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2021 | Book

Proceedings of the 3rd RILEM Spring Convention and Conference (RSCC 2020)

Volume 2: New Materials and Structures for Ultra-durability

Editors: Dr. Isabel B. Valente, Dr. António Ventura Gouveia, Dr. Salvador S. Dias

Publisher: Springer International Publishing

Book Series : RILEM Bookseries


About this book

This book gathers peer-reviewed contributions presented at the 3rd RILEM Spring Convention and Conference, held at Guimarães and hosted by the University of Minho, Portugal, on March 9-14, 2020. The theme of the Conference was “Ambitioning a Sustainable Future for Built Environment: comprehensive strategies for unprecedented challenges”, which was aimed at discussing current challenges and impacts of the built environment on sustainability. The present volume is dedicated to the topic “New materials and structures for ultra‐durability”, which covers current scientific and technological developments aimed at improving knowledge about degradation mechanisms in construction materials, as well as to the development of new materials with extreme durability. Novel special materials for extreme environments or extreme loading conditions are also included, as well as novel approaches to improve the performance and durability of currently common construction materials. The following subtopics are included: general purpose, constructions, infrastructures and facilities; extreme environments and extreme events; transport and deterioration mechanisms, characterization and mitigation; Supplementary Cementitious Materials, admixtures, additions and other emerging material optimization strategies; smart materials for durable structures.

Table of Contents

Nonlinear Analysis of Offshore Wind Towers in Prefabricated Segments of Prestressed Fibre Reinforced Concrete

This paper presents the nonlinear finite element analysis of a new concept of offshore wind tower made by prefabricated prestressed fibre reinforced concrete (FRC) segments that are assembled to form the final structure. Fibre reinforcement aims to eliminate conventional passive steel reinforcement in order to avoid corrosion concerns and decrease the thickness of the segments. The first stage of the design approach consists on an analytical model that optimizes the geometry of the eolic tower by considering the relevant loading cases, the properties of the developed FRC, the resisting stress levels of the constituent materials and the frequency and lateral deformability of the tower. By determining the thickness and radius along with the height of the tower, this model can provide the solution of minimum FRC volume for the eolic tower. In the second stage of the design approach, the optimum solution from the previous design stage is simulated by a finite element approach that considers the geometric and material nonlinear features. This paper describes the main relevant aspects of this design methodology.

Fabio P. Figueiredo, Joaquim A. O. Barros, A. Ventura-Gouveia
Early Age Temperature Control in Mass Concrete Through Incorporation of Dispersed Phase Change Materials (PCMs)

There is a frequent need to take measures for temperature control in massive concrete structures, as to avoid thermal cracking risk at early ages (induced by temperature gradients inherent to hydration heat release). This research work has explored a procedure for temperature control through the incorporation of phase change materials (PCMs) in laboratory environment (mortar testing). Indeed, PCM’s have the potential to store and release heat energy during phase change from solid to liquid, or vice versa. By choosing a PCM with a melting range between casting temperature and the expected peak temperature, it is possible to attenuate the temperature rise rate in concrete through heat storage (the melting process is endothermic). This paper presents and discusses an experimental work focused on the thermo-physical properties and thermal performance analysis of mortar with direct incorporation of pristine PCM (with a melting temperature of 34 °C and latent heat capacity of 240 J/g) in three volume fractions of 0, 10 and 20% in mixture compositions (volumetric percentage replacement with regard to sand particles), cast into partially insulated cubes with 320 mm3 size. The thermal performance tests revealed the impact of the PCM in the thermal behavior of the cast element, by reducing the maximum peak temperatures in comparison with the reference case (without PCM). Mechanical tests were also performed and revealed that, as expected, their compressive and flexural strength are reduced. Nonetheless, the observed reduction might still be compatible with structural applications in specific contexts, even for the case of high PCM content incorporation (20%).

Mohammad Kheradmand, Romeu Vicente, Miguel Azenha, José Luís Barroso de Aguiar
Determination of Autogenous Self-healing Capability of Cementitious Composites Through Non-destructive Testing

Unlike conventional concrete and fiber reinforced concrete, Engineered Cementitious Composites (ECC) display closely spaced multiple microcracks through strain/deflection-hardening response when subjected to tension-based loadings. These multiple microcracks allow ECC to be characterized with inherent autogenous self-healing capability. With the emergence of cement-based composites exhibiting multiple tight cracking, possibility for favoring the intrinsic self-healing behavior increased. Self-healing phenomenon in cementitious composites is being studied extensively nowadays. Although, great number of tests utilized to evaluate the self-healing mechanism in cementitious composites, implementation can be time consuming in some occasions and results from different tests may not always well-suit. Thus, different from other studies in literature, direct electrical impedance (EI) measurements were used in the present study to evaluate the self-healing performance of ECC mixtures along with rapid chloride permeability test (RCPT) and resonant frequency (RF) measurements. Experimental results revealed that EI testing is rather easy to perform and takes very limited time but it seems that the method itself is markedly influenced by anything modifying ionic state of specimens. Therefore, it looks like a hard task to very accurately assess the self-healing performance of ECC specimens considering the fact that both ongoing hydration and calcium carbonate precipitation which are regarded to be the main mechanisms contributing to the autogenous self-healing significantly changes the specimens’ pore solution chemistry. Well-fitting exponential relationship exists between EI and RCPT measurements at different ages regardless of the mixture and specimen type. However, results from RF tests do not correlate either with EI or RCPT results which is attributed to the different parameters having paramount influence on the individual tests. Although results from different tests do not always correlate well among themselves, three different tests used for the present study are capable of monitoring the self-healing behavior with differing efficiencies.

Gürkan Yıldırım, Oğuzhan Öztürk, Hüseyin Ulugöl, Muhammed Hatem, Mustafa Şahmaran
Autogenous Self-healing Assessment of 1-Year-Old Cementitious Composites

Traditional concrete materials are prone to cracking and as cracks form, durability issues arise which reduce the expected service life of the materials followed by structures incorporating them. This, in many occasions, may lead to repetitive repair and maintenance or even re-construction of certain structural/non-structural sections and structures. Thus, it is highly desirable to reduce the chance and/or further development of cracking. Engineered Cementitious Composites (ECC) are feasible materials to suppress cracking formation and progression through their strain-hardening response under uniaxial tensile loading conditions. Even at the stage of failure, these materials exhibit micron-size cracks which significantly improve the capability to resist against detrimental durability issues. Moreover, these microcracks are constantly reported to be closed through autogenous healing mechanisms with no external interference from outside which significantly improve the mechanical and durability performance and service life of these materials and structures incorporating them. However, the performance of autogenous self-healing in ECC is called into question, especially for late-age specimens since reactions which produce products to plug the micro-size cracks stabilize as the specimens get more and more mature. To clarify this subject, in this study, 1-year-old specimens produced from ECC mixtures incorporated with different mineral admixtures (i.e. Class-F fly ash and ground granulated blast furnace slag) were tested for their self-healing performance. For self-healing evaluation, specimens which were severely preloaded for creating microcracks, were subjected to four different curing conditions which included “Water”, “Air”, “CO2-water” and “CO2-air” for 90 additional days beyond initial 1 year. Tests used for self-healing assessments were electrical impedance (EI) and rapid chloride permeability (RCP). Results indicate that water is a must-have component for enhanced autogenous self-healing efficiency. “CO2-Water” curing results in the most effective self-healing performance regardless of the composition of ECC mixtures. By properly adjusting mixture proportions and curing conditions, microcracks as large as nearly half a millimeter (458 µm) can be healed in only 30 days of further curing. Overall, results clearly suggest that late-age autogenous self-healing capability of ECC can be made as effective as the early-age with proper further environmental conditioning and mixture design.

Gürkan Yıldırım, Hüseyin Ulugöl, Oğuzhan Öztürk, Mustafa Şahmaran
Impact of Super Absorbent Polymers on Early Age Behavior of High Performance Concrete Walls

The prediction of the early age behavior of cementitious materials is a difficult task, because many of the material properties are very sensitive to curing conditions as it is the case for High Performance Concrete (HPC), which usually has a very low water to cement ratio (0.2 < w/c ≤ 0.3). Early age cracking, a common problem for HPC, is caused by Autogenous Shrinkage (AS) and self-desiccation during the cement hydration reactions when the deformation is restrained. However, to avoid the crack development initiated by AS, several solutions can be adopted; one example is the addition of a promising material considered as an internal curing agent, the Super Absorbent Polymers (SAP) which limits the capillary depressions that enhance the formation of the crack. In this study the main goal is to mitigate the shrinkage using SAPs in infrastructure under severe conditions. Therefore, a demonstrator wall was built simulating a typical case with high risk of cracking. With the help of fiber optic SOFO sensors embedded in the wall, real-time deformations are recorded and compared with the demountable mechanical strain gauges (DEMEC) measurements to further investigate the behavior of SAPs in real scale infrastructure. The amount of extra water (in SAP) needed to mitigate shrinkage was determined by performing chemical shrinkage tests on different cement paste combinations. Tests of autogenous shrinkage were performed on mortars using corrugated tubes and showed that SAPs reduce to some extent the AS. Under restrained conditions via ring tests, SAP specimens did not crack. Therefore, SAPs were found promising towards mitigating the shrinkage and enhancing the early age behavior of concrete for a better durability.

J. Kheir, L. De Meyst, J. R. Tenòrio Filho, T. A. Hammer, A. Klausen, B. Hilloulin, A. Loukili, N. De Belie
Influence of Crack Geometry and Crack Width on Carbonation of High-Volume Fly Ash (HVFA) Mortar

Carbonation of concrete results in a drop of the pH which can induce steel corrosion. This is costly to repair and therefore an accurate assessment of the carbonation resistance is required. Carbonation of uncracked concrete has been well-studied. However, in reality many of the concrete structures exhibit cracks, but only limited data is available on the influence of cracks on the carbonation process. Two types of cracks in cylindrical High-Volume Fly Ash mortar specimens were investigated: (1) an artificial crack created by pulling out a cast-in metal plate with a thickness of 100, 200 or 300 µm, and (2) a realistic crack created by splitting cylinders and reattaching them with silicon spacers (with a thickness of 100, 200 or 300 µm). After crack creation the specimens were stored in a carbonation chamber for different durations and the carbonation front was visualised using phenolphthalein. This paper reports on the influence of the crack width and the crack geometry on the CO2 ingress. Artificial cracks with different crack widths did not show a difference in carbonation front. On the other hand, a significant difference could be observed for realistic cracks with different crack widths; realistic cracks with a nominal crack width of 100 µm induced a substantially lower carbonation depth. This demonstrates the influence of crack tortuosity on carbonation; the smaller the crack width, the larger the influence of the tortuosity. Comparing artificial cracks to realistic cracks, it could be concluded that the carbonation depth is lower for realistic cracks. Due to the wall effect near artificial cracks, more pores can be found in the crack area which makes them more susceptible to CO2 ingress.

Tim Van Mullem, Laurence De Meyst, Jessica P. Handoyo, Robby Caspeele, Nele De Belie, Philip Van den Heede
Effect of Curing Temperature on the Alkali Activation of German Brown Coal Fly Ash

Due to environmental concerns regarding the use of Portland cement as the principal binder material in concrete and mortar it is imperative to identify alternative materials that could reduce the carbon footprint of the construction industry. One alternative to address these issues is the use of alkali activated materials, in particular, when based on waste streams that currently have no or only limited industrial application. This paper reports a preliminary study into the synthesis of geopolymer mortar utilizing Brown Coal Fly Ash. The ash had a CaO content of ~39%, indicating that synthesis at ambient or low temperature may be feasible. The paper reports initial trials on the effect of curing temperature, ambient to 120 °C, on the mechanical properties of the mortars produced. The results showed that ambient cured mortar achieved a compressive strength of 6.5 MPa at 3 days. A curing temperature of 60 °C gave the optimum results with a compressive strength of almost 20 MPa and a flexural strength of 3.5 MPa obtained.

David W. Law, Patrick Sturm, Gregor J. G. Gluth, Chamila Gunasekara
Use of Microwave-Accelerated Curing Under Low-Pressure in the Production of Ultra-Durability Portland Type I-Portland Cement Pastes

Globally, the pressure mounts towards attaining low carbon emissions in the energy sector, which has propelled the G8 Summit to advocate for radical high technology approaches for cement production. Among the modern technologies recommended, which also offers the techno-economic advantages is the microwave-based curing. Low pressure accelerated microwave heating, also called accelerated dewatering, is an innovative technique that enhances the properties of HSCP. This study has analyzed the effect of this improvement including the impact of the pressure on feed direction, MW cavity, and the different HSPC samples for every MW treatment batch. The initial state of this treatment established the following. First, to evade internal structure cracks, the delay time should precede the setting time (averagely 30 min after mixing). Secondly, the moisture and temperature increase differences within the MW cavity should be minimal. By following low-pressure microwave treatment will significantly improve properties of HSCP by increasing the resistance to drying shrinkage and water permeability.

Natt Makul
Performance Requirements, Challenges and Existing Solutions of PCM in Massive Concrete for Temperature Control

The development of new solutions and techniques targeted towards better control of the temperature rise in massive concrete at early ages aiming at the reduction of thermal cracking risk, is of paramount importance, namely in respect to durability. To mitigate this issue, one of the most researched solutions that has attracted most interest is the incorporation of Phase Change Materials (PCMs) into massive concrete. PCMs have the capacity to store and release energy in the form of heat within a specific temperature range. The application of PCM in massive concrete, with a melting temperature point/range in between the casting temperature of concrete and the expectable peak temperature (had PCM not been added in the mixture), has the potential to reduce the internal temperature rise, and associated temperature gradients. Therefore, the internal thermal stresses are reduced, and consequently the inherent thermal cracking risk. This paper carries out a critical review on requirements and challenges of different applications of PCMs into massive concrete structures.

Mohammad Kheradmand, Romeu Vicente, Miguel Azenha, José Luís Barroso de Aguiar
Microencapsulation of Isophorone Diisocyanate with Silica Shell

In several studies, Isophorone diisocyanate (IPDI), a monomeric aliphatic diisocyanate, has been microencapsulated with various polymeric shells for self-healing purposes in polymer-based materials. In this study, for the first time, isophorone diisocyanate was microencapsulated with silica shell via interfacial polycondensation of a silica precursor (TEOS). The shell materials of the IPDI-loaded microcapsules reported in the literature are polymeric (organic). It is known from the literature that silica shell can chemically and physically bonded to cementitious matrices, allowing the microcapsules to remain stable for years without deterioration. Essential parameters such as the amounts of core material (IPDI), shell-forming material, and surfactant as well as the stirring speeds were investigated through yield, optical microscopy, SEM, TGA, and FTIR analyses. Promising results were obtained in the process of microencapsulation of isophorone diisocyanate with silica shell. The optimum core material/shell-forming material, oil phase/aqueous phase, and surfactant/oil ratios were found to be 1.0, 0.18, and 0.08, respectively.

Ahsanollah Beglarigale, Doğa Eyice, Yoldaş Seki, Halit Yazıcı
The Response of Synthetic Alkali-Silica Reaction Products to Carbonation

Alkali-silica reaction (ASR) is one of the most studied deterioration mechanisms of concrete. However, the ASR mechanism in the presence of external environments such as carbonation is yet to be understood. The present study simplifies this research gap by subjecting the synthetic ASR gels to carbonation and evaluating the changes in the gels through microanalytical studies. Synthetic ASR gels are prepared and subjected to 3 days of carbonation at 3% CO2 concentration. Thermogravimetric analysis indicated the uptake of CO2 in the form of calcite validating the interaction of ASR and carbonation. Nanoindentation demonstrated the improvement in mechanical properties of the synthetic gel due to carbonation. Electron microscopy coupled with energy dispersive spectroscopy revealed the compositional changes of the gel caused by its interaction with CO2 that led to the improvement in their mechanical properties. These results suggest a possible increase in the deterioration of concrete due to the interaction of ASR and carbonation.

Satyanarayana R. Narneni, Daman K. Panesar
Salt-Scaling Resistance of SAP-Modified Concrete Under Freeze–Thaw Cycles

Concrete structures can be subjected to a range of deteriorating processes due to environmental exposure. When subjected to freeze–thaw cycles, the concrete can experience scaling of the surface layer and internal damage that can further lead to cracking and open the path to other deleterious agents. During winter times, the use of de-icing salts is a very common practice to aid in the cleaning and clearance of roads, bridges and tunnels which increases the effects of scaling. Lately, a lot of research has been developed on the use of superabsorbent polymers (SAPs) to increase the durability of concrete structures by means of internal curing, self-sealing and self-healing. The SAP-modified concrete presents a higher resistance to salt-scaling when compared to concrete mixtures without SAPs. In this paper, the scaling resistance of four concrete compositions with and without superabsorbent polymers is studied. One commercial SAP applied to mitigate the autogenous shrinkage and two “in-house” developed SAPs are used. Cylindrical specimens were exposed to 28 freeze–thaw cycles with a 3% NaCl solution. Two of the SAP containing-mixtures showed a reduction of 49% (commercial SAP) and 54% (“in-house” SAP) in salt-scaling in comparison with the reference mixture. On the other hand, another “in-house” developed SAP induced an increase in scaling. The water kinetics of the SAPs was found to play a major role in the performance of the mixtures regarding the scaling resistance.

José Roberto Tenório Filho, Els Mannekens, Didier Snoeck, Nele De Belie
Pore-Scale Numerical Modeling Tools for Improving Efficiency of Direct Carbon Capture in Compacts

Carbonate bonded materials are considered to be a viable alternative to reduce carbon emission from cement industry. Such materials are carbon emission negative since they sequestrate CO2 through carbonaQtion reaction and present potential of making commercial profit. However, carbonation reaction depends on several factors such as pore structure, particle size distribution, relative humidity, temperature, CO2 gas pressure, etc. The design of carbonate bonded materials requires a fine tuning of these parameters which is preliminary done through extensive experimental campaigns. Here we present an alternative approach of in-silico based design of carbon bonded material, where microstructure modeling plays a central role in the design process. Finally, a newly developed microstructure modeling framework is presented. This framework utilizes the discrete element method to generate the initial compact structure, the lattice Boltzmann method to compute the equilibrium distribution of liquid and gas phase, and as a last step a cellular automation-based model for evolution of microstructure due to the carbonation reaction. The model qualitatively reproduces the experimental observations thus providing confidence in our modeling approach. Quantitive comparison with experiments available in the literature and further refinement of the model is ongoing. The developed microstructure modeling framework is foreseen as a valuable tool for designing carbon bonded materials.

Ravi A. Patel, Nikolaos I. Prasianakis
Assessing the Alkali-Sensitivity of the Mechanical Behavior of Jute Fibers to Evaluate Their Durability in Cementitious Composites Applications

Jute fibers have been studied for their numerous properties and, recently, much attention has been paid to the possibility of using them as reinforcing material in cement based matrices for structural engineering applications. In the context of structural reinforcement methods, the use of composite materials reinforced with synthetic fibers is now quite common, due to their light weight, versatility and adaptability. However, in recent years, the scientific community has been interested on the use of natural composite materials, with the goal of finding innovative solutions with renewable, recyclable, sustainable and biodegradable products for the construction industry. This research investigates the use of jute fibers to assess their suitability as reinforcing materials in cementitious composites for historic/existing masonry structures retrofitting. As a matter of fact, these applications have to consider the possible low durability of jute, like all other cellulose-based fibers, especially into alkaline environments. This work reports the ongoing experimental investigation to set the mechanical performance of jute fibers. The experimental program considers jute yarns in their natural condition and evaluates how the alkaline matrices would affect the fiber mechanical properties. The paper summarizes the first results obtained from durability tests on jute yarns as a first step towards the assessment of the long-term performance of Natural Fiber Reinforced Cementitious Composites.

C. B. de Carvalho Bello, A. Cecchi, L. Ferrara
Long-Term Capillary Imbibition of Mortars with Slag and Fly Ash

Short-term capillary imbibition (or absorption) tests are practical and provide useful information about the performance of cementitious materials. Most of these tests are performed for a short period (<1 week), however, if the test continues for a longer period there is still liquid ingress. This further ingress of liquid is believed to be related to moisture diffusion inside the sample during long-term measurements. Such process occurs at a much slower rate than the short-term capillary imbibition. This paper describes the effect of supplementary cementitious materials (SCMs) on long-term capillary imbibition tests and presents the application of an earlier developed approach that relates the water uptake to t0.25 for long-term measurements. To assess the whole capillary imbibition phenomenon, long-term measurements were performed for 10 weeks in mortar mixes with and without SCMs. Cement was partially replaced by ground granulated blast-furnace slag (SB) and fly ash (FA). The advance of the capillary rise was restricted much more in mixes with FA or SB than in the OPC mix. As these samples were tested at 360 days, this led to a more refined microstructure in the SB and FA mixes in comparison with the OPC mix. The decrease of water uptake with time occurred in all mixes and it can be explained by the changing hydraulic diffusivity in cementitious materials due to their hygroscopic behaviour. Long-term measurements reveal primary and secondary periods of capillary imbibition that are well described by a bi-linear relationship with the fourth root of time.

Natalia Alderete, Yury A. Villagrán-Zaccardi, Nele De Belie
Geopolymer Concrete Structures: Bond with Deformed Steel Bars

The promising performances showed by geopolymer concrete led several researchers to investigate about possibilities of using this material in reinforced structural elements. Since geopolymer binder has a different microstructure from Ordinary Portland Cement (OPC) it is necessary to investigate, also, on its bonding behavior with steel bar that as well-known influences the service and ultimate conditions. For this reason, in the last decades both direct pull-out and beam-end tests were carried out with this material. Generally, it has been observed that Geopolymer Concrete (GPC) has higher bond strength than OPC concrete due to the higher compression strength and the dense and compact microstructure of GPC. This means that the existing design equation for bond strength prediction of ordinary concrete can be conservatively used also for GPC. In this paper the bond-slip behavior between GPC and steel reinforcing bar with two different diameters has been investigated.

V. Romanazzi, M. Leone, M. Aiello, M. R. Pecce
10 Years of Research on Sugar Cane Bagasse Ash as Supplementary Cementitious Material

We present a survey of 10 years of researches carried out by the Federal University of Rio de Janeiro (COPPE/UFRJ) and the State University of Northern Rio de Janeiro (UENF) on the use of sugar cane bagasse ash (SCBA) as supplementary cementitious material (SCM). The main findings of such comprehensive studies are here summarized: the use of SCBA for producing concrete; the role of grinding and calcination; the physical and chemical effects; the use of SCBA in industrial scale; blending of SCBA and rice husk ash (RHA); and long-term compressive behavior.

Guilherme C. Cordeiro, Romildo D. Toledo Filho, Eduardo M. R. Fairbairn, Luis M. Tavares
Thermal Performance of Steel and Fibre Reinforced Concrete Composite Floor

In general, steel and concrete composite floors tend to present a reduced functional performance (considering thermal and acoustic conditions), due to their low mass and to the high conductivity of the steel elements. By including components with high thermal insulation capacity in these structural systems, it is possible to maintain the structure lightness and not compromise the thermal performance. Within this work, the analysis is dedicated to a composite floor in which a fibre reinforced concrete (FRC) slab is associated with a concrete filled “U” type steel profile. The fibre reinforcement avoids the use of conventional reinforcement, with significant savings in term of fabrication time. Filler blocks are inserted, composed by thermal insulation material (EPS), between the “U” shaped steel profiles, which act as formwork during the casting phase and, after the concrete hardening, contributing to improve the system´s thermal performance. This system was evaluated through numerical assessment. The analysis enabled to determine the thermal transmittance (U-value) and to identify the critical zones in terms of thermal insulation efficiency. The performance of the proposed solution was also compared to other flooring solutions. According to the results obtained, the proposed composite floor presents a better thermal behaviour than other more traditional flooring systems.

Talita L. Silva, Isabel B. Valente, Joaquim Barros, Maria José Roupar, Sandra M. Silva, Ricardo Mateus
Interface Evaluation of Carbon Textile Reinforced Composites

Cement production is responsible for high CO2 emissions. Focusing on environmental sustainability, there is nowadays a desire to make thinner concrete elements, thereby reducing the amount of cement used. Textile reinforced concrete (TRC) is a cementitious matrix composite reinforced with one or multiple layers of 2D or 3D fabrics that present elevated mechanical performance aligned with high load-bearing capacity. The textiles can be constituted by several types of fibres. Carbon fibres are an attractive option due to their superior mechanical and durability properties. However, they present a low bond with the cementitious matrix. The bond between the textile reinforcement and the matrix is the weakest region of the composite, therefore governing the element behaviour up to its failure. Polymeric coatings can be used to enhance the interaction between the carbon fabric and the cementitious matrix. Nevertheless, these materials present a decomposition temperature extremely lower than the one of the carbon fabrics, limiting their use in case of elevated temperature conditions. An alternative to improve the bond and, consequently, the composite mechanical performance is matrix modification and use of inorganic high-tech ceramics, such as geopolymers, as coatings. This paper aims to present a comparison of the interface behaviour of carbon textile reinforced composites embedded in distinct matrices. For this, pull-out tests will be performed in carbon yarns impregnated with SBR. A cementitious and a geopolymer matrix will be evaluated. Furthermore, the influence of an additional geopolymer coating will also be analyzed.

Rebecca M. C. Silva, Ana C. C. Trindade, Flávio A. Silva
Calorimetry Study of the Influence of Portland Cement Content, Slag/Fly Ash Ratio, and Activator Type on the Early Hydration of Hybrid Cements

Hybrid cements (cements composed of Portland clinker, supplementary cementitious materials and an alkaline activator) potentially combine advantages of conventional cements with those of alternative binders, such as low heat of hydration and improved durability in some environments. While fly ash-based hybrid cements have been studied in considerable detail, slag-dominated hybrid cements appear to have received less attention. Here, the latter materials have been studied by isothermal calorimetry, X-ray diffraction and strength testing. The heat of hydration of these cements was as low as ~50% of that of an ordinary Portland cement, while their strength after 28-day curing was in the range 31–61 MPa. The phase assemblages after 28-day curing depended on the activator, with Na2SO4 leading to ettringite and Na2CO3 leading to hemicarbonate formation, respectively, besides C–A–S–H, portlandite and hydrotalcite. The U phase was identified when a high Na2SO4 dose and/or fly ash was employed. Na2SO4 accelerated the early reaction of the Portland clinker, while Na2CO3 appeared to decrease the extent of reaction of the clinker and led to a shift of the second hydration peak (likely related to slag reaction) to later hydration times, as did substitution of slag by fly ash. Increasing Na2SO4 dose from 4 to 6% did not lead to further acceleration of hydration or improved strength.

Gregor J. G. Gluth, Solen Garel
Chloride Ion Penetration into Cracked UHPFRC During Wetting-drying Cycles

The subject of this paper is the extent to which, during wetting–drying cycles, chloride ions can penetrate Ultra-high-Performance Fibre Reinforced Cementitious Composites (UHPFRC) specimens subjected to combined mechanical and environmental load. Pre-cracking was obtained by subjecting prismatic specimens (40 × 40 × 60mm3) to four-point bending until a predefined crack opening displacement (COD) is reached, using a dedicated test setup. Three target CODs were studied: 300, 350 and 400 µm. Exposure to a concentrated chloride solution (3.5% NaCl) was used as an environmental load. Specimens we subjected to wetting–drying cycles for one year. After this exposure period, the chloride penetration was characterised both qualitatively (by colourimetric analysis with silver nitrate) and quantitatively (by determining the chloride profile). The effect of damage level on chloride penetration and its impact on structures durability is discussed in the current paper.

Ana Mafalda Matos, Sandra Nunes, Stefan Chaves Figueiredo, Erik Schlangen, José L. Barroso Aguiar
Cracking Potential of Alkali-Activated Concrete Induced by Autogenous Shrinkage

Alkali activated concrete (AAC) has not received broader industry acceptance, one reason of which lies in the uncertainties in the durability against shrinkage and potential cracking. Many studies reported that AAC exhibit larger autogenous shrinkage than OPC concrete. However, it is unable to deduce that AAC should show higher cracking potential than OPC concrete only based on the higher autogenous shrinkage of AAC. The cracking potential of concrete is determined by multiple factors including autogenous shrinkage, creep/relaxation, elastic modulus, and tensile properties of the concrete. However, very few studies have considered these parameters. Furthermore, the influence of precursors (e.g. slag or fly ash) on the cracking potential of AAC induced by autogenous shrinkage is also rarely studied. The aim of this study, therefore, is to investigate the autogenous shrinkage-induced cracking potential of slag and fly ash-based AAC. The free autogenous shrinkage of the specimens is measured by Autogenous Deformation Testing Machine (ADTM). The autogenous shrinkage-induced stress and cracking of the concrete under restraint condition is tracked by Thermal Stress Testing Machine (TSTM). Additionally, the influence of precursors on the autogenous shrinkage induced cracking potential is discussed.

Zhenming Li, Shizhe Zhang, Xuhui Liang, Albina Kostiuchenko, Guang Ye
Influence of Nanofibrillated Cellulose (NFC) on the Mechanics of Cement Pastes

The use of nanomaterials in several fields has been growing in the past few years due to their unique physical and mechanical properties. Nevertheless, the use of these materials in civil engineering is fairly new and still requires extensive research to completely understand their potential. The search and development of new cementitious materials that are less harmful to the environment are significantly important. In this scenario, the nanocellulose comes as an interesting option of reinforcement for cementitious elements. One of the constraints of the more intensive employment of nanomaterials is the formation of agglomerates that act as defects and stress concentrators in the elements. In this way, the development of efficient dispersion techniques is essential for the total exploitation of the mechanical properties of the nanomaterials, including the nanocellulose. In the present research, nanofibrillated cellulose (NFC) obtained from Eucalyptus pulp fiber was added into cement pastes thin elements in several contents. The mechanical behavior was assessed by means of four-point bending tests. The percentage of NFC varied between 0 and 1% of the mass of cement. In an attempt to explore most of the properties of NFC and then enhance the mechanical properties of the composites, dispersion strategies were applied as a step on the mixture procedure. Chemical dispersion methods were combined with mechanical stirring in order to produce a homogenous solution of water and NFC. Results showed expressive improvements regarding mechanical properties upon the addition of NFC on the cement pastes. The flexural strength enhanced by more than 400%, and the flexural modulus more than 13 times. Results also indicated that the dispersion methods applied were able to influence positively the flexural strength, and this improvement is sensible to the content of NFC.

Letícia O. de Souza, Lourdes M. S. Souza, Flávio A. Silva
Rheological Behaviour and Flow Properties of Alkali-Activated Materials

Great efforts are being made by researchers concerning the development of cement-less concrete to reduce both greenhouse gas emissions and energy use. Alkali-activated materials (AAMs) are one of the viable alternatives which are attracting increasing attention in practice and research due to their lower CO2 emissions. In this paper, the rheological behaviour of binary blended alkali-activated fly ash/slag pastes is investigated. Various rheological measurements were conducted such as paste fluidity, viscosity, yield stress and thinning index. The effect of different parameters was assessed including the slag content, SiO2/Na2O ratio as well as the solution/binder ratio. The experimental results revealed that increasing the slag content increases the viscosity and yield stress and reduced the overall paste fluidity at elapsed times. The viscosity of AAM pastes was in the range of 0.77–7.55 Pa.s. The AAM pastes behaved like a shear-thinning fluid, where the apparent viscosity decreased by increasing the shear rate. The SiO2/Na2O ratio in the activator had no significant effect on shear thinning parameters and fluidity. The thinning index, which is the ratio between viscosity at low and high shear rates, of AAM pastes was found to be in the range of 1.92–4.01. The volumetric solution-to-binder ratio was shown to effectively influence the thinning index. The findings of this study confirm that the fluidity and thinning index are independent of the chemical composition of the used activator but depend upon the changes done in the volume of both slag and activation solutions.

Mohammed Fouad Alnahhal, Taehwan Kim, Ailar Hajimohammadi
Material Characterization of Geopolymer Concrete for Its Beneficial Use in Composite Construction

Geopolymer concrete (GPC) is an inorganic, mineral-based construction material with high resistance to chemical attack and further excellent properties such as rapid strength development and relatively low CO2 emissions in comparison to ordinary Portland cement based normal concrete (PCC). However, production technologies, corresponding to the workability and time-dependent properties during the hardening of GPC are not known in detail. The aim of an ongoing research project is to combine GPC with PCC to form composite structures for applications in chemically aggressive environments such as sewers. This paper deals with material properties of GPC, which have significant impact on the composite action. GPC formulations with different workability (soft and stiff-plastic consistencies) were developed and investigated with regard to their compressive and tensile strength development over time, as well as shrinkage during hardening under different ambient conditions (autogenous shrinkage, drying shrinkage, early shrinkage). The GPCs investigated show significant autogenous shrinkage and drying shrinkage. Under dry conditions, additionally very high early shrinkage occurs immediately after the beginning of hardening, which was tested using the image correlation method. The extent of this early shrinkage depends strongly on the thickness of the specimen. As another result of this experimental study, equations for the prediction of the strength development over time are given in this paper.

Joachim Juhart, Christopher Gößler, Cyrill Grengg, Florian Mittermayr, Andrew McIntosh, Bernhard Freytag
Long-Term Performance of Cement Composites with Wood Biomass Ash

Positive trend of using wood biomass as renewable energy source (RES) results in generating large amounts of wood biomass ash (WBA). WBA is mostly landfilled as a waste. WBA could be used as secondary raw material in another industry reducing the environmental and social problems related to its disposal. In order to ensure enough cement for construction needs and while reducing fuel and raw material requirements and subsequent emissions during cement production, the use of new waste materials in the cement and construction industry is necessary. Therefore, one possible option is WBA utilization in the construction sector as a new raw material. The chemical and physical properties of WBA are different from coal fly ash (FA) and currently do not meet the existing requirements for concrete application. Application of novel materials in the construction composites highlights the need for generic, quantitative relations between chemical and physical properties and its behavior and effect on the cement composites. This research investigated the long-term durability performance of cement composites where WBA is used as partial cement replacement. Gas permeability and capillary absorption were investigated on mortars where fly WBAs, originating from different combustor technologies, were used as replacement of cement CEM I 42.5R.

Ivana Carević, Nina Štirmer, Jelena Šantek Bajto, Karmen Kostanić Jurić
Steel Reinforcement in Slag Containing Binders and Its Susceptibility to Chloride-Induced Corrosion

The construction industry has moved from using plain Portland cement (PC) to binders with high proportions of supplementary cementitious materials such as blast furnace slags such as CEM II, CEM III A/B, and is increasingly targeting alkali-activated slags (AAS). The reducing nature of the blast furnace is retained by the slag, which contains ~1–3 wt.% sulfur (expressed as SO3), mostly in a reduced state and available to dissolve when mixed with water or an alkaline solution. The pore solution chemistry of many modern ‘alternative’ construction materials can be characterised as being rich in reduced sulfur species, and highly alkaline. There remain many open questions about the influence of such alkaline-sulfide solutions on the passive film formed on common mild steel reinforcement, and thus the susceptibility of this steel to chloride-induced corrosion. This study focusses on the influence of reduced sulfur species on mechanisms of passivation of steel and the phenomena of localised corrosion due to chlorides in highly alkaline electrolyte solutions with containing varying concentrations of reduced sulfur species, via electrochemical and spectroscopic techniques. The presence of HS− in alkaline electrolytes alters not only the passivation behaviour of mild steel, but also the mechanism of chloride-induced corrosion. In alkaline solutions containing sulfide, the competitive adsorption of [OH−] and [HS−] inhibits and retards the formation of a passive film, conventionally a Fe (III) oxide, and instead forms a surface film on the reinforcement composed of an assemblage of Fe(OH)2 and Fe-S complexes. In alkaline-sulfide solutions, the critical chloride concentration to induce corrosion was found to be dependent on the concentration of sulfide (i.e. the reducing capability of the electrolyte), and on the time that steel specimens were exposed to the electrolyte, consistent with the progressive formation of a sulfidic layer on the steel. Additionally, it has been shown that in the presence of high concentrations of HS−, the onset of chloride induced corrosion cannot be easily detected by conventional electrochemical measurements of OCP, Rp or icorr, as these tend to be highly influenced by the chemistry of the pore solution. Therefore, interpretation of electrochemical data obtained for aqueous systems containing HS− based on standard guidelines that assume Fe to be the sole redox-active species would result in misleading conclusions regarding whether the steel is in the passive or the active state.

Shishir Mundra, John L. Provis
Using Waste Materials in Durable Environmentally Friendly Concrete

Solid waste management is one of the major environmental concern all over the world. Big amounts of waste tires are generated each year and utilization of this waste is a big issue from the aspects of disposal of this amount of this waste, and health hazards. One of the recommended methods to utilize of this waste to be used as an ingredient of Portland cement concrete that could be used in concrete block paving, pedestrian blocks, highway sound walls, residential driveways, and garage floors. In this study, an experimental investigation has been performed using a waste rubber tires and bentonite in the concrete mix design. Rubber waste is used to replace fine aggregate in the concrete with different percentages (5, 20, 25, 30, 40%). Slump test are conducted to evaluate the workability of fresh concrete. Compressive strength of cubes at 7 days and 28 days are studied and compared with conventional concrete. The research work addresses the effect of using waste rubber tires and bentonite on durability of concrete. For this purpose, specimens were submerged in solution containing 50 g/l of NaOH and H2SO4, and according to the results it can be stated, that rubberized concrete can be used in to improve concrete durability. Based on the test results, the ideal percentage of mix which shows maximum compressive strength is identified. The optimal mix from the laboratory experimental investigation contained 20% waste rubber tires and 5% Bentonite replacement that exhibited a compressive strength of 33 MPa at 28 days.

Rana Morsy, Sohair Ghoniem
Magnesium-Phosphate Cement Pastes to Encapsulate Industrial Waste Powders

Although Ordinary Portland Cement (OPC) is the main cement considered in relation to industrial and radioactive waste management (as being the most widely used in the world), several waste types are incompatible with OPC. In particular, magnesium potassium phosphate cements (MKPC) are more suited to some waste types. They are promising durable alternatives to OPC cements, owing to their fast and adjustable setting time and to a high compressive strength on the short term. However, in stoichiometric proportions (Mg/P = 1), MKPC pastes swell significantly. Swelling decreases with increasing (Mg/P), i.e. with increasing content in over-stoichiometric MgO. In the context of hazardous waste management, our idea is to incorporate as much of powdered waste as possible, in replacement to over-stoichiometric MgO. The adequate granulometry and nature of powders, suitable with MKPC, need to be determined. Therefore, in this research, in MKPC pastes, over-stœchiometric MgO is replaced by fillers of varying nature and granulometry (fineness). First results explain the phenomena and phase formation, responsible for MKPC swelling, and how this is avoided when adding adequate powders. The most adapted filler, which removes swelling and allows sufficient spread, is described, as well as the threshold mass ratio of fines/cement (F/C), above which swelling of stœchiometric MKPC cement is eliminated.

Matthieu De Campos, Catherine A. Davy, Murielle Rivenet, Justo Garcia
Microstructural Evaluation of Fibre-Reinforced Slag-Based Foams

Alkali-activated foam materials were produced using electric arc furnace steel slag and ladle furnace basic slag as precursors, sodium water glass (Na2SiO3) and sodium hydroxide (NaOH) as alkali activators, and hydrogen peroxide (H2O2) as a foaming agent. The anionic surfactant sodium dodecyl sulfate (SDS) was used for the stabilization of pores in the matrix. In order to improve the mechanical properties (fracture resistance expressed as bending strength), seven types of fibres (polypropylene (PP), polyvinyl alcohol (PVA), basalt (B), cellulose (C), steel fibre (S), mineral wool (M) and wood fibres (W)) were added to selected mixtures and embedded into the AAF matrix. The bending and compressive strength measurements show that the addition of fibres, especially PP, improved bending strength. Microstructural analysis gives an insight into the interfacial zones between the fibres and the AA matrix. Where a non-uniform distribution of fibres and/ or a weak contact between fibres and the matrix was detected, there was negligible or no impact on the mechanical properties. In the cases where the fibres were uniformly distributed and a good adhesion between fibres and the matrix was established, the bending strength increased.

M. Češnovar, K. Traven, V. Ducman
Utilization of Biochar as a Multifunctional Additive in Cement-Based Materials

This article presents an experimental study on the application of processed biochar as a partial replacement of cement. Raw biochar was chemo-mechanically modified to produce super-hydrophobic carbonaceous powder (SHCP). The effects of this SHCP on paste and mortar samples were monitored in terms of compressive strength, hydration products, electrical conductivity, water absorption, and embodied carbon. The performances of the mortar samples were monitored after 7 and 28 days of sealed curing. SHCP primarily worked as inert inclusion and did not significantly affect the cement hydration. Nevertheless, the addition of SHCP as partial replacement of cement was found to decrease the water sorption, increase the electrical conductivity, and decrease the embodied carbon of the mortar samples. As such, this study provided experimental evidence that biochar can be utilized as a multifunctional additive in cement-based composites.

Muhammad Intesarul Haque, Rakibul Islam Khan, Warda Ashraf, Hemant Pendse
Pore Size Distribution of Cement Based Materials Determined by Dynamic Water Vapor Sorption and Low Temperature Calorimetry

In this work, both dynamic water vapor sorption (DVS) and low temperature calorimetry (LTC) methods were adopted to study the pore size distribution of cement pastes prepared by two types of cements CEM I and CEM III. A model porous material, MCM-41, was also included in order to investigate important aspects of the measurement and the data evaluation approaches. As indirect methods for pore structure characterization, important assumptions involved in the data analysis of both methods were highlighted and discussed. In addition, a special attention was paid to the comparison of the results obtained from the two methods. A careful examination of the bases for the two methods for pore structure characterization revealed that a number of matters could affect the obtained results, including sample preparation, possible influencing factors on the measured results, unsolved factors for data analysis, etc. Consequently, the results obtained from one method might differ significantly from the other. Nevertheless, a certain degree of agreement was still found for the pore size distributions determined by the DVS and the LTC methods, despite of the uncertainties involved in each method. Meanwhile, it was concluded that probably none of the two studied methods could deliver the “true” (actual) pore size distribution information at this stage. To further improve the accuracy of the results obtained from the methods, it was highlighted that emphases should be laid on clarifying relevant assumptions made in both measurement and data analysis.

Tian Wang, Min Wu
Experimental Investigation on the Influence of Organic Extract from Citrus Sinensis as an Additive in Lime Mortar Preparation

In the twentieth century, the restoration process in heritage buildings is carried out using cement mortars. From the ongoing study it is found that this can cause extensive damage to the existing structures. In order to avoid consequences of this cement based mortar in the ancient structures, study of lime based mortar is necessary. Many researches are going on to analyses the various strength properties, reactions and the strength factors of lime mortars for different percentages of additives used. Carbonation, which is a slow process, enhances the hardening of the fresh lime mortar and hence increases in its compatibility. For increase in the carbonation rate, various admixtures are added to the lime mortar. It also increases the mechanical strength, weather-resistance and water resistance compared to common lime mortar. This research aims at studying the physical, mechanical and chemical transformations in fresh state and hardened state properties of lime mortar through experimental investigations and for understanding the influence of use of organic extract from Citrus Sinensis (Orange) in lime mortar. Traditional slaking of calcium rich lime was done for various periods of 1, 5, 15 and 30 days. On slaking, quick lime combines with water to form calcium hydroxide which can be used as binder in a mortar. With carbon dioxide from atmosphere, this calcium hydroxide further carbonates to form calcium carbonate. Slaking improves the surface area of the mix. The slaked lime was mixed in the ratio of 1:3 with aggregate, grinded for 0, 5, 10, 15 min and the addition of 5% organic extract. The fresh state properties were obtained based on consistency, workability, and setting time tests. The mechanical property was evaluated by compressive strength test after 28 days of curing. Chemical property of the specimen was evaluated by XRD and FT-IR. Results reveal an increase in the transformation of calcium hydroxide to calcium carbonate in lime mortar with organic addition, enhancing its strength.

Ben George, Simon Jayasingh
A Correlation Between Sorptivity Coefficients of Concrete as Calculated from Relationships of Water Uptake with t0.5 or t0.25

Sorptivity is a transport parameter widely used for assessing the durable performance of concrete. However, anomalous capillary absorption (or imbibition) is normally reported for cementitious materials, i.e. capillary water uptake evolves non-linearly with t0.5. For decades, different methods of dealing with the anomaly have been adopted in different standards. A novel approach based on the hygroscopic nature of cementitious materials has been recently proposed. A linear relationship of water uptake with t0.25 (instead of t0.5) was proven sound in terms of accurate description of the transport process and fitting with experimental results. For comparative purposes, there is therefore a need for a correlation between the new coefficients and coefficients in the literature computed upon considering an evolution with t0.5. In this manner, the potential of sorptivity in the design for durability of concrete structures, previously hindered by the anomalous behaviour of the material, may be further explored. This paper presents a correlation between sorptivity coefficients of concrete as calculated from relationships of water uptake with t0.5 and t0.25. The data was obtained from the literature and contrasted with own data produced in 6 different laboratories. Samples were pre-dried at 50 °C for a limited period of time. With some limits, the obtained relationship is sound. No particular considerations are required with regard to the features of the concrete mixes (e.g. water-to-cement ratio, type of cement, aggregate type, curing).

Yury A. Villagrán-Zaccardi, Natalia M. Alderete, Alejandra Benítez, María F. Carrasco, Patricio Corallo, Raúl López, Alejo Musante, Cristian Rios
Numerical Analyses of the Connections Between Representative SFRC Prestressed Rings of Off-Shore Wind Towers

Off-shore wind towers are the wind farms used to harvest wind energy to generate electricity on water bodies. With the growing need of sustainable production for electricity, off shore wind towers are finding a rapid growth in application. In fact, 4% of European electricity demands will be generated by offshore wind towers by 2020 in European waters. The current project concentrates on development of an innovative structural system using advanced materials for lightweight and durable offshore towers. The present paper discusses the nonlinear finite element modelling of the connections between representative prefabricated rings of off-shore wind towers made by steel fibre reinforced concrete (SFRC) and prestressed by a hybrid system formed by carbon fibre reinforced polymers (CFRP) bars and steel strands. The connection between these two rings are assured by post-tension high steel strength cables and concrete-concrete shear friction of treated surfaces. The model takes into account different types of loads and moments originating from rotor, wind and water currents considering the critical loading conditions. The material nonlinear analyses were carried out in FEMIX V4.0 software, considering a 3D constitutive model capable of simulating the relevant nonlinear features of the SFRC, and interface finite elements for modelling the shear friction of the concrete-concrete surfaces in contact. The SFRC rings are modelled by solid elements, and the longitudinal CFRP bars and steel strands by 3D embedded cables. Parametric studies are carried out in order to assess the influence of different fracture parameters of the SFRC and post-tension level in the cables (steel and CFRP) on the performance of the connection between the two rings.

Chandan C. Gowda, Fabio P. Figueiredo, Joaquim A. O. Barros, A. Ventura-Gouveia
The Effect of Mechanical Load on Carbonation of Concrete: Discussion on Test Methods and Results

Carbonation of concrete, consuming Ca(OH)2 and lowering concrete alkalinity, will lead to reinforcement corrosion and therefore is one of the major causes of concrete deterioration. Most research mainly focuses on the carbonation of concrete without mechanical load. However, concrete structures will bear load in practice, which has a significant influence on CO2 transport and carbonation rate. So, studies on carbonation in combination with mechanical load are of great importance for optimizing service life prediction models. In this review paper, it is discussed how imposed load affects the carbonation of concrete and how a dedicated experimental setup is achieved in the lab. The advantages and disadvantages of existing devices are discussed in terms of specimen size, loading frame, method for applying load and stress compensation. Finally, changes in cracks and pore structure induced by compressive loads at different levels are analyzed with respect to gas permeability and carbonation depth.

Zhiyuan Liu, Philip Van den Heede, Nele De Belie
Usefulness of Mercury Porosimetry to Assess the Porosity of Cement Composites with the Addition of Aerogel Particles

Today’s need to reduce the energy consumption of buildings makes it necessary to search for new material solutions. Such materials are, for example, cement composites with various types of additives, such as foamed-polystyrene granulates, cenospheres or aerogels, which are intended to reduce the composite’s thermal conductivity. The introduction of such additives to concrete composites may be an issue for the assessment of microstructural properties of these materials. This is because the microstructure of concrete and additives are completely different. This problem exist in the mercury porosimetry of cement composites with the addition of aerogel granulate. The Washburn equation, traditionally used in mercury porosimetry, gives false porosity results when applied to aerogels. This paper presents the problems and the method of determining the total porosity and integral and log-differential graphs for cement composites with addition of aerogels. Two types of composites based on lightweight aggregates were tested: expanded clay and sintered fly ash aggregate. In both variants, concrete was made with the addition of aerogel granulate, which accounts for 20% of the total composite volume. Also reference concretes of the same composition, but without aerogel were prepared. The paper presents a method of combining the results of mercury porosimetry using the classic Washburn equation, which is suitable for cement-based materials, and the Pirard equation showing the relationship between the pressure of injected mercury and the diameter of pores in compressed hyperporous materials. The study also provides cumulative and log-differential diagrams of pore distribution in tested concrete with aerogel addition. The values of thermal conductivity in dry state and the compression strength average values for composites after 28 days of curing are also presented.

Jarosław Strzałkowski, Halina Garbalińska
Calcined Clay-To-Limestone Ratio on Durability Properties of Concrete with Low Clinker CEM II/B-M(Q/LL) Cements

The present work focuses on the effect of different calcined clay-to-limestone ratios for a clinker replacement level of 35% on durability properties of CEM II/B-M(Q-LL) cements. Two calcined clay-to-limestone ratios, 0.5 and 0.83 expressed as Q/(Q + L), were considered in this investigation. In addition, some specific manufactured batches of finely ground calcined smectite clay and limestone filler with relative high chloride contents were opportunely considered for testing. This was done to investigate the viability of using alternative fuels in clinker, limestone filler and calcined clay productions without compromising the durability of concrete. The durability properties evaluated in concrete specimens with comparable 28-day strength demonstrated that these low clinker cements show a high resistance to chloride penetration, which is independently of calcined clay-to-limestone ratio and chloride content of the cement within the investigated compositions. Moreover, the high reactivity of calcined smectite clay is enough to mitigate ASR even at the cement composition with the lowest Q/(Q + L) and the increased alkalis content derived from calcined clay does not affect the performance in concrete regarding ASR. Nonetheless, it was detected that the increase of the calcined clay at the expense of limestone content in these cement compositions leads to a decrease of the resistance to freeze/thaw.

S. Ferreiro, R. Sacchi, L. Frølich, D. Herfort, J. S. Damtoft
A New Dilation Model for FRP Fully/partially Confined Concrete Column Under Axial Loading

Experimental research has confirmed that the usage of fiber reinforced polymer (FRP) composite materials can be a reliable solution to substantially improve axial and dilation behavior of confined concrete columns. In this regard, FRP partial confinement system is a good compromise from the cost competitiveness point of the view, while the application of discrete FRP strips provides less confinement efficiency compared to full confinement system. Experimental observations demonstrated that the concrete at the middle distance between the FRP strips experiences more transversal expansion compared to concrete at the strip regions. It can result in a considerable decrease in the confinement performance in curtailing concrete transversal expansion, overwhelming the activation of FRP confining pressure. The present study is dedicated to the development of a new dilation model for both full and partial confinement systems, which takes into account the substantial impact of non-uniform distribution of concrete transversal expansion, a scientific topic not yet addressed comprehensibly in existing formulations. For this purpose, a reduction factor was developed in the determination of the efficiency confinement parameter, by considering available experimental results. Furthermore, based on a database of FRP fully/partially confined concrete, a new analytical relation between secant Poisson’s ratio and axial strain was proposed. To evaluate the reliability and predictive performance of the developed dilation model, it was applied on the simulation of experimental tests available in the literature. The results revealed that the developed model is capable of predicting the experimental counterparts with acceptable accuracy in a design context.

Javad Shayanfar, Mohammadali Rezazadeh, Joaquim Barros, Honeyeh Ramezansefat
Urban Furniture in Fiber Reinforcement Concrete with High Durability

Within the scope of the “NG_TPfib” R&D project, Exporplás and CiviTest have, in the recent past, developed a new typology of polypropylene fibers for the production of urban furniture of high durability by eliminating conventional steel reinforcements susceptive to corrosion. This reinforcement replacement strategy also allows the development of lighter and more elegant urban furniture with complex geometries at competitive costs, giving possibility for new generation of elements of added architectural and sculptural value.This paper describes the beginning research carried out for the development and production of this type of furniture and presents the main results obtained in the development of the material. In this context, the mechanical properties and some durability indicators of the material were characterized. Due to the prefabrication nature of the production technique adopted for this type of urban furniture, special care was done on the evaluation of the early age properties of this composite, mainly the post-cracking tensile capacity. For this purpose the evolution of the compressive strength and elasticity modulus were evaluated from standard compression tests, while inverse analysis with the results obtained in 3-point notched beam bending tests at different ages have provided the evolution of the post-cracking tensile capacity of this composite. For assessing some relevant aspects of the durability of this composite, its permeability by immersion and by capillarity was evaluated, as well as the influence of the chloride penetration by dry–wet cycles on the its post-cracking resistance. The present paper describes the experimental programs carried out and presents and discusses the relevant results.

Felipe Melo, Inês Costa, Tiago Valente, Cristina Frazão, Christoph de Sousa, Ana Moreira, João Sá
Self-healing of Engineered Cementitious Composites at Two Different Maturity Levels

While there are numerous studies in the literature about the application of maturity method to ordinary concrete, strength development mechanism of Engineered Cementitious Composite (ECC) and its effect on self-healing behavior have not been studied in the light of maturity concept. This study aims to apply the maturity method on standard ECC mixture and to compare the self-healing behavior of ECC specimens matured at two different levels. Based on this purpose, datum temperature for temperature–time factor calculation was determined for the standard ECC mixture and maturity indices corresponding to 28 days and 365 days age were calculated. Self-healing assessments of the specimens at low and high maturity levels were carried out by considering the recovery of flexural strengths and ultrasonic pulse velocities and crack closure by visual inspection. In general, it is observed that although ECC exhibits self-healing when the cracks are formed at high maturity level, as the maturity level increases, self-healing capacity of ECC shows some decrement.

Özlem Kasap Keskin, Kamil Tekin, Süleyman Bahadır Keskin
Comparison of Chloride-Induce Corrosion of Steel in Cement and Alkali-Activated Fly Ash Mortars

The aim of this paper is to make an initial evaluation of chloride-induced corrosion behaviour of steel in alkali-activated fly ash and compare it to behaviour of classical cement mortar. Fly ash used in this research was obtained from regional production and was activated with sodium silicate and sodium hydroxide. Setup for evaluating corrosion behaviour consisted of structural steel plate covered with mortar layer under tap water or simulated seawater solutions. Corrosion behaviour of structural steel plates was monitored by Open Circuit Potential (OCP) and Linear Polarization (LP). The mortars have been additionally characterized by their mechanical properties, pore structure obtained by mercury intrusion porosimetry (MIP), electrical resistivity and chloride migration according to NT BUILD 492.

Antonino Runci, Marijana Serdar
Correction to: Proceedings of the 3rd RILEM Spring Convention and Conference (RSCC 2020)

The original version of the book was published with incorrect initial of the editor “Salvador J. E. Dias” has been corrected. The book have been updated with the change.

Isabel B. Valente, António Ventura Gouveia, Salvador J. E. Dias
Proceedings of the 3rd RILEM Spring Convention and Conference (RSCC 2020)
Dr. Isabel B. Valente
Dr. António Ventura Gouveia
Dr. Salvador S. Dias
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Print ISBN