Proceedings of the RILEM Spring Convention and Conference 2024

Aiming towards sustainability in the construction sector, various alternatives to cement-based materials have been proposed, with geopolymers being an excellent candidate due to their reduced carbon footprint as well as their exceptional mechanical and durability properties. With an increase in the need for external strengthening of structures, the use of textile-reinforced mortars (TRM) has been in the spotlight lately. This study aims to investigate such a strengthening system which uses alternative materials to cement-based matrices. The study focuses on the bond behaviour between textile-reinforced mortar using a binary geopolymer mortar as a matrix and a concrete substrate. A conventional TRM system employing a cement-based matrix was also investigated and used as a reference. The investigative parameters include the type of matrix (geopolymer or cement-based) and the bond length (50, 75, 100, 150 mm). For this purpose, a total of 8 twin specimens were prepared and tested by modified beam test. The results showed that specimens employing the geopolymer mortar achieved higher peak load than their cement-based counterparts regardless of the bond length by 25–94%, while also achieving higher vertical displacement by at least 14%. When geopolymer matrix was used the effective bond length was lower than the cement-based TRM although both systems exhibited the same failure mode.

Significant attention has been garnered to Textile Reinforced Concrete (TRC), a novel composite material comprising a cement-based matrix with high-performance textiles, due to its exceptional mechanical and durability properties. In response to environmental and economic challenges in constructions, this study focuses on enhancing the sustainability and economic efficiency of TRCs through development of innovative low carbon, low-cost concrete matrices utilizing composite cements. Ternary and quaternary blended cement mixes, incorporating Portland cement, ground granulated blast furnace slag, limestone, and/or silica fume, with 65% to 70% cement replacement levels, were developed. The concrete mixes developed in this study achieved optimal workability and compressive strength, resulting not only significantly reduced costs but also lower equivalent CO₂ emissions compared to TRC mixes of an equivalent strength class documented in the existing literature. Furthermore, the investigation explored the flexural performance of TRC composites, incorporating the developed concrete mixes and Alkali resistant-glass textile, revealing valuable insights into the material's response to bending forces.

Textile Reinforced Concrete (TRC) is now a key technology for the structural rehabilitation of deteriorated concrete structures, as well as for novel, versatile and highly customisable thin structures with optimised raw material utilisation. In order to fully exploit the excellent strength and modulus of high-performance fibres, like PBO, a uniform impregnation of the yarns is generally applied to achieve optimum stress transfer from the inorganic matrix to the load-bearing reinforcements. Mineral impregnation techniques for high-tenacity multifilament textiles are gaining increasing popularity over their polymeric counterparts mainly due to their enhanced thermal stability and good potential for reducing environmental impact. This paper presents and discusses the pull-out behaviour of PBO yarns embedded in a newly developed limestone calcined clay cement (LC3) mortar. Emphasis is placed on the bond properties of two grades of PBO fibres through pull-out tests. It is shown that the mineral impregnation plays a crucial role, not only in improving the mechanical response in terms of bond, but also in overcoming the differences in stiffness and properties of the PBO fibres, allowing the use lower grade fibres without compromising the overall performance of the composite.

The mechanical properties of cementitious composites subjected to carbonation curing depend on the carbonation degree, which is influenced by the diffusion of CO2 within the cementitious matrix. It has been found that due to the decrease in CO2 diffusivity as the curing progresses, the carbonation hardening is not uniform across the cross-section of the composite. The non-uniform carbonation of the cementitious matrix is expected to significantly influence the fiber-matrix interaction in fiber-reinforced composites (FRCs) subjected to carbonation curing. This study aims to understand the effects of carbonation curing regimes on the fiber-matrix interfacial properties. Single fiber pullout tests using polyvinyl alcohol (PVA) fibers embedded in reactive magnesia cement (MgO) matrix were conducted to determine the chemical bond, frictional bond, and slip hardening parameters. Three different curing conditions – 10% CO2, 0.5% CO2, and ambient curing (i.e., 0% CO2) were investigated. Results showed that the chemical bond between the fiber and matrix is higher when subjected to carbonation than ambient curing for oil-coated fiber, whereas non-coated fiber showed reduction in chemical bond when subjected to carbonation. The fiber-matrix frictional bond increased with the increase in CO2 concentration. The effect of CO2 concentration on slip hardening was negligible. These experimental results will aid in modifying the fiber-bridging analytical models to account for the non-uniform carbonate hardening of the cementitious matrix in FRCs.

Textile Reinforced Mortar (TRM) systems are currently among the most effective retrofitting solutions for masonry structures, thanks to their high compatibility with the substrate, and reversibility. Recently, the adoption of natural textiles as reinforcement in TRM systems has attracted the interest of researchers and industry, due to their great potential of providing a cost effective and sustainable solution while ensuring adequate structural performance. Despite the increasing number of studies focusing on the characterisation of short-term tensile properties, the long-term durability performance of natural TRMs, which is fundamental to ensure their viability in construction applications, has not been examined in detail. This paper aims to investigate the tensile behaviour of flax textiles and flax-TRM composites and assess their residual performance after exposure to accelerated ageing. Composites consisting of two and three layers of a bi-directional flax fabric embedded in a lime-based mortar were conditioned in water for 1000 h and 2000 h at controlled temperatures of 23 ℃ and 40 ℃. Bare textiles were also aged in an alkaline solution for equivalent exposure times and temperatures, to replicate the conditions within the lime-based matrix environment. Both unconditioned and aged textiles and composites were tested under uniaxial tension to determine their tensile behaviour. The complete load-deformation response was assessed employing both contact and non-contact methods (i.e. 2D Digital Image Correlation). It is shown that ageing strongly affects the textile reinforcement, resulting in a significant strength loss of the composite system.

Exposure to high temperatures, during fire events, can significantly affect the structural safety of existing buildings or infrastructures. Evaluating the effectiveness of retrofitting interventions or the repairability of damaged structures after fire is of fundamental importance to guarantee adequate structural reliability levels. The paper deals with the application potential of textile reinforced composites (TRC) (i.e. Textile reinforced mortar (TRM, Fabric Reinforced cementitious matrix (FRCM), etc.) both in retrofitting and repair techniques for heat damaged concrete elements. Some experimental tests, carried out on standard small scale concrete specimens, exposed to different temperature levels, are presented. The results show that: 1) thermal stress can significantly influences the behaviour of concrete retrofitted through TRC and 2) repair interventions through TRC were able to fully or partially restore the initial strength of the heat damaged material. Averall, textile reinforced composites showed a high potential to be applied in retrofitting and repair interventions of concrete elements damaged due to high temperature exposure.

This research presents preliminary results of the development of a lightweight, sustainable and fire-safe structural insulating panel by combining very lightweight aggregate concrete (VLWC) as a core and textile-reinforced cementitious composite (TRC) as skins. The potential disadvantage of this system using TRC compared to steel reinforced concrete may be its behaviour under fire. A VLWC, with expanded clay aggregates, was developed focusing on density and high temperature stability. This study investigates the behaviour of each of the constituent materials, TRC and VLWC and then of their combination in the sandwich structure at ambient temperature and cooled-down after being submitted to elevated temperature. The residual mechanical behavior of VLWC after heating up to 600 ℃ has proven to be as satisfactory as traditional concrete, if not better, particularly regarding tensile strength. The effect of high temperatures up to 600 ℃ on the tensile behaviour of TRC with coated-AR glass fibers was investigated. The first cracking stress and the ultimate tensile strength decrease with the temperature from 150 ℃. But the originally three-staged response (in ambient conditions) is maintained up to 300 ℃, and the ultimate strength is still significantly improved compared to the first cracking stress value. For the sandwich panels, no delamination from the skins appears. At ambient temperature, a similar three-stage behaviour is observed with satisfactory mechanical behaviour. Up to 300 ℃, the residual behaviour is similar, with a limited decrease in maximum loading. Yet, at this temperature, a few specimens undergone delamination during the heating phase.

Generally, it is known that the tensile strength of plain concrete decreases with the size of the element, which is attributed to the higher probability of having larger and more microstructural defects in larger elements or the effect of the propagation of the fracture process zone. There is limited information on the size and scale effects on the strength of strain-hardening cement based composites such as Textile Reinforced Concrete (TRC), which are beneficial for developing structural sections that are allowed to crack in a stable manner before failure. The size effect on tensile response of TRC is necessary for rational design and implementation of large-scale applications. In the current study, composite panels of different thickness (i.e., 10, 20, 40 mm) were fabricated using a cementitious matrix and coated E-glass textiles reinforcement; four layers of textile were used in all the panels. The specimens were monotonically loaded under direct tension in accordance with RILEM TC232. The specimens have shown a slight reduction in the first crack stress with increasing thickness, as can be explained based on statistical scale effects. Also, the overall tensile response transitions from strain-hardening to strain softening behaviour as specimen thickness increases. More interestingly, the number of cracks decreased with increasing size at any given strain. Further, DIC analyses reveal that the crack pattern and crack widths are significantly affected by the panel thickness.

Ultra High-Performance Concrete (UHPC) demonstrates superior mechanical properties and durability compared to ordinary concrete. The self-healing ability of UHPC has also been widely observed in numerous studies. Consequently, the development of a predictive model capable of forecasting the evolution of UHPC's self-healing performance under diverse exposure conditions has become crucial in order to reliably and effectively exploit this potential in the framework of a durability-based design of UHPC structural applications. In this study, an extensive dataset was collected and established through experimental tests focusing on the crack-sealing performance of UHPC. These tests simulated the conditions in which pre-cracked UHPC specimens were subjected to sustained tensile stress, while simultaneously exposed to exposure environments, including fresh water, salt water and geothermal water. Based on this dataset, a mathematical regression model was constructed, incorporating significant factors such as crack width, exposure environment, and exposure time for UHPC. The results demonstrate the remarkable accuracy of the proposed mathematical model in predicting the self-healing ability of UHPC.

Strategic structures can benefit from the characteristics of Ultra High-Performance Concretes (UHPC) to achieve long term durability without substantial maintenance. However, in some cases the aforesaid structures may still need to be dismantled. Thus, the possibility to recycle UHPC can significantly affect the environmental impacts associated with the use of this category of materials, given the high binder content and embodied energy. This study has investigated the self-healing performance of a UHPC made with recycled UHPC. Two different mixes were studied, with total replacement of sand and partial replacement of cement by recycled UHPC aggregates and recycled UHPC aggregates and fines respectively. The self-healing capacity of the mixes was addressed with mechanical and durability tests up to six months, with continuous exposure to a chloride-rich solution, simulating the marine environment. The unhydrated cement particles preserved the self-healing capacity of the parent UHPC. Both mixes proved their crack-sealing potential even with repeated damage-healing cycles, exhibiting a slight decrease only after six months of exposure and cracking. The crack closure resulted in a constant mechanical performance which was maintained over time.

The ingress of chloride ions in concrete induces the corrosion of reinforcement, leading to a degradation of the mechanical performance of the intended structural applications. The incorporation of crystallizing admixtures imparts autogenous healing to conventional concrete, enabling cracks to seal by themselves and thereby reducing the infiltration of chloride ions. Recognizing the inherent heterogeneity of plain concrete, this study formulates a mesoscopic numerical model in the framework of finite element method. The model conceptualizes concrete as a three component structure: coarse aggregate, mortar matrix, and interfacial transition zones (ITZs). To account for the influence of the self-healing phenomenon in concrete, two further phases representing cracks and damage zones (DZs) are introduced. The coarse aggregate phase is considered impermeable, with chloride ion diffusion assumed to occur in the remaining four phases. The self-healing process of cracks was simulated by using the moving mesh technique in COMSOL, with reference to the method of establishing the kinetic law of crack self-healing in the follow-up of Horizon 2020 ReSHEALience project, undertaken in the project MUSA, funded through the Italian National Resilience and Recover plan. Validated against experimental data, the model not only reproduces the crack closure process but also offers predictions on chloride transport. This simulation model contributes to the exploration of concrete resistance to chloride permeability, elucidates the transport mechanism of chloride ions within self-healing concrete, and provides insights for designing durable concrete structures to mitigate the corrosion of steel reinforcement or steel fibers.

Recently, we developed multifunctional bacterial-laden polymeric fibers (BioFibers) as an innovative delivery system to introduce a bio-self-healing capability into quasi-brittle composites. These BioFibers consist of a load-bearing core-fiber, a bio-compatible hydrogel sheath, and an outer protective damage-responsive shell layer, engineered to endow the matrix with three key functionalities: (i) bio-self-healing, (ii) control over crack growth, and (iii) damage-induced self-activation. This study focuses on evaluating BioFibers’ efficacy in filling cracks within a cementitious matrix. BioFiber-reinforced cement paste samples (BioFRC) were prepared, cracked under controlled flexural conditions, exposed to wet/dry cycles with bio-agent solutions, and monitored for the development of crack-filling efficiency over time. BioFRC specimens were prepared with a BioFiber reinforced zone. Controlled loading was applied to the specimens to induce cracks with the widths of 100–150 μm. Following crack initiation, samples underwent wet/dry cycles: 1 h submerged in a bio-agent solution (urea, yeast extract, and calcium acetate at 20 g/L each), followed by 23 h of dry conditions at 23 ± 1 ℃ for 28 days. Crack-healing efficiency was assessed at 0, 14, and 28-day intervals post-exposure. Moreover, self-healing end-product precipitations were collected from sacrificial samples for material characterization, including thermogravimetric analysis and scanning electron microscopy. Results indicated that precipitations from activated BioFibers achieved a crack-filling ratio of 93.7 ± 3.3% for cracks with an average width of 129 μm after 28 days of exposure. Material characterization tests revealed the formation of calcium carbonate crystals, including combinations of calcite and vaterite, in the healed samples.

This paper provides an overview of techniques for evaluating flexural fatigue life, delving into their applicability to ultra high-performance concrete (UHPC). The consensus on the impact of fibre inclusion on fatigue life of fibre-reinforced concrete (FRC) remains elusive. The intricate interplay of varied fibre parameters, loading frequency, and matrix composition complicates the understanding of FRC behaviour under cyclical loads. The absence of standardized test procedures hampers the correlation and extension of published results. Despite these challenges, a positive impact on fatigue performance under flexural loading is revealed, suggesting that fibres, under tensile forces, bridge cracks and extend fatigue life. This paper proposes a methodology to assess self-healing induced enhancement of the flexural fatigue life of UHPC in high-cycle fatigue loading, focusing on stiffness and the rate of crack opening displacement. Initially, specimens underwent 700,000 cycles as a fatigue pre-healing condition. Following the healing process, the specimens were subsequently subjected to up to 2 million cycles at a frequency of 5.5 Hz. UHPC specimens demonstrated up to 10% improvement in stiffness and a reduction of up to one order of magnitude in the rate of crack opening displacement with three months of healing in submerged condition.

Cement-based materials, vital in construction for their properties, face challenges due to crack formation compromising structural integrity. Thus, self-healing materials have been demonstrated to be crucial in extending structure lifespan and enhancing overall sustainability. More specifically, capsule-based healing, with the encapsulation of a targeted agent, relies on the choice of capsule core and shell material that can both influence the impact on the cementitious material as a whole, and the cracks closure. These systems, able to cope with different crack widths, may lead to improvements in terms of structure durability and a consequent reduction in the frequency of maintenance activities. Nevertheless, the production of microcapsules to be included in the concrete matrix encounters scaling challenges. However, membrane emulsification emerges as a potential solution, offering scalability and consistent product quality that could match industrial demand. In this framework, the present work investigates the environmental sustainability of the aforesaid technology through a Life Cycle Assessment (LCA) analysis. The study has been conducted using a cradle-to-gate system boundary to evaluate the environmental performance of the production process of the microcapsules, contributing valuable insights towards their impact on sustainability of self-healing cementitious systems.

Currently, there is a lot of focus on sustainability and circularity in the built environment to increase its durability. Some solutions, such as adding superabsorbent polymers to induce sealing and healing effects in cementitious materials, require the use of derivatives from the petroleum industry. Although these polymers are added in small amounts, they are environmentally unfriendly due to the carbon emissions associated with their fabrication. These polymers are used in the hygiene industry and often end up in waste landfills. However, they can be recycled and reused. This paper explores the use of recycled SAPs in cementitious materials and investigates whether they can achieve similar properties and characteristics, such as regaining impermeability and visual healing. The polymers are obtained by recycling diapers and hardened cement paste containing the polymers. Both virgin and recycled superabsorbent polymers showed reduced permeability compared to reference sample, with the virgin one performing slightly better than the others. The healing process was more visible in the specimens containing superabsorbent polymers compared to the reference samples, and the trends were consistent across all specimens. However, there was a minor decrease in the overall swelling properties of the recycled superabsorbent polymers. Both the commercial and recycled superabsorbent polymers yielded comparable results in terms of reduced compressive strength. The study demonstrates the potential of reusing superabsorbent polymers for more sustainable sealing and healing of cementitious materials. Future research will investigate the complete life cycle assessment associated with overall durability.

This paper presents a novel approach to characterize the direct tensile behavior of ultra-high performance fibre-reinforced concrete (UHPC), accounting for the complex relationships between the mix design constituents and the mechanical properties of UHPC. An artificial neural network (ANN)-based predictive model was developed to determine the mechanical properties of UHPFRC such as cracking stress, peak tensile strength, and the corresponding strain. Subsequently, this ANN-based tensile model for UHPFRC was integrated into a hybrid rotating crack model incorporated into an established nonlinear finite element analysis (NLFEA) software. In this formulation, suited for macro-modelling, the fibres are represented as smeared within the material. The proposed procedure was validated against UHPFRC specimens tested in the literature, including 5 membrane elements subjected to pure shear and (34) shear-critical beams. The simulated behaviours were in good agreement with the experimentally measured responses, with an $${R}^{2}$$ R 2 of 0.97 for all specimens. The model was then utilized to better understand the influence of the cross-sectional shape on the behavior of shear-critical UHPFRC beams. The analysis results facilitated the development of a simplified shape effect parameter that can be integrated into existing shear capacity prediction models for UHPFRC. The proposed shear capacity model showed reasonably accurate results in predicting the capacity of the beams with unconventional cross sections that were tested in the literature.

Applications of High-Performance Fibre-Reinforced Concrete (HPFRC) are gaining popularity both thanks to its enhanced mechanical performance and its capability of guaranteeing pleasant finishing that makes this type of materials a good solution for thin elements like façade panels. These kinds of elements are often subjected to cyclic loads throughout their service life. The impact of cyclic loads on material properties is significant and can potentially lead to fatigue failures, particularly in situations in which the elements have experienced cracks during their service life.The research presented here is oriented to studying the cyclic bending behaviour of thin-walled elements made of one specific HPFRC material, also considering different level of pre-cracking that refers both to serviceability limit state and to ultimate limit state condition.A set of four-point bending tests were performed on 35 mm thick samples applying a pulsating load with a cycle frequency of 1.3 Hz and considering different load range typical of the serviceability limit state. The pre-crack levels considered correspond to 0.5, 1.5 and 2.5 mm of global crack opening measured astride the constant bending moment region. The crack evolution has been measured during the proceeding of the cycles and, in the cases in which the samples did not experience failure before 100.000 cycles, a monotonic test was performed in order to compare the structural performance after cycles with that in pristine condition.

Integrating plant aggregate into building envelope insulation materials, such as hemp concrete, provides a promising approach to reducing the energy consumption and carbon footprint of buildings due to its excellent hygrothermal performances and low carbon footprint. Considered a highly hygroscopic material, hemp concrete exhibits susceptibility to hygrothermal solicitation. This characteristic causes dimensional variations (swelling/shrinkage) and consequently leads to damage in the material cracking especially at the interface zone. In addition, this material is highly heterogeneous and therefore requires better consideration of its behavior on a finer scale. The present study aims to improve the precise understanding of how temperature changes impact the morphological variations of hemp concrete. For this purpose, a specialized mini climatic chamber equipped with telecentric lenses, ultra-resolution cameras, and a precise temperature and humidity controller was designed to acquire a high-quality image of hemp concrete under heating-cooling cycles (15 ℃-50 ℃-15 ℃) with the constant relative humidity state. Next, the strain of the hemp concrete was visualized and quantified based on the 2D digital image correlation (DIC) technique. Particular attention was also devoted to the strain uncertainty. The results show that DIC is an accurate method for determining the local deformation characteristics (aggregate and interface) of hemp concrete. The acquired swelling/shrinkage percentage in hemp aggregate and interface zone inside hemp concrete could serve as input for numerical modeling of coupled hygro-thermal properties in the material.

One of the main weaknesses of alkali-activated materials is their higher drying shrinkage behavior compared to Portland cement-based construction materials. This limits their applications as repair materials, especially in composite action with OPC. In this study, an innovative approach to develop sprayed AAM exhibiting low drying shrinkage and no crack formation is presented. In order to develop proper spray formulation, fresh metakaolin-slag AAM is mixed with vegetable oil and reinforced with hemp and basalt fibers. The impact of oil and different fibers on various properties of the AAM composite is investigated experimentally: (i) workability, (ii) mechanical (compressive strength), (iii) porosity (low temperature nitrogen adsorption), (iv) drying shrinkage and (v) the crack formation due to constrained shrinking (analyzed on cylindrical disc specimens). Addition of oil does not degrade the properties of fresh mortars, but shows a beneficial effect on the shrinkage behavior by significantly reducing the porosity; especially of gel pores and small capillary pores below 20 nm of pore sizes. This led to reduced drying shrinkage rates by 25–30%. The addition of hemp and basalt fibers lead to changes in workability of the fresh mixtures, and a reduction in crack formation after 7 days of curing. By the combination of oil, fibers and air-entrainment agents the drying shrinkage related crack formation allowed the crack-free application of thin AAM layers on concrete substrates.

Ultra high performance concrete (UHPC) is a cementitious material containing a large percentage of cement, and 1–3% by volume of randomly distributed steel fibers. When UHPC is reinforced with longitudinal steel, R/UHPC members can develop significantly higher strength for a given cross-sectional area than traditional concrete members. Due to the compressive properties of UHPC, larger longitudinal reinforcement ratios than commonly used in reinforced concrete lead to more efficient use of both the UHPC and steel materials. The objective of this research is to explore various methods of providing shear capacity in R/UHPC beams subjected to high shear demand. Specifically, this study explored short-span R/UHPC beams where steel fiber content and longitudinal steel reinforcement ratio were held constant at 0.5% and 3.9%, respectively. Transverse steel spacing, transverse steel grade, and placement method were varied in seven small scale R/UHPC beams, which were experimentally tested to failure. Results indicated that traverse steel spacing had the greatest impact on specimen response. More transverse steel did not significantly increase load carrying capacity, however, it increased ultimate drift by 24%. Increasing the grade of the transverse steel did not significantly impact response, indicating that the shear force capacity within each transverse reinforcing bar was not a limiting factor to specimen performance. While some differences in fiber orientation within the R/UHPC beams were observed, the impact of placement method on beam response was negligible.

Ultra-high-performance steel fibre reinforced concrete (UHPSFRC) combines the benefits of ultra-high-performance concrete with the added reinforcement of steel fibres. The durability of UHPSFRC can contribute to sustainable construction practices. Its strength can lead to longer-lasting structures, reducing the need for frequent repairs or replacements. Using UHPSFRC poses the possibility of a decrease in Global Warming Potential (GWP) compared to normal-strength concrete per available m2 in residential and office buildings. Implementation of prestressing could reduce GWP even further. Deformations are often a problem when designing structures. From this came the idea of combining the two. In the present study 9 beams with the same reinforcement arrangement have been tested. Three were not prestressed, three were pre-tensioned, and the last three were post-tensioned. Cylinders and small beams were tested for reference parameters, strength, and fracture energy. The results of the tests are presented as load-displacement curves at several points along the beam axis and at the mid-point.A semi-analytical model governed by beam theory and the principle of virtual work is proposed. A software package developed in MATLAB allows for a wide range of possible beam cross-sections and non-linear material models. It is a proposal for a faster evaluation of the deflection behaviour of a concrete beam compared to i.e. FEM. The general idea of the methods is that a numerical iterative method can be utilised to investigate the member’s method, calibrate the parameters, and predict the response. The model assumes that individual beam cross-sections remain planar, equilibrium between internal and external forces and non-linear constitutive models for the materials, including a Fictitious Crack Model for UHPSFRC. The agreement between tests and the model is very good.The GWP is compared between a beam of normal-strength concrete (C40) and a pre-stressed UHPSFRC with the same performance parameters and shows a reduction in GWP of 20.7%.

A waffle-shaped UHPFRC deck slab has been designed and tested by running wheel fatigue tests to assess its fatigue resistance under traffic loading within the intended operational period. However, these tests did not result into destructive outcomes, and the specific failure mode remains undisclosed. Consequently, constitutive laws of the UHPFRC have been experimentally identified to elucidate the failure mechanism and the progression of damage in the UHPFRC deck slab by Non-Liner Finite Element Method (NLFEM) analysis. In this paper, various fatigue loading tests employing UHPFRC specimens were conducted to comprehend the evolution of the mechanical characteristics of the material under fatigue. The results indicated a reduction in the elastic modulus of the UHPFRC and an increase in displacement corresponding to an increase in the number of fatigue loading, thus signifying the potential for establishing these shifts of mechanical properties as governing parameters for fatigue dependent constitutive laws.

This work provides a succinct overview of recent advancements in wind turbine tower design and optimization. Recognizing the critical role of tower structures in enhancing the efficiency of wind energy harvesting, the review traces the historical evolution from traditional designs to modern tubular steel, concrete, and hybrid towers. A focus on taller towers highlights the significance of accessing higher wind speeds for optimal energy output. Materials science innovations, including the use of high-strength alloys and composites and of high-performance cement-based materials, are discussed for their role in achieving lighter yet robust and better constructable tower structures. In addition, new construction techniques are examined. Optimization methodologies, including computational modelling and machine learning, are examined, considering genetic algorithms, computational modelling, and simulation tools, coupled with machine learning algorithms. The paper concludes with a forward-looking perspective on future developments, anticipating progress in materials, construction techniques, and ongoing research initiatives. This concise review serves as a valuable resource for researchers, engineers, and industry stakeholders engaged in advancing wind turbine tower technologies.

With the advent of new concrete materials and advances in structural design, new thin structural elements are becoming increasingly popular. However, the lack of a standardized shear characterization process impedes full utilization of the inherent shear strength of these novel concrete mixes. This paper aims to address this by introducing a novel direct shear test for fibre reinforced concrete (FRC) that uses standardized samples and loading method. The shear behaviour of the cementitious matrix and FRC samples having different fibre dosages was thoroughly captured using the test. Furthermore, the new testing method can detect the effect of fibres on the shear strength, with samples with higher dosages exhibiting greater shear strength. Additionally, residual strength was found to depend on both the fibre dosage and type, with longer fibres exhibiting slightly better performance and higher ductility. This study contributes to the advancement of shear strength characterization in concrete and provides valuable information on the behaviour of fibre-reinforced concrete under shear loading, potentially facilitating the direct use of concrete shear strength in the design, especially for thin structural elements without conventional longitudinal and shear steel reinforcements.

Because the environmental impact of 3D printable mixtures by weight is often higher than traditional mixtures due to their high clinker content [1], the benefit of material savings through optimization and digital manufacturing may thus be annihilated by the difficulty to formulate printable mixes with low binder content [2]. This paper aims to develop a methodology for designing cementitious materials specifically tailored for large-scale 3D printing of mortar in bi-component printing systems. This method, developed and used in this study, focuses on the packing density of a dry mix because high packing density is one of the key factors for obtaining ultra-high-performance cementitious materials, but packing density also plays a role in the fresh state, influencing various properties of dense suspensions, including rheological properties and stability, which are highly important in 3D printing applications and can be related to the three steps of a 3D printing process: Pumpability, extrudability, buildability [3]. To compute the packing density of futures mixes, the Compressive Packing Model [4, 5] was used. With various sets of raw materials, four different mixes were formulated with this method: a high performance mortar, a PLC (Portland, Limestone, Cement), a low carbon PLC, and a LC3 (Limestone filer, Cement, Calcinated-Clay). These mixes were tested at small scale to validate their rheological properties, particularly the yield stress. Pumpability, extrudability and buildability were evaluated by utilizing these mixtures in different large-scale printing sessions. The compressive strengths of these mixtures is characterized, and the carbon intensity [6] of theses mix is be discussed.

The ‘DiNaBau’ project investigates the utilisation of renewable and locally available resources in sustainable construction education. The project focuses on integrating digital building models to provide students with an immersive learning experience that promotes a thorough understanding of sustainable building practices. The aim of the project is to use locally produced renewable raw materials and develop innovative solutions to reduce the negative environmental impact of construction processes. Advanced digital technologies will be utilised to create comprehensive building models that demonstrate the use of sustainable resources. These models will serve as dynamic teaching tools, allowing for comparisons of sustainable materials and building constructions. DiNaBau aims to prepare specialists for the fields of sustainability and digitalisation early on in their training. This is achieved by seamlessly integrating digital building models into university curricula, familiarising students from all disciplines with sustainable practices and cutting-edge technologies.

The utilization of industrial wastes and by-products is one of the strategies for lowering the carbon footprint of the cement and concrete industry to reach sustainable construction goals. The criteria for evaluating the utilization of any industrial waste or by-product material as a supplementary material in cement and concrete technology are primarily related to their impact on the mechanical and durability performance of the final product. On the other hand, some industrial wastes may also provide an added value, such as turning concrete into a magnetorheological material with rheological properties that can deliberately be altered by applying an external magnetic field during concreting operations. This study investigates the potential of fayalite slag (FS), the waste iron silicate slag from the copper industry, to create a more cost-effective and sustainable magnetorheological cementitious mixture. The magnetic properties, phase, and oxide compositions of the FS were determined by vibrating sample magnetometry (VSM) test, X-ray diffraction (XRD) analysis, and X-ray fluorescence (XRF) analysis, respectively. The FS was used as a responsive additive in a cementitious mixture at 10% by volume. The magnetorheological properties were assessed by an oscillatory rheometer equipped with a magnetorheological device that can provide a constant or variable magnetic field during the rheometry test. Test results showed that the FS possesses significant magnetic properties, and incorporating the FS allows for the creation of more sustainable and cost-effective cementitious mixtures with magnetorheological properties that can be beneficial in pumping and 3D printing operations with smart control.

3D concrete printing is an innovative new construction technology offering the potential to enable the efficient production of individual structures with less consumption of resources. The technology will mainly shape the future construction philosophy. From the design of a structure to the printed component, many individual steps based on different software are required, which must be repeated for each new or even slightly changed design. The geometry of the structure is created in a CAD program. The print path is defined in slicer software leading to the machine code for the printer to print the structure. A numerical model of the printed structure makes optimization in design and fabrication possible, by predicting the behaviour of the structure and reducing the number of test prints and costs. For that, additional steps like meshing the design and running a simulation are required. In order to work efficiently, an automated workflow is necessary, which runs all of the individual steps without interacting with each software program. Furthermore, changes in parameters or the exchange of parts (different designs or printers) must be simple. One way to develop such an automated workflow is presented within this paper. The interfaces are defined in a way that allows running the full chain of tools as well as individual steps. The workflow is demonstrated based on the example of a parametrized wall element for extrusion-based concrete. Furthermore, a test series of cubes is printed, and the influence of different infill structures is numerically and experimentally compared.

This paper presents a comprehensive investigation into the rheological behaviour and pumpability of a mortar designed for 3D printing, incorporating fine recycled aggregates (recycled sand) sourced from construction and demolition waste. The research addresses the growing demand for sustainable construction materials by exploring the viability of recycled sand in 3D mortar printing applications. The study aims to modify a highly thixotropic reference mortar for 3D printing by substituting natural sand with recycled sand. Various aggregate-to-binder (a/b) ratios are used to assess their influence on the mortar's rheological properties and pumpability. The methodology extensively employs rheological oscillatory tests conducted with an Anton Paar MCR102e rheometer to obtain the storage modulus (G’) and loss modulus (G”) evolution over time for each mixture. Additionally, oscillatory step tests are conducted to measure the degree of thixotropy exhibited by the mixtures. The findings of the Sliding Pipe Rheometer (SLIPER) are instrumental in characterizing the slip layer's rheological properties, providing essential insights into the pumpability of the mortar.

Recent 3D concrete printing technology advancements have rapidly progressed in the construction industry. To meet the layer-by-layer stacking requirements, there is a need to develop high-performance cement-based composites compatible with 3D printers. Using fly ash as a substitute for cement reduces the environmental impact of 3D-printed traditional concrete mixes involving ordinary Portland cement (OPC). This study aims to determine the feasibility of adapting high-volume fly ash (HVFA) mortar to 3D printing by modifying the rheology of the mix with mineral additives. Three different additives were used to achieve this goal: sepiolite, slaked lime, and unslaked lime. The mix design includes 70% fly ash by weight and 5% slaked or unslaked lime by the weight of the binder. Additionally, 0.3% of the binder weight of sepiolite was added as a rheological modifier. Rheological parameters were assessed, including time-dependent evolution of yield stress, viscosity, thixotropy, and structural build-up with resting time. A preliminary printability and shape retention assessment of printed samples was conducted using a lab-scale robotic arm with a pipe as an extruder. Experimental results indicated that adding either slaked or sepiolite increased the static yield stress, dynamic yield stress, and thixotropy. The results show that the rheology of HVFA can be improved by using lime and sepiolite, and the quaternary mix design can be an alternative sustainable solution in the 3D printing of building materials.

This work focuses on Artificial Intelligence (AI)-driven materials design, addressing the challenge of improving the sustainability of building materials amid complex formulations. These formulations involve various components, such as binders, additives, and recycled aggregates, necessitating a balance between environmental impact and performance. Traditional experimental methods often fall short in managing the complexity of material composition, hindering fast enough development of optimal solutions. Our research explores complex composition materials design through a comprehensive, comparative lab study between Data-Driven Design, using SLAMD - an open-source AI materials design tool, and traditional Design of Experiments (DOE). We aimed to develop a high-performance, alkali-activated material using secondary precursors, aiming for a compressive strength exceeding 100 MPa after 7-days. The findings reveal that AI-driven design outperforms DOE in development speed and material quality, successfully identifying multiple high-performance materials. This result showcases AI's capability to handle complex designs with limited data, marking a significant improvement over conventional methods and demonstrating AI's revolutionary role in sustainable material design. Our study provides in-depth insights into the real-world application of data-driven design in a laboratory setting, highlighting the effective collaboration between AI-guided design and expert oversight. By showcasing the successful integration of AI, this research contributes to advancing sustainable materials science. It sets the stage for shorter time-to-market development boosting the impact of sustainable building in the construction industry.

We introduce the REINCARNATE project, funded by the European Union's Horizon Europe program, to boost circularity by merging digital innovations with practical applications and a focus on material reuse. The heart of REINCARNATE is the Circular Potential Information Model (CP-IM), a digital platform designed to assess and enhance the recyclability of construction materials, construction products, and buildings. The CP-IM integrates advanced technologies such as digital twins, AI, and robotics to revolutionize the handling of construction waste, turning it into valuable resources and cutting the environmental footprint of the sector. Among its features are digital tracing, material durability predictions, and CO2 reduction materials design. These are showcased in eleven European demonstration projects, highlighting the practical benefits of these technologies in reducing construction waste and CO2 emissions by up to 80% and 70% respectively. REINCARNATE aims to marry innovation with real-world application, providing the construction industry with strategies for sustainable and circular practices.

The rise in renewable energy usage has led to an increased focus on the recycling of wind turbine blades at the end of service life, due to a significant waste concern associated to their significant quantities. These blades, primarily composed of Glass Fiber Reinforced Polymer (GFRP), present a recycling challenge, as their material composition and potential secondary life applications are not widely established. This study aims to assess the efficacy of using recycled fibres from these blades into cementitious mortars, while also evaluating the environmental performance of giving these turbine blades a second life. A novel procedure is proposed for the segmentation and grinding of the blades into fibrous mixtures with known dimensional distributions. Various mixes for the mortars were prepared and tested, incorporating different percentages of recycled fibres. Alongside this, a sustainability assessment was conducted, analysing several recycling scenarios to evaluate their environmental impact. The findings indicate that the effectiveness of recycled fibres in enhancing the properties of mortars is promising only in certain compositions and production scenarios. The results suggest that the environmental benefits of recycling wind turbine blades into construction materials are contingent on specific factors, such as transportation scenarios and energy supply for processing recycled fibers.

3D-printed concrete is a groundbreaking innovation in construction, aiming to reduce environmental impact and speed up building processes. While current research is primarily focusing on material properties and their adaptability to the printing process, it is imperative to also consider the structural implications, particularly in challenging environment. Diverging from traditional concrete construction methods that involve formwork, compaction, and curing, 3D-printed concrete introduces a paradigm shift characterized by increased overall porosity and reduced reinforcement cover thickness. Although these distinctive features expedite the construction phase, there are concerns about the potential acceleration of corrosion in steel reinforcements. To enhance the durability of 3D-printed concrete, there is consideration for directly integrating corrosion inhibitors into the “ink” mixture. However, this proposition requires meticulous evaluation of the admixture dosage, since an imbalanced formulation could alter the specific characteristics of the initial mix, potentially compromising the material's printability. Predicting how rheological parameters will respond to selected materials and dosages poses a significant challenge. The work starts with an experimental preliminary characterization of rheological properties (via a flow table test) of 3D-printable mixes, sourced from existing literature, and incorporates the effects of corrosion inhibitors. This methodology is proposed as an alternative to using a rheometer, simplifying the entire procedure and facilitating streamlined on-site evaluations of material characteristics. Through this comprehensive analysis, the objective is not only to leverage the advantages of this cutting-edge technology but also to address potential challenges, paving the way for a more sustainable and efficient future in the construction industry.

3D concrete printing is a new and pioneering construction method that involves fabricating an element by depositing concrete layers according to a predetermined virtual model. This technology allows for faster construction and fabrication of customizable and complex shapes. In this study, a 3D printable concrete mix was developed using Portland cement and fly ash (80:20 by mass) as the binder. The rheology of the mixtures (yield stress and plastic viscosity) was characterized by performing flow curve experiments using a dynamic shear rheometer. To assess the buildability of the mix, a three-layer filament of 300 mm length was printed using a circular nozzle of 20 mm diameter. A digital camera was also used to record the print experiment, and subsequently, the deformation of each layer was determined using image analysis. Finally, using the measured rheological parameters, a fluid-based FEM numerical model was adopted to simulate the printing process. The filament shapes obtained from the simulation were compared to those obtained from the actual print experiment. Both numerical simulation and image analysis indicated that the layer deformation is evident. The results from the numerical simulations agreed well with the experimental results.

Steel fibre reinforced concrete (SFRC) offers a promising alternative to conventional steel reinforcement when constructing railway tunnel linings due to its remarkable strength and excellent fire resistance. Nevertheless, a crucial inquiry persists: could steel fibres potentially facilitate the conduction and transmission of stray currents, resulting in corrosion similar to that observed in conventional steel reinforcement? To address this concern, instrumental methods in electrochemistry, including potentiodynamic polarization techniques, have been used to assess SFRC’s corrosion resistance. Experimental results highlight the inherent resistance of concrete reinforced with discrete and discontinuous steel fibres to corrosion induced by railway stray currents. However, it is worth noting that the presence of even a small quantity of NaCl, specifically 0.3 mol/L in the concrete pore solution, can significantly diminish its corrosion resistance.

Sustainable construction of concrete structures in corrosive environments requires responsible use of locally available materials to extend services life, reduce cradle to grave carbon footprint impact, and to make these structures economical. Conservatism in setting limits for allowable chlorides in new concrete is needed to promote extended service life; however, refinement of industry approaches and standards towards protection against excessive conservatism is also important so that maximum flexibility and use of mixture supplements can be used to optimize reduction in carbon footprint and costs in construction. ACI Committee 222, Corrosion of Metals in Concrete, has recently revised the Guide to Protection of Metals in Concrete Against Corrosion. Due to the significant impact to the industry, considerable variation in existing approaches and serious consequences of corrosion, the committee has also recently promoted initiatives associated with refining chloride limit recommendations for new construction and chloride threshold testing. This includes a recent Special Publication on chloride limits, revision of recommendations in the new guide, formation of a special Task Group, and sponsorship/oversight of ACI’s Concrete Research Council (CRC) funded research for a collaborative study for the development of a standard critical chloride threshold test method. This paper will discuss some of the key updates to the Guide Document, as well as recent initiatives associated with chloride limits and thresholds. Information will be provided on the results of the CRC-funded research sponsored by the committee for a new test method for quantifying chloride limits. It will also discuss the reasons why these issues have been identified as important, impacts to the industry, and future needs.

Chloride-induced depassivation of steel reinforcement is one of the key durability issues for concrete structures. Conventionally prediction of service life using a probabilistic approach for chloride-induced depassivation relies on semi-empirical engineering models like the fib chloride model. However, such models use parameters such as the aging coefficient which are difficult to define in practice and introduce additional uncertainties that makes such models difficult to apply for realistic service life prediction. This study offers a new approach, employing a physics-based reactive transport numerical model in a probabilistic manner. The reactive transport model considers chemical and physical interactions within the concrete structure. Based on experimental data, a new binding isotherm for Portland cement paste is presented and used in the reactive transport numerical model. To demonstrate this approach, a case study compares the predictions made by the reactive transport model with those from the conventional fib chloride model. The reactive transport model predicts the chloride ingress after 6 years with less uncertainty compared to the fib chloride model. It also predicts the highest probability of depassivation after 50 years. Additionally, this study explores the impact of introduced uncertainties, given their substantial effect on the prediction results.

Heating and cooling systems are a major contributor to global energy consumption and CO2 emissions in the construction industry. In case of restoration of historical buildings, a possible solution to mitigate this problem is to incorporate thermal energy storage systems, like phase change materials (PCMs), into restoration mortars. PCMs, like poly-ethylene glycol (PEG), can be incorporated in lime-based mortars as bi-phased smart aggregates. These aggregates consist of a porous inert matrix, for instance small flakes of Lecce Stone, containing the active PEG phase [1]. Although mortars with PCM show favourable thermal properties, nevertheless they present a reduction in their mechanical resistance possibly due to: (i) a lack of compatibility between aggregate and binder; (ii) a lack of confinement of the PEG polymer in the stone, causing its dispersion in the mortar. Therefore, the aim of this study was to investigate the causes of the observed reductions in mechanical properties and to propose a method to prevent this occurrence. The results showed that the dispersion of PEG-1000 within the binder is apparently the main reason behind the reduction of the mechanical properties. Micro-FTIR compositional mapping evidenced that the lack of confinement of the PEG-1000 in the inert aggregates results in its dispersion inside the mortar; mechanical tests showed that the binder’s mechanical resistance is reduced in the presence of PEG. To prevent PEG dispersion, a simple coating procedure of the smart aggregates was successfully implemented. The improved confinement of the PEG-1000 in the inert aggregates produced a reduction of the internal cracks and pores of the mortar.

Concrete is responsible for 8–10% of total anthropogenic CO2 emissions, with cement production accounting for over 60% of this contribution. Considering this environmental impact, the integration of sustainable and alternative materials as replacements for cement represents a promising strategy for emission reduction. Alkali-activated materials and/or geopolymers can be used as an alternative construction material and are formed by activating aluminosilicates such as fly ash, granulated blast furnace slag, and/or clays with alkaline solutions. The selection of precursors for geopolymer synthesis is strictly related to their local availability. Among these, activated clays have gained considerable attention, offering great potential for geopolymer production due to their widespread availability and composition. Albania has a great potential due to the weathering conditions, but very limited information is available. In this preliminary study case, different clays were collected from different areas across Albania and investigated for their reactivity and suitability as precursors for geopolymers after thermal treatment. These clays were subject to characterization, and their reactivity was assessed according to R3-bound water methods. Calcination of clays was performed at temperatures of 650 and 750 ℃ for 1 h. The results indicated that calcined clays from Albania can have potential to be suitable source materials in geopolymerization reactions and/or as supplementary cementitious materials.

Ordinary Portland cement (OPC) is a ubiquitous construction material and has long been the most prevalent of all man-made concepts. However, the massive demand for OPC is responsible for approximately 7–8% of all anthropogenic CO2 emissions. Substituting OPC with industrial by-products presents a promising avenue for reducing clinker usage and aiding industry decarbonization. However, concerns arise regarding the presence of trace metals, particularly Pb, which can impede early hydration and degrade material properties. Understanding the kinetics of clinker phase dissolution in the presence of Pb is crucial for mitigating these issues. Conventional characterization methods may alter samples and fail to adequately capture underlying reaction mechanisms. To address this challenge, our study employs in-situ X-ray diffraction (XRD) to accurately assess Pb-OPC hydration kinetics in real time. Furthermore, we develop a geochemical model to quantify hydration reactions. This model supplements experimental findings, providing valuable insights into the proposed mechanisms. Overall, our work enhances the understanding of Pb-OPC interactions in cementitious materials, ultimately contributing to more efficient industrial by-product management and sustainable construction practices.

The present work evaluates the performance of concrete, after four (4) years of placement in slabs on ground in Guatemala City, produced with the first LC3 [1, 2] Limestone-Calcined Clay cement in Guatemala, compared with concrete produced with a High Early Strength Portland Pozzolanic cement, commonly used in Ready Mix applications in the country. Three different concretes were evaluated: 1 with Portland Pozzolanic Cement (cement content of 292 kg/m3), 2 with LC3 (cement content of 292 kg/m3), and 3 with LC3 (cement content of 352 kg/m3). As expected, the Portland Pozzolanic cement concrete and the LC3 cement concrete with higher cement content, present much better compressive strength than the LC3 cement concrete with 292 kg/m3 cement content, especially at early ages. In durability tests, both concretes with LC3 cement present higher carbonation depth than the Portland Pozzolanic cement concrete. Nevertheless, both concretes with LC3 have a superior performance in resistance to chloride ion penetration. It is noted, that on a long-term basis, the Portland Pozzolanic Cement concrete improved considerably on this particular test, due to pozzolanic reaction. Although more tests are needed on concretes with LC3 cements, for the moment, and with the humidity conditions prevailing in Guatemala City, which are moderate, around 70%, and very prone to carbonation, it is recommended to continue to use concretes with Portland Pozzolanic cement. On the other hand, due to the good performance of concrete with LC3 cement on the chloride ion penetration test, this cement is recommended in high humidity environments, where carbonation is not an issue.

MgO/hydromagnesite blends have emerged as promising low-carbon alternatives to conventional building materials based on Portland cement. Despite recent advancements in the characterisation and modelling of Mg-bearing phases in this type of binder, the durability of building products, i.e. mortar and concrete, has received comparatively little attention. This study investigates the ability of MgO/hydromagnesite binders to resist chloride and moisture ingress and to protect embedded steel from corrosion. A combination of chloride-resistance, impedance and linear polarisation resistance measurements is used. Irrespective of the curing conditions, 90/10 mass-% MgO/hydromagnesite mortars feature a low chloride diffusion coefficient of $$D=\left(0.6\pm 0.3\right)\times {10}^{-12}$$ D = 0.6 ± 0.3 × 10 - 12 m2/s. Single frequency impedance measurements between stainless steel bars embedded in mortar prisms suggest that the mortars are resistant to the ingress of water, prospectively due to their dense microstructure. Embedded carbon steel bars exposed to the ingress of water and concentrated chloride-containing solutions experience low corrosion current densities in the order of 10–7 to 10–8 A/cm2, similar to the corrosion rate of passive steel in concrete. Even though the pore solution in the MgO/hydromagnesite binder is buffered at significantly lower pH (10.5–11.0) than the aqueous phase in equilibrium with portlandite in Portland cement, the novel binder could thus be used for reinforced cement products. Further testing is needed to assess the long-term stability as well as the corrosion rate of steels embedded in MgO/hydromagnesite building materials under the simultaneous ingress of moisture and CO2.

Strategies to reduce the environmental impact of the concrete industry include enhancing the CO2 sequestration using the material as a durable carbon sink. At this aim, early-age carbon curing has been proposed and seems to be a promising method for CO2 sequestration. However, studies on this treatment are still limited and do not allow to clearly evaluate its environmental benefits and its effects on concrete properties. In this work, both moist and carbon curing treatments were performed on concretes made with natural aggregate (Ref) and recycled concrete aggregate (RCA). In particular, concretes were either moist cured for 7, 14 and 28 days or carbon cured for 7 and 14 days. In addition, combined curing was also tested, performing carbon curing for 7 and 14 days, followed by moist curing up to a total of 28 days. After the different curing times, compressive strength, modulus of elasticity and resistivity were measured, together with the carbonation depth by means of phenolphthalein test. At all the curing times the use of RCA in partial replacement of natural aggregate led to a slight worsening of the mechanical properties. The carbonation treatment both in Ref and RCA concretes allowed to permanently store the CO2 guarantying comparable performances. Moreover, the combined curing had a beneficial effect in partially restoring the alkalinity of the cement paste.

Phase change materials (PCMs) are among the most promising candidates for thermal energy storage (TES) applications. However, their low thermal conductivity and slow phase change phenomena are major restricting factors for efficient TES applications. This work investigates a novel thermal energy storage aggregate (TSA) composite based on butyl stearate (BS), a low-cost, commercially available, supported by graphene nanoparticles (GN) as high conductive agents stabilized in the porous media of expanded clay (EC) aggregates. Based on GN's high thermal conductivity, adding 2% GN in the composite shows enhanced heat transfer, while the composite TSA containing 2% GN, compared to plain EC, decreases the maximum temperature peaks up to 5 ℃ in heating cycles. Furthermore, the leakage test demonstrates that the developed TSA exhibits excellent thermal stability, indicating the potential to maintain its thermal performance even after multiple thermal cycles. Finally, the thermal performance of a TES concrete (TSC) containing TSA with 3.5% PCM-2GN by weight of TSC decreased the peak ambient temperature fluctuations up to 3.5 ℃ for a test in complete insulation condition. This reduction on TSC surface was between 9 ℃ to 10.8 ℃ in 1D heat transfer condition with 0% and 50% humidity, respectively. The novel-designed TSA composites pave the way for a practical and effective solution to enhance internal building comfort and energy efficiency.

Concrete is the most widely used man-made material in the world. Globally, millions of tons of drinkable water are used each year in the production of concrete and its derivatives. Considering the regional and global water shortages in recent years, it is considered that this consumption should be restricted urgently. Seawater is considered one of the alternative mixing waters that could be used as a substitute for fresh water. The interest in this subject has increased in recent years and the number of research projects on the use of seawater as the mixing water for concrete considerably increased. Most of the publications deal with the mechanical performance and microstructure of seawater concrete. Although there is consensus among researchers on some of the obtained results, there are many points where contradictory results have been reported. In this study, the effects of different mixing waters, ion concentrations, and metakaolin substitution on the performance and hydration kinetics of cement-based materials were investigated. The results showed that the dissolution of binder ions improved with higher ion concentrations. In addition, the synergistic effect of metakaolin and seawater maximized the performance and hydration kinetics of the material.

Comprehensive understanding of the processes of chloride ingress and carbonation, particularly their combined effects, is imperative to find prevention strategies. In this study, 3 mortar samples (CEMI+ground granulated blast furnace slag) were exposed to three alternating 14 day cycles in a 3% NaCl solution and a carbonation chamber (3 vol% CO2, 65% RH). After each cycle one sample was taken out for analysis. The water- and the acid-soluble chloride content was determined in powdered samples using a novel optical chloride sensor and via titration (reference method). The pH determination and assessment of the carbonation progress was done via optical pH imaging together with phenolphthalein coloration, as reference method. The results revealed a relatively constant carbonation rate ranging between 0.6 and 0.7 mm/√d. The pH imaging visually depicted the carbonation progress with depth and provided pH profiles in the pH range of 7.0–12. The chloride content decreased in the carbonated zone and the region with the highest chloride concentration shifted inwards. The results show a good correlation of the new optical sensors with the reference methods. Notably, optical pH imaging provides more insights into the pH variations over time compared to the phenolphthalein method. This investigation contributes towards advancing our comprehension of corrosion processes, particularly in the context of combined attacks involving carbonation and chloride ingress. The robust correlation observed between optical sensors and established methods highlights the potential of optical sensing technologies in enhancing our ability to monitor and understand corrosion phenomena in concrete structures.

In the quest to combat climate change, the construction industry, heavily reliant on cement-based materials, faces scrutiny due to significant CO2 emissions, mainly from clinker production. To address this, there's a need to strategically reduce clinker content in cement. However, these new formulations must meet the same requirements as the original ones, so their durability must be investigated. In this study, we determined material parameters that enable an assessment of moisture and ion transport. These methods offer advantages over conventional approaches, including non-destructiveness, reduced measurement time, simplified setup, enhanced resolution, and improvement of detection limits. Our investigation utilizes NDT techniques, using 1H NMR relaxometry for moisture transport and LIBS for ion transport in various clinker-reduced materials. The NMR tomograph provides spatial insights into internal moisture transport, correlated with weight change assessments for the capillary transport coefficient. Additionally, based on NMR relaxometry data the chloride diffusion coefficient is estimated. Chloride migration tests are performed, and results are evaluated using LIBS and indicator tests for the chloride migration coefficient. Our findings highlight NMR relaxometry and LIBS advantages over conventional methods, showcasing superior spatial resolution, non-destructiveness, and, in some cases, expedited results with independence from the formulation of the cement matrix. Thus, these new methods can be used to test the durability of new, more heterogeneous cement-based building materials and compensate for the disadvantages of conventional methods.

This study explores the acceleration of material design in the concrete industry, focusing on improving carbonation resistance, a key factor in the durability of concrete structures. Traditional tests for carbonation resistance are lengthy, but with the construction industry aiming for sustainable production, finding a balance between carbonation resistance and CO2 footprint is crucial. Our research employs two innovative methods: 1. Applying the Sequential Learning App for Materials Discovery (SLAMD), an AI materials design framework, to an extensive dataset of real-world concrete compositions to selectively test materials that meet market demands: maximum durability, optimal eco-durability, and the best cost-durability trade-off. 2. Investigating 1H Nuclear Magnetic Resonance (NMR) relaxometry as a quick alternative for characterizing carbonation behavior, as it saves time compared to traditional tests and assesses the complete material's pore space. Specific NMR features are then integrated into the material design model, with the model's performance compared against traditional approaches. The results of our study are compelling, demonstrating that materials can be precisely tailored to meet specific requirements with minimal data points. This marks a significant stride in the concrete industry, indicating that NMR-based, low-fidelity surrogate characterizations, combined with a focused, data-driven design approach, can substantially accelerate the development of durable, sustainable concrete mixtures.

This study investigates microstructure evolution of carbonating cement paste under varying water-to-cement ratios (w/c) which is an important parameter impacting initial porosity and pore structure that will in turn influence the carbonation process. Cement samples with different water-to-cement ratios (w/c) ranging from 0.4 to 0.6 were exposed to natural carbonation at 20 ℃ and 65% relative humidity. The microstructure was characterized using MIP and Proton nuclear magnetic resonance relaxometry (1H-NMR). Under saturated conditions, 1H-NMR is able to determine a wider range of pore size distribution from capillary pores to gel pores, and even interlayer spaces typically less than 1 nm. Classical Mercury Intrusion Porosimetry (MIP) is always associated with systematic errors stemming from ink bottle effects, while the external pressure from the device can also induce changes in the microstructure. By applying 1H-NMR these problems can be mitigated, leading to more repeatable results. Results show that NMR offers a more efficient means of monitoring and studying the effects of carbonation on microstructure. Thermogravimetric Analysis (TGA) is also employed to determine the correlation between microstructural changes and carbonation degree.

Tropical regions like French Guiana need local, sustainable construction materials to meet the increasing demand for urbanisation. Earth construction, composed of local soil and additives, is gaining increasing attention due to its minimal environmental impact, local availability, and full recyclability. One of the major limitations of earth construction is the high variability of soils. This results in unpredictable mechanical strengths and prevents its widespread industrial use. Therefore, new methods for the rapid identification of suitable soils are required. This paper explores whether several properties of tropical soils could help predict the mechanical strength of associated mortars. Particle size, major oxide composition, infrared spectroscopy, methylene blue value, and soil pH measured in water or potassium chloride (pH KCl) were characterized in nine different soil types. The nine soils were composed of kaolinite clay, iron, and aluminium oxide. Results showed that the mechanical strength of tropical soil mortar was correlated with the soil iron and aluminium oxide content. Importantly, the pH KCl, an easily measurable soil property, was also highly correlated with the soil iron and aluminium oxide content and, consequently, strongly correlated with the compressive strength (R2 = 0.95). Overall, this study shows that the pH KCl can be used to predict the compressive strength of mortars made with tropical soils composed of kaolinite clay, iron, and aluminium oxide.

Spent ion exchange resins are a waste that is generated in the operation of nuclear power plants. These resins are usually managed by their immobilisation in cementitious matrices, specifically based on Portland cement. In this context, alkali-activated cements (AACs) emerge as a promising and more sustainable option for resin immobilisation.This study evaluates the leaching behaviour of AACs containing spent resins (7.5 wt.% by binder). These resins are saturated in a solution consisting of boric acid, cobalt chloride, nickel nitrate, strontium chloride, cesium chloride, and copper sulphate. The AAC evaluated is based on blast furnace slag and fly ash. Sodium carbonate (8 wt.%) is used as an alkaline activator as its utilisation reduces the environmental footprint of the cementitious material. This matrix is compared with a reference Portland-based matrix currently employed for resin immobilisation. To evaluate the confining capacity of the systems a semi-dynamic leaching test is carried out according to ANSI/ANS 16.1-2019.Results indicate that the reference matrix has a higher calcium leaching ratio (12 wt.% by binder) compared to the AAC (3 wt.%), suggesting a potential higher gel degradation of the reference system. The AAC matrix also shows improved strontium retention compared to the reference, whereas the reference matrix exhibits higher boron retention. Additionally, after a 90-day leaching test, AAC demonstrates significantly better mechanical development than the Portland cement-based reference. Micrographs show a region affected by the leachant of around 200 µm, however, EDX results indicate no compositional alteration of the gel in that region.

The paper studies the effect of the presence of cracks on the corrosion of the reinforcement in Ultra High Performance Concrete (UHPC) and the self-healing capacity of this concrete through the use of bacteria, thus protecting the reinforcement. Furthermore, the influence of the presence of steel fibers in the matrix has been analyzed. UHPC samples with two embedded bars have been used to analyze the corrosion response of the reinforcement in crack state that reaches the level of the bar. Samples with and without steel fibers and with and without bacteria were considered. The samples were exposed in a chloride environment and the corrosion response has been monitored for more than 9 months. The initiation and propagation of corrosion have been analyzed through periodic measurement of the corrosion potential (Ecorr) and the corrosion rate (Vcorr). The chloride profile at the crack level and the self-healing of the crack have also been analyzed.In UHPC the incorporation of high doses of fibers slightly affects the initiation and propagation of corrosion due to the different morphology and size of the cracks. A slightly higher corrosion rate occurred in the samples with bacteria compared to similar samples without bacteria even though the crack width was double in the case of the specimen with bacteria (160 and 85 μm respectively). The autogenous self-healing capacity of UHPC masks the contribution of bacteria to the enhancement of autonomous self-healing.

Rice Husk Ash (RHA), a largely available agro-industrial bio-waste is utilized in many applications, especially in civil engineering due to its innate favourable properties including high silica content, large specific surface area, and better temperature stability. Several researchers highlighted its beneficial role in the improvement of soil stability and enhancing cement concrete compressive strength. Aside from the inclusion of RHA in soil and cement, limited studies have been conducted on the suitability of RHA as an asphalt modifier. Asphalt modification is an effective technique to improve the quality and performance of conventional asphalt that is exposed to heavy traffic and extreme climatic conditions. Moreover, it aids in the conservation of resources and reduces the carbon footprint by minimizing the usage of asphalt for pavement construction. In that direction, RHA modification on asphalt not only reduces asphalt consumption but also effectively utilizes RHA together, promoting sustainable pavement construction practices. Therefore, this research aims to develop RHA Modified Asphalt (RMA) and conduct a detailed comparative analysis with virgin asphalt. Specifically, investigates how RHA inclusion in low-viscosity grade asphalt could enhance the consistency and temperature susceptibility in line with that of high-viscosity grade asphalt. Moreover, a micro-level study is carried out wherein the FTIR analysis on binders is performed to understand the RHA’s influence on the asphalt’s chemistry. Overall, it is anticipated that the RHA modification of asphalt would enhance the performance characteristics of low-viscosity grade asphalt making it a sustainable alternative to high-viscosity grade asphalt and advancing the state-of-the-art bio-modification of asphalt.

The objective of this study was to investigate the impact of additives like Fly ash, Ground Granulated Blast Furnace (GGBS) slag, and Lime on the performance of CMA, and correlate them with mix volumetrics. The scope of this study included preparation of CMA, fundamental characterization of CMA at various curing times, and comparison of control and modified CMA strength properties through Indirect Tensile Strength Test (ITS) and Tensile Strength Ratio (TSR). Four types of CMA were considered wherein filler contents and types were varied. The test findings revealed that when 50% Fly ash, 25% GGBS, and 25% Lime were used in the place of mineral filler, the strength of the mix improved significantly. However, the addition of Fly ash without any other additives yielded lower strength as measured by stability when compared to the mix without any additives (control mix). Furthermore, the ITS of CMA mixes prepared with only Fly ash produced marginal changes with respect to the control mixes. The mix, containing 50% Fly ash, 25% GGBS, and 25% Lime as filler material, exhibited the lowest Voids in Mineral Aggregate (VMA) and total voids compared to all other mixes, which resulted in higher strength. Hence, it can be concluded that the additives not only impacted the strength but also contributed to the volumetric properties of CMA. It is envisioned that the study findings will provide important insights into the volumetric and its associated performance of CMA that contributes to state-of-the-art akin to sustainable technologies in pavement engineering.

Cold Mix Asphalt (CMA) is a sustainable alternative to the conventional Hot Mix Asphalt (HMA) in the construction of flexible pavement. The objective of this study was to evaluate the effect of cement and glass fibers as additives and assess the mechanical properties of CMA. The scope of this study included the preparation of CMA with cement and glass fibers, evaluation of mechanical properties using Indirect Tensile Strength (ITS) and Tensile Strength Ratio (TSR), and statistical comparison among the mixes. This study considered a total of 57 samples and performed laboratory investigation to accomplish the objective. The test results indicated that when 2% cement was used in place of filler, significant improvement in the tensile strength was observed as compared to the control mix without cement. Similarly, the resistance to moisture damage also improved in the presence of cement. However, the incorporation of glass fibers did not result in any change in tensile strength. The moisture resistance of the mix with glass fibers was found to be the lowest among all the mixtures. Hence, the use of cement as a filler was found to be beneficial to improve the properties of CMA. Overall, it is envisaged that this study provided important insights into the behavior and properties of CMA with cement and glass fibers, and thus advancing the state-of-the-art akin to the design and construction of sustainable pavement infrastructures using cold mix asphalt.

Accurate prediction of serviceability is crucial in selecting the appropriate maintenance strategies for pavement management systems. Pavement Condition Index (PCI) measures the serviceability levels of pavements based on distresses. In general, the reduction in serviceability can be majorly attributed to traffic, environmental factors, and material properties. This study aimed to develop a comprehensive deterioration model incorporating various factors contributing to pavement conditions. A total of 97 pavement sections were filtered from Long-Term Pavement Performance (LTPP) database that covered 19 pavement distresses, such as rutting, fatigue cracking, block cracking, longitudinal cracking, transverse cracking, patching, potholes, etc. The deterioration model was established that help estimate the pavement conditions as a function of structural capacity of pavement, and environmental and climatic conditions. Two regression coefficients, which were part of deterioration model, were further correlated with traffic, structural condition of pavement, and climatic conditions. Furthermore, the accuracy of the deterioration model was measured using R2 = 0.75 and Se/Sy = 0.05 which indicates a good correlation between the observed PCI obtained from distress condition and predicted PCI from the deterioration model. In summary, this model can be effectively used to estimate the residual life in terms of PCI.

The objective of this study was to evaluate the impact of Ground Granulated Blast-Furnace Slag (GGBS) as a filler on the properties of HMA and analyze the microstructural dispersion to understand its behaviour. This study considered two mixtures with GGBS at 50% and 100% as a replacement for Stone Dust, and compared the properties of two mixtures with a control mix prepared without any GGBS. At first, two fillers, namely, Stone Dust and GGBS were examined at a microscopic level and it was found that GGBS exhibited more rough and angular surfaces than stone dust. Subsequently, Indirect Tensile Strength (ITS) was carried out to examine the tensile properties at 25 ℃. The test findings showed that when GGBS content increased in the HMA, the ITS improved both for dry and wet conditions. This increment was measured through a statistical test, and it was found that the increment incurred due to GGBS was statistically significant at 95% confidence interval. It is envisaged that this study had shed some light on the performance of HMA with GGBS through microscopic analysis and, thus advancing state-of-the-art pertinent to the sustainable design practices of pavement construction.

Due to the development and improvement of nations’ infrastructure, the percentage of paved roads has significantly increased. Bitumen, derived from fossil fuel is considered the most important binder material in case of bituminous road construction worldwide. Focusing on renewable materials as an alternative source for fossil fuels is necessary to meet the world’s increasing energy demand. Thus, this study focuses on the partial replacement of bitumen with a renewable and sustainable material, lignin, generated abundantly in the paper and biofuel industries. Two types of lignin are utilized separately as a partial replacement for control bitumen, and its influence on the properties of modified bitumen and bituminous mixtures is assessed. The laboratory tests demonstrated that the modified bitumen exhibited an enhanced softening point and increased brittleness. A decrease in penetration value was also observed when compared to the control bitumen. Further evaluation of the mechanical properties of lignin-modified bitumen mixtures revealed that Marshall stability and Indirect Tensile Strength (ITS) initially increased with the incorporation of lignin into bitumen. This enhancement was observed up to a certain percentage of lignin dosage. However, a further increase in dosage tends to decrease both mechanical properties. But, in the case of flow number property, it tends to decrease as lignin percentage increases indicating a shift towards material brittleness. Overall addition of lignin as a modifier in bitumen, enhanced properties of modified bitumen and bituminous mix performance.

Traditional soil stabilization methods have been used for many years to improve the load-bearing capacity, durability, and erosion resistance of soil; however, they have some potential drawbacks including air and water pollution, and increased energy consumption. The most used stabilizer, cement considered for its performance and cost-effectiveness is responsible for approximately 5–7% of total carbon dioxide (CO2) emissions worldwide. But nowadays, the global trend incorporates sustainability goals while choosing appropriate soil stabilization. In this direction, various sustainable stabilizers, such as enzymes, and pozzolanas have gained significant attention in recent years. This study explores using a calcium-based mineral stabilizer and GGBS, a byproduct of Iron furnace, as a potential alternative to cement in soil stabilization for flexible pavement construction. The main objective of the paper is to evaluate the mechanical properties of the stabilized soils using CBR followed by the designing of pavements and a comparative life cycle assessment of cement-stabilized flexible pavement construction with mineral-stabilized pavement in SimaPro software, with a cradle-to-gate approach, using the ReCiPe 2016 Endpoint (H) method. The scope of the study is to provide insights into the feasibility and environmental impacts of using mineral stabilizers for soil stabilization in pavement construction. The study’s findings indicate that the pozzolanic reaction during the stabilization process played a crucial role in enhancing the CBR values. This improvement led to a reduction in pavement thickness, highlighting that mineral-stabilized pavements demonstrate lower energy requirements and reduced greenhouse gas emissions thus serving as a viable and sustainable choice for pavement construction.

Most of the water bodies are getting polluted day by day due to the disposal of waste into them. The main contributor to household waste includes used cooking oil. Factories and industries also dump waste oil into nearby rivers and lakes, which pollutes the water. The suitability of using waste cooking oil (WCO) in the bituminous mix as a replacement material is studied. The use of WCO in the bituminous mix without compromising its properties helps its reuse in a sustainable manner. This study aims to determine the optimal dosage of WCO in bituminous concrete. With the aim to determine the optimal dosage of WCO, the material properties of WCO as well as the bitumen needs to be assessed. To determine the optimal bitumen content, Marshall Test is conducted in bituminous mix after determining the properties of its components. The optimal bitumen content for Grade II bituminous concrete is obtained. The Bitumen is further replaced by 0–4% of WCO and Marshall Test was conducted. From the study, it is observed that adding WCO to the bituminous mix won’t jeopardize its stability of the mix under the conditions in Palakkad, Kerala, India. The use of WCO as a replacement material in bituminous concrete helps to reduce the environmental impact by reducing the disposal of WCO. It also reduces the production of virgin bitumen which in turn helps in reducing the cost of construction. Also, from the cost comparison study, it is found that the cost of the project can be reduced considerably, upon using WCO. Thus, the proposed mix is found to be economical and sustainable.

In this study, the possibility of using recycled concrete aggregate (RCA) from building demolition waste in an asphaltic mix, in combination with natural aggregate is explored. RCA was considered as 0%, 25%, 50%, and 60% of the weight of dry aggregates. Two grades of asphalt were used in this study namely, viscosity grade-30 (VG 30) and a polymer-modified asphalt binder (PMB-40). The RCA was used as coarse and fine fractions and the filler was used as hydrated lime. The behavior of the asphalt mix composed of different combinations of RCA and natural aggregates was determined using volumetric, indirect tensile strength, moisture damage, and rutting properties. The results showed an increase in optimum asphalt content in the design mixtures with an increase in the percentage of RCA. In addition, the mix prepared with polymer-modified asphalt and combinations of RCA-NA indicates improvement in indirect tensile strength, moisture damage resistance, and rutting resistance properties as compared to an RCA mix prepared with virgin asphalt binders. The inclusion of hydrated lime as filler and polymer-modified binder enhanced the resistance to moisture damage properties of the RCA mix, irrespective of the asphalt binders. Overall study concluded that the optimum percentage of RCA can be considered without pre-treatment up to 50% for better performance of asphalt mix.