Proceedings of the Canadian Society for Civil Engineering Annual Conference 2023, Volume 6

Cementitious composites are widely used as building materials due to their affordability, accessibility, and ease of forming. However, they have drawbacks such as less flexibility, brittleness, and low resistance to thermal stress. The use of fibers as reinforcing material is one way to alleviate these concerns. Carbon fibers have high elastic modulus and strength, resulting in composites with superior fatigue resistance, flexibility, and compressive strength. However, the surface inertness restricts the adhesion ability of carbon fibers to form a bond with the composite matrix and hence requires surface modifications to improve the surface characteristics. In this study, two strategies are used to improve the surface roughness of carbon fibers: first, an alkali treatment; second, a combination of an alkali and fly ash treatment. To determine the best strategy for enhancing the carbon fibers’ adhesive and mechanical characteristics, a comparative investigation is conducted. SEM microstructural analysis is used to examine the bonding between the carbon fibers and the matrix as well as to confirm the effects of the treatment on the fiber's surface. The sessile drop contact angle was used to study the surface wettability of the fiber and the four-probe electrical resistivity testing was used to analyze the resistivity of the fiber. The interfacial bond strength between the fiber and the matrix was obtained from pull-out testing. From the test, it was found that the alkali treatment weakens the mechanical strength and bonding propensity of the fiber, but the addition of the fly ash greatly compensates for the adverse effect and increases the bond strength when compared to the untreated fiber.

The development of new geopolymer foams by using construction waste can highly contribute to reducing the environmental burdens of the building industry while providing a sustainable and lightweight material for thermal and acoustic insulation. The goal of this study was to optimize the mechanical, thermal, and physical properties of geopolymer foam binders prepared only from concrete waste (CW) precursor or with ground granulated blast furnace slag (GGBS). The direct chemical foaming method was adopted using cetyl trimethyl ammonium bromide (CTAB) as a surfactant and hydrogen peroxide (H₂O₂) and aluminum powder (ALP) as foaming agents. The effects of using between 1 and 3% of CTAB, 3 and 9% of H₂O_2, and 0.01 and 0.09% of ALP on the compressive strength, density, porosity, and thermal conductivity of CW-based geopolymer foams were considered. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDS) analyses and digital image processing techniques were employed to characterize the microstructure and quantify the open pores of the foam material. The results confirmed the possibility of preparing a stable foam geopolymer by using up to 55% of CW as a precursor, whereas achieving densities between 1.350 and 0.600 g/cm³ with corresponding compressive strengths ranging from 12.87 to 1.56 and thermal conductivities from 0.258 to 0.093 W/mK. The SEM–EDS analyses revealed the formation of various pore size distributions within the geopolymer network, in line with the thermal conductivity results of CW-based geopolymer foams.

Freeze–thaw cycles play a crucial impact on the degradation of outdoor structures in the northern climate regions. Outdoor structures such as bridges are located in harsh environmental conditions and are subject to daily fatigue stress, corrosion, and component rapid deterioration. Bonding carbon fiber reinforced polymer (CFRP) to the bridge element surface has proven to be an appealing technique of bridge reinforcement. This research aims to investigate and evaluate the use of externally bonded CFRP in bridge retrofits under freeze–thaw conditions. The mechanical properties of FRP systems degrade under exposure to certain environments, such as salt water, chemicals, ultraviolet light, high temperatures, high humidity, and freezing and thawing cycles. Numerical research using the finite element method is performed to examine the flexural behavior of CFRP-strengthened beams under static loading, considering the effect of freeze–thaw effect. Different freeze–thaw cycles (100, 200, 300 Cycles) are considered in finite element analysis. The results indicate that the freeze–thaw cycles under 200 cycles have a slight effect on the mode of failure of the strengthened RC deep beam, by increasing the number of cycles, the failure mode changes from tension to compression failure due to the decrease in the compressive strength of concrete.

This paper evaluates the effect of using Portland Limestone Cement (PLC) on the expansion of the accelerated mortar bar test (AMBT). The preliminary results of the program showed no significant difference between the expansions of samples made with GU or GUL cement from the same supplier. Four aggregates were used in this study with four sources of cement. The difference between the expansion of GU and GUL for all the samples from the same supplier except one was <8.3% of the mean expansion, which is the expected within-lab precision of the test. Only one aggregate showed a difference of >8.3% when used with one source of cement, with a 14-day expansion of 0.28% and 0.34% for GU and GUL, respectively. The level of Na₂O_e of the Portland cement did not significantly impact the AMBT expansion, likely due to the ample supply of alkalis from the soaking solution. As expected, alkali-carbonate reactive aggregate did not show an expansion above 0.10% at 14 days, except with one cement (Cem 3); however, the expansion was not much higher than the 0.10% limit.

CFRP is commonly used as external reinforcement on bridges in service; it increases the life of bridges by solving problems such as structural degradation caused by environmental damage. However, CFRP's bond with concrete has some limitations, including durability issues of the bond between CFRP and concrete that are caused by aggressive environmental exposure and fatigue loading. This paper studied the bond behavior of composite sheets bonded to concrete blocks through single-lap shear tests. Three externally CFRP bonded to concrete blocks were tested via fatigue loading under constant range stress. Load-slip curves and the strain profiles in the interface zone are presented as a function of the number of cycles. Moreover, comparison and analysis of failure modes are presented between specimens subjected to static and fatigue loading. In addition, the interface stiffness degradation as a function of the number of fatigue loading cycles is presented in this paper and a damage model was proposed to describe the fatigue damage of the CFRP-concrete interface. The results of this study demonstrate the effect of the fatigue loading on the CFRP to concrete bond behavior, in terms of bond stiffness degradation and mode of failure.

The construction sector consumes a massive amount of natural resources and energy and is a major emitter of greenhouse gases resulting in global temperature increase. Thus, the employment of recycled and green materials is essential for sustainable advancement. Hemp-lime composites, commonly known as hempcrete, are a promising low-carbon alternative to conventional building materials; however, further research is needed to optimize hempcrete mix designs and binder composition. This study investigated the impact of using different pozzolanic materials including metakaolin, silica fume, GGBFS, and fly ash on the physical and mechanical properties of the lime binder used to produce hempcrete. The experimental procedure was executed by testing 27 different mix designs generated by varying three parameters, namely the lime replacement ratio of the pozzolanic materials (10% and 20%), type of pozzolan, and the water/binder ratio (0.8, 1, and 1.2) in the mix. The physical and mechanical properties of the mortar including compressive strength, drying shrinkage, and flowability were carried out. The results showed that batches containing GGBFS and silica fume performed the best compared with the other mixes.

In a quest to reduce the shrinkage of concrete at an early age and during its service life, the incorporation of short fibres has been found to inhibit the shrinkage thereby preventing cracks formation in the concrete. Recently, the use of chopped basalt fibres (BF) to mitigate cracks has been gaining huge attention due to its economic and sustainable advantage. However, in order to ensure that the overall performance of concrete is improved, it is paramount to evaluate how different dosages of basalt fibres typically used to reduce/prevent shrinkage in concrete mixtures affect its mechanical properties. Therefore, this study was carried out to investigate the effect of three fibre dosages on the mechanical properties of concrete. BF was used at a dosage of 0.1, 0.2 and 0.3% while the mechanical properties investigated are the compressive strength, flexural strength and split tensile strength. The results from this study showed that there is a slight reduction in the compressive strength of concrete incorporating BF when compared to concrete without any fibre.

Our natural environment has witnessed severe issues over the past decades caused by the construction industry. Cement manufacturing and gypsum drywall disposal are two of the most debatable topics in this domain due to their direct or indirect negative impact on the natural environment such as air pollution, water contamination, climate change, and soil degradation to name a few. To address these challenges, several solutions have been introduced by researchers to date and one of them is replacing the cement in concrete with recycled gypsum from waste drywall. The resulting concrete (gypsum concrete) has been evaluated in terms of short-term compressive strength (up to 90) days and the result has supported the theory of gypsum concrete functionality to some extent. In this paper, the long-term physical and mechanical properties of gypsum concrete as well as the overall durability of this novel material under two environmental exposures have been evaluated. Concrete cylinders with dimensions of 100 × 200 mm were prepared. Three different mix designs for cementitious material were considered. 0, 10, and 20% of cement were replaced by gypsum powder (fine gypsum). Specimens were planned to be tested on day 7 and day 28. The cylinders were exposed to airdry and freshwater conditions. Afterward, the compressive strength of cylinders was tested at 1000, 3000, and 6000 h after the curing period to evaluate the durability of specimens. Moreover, the alterations in the volume and weight of specimens over time are noted and analyzed.

Concrete is the most commonly used material in the world for construction, and to produce this large amount of concrete requires the production of large quantities of cement, which results in the degradation of the environment by releasing harmful gases. One approach for making eco-friendly concrete is to use less cement in concrete; for that aim, other cementitious materials can be utilized as a partial replacement for cement. This study focuses on the mechanical and durability properties of concrete having limestone powder (LSP) as a partial replacement for cement. Five different combinations are considered for this study; the LSP replacement level is 5, 10, 15, and 20% (by weight). The result indicates that the slump value increases with increasing LSP content. At 28 days, compressive strength and flexural strength are the highest for replacing 10% cement with LSP. The concrete cylinders are subjected to elevated temperatures (200 and 400 °C) for one hour and then cooled down to room temperature (25 °C). Reduction in compressive strength with increased temperature is up to 6% at 200 °C temperature and up to 11% at 400 °C temperature. Therefore, incorporating 10% LSP in concrete as a replacement for Portland cement will increase concrete's mechanical and durability properties.

Concrete is the most abundantly used material worldwide, with an estimate of 4.4 billion tons being produced in 2021 alone. Although it is reliable as a building material, each ton of concrete produced results in the creation of approximately one ton of CO₂. This combined with the mass amounts of concrete used across the world each year results in the concrete industry being responsible for about 8% of all pollution each year. Considering this, new alternatives to concrete are being developed to attempt to resolve this issue. An experimental program is designed to test one of such materials. A sustainable building materials manufacturing company has explored the creation of an alternative to concrete block material and has supplied samples for the completion of this project. These samples use recycled plastic as a binder for the aggregates rather than the Portland cement used in traditional concrete. The goal of this project is to test the material properties of recycled plastic concrete to determine the stress–strain behavior in both compression and tension. These tests allowed for the determination of the compression and tension modulus to analyze whether the material behaves the same in tension as in compression. Along with this, the material was also tested in compression over a variety of temperatures to assess the impact that changes in temperature have on the strength of the material. Cylinders with a diameter of 100 mm and length of 200 mm were prepped and tested for compressive to determine compression properties, while prisms with a length of approximately 300 mm, and width and depth of approximately 100 mm were tested to determine tensile properties. The results obtained give insight into potential applications of the alternative material, and changes or improvements that could be made to allow for further applications.

The use of fiber-reinforced polymers (FRPs) has quickly grown during the past decades due to their strength, durability, and versatility. Although, given the first use of FRPs, in the 1980s, and their service life of 20 to 40 years for wind turbine blades and 50 to 70 years for FRP bars in structures and bridges, it is anticipated that a huge amount of FRP waste will accumulate in the upcoming years. Given this fact and the non-renewability of FRPs, reusing them could be considered the most promising approach. Many researchers studied using recycled FRP composites as aggregate, filler, and fibers to reduce the demand for aggregate and/or cement in concrete materials, slowing down resource depletion. Unfortunately, the application of recycled composites in concrete and their impacts on the compressive strength of concrete properties have not been comprehensively determined. However, the existence of a review article on using recycled FRP composites can identify the gaps and provide valuable insight for future studies. Therefore, this article aims to comprehensively examine the influence of using recycled FRP composites in concrete based on recent literature. Results demonstrated that the main adverse impact of using recycled FRP bars and blades is due to the low strength of their interfacial transition zone with cement paste in the cementitious composites. Nonetheless, findings demonstrated that the impact of using recycled FRP composites is similar to that of concrete-recycled aggregates, showing their potential as an alternative for recycled aggregates.

Cementitious mixtures incorporating carbon nanofibers (CNFs) have emerged as new construction materials with enhanced mechanical and electrical performance. Due to their high strength, small size, and high aspect ratio, CNFs have the potential to bridge the cracks, limit their propagation, and fill the pores inside cementitious mixtures. Therefore, there has been a growing interest in the utilization of CNFs in the concrete industry, especially for the production of ultra-high-performance concretes (UHPCs) and self-sensing cementitious mixtures for structural health monitoring applications. Thus far, several studies have focused on the compressive strength of cementitious mixtures incorporating various nanomaterials including CNFs at the age of 28 days. The enhancing effect of CNFs on the early-age compressive strength of cementitious mixtures (i.e., up to 7 days of age), however, has not been largely investigated. Such early-age mechanical performance improvements are important to promote wider applications of CNFs in the concrete industry, for example, to compensate for the delays in the strength development of concretes made with large volumes of supplementary cementitious materials (SCMs). To fill this gap, the current paper aims to evaluate the effect of incorporating CNFs in various concentrations on the heat of hydration and compressive strength development of cement pastes in the first 7 days after production. Aqueous dispersions containing different concentrations of CNFs and a polycarboxylate ether (PCE)-based superplasticizer were prepared, subjected to ultrasound energy, and added to cement pastes at the time of mixing. The superplasticizer content in each mixture was adjusted so that all the cement pastes had a similar flow. The cement pastes were tested for isothermal calorimetry and compressive strength at the ages of 1, 3, and 7 days. Furthermore, scanning electron microscopy (SEM) was used to evaluate the dispersion of CNFs in the cement pastes.

This research aimed to evaluate the performance of sprayed shotcrete mixtures prepared by silicate-based and alkali-free accelerators. A new innovative silicate accelerator was used at dosages of 4% and 6% and was compared to a standard silicate accelerator and an alkali-free accelerator at dosages of 6% by binder weight. Scaled-down shotcrete elements were cast to investigate the different shotcrete mixtures’ behaviour. The mechanical and microstructure properties of shotcrete mixtures at different curing ages were investigated. Results proved the competitive behaviour of the innovative silicate accelerator compared to other accelerators. Also, the new innovative silicate-based accelerator had less tendency to reduce mixtures’ compressive strength at a later age, up to 90 days.

Concrete is one of the most widely used materials in construction around the world and the importance of monitoring the workability of concrete is well-known. Many attempts have been made to develop an acceptable and accurate test that can measure concrete workability and represent wet concrete mixture characteristics. However, with the exception of the classic Slump test, only a few tests have gained acceptance. Furthermore, newer concrete mixtures, such as high-performance concrete mixtures, are subject to significant changes, even with slight modifications in the proportions of the materials of the mix. This has made the monitoring of workability more critical. This study examines and compares three workability tests that have been used in the concrete industry: ASTM Slump, K-Slump, and Kelly Ball workability tests. These tests were used to measure the workability of 34 different concrete mixtures obtained based on a statistically based mixture-process experimental design. The tests’ results are compared and suggestions for future concrete workability testing are made.

Surface treatment applied to concrete elements is a viable strategy to provide efficient protection against intrusive media which helps to reduce future maintenance and repair costs. In many Canadian cities, including the City of Winnipeg (COW), bridges that were built years ago have bare concrete decks, showing signs of cracking and deterioration, which need to be coated, treated, or sealed to maintain their serviceability and achieve their design service life. Typically, bridge decks are affected by freezing–thawing cycles, de-icing salts, and abrasion. The COW has considered different deck protection strategies including the applications of silane coatings, methyl methacrylate (MMA) healer-sealers, polymer-wearing surfaces, concrete overlays, and waterproofing membranes with asphalt overlays. It has been found that these coatings tend to detach/crack or require reapplications during their service life. Additionally, cracks were found to be a prime source of fluid ingression to initiate chloride induced corrosion of the bridge deck’s reinforcing steel. The authors previously completed laboratory studies to evaluate the efficacy of plain and nano-modified coatings as superficial treatments for concrete. In Phase I of this study, crackedcores were obtained from three bridges in Winnipeg, which were treated with various coatings in the laboratory to observe their resistance to the absorption of fluids. To verify the results in the field (Phase II), the same coatings were applied on a COW bridge deck, which is approximately 32 years old, to investigate the transport properties and microstructural changes after the coatings’ application. The current paper reports on the performance of silane, MMA, and colloidal nano-silica (50% nano-silica) coatings. Cracked and uncracked cores were extracted from each coating, and the barrier properties were implicated by absorption and penetrability to project their effectiveness.

Concrete is a high-performance construction material that requires exiguous maintenance throughout its design life. Despite being the most popular construction material, concrete is brittle and tends to develop cracks under tensile stresses. This property of concrete has often resulted in catastrophic failures resulting in the loss of life and property. Reinforcing steel bars has been used to induce ductility and enhance the load-carrying capacity of concrete, but reinforced concrete remains vulnerable to tensile cracking due to its poor crack-arresting mechanism and the risk of metal corrosion. This can be overcome by the addition of randomly distributed discrete fibres such as steel fibres, synthetic fibres, natural fibres to the composite to form Fibre Reinforced Concrete (FRC). FRC can be cost-effective, especially if the fibre is a locally sourced waste material from agricultural activities. This paper reviews the potential of natural fibres obtained from agricultural waste to improve the tensile behavior of concrete and augment its post-crack strength. This study focuses on the mechanism of crack formation/propagation, compressive strength, tensile strength, flexural strength, drying shrinkage characteristics of natural fibre-reinforced concrete (NFRC). The properties of natural fibres including the type of fibre, its dimensions, volumetric concentration, and the required pre-treatment largely influence the overall mechanical behavior of concrete. At the same time, the major drawback of using natural fibres in concrete is their susceptibility to degradation due to fibre’s capacity for water absorption. In order to minimize the fibre degradation in NFRC, studies have looked at coating or treating the fibres, and lowering the alkalinity of the cement around the fibre. However, coating of natural fibres to achieve these properties and then testing their response to degradation inside concrete seems to be lacking in the literature. Thus, this study aims to examine the various challenges associated with the use of natural fibres in concrete.

Recently, great attention has been given to the environmental impact of greenhouse gas emissions as well as the impact of non-biodegradable waste materials on the environment. Asphalt road production is a huge source of carbon dioxide emission both during the production of asphalt cement and the paving process. The rapid growth of the automobile industry and the worldwide dependence on vehicles have led to a massive increase in rubber tire waste. On another hand, Low-Density Polyethylene (LDPE) such as plastic bags and food packaging plastic containers are a major source of non-biodegradable waste. This research studies the incorporation of these waste materials into the asphalt binder without compromising its function. Replacing a portion of the asphalt binder may help reduce carbon dioxide emissions during the production process. Additionally, incorporating waste material into the asphalt mix minimizes the amount of waste material reaching landfills. The aim of this research is to incorporate waste materials, sourced in Egypt, into asphalt binder to improve road quality. The research compares non-modified asphalt binders, crumb rubber-modified asphalt binders and LDPE-modified asphalt binders using the Superpave technique. Waste tire rubber and second-grade LDPE plastic bags were processed into powder and incorporated into asphalt binder separately at varying percentages using the wet method. It was found that both modifiers led to significantly better performance grades of the asphalt binders. A combination of rubber and LDPE modified asphalt was also examined with respective percentages of each modifier selected according to their individual performance. The 5% LDPE modified binder was found to be the best performing asphalt binder when compared to the rest of the modified binders. The 5% LDPE and 7% CR modified asphalt were found to have PG of 76–28 and PG 70–28, respectively. The improved performance of the modified asphalt binder was evaluated against the required PG of Egyptian roads and it was found that adding 5% of either CR or LDPE will substantially enhance the virgin Egyptian asphalt binder to the point of meeting the regional Egyptian asphalt requirements of PG 70–10 and PG 76–10, respectively.

Determining compressive fracture behaviour via fundamental fracture mechanics has proven difficult due to analytical complexities. However, recent studies have yielded significant breakthroughs. Linear elastic (LE) K_I variation with crack length in uniaxial compression has been found for certain void geometries—the observed K_I nonlinearity may independently explain stable compressive crack propagation, a long-outstanding issue. Other authors have also noted that LE stress fields of continua with voids in uniaxial compression have predictive value in crack propagation, but detailed guidelines for stress field interpretations have not yet been proposed. Together, these findings suggest an accurate interpretation of LE stress field components in a fracture context may be a significant step towards describing compressive fracture. Herein, concepts which may prove useful in the interpretation of LE stress fields are proposed. Chief among these concepts is the small flaw geometry assumption, a concept inherent in stress concentration studies that permits the computation of stress intensity factors from LE stress fields. The presented concepts are used to comment on the fracture characteristics of single and multi-void systems. These concepts are also used to provide guidance on determining the zone of influence (ZOI) of a void subjected to a particular distant loading.

Biochar is one of the new potential sustainable substitutions for ordinary Portland cement that has been studied to reduce the demand for ordinary Portland cement. This replacement can significantly cut down the environmental impacts of the construction industry and reduce the carbon dioxide emission of concrete and the industry. According to the literature review, one of the main barriers against using biochar in the construction industry is that the role and influence of biochar on the properties of cementitious composites have not been conclusively determined. Accordingly, the current study examines the role and effect of biochar on the strength and structure of cementitious mortar. To this end, the effect of using biochar as both cement replacement and additive was examined by manufacturing and testing 81 mortar cubic specimens with ultrasonic pulse velocity and compression tests. Findings indicated that, although biochar improves internal hydration by providing additional water and surface, adding biochar to the mortar reduces the compressive strength of mortar specimens. It is worth mentioning that specimens containing 15% or less biochar can completely meet the minimum strength requirement for masonry mortar based on ASTM C270. The ultrasonic results revealed that the main reason for the strength reduction of the specimens containing biochar is the low strength of biochar particles. Accordingly, some insights were proposed to enlighten the way for future studies.

The construction industry is one of the largest generators of waste. The majority of widely used insulation panels are made of synthetic materials that end up in landfill. The mycelium of the mushroom Pleurotus ostreatus, 100% compostable, has interesting properties that give it the potential to be the next trendy bio-based material. The literature reports its low thermal conductivity comparable to that of currently used insulation materials. The fire resistance of mycelium is also better than that of extruded polystyrene insulation materials. Mycelium has a lower heat production rate, it generates less smoke and CO₂ in addition to having a longer ignition time (300 vs. 50 s) limiting the spread of fires. Mycelium also has interesting acoustic properties. However, there is still much to do with the technology of growing and transforming mycelium into construction materials to be developed in Canada. The overall objective of this study is to produce an insulator that can be 100% composted after use. The specific objectives are to define the mycelium culture protocol, to define the optimal growth temperature of Pleurotus ostreatus on ash chips, and to measure the thermal conductivity by the modified transient plane source method (MTPS) in order to compare them to those measured for hemp and glass wool. Different combinations of mushroom species and substrates can be used to manufacture mycelium-based products like that of Pleurotus ostreatus which is an edible mushroom safe for human health. The final properties of the material obtained will depend on the chosen mycelium-substrate composition. Pleurotus ostreatus grows on ash chips free of insecticide. The different experimental tests allow us to define the optimal substrate composition (10% rye; 90% ash) for an optimized growth time at the best incubation temperature (25, 30, 35 °C) determined by isothermal calorimetry tests with ash as the reference substrate. Preliminary tests allow us to consider the use of mycelium as a thermal insulator following more in-depth studies.

Alkali-activated materials (AAMs) are introduced as promising green materials with less carbon dioxide (CO₂) footprints rather than ordinary Portland cement (OPC) in concrete production. Moreover, as innovative, durable, and sustainable materials, AAMs exhibited superior mechanical properties and durability performances comparable to OPC. AAMs have advantageous characteristics (i.e., high early-age strength, high strength development, high chemical resistance, severe environmental conditions, etc.). Those intrinsic features have promoted AAMs in diverse applications, including repair approaches. Furthermore, from a sustainability perspective, self-healing as an inherent feature of AAMs should be addressed when considering those materials for repair purposes. AAMs have been deduced to be potentially self-healed autogenously and autonomously. Autogenous healing is defined as the ability of concrete to heal cracks over the long term without any manual interference. Autonomous healing, by which the induced cracks will be plugged using engineered materials embedded inside the mixture during casting. This paper focused on the autogenous self-healing of AAMs, the extent of self-healing, and factors affecting self-healing efficiency. Also, determination and quantification of self-healing were demonstrated as well.

The serviceability and durability of any reinforced concrete structure depend on the bonding characteristics between concrete and reinforcing bars. The tensile stresses in the structures are transferred to concrete from reinforcing bars through the effective bond action between them. But often, plain concrete fails to achieve a complete bond with the reinforcing bars embedded in it. Thus, this research incorporates locally available galvanized iron fiber (GIF) to increase the mechanical as well as the bonding properties of concrete. Test parameters include the percentage of GIF as 0, 0.25, and 0.5%; the diameter (D) of rebar as 12, 16, and 20 mm; and the embedded length as 8D and 12D. Results reveal that a decrease in the bar size and the embedment length increases the bond strength. In terms of GIF, it positively impacts bonding properties in both cases. Besides, most GIF-reinforced specimens demonstrate either concrete rapture/v-notch failure or rebar rapture/rebar yielding failure. Only the samples with 8D embedded length undergo pullout failure. The 0.25% GIF-reinforced concrete exhibits comparatively higher strength than the 0.5% GIF-reinforced concrete. Finally, this research will encourage engineers to build GIF-reinforced concrete using a locally available GIF to produce a better bonding mechanism in concrete.

Nowadays, the management of waste is one of the most crucial challenges worldwide. In the past decades, agro-waste has become one of the most significant environmental challenges in waste management. In this way, the disposal of agricultural waste has been turned into one of the most critical issues for environmentalists worldwide. Consequently, agro-waste is used in the construction industry in order to have sustainable buildings. In this study, the potential of using agro-waste in non-structural concrete as a partial replacement for coarse aggregate was investigated. Initially, the used agro-waste was characterized, and properties were compared with coarse aggregate specifications for non-structural concrete applications. Then, fresh, and hardened properties were evaluated for mixtures with various agro-waste contents. Results showed that density was directly affected by the percentage of replacement, while the compressive strength was significantly reduced until 60% due to the spongy characteristic of agro-wastes when the replacement goes up to 20%. However, both meet the limits for some non-structural applications. In this regard, the optimum percentage of using agro-waste in structural concrete is 10% as a replacement for coarse aggregate.

Calcium aluminate cement (CAC) is known as the most important class of non-Portland cement, which contains high alumina and lime. Different than ordinary Portland cement (OPC) which is made of 95% clinker, the manufacturing of CAC involves bauxite as a source of alumina in addition to limestone, which makes it more appropriate for applications requiring high-early strengths and chemical resistance. Although the use of CAC in engineered cementitious composites (ECCs) can enhance their mechanical characteristics in terms of compressive and flexural strengths, it may also cause higher shrinkage and risk of cracking than OPC-ECCs. In this study, the fresh, mechanical, and shrinkage properties of ECC compositions incorporating CAC as an alternative to OPC were considered. Furthermore, the effect of using fly ash with CAC at various FA/CAC ratios of 0, 0.8, 1.2, and 1.5 was investigated in an attempt to control the shrinkage of CAC-based ECCs, while targeting equivalent or better mechanical strengths and deflections. The performances of five ECC mixtures were studied by measuring their flowability, compressive and flexural strengths, mid-span deflection capacity, and cracking and shrinkage behavior at different curing ages. Also, the microstructural change related to the high alumina content of CAC was analyzed by SEM–EDS. The results confirmed the possible development of high-early strength ECC with the use of CAC cement instead of OPC. Interestingly, the higher calcium amounts with the use of FA in CAC-ECC mixtures allowed to optimize the shrinkage results to reach values two times lower than the control OPC-ECC.

Recent studies have shown that glass powder can be used as supplementary cementitious material (SCM) in engineered cementitious composites (ECC). However, there is a need to evaluate the long-term permeability properties of conventional ECC and those incorporating glass powder as SCM. Also, the limited use of non-destructive test methods to evaluate ECC has called for a need to investigate the response of ECC to non-destructive tests (NDT) and create a correlation between these NDT results and other properties of ECC. Therefore, this study was carried out to evaluate the long-term permeability properties of ECC incorporating glass powder. Ultrasonic pulse velocity was also used as a non-destructive test to evaluate the performance of the ECC. Results observed from this study showed a correlation between the ultrasonic pulse velocity passing through the ECC and the permeability properties. Results from this study will serve as a useful resource for evaluating the performance of ECC based on non-destructive tests such as that of ultrasonic pulse velocity.

Ultra high-performance concrete (UHPC) is a relatively new concrete material that is high in strength and durability. Its high quality typically comes at the price of high material costs, high carbon footprint and low production efficiency. The objective of this paper is to explore the design process for developing an economical base mix of UHPC that can be used for a wide array of precast building applications. Taking an iterative approach, various materials were tried and tested, measuring the hardened and fresh properties of the resulting UHPC. This paper discusses the use of particle packing, and cement and sand selection to optimize the mixing time, workability and strength of category 120 UHPC. While a particle packing model is a good starting point for developing a UHPC mix, other factors that needed to be considered were the chemical compositions of selected materials and the sizes and shapes of particles. The overall distribution of particles had the biggest impact on the overall quality of UHPC. The shapes of particles affected the consistency between UHPC samples. Factors affecting the workability and early age strength of UHPC were directly related to the rate of hydration, while the size and distribution of particles affected the magnitude of mixing energy required.

Filamentous eukaryotic fungi are ubiquitous in soil habitats. Long filaments, called hyphae, of diameter 1–30 μm form a network called mycelium. The mycelium grows into and breaks down surrounding organisms to provide nutrition for the fungus. Techniques have been developed that introduce fungal spores into a cellulosic matrix, permit the mycelium to grow and bind together the particles of the matrix, resulting in a mycelium-based composite (MBC). The growth is stopped by effectively “killing” the fungus, usually by heating to 80 °C or above. Some of the key advantages of MBCs compared to conventional materials include their low-embodied carbon footprint, the potential to valorize waste agricultural and wood materials, the ability to manufacture these bio-composites locally, and the potential to bio-degrade the bio-composites at the end of life (i.e. they can be composted). Most mycelium composites to date have been used for insulation or packing material applications. More recently, an MBC that incorporates a cotton textile, hemp particles (hurd) and mycelium binder has been developed and is purported to have improved mechanical properties. This paper presents nine cylinder compression tests and one beam bending test. This mycelium composite has an average compressive strength of 0.7 MPa (based on a 0.2% off-set value) and average compressive secant modulus E = 37 MPa. On the other hand, it is relatively low density (average 285 kg/m³). The stress–strain response is highly non-linear, even at strains below a 0.2% off-set yield stress. It exhibits hysteretic behaviour, and repeated load cycles lead to permanent strain. The composite has a higher initial stiffness in bending (2.7 times greater), but a lower yield moment (58% less), than would be expected based on the compressive stress–strain response. This may be due to differences in the load sharing between the textile, hurd, and mycelium under different loading regimes.