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2024 | Book

Smart & Sustainable Infrastructure: Building a Greener Tomorrow

Proceedings of the 1st Interdisciplinary Symposium on Smart & Sustainable Infrastructure (ISSSI 2023)

Editors: Nemkumar Banthia, Salman Soleimani-Dashtaki, Sidney Mindess

Publisher: Springer Nature Switzerland

Book Series : RILEM Bookseries


About this book

This book gathers peer-reviewed contributions presented at the 1st Interdisciplinary Symposium on Smart & Sustainable Infrastructure (ISSSI), held in Vancouver, BC, Canada, on September 4–8, 2023, and affiliated with the 77th RILEM Annual Week 2023. Aiming at creating an environment of mutual cooperation between experts in materials and structures, it covers topics such as sensors, IoT, and structural health monitoring, AI and machine learning, data analytics for infrastructure management, nanotechnology, additive manufacturing, smart and bioinspired materials, durability of materials and structures, resilience to earthquakes, floods, fire and blast, carbon reduction in construction and operations, and sustainable ultra-high performance materials. The contributions, which were selected through a rigorous international peer-review process, share exciting ideas that will spur novel research directions and foster new multidisciplinary collaborations.

Table of Contents


Advanced Materials in Construction Innovations and Applications

Optimizing Performance-Engineered Concrete Mixtures Using Linear Programming

This paper uses linear programming to optimize concrete mixture proportions while meeting target performance criteria that serve as constraints. The objective function, which is a weighted function of the material and carbon costs, is used to find the optimal mixture design based on the criteria that are most important to the user. The parameters in the objective function (e.g., material cost, carbon cost, construction cost, etc.) are user-adjustable. The constraints are the required mechanical properties (e.g., compressive strength, elastic modulus, etc.) and durability performance indicators of concrete such as formation factor, calcium hydroxide content, time-to-critical saturation, electrical resistivity and pH of concrete pore solution. A thermodynamics-based modeling framework is used to predict the mechanical and durability performance of concrete. A feasible region of mixture proportions is obtained after predicting concrete performance across a range of volumes of water and supplementary cementitious material in concrete where the target performance is met. The optimal mixture proportions (i.e., least cost, minimum carbon emissions, or a weighted combination of the two) can be obtained using the concepts of linear programming used in this framework. This powerful approach can be used to efficiently utilize resources and optimally design concrete mixtures.

Keshav Bharadwaj, O. Burkan Isgor, W. Jason Weiss
Investigating the Self-sealing of a Healing Agent via a Korean Permeability Test and a Migration Test

Cracks in reinforced concrete are a fast entry point for aggressive substances possibly leading to reinforcement corrosion and concrete deterioration, which leads to a decreased service life and a need for repair. This paper investigates self-healing concrete, which is able to heal the formed cracks. An organic/inorganic hybrid admixture was used in a mortar mix as a healing agent and compared to a reference mortar: The sealing efficiency of the mixture with and without healing agent was compared through a Korean water permeability test on cylindrical specimen. The specimens were cracked in an indirect tensile strength test after which the two halves were tied back together with silicone spacers in order to have a crack width of 300 µm. The results showed that the organic/inorganic hybrid admixture obtained a better sealing efficiency in comparison to the reference mortar. Additionally, a chloride migration test was performed on a different set of reference specimens and specimens with the organic/inorganic hybrid admixture. After 0 and 28 days of healing, the specimens with the hybrid admixture had a significantly lower migration coefficient.

Laurena De Brabandere, Tim Van Mullem, Lee Junghwan, Jung-Il Suh, Kwang-Myong Lee, Nele De Belie
Study of Hydration of Belite-Based Cement with High Gypsum Content

Belite-based binders offer major advantages over Ordinary Portland Cement with high Alite content in terms of durability, low heat evolution, and low carbon footprint during production. To gain these advantages, activation of the most active polymorphs of Belite by the addition of mineralizers and rapid cooling is needed. However, the reaction rates and hydration products of pure Belite paste are still not well understood. This is due to factors such as i) the effect of mineralizers incorporated in Belite crystals on hydration; ii) the role of residual mineralizers left outside of Belite; iii) the effect of sulfate’s addition on Belite hydration. In this study, a clinker with a high content of α-Belite was prepared. The variable parameter was the amount of Gypsum added during the stage of cement preparation, which ranged from 0 to 30%. The results of the study confirmed that the reactivity of cement based on Belite is highly dependent on the content of sulfates. As sulfate content increases, the degree of hydration increases at an early age but decreases at later ages. It has also been found that Gypsum reacts during the Belite hydration and forms atypical new hydration products such as aluminate-free Ettringite and Apatite. The results of this research reveal a high potential for a new type of low-carbon binder system based on α-Belite with high Gypsum content.

Antonina Goncharov, Semion Zhutovsky
Mechanical Performance of 100% Recycled Aggregate Based Geopolymer Concrete at Various Concentrations of NaOH

India is among the developing countries grappling with environmental pollution. To address the environmental pollution that results from the production of OPC and the increasing waste material, there are various methods available, including geopolymer concrete (GPC) that incorporates recycled concrete aggregate (RCA). To maintain consistency, a constant alkali activator content (AAC) to binder ratio is employed. The compressive strength (CS) and indirect tensile strength (ST) of the GPC with recycled aggregate are evaluated at 3, 7, 14, 28, and 56 days. The findings indicate that the CS and ST of the GPC with recycled aggregate are lower than those of natural aggregate-based GPC. Nonetheless, there is a positive correlation between CS and ST in GPC containing recycled aggregate. Furthermore, the mechanical performance of the recycled aggregate based GPC increases up to 16M NaOH concentration and decreases beyond that.

Banoth Gopalakrishna, Pasla Dinakar
Thermoplastic Impregnated Textile Reinfrocement for the Industrial Realisation of Complex Shaped Concrete Elements

Resource-efficient design and lightweight construction represent a central approach to sustainable development and production in the construction industry. For more than two decades, textile-reinforced concrete (TRC) has been researched as a material-efficient solution for the production of high-strength and thin-walled components, transferring lightweight potential to the construction industry. However, the increase in mechanical performance due to impregnation of the textile reinforcement is often at the expense of shape flexibility and design freedom. Therefore, application mostly focuses on two-dimensional slabs. For more complex elements such as T-beams and aesthetic features, e.g. shell systems, three dimensional reinforcement cages are needed. The use of thermoplastic impregnation materials facilitates the flexible realisation of reinforcement geometries due to their thermal deformation behaviour. Within this study, the mechanical behaviour of the thermoplastic impregnated reinforcement on textile and composite level are analysed. It is shown that tensile strength of the reinforcements up to 1300 MPa, which is well in range of the commonly applied impregnation materials. In addition it is shown, that the shaping process under elevated temperature is no cause for decrease of the mechanical performance of the textile reinforcement. In conclusion, it is shown that the application of thermoplastic impregnation shows potential for the realisation of application- and product-specific geometries of reinforcement cages without sacrificing mechanical performance.

Kira Heins, Thomas Gries
Optimizing Digital 3D Printing of Concrete Structures

Digital 3D printing seems to be a novel way of constructing concrete and reinforced concrete structures. This paper is concerned with printing concrete structures by 3D extrusion. It describes an optimization procedure that changes the sequence in which the individual wall segments are printed, thereby it reduces the time to print the whole structure. The paper also provides a procedure how to estimate time-dependent material parameters for the concrete used for printing. It is based on material laboratory measurements added by use of several empirical formulas.The developed optimisation procedure was successfully applied for analysis of the experimental Technische Universität in Dresden, (TUD), house. Solution of a more complex structure is presented for the case of the Prvok house built in Prague, Czechia.

Libor Jendele, Jiří Rymeš, Jan Červenka
Evaluation of Tensile Behaviour of 3D Printed Concrete Assemblies with Reinforcement

Inclusion of reinforcement to improve the tensile capacity of 3D printed concrete specimens has been gaining significance in recent times. Different types and procedures for introducing steel reinforcement in printing are currently under development. The present study involves understanding the influence of two different types of reinforcement on the tensile behaviour of 3D printed concrete. The different reinforcements considered were steel mesh and a 3 mm bar. The reinforcement was placed between printed layers in a beam-type assembly. The influence of the reinforcement in providing tensile stresses across a crack propagating across printed interfaces is evaluated from a fracture beam test. The crack bridging provided by the reinforcement is evaluated from the measured surface crack profiles obtained from fracture test. Mesh reinforcement showed a better bond behaviour when compared to the 3 mm bars. The factors which contribute to the tensile performance of reinforcement across a tensile crack are identified.

Omkar Kulkarni, Manideep Singh Thakur, Tippabhotla A. Kamakshi, Spandana Paritala, Kolluru V. L. Subramaniam
Characteristics of High Calcium Fly Ash Geopolymer Mortar

Portland cement is one of the principal sources of anthropomorphic CO2 emissions. It is estimated that cement production contributes up to 10% of greenhouse gas emissions and annual cement production over 4 billion tons. This has led to the development of a range of alkali activated materials (AAM), the most common precursor materials being class F fly ash and blast furnace slag. At present Class C Fly Ash is not widely utilized as an AAM due to the chemical composition and activation requirements. However, initial research on high Calcium German Class C Fly Ash suggests that the material may have potential for application as an AAM. This paper reports the development of ambient cured alkali activated mortar optimised by varying the alkali modulus and w/b ratio. The evolution of the mechanical and microstructural properties is reported over the initial 28 day period. Compressive strength in excess of 10 MPa at 7 days and 15 MPa at 28 days was achieved at ambient temperature. Similar strengths were observed for both 10% and 15% dosage but as dosage increases the optimal Alkali Modulus reduces.

David W. Law, Patrick Sturm, Gregor J. G. Gluth, Chamila Gunasekara, Morteza Tahmasebi Yamchelou
Synthesis of Magnetic Calcium Silicate Hydrate (M-C-S-H) and Its Adsorption Behaviors of Heavy Metal Ions in Wastewater

A novel inorganic nanocomposite with excellent robustness, magnetic calcium silicate hydrate (M-C-S-H), is synthesized at extremely low cost yet presents rapid adsorption rate and superhigh adsorption capacity. Cu(II), Cd(II), Co(II) and Cr(III) can be completely removed at low M-C-S-H dosage. The adsorption processes are spontaneous, following the Langmuir adsorption isotherm model. It was found that about 72% of Cu(II), 82% of Cd(II), 84% of Co(II) and 94.5% of Cr(III) were removed by exchanging with the interlayer Ca(II) in M-C-S-H, and the rest was removed through other mechanisms including chemical microprecipitation and surface complexation adsorption facilitated by electrostatic attraction. M-C-S-H maintained well both its structure and morphology during the adsorption process. Meanwhile, good regeneration performance was also observed that the adsorption capacity of nearly 53–72% can be retained after four cycles of Cu(II) treatment. Furthermore, massive wastewater treatment was successfully carried out through a specially designed platform. All these results demonstrate that M-C-S-H is an efficient and robust adsorbent for heavy metal ions which has great application potential in aqueous systems.

Qi Liu, Pan Feng, Lijing Shao, Chen Chen
Evaluation of Concrete-Steel Friction for Automated Tunnel Segment Extrusion

Italy is a country, that due to its tomography, has one of the highest number of tunnels in its roadway network. Due to the limited technology available at the time of construction and the years elapsed since then, maintenance interventions are needed in order to avoid their collapse. An academia-industry collaboration between Politecnico di Milano and the start-up company Hinfra is active in this field, validating a new technology for the refurbishment of existing tunnels through extrusion of a Steel Fibre Reinforced Concrete (SFRC) lining against the existing old one. This new technology is asking for tailored material and process performance requirements, in order to boost the productivity through the use of a dedicated mechanical extrusion system. In designing the latter, it is fundamental to correctly assess the extrusion resistance due to the friction of concrete against the surface of the moving steel mould. This is of fundamental importance as the mechanical engine has to be designed in order to be capable to slip the extruded SFRC layers during the slip-forming process. The goal of this paper is to present an experimental campaign aimed at evaluating the aforesaid property for an extrudable concrete mix at early ages and speeds both calibrated on the basis of the full-scale extrusion equipment and target productivity rate (between 1 and 3 m per hour). The influence of mix design variables including water binder ratio and retarder admixture dosage have been investigated through a factorial design methodology.

Andrea Marcucci, Arslan Javed, Stefano Guanziroli, Liberato Ferrara
A Long-Term Influence of Sewage Sludge Ash as an Additive on Shearing Capacity in Collapsible Soil

The growing concerns about the negative environmental impact of sewage sludge and its disposal have drawn attention. However, the volume of sewage sludge is increasing significantly. Therefore, it is important to establish an effective cycle for the application and utilization of this material in order to mitigate its bio-environmental risks. Given the extensive presence of collapsible soil, the rapid urbanization, and the expansion of large cities on such soil, it is crucial to investigate the stability and improvement of this type of soil. This research project aims to evaluate the long-term effects of sewage sludge ash on the shear strength of collapsible soil. The use of sewage sludge ash as an additive is being considered. Through initial assessments, the shear strength of the soil under investigation is determined both without the additive and with varying weight percentages of 2%, 4% and 6%. The tests are conducted on samples remoulded over a period of 30 days. The final results indicate that increasing the percentage of sewage sludge ash as an additive enhances soil cohesion while reducing the internal friction angle ɸ. Furthermore, a comparison is made between samples remoulded 3 days and 30 days, revealing a similar behavior in terms of shearing capacity for both time durations.

Amir Mosallaei, András Mahler
The Role of Reinforced Interface Adhesive Layer to Construct Resilient Pavement

Resilience in general captures the goals of maintaining the continuity of performance and recovery to the desired function during an infrastructure designated service life. Nevertheless, pavement infrastructure is particularly vulnerable to the impacts of climate change due to being continuously exposed to outdoor conditions. Constructing a pavement that is resilient to a changing climate will necessitate challenging changes in materials, design, and execution techniques. Accordingly and irrespective of crucial parameters such as pavement structural and mix designs, interlayer bonding between pavement layers plays a crucial role in pavement durability. For instance, slippage of pavement layers occurs particularly during summer under heavy traffic loads. However, such distress has been exacerbated due to global warming which might be moderated using a proper adhesive layer. This study initially compared the shear resistance between pavement layers when conventional and polymer-modified bitumen (PMB) emulsions were applied as adhesive agents. Furthermore, the impacts of milk lime (slurry) and glass-fiber-reinforced adhesive layer were evaluated using the Leutner shear test. The results showed that incorporating PMB emulsion considerably enhanced bonding between layers and outperformed conventional materials. Although no considerable influence of slurry on shear resistance was found, less tack coat removal by paver during road execution was detected due to the presence of the slurry. The reinforced adhesive layer with glass fiber exhibited higher shear resistance, particularly for the specimens that were collected after being approximately one year in service. It was finally observed that a few parameters such as trapped moisture can destructively influence interface shear resistance.

Seyed Reza Omranian, Cedric Vuye, Johan Braspenninckx, Wim Van den bergh
Final Disposal of Molecular Sieves in Cement Mortars

An industrial waste survey was performed in the city of Bahía Blanca (Argentina) to analyse the possibility of disposal in a cement matrix. A molecular sieve (MS), from a gas transportation company was found and studied. This granular material is used in absorption towers to filter the hydrocarbons contained in the gas and it is disposed in a safe landfill at the end of its useful life. The objective of the current paper is mainly focused on the feasibility of recycling milled molecular sieves on cement mortars with its incorporation and comparing them with a standard sample (without waste). For MS, bulk density, specific gravity, water absorption, particle size distribution, and X-ray diffraction were tested. Mixes were made by incorporating 0%, 15%, and 25% of milled molecular sieves by weight of cement, to evaluate hydration process at different ages by calorimetry, puzzolanic effect by Frattini test and measure mechanical properties in mortars employing standardized tests. In addition, a leachate analysis of curing water was conducted after 90 days for contaminants. The incorporation of milled molecular sieves in cement mortars produces changes in the properties of the mixture at early ages but the reduction of compressive strength decreases over time. It is concluded that this is a potential alternative to the final disposal of these wastes without harming the environment and has a possible pozzolanic effect on the mixtures.

Rocío Peralta Ring, Carla Priano, Viviana Rahhal
Predicting the Alkali Contribution of SCMs to Concrete Pore Solution

Supplementary cementitious materials (SCMs) are often used in concrete to reduce the risk of alkali-silica reaction (ASR). This is primarily through dilution of the alkalis contributed by Portland cement and binding of alkalis as a result of pozzolanic reaction. Some SCMs, however, contain a high level of total alkalis, and these may be soluble, leading to increased pore solution pH and reduced efficiency in mitigating ASR. This may be especially problematic for many non-conventional and rapidly growing SCMs, such as volcanic ashes, marginal coal ashes, and ground glass, having total Na2Oeq > 3.0%wt. This paper presents a new soluble alkali test to quantify the soluble fraction of alkalis in SCMs. The test was applied to 14 SCMs, including coal ashes, volcanic ashes, calcined clays, and ground glass, and their alkali release was monitored for 90 days. The results are compared with ASTM C311’s “available alkali test.” Additionally, the pore solution of cement pastes made using 11 of these SCMs were extracted and analyzed over 90 days. The findings indicate that a considerable fraction of the total alkalis in SCMs is soluble in concrete’s pore solution. However, the pozzolanic reaction can bind most of the dissolved alkalis, resulting in a net alkali sink/reduction for the majority of the tested SCMs. A regression analysis of the results revealed that the pore solution [OH−] reduction by an SCM can be estimated based on the SCM’s pozzolanic reactivity, soluble alkali content, and Ca/(Si + Al).

Farshad Rajabipour, Mohammadreza Sharbaf
An Investigation into the Effect of Pre-treated Milkweed Fibers on Hydration of Portland Cement

Pre-treated milkweed fibers have been shown to have excellent hygroscopic properties, making them suitable for superabsorbent applications. These hollow fibers can be particularly used as a sustainable substitute for non-renewable superabsorbent polymers and act as an internal curing agent in cement paste mixes with low water-to-cement ratios. This study investigates the effect of pre-treated milkweed fibers on the hydration of Portland cement paste for internal curing agent application. Milkweed fibers were pre-treated by hydrothermal treatment and hybrid treatment, which combine the hydrothermal treatment and alkaline treatment. The impact of different pre-treated milkweed fibers on the hydration reaction of cement paste was investigated using thermogravimetry analysis (TGA/DTG), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). It was observed that different pre-treatment methods resulted in MW fibres with different chemical compositions. While hydrothermal treatment removed waxes and pectin from MW fibres, hybrid treatment removed lignin and hemicellulose. According to the result of the study, the incorporation of hybrid treated MW fibers to cement paste samples improved cement hydration by forming more chemical bond water, which promotes the hydration of C3S and C2S and increases the production of CH and crystallized calcite. Contrarily, non-treated MW fibres and hydrothermally treated MW fibres performed less effectively as an internal curing agent than the hybrid treated fibre, primarily due to presence of lignin and hemicellulose and their retarding effect on the cement hydration reaction.

Amirmohammad Sabziparvar, Donato Taleponga, M. Reza Foruzanmehr
Mitigating Autogenous Shrinkage by Using Recycled Superabsorbent Polymers

Cracks may appear in cementitious materials with a low water-to-binder ratio. These early age cracks during the autogenous deformation have an impact on the durability of structures. Superabsorbent polymers used as internal curing materials may mitigate autogenous shrinkage, and thus may improve durability. In the interests of the circular economy, recycled superabsorbent polymers can be added to building materials, instead of commercially available superabsorbent polymers. In this paper, the influence of the addition of recycled SAPs from the diaper industry on autogenous shrinkage as well as on compressive and flexural strength, and free shrinkage was evaluated. The aim is to verify whether the improvement of the autogenous deformation is not at the expense of the mechanical properties of the cementitious material. Various tests were performed to assess the mechanical properties and shrinkage behaviour of specimens containing recycled superabsorbent polymers compared to reference preparations and specimens with commercially available superabsorbent polymers. The addition of recycled SAPs has a limited influence on the material’s properties compared to the addition of commercial SAPs. By partly mitigating autogenous shrinkage, recycled admixtures postpone the early-age cracking and seem to be a solution to improve cementitious materials durability and sustainability. The same behaviour was observed with regard to the free shrinkage tests.

Didier Snoeck
Printability and Shape Stability of Cement Mortar Incorporating Low Volume of Micro-Polypropylene Fiber for 3D Printing Application

This study investigated the printability and shape stability of cement mortar with micro-polypropylene fiber for 3D printing application. Mortar mixes with fiber content from 0% to 0.1% were tested for properties relevant to printable cement mortar, including initial printable time, flow, and viscosity. The results showed that fiber addition decreased flow percentage, and initial printable time but increased viscosity (in terms of shear stress). The fiber addition also impacted the filament cross-sectional shape, making the width narrower and the height taller. The relationship between the initial printable time and viscosity test indicated that the shear stresses between 494 to 580 Pa are suitable to start the printing these mortars.

Piti Sukontasukkul, Sila Khomkum, Buchit Maho, Kazunori Fujikake
Influence of Cold Joint on Fracture Behaviour of 3D Printed Concrete

Extrusion-based layer deposition is the most popular form of 3D Concrete Printing (3DCP). The inter-layer bonding is an important parameter in the case of extrusion-based layer deposition in 3DCP, which affects the homogeneity of the element and thus its mechanical behaviour. The bond between the layers depends upon several factors including the fluidity of the mixture and the print time gap between layers. Weak interfaces develop in the form of cold joints between two adjacent layers of concrete when they are placed with a time gap. The study involves the understanding of influence of time gap between the vertical layers on the fracture behaviour of the printed beams. Crack propagation in the layered beam is evaluated using digital image correlation. The influence of wait time on the crack planes across the printed interfaces are studied. The reduction in the bond between layers with waiting time is related to fracture behaviour of the printed beam.

Manideep Singh Thakur, Omkar Kulkarni, Tippabhotla A. Kamakshi, Spandana Paritala, Kolluru V. L. Subramaniam
Self-Sensing Performance of Cementitious Composites with Carbon and Recycled Carbon Fibres

This paper investigates the electrical-mechanical performance of cement-based mortar and concrete mixes incorporating carbon and recycled carbon fibres. Mortar mixes were produced with varying fibre content from 0.1% to 0.5% by volume for both types of fibres, while sand/cement and water/cement ratios were kept constant to achieve a similar composition in terms of mortar matrix. Concrete mixes were also produced incorporating 0.5% vol. of fibres and varying the ratio of coarse/fine aggregates from 1 to 2. Electrical measurements and mechanical characterisation tests were performed at 28 days while cyclic compression tests with concurrent measurements of electrical resistance were carried out to assess the piezoresistive response. The percolation threshold in both virgin and recycled carbon fibres was found to be approximately 0.1% vol. in mortar mixes, with mortars reinforced with recycled fibres showing higher sensitivity. The addition of higher amounts of coarse aggregates fibres led to a non-homogenous distribution of fibres within the mortar matrix and limited the piezoresistive response of the composite. The results highlight the potential of recycled carbon fibres in substituting expensive inclusions in smart applications, without compromising electrical and piezoresistive performance.

Niki Trochoutsou, Danny Smyl, Giacomo Torelli
Self-Sealing Performance of Healing Agents via a Low and High Pressure Water Permeability Test with Active Crack Width Control

With the continued rise of the world population, it is important to focus on the sustainability of our building materials. Traditional reinforced concrete is prone to cracking and these cracks have a detrimental effect on the durability, thereby limiting the service life. Repair of the damage is often costly and if not done timely the structure needs to be replaced. Self-healing concrete has the capacity to repair its own cracks. The current study investigates two self-healing agents: an organic/inorganic hybrid admixture and bacterial pellets. The self-sealing performance of the two healing agents were compared with a reference mortar using a permeability setup, after cracking the specimens with an active crack width control technique. The performance of the organic/inorganic hybrid admixture was best after healing the mortar specimens for a month in submerged conditions. Nevertheless, all other series also had a significant sealing efficiency. In order to differentiate the results better and in order to test the stability of the healing products deposited in the crack at higher pressures, the specimens were also subjected to a high-pressure permeability test. Again the organic/inorganic hybrid admixture came best out of the comparison.

Tim Van Mullem, Laurena De Brabandere, Jung Hwan Lee, Kwang-Myong Lee, Nele De Belie
Optimizing the Effects of Mineral Admixtures and Curing Regimes on Sustainable Non-proprietary UHPC

The proprietary ultra-high-performance concretes (UHPCs) are well-known for outstanding mechanical properties and durability. Despite the potential of the proprietary UHPC, factors including high cost, more complicated manufacturing than conventional concrete, and CO2 emission due to the large cement dosage hinder the prevalent application of the proprietary UHPC. This research aims to provide an economic, duplicatable, and ecofriendly non-proprietary UHPC with an energy saving curing regime. The effects of three mineral admixtures including silica fume, fly ash, and ground granulated blast-furnace slag (GGBS), combined with three curing regimes are studied. The 28- and 56-day compressive strengths are compared to select the combination of mineral admixture and curing regime which gives the highest strength-to-cost ratio. The experiment results demonstrated that a non-proprietary UHPC with commercially available components within Japan through conventional equipment. Experiment results showed that: (1) GGBS non-proprietary UHPC cured at ambient produces the highest strength-to-cost ratio; (2) silica fume is the most sensitive to the elongation of thermal curing; (3) thermal curing is not essential in boosting the compressive strength of non-proprietary UHPC.

Ye Zhang, Yuko Ogawa, Riya Catherine Geogre, Kenji Kawai
The Effect of U-Type Expanding Agent for Concrete (UEA) on the Microstructural and Mechanical Properties of Mortar Fabricated Through Alternate 3D Printing

In this paper, we proposed an alternative 3D printing process for construction materials based on the idea of upgrading from “black and white printing” (printing from one material) to “color printing” (printing from multiple alternative materials). The plan was to reduce the amount of energy-intensive and polluting construction materials (e.g., cement) and use a combination of industrial solid waste and cement to build structures that meet safe service requirements. Two different alternative materials of alkali-activated slag and conventional cement were used, and it was found that column-by-column printing was beneficial to refine the interface, resulting in better flexural strength. After establishing the feasibility of the alternative printing, the architectural alternative 3D printing device was designed and fabricated, and the effect of u-type expanding agent for concrete (UEA) on the performance of the alternatively printed products was evaluated. It was found that 2% by mass of UEA would create an interlocking structure, which was beneficial for strength enhancement. The study contributed to the advancement of alternative 3D printing technology.

Xiaoshuang Liu, Yuxiao Zou, Yingxuan Wu, Dong Cui, Xiaobao Zuo

Emerging Trends in Sustainable Construction Materials and Practices

Effects of Pretreatment Methods and Physical Properties of Cellulose Fibers on Compatibility of Fiber-Cement Composites: A Review

One of the most serious environmental issues of our day is climate change, which is being caused by the massive quantities of non-renewable resources that are being depleted as a consequence of construction activities. The extensive use of ecologically friendly construction materials is thus essential. In this scenario, the development of biobased cellulose fibers for reinforcement of cement composites may open the door to effectively substituting these environmentally sustainable, biodegradable, and biocompatible fibers with conventional, non- renewable fibers. However, there are concerns regarding cellulose fiber’s compatibility with the cement matrix, which inhibits the use of these efficient and sustainable materials. The present article entails the existing research gaps in the field of challenges inhibiting the use of cellulose fibers for reinforcing cement composites owing to fiber-cement compatibility, as well as feasible solutions to cover those gaps. This study discusses techniques for improving the bonding adhesion of cellulose fiber-cement matrix, with a focus on physical properties of cellulose fibers and effectiveness of different pre-treatment methods. The article provides in-depth information on the influence of cellulose fiber surface scales, ranging from macro to nano, on the fiber- cement bonding adhesion level. The article further discusses the use of different pre-treatment methods, including physical, chemical and Enzymatic pretreatment of cellulose fibers as a means of enhancing the compatibility of fiber-cement matrices.

Sanaz Ajabshir, Rishi Gupta
Recycled Concrete Aggregates – State of Play in South Africa and Collaborative Programme with IITM

Population growth coupled with rapid urbanisation have produced a continued increase in construction and related demolition activities for projects such as housing developments, commercial buildings, and public infrastructure, especially in developing countries in the Global South. The deposition of construction and demolition waste (CDW) into landfills depletes land resources, potentially poses environmental hazards and results in disposal of potentially useful resources that can be used to produce concrete according to circular economy principles. Joint research activities at the Universities of Cape Town and the Witwatersrand in South Africa and IIT Madras in India have resulted in the development of a monograph on recycled concrete aggregates and their influence on concrete properties. The monograph and associated online teaching material, published in 2023, aim at informing industry and academia about current challenges and opportunities in the fields of CDW generation and management and concrete manufacture with recycled concrete aggregate (RCA). The background to the monograph is presented together with an overview on the generation of RCA and recent results on the durability of RCA concrete.

Mark Alexander, Hans Beushausen, Ichebadu Amadi, Manu Santhanam
Improvement of Recycled Cement Powder Characteristics from C&D Wastes by Accelerated CO2 Curing and/or Heat Treatment

Huge quantities of construction and demolition waste are produced each year, and about a third of this is concrete. With growing interest in circular economy, there is a need to examine how this can be applied to end-of-life concrete. While there is a potential market for recycled coarse aggregate, the reuse of fine aggregate and recycled concrete powder is more limited. However, recycled concrete powder constitutes up to 10% of the mass of crushed end-of-life concrete, and comprises almost 80% hardened cement paste. This calcium- and silicon-rich paste is ripe for reactivation. This study has examined the latent hydraulic behaviour of recycled concrete powder and investigated how various treatment methods can produce an effective supplementary cementitious material. Heat treatment and carbonation, either in isolation or combined has been used to produce materials with activity indices approaching unity at 20% replacement. The performance of these materials has been understood via detailed characterization by thermal analysis, XRD and FTIR. It has proven possible to produce effective supplementary cementitious materials from waste recycled concrete powder, thus finding a use for this end-of-life material and potentially reducing cement’s carbon footprint.

Ali Al-Janabi, Leon Black, Samuel Adu-Amankwah
Hydration and Strength Development in Limestone Calcined Clay Cements with Low-Grade Limestone

Limestone calcined clay cement (LC3) is a sustainable alternative to ordinary Portland cement. It helps to achieve a clinker factor as low as 0.5. Cement-grade limestone with a CaCO3 content above 75% is usually used to manufacture LC3 cement. Sometimes limestone contains impurities like silica, clay, dolomite, etc., beyond the specified limits recommended for cement manufacture. This limestone is commonly known as low-grade limestone. This paper discusses the results of a study on the feasibility of utilising low-grade limestone in LC3 cement. Isothermal calorimetry was done to understand the hydration kinetics of the cementitious systems. Compressive strength measurements on mortar cubes were done to understand how strength is affected due to the presence of impurity in limestone. Results indicate that LC3 systems with low-grade limestone give either comparable strength or higher strength in compression, compared to the control specimens of ordinary Portland cement. Calorimetry results also showed an acceleration in early hydration for the blends with low-grade limestone. In short, low-grade limestone is a promising alternative to pure limestone in LC3 systems.

B. Asha, Manu Santhanam
Transition Towards Low Carbon Concrete – Persuading Parameters

The transition of the concrete industry towards a low-carbon pathway not only requires optimized mix designs with lower clinker/cement content but also other interventions that could reduce the carbon footprint of concrete in its value chain. Current codes specify minimum cement contents for concrete mixes intended to preserve durability in various exposure classes, but the cement type is usually not specified. Codes also specify an increase in the amount of reinforcing steel required for reinforced concrete members with a matrix strength above 50 MPa, partially counteracting the potential carbon benefits of reducing the amount of concrete used for a given element employing high-strength concrete. This places two “hard” constraints on reinforced concrete design for minimum carbon per unit of structural performance. With these two practical constraints in place, in this paper, the influence of several materials and design parameters are discussed and assessed for the carbon reduction potential of concrete systems. The parameters considered are i) lowering the clinker content in concrete mixes whilst complying with the code-specified minimum cement content for required durability ii) producing better quality concrete e.g., by minimising the margin between target mean strength and required characteristic compressive strength and iii) reducing partial factors of safety for concrete at the design stage while assuming the minimum load requirements. It was quantified that there is a significant potential reduction in the carbon footprint of the concrete and the reinforced concrete element, when these parameters are varied from what is specified in the code.

Anusha S. Basavaraj, Hisham Hafez, Adam Bell, Michal Drewniok, Phil Purnell
A Case Study on Structural Steel Reuse: From Source Material to New Construction

Canada’s most prominent parliament building, Centre Block, is currently undergoing an extensive rehabilitation. As part of this rehabilitation, some original 1916 structural steel requires removal, and several new structural components are being introduced. Like many existing buildings undergoing modifications, the removed materials could be recovered as a resource for future works instead of being recycled or becoming waste, enabling a circular economy approach. Several challenges were identified for the successful implementation of this reuse of steel, including modifying salvaging procedures, developing proper inspection processes, providing an inventory framework, and optimizing the reintegration of the members into the new design.This paper outlines the methods used by the project team to overcome these challenges and adopt a circular economy approach for the structural steel, facilitating the reuse of the removed structural members in Centre Block’s rehabilitation. This case study documents the procedure from deconstruction to new design, including the development of a computational design tool which identifies each unique salvaged member and finds a location for its reuse. The automation of this portion of the process reduces time spent identifying potential beam reuse locations, improves design efficiency, and enables a rapid response to evolving design constraints.Current projections of the implementation of this circular economy approach indicates an embodied carbon savings of 625 tCO2e for 1700 reused beams, with the potential for a broader impact as additional members are retained for reuse on other projects. Furthermore, the establishment of this methodology can facilitate this process for a larger inventory across multiple concurrent projects.

Isis E. Bennet, Kiarash Ara, Carl Mohammadi, Paul Steneker
Paving Zero Emissions?

Paving zero emissions refers to the goal of achieving a pavement construction or maintenance process that does not release any harmful emissions into the environment. This objective aligns with the broader efforts to mitigate climate change and reduce greenhouse gas emissions.The implementation plan for achieving zero emissions, in the pavement industry, as mandated by the European Green Deal, encounters significant challenges. A thorough literature review reveals a lack of standardized measurement methods for, the volatile organic compound (VOC), emissions in the asphalt industry. This absence of clear protocols, procedures, and tools poses obstacles to accurately measuring and monitoring emissions. Essential research, as presented in this work, is required to establish thresholds, limit values, and reliable measurement methods that will pave the way for achieving zero emissions. Furthermore, practical on-site measurement techniques need to be developed to complement laboratory-based tests. By investing in research initiatives, promoting collaboration between stakeholders, and supporting the development of pragmatic solutions, meaningful progress can be made toward achieving zero emissions in the pavement industry. Alignment with the objectives of the European Green Deal necessitates addressing these gaps.

Johan Blom
Enhancement of Early Age Strength of Activated Steel By-Products

All factories produce by-products and waste that are needed to be recycled or reused in other industries to keep the environment sustainable for future generations. Also, one of the human efforts to reduce the built emission environment is the use of types of cement whose production produces less carbon dioxide such as by-products activated with alkali to move toward low carbon cement and net zero concrete. As a by-product of steel factories, different types of slags are worthy to be studied to be used in low-carbon cement production. However, different studies have shown the low early-age strength of these materials.In this study, ground granulated blast furnace slag (GGBS) was replaced with different slag as by-products of one steel factory and activated with different [OH−]/M activator systems to study which works better to enhance early-age strength in different types of slags. The effect of further treatment on different slag such as calcination was considered as well. Flow tests, compressive strength tests, and flexural strength tests were conducted to evaluate the fresh and hardened properties of the final products mortar. This paper shows that the addition of mineral additives brings a positive effect by enhancing the early age strength in the cases where main mineral is lacking in the precursors’ composition.

Dali Bondar, Bruno Campos, Elizabeth Gilligan
CO2 Capture of Concrete Waste Fines Through Wet Carbonation Under Seawater

The growing concern over the increase in atmospheric CO2 concentrations has led to the development of innovative methods for its storage and utilization. One promising approach is to store CO2 in seawater, which can dissolve and store large amounts of CO2. Recent technological advances have facilitated the rapid storage of CO2 in concrete waste through wet carbonation. Therefore, combining these two approaches has been proposed to achieve effective CO2 storage while also addressing the issue of concrete waste. In this study, we investigate the feasibility of wet carbonation of concrete waste fines under seawater, compared to pure water, for CO2 capture. The experimental results indicated that seawater eluted a considerable amount of calcium and other elements from concrete waste, which were approximately 2–3 times higher than those in deionized water. However, the concentration of Si dissolved from cement paste carbonated in seawater was found to be lower than that in deionized water. Furthermore, the phase assemblage evolution in cement paste during wet carbonation in seawater exhibits a similar trend to that in deionized water but with a faster rate of hydrated phase decomposition. Wet carbonation of concrete waste in seawater exposure results in the emergence of new phases in concrete, including Friedel's salt and halite. The rapid decomposition during wet carbonation in seawater increases the amorphous phase in cement paste, even though the decomposition of C-S-H is completed. Moreover, wet carbonation in seawater was observed to sequester a larger amount of CO2 in both the concrete waste and solution compared to deionized water. These findings provide valuable insights into the potential of seawater for carbon capture and utilization and contribute to the development of efficient and effective CO2 capture technologies.

Ngoc Kien Bui, Ryo Kurihara, Takafumi Noguchi, Ippei Maruyama
Environmental and Mechanical Investigation of Sustainable Lightweight Aggregate Concrete

Reducing the density of concrete has received remarkable attention as the loads carried by structural elements are significantly contributed to the weight of concrete. This has led to an increasing request for structural lightweight aggregate concrete (LWAC) due to its numerous pros including lower density and better thermal and acoustic performance, etc. In this regard, a range of lightweight materials including lightweight expanded clay aggregate (LECA) have emerged as a contender for reducing the density of the concrete. In addition, today’s concrete is expected to satisfy stricter eco-efficiency and sustainability demands, causing a need for alternative binder material to replace (in part or in full) the high carbon dioxide (CO2)-generating traditional ordinary Portland cement (OPC). The use of silica fume (SF) as partial substitution of OPC is a promising solution to mitigate the negative effects of OPC production. Therefore, this work aims to analyze the influence of material parameters on the mechanical and environmental behavior of LWAC. To achieve this objective, a total of 30 LWAC mixture designs varying OPC content, LECA percentage replaced with natural aggregates, SF partial replacement by weight of OPC, and varied water-to-cement (w/c) ratios as the test variables were examined. A sensitivity analysis, a simulation tool used to understand the impact of changes to input parameters on the outcome, was used to determine the effect of diverse variables on the compressive strength and CO2 emission of LWAC mixture.

Farshad Dabbaghi, Ibrahim G. Ogunsanya
Microstructural Analysis of Ternary Hybrid Alkaline Binders Containing Slag, Fly Ash and Portland Cement

Although the use of supplementary cementitious materials (SCMs) is a well-known practice with over a century of experience, the mechanism of reaction of SCMs remains not fully understood, and further research is necessary. In addition, the incorporation of alkaline activators into cementitious systems with a low content of Portland cement (PC) is gaining popularity because it resolves issues such as long setting times and slow strength development. These challenges are typically identified when high volumes of SCMs are used.Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) analysis can provide insights into the phase assemblage of ternary hybrid alkaline binders. Information concerning the microstructure, as well as the presence of different gels identified as the main binding products in the systems are key for understanding the complex formation of secondary hydration products. In many cases, such secondary hydration products influence the durability of the cementitious matrix when exposed to the environment.This study evaluates ternary cements containing ground granulated blast furnace slag (GGBFS), a low-calcium fly ash (FA), PC, and sodium sulfate as an activator. The chemistry and morphology of remnant GGBFS and FA particles provided important information in terms of the ongoing reactions. Calcium silicate hydrates with partial substitution by aluminium from the SCMs were identified as the main reaction products forming in these systems.

Juan M. Etcheverry, Sreejith Krishnan, Yury Villagran Zaccardi, Susan Bernal Lopez , Nele De Belie
Critical Parameters Affecting the Carbon Footprint of Asphalt Mixes

There is the need for up-to-date environmental assessment of the different types and sources of asphalt mixes, including the new and developing modified mixes with engineered recycled wastes, such as recycled asphalt pavement (RAP), ground tire rubber (GTR), waste plastic pellets, etc. In recent years, the asphalt industry has shifted its focus to accelerating and adopting more sustainable practices to mitigate environmental issues pertaining to asphalt consumption, such as carbon dioxide emissions, resource depletion and human toxicity. Such impacts can be quantified and interpreted using life cycle assessment (LCA) tools, where the total environmental burden of a product or system is estimated. LCA can help us realize the sustainability potential of asphalt mixes reinforced with recycled material. Environmental impacts of a life cycle for a product or system are available in documents known as Environmental Product Declarations (EPDs), which consist of the following components in detail: product description and ingredients, LCA framework and functional unit, life cycle inventory and allocation method, data of environmental impacts indicators and impact category summary. In this study, 41 EPDs from an asphalt mixing plant in the State of Missouri in the U.S., were analyzed to identify the critical parameters contributing to the total carbon footprint per metric tonne of asphalt mix, considering the extraction of raw materials, transportation and production phases of a pavement life cycle. One of the more dominant environmental factors examined was the global warming potential (GWP) that is measured in terms of the effect of kilograms of carbon dioxide. These mixes varied in terms of type of asphalt mix, source of aggregates, aggregate size, binder grade, modifiers and additives, and recycled material content, mainly RAP. All unmodified mixes showed embodied GHG emissions of about 80 kg-CO2e. The mix that had the highest environmental impact, i.e., 231 kg-CO2e, was a PG76–22 SMA mix with 3.5% SBS modified binder. It is evident in all cases, however, that the extraction of raw materials and preparation of ingredient materials (i.e., Phase A1) dominates the carbon footprint of the production of asphalt mixes. Mixes incorporating lime filler had significantly higher GHG emission in A1 compared to those with other types of mineral filler. The transportation phase (A2) was the least impacting component of the material production stage, though most PPA modified mixes exhibited higher GWP in A2, compared to the rest, suggesting that the PPA is transported over large distances. A GWP of around 42 kg-CO2e (with negligible difference) is found for mix production processes (A3) at the asphalt plant in this study. This research can further bridge knowledge gaps and distinguish inconsistencies in asphalt pavement LCA that can make databases and assessments more efficient.

Nandita Gettu, William G. Buttlar
Reuse of Waste Plastic as an Alternative of Concrete Used in Blocks

Plastic production has increased globally due to the increase in the use of plastic, which results in a huge amount of plastic as waste. One of the major constituents of plastic waste is “Polyethylene Terephthalate (PET)”, mainly used in drinking bottles. The recycling of plastic waste for the production of new materials appears as one of the best solutions. Hence, one broad application can be in the infrastructure development in the form of plastic blocks. This paper is focusing to utilize PET bottles for making blocks. After melting in air tight container, PET was mixed with sand, and fly ash in the presence and absence of marble powder in fixed proportions. The mixes were then used to cast specimens for determining compressive strength, heat resistance, and water absorption and their results were analysed and compared with those of conventional concrete blocks. Based on the results obtained, it was concluded that these mixes have higher compressive strength, lesser water absorption, and are more resistant to heat than the Conventional Concrete used in blocks.

Sadaqat Ullah Khan, Tehmina Ayub
Fresh and Hardened Properties of Low-Clinker Cementitious Systems with Low-Co2 Footprint Produced with Carbonated Fine Recycled Aggregates

Concrete production is a major contributor to greenhouse gas emissions, mainly from the calcination of limestone to manufacture clinker. To address this issue, there is growing interest in developing more sustainable and eco-friendly alternatives to traditional concrete. One approach is developing composite cement to replace some clinker with supplementary cementitious materials (SCMs). Another solution is the carbonation of recycled concrete aggregates (RCA), a process that sequesters CO2 and improves the resulting concrete's mechanical properties. Few studies focus on the carbonation of fine recycled aggregates (fRCA), therefore, this study investigates the combined use of low-clinker cement and fine recycled concrete aggregate carbonation. Specifically, this study examined how different levels of substitution of carbonated fRCA affect the fresh properties (flow test) and hardened properties (compressive strength, flexural strength) of low-clinker cementitious systems. For this purpose, mortar mixtures were produced, substituting 0%, 50%, and 100% of the river sand by treated fRCA after subjecting to one-hour moist carbonation. In all mixtures, water/binder, sand/binder, and slump flow values were kept constant at 0.5, 3, and 175 ± 10 mm, respectively. High-range water-reducing admixture and adjusted water were added to provide the targeted slump-flow range of each mixture. The results showed that incorporating treated fRCA into low-clinker cementitious systems can improve their mechanical properties. Considering the industry's efforts to reduce CO2 emissions, this research could contribute to developing more sustainable building materials.

Mujeebulrahman Latifi, Torben Pede, Paul Dengler, Svenja Vogt, Lisa Koeniger, Harald Weigand, Rüdiger Kern
Environmental Assessment of Asphaltic Wearing Course Containing Mixed Plastic Waste in Singapore

Presently, the amount of plastic waste generated globally has doubled since the early 2000s yet the recycling rate for plastic waste remains below 10%. The accumulation of mixed plastic waste in municipal solid waste streams have spurred immense interest in recycling mixed plastic waste as polymer-modified bitumen in asphalt mixtures for pavement applications. This paper presents the findings from laboratory tests and field investigation conducted to evaluate the environmental properties of a novel mixed plastic modified asphalt mix. The laboratory works carried out include leachate characterization and microplastic detection assessment. Subsequently, full scale wearing course sections were constructed with control and mixed plastic modified asphalt mixes for field investigation. Groundwater and surface runoff samples were collected and analysed to provide valuable insights on the environmental properties and field performance of mixed plastic modified asphalt mixtures in operative conditions.

Kevin Jia Le Lee, Sook Fun Wong, Kelvin Yang Pin Lee, Nyok Yong Ho, Aung Lwin Moe
Study on Shrinkage and Elastic Modulus of Limestone Calcined Clay Cement Concrete

In Africa, one of the most promising options for lowering costs and environmental impact of concrete is the use of limestone calcined clay cement (LC3) systems. However, improper use of the constituent materials may result in a concrete with substandard properties. The results reported here are part of a larger study on the properties of LC3 concrete made with African raw materials and focus on deformation properties including drying shrinkage and elastic modulus of concrete with three different clinker levels and four different clays from South Africa and Tanzania, which are compared with two reference mixes; one with 100% CEM II/A-L 52.5 N and the other with 50% of cement replaced by ground granulated blast-furnace slag. Overall, it can be concluded that the LC3 mixes produce lower shrinkage strain than the reference mixes provided that the alkali level in the system is not high. The performance is mainly related to the high internal surface area of the clays which absorb some of the available water in the system, a resulting that the rate of loss of moisture in the paste is reduced. Also, results indicate that the elastic modulus performance of the LC3 concrete, regardless of the clinker content and type of clay, is similar to that of the reference mixes.

Emmanuel Safari Leo, Mark G. Alexander, Hans Beushausen
The Repairs, Renovation, Waterproofing of 50 Years Old “Wankhede Cricket Stadium” with Reduction of Carbon Foot Print of Over 10,00,000 Kgs of Co2

Wankhede Stadium is an iconic structure situated by Arabian Sea built in 1974 for the capacity of 39000 cricket loving spectators. Cricket is a religion in India like soccer is in many other countries. Several memorable matches and corresponding full houses is the common feature of ‘Wankhede Stadium’ over past five decades. Like any other stadium, frenzy of full house spectators occasionally and perennial aggressive saline weather resulted in heavy damage of the properties which include RCC walls, slabs, flooring, washrooms, steel structures and all the chairs. This rendered the stadium unusable. Excessive leakages through horizontal and vertical RCC surfaces in heavily saline and high rains conditions further affected this huge structure.Indian Premier League(IPL) matches are the annual big event of two months which is looked forward to by the entire country and other cricket playing countries. Many international players and visitors flock to be part of the excitement. Wankhede Stadium was the venue for the IPL in the year 2022 and the audit done beforehands brought out all the points mentioned above to be looked into on priority without any delay in the interest of the health of a structure and successfully hosting the IPL. Time was very limited for the operation. The renovation process had to conclude into world class facility and hence the activity was taken in a planned manner with high technological inputs to take care of leakages of basements, leakages of external walls, anti carbonation coatings and above all restoration of about 38000 polyethylene chairs which could not be discarded(despite the inclination and availability of funds) due to shortage of time. Novel technology was used of high adhesion ultra violet resistant Long Chain Nylon Reticulant(LCNR) special coating. These were significant steps in conservation of the stadium. The entire operation resulted in high reduction of carbon foot print. This case study sets an example to every such stadium undergoing restoration and renovation anywhere in the world to follow suit and be sustainable with ‘green approach’. The substantial reduction in the project cost is another major feature wherein major capital cost to replace the polyethylene chairs was totally avoided.

Ruchira S. Manjrekar, Surendra Manjrekar, Rahul Kshirsagar, Ishita Manjrekar
Carbon Reduction in Concrete Design and Construction

In the Global Cement and Concrete Association's Concrete Future 2050 Net Zero Roadmap, there are 7 categories of how to decarbonise the sector over the whole life of cement and concrete. The Design & Construction Efficiency category points to the important role of designers. Engineers and architects can contribute to reductions in embodied CO2e by actively having CO2e reduction as a design criterion as they optimise overall project topology, conduct their detailed element design, and prepare the material specifications.These embodied carbon reduction actions should be seen in the context of limiting whole life whole project CO2e emissions. Furthermore, there is the even broader context for designers of the biodiversity emergency, sustainable development and delivering a resilient built environment.

Andrew John Minson
Assessing the Trade-Off Between Sustainability and Resiliency of Reinforced Concrete in Corrosive Conditions: An LCA-System Dynamics Approach

Concrete has been categorized as a key contributor of carbon emissions. This is mostly associated with the production of the ordinary portland cement. In response to this, the concrete and cement industries are pursuing a path to reduce their carbon emissions, generally in accordance with the climate change goals outlined in the Paris Agreement. These efforts have resulted in the development of multiple low-carbon concrete systems aimed to reduce the environmental impact of cement and concrete. However, these new low-carbon concrete systems may not always result in a more resilient structure, i.e., a more durable and longer-lasting structure. In fact, some research indicates that the service life of structures containing lower carbon producing alternative cementitious materials may be reduced based on their performance in corrosive conditions. However, reduced service life does not necessarily mean there are no carbon emission benefits from the new material. An objective assessment of the trade-off between improved sustainability (i.e., reduced carbon footprint) and reduced resilience (i.e., reduced service life) is needed. This paper presents a life-cycle assessment-system dynamics approach to evaluate the trade-off between more sustainable reinforced concrete solutions and the reduced resiliency of these systems over time. The objective of this paper is to assess the effect of improved sustainability and the potential reductions in service life as a result of corrosion deterioration for low-carbon concrete alternatives. This paper also aims to provide information to better understand how short-term sustainability decisions can influence the longer-term sustainability goals when designing and constructing with reinforced concrete.

Erick Daniel Moreno Rangel, David Trejo
A New Technology for Full Replacement of Natural Aggregates with Bioremediated Recycled Aggregates and Its Lifecycle Assessment

The problem of construction and demolition wastes can be mitigated by recycling them as aggregates in concrete. However, high absorption and poor interfacial properties due to the attached mortar from old concrete use a major weakness resulting in only a partial replacement of natural aggregates with the recycled ones. This paper discusses a technique, bioremediated recycled aggregates (BRA), to bring their performance at par with the natural aggregates (NA). A biocement treatment has been applied to strengthen the attached mortar. The performance concrete with NA and 100% BRA is assessed for strength, water absorption, microstructure (using SEM with EDS) and micromechanical properties (using nanoindentation). It is observed that bio treatment recovers the performance of recycled aggregates at par with that of NA. The lifecycle analysis has demonstrated that BRA is clearly more sustainable than NA.

Abhijit Mukherjee, Abhijit Mistri, Navdeep Dhami, Sriman Kumar Bhattacharyy, Sudhirkumar V. Barai
Study on the Causes that Effect of Carbonation on the Elastic Modulus of Different Cured Concrete and Mortar Containing High Ggbs Content

Concrete using Ground granulated blast-furnace Slag (GGBS) has been widely used for a long time because it is expected to improve long-term compressive strength, high durability, and reduce environmental impact. However, previous studies have shown that GGBS is sensitive to the surrounding environment and easily carbonated, and it is necessary to know its compressive strength and elastic modulus in such an environment. In this study, concrete and mortar with different replacement ratios of GGBS were prepared to compare the compressive strength and elastic modulus of concrete and mortar. The specimens were cured under various environmental conditions, such as in tap water, in air and accelerated carbonation curing. The compressive strength and elastic modulus tests were conducted. As a result, a decrease in the elastic modulus was observed for specimens with a higher replacement ratio of GGBS on carbonated curing. This is thought to be caused by differences in the physical properties of the aggregate and cement paste, shrinkage of the matrix, or microscopic cracking due to hydration, and an investigation is underway to determine the cause.

Yurika Noguchi, Runa Yahiro, Takeshi Iyoda
Fabric-Reinforced Lime Composite as a Strengthening System for Masonry Materials: A Study of Adhesion Using Flexural and Tensile Testing

This study aimed to investigate the potential of using flax nonwoven fabric as a reinforcement material for lime composite with 20% metakaolin in strengthening masonry structures. The two types of masonry stones used in the study were subjected to flexural and tensile testing methods to determine the bond mechanism between the reinforced lime mortars and rocks. The study found that the bond strength values were directly related to the adhesion extension, which was influenced by the effective surface treatment (such as water, lime, and latex) the materials. To simulate the effects of carbonation in the environment, the reinforced masonry structures were exposed to CO2 chambers for 7 days before testing. The 7-day carbonation process was important in evaluating the effectiveness of the reinforcement material in strengthening the masonry structures under real-world conditions. The study found that the latex treatment was the most effective in strengthening the masonry structures. Scanning electron microscopy (SEM) was used to evaluate the composite and behaviour adhesion reinforcement, and the results confirmed the effectiveness of the latex treatment. However, further research is needed to validate these findings and assess the potential of this reinforcement system for masonry structures. The use of sustainable reinforcement materials like flax nonwoven fabric has the potential to reduce the environmental impact of construction and improve the durability and strength of masonry structures. Therefore, this study has significant implications for the construction industry and could contribute to the development of sustainable building materials and practices.

Ali Rakhsh Mahpour, Josep Claramunt, Monica Ardanuy Raso, Joan Ramon Rosell
A Performance Enhancement Technique for Recycled Concrete Aggregates

Recycled concrete aggregates (RCAs) typically derived from construction and demolition waste differ from natural aggregates as the former contains hardened cement paste. The residual cementitious mortar is comprised of fine aggregates, hydrated, and un-hydrated cement particles, which have a higher porosity due to the existing cracks and voids. This leads to an increase in water absorption, reduced density, reduced aggregate crushing, and reduced impact strengths when compared to virgin aggregates. Furthermore, the interfacial transition zone between the old adhered mortar and the new cement matrix creates an additional weak link. This results in decreased mechanical and durability strength parameters of the hardened recycled aggregate concrete (RAC). Construction and demolition waste consists of approximately 40% of waste concrete. Recycling this waste to produce RCAs promotes several advantages. A sustainable alternative to that of virgin aggregates is generated, and there is a reduction in energy consumption and CO2 emissions during the quarrying of raw materials. Within this study, an innovative technique was developed to treat the coarse RCAs using a waterproofing agent. The water absorption was reduced by 50% while the bulk density and specific gravity had almost a 1% increase after treatment. The treated coarse RCAs were used to create new concrete at 0%, 30%, 50%, 70%, and 100% replacement ratios to natural concrete aggregates (NCAs) to investigate the fresh and hardened concrete parameters. The treated RAC showed improvement in workability, hardened density, and compressive strength when compared to the untreated RAC.

Rekha Rampit-Greaves, Jovanca Smith
Informal Sector Inclusion in Sustainable Concrete Construction in Africa

Concrete used as a construction material is inevitable in Africa’s rapid urban growth, despite its significant contribution to carbon emissions. Hence, best practice concrete with reduced Portland cement clinker needs to be applied. The highly informal nature of Africa’s construction sector could impede the implementation of sustainable concrete construction. Although urgent need for economisation unintentionally often leads informal actors to operate according to circularity principles, the sector lacks awareness of climate challenges and incentives for adopting climate-friendly materials and technologies. In addition, the informal sector is prone to fraudulent adulterated materials and components causing challenges for safe and durable construction. The authors elaborate on the crucial role of the informal sector in driving sustainable construction forward, despite the lack of policies and disinterest from regulatory bodies. Solutions through education, communication, and quality control are proposed and discussed.

Wolfram Schmidt, Patrick R. Cunningham, Ada Farai Shaba, Kolawole A. Olonade, Joanitta Ndawula, Angela Tetteh Tawiah, Joseph Mwiti Marangu, Pheladi Tlhatlha, Emmanuel Obeng
The Comparison of the Bleeding Potential of Chip Seals Developed with Recycled Materials and Limestone Aggregates

Waste glass accounts for huge quantities throughout the world. Although some part of this waste material is recycled, a considerable part of waste glass cannot be reused and recycled due to the glass remanufacturing strict limitations. Hence, reusing waste glass in construction projects can be a cost-effective and environmentally friendly method to recycle this material. One of the preventive or corrective pavement maintenance approaches is chip sealing which can be constructed easily and rapidly on old pavements. In this study, the conventional limestone aggregates were replaced with 100% waste glass to develop a new chip seal. A cationic rapid-setting bitumen emulsion was also utilized to develop the chip seal. Different experimental methods were used to compare the performance of the new chip seal and the limestone chip seal, including the sand patch test and an adjusted load wheel test (LWT) for bleeding resistance. The test result revealed that the macrostructure of this waste material was in the standard range of chip seals, providing sufficient mean texture depth (MTD) for posted traffic speed over 70 km/h. Besides, the bleeding potential of glass chip seal was approximately two times higher than limestone aggregates due to lower Los Angeles abrasion resistance. Overall, as the abrasion resistance of glass aggregates is not as high as limestone aggregates, it is recommended to use them for the chip sealing of bicycle paths, low-volume roads, driveways, and parking lots. Finally, reusing these materials as chip seal aggregates can recycle high quantities of these materials and reduce the demand for natural aggregates.

Mohsen Shamsaei, Alan Carter, Michel Vaillancourt
Integration of Concrete Sustainability Information as Part of the BIM Process

Sustainability objectives for concrete require that EPD data for each raw material be assembled into a digital twin model of the mix design. This is typically accomplished by manually accumulating the data and creating a document using a manual consulting approach. These manual documents are static PDFs and make it difficult to share the data with other models and for producers to quickly produce new mix designs and EPDs. Processes have now been created in the concrete industry which allow a concrete producer to assemble not only EPD documents for a project, but to also utilize EPD values to assist in the selection of concrete mix designs that will have the lowest global warming potential, or other environmental factors. As sustainability data is increasingly computerized, gaps in the sustainability modeling process become apparent. One of these gaps is the lack of standards on how to accumulate and share this data. As BIM models improve, this data will be able to be incorporated in a comprehensive environmental footprint for a project.

James M. Shilstone Jr., Chris Erickson, Rob Piosik
Prediction of the Resource Amount of Calcium Carbonate Concrete Materials Generated from Concrete Stocks in the Past and Future

Providing excellent performance as a structural material, concrete has long been essential for modern civilization and recognized as a material that will continue to maintain and support the development of human society. Now that recycling of concrete in a completely closed loop has become technically feasible, concrete is being seen in a new light. On the other hands, the huge issues regarding carbon dioxide emissions all of the world are a concern in the construction field as well as in society. To solve this problem, a concept for new Calcium Carbonate Concrete (CCC) is proposed. This paper is focused on prediction of the resource amount of CCC, which is manufactured by treating concrete waste as a raw material with calcium hydrogen carbonate in which carbon dioxide is dissolved. It was described the details of the amount of supply potential of concrete waste from the past 1950s to the future in 2050s and analysed a resource recycling scenario based on the long-term transition future perspectives.

Masaki Tamura, Takafumi Noguchi, Ippei Maruyama, Manabu Kanematsu, Ryoma Kitagaki, Satoshi Fujimoto, Masato Tujino, Takayoshi Masuo, Hikotsugu Hyodo, Hiroshi Hirao
Carbonation and Shrinkage Behavior of Alkali-Activated GGBS Mortar Incorporated with Supplementary Precursors

By increasing the investigations and applications of alkali-activated concrete, improvement of its behavior is a promising idea by using different materials and specifically secondary raw materials. In this study, an alkali-activated GGBS (AAG) mortar mixture having a ternary activator system including NaOH, Na2O.nSiO2, and K2O.nSiO2 was considered. The effect of the substitution of fly ash, metakaolin, calcined clay, and calcium alumina cement (CAC) by ground granulated blast furnace slag (GGBS) on carbonation resistance, as well as shrinkage behavior was investigated. It was observed that the replacement of GGBS with CAC reduced the total volume of pores, and their sizes. By the way, the shrinkage behavior of that showed about four times higher strain than the mixtures without CAC. On the other hand, the replacement of CAC with GGBS in AAG slightly improves the carbonation resistance, as well as capillary porosity. However, the substitution of GGBS with fly ash, metakaolin, and calcined clay resulted in a reduction of the carbonation resistance, as well as an increase of porosity.

Syamak Tavasoli, Ahmad Waheed Sadeed, Wolfgang Breit
Optimized Mix Design Regarding Cost and Sustainability

The authors developed a model to optimize the design of concrete mixes in terms of their raw materials’ cost. The model simulates the effect of the characteristics and proportions of raw materials on the behaviour of concrete in relation to: consistency and cohesiveness of the fresh mix and compressive strength of the hardened concrete. Different alternative sets of constituents can be analysed simultaneously, with the model being calibrated with data of existing concrete mixes. For each set, the mix - that complies with the specifications - of lowest cost is obtained, applying an optimization engine based on the CobyLa2 simplex method, subjected to specification boundaries (e.g., w/cmmax, entrained air, etc.). The suitability of the software was validated during successful applications across the Holcim world. Currently, the authors are in the process of upgrading the software to extend the model to find the mix with the lowest CO2-Footprint (and/or other sustainability indices) and to improve the software’s user-friendliness (capturing the required data directly from the concrete plant databases). The suitability of the software is demonstrated by optimizing several mixes, using real data of nine alternative industrial cements, with contents of addition between 0 and 69% (Silica Fume, GBFS, PFA, Limestone Filler) and CO2-Footprints between 300 and 900 kgCO2 per ton of cement. It is shown that the cement providing the most sustainable solution depends, on a case-by-case basis, on the mix specifications. The paper describes the background of the model and presents and discusses the results of the optimizations.

Roberto J. Torrent, Hans Musch
Integrated Structural and Energy Retrofitting Based on Cementitious Composites and Phase Change Materials

The retrofitting of existing buildings is crucial for improving their structural safety, reducing damage, and enhancing energy efficiency while maintaining their distinctive features. Seismic retrofitting and thermal energy retrofitting are two effective approaches that can be integrated to achieve enhanced seismic performance and reduced energy consumption. Seismic retrofitting aims to strengthen buildings against seismic forces, while thermal energy one involves measures that enhance the building envelope’s performance to reduce energy consumption. The use of phase change materials (PCMs) in building construction has gained significant attention due to their potential for energy efficiency and sustainability. By correctly incorporating PCMs into construction materials, the thermal performance of existing buildings can be improved while preserving their unique characteristics. The integration of PCMs with structural retrofitting techniques, such as textile-based composites, provides an attractive option for enhancing both seismic and energy retrofitting simultaneously, resulting in improved seismic performance and energy efficiency for existing buildings. Integrated retrofitting is an approach that evaluates the technical and financial aspects of retrofitting to achieve a balance between energy efficiency and cost-effectiveness. The primary objective of this review paper is to examine the advantages of incorporating PCMs in the process of integrated structural and energy retrofitting. Additionally, this paper aims to provide a comprehensive overview of the various retrofitting methods that can be employed to enhance the seismic performance and energy efficiency of existing buildings.

Mahdi M. K. Zanjani, Ignacio Peralta, Victor D. Fachinotti, Antonio Caggiano
Thermal Energy Storage of Integrated Energy and Structural Retrofitting Systems for Masonry Walls: Cases Studies and Numerical Assessments

This paper presents ongoing research activities that investigate the development of carbon-neutral binder-based composites for Thermal Energy Storage (TES) and energy retrofitting in multi-layer stone masonry wall systems. The study involves preliminary laboratory characterizations of integrated energy and structural retrofitting systems for historical masonry walls, which incorporate EPS boards, mineral adhesives, natural fibres, thermal mortars, and Phase Change Materials (PCMs). Main aim of this paper is to report on a numerical approach for modelling TES and thermal responses of these systems in multilayer cases. Specifically, the fixed grid method is used to solve the well-known Stefan problem in Phase Change processes, and an enthalpy-based approach and apparent calorific capacity method are proposed for solving the multilayer wall heat flow phenomena. Three different virtual locations, including Genova, Italy, Sauce Viejo, Argentina, and Frankfurt (am Main), Germany, are selected as case studies. By analysing the total undesired heat loads to which the walls are exposed, the energy performance of the multilayer wall systems is assessed.

Mahdi M. K. Zanjani, Ignacio Peralta, Michela Rossi, Maedeh Mohit, Víctor D. Fachinotti, Dionysios Bournas, Antonio Caggiano
R3 Revealed – Inside Views from Calcined Clay Calorimetry Brews

The R3 test method is currently experiencing rapid adoption worldwide as an essential tool for the assessment of potential supplementary cementitious materials for use in concrete. Originally developed for calcined clays, the resultant hydration phase assemblages have been well characterized by bulk techniques such as X-ray diffraction, thermogravimetric analysis, and nuclear magnetic resonance, but relatively less work has been dedicated to seeing, microscopically, the inner workings of the method. With this in mind, this foray into the formerly private world of calcined clay pastes was undertaken, to see what goes on behind those closed calorimeter chamber doors. Like some sort of scientific construction materials conference proceedings click-bait, this abstract is intended to whet the appetite of those who demand to know more about such elusive and camera-shy phases as monocarbonate and katoite. And for those who choose to turn the page, and succumb to such temptations: buckle your seatbelts for a twisted tortuous ride through hydrated paste pore structure, as revealed by fluorescent epoxy impregnation and scanning electron microscope images.

Pengfei Zhao, Karl Peterson

Assessment and Enhancement of Concrete Durability in Challenging Environments

Determining Factors Affecting Pitting Corrosion of Stainless Steel Reinforcing Bars

Corrosion of steel reinforcing bars (rebar) caused by chloride ions from seawater or deicing salts is a major deterioration mode of reinforced concrete (RC) structures. A practical solution to improve this durability challenge is the use of corrosion resistant materials such as stainless steel (SS) rebar. Pitting corrosion is the most prevalent and insidious corrosion type on SS rebar, which considerably impacts structural load-bearing capacity and safety. In addition, the manufacturing process of ordinary Portland cement (OPC), a key ingredient in concrete production, contributes to 8% of the global carbon footprint. A common approach to improve this sustainability challenge is through the use of new cement blends, such as Portland limestone cement (PLC), and sustainable supplementary cementitious materials (SCM) to partially replace OPC. The present study, being phase one of a research program, aims to investigate and report key influencing factors, including rebar alloy composition, SCM incorporation, and chloride concentration, affecting the pitting corrosion behavior of different SS rebar grades. The outcome of this literature review study will be used, in the next phase, to develop a comprehensive model needed to improve understanding of the factors affecting the pitting corrosion in SS rebar in various sustainable concrete mixes. In general, the research outcome will help the researchers evaluate rebar's corrosion characteristics, creating a safer and more sustainable environment while also contributing to reducing CO2 emissions.

Mohaddeseh Abdolhosseini, Ibrahim G. Ogunsanya
Durability Problems of Reinforced Concrete Structures on the Lagos Lagoon in Nigeria

The ingress of sulphate and chloride salts into reinforced concrete structures has led to the continuous deterioration of the bridge structures and some of the jetties on the Lagos lagoon. This research investigated the current durability problems associated with these structures using indirect methods. Modelled samples of grades 30 and 40 cubes and reinforced concrete beams were submerged in the lagoon water that contains high salt contents while control samples were submerged in freshwater for a one-year test. Compressive, flexural and pull-out tests were carried out on the concrete at 28, 90, 220 and 365 days. ANSYS software was used to simulate the reactions of the beam elements to loading on the 28th and 365th days. There was a general reduction in strength for concrete samples cured in lagoon water, while the freshwater-cured concrete increased in strength. A mathematical model was used to determine the deterioration rate of concrete elements, this mathematical model was compared with an existing model to determine it reliability. The current deterioration rate of the concrete elements was used to predict the future strength of all the concrete samples over a period 10 years.

Joseph Akinyele, Uvieoghene T. Igba, John O. Labiran
Optimizing Mixture Components, Shiv Size and Content in Hempcrete for Thermal Capacitance

This study investigates the thermal performance of hempcrete, for use as the building envelope in masonry walls. Three samples of hemp hurds were sourced from Canadian harvests and a fourth from France. Each hemp hurds sample was cut to a different particle size distribution, and then incorporated at 5 binder-to-hemp ratios. Portland cement Type GU and hydrated lime were used in equal amounts to form the binder. The resulting mixtures were first tested for thermal conductivity and specific heat capacity. The experimental findings were then incorporated into an ANSYS based model, to predict the thermal energy stored and lost by each mixture when used as a building envelope for a masonry wall. The results show that while smaller hemp particles favour greater volume of interface, larger particles lead to higher porosity. In turn, they result in lower thermal conductivity, lighter hempcrete and hence higher thermal capacitance. Together, these properties result in higher thermal energy storage. The optimum thermal performance was obtained with hemp particles under 3 mm wide and shorter than 10 mm.

Ahmed Al-Tamimi, Vivek Bindiganavile
High-Performance Concrete Cover – A Smart Way to Increase Service Life and Reduce Co2

Reduction in CO2 emissions of reinforced concrete construction is critical to mitigate the effects of climate change. Durable infrastructure with a long service life is not only an important part of CO2 reduction but is a general sustainability objective for society. However, durable concrete construction traditionally uses high cement content mix designs and increased concrete cover which can increase member thickness. Both will typically result in increased CO2 emission. Use of supplementary cementing materials is acknowledged as being the primary means to reduce CO2 emissions in concrete, but other methods that further reduce emissions include smart construction techniques that either reduce the volume of concrete used or maximize the use of low cement content mix designs. This paper discusses the method of applying a bonded cement-based high-performance shotcrete or hand-applied mortar layer to create a high-performance concrete cover (HPCC) over a low CO2 emission concrete core. Case studies will be presented where this technique is already in regular use for both new construction and restoration to provide enhanced cover properties and replace cover deficiencies. Possibilities for further use of the method will be discussed.

Ata Basaran, Kelly Nix, Kyle Gilmour, Paul Derby, Patrick F. McGrath
Effects of Hydrolytic Aging on the Behaviour of Nano Silica (SiO2)-Treated Spruce Wood

Wood is a viscoelastic composite material that has been historically prominent in the construction of buildings and continues to see widespread use. When used for exterior applications, wood is exposed to dynamic environmental conditions and can degrade if left untreated. Previous research has proven that vacuum impregnation of the lignin matrix with a silica (SiO2) nanoparticle colloid can enhance the viscoelastic properties, increase the density, and reduce the water uptake of wood. However, the behaviour of SiO2-treated wood under different environmental conditions over time has yet to be fully explored. This research aims to examine the durability and performance of SiO2-treated spruce wood samples subjected to accelerated hydrolytic aging conditions. Spruce wood samples treated with 40% SiO2 nanoparticle colloid under a −90 kPa vacuum were placed in an environmental chamber at 90 ºC and 80% RH. The samples were removed at regular intervals and thermogravimetric analysis, dynamic mechanical analysis, and tensiometry tests were performed. When compared to the results obtained from a set of non-treated samples, it was found that the SiO2-treated samples exhibited lower water uptake values as well as a lower rate of decrease in peak cellulose degradation temperatures when subjected to hydrolytic aging. The effects of the aging conditions on the viscoelastic properties of the samples were also found to be insignificant. These results indicate that the durability and properties of wood can be improved through nano-SiO2 impregnation as the material remains relatively stable when subjected to high temperature and humidity conditions over time.

Callisto Ariadne Beuthe, Reza Foruzanmehr, Marzieh Riahinezhad
Corrosion-Induced Cracks in Reinforced Concrete Slabs Incorporating Multi-peak Nonuniform Rust Layer

Corrosion-induced concrete cracking is of importance in evaluating service life of reinforced concrete (RC) structures. In this study, an advanced 3D finite element (FE) model was developed to simulate crack propagation in RC slabs. The FE model showed its originality by incorporating multi-peak asymmetrical nonuniform expansion of rust between the steel bar and concrete. The rust expansion was established based on Asymmetrical Generalised von Mises distribution (AGvM model). An experimental programme of six RC slabs with three different rebar configurations was conducted to validate both the AGvM and the 3D FE models. As a result, it showed that the proposed AGvM model could better simulate nonuniform rust distribution around the rebar than the other six existing mathematical models. The proposed FE model could reasonably predict crack development in RC slabs with different rebar configurations. Based on the test results and numerical models, effects of rebar configurations on crack patterns induced by corrosion were also discussed.

Huy Tang Bui, Kang Hai Tan
Potential Strength and Durability of Blended Low-Grade Limestone Calcined Clay Cement Concrete

In the ternary cementitious systems, limestone along with calcined clay shows good mechanical and durability performance at a lower clinker factor as compared to the ordinary Portland cement (OPC) concrete system. The amount of cement-grade limestone in mine reserves is decreasing as the demand for cement rises. This makes it important to explore the potential of low-grade limestone rejected by cement industries during clinker production. This work focuses on the use of rejected limestone along with calcined clay in ternary cementitious systems. The experimental work includes clinker substitutions of 30 wt% and 45 wt% with calcined clay and limestone in 2:1 proportion. Mechanical properties such as compressive strength and durability parameters of concrete like chloride migration and surface resistivity were assessed. The results indicate that 30% ternary blended concrete mix has better compressive strength and durability as compared to ordinary Portland cement concrete mix and the 45% ternary mix has very good durability performance. The overall performance of LC3 based mixes was similar, irrespective of the type of limestone used in the blends. This implies that dolomitic limestone based LC3 blends can be successfully used in producing durable concrete.

Amitkumar R. Chauhan, Manu Santhanam
Chloride Transport Characterisation in Self-healing Concretes

It is essential to evaluate the deterioration of concrete structures in a chloride-laden aggressive environment, which may lead to the corrosion of embedded reinforcement and eventually to the loss of the integrity of the concrete structure. Several tests are available in the literature that evaluates the ingress of deleterious chemical species into the concrete matrix, but an uncracked state of concrete is largely considered in these tests. This work demonstrates the testing of concrete samples from full-scale beam elements, the introduction of cracking imitating the realistic crack specifications, and analysis for service life evaluation for cracked concretes. The autogenous property of crack healing in concrete is amplified by the addition of self-healing agents – crystalline admixture and bacteria. This study highlights that the presence of cracks in concrete significantly influences the chloride ingress profile. Two-fold diffusion of ions occurs – one perpendicular to the exposed surface and the other perpendicular to the crack walls. It is reported that the cracked and uncracked migration coefficients through and across the crack are highly affected by its existence, not necessarily controlled by the crack width at the surface. Consequently, the service life evaluation for a cracked concrete element needs to be adapted to account for the influence due to cracking.

Kiran Dabral, Esteban Camacho, Pedro Serna, Macría Cruz Alonso
Acid Resistance Evaluation of Expansive and Non-expansive Calcium Sulfoaluminate Cements

When sulfate to ye’elimite ratio of Calcium sulfoaluminate (CSA) cement increases, it changes its application from rapid-strength cement to expansive (shrinkage compensating) cement. CSA cement is now getting attention because of its low carbon footprint. They are potential candidates for sewer structures where acid attack is the major durability threat. However, acid resistance of CSA is less explored. Acid resistance of commercial CSA cement (i.e., non-expansive) paste of a higher water-cement ratio of 0.6 and 0.5 were considered first. Then the mix was converted to an expansive binder by blending with 15% gypsum, and the acid resistance was evaluated. The acid resistance was evaluated by acid immersion tests with hydrochloric acid (HCl) of 1% and 2% conc., and sulfuric acid (H2SO4) of 2.95% conc. The results show that expansive CSA cement showed poorer performance than non-expansive CSA cement in acidic environment though the former had slightly higher compressive strength than the latter before acid exposure. This could be attributed to the modified phase composition in expansive CSA, as observed from the results of recently developed acid consumption tests. Similar results were observed in case of sulfuric acid attack of mortars. Though gypsum blending improved the mortar strength, the acid resistance was reduced indicating the importance of chemical composition against acid attack.

Tom Damion, Piyush Chaunsali
Understanding the Carbonation Performance of Cements Containing Calcined Clay

Low-purity calcined clays are becoming increasingly popular as supplementary cementitious materials (SCMs) due to their wide availability, and potential ability to reduce the carbon footprint associated with concrete production. To ensure the longevity of concrete structures, it is crucial to understand the mechanisms governing long-term durability when using new SCM-containing cement formulations. Understanding of the carbonation resistance of cements containing calcined clay is limited, and this remains a concern. This research is part of the collaborative USA-UK project “Response to CO2 exposure of concrete with natural supplementary cementitious materials” (RENACEM), aiming to understand the connections among the properties of natural clays, activation treatments to enhance their chemical reactivity, and the response to CO2 exposure of cements, mortars and concretes produced with them. The current study presents the carbonation resistance results of binary and ternary materials containing calcined clays upon exposure to natural CO2 concentrations under controlled relative humidity (57% RH), resembling in-service conditions. Four cement compositions were studied, including a CEM I (OPC), CEM I with 30% limestone substitution (L30), CEM I with 30% calcined clay substitution (CCF30) and CEM I with 30% calcined clay + 15% limestone (CCF30L15). The carbonation performance of these binders was monitored using pH indicators on cement paste and mortar specimens. Scanning electron microscopy coupled with EDX was used to identify the carbonation front. The results demonstrate that chemical alterations identified using analytical techniques can be used to characterise the reaction front of these materials, offering more insights into the effect of carbonation beyond potential changes in alkalinity of these systems.

Yuvaraj Dhandapani, Leon Black, Maria C. G. Junger, Susan A. Bernal
Effect of Graphene Oxide on Chloride ION Penetration in Standard Canadian Mixes

This study was conducted to evaluate the impact of a small percentage (0.03%) of graphene oxide (GO) on the properties of cement-based materials. The GO dispersion method (superplasticizers and sonication) and the use of binary binders were also variables of the study. To make this technology potentially accessible to concrete producers, commercially available GO was used for the trials. Through isothermal calorimetry, it was possible to characterize the hydration reaction of the GO-modified cementitious materials. The effect of GO is visible on the heat release rate curves, especially when dispersed by a superplasticizer and by a combination of superplasticizer and sonication. This effect is mainly noted in the amplitude of the calcium aluminate (C3A) peak. The compressive strength tests were used to evaluate the mechanical strength of mortar at 1, 7, and 28 days. To evaluate the effect of GO from a practical application point of view, chloride ion penetration tests were carried out at 28, 56, and 91 days, on concretes based on the Ministère des Transports (MTQ) and Canadian Standard Association (CSA) V-S/C-1 mixes. The results showed that GO slightly reduces the penetration of chloride ions varying with the cure period and the type of concrete mix.

Thomas Duplessis, Victor Brial, Claudiane Ouellet-Plamondon
New Systems for Sustainable Strengthening and Service Life Extension of Existing Structures

Over the past 10 years, the authors have developed a whole toolbox of methods for strengthening existing structures. Two methods have proven to be particularly effective. One is the use of concrete screw anchors, which can be inserted into concrete cross-sections as post-installed reinforcement and can thus replace missing shear and punching reinforcement in particular. Secondly, the use of thin, textile-reinforced concrete layers that can be applied to existing structures to reinforce the load-bearing capacity for bending, shear and torsional loads. The effectiveness of the reinforcement methods was evaluated in numerous experimental and numerical tests. This has led to technical approvals by the building authorities of the reinforcement systems in 2019. Thus, these methods are now available for a broad application in practice. The article discusses the effectiveness of the reinforcement methods on the basis of research results, but above all on the basis of pilot projects carried out. It can be shown that by the enhancement of life time of existing structures by these methods a huge impact on CO2-reduction can be reached.

Jürgen Feix, Christoph Waltl, Johannes Lechner
Autogenous and Stimulated Healing of UHPC Under Torsion Induced Cracking

Autogenous and stimulated healing capacity of UHPC is well known, though in the entirety of studies cracks induced by means of flexural or direct tension tests have been studied. In the attempt of widening the case study database and promote self-healing cement-based materials into a variety of structural applications and broaden its concept to the upkeep of the material and structural load bearing capacity, this study focuses on the effects of self-healing in UHPC under torsional behaviour. Both autogenous and stimulated, via crystalline admixture, healing capacity have been considered, investigating cylinder specimens submitted to torsional behaviour. The capacity of the material not only to heal the induced skew cracks, under wet/dry exposure conditions, but also to maintain its multiple cracking capacity and to promote, upon successive reloading after healing, the formation of new cracks instead of the simple reopening of closed ones. A validation of the experimental campaign is also proposed via fracture-mechanics based finite element analysis.

Liberato Ferrara, Virginia Lo Gatto, Giacomo Rizzieri, Didier Snoek
20-year Monitored Performance of Distributed Galvanic Anodes

The development of cost-effective methods to mitigate rebar corrosion in existing chloride-contaminated bridge decks is a key research objective of many asset owners. Such methods and technologies are vital to asset owners for the management of ageing transportation infrastructure. One such method is the use of distributed galvanic anode systems to provide cathodic protection to reinforced concrete. A distributed galvanic anode system was installed in the bridge deck of North Otter Creek Bridge on Highway 9 near Walkerton, Ontario in 2003. The performance of this system has been monitored every year since its installation through direct readings of the system’s polarization and current density. Ministry of Transportation Ontario (MTO) has also installed distributed galvanic anode systems in existing abutments as part of rapid superstructure replacement projects in Ottawa; the first was installed in 2007. Distributed galvanic anode systems have also been used in pier jackets and other bridge deck overlays. The monitoring data including current density and depolarization collected to date shows effective continuing corrosion protection. This paper will first discuss the process of rebar corrosion in a bridge deck, then introduce the distributed galvanic anode system. This paper will then detail the anode monitoring data that has been collected and an analysis of the performance and ageing of distributed galvanic anodes in a number of applications.

Liao Haixue
Pullout Behavior of Straight Steel Fiber Reinforced UHPC Subjected to Single Cryogenic to Elevated Cycle

This paper aims to reveal the performance characteristics of steel fiber reinforced concrete under extreme temperature environments, and provide possibilities for concrete engineering applications under extreme temperature environments. In this study, herein, pullout characteristics of straight steel fiber embedded in unreinforced Ultra High-Performance Concrete (UHPC) within the temperature range of −170 ℃ ~ 200 ℃ were evaluated. The results showed that, in the single cryogenic-elevated cycle, the bond strength and pullout energy of UHPCs enhanced at −170 ℃, and recovered to the same value as ambient temperature after the cryogenic-ambient freeze-thaw cycle. The pullout performance of UHPCs decreased at 200 ℃, and had an obvious improvement after a complete cryogenic-elevated cycle. Within the large-span temperature variation, the characteristics of the matrix and the thermal expansion between the matrix and the steel fibers are the reasons for the change in the bonding performance of UHPCs.

Bei He, Hongen Zhang, Xinping Zhu, Zhengwu Jiang
Proposal for a New Maintenance and Deterioration Prediction System Using Center of Core

Reinforced concrete structures are used worldwide, but there are many deteriorated structures needing repair or renewal due to steel corrosion and concrete deterioration. To efficiently maintain and manage these structures, it is essential to establish more accurate deterioration prediction systems. In the current maintenance management, the surface of the structure is visually inspected for cracks, rust soup, delamination and peeling. If an abnormality is detected, the structure should be investigated using non-destructive test or a core should be taken to investigate the compressive strength and carbonation depth. The criterion is whether the deterioration factor has reached the rebar. In these cases, it is possible to deal with steel corrosion caused by deterioration factors penetrating from the surface layer. However, it is not possible to take into account internal defects and internal cracks caused by the materials used and construction, or concrete deterioration such as ASR and frost damage. The proposed system simultaneously assesses the condition of the internal concrete from cores taken for preventive maintenance and other purposes, using the centre of the core to (1) compare the surface and deep layers, (2) detect internal deterioration, and (3) predict deterioration based on the results of the comparison.

Takeshi Iyoda
Durability of Waste Glass Fine Aggregates in Cement Composites

The disposal of Waste Glass (WG) in landfills is a critical environmental challenge faced by most countries around the world. Therefore, reusing of crushed glass as aggregates reduces the utilization of natural resources, thereby minimizing greenhouse gas emissions and increasing the sustainability of natural aggregates. Although it has a near to zero water absorption, enhanced dimensional stability and reduced drying shrinkage, crushed waste glass aggregates have limited use in cement-based applications due to its severe alkali- silica reaction (ASR) proclivity. This paper presents effective ways of incorporating waste glass aggregates in cementitious systems as a partial replacement of fine aggregates. This study explores the use of different combinations of Calcium Aluminate Cement (CAC), Ordinary Portland Cement (OPC) and Ground Granulated Blast Furnace Slag (GGBS) as an optimal matrix for reduced interaction between silica and the alkaline cement paste. Results showed a steady increase in the compressive strength of mortar mixtures incorporating 15% waste glass as a fine aggregate replacement material, and varying percentages of CAC, GGBS and OPC as binder. Furthermore, the paper evaluates the ASR performance of glass incorporated CAC, OPC and GGBS mixtures.

Darshan Chowdary Kandra, Obinna Onuaguluchi, Nemkumar Banthia
Effects of Natural Drying and Carbonation on a Method for Investigating Fire-Damaged Concrete Using Phenolphthalein Solutions

Assessing the depth of the heat impact caused by fire damage is important for planning the repair and reinforcement of fire-damaged reinforced concrete (RC) structures. One method used to investigate fire-damaged concrete structures is measuring the depth of carbonation, which has been reported to increase after fire damage. And, previously, using an anhydrous phenolphthalein (PP) solution had believed to identify regions heated to around 500 ℃ (areas with CaO formation). Few studies have investigated or analyzed the chemical changes in cement hydrates in detail. In this study, heating experiments were conducted under N2 using an electric furnace, focusing on the chemical changes in cement hydrates due to high-temperature heating, the coloring of PP solutions with and without water, and the moisture transport in concrete caused by high temperatures. Upon heating cement paste, areas where CaO was formed or carbonated by thermal decomposition could not be determined by observing the color of the anhydrous PP solution, whereas areas heated above approximately 150 ℃ almost dried out could be successfully evaluated. In heating experiments on concrete cores taken from carbonated RC structure before being exposed to fire, the PP solution with water enables judging carbonated areas where CaCO3 pyrolyzed to form CaO (i.e., areas heated above approx. 600 ℃) in addition to determining dry areas. However, this method is not applicable to concrete where carbonation has not progressed significantly.

Toru Kinose, Natsuki Yoshida, Daiki Atarashi, Kei-ichi Imamoto
Durability of Concrete According to Performance-Concept – Inspection of Bridges

In current codes the durability of concrete structures is usually guaranteed by describing mix design parameters such as maximum w/c-ratio, minimum cement content and minimum concrete cover. European and German standards (DIN EN 1992, DIN EN 206-1, DIN EN 13670 and DIN 1045 part 2 to 4) specify relevant requirements. However, it has been observed that there seems to be a contradiction between results of life cycle calculations based on fib-Model code and deemed-to-satisfy-rules used for durability in Germany. Hence, a research project was initiated to evaluate the performance of structures with respect to durability. The objective was to assess the condition of a representative group of structures planned and built according to current German standards. The sample was made of five bridges built with various cement types (CEM I, CEM II and CEM III) located in different parts of Germany. The bridges investigated were in use for 11 to 15 years. The aim of the bridge inspections was to come up with information about material performance and execution quality. Material tests were carried out in-situ on the structures and in the laboratory. The in-situ investigations consisted of visual inspection of concrete surfaces, measurement of concrete cover, measurement of electrical resistance and carbonation depth. Laboratory tests on concrete cores taken during the inspections were carried out to investigate concrete performance. The laboratory testing included compressive strength, carbonation depth, chloride content in various depths, chloride migration test and freeze-thaw-tests. This article covers the chlorides at various depths only.

Stefan Kubens, Juan Mauricio Lozano-Valcarcel, Thomas Kränkel, Christoph Müller, Christoph Gehlen
Self-healing Performance Evaluation for Concrete Beams with Artificial Inner Tunnel and Repair Agents by Non-destructive Testing

In this study, the self-healing system was developed using an artificial inner tunnel and a repair agent for the purpose of automatic repair of cracks. The effect of concrete beam section type on repair performance and the change in strength recovery rate when repair was repeated, and the efficiency of repair performance evaluation by various non-destructive tests were carried out. As a result, it was confirmed that the strength recovery rate after repeated repairs recovered to the original level of strength and rigidity before cracking occurred in all cases of each beam section type.

Sanghun Lee, Sanjay Pareek
Thermal and Alkaline Aging of Wood as a Construction Material Measured by Atomic Force Microscopy

Wood has been used as a construction material by human beings since ancient times. Under dry conditions, wood structures can sustain hundreds or even thousands of years. The combination of lignocellulosic materials with concrete reduces the mass of structures, reduces the waste material, increases ductility of the structure, and reduces the construction cost. Natural fibers or wood particles are used as the reinforcements in concrete and to reduce weight; composite timber-concrete beams and slabs are used to control fire resistance and acoustic performance, for example. The combination of different materials raises the issues of compatibility and aging due to various technological (such as cement hydrations) and environmental factors. The aging of wood has attracted a lot of research interest in both natural aging and accelerated aging studies. However, the fundamental understanding of aging mechanisms is still lacking. This work focuses on the aging mechanism of wood surfaces in thermal and cement alkaline conditions in the nanoscale using atomic force microscopy (AFM) and other analytical techniques.We proposed two sigmoidal curves (using Boltzmann sigmoid equation) to describe the change of adhesion forces and jump-off force ratios during the aging of wood cell walls. During thermal aging, the 1st sigmoidal curve of the adhesion force – jump-off force ratio relationship described the transportation of extractives and their oxidation on the surface. The 2nd sigmoidal curve suggested the degradation of the hemicellulose-lignin matrix and the exposure of the cellulose aggregates. This interpretation was independently proven by the cell wall topography before and after treatments, and chemical analysis with Fourier-transform infrared spectroscopy (FTIR), and Headspace GS-MS. During alkaline aging, the gradual shift of data points could also be described by the two sigmoidal curves.We measured the immediate and short-term degradation process of the wood cell wall surfaces from 0.5 h to several days quantitatively in thermal loading and cement alkaline environment. We described the progressive degradation from the dissolution of extractives, through the degradation of the hemicelluloses-lignin matrix, to the exposure of cellulose aggregates using the two sigmoidal curves in terms of jump-off force ratio and adhesion force. Measuring the changes in surface deformation and modulus of wood in cement alkaline aging revealed that the cement hydration heat significantly accelerated the aging process: The 1-h treatment at 50 ℃ (cement hydration temperature) caused a 20% decrease in the surface moduli similar to 144–624 h at 20 ℃; a 50% decrease of the surface modulus occurred after 264 h at 50 ℃ similar to after 1104 h at 20 ℃.

Juan Li, Bohumil Kasal
Leaching and Permeation of Chloride Ions from Seawater and Sea Sand Concrete

In this paper, the chloride leaching from seawater and sea sand concrete (SSC) to freshwater (static water and dynamic water) and the penetration of chloride into normal concrete (NC) were investigated. Meanwhile, the chloride permeation between SSC and NC was simulated by COMSOL software. The results show that chloride ions in SSC slowly migrated from the inside to the surface and form a surface enrichment phenomenon in the area of 0–5 mm when immersion in the freshwater environment. Increasing the concrete strength can delay the leaching of chloride ions and the total leaching amount were only 0.116–0.158 mg Cl/g concrete after 189 d. The leaching rate can be accelerated by changing the leach solution regularly, and the chloride ions leaching from concrete with volume of 1 dm3 was 50–85 mg each time. Chloride ions were first enriched at 2 mm on the surface of SSC and then partially penetrated into NC, and the penetration depth is 5 mm after combining for 90 d. The simulation results show that the relative humidity inside the concrete was the key parameter to determine the penetration rate of chloride ions, and the chloride penetration into NC was inhibited by its lower humidity.

Shicai Li, Zuquan Jin
Increasing the Shelf Life of Portland Cement

Strategies to counteract the negative effects of extended storage for cement generally fall into one of two categories: either pretreat the cement to prevent or interfere with prehydration, or introduce new admixtures during the mixing of concrete that can compensate for prehydration that has already occurred. This study focusses on the former, with alkyl ketene dimer (AKD) wax and AKD + paraffin wax additions that are introduced during clinker milling, to slow the prehydration of cement under moist storage conditions. AKD and AKD + paraffin additions are shown to function as effective grinding aids, and mortar strength and calorimetry tests demonstrate improved resistance to degradation of hydration reactions attributed to prehydration, based on accelerated aging exposure conditions of 37 ± 2 ℃ and 95–100% RH.

Alexander Ozersky, Alexander Khomyakov, Pengfei Zhao, Lucas Herzog Bromerchenkel, Oleksiy Chernoloz, Karl Peterson
Corrosion and Its Control in Prestressed Concrete Structures

Many prestressed concrete (PSC) structures have been built with an anticipated service life of 100+ years. However, many of them have experienced premature corrosion of strands and eventual tendon/girder/bridge failures within a few decades. Hence, reviewing earlier assumptions on corrosion properties used for durability-design purposes and developing methods to build PSC structures with “corrosion-free” service lives of 100+ years is important. For conventional and pretensioned concrete structures, the chloride threshold is a key service life parameter. It is the minimum amount of chlorides required to initiate corrosion of steel-cementitious (S-C) systems and no suitable test methods are available to determine this. This prevents engineers from choosing durable material-combinations to achieve the target service life of 100+ years. In this presentation, the development of a test method and determination of chloride threshold for various S-C systems with various binders, corrosion inhibitors and prestressing steel (i.e., 50% less than conventional steel!) will be presented. In case of post tensioned (PT) concrete structures, the presence of air voids (due to the inadequate grouting) has been cited as the major reason for corrosion of prestressed strands. Refilling of such voided tendons with new grout can lead to galvanic corrosion and is not recommended. Also, the replacement of corroded tendons is very expensive and cumbersome. Hence, a new non-invasive method to control the corrosion of strands in PT systems with voids has been developed using chemical treatments and cathodic protection techniques. These techniques that can save huge inventory of PT bridge tendons will also be presented.

Radhakrishna G. Pillai, Karthikeyan Manickam, Dyana Joseline, Sreelakshmi Srinivasan
Raman Imaging of Cementitious Systems

The chemical composition and mineralogy of heterogeneous materials are key to understanding their behavior and performance. Specifically, for construction materials such as aggregates and cements, elucidating the phase mineralogy at a fundamental scale is crucial for predicting their performance. Most investigations obtaining chemistry and mineralogy, have relied on methods such as NMR, X-Ray Diffraction, and electron and optical microscopy. These methods when combined provide much more information on the complex heterogenous materials, despite having certain limitations. Raman imaging is a complementary high-resolution imaging technique that allows direct fingerprinting of minerals, including their polymorphs. Here, using a newly developed analytical methodology, an accurate and rapid mapping protocol to quantify a variety of static heterogeneous systems such as cements, fly ashes, waste-to-energy ashes, and granites is reported. In addition, an application of this diverse technique to map cement paste carbonation, a dynamic phenomenon, is demonstrated. These results pave the way for future application of Raman imaging such as the design of sustainable materials and monitoring of concrete’s performance.

Krishna C. Polavaram, Chirayu Kothari, Andrew Christopher Witte, Sonali Srivastava, Sudharsan Rathna Kumar, Hamza Samouh, Nishant Garg
Valorization of Textile Waste in Laminated Fabric Reinforced Cementitious Matrix Plates: Tensile and Durability Characterization

A gradual transition of the linear economy towards a circular economy model, where recycling and reusing are the basis, has been widely encouraged in all sectors for guaranteeing a sustainable future. In this sense, the utilization of textile residues, largely-available waste with a high potentiality of reusing, as reinforcement in inorganic matrices could valorize waste recycling in construction industries. In the present study, cement-based composite panels reinforced with nonwoven fabric layers recovered from textile wastes, both end-of-life fashion and fire-protecting clothing, were investigated. The mechanical (through the uniaxial tensile test) and durability (through forced aging of wet-dry and freeze-thaw cycles) properties of the developed sandwich-like fabric cement boards were assessed. The results demonstrated promising tensile resistance (up to 7 MPa with strain capacity up to 8%) and fracture toughness (up to 50 kJ/m2) for the unaged panels, suitable for the projected applications such as façade cladding panels, pavement slabs, or internal panel walls. Regarding durability, although the post-cracking performance of both recycled textile composites (specifically those from fashion garments) in wet-dry conditions was degraded due to the fibers’ embrittlement, substituting partial Portland cement with silica fume (up to 30%) could enhance the behavior by 50%.

Payam Sadrolodabaee, Mònica Ardanuy, Albert de la Fuente, Josep Claramunt
Effect of Portland Cement Blending with Calcium Sulfoaluminate Belite Cement and Calcium Sulfate on Carbonation Resistance

Calcium sulfoaluminate belite cement (CSAB) is an environment-friendly alternative to portland cement (PC). CSAB cement has been shown to have up to a 30% reduction in carbon dioxide emissions. Carbonation is one of the significant factors that can cause durability concerns in the reinforced concrete system. Carbonation of a cementitious system reduces the pH, destabilizing the passive layer around reinforcing steel and causing corrosion. In CSAB system, the primary hydration products are ettringite, monosulfate and aluminium hydroxide. The CSAB system with additional gypsum will have ettringite as the major hydration product. The surplus gypsum will promote ettringite formation at the expense of monosulfate, limiting its capacity to bind carbon dioxide. The microstructure of PC system will also be influenced by blending it with CSA admixture or CSAB cement and gypsum. This study aims to evaluate the carbonation behaviour of two expansive binders: 1) blend of PC and expansive CSA admixture, and 2) blend of PC, non-expansive CSAB cement and gypsum. The specimens were exposed to a 3% concentration of CO2 at 65% relative humidity to accelerate the carbonation rate. Additionally, the pore structure and microstructure changes were monitored by characterising non-carbonated and carbonated samples. The results indicate that PC blended with CSAB cement and gypsum carbonated faster than PC blended with CSA admixture. The additional ettringite present in PC blended CSAB cement resulted in increased carbonation rate.

Paul Shaji, Piyush Chaunsali
Assessing Passivation and Corrosion of Post-tensioning Strand in Grouts Under Chloride Salt Exposure

This study examines the impact of different commercial grout pore solutions and varying concentrations of salts with different cations on the chemical composition of the passive layer and its breakdown process. X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization were used to study the passivation and corrosion behaviour of post-tension strands. The strands were passivated for 10 days in ex-situ leached pore solution from pastes made of ordinary portland cement (OPC) and other commercially available grouts, followed by exposure to 0.01 mol of chlorides per day in the form of NaCl, CaCl2, MgCl2, and KCl for the total duration of ten days. The study found that the passivated strands’ Fe 2p3/2 spectra generated from XPS testing included metallic iron (Fe), Fe cementite (Fe3C), a mixture of magnetite and wustite (Fe3O4/FeO), hematite, maghemite, and ferrihydrite (a-Fe2O3/c-Fe2O3/FeOOH), and the satellite structure of Fe2O3/FeOOH. The Nyquist and Bode plots of the EIS spectra showed a higher passivation capability of strands in commercially available grouts compared to OPC. However, potentiodynamic test results revealed that after adding chloride, samples that passivated in OPC pore solution had a higher critical chloride threshold, partially due to a higher pH of the pore solution in this system. The analysis of critical chloride threshold of strands exposed to various salts demonstrated that the cation of chloride salt can significantly affect the passive film breakdown, and the critical chloride threshold of strands changes in the increasing order of MgCl2 < NaCl < CaCl2 < KCl.

Mahmoud Shakouri, Ojo Friday Abraham, Naga Pavan Vaddey
Capturing Internal Swelling Reactions (ISR) Damage in Concrete Through the Damage Rating Index (DRI)

Concrete, building most of our infrastructure, is relied upon to provide safe and long-lasting uninterrupted flow of goods and services to the public. However, as deterioration in concrete may be a result of service lives coming to an end, in some cases, factors that were unknown at the time of construction accelerate the process. Such distress mechanisms include alkali-silica reaction (ASR), freezing and thawing (FT), and sulphate attack among which delayed ettringite formation (DEF) make up the three major internal swelling reactions (ISR) known to date. With the rise of more efficient concrete materials comes the lack of field performance for which there is a need to identify damage on its early onset. The damage rating index (DRI) is a microscopy tool currently used in North America to semi-quantify damage in concrete. The DRI combined with other tools such as mechanical/durability property loss, the stiffness damage test (SDT), and characterization of the reaction products can provide a full profile of the damage. This work therefore offers an overview of the DRI procedure and its adaptability to other distress mechanisms such as DEF at a representative scale while highlighting its accessibility worldwide due to its low cost and energy compared to other tools.

Cassandra Trottier, Leandro F. M. Sanchez, Renaud-Pierre Martin, François Toutlemonde
Effects on Hydration Reactions by Different Curing Temperatures for Various Types of Cement

Cement hardens by hydration reaction. However, it is noted that cement type and curing temperature have an effect on hydration reactions. It is important to understand the effects of materials of concrete and the conditions of the construction environment in order to design concrete that satisfies the required performance such as strength and durability. Therefore, in this study, cement pastes specimens were prepared using various types of cement, curing temperatures, and curing periods. We measured the amount of bound water and organized it according to the accumulated temperature, which is indicated by temperature and time. Then, the degree of hydration was quantitatively evaluated. In order to know the effect on strength and durability, mortar specimens were made by setting the curing period at each curing temperature to achieve the same level of hydration. And we conducted compressive strength test and accelerated carbonation tests. As a result, the effects of temperature on hydration reaction, strength, and mass transfer resistance were evaluated. It was found that a lower curing temperature had a greater effect on the progress of hydration when blast-furnace cement was used. Furthermore, the trend was more significant when the content of blast furnace slag fine powder was high.

Runa Yahiro, Takeshi Iyoda

Enhancing Infrastructure Resilience Through Innovative Materials in Rehabilitation

Cost Implications of Natural Disasters on Road and Bridges Infrastructure in the Philippines

In 2021, the Philippines’ total cost of damages caused by natural disasters exceeded 60 billion pesos or 1.1 billion USD. However, it is important to determine the financial costs incurred in each region as a result of road infrastructure damage caused by natural disasters to understand how the cost of damages differs between regions. This study used disaster-related data from the Philippines for the year 2021 to calculate the estimated cost of damages to road infrastructure resulting from different natural disasters. The results for the different regions of the Philippines were compared using the Kruskal Wallis test, and the Mann-Whitney U test was used as a post-hoc test to determine which regions had a similar median distribution of estimated costs of damages. In the analysis, it was concluded that not only the frequency of disasters experienced by the region but also the number of extreme damage events are key factors in estimating the damage suffered by the region. Understanding the cost of damages and how they differ between regions may help road infrastructure management agencies develop a strategy for mitigating the impacts of natural disasters.

Minie Joy Adarne, Michael Henry
Optimizing Bridge Rehabilitation: A Life Cycle Assessment and Cost Analysis of Conventional and UHPC Overlays

Bridge decks often face common issues such as concrete cracking, spalling, and deterioration. As a proactive approach to extend the bridge’s service life, necessary measures must be implemented on a preventive, cyclic, or condition-driven basis. Selecting the most suitable materials for rehabilitating bridge decks is a pressing concern in extending their lifespan, underscoring the need to assess the economic and environmental performance of various overlay options. Ultra-high-performance concrete (UHPC) is one of the innovative technologies for the prevention and repair of bridge infrastructure by the USA Federal Highway Administration. UHPC requires less maintenance than traditional materials due to its very high strength and low permeability to the aggressive environment, despite the higher investment costs that may limit its deployment. It further offers enhanced performance and improved life cycle cost over conventional methods. The implementation of preventive measures could reduce the frequency of condition-driven repairs and corresponding expenditure, leading to considerably lower carbon emissions. This study performs an integrated Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) to generate a parameterized model for the preventive maintenance of bridge deck rehabilitation, considering the lifespan of the bridge as the functional unit. Different bridge deck overlay formulations are compared with conventional concrete rehabilitation. An eco-efficiency analysis was conducted to assess the performance of alternative scenarios. It was observed that despite the high initial construction cost, UHPC does not require frequent maintenance, thus proving economically and environmentally viable. The study provides a methodology to have an optimal solution considering cost and environmental impacts without prioritization or subjective weighting.

Manisha Malik, Ben Amor
Sustainable Pervious Concrete for Urban Environment – Improvements and New Function

Urban heat island (UHI) effect refers to the overall tendency of increased temperature in urban landscapes compared to surrounding rural areas. This phenomenon is linked to anthropogenic heat (due to human activities) in the cities and a high heat storage capacity of urban construction materials. Also, it is reinforced by the air pollution linked to the traffic. In a context of rapid urbanization (leading to soil sealing, deterioration of ecosystems) and climate change with recurrent heat wave events, it is urgent to provide solutions to build more climate resilient cities. The first generation pervious concrete solution (which is initially a water management system that rapidly absorbs rainwater off streets, parking surfaces, driveways, and walkways) is the first answer to this equation. With feedback from several projects in multiple countries over the past 10 years, the major challenges in the deployment of this solution have been identified. They are mainly workability, robustness of formulation, freeze thaw resistance (in cold climate) and maintenance. The second generation of pervious concrete (using microfibers, stabilizer and air entrained technology) is able to solve the robustness and durability challenges. The combination of improved formulation and the use of activated charcoal (which acts as a filter, adsorbing pollutants such as nitrogen oxides and fine particulates) allows for the capture of pollutants more efficiently through the open porosity in pervious concrete. The pollution adsorption capacity of this solution has been proven through an open-air mock-up test.

Vibhu Malik, Adam Rudy, Quoc Huy Vu, Isabelle Javierre Bouchard, Isabelle Dubois-Brugger
Modular Design of Industrial Control Room with Steel and Aluminum Foam Materials Under Internal or External Blast Loads

Safety of personnel and heavy machinery is a key requirement in case of industrial facilities under accidental blast events. Moreover, selection of materials, structural systems, and construction practices for such infrastructure are required to support faster construction, without compromising safety though. Therefore, a case of modular design of an industrial control room has been presented in this work for blast-resistance. The control room is made of steel and aluminum foam composites fabricated and assembled suitably, along with pertinent connection details to serve the functional requirements. Subsequently, a detailed finite element (FE) model is developed for the structural assembly and exposed to internal or external blast loading scenarios, as applicable to the scenario-specific accidental blast events in typical industrial setups. The design of the modular control room, satisfying the functional requirements and specifications under the blast loadings has been accomplished satisfactorily. Particularly, the leakage of gas due to the blast-induced pressures has been checked under the distinct scenarios and the requirements thereof are duly satisfied. The modelling, analysis, design, and detailing strategies followed in the present work can therefore be suitably adopted in designing industrial facilities under the threat of blast-induced loading.

Harshada Sharma, S. P. Singh, Vasant Matsagar
Comparative Analysis of a Base-Isolated LNG Storage Tank Using Friction Pendulum Bearings and U-shaped Dampers

Base isolation is commonly employed to protect liquefied natural gas (LNG) storage tanks from earthquake damage. However, large deformation may occur to isolators under near-fault earthquakes, leading to risks of structural overturning, pipeline fracture and liquid leakage for LNG storage tanks. U-shaped dampers are highlighted as energy-dissipating devices used in combination with isolation bearings for high performance of base-isolated structures. This paper aims to investigate the effect of U-shaped dampers on a 160,000 m3 LNG storage tank isolated by friction pendulum bearings (FPB). A finite element (FE) model of the FPB equipped with U-shaped dampers was first established, which was validated by comparison with existing experimental results. Parametric analysis was performed on the isolation devices, including variables of damper thickness (i.e., 16, 30, and 42 mm) and material properties of the damper (LY160 steel and Q345 steel). Afterward, a refined FE model of the 160,000 m3 LNG storage tank was developed, and the effect of the isolation devices on the LNG storage tank subjected to near-fault earthquakes was investigated. Seismic responses of the tank, including acceleration of both the outer and inner tanks, hydrodynamic pressure of the inner tank, base shear and isolator displacements were extracted and analyzed. Results showed that for the 160,000 m3 LNG storage tank (isolated by 285 FPBs with a sliding radius of 3.0 m), it was recommended to employ the U-shaped dampers manufactured by LY160 steel with a thickness of 42 mm or the U-shaped dampers manufactured by Q345 steel with a thickness of 30 mm.

Jie-Ying Wu, Qian-Qian Yu, Xiang-Lin Gu

Smart Infrastructure Monitoring Techniques for Predictive Modeling

Statistical Analysis of Asphalt Pavement Distress Occurrence for Project-Level Maintenance Management of Provincial Highways

Understanding the various types of pavement distress that can affect asphaltic pavements is essential for effective project-level maintenance management. By identifying and analyzing different distress types and their probability of occurrence, road authorities can develop targeted maintenance strategies that address specific issues and prolong the lifespan of pavements while optimizing the maintenance budget. This study aimed to statistically model pavement distress using data from 240 km of provincial highways in Pakistan to understand the progression of crack development with pavement age for hilly and plain terrains. The analyzed distress data, taken in 200-m segments by field survey, include raveling, alligator cracking, potholes, rutting, edge cutting, block crack, patch failure, polished aggregate, slippage, transverse and longitudinal cracking. Logistic regression analysis was performed to determine the probability of occurrence of the various distress types up to six years after the last pavement rehabilitation in different terrain. The study found that rutting, raveling, alligator, and transverse cracking exhibited the highest probabilities of occurrence as compared to the other distress types, while block cracks, patch failure, and loss of pavements showed very slow deterioration over time.

Azam Amir, Michael Henry
Machine Learning-Based Deterioration Modeling of Highway Bridges Considering Climatic Conditions

Highway bridges are critical infrastructure systems that facilitate efficient and optimal vehicle flow along the transportation network. However, these assets are rapidly deteriorating because of their ubiquitous nature and insufficient maintenance programs. Climate change is expected to exacerbate this issue. Precise deterioration modelling is essential to maintain sustainable function of highway bridges. Research on condition assessment of highway bridges is increasingly being reported. Nonetheless, few models incorporated climate-based factors. This study aims to create a comprehensive, data-driven deterioration model for highway bridges that considers operational and climatic factors. The study utilized datasets from two main sources: the National Bridge Inventory (NBI) database and the Long-Term Pavement Performance (LTPP) dataset, both managed by the Federal Highway Administration (FHWA) in the USA. Data mining algorithms, feature engineering, and hyperparameter tuning techniques are exploited to calibrate the condition assessment model. The considered models include a k-nearest neighbor, decision tree, random forest, gradient-boosted trees, deep learning, and support vector machine. Evolutionary optimization is utilized to facilitate automated hyperparameter tuning. Several Performance metrics tests are employed to validate the practicality and accuracy of the developed models utilizing a new set of data that was never employed in the calibration process. The gradient-boosted trees model yielded the most promising results, with a mean relative error of 3.6%. In addition, the predictive importance of some climatic factors, especially the freezing index and mean temperature average was signified through the analysis. The developed model can assist transportation agencies in establishing optimal rehabilitation programs for highway bridges.

Ahmed Assad, Ahmed Bouferguene
Self-sensing Cementitious Composites for Monitoring Concrete Beams under Bending

An electrically conductive filler can be mixed into a cement-based matrix to create a self-sensing cementitious composites (SSCC). Carbon-based materials, such as graphene, carbon fiber, and carbon nanotubes (CNT), are the most commonly used fillers for this purpose. Concrete structures can be monitored through the changes in the SSCC electrical resistivity by taking advantage of its piezo-resistive behaviour. It has been proposed that the correlation between deformation and resistivity can be used as a calibration equation for the SSCC, which in turn, can be embedded in structural elements for monitoring. The purpose of this study was to develop a calibrated SSCC with CNT as conductive filler and apply it in the monitoring of a concrete beam subjected to cyclic bending. Cement, sand, CNT, and a viscosity modifying agent were combined to produce a SSCC that was molded in 4 cm side cubes with four copper electrodes inserted to measure its electrical resistivity. A Self-compacting concrete beam (10 × 10 × 40 cm) was molded with the cubic SSCC embedded in the compressed zone, cured for 28 days, and then submitted to cyclical four-point bending tests by increasing progressively the applied load until reaching the maximum flexural strength of the material. Strain gauges were installed on both the SSCC and the concrete beam. The effectiveness of the developed SSCC to monitor the concrete beam was demonstrated through the proportional response between the electrical resistivity of the SSCC and the mechanical load applied to the concrete beam. It was concluded that regardless of non-uniform deformations under bending, the compressed zone of concrete beams subject to bending may be effectively monitored by the SSCC.

Pedro de Almeida Carísio, Thaís Carvalho Dos Santos, Adriana Paiva de Souza Martins, Maria das Dores Macedo Paiva, Flavio Mamede Pereira Gomes, Oscar Aurelio Mendoza Reales, Romildo Dias Toledo Filho
Comparison of Decision Makers’ Perspectives and Data-Driven Factors Affecting Pavement Condition in Khyber Pakhtunkhwa, Pakistan

Best practices dictate that road maintenance plans be drawn up based on the pavement conditions determined by routine inspection. However, in many cases, the maintenance strategy is based on the experience of decision-makers, rather than the actual conditions. In Khyber Pakhtunkhwa Province, Pakistan, there are more than 3,000 km of provincial roads, but the road condition does not match the desired level due to the absence of an effective maintenance strategy. This paper aims to compare the pavement deterioration factors in the four divisions of highways as evaluated by decision makers with the factors exhibited by the actual inspection data to determine whether they follow a similar or different pattern. For this purpose, the factors that affect the pavement condition from the decision makers’ perspective were extracted from a questionnaire survey of division-level road managers by cross-tabulation analysis and were then compared with factors identified by ordinal logistic regression analysis of the pavement condition data obtained from the department. The study revealed that some factors that affected pavement condition like traffic loading that were common to both the decision makers’ perspectives and inspection data collected from the department in all divisions. However, there were some differences like drainage condition having a more significant effect on pavement condition in some divisions more than others, which suggested that it is important to analyze routine inspection data to give a more thorough and holistic approach to maintenance planning.

Selorm Dartey, Azam Amir, Michael Henry
Carbon Fibre Based Strain and Leakage Sensors for Sustainable TRC Infrastructures

Preventing damage over time contributes decisively to the sustainability over the lifespan of infrastructures. The development of smart protective measures to detect structural risks early is an urgent need in sustainable construction.Continuous carbon fibre rovings are suitable for use as reinforcing textile grids in concrete through their high modulus and alkali resistance. Additionally, their electrical conductivity allows for integration as sensors of strain change or leakage in concrete structures such as bridges and pipes. To realize a textile reinforcement for concrete structures various parameters like fibre material and orientation, grid opening, binding type and stitching length, textile dimensioning (2D, 3D) and coating are implicated. These affect not only the mechanical characteristics of the reinforcement but also the sensing properties of the carbon fibre rovings.This study delivers an overview on the use of carbon fibre based sensors in concrete structures and their characteristic changes as a function of different textile parameters.

Gözdem Dittel, Thomas Gries
Real-Time Monitoring of Concrete Properties Using an Embedded Smart Piezoelectric Sensor with Active and Passive Sensing Abilities

Concrete undergoes physical and chemical changes from the time of casting. These changes in early stage of hydration of concrete, highly influence the final properties and overall performance of concrete structures. Comprehensive health monitoring sensors can help to improve the quality and performance of concrete structures by providing detailed and accurate real-time information about the properties and condition of concrete at different stages of its life cycle. In this study, an embedded smart PZT (Lead Zirconate and Titanium) sensor is developed and its potential for comprehensive health monitoring of concrete structures is explored. To protect the PZT sensor from short-circuiting and alkaline environment, a robust and sensitive protection scheme is developed. The developed embedded smart PZT sensor was placed in the concrete during casting to infer the in-situ properties of concrete through active and passive sensing techniques. Through active sensing techniques Electrical Impedance (EI) and wave propagation (WP), the hydration and damage are monitored, respectively; through passive sensing techniques vibration, and acoustic emission (AE), the development of Young’s modulus and cracking in concrete are monitored. The methodology to infer the changes in workability, complete set behavior, property development, and crack opening in concrete structures is developed. The reproducibility of all these techniques using the developed embedded smart PZT sensor is established. Since the developed sensor is capable of both active and passive sensing, it allows for a more comprehensive and flexible approach to health monitoring. This contributes to increased data accuracy, reliability, and a more holistic understanding of the concrete structure’s condition.

Murali Duddi, Amarteja Kocherla, Kolluru V. L. Subramaniam
Structural Digital Twin of Concrete Infrastructure Powered with Physics-Informed Neural Networks

There are growing concerns for the remaining service life of concrete infrastructure under normal service conditions and the structural resilience under extreme climate events. Therefore, advanced and reliable computational tools are required for the assessment of existing structures’ condition, and the estimation of their serviceability. Traditionally, advanced structural simulations are conducted using nonlinear Finite Element Analysis (FEA) that exhibits major drawbacks hindering its application for large-scale simulations, particularly in real-time or nearly real-time. Those drawbacks include high computational time/power, convergence problems, and limitations in modelling the actual (than ideal or theoretical) condition of the structure and, more importantly, model updating as the structure deteriorates or undergoes changes. This paper proposes a closed-loop and computationally affordable cyber-physical solution for comprehensive structural health monitoring. The proposed approach is based on real-time prediction of the structural response for a concrete structure by creating, updating, validating, and maintaining a Structural Digital Twin founded on the framework of Physics-Informed Neural Networks (PINNs). PINN-powered structural digital twins present a novel simulation scheme that combines the physics-based models (represented by differential equations governing the structural behavior) with data-driven models (trained on the response data collected through sensors) into a robust computational model. The proposed method, implemented in a lab-scale case study, is presented in detail, and future areas of research will be discussed.

Soheil Heidarian Radbakhsh, Mazdak Nik-Bakht, Kamyab Zandi
Simulation-Based Transfer Learning for Concrete Strength Prediction

Data-driven techniques, such as machine learning, have shown their superiority in the design and development of concrete materials by accounting for their inherent complexity autonomously. Their wider adoption, however, has been hindered by the availability of large, reliable data and the model generalization performance to new data. In this paper, we propose a simulation-based transfer learning framework, where machine learning models are pre-trained on simulated results from physics-based models and then fine-tuned on target datasets. Compared with existing transfer learning approaches, the proposed method does not require real datasets for pre-training but instead takes advantage of prior domain knowledge embedded in existing physics-based models. The effectiveness of the proposed framework is investigated in the context of concrete compressive strength prediction. Results demonstrate that our framework enables desirable prediction accuracy, speeds up the learning process, and improves generalization ability to real-world data, even with a small amount of training samples. The proposed framework offers a practical solution to data scarcity in many scientific and engineering domains, where various physical models can be utilized as an additional knowledge source.

Zhanzhao Li, Te Pei, Weichao Ying, Wil V. Srubar III, Rui Zhang, Jinyoung Yoon, Hailong Ye, Ismaila Dabo, Aleksandra Radlińska
Use of Non-destructive Assessment Methods to Evaluate Condition of Carbon Fiber-Reinforced Concrete Pavement

The safety and comfort of those who utilize the roads will be impacted by the frequent pavement degradation. One of the main problems with road pavement that can accelerate its degradation is top-down cracking in the longitudinal wheel path. An effective technique to ascertain the characteristics of the existing road pavements and to detect any cracking and delamination is non-destructive testing. In this paper, the mechanical and durability characteristics of two concrete bus pavements—one reinforced with carbon fiber and the other with plain concrete—located in Victoria, Canada, were evaluated using the most up-to-date and efficient NDT techniques. To evaluate the surface and subsurface conditions of two concrete bus pavements, ground-penetrating radar (GPR) along with additional NDTs, including ultrasonic pulse velocity (UPV), Schmidt hammer (SH), infrared thermography (IR) and electrical resistivity (ER) have been used. The relationships between the NDTs and the impact of adding carbon fiber to concrete pavements were determined by a comparative analysis.

Maryam Monazami, Clinton Pereira, Rishi Gupta
Rebar Corrosion Monitoring in Concrete Using Piezoelectric Cement Sensors

In this study, the piezoelectric cement (PEC) sensor, a sensing element of lead zirconate titanate (PZT)/cement piezoelectric composites, was used to monitor rebar corrosion in concrete. The strength of the concrete was 21 MPa. A rebar was placed in the center of the concrete specimen. The piezoelectric cement sensor was attached to the concrete surface with epoxy resin to monitor rebar corrosion. An impressed current was applied to accelerate the rebar corrosion in concrete. The weight loss of the rebar was directly measured after removing the rusted parts in the acid solution. The results showed that the piezoelectric cement sensors, through the electromechanical impedance (EMI) technique, can monitor rebar corrosion in concrete. The conductance curve of the RC specimen monitored by the PEC sensor is smooth, and the applicable frequency is easy to identify. The frequency bandwidth for rebar corrosion monitoring is between 1000 and 2000 kHz. The broader bandwidth of the PEC sensor is beneficial for monitoring rebar corrosion. The regression analysis of the rebar’s weight loss rate (WL) and the sensor conductance root-mean-square deviation (GR) indicated that WL is linearly correlated with GR. This linear behavior allows the assessment of rebar corrosion when piezoelectric sensors are used for RC structure monitoring.

Huang Hsing Pan, Meng-Chen Ke, You-Shen Cheng, Hsin -Hsiang Hsu
Isafeguard: A Proactive Solution for Construction Job Site Safety Monitoring

Inherent hazards characterize the construction industry, and despite proper training and planning, accidents can still transpire during work. Furthermore, the manual monitoring processes traditionally employed are both time-consuming and costly. Safety managers often struggle with juggling diverse responsibilities beyond safety management, especially in large projects where there might be a shortage of personnel for effective on-site safety oversight. Thus, there is a necessity to integrate technological advancements that ensure real-time worker safety monitoring and alleviate the workload of on-site safety managers who oversee worker activities. The iSAFEGuard platform has been introduced to address this issue, incorporating cutting-edge technological monitoring innovations employing 127 unsafe scene detectors through Computer Vision (CV) technology. This platform has been developed to monitor and mitigate various risks, including falls, being caught in/between incidents, being struck by objects, electric shock occurrences, fires, etc. The advancement and application of techniques such as depth estimation, edge detection, and background subtraction in identifying these risks are discussed. Additionally, diverse applications of the iSAFEGuard platform on activities involving scaffolds, ladders, welding machinery, arrow saws, and others are explored. In conclusion, the iSAFEGuard platform presents an automated and technologically driven approach to safety management, enhancing the safety of construction workers and improving overall job site safety conditions.

Mehrtash Soltani, Akeem Pedro, Jaehun Yang, Syed Farhan Alam Zaidi, Doyeop Lee, Chansik Park
Corrosion Level Prediction with Acoustic Emission Sensing and Crack Measurements

The prediction of corrosion levels in reinforced concrete (RC) structures is crucial for damage assessment and ensuring safety. However, obtaining this information is challenging due to the complex nature of the corrosion process and difficulties encountered during on-site inspections. This research aims to develop a novel approach to determine the corrosion degree across corroded RC elements based on acoustic emission (AE) sensing and crack measurements.Data of multiple experimental programmes at KU Leuven have been combined in an elaborate data-set of six corroded beams, which all have been monitored by AE sensing and crack measurements. AE sensing continuously detects and localises elastic waves emitted by internal damage processes, providing information on the relative corrosion degree across a structure. However, several factors such as noise filtering, element size and wave velocity have a significant impact on the localisation process. Afterwards, targeted crack measurements can be performed on the area with highest AE activity. Crack measurements provide a straightforward technique for identifying visible damage and can be related to absolute corrosion levels through empirical relations. Since crack measurements are labour intensive and are limited to surfaced damage, and AE sensing can only assess damage in relative terms, the combination of both techniques offers significant benefits. When the influencing factors of the AE localisation are properly evaluated, results show that the predicted corrosion levels indeed match the actual mass losses of the rebars well, highlighting the potential of the combined AE and crack measurement technique as an efficient and accurate corrosion monitoring method.

Eline Vandecruys, Charlotte Van Steen, Constantijn Martens, Geert Lombaert, Els Verstrynge
Imputed Data Driven Prediction of Concrete Autogenous Shrinkage Based on Machine Learning Algorithms

The robustness of the prediction by machine learning (ML) highly depends on the quantity and quality of data used for training the ML algorithms. However, missing data of features in stored datasets from constructions in the field is rather common, which impairs the reliability of the predicted results. In this study, high-fidelity missing data imputation methods based on k-nearest neighbors (KNN) and multivariate imputation by chained equations (MICE) are proposed. Structured datasets of measured autogenous shrinkage (AS) data collected from different engineering projects are used for prediction. Random Forest (RF) and Extreme Gradient Boosted Decision Trees (XGBoost) integrated algorithms are selected to predict the AS with both imputed datasets and unimputed datasets. The results show that high-fidelity missing data imputation methods enhance the integrity of the structured datasets, and optimized XGBoost shows the highest prediction performance when the AS datasets are imputed using MICE. The prediction is also compared with the widely used ACI model. The validity of the ML prediction is therefore verified.

Xiaohang Xu, Yuanhao Dong, Zhangli Hu, Jiaping Liu
Smart & Sustainable Infrastructure: Building a Greener Tomorrow
Nemkumar Banthia
Salman Soleimani-Dashtaki
Sidney Mindess
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