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The Disposal of Scrap Tires has Resulted in Major Environmental Problems Worldwide. Therefore, Utilizing Scrap Tires as Crumb Rubber is being Used in Brick Production to Improve the Properties of the Bricks as well as to Provide Feasible Waste Management of Scrap Tires. this Study Presents the Literature Research on Utilizing Crumb Rubber in Bricks Manufacturing. the Review Summarized the Manufacturing Process of Producing Crumb Rubber and then Documented the Application of Crumb Rubber in Masonry. the Results Show that the Compressive Strength of Masonry Bricks Decreases with the Increased Percentage Substitution of Crumb Rubber as a Replacement of Fine Aggregate while the Water Absorption Increased. Moreover, the Addition of Crumb Rubber in Masonry Applications Reduce the Density which Produce Lightweight Masonry Products. Generally, the Findings Confirmed that the Masonry Bricks Incorporated Crumb Rubber Exhibit Good Physical and Mechanical Properties. the Usage of Crumb Rubber in Bricks Making Helps to Solve Problems Associated with Scrap Tire Management all over the World.

The rapid growth in the construction industry has dictated the utilisation of the eco-friendly materials and recycling of wastes to produce sustainable products. In this study, rubberized concrete interlocking bricks have been developed by utilising crumb rubber (10%) and fly ash (56%) as partial replacements of sand and OPC, respectively. It is aimed to develop mean and characteristic compressive strength correlations of rubberized concrete interlocking hollow and grouted wall systems, corresponding to rubberized concrete interlocking brick and prism strengths. A systematic investigation of 20 rubberized concrete interlocking brick units, 10 hollow and grouted rubberized concrete interlocking prisms and 10 identical hollow and grouted rubberized concrete interlocking wall panels were cast, constructed and tested under compressive load. Results were statistically analysed and the design-charts for the mean and characteristic compressive strength of masonry were used. The results obtained for the strength of rubberized concrete interlocking brick, prism and wall revealed a normal distribution with 5% significant interval. Four types of regression models were proposed for statistical analysis and the best fit model was identified based on r2 (correlation coefficient). The power model for the mean and characteristic strength curves presented the best fit to the sorted data. The cracking pattern and modes of failure of the tested specimens were discussed. The relationships for characteristic strengths of rubberized concrete interlocking masonry hollow and grouted wall were derived in terms of rubberized concrete interlocking unit and prism strength and found to be fkw = 1.533fb 0.290, fkw = 2.178fb 0.337 and fkw = 1.119fp0.659, fkw = 1.023fp0.731, respectively.

Hosting mega event is an opportunity for hosting city to attract investment in construction of new building and facilities and upgrading its infrastructure and transportation network required for the event. This research paper explores the conceptual elements adopted by Roads & Transport Authority of Dubai to deliver sustainable planning of new metro line route 2020. The main objectives considered in the planning phase of the new metro line are increase ridership, penetration to new to new development and existing urban areas and continuity of the service beyond event period, which will last for 6 months from Oct 2020 to April 2021. Different alignment options were examined against selection criteria that consisted of the following elements: transportation & future developments or transit oriented development TOD, route insertion, constructability and sustainability to ensure integration with urban areas. Refereed/Peer-reviewed

This research aims to study the effect of the dosage of anhydrous sodium metasilicate activator on the long-term properties of fly ash-based one-part alkali-activated binders (OPAAB) cured at ambient conditions. Powdered sodium metasilicate activator was utilized in the range of 8–16% by weight of the fly ash in producing the OPAAB. The properties examined are hardened density, compressive strength, flexural strength, water absorption, efflorescence formation, and microstructural analysis. The experimental result revealed that the binders exhibited excellent long-term strength properties. The compressive strength of the OPAAP is well correlated with its hardened density. The pastes were found to exhibit good soundness characteristics over the long-term. The absorption of water decreases with an increase in the activator dosage from 8–12%, and beyond that, the water absorption relatively remains the same. Field emission scanning electron microscope (FESEM) micrograph revealed uniformly formed solid matrices with the micro-crack present were observed in the samples. The larger pore size promotes the crystallization of the resulting hydrate substances (N, C)-A-S-H gel. The initial dissolution of the OPAAP occurred within the first 30 min. At longer age of curing, mixtures with a higher dosage of powdered activator tend to absorb less water. Strength properties beyond 28 days are considered as the long-term strength.

This paper analyses the bond behaviour of steel reinforcement bars in the matrix of nano-silica (NS)-modified self-consolidating engineered cementitious composites (SC-ECC). Presented first is the results of pull-out tests performed on three different diameters (12 mm, 16 mm, 20 mm) sizes of reinforcing steel bar embedded in the matrix. Subsequently, the results of the experiment are used in identifying the bond-slip relationship which explains the interactions between steel bars and matrix. A response surface methodology is applied to develop predictive models which are used to perform multi-objective optimization on bond-slip properties such as bond energy, bond slip and bond strength. Lastly, the experimental and predicted results obtained demonstrate that the developed models are suitable for the interpretation of the bond behaviour of steel bars embedded in the NS-modified cementitious matrix.

Due to its low carbon footprint and the capacity to be used for in situ applications, cast in-situ geopolymers are recognized as a feasible substitute of Portland cement. One of the limiting factors of using geopolymer in concrete sectors is dealing with viscous and dangerous alkaline alternatives, making it hard to adopt for mass concrete manufacturing. The advanced binder comprises of aluminosilicate components and granular sodium metasilicate to which water has been added like OPC. This document reports on the novel experimental method of producing cast in-situ alkali-activated binders using fly ash, ground granulated blast furnace slag (GGBS) and anhydrous sodium metasilicate. The defined method is described with a logical experimental study conducted to examine a feasible manufacturing method for casting in-situ geopolymer production. Replacement concentrations for slag were 0–100 percent by fly ash weight, while activator is used at 8%–16% of the complete binder content. The strengths, absorption rate and microstructural behaviour of cast in-situ alkali-activated pastes were regarded for up to 28 days. The resistance development of one-part/cast in-situ alkali-activated binders was discovered to be comparable to that of OPC. Microstructural assessment disclosed that the incorporation of GGBS in the paste resulted in structural changes of the in-situ geopolymer paste that could be attributed to the creation of C-A-S-H gel owing to the existence of extremely reactive alumina and silica in the source materials. Using the variance analysis, the impact of slag and sodium metasilicate activator on the behaviour of cast in-situ geopolymer pastes was acquired. The defined models were discovered to be important for all P-value reactions of

The analysis of subsurface structures has always remained a challenge for construction engineer, especially the below-grade sulfur storage pit. A sulfur pit temporarily accommodates elemental sulfur extracted from oil refineries through a Sulfur Recovery Unit (SRU) and conveyed further to different transportation systems such as railcars, trucks or barges via a pumping system. The storage pit ensures that the elemental sulfur remains in its molten state, and further, the surrounding soil environment is protected. The operating temperature of below-grade sulfur storage pits range from 250 °F (121 °C) to 300 °F (149 °C) at which molten sulfur is kept in fluid form using submerged heating coils located at the pit base. The hazardous, corrosive and highly acidic environment causes severe concrete deterioration in the sulfur pit. The extensive concrete deterioration reduces the life span of the sulfur pit to even less than 10 years. The sulfuric acid formation is mainly responsible for the corrosive environment in the pit. The progression occurs from crack formation to delamination to spalling of concrete cover to corrosion, which finally degrades the structural durability and integrity. The heavily affected areas within the pit include the soffit of the roof slab and the walls in the headspace regions. This research paper presents the review of the various mechanisms in sulfur pit deterioration supported by industrial case studies and the absence of long-term durability performance in current industrial sulfur pit repair approaches.

Background: High permeable concrete is designed with high porosity, which allows water to pass through it. By considering this ability, it has been widely used for various applications including high permeable road pavement. However, to fully adopt highly permeable road pavement technology is challenging due to high cost and maintenance, besides the present engineers and contractors have insufficient expertise and experience with this technology. Henceforth, the high porosity property is highly favorable for road curb applications especially in the tropical region like Malaysia with high rainfall intensity. Objective: This paper aimed to determine the properties of the concrete experimentally, and propose the optimum mix design of high permeable concrete for road curb. Methods: The flow value and setting time of the cement paste were investigated. Next, the effects of the modified high permeable concrete with varying amount of crumb rubber on compressive strength, permeability and void ratio were also investigated. Results and Conclusion: Results have revealed that the workability of the cement paste increases when the water-binder ratio and the amount of fly ash increase. Meanwhile, an increasing amount of cement ratio and crumb rubber lowers the flow value and consequently leads to lower void ratio and permeability. Besides, it has been found that the higher the compressive strength, the lower the void ratio and permeability of the concrete. The research findings support that using an optimum amount of cement replacement with crumb rubber as an additive may increase the performance a high permeable concrete. Herein, the results indicate that the mix design of the concrete studied has the potential to be applied onto the road curb.

This paper discusses the influence of elevated temperature on the tensile properties (tensile strength, tensile strain, and energy absorption) and microstructure of nano-silica-modified self-consolidating engineered cementitious composites (NS-modified SC-ECC) mixtures. Response surface methodology (RSM) was utilized to develop a design matrix and predictive models and to perform multi-objective optimization for a matrix of mixtures prepared with polyvinyl alcohol (PVA) fiber at 0.5%, 1%, 1.5%, and 2% volume fractions and NS at 0%, 1%, 2%, 3%, and 4% of the weight of cementitious materials at temperatures of 23 °C, 100 °C, 200 °C, 300 °C, and 400 °C. To investigate the influence of elevated temperature on the certain characteristics of NS-modified SC-ECC mixtures, residual compressive strength, tensile properties, and microstructure properties were assessed at elevated temperatures of up to 400 °C for 1 h. Microstructure was examined using scanning electron microscopy before and after the mixtures had been exposed to elevated temperatures; accessible porosity and pore size distribution with cumulative pore volume were measured using mercury intrusion porosity (MIP) to validate the behaviors of the tensile properties and compressive strength of NS-modified SC-ECC mixtures. The results show that the tensile properties of the NS-modified SC-ECC mixtures improve due to pozzolanic reactivity of NS by utilizing the calcium hydroxide (CH) released from cement hydration to produce more calcium-silicate-hydrate (C-S-H) gel, which refines the fiber-matrix and aggregates-matrix interfacial transition zones (ITZ). The pozzolanic reactivity is further facilitated by temperature curing to produce more C-S-H gel, improving the fiber-matrix interactions at elevated temperatures of up to 200 °C. The PVA fiber improves the elevated temperature behavior of the mixtures and prevents explosive spalling behavior even after the incorporation of 2% NS with a PVA fiber volume of up to 2%. The responses considered in the RSM were tensile strength, tensile strain, and energy absorption. The established models showed high degrees of correlation between the responses and independent variables. Optimized tensile properties could be achieved at 2% PVA fiber volume, 1.3% NS, and a temperature of 125.7 °C. The measured absolute deviations (error) between the experimental data and the theoretical (predicted) models’ results for tensile strength, tensile strain, and energy absorption were 2.83%, 4.4%, and 1.68%, respectively.

Conventional bricks are made off from clay with high firing temperature or from cement concrete, but these consume and emit high energy and have environment shortcoming like carbon footprint and raw materials depletion. Researchers have utilized various types of waste materials in the production of bricks to protect the environment and contribute towards sustainable development. This study presents the latest research updates on utilizing waste materials in bricks manufacturing. The study categorized into two groups based on manufacturing method: fired and unfired methods. The review of literature exhibited an obvious potential of the waste materials as partial or total replacement of conventional raw materials where the produced bricks fulfilled the standards requirements. Additional research work is required, not just in the properties and economical parts but also on educating and aware the public about the advantages of utilizing waste materials in bricks manufacturing as well as on developing codes of practices and standards. © 2018 Elsevier Ltd

Researchers have used crumb rubber in the manufacturing of engineered cementitious composites (ECC) as a solution for spalling, however, it reduces the mechanical and physical properties. Therefore, this research reviews the available and related literature reviews on rubberized ECC and its constituent. The role of each constituent in a rubberized ECC mix is also reviewed. It’s concluded that utilizing rubberized ECC helps to solve environmental issues relating to improper disposal of tyres. As a result, fly ash has been the most common substance utilized in rubberized ECC by scholars all over the world over the past years because of its encouraging impacts on rheology, matrix toughness control, and interactive effect between fiber and matrix. It’s also found that the rectification of the crumb rubber drawbacks in ECC is by incorporating a modern method of adopting nano-silica, Polyvinyl alcohol (PVA) fibers, graphene oxide into the rubberized ECC mixes. Therefore, rubberized ECC can be utilized for civil engineering applications, especially with the inclusion of nano-silica and graphene oxide, as a result of its high ductility and low permeability.

Waste tire and fly ash (FA) are two waste materials whose disposal and rapid rate of accumulation are among the pressing sources of concern and threat to the environment. Although much research exists on the use of these materials in cementitious composites, very little literature is available on the effectiveness of combining them in high volumes for concrete production. This work aimed to utilize crumb rubber (CR) from waste tires as a partial replacement of fine aggregate at 15%, 22.25%, and 30% by volume, and high-volume fly ash (HVFA) replacement of cement at 50%, 60%, and 70% (by weight of cementitious materials) to produce high-volume fly ash–crumb rubber concrete (HVFA–CRC). Using the central composite design (CCD) option of the response surface methodology (RSM), 13 mixes were produced with different combinations and levels of the CR and FA (the input factors) on which the responses of interest (compressive, flexural, and tensile strengths) were experimentally investigated. Furthermore, the composite influence of CR and HVFA on the workability of the concrete was assessed using the slump test. The results showed a decline in the mechanical properties with increasing replacement levels of the CR and HVFA. However, up to 22.25% and 60% of CR and HVFA replacements, respectively, produced a structural HVFA–CRC with a compressive strength of more than 20 MPa at 28 days. Response predictive models were developed and validated using ANOVA at a 95% confidence level. The models had high R2 values ranging from 95.26 to 97.74%. Multi-objective optimization was performed and validated with less than 5% error between the predicted and experimental responses.

Emerging as a new technology, carbon fiber-reinforced polymer (CFRP) has been introduced to rehabilitate and strengthen steel structures using an adhesive agent. However, the outdoor service temperature is potentially degrading to the mechanical strength of the adhesive, as well as affecting the bonding of the strengthened steel structure. Therefore, this paper aims to investigate the bond relationship of CFRP-strengthened steel plates exposed to service temperatures. Two types of experiments were conducted to determine the tensile and flexural performance of CFRP-strengthened steel plates. The experiments were designed using a Box–Behnken design (BBD) and response surface methodology (RSM) by considering three parameters: service temperature (25 °C, 45 °C and 70 °C), number of CFRP layers (one, three and five layers) and bond length (40, 80 and 120 mm). The findings show the dominant failure mode transformed from adhesion failure between steel and adhesive interfaces to adhesion failure between CFRP and adhesive interfaces as the service temperature increased. The tensile strength improved by 25.62% when the service temperature increased. Field emission scanning electron microscope (FESEM) analysis proved that the strength enhancement is due to the densification and reduction of the adhesive particle microstructure gaps through the softening effect at service temperature. However, service temperature is found to have less impact on flexural strength. Incorporating the experimental results in RSM, two quadratic equations were developed to estimate the tensile and flexural strength of CFRP-strengthened steel plates. The high coefficient of determination, R2, yields at 0.9936 and 0.9846 indicate the high reliability of the models. Hence, it can be used as an estimation tool in the design stage.

The concrete-filled double skin steel tube (CFDST) is a more viable option compared to a concrete-filled steel tube (CFST) due to consisting a hollow section, while degradation is enhanced simply by using carbon fiber-reinforced polymer (CFRP). Hence, the stabilization of a concrete&rsquo, s ductile strength needs high- performance fiber-reinforced cementitious conmposite. This study investigates the behavior of high-performance fiber-reinforced cementitious composite-filled double-skin steel tube (HPCFDST) beams strengthened longitudinally with various layers, lengths, and configurtion of CFRP sheets. The findings showed that, with increased CFRP layers, the moment capacity and flexural stiffness values of the retrofitted HPCFDST beams have significantly improved. For an instant, the moment capacity of HPCFDST beams improved by approximately 28.5% and 32.6% when they were wrapped partially along 100% with two and three layers, respectively, compared to the control beam. Moreover, the moment capacity of the HPCFDST beam using two partial layers of CFRP along 75% of its sufficient length was closed to the findings of the beam with two full CFRP layers. For energy absorption, the results showed a vast disparity. Only the two layers with a 100% full length and partial wrapping showed increasing performance over the control. Furthermore, the typical failure mode of HPCFDST beams was observed to be local buckling at the top surface near the point of loading and CFRP rapture at the bottom of effect length.

Deep beams are more susceptible to shear failure, and therefore reparation is a crucial for structural reinforcements. Shear failure is structural concrete failure in nature. It generally occurs without warning, however, it is acceptable for the beam to fail in bending but not in shear. The experimental study presented the structural behavior of the deep beams of reinforced concrete (RC) that reinforces the web openings with externally connected carbon fiber reinforced polymer (CFRP) composite in the shear zone. The structural behavior includes a failure mode, and cracking pattern, load deflection responses, stress concentration and the reinforcement factor were investigated. A total of nine reinforced concrete deep beams with openings strengthened with CFRP and one control beam without an opening have been cast and tested under static four-point bending load till failure. The experimental results showed that the increase the size of the opening causes an increase in the shear strength reduction by up to 30%. Therefore, the larger the openings, the lower the capability of load carriage, in addition to an increase in the number of CFRP layers that could enhance the load carrying capacity. Consequently, utilization of the CFRP layer wrapping technique strengthened the shear behavior of the reinforced concrete deep beams from about 10% to 40%. It was concluded that the most effective number of CFRP layers for the deep beam with opening sizes of 150 mm and 200 mm were two layers and three layers, respectively.

Engineered cementitious composite (ECC) was discovered as a new substitute of conventional concrete as it provides better results in terms of tensile strain, reaching beyond 3%. From then, more studies were done to partially replace crumb rubber with sand to achieve a more sustainable and eco-friendlier composite from the original ECC. However, the elastic modulus of ECC was noticeably degraded. This could bring potential unseen dangerous consequences as the fatigue might happen at any time without any sign. The replacement of crumb rubber was then found to not only bring a more sustainable and eco-friendlier result but also increase the ductility and the durability of the composite, with lighter specific gravity compared to conventional concrete. This study investigated the effects of crumb rubber (CR) and graphene oxide (GO) toward the deformable properties of rubberized ECC, including the compressive strength, elastic modulus, Poisson&rsquo, s ratio, and drying shrinkage. Central composite design (CCD) was utilized to provide 13 reasonable trial mixtures with the ranging level of CR replacement from 0&ndash, 30% and that of GO from 0.01&ndash, 0.08%. The results show that GO increased the strength of the developed GO-RECC. It was also found that the addition of CR and GO to ECC brought a notable improvement in mechanical and deformable properties. The predicted model that was developed using response surface methodology (RSM) shows that the variables (compression strength, elastic modulus, Poisson&rsquo, s ratio, and drying shrinkage) rely on the independent (CR and GO) variables and are highly correlated.

Multi-layers of carbon fibre reinforced polymer (CFRP) were used to strengthen engineered cementitious composites (ECC) to study their effects on flexural and tensile strengths. Response Surface Methodology RSM was used to obtain the number of trial mixes. A total of 13 mix designs were suggested with two variables: polyvinyl alcohol (PVA) fibre (0.5 %, 1.25 % and 2.0 %) and number of CFRP (1, 3 and 5 layers). The result showed that the flexural strength of specimens with 0.5 % and 2.0 % PVA fibre was enhanced by more than 40 % and 55 %, respectively, when the CFRP layers were increased to 3 and 5 layers, which subsequently increased the absorption energy of the specimens by more than 20 %. Moreover, the tensile strength of the specimens with 1.25 % and 2.0 % PVA fibre improved by 31 % and 61 %, respectively, after these have been strengthened with 3 and 5 CFRP layers. To validate these results, the experimental responses were analysed and optimised using RSM. The coefficient of determination R2 yielded high values at 0.9647 and 0.9747, which indicated the good agreement of the proposed model to the experimental responses. Consequently, a quadratic model and a 2FI (two-factor interaction) model were developed to estimate the bond behaviour of CFRP-strengthened ECC. Based on these models, the best solution of CFRP strengthening with respect to the present study is to use 2 % PVA fibre and 5 layers of CFRP.

Openings in reinforced concrete (RC) slabs are not commonly prescribed in design codes. Even when they are, they raise concerns regards to the size of the openings and the location of the applied loads. Lack of sufficient information about the load-carrying capacity of the slabs with openings and performance is another concern. Hence, this research addresses the structural behavior of slabs with openings coated with Carbon Fiber Reinforced Polymer (CFRP) sheet. In the experimental part, ten slabs were cast with a dimension of 1000 mm &times, 530 mm &times, 25 mm, among which nine slabs had openings and one slab was without opening (control slab). The configuration of the CFRP sheet includes coating in the form of single, double, and triple layers. Experimental results show that the slab with a triple coating of the CFRP layer offers the maximum resistance towards the loading rate. Moreover, with the increase in CFRP layers, the value of deflection is minimized.

In relation to the use of retrofit materials on damaged constructions, application on earthquake-resistant buildings, and for the strengthening and rehabilitation on weakened regions, there is a need for a more superior material than concrete. Application sites include beam-column joints, corbels, link-slabs, deep beams, support regions and dapped-end areas. Fiber reinforced engineered cementitious composites (FR-ECC) can address this issue, because FR-ECC is one of the composite materials that has high strength, ductility and durability. In order to develop FR-ECC, this study was done to investigate the effect of adding quartz powder on the compressive strength capacity and properties of FR-ECC through the use of polyvinyl alcohol (PVA) and steel fibers. The volume fraction of fiber was set to 0%–2%. To support the friendly environment, FR-ECC uses by-product materials such as fly ash and silica fume, with a cement content less than 600 kg/m3. In terms of the experimental investigation on FR-ECC, this work conducted the fresh property tests showing that PVA fibers have quite an influence on ECC workability, due to their hydrophilic behavior. By adjusting the superplasticizer (SP) content, the consistency and high workability of the ECC mixes have been achieved and maintained. The test results indicated that the PVA and steel fibers-based ECC mixes can be classified as self-compacting composites and high early compressive strength composites. Significantly, addition of quartz powder into the ECC mixes increased the compressive strength ratio of the ECC samples up to 1.0747. Furthermore, the steel fiber-based ECC samples exhibited greater compressive strength than the PVA fibers-based ECC samples with the strength ratio of 1.1760. Due to effect of the pozzolanic reaction, the fibers dispersion and orientation in the fresh ECC mixes, so that the cementitious matrices provided the high strength on the FR-ECC samples. During the compression loading, the bulging effect always occurred before the failures of the fibers-based ECC samples. No spalling occurred at the time of rupture and the collapse occurred slowly. Thus, FR-ECC has provided unique characteristics, which will reduce the high cost of maintenance.

In this study, nano-silica (NS) has been incorporated into self-consolidating engineered cementitious composites (SC-ECC) for improving materials utilization and performance. Accordingly, the experimental results of the influence of nano-silica (NS) and polyvinyl alcohol (PVA) fibre on the high temperature resistance and microstructure of NS-modified SC-ECC is reported. Standard ECC mix (ECC M45) was adopted to develop mix matrix of composites with PVA fibre at 0.5%, 1%, 1.5%, and 2%, while NS at 1%, 2%, 3%, and 4% with the aim of investigating the behaviour of the materials at high temperatures. The NS-modified SC-ECC specimens were considered at various high temperatures up to 400 °C for residual compressive strength assessment using response surface methodology (RSM). While the microstructure of the mix containing 2% each of NS and PVA fibre at a high temperature up to 400 °C were investigated for microstructural properties through mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The incorporation of NS and PVA fibre improved the performance of ECC due to the physiochemical effects and microcracks’ bridging ability of NS and PVA fibres, respectively, which was further confirmed by the microstructural studies. The developed prediction model using RSM shows a strong degree of correlation and predictability between the dependent (residual compressive strength) variable and the independent (NS, and PVA) variables after high temperatures exposure. The multi-objective optimization results revealed that the criteria settings at 2% each of NS and PVA fibre achieved a residual compressive strength of about 101 MPa while optimizing the high temperature resistance up to about 293 °C.

This study investigated the effect of a hybrid of crumb rubber and nano silica on the durability performance (Porosity and Permeability) and skid resistance of high volume fly ash (HVFA) roller com...

In this study, a method for determining the setting time and the porosity of fly ash-based geopolymer binders (FAGPBs) has been established. This method permits a real-time monitoring of the geopolymerisation and hardening progressions. A parallel plate capacitor cell technique was used to determine the dielectric constant e r ' and dielectric loss factor e r ' ' of fresh and hardened mixes. Equivalent model-circuits of the measurement system were developed, and the accuracy of the system was verified. The dielectric properties were monitored at different ages until 56 days over a frequency range of 0.1–60 MHz. The alkaline solution to fly ash ratio, sodium silicate to alkaline solution ratio, and sodium hydroxide solution molarity were varied to study their effects on the dielectric properties. It was found that dielectric properties can provide valuable information when measured in the frequency range of 10–25 MHz. In this range, the dielectric values responded well to the variations with age and with mix properties. The relationships between the dielectric properties and the different physical states and constituent materials of FAGPBs could be used for quality control applications. The e r ' and e r ' ' time plots were effectively utilized to determine the setting time and the rate of geopolymerisation of FAGPBs. Measurements showed a strong correlation between e r ' and porosity; the e r ' values decreased 2.3-fold over a porosity range of 3–15%. The proposed regression models can be further used in determining the porosity of FAGPBs at a high accuracy level.

New hybrid fibre reinforced cementitious composite developed using waste materials in the form of tirewires in combination with the PVA (Polyvinyl alcohol) fibers. The two kinds of fibres have been incorporated in the RSM (Response surface methodology) technique from the Design-expert software to evaluate the hybrid proportion of fibers. The Hybrid fibres in ECC (Engineered cementitious composite), with appropriate quantity of high and low modulus fibers is anticipated to enhance both the tensile strength (modulus of elasticity, bulk strength) and strain capacity (mainly for energy absorption). The fresh properties for self-compacting were satisfied according to EFNARC guidelines and observed that tirewire fibre diminished the workability and was preserved through the addition of PVA and superplasticizer. The hardened properties such as flexural strength, direct tensile strength, modulus of elasticity and shrinkage strain were optimized by developing the model equations through ANOVA (analysis of variance) validation with the more than 95% of significance. The appropriate proportions as 0.5% of tirewire and 1.5% of PVA fibers were obtained. The results revealed that the hybrid proportion of fibres adversely effected on workability and it produced a favourable influence on flexural strength, tensile strength and modulus of elasticity. The PVA fibres helped in increasing the strain hardening portion for the hybrid fibre reinforced engineered cementitious composite (HFRECC) and was able to maintain strain capacity up to 5%. The optimized results were validated experimentally with high desirability value of more than 0.97 and the variation between experimental and optimized results from RSM was found to be less than 5%.

The major problems related to roller compacted concrete (RCC) pavement are high rigidity, lower tensile strength which causes a tendency of cracking due to thermal or plastic shrinkage, flexural and fatigue loads. Furthermore, RCC pavement does not support the use of dowel bars or reinforcement due to the way it is placed and compacted, these also aided in cracking and consequently increased maintenance cost. To address these issues, high volume fly ash (HVFA) RCC pavement was developed by partially replacing 50% cement by volume with fly ash. Crumb rubber was used as a partial replacement to fine aggregate in HVFA RCC pavement at 0%, 10%, 20%, and 30% replacement by volume. Nano silica was added at 0%, 1%, 2% and 3% by weight of cementitious materials to improve early strength development in HVFA RCC pavement and mitigate the loss of strength due to the incorporation of crumb rubber. The nondestructive technique using the rebound hammer test (RHT) and ultrasonic pulse velocity (UPV) were used to evaluate the effect of crumb rubber and nano silica on the performance of HVFA RCC pavement. The results showed that the use of HVFA as cement replacement decreases both the unit weight, compressive strength, rebound number (RN). Furthermore, the unit weight, compressive strength, RN, UPV and dynamic modulus of elasticity of HVFA RCC pavement all decreases with increase in crumb rubber content and increases with the addition of nano-silica. Combined UPV-RN (SonReb) models for predicting the 28 days strength of HVFA RCC pavement based on combining UPV and RN were developed using multivariable regression (double power, bilinear, and double exponential models). The exponential combined SonReb model is the most suitable for predicting the compressive strength of HVFA RCC pavement using UPV and RN as the independent variable with better predicting ability, higher correlation compared to the single variable models. Keywords: Crumb rubber, High volume fly ash, Nano silica, Roller compacted concrete pavement, Ultrasonic pulse velocity, Rebound number

Waste tires contribute badly to the environment on a huge scale as they are bulky, non-biodegradable, and prone to fire and being a shelter for mosquitos and other insects. This paper reports on a novel approach towards the development of rubberized brick by utilizing crumb rubber as the sole fine aggregate in the production of geopolymer interlocking bricks. The response surface methodology (RSM) from Design Experts software has been used to determine the numbers of trial mixes and their corresponding ingredients. A total of thirteen trial mixes were carried out and tested for compressive strength and the RSM model was developed to predict the design mix based on the targeted compressive strength. The mix design was obtained to be an 18 M for NaOH and 0.8 solution to fly ash ratio. The geopolymer interlocking rubberized bricks were then produced and tested for compressive strength, dimension, modulus of rupture, water absorption, initial rate of absorption, and efflorescence. The geopolymer interlocking rubberised bricks presented a low compressive and flexural strength and a high-water absorption capacity. The bricks were rated as non-effloresced and classified as 3rd class bricks which can be used as non-load bearing material. It is recommended to utilize nano silica in order to increase the strength of the brick. Keywords: Rubberized bricks, Crumb rubber, Interlocking bricks, Geopolymer, Response surface methodology

The aim of this study is to evaluate the effects of inclusion nano-silica (also known as nano-SiO2) on the properties of pervious concrete containing fly ash (FA) as a partial replacement to cement. It has been found, for cementitious paste, that incorporating NS leads to reduce the cumulative pore volume by 13.4%. While the compressive strength of NS modified pervious concrete has been improved without adversely affecting its void ratio and permeability. The workability has been adversely affected by the inclusion of NS, which can be enhanced by incorporating the fly ash and superplasticizer. The porosity of cementitious paste has increased as the FA content is increased. These results are in good agreement with SEM results. For the pervious concrete voids ratio, permeability and infiltration rate were decreased against the increase of paste to the aggregate ratio Response surface methodology (RSM) has also been used to develop a model for navigating the design space of NS modified pervious concrete. Models revealed 95% significance of confidence level with difference less than 0.2 between Pred R-Squared value of 0.9515 and Adj R-Squared. The general expression has been developed for all the responses with the different coefficients using the RSM. Keywords: Fly ash, Final setting time, Infiltration rate, Pervious concrete, Nano-silica

This study deals with the development of an environmentally sustainable roller-compacted concrete (RCC) using high-volume fly ash (HVFA) and crumb rubber as partial replacement for cement and fine aggregate respectively, and nano-silica as an additive to cementitious materials. Response surface methodology (RSM) was used to design, develop statistical models, and carry out the optimization for the mixtures using the variables crumb rubber, HVFA, and nano-silica. The responses used for the RSM are compressive, flexural, and splitting tensile strengths. The proposed models demonstrated a high correlation among the variables and responses. An optimised HVFA RCC mix can be achieved by partially replacing 10% fine aggregate with crumb rubber by volume, replacing 53.72% of cement with fly ash by volume, and the addition of 1.22% nano-silica by weight of cementitious materials. Further experimental investigations showed that the HVFA RCC pavement exhibited lower fresh density, Vebe time, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, abrasion resistance, and impact resistance compared to conventional (control) RCC pavement. These effects further escalate with increase in partial replacement of fine aggregate with crumb rubber. On the other hand, nano-silica increases the mechanical properties and performance of HVFA RCC pavement with or without crumb rubber. This is because of the ability of nano-silica to partially mitigate the negative effect of crumb rubber on the properties of HVFA RCC by densifying the interfacial transition zone between the cement matrix and crumb rubber and filling the pores in the hardened cement matrix. Furthermore, nano-silica partially ignited the pozzolanic reactivity of fly ash at early ages which leads to higher performance of HVFA RCC pavement at early age.

Roller-compacted concrete (RCC) is being widely used in highway construction industry (for pavement applications) due to its enormous advantages over conventional concrete rigid pavement. However, ...

In this study, roller compacted rubbercrete (RCR) was developed by partially replacing fine aggregate with crumb rubber (CR) in roller compacted concrete pavement (RCCP) to improve its flexural resistance, ductile behavior and reduces the environmental effect of waste tires. Due to the fact that crumb rubber reduces strength in concrete, the addition of nano silica (NS) to mitigate the loss in strength of RCR is a possible solution. Sixteen mixtures with four levels of CR (0%, 10%, 20%, and 30%) by volume replacement to fine aggregate and four levels of NS (0%, 1%, 2% and 3%) addition by weight of cementitious materials were prepared and tested. Fresh properties including density and Vebe consistency time have been determined. Hardened properties including unit weight, compressive, flexural and splitting tensile strength, elastic modulus, abrasion resistance and water absorption have been investigated. The findings show that CR increases the consistency of RCR. The compressive strength and abrasion resistance of RCR increases with 10% CR and the flexural strength also increases with replacement of up to 20% fine aggregate with CR. Addition of NS was successful in improving the performance of RCR due to its physicochemical effects which have been verified by carrying out microstructural analysis. Mathematical models developed using Response surface methodology for predicting the strengths and water absorption using CR and NS as the input variables shows a high degree of correlation and predictability. The results of multi-objective optimization showed that, an optimum mixture can be achieved with a 10% volume replacement of fine aggregate and 1.13% NS addition by weight of cementitious materials to have a high strength, durable and ductile RCR for pavement applications.

Rubbercrete is made of partially replacing fine aggregate, in normal concrete, with crumb rubber (CR) from scrap tires. Despite several advantages of rubbercrete, one of the most hindering factors on using it in the construction industry is the absence of specific mix design to optimize the mix ingredients. Response surface methodology (RSM) optimization has been incorporated using the design expert to eliminate the difficulty in obtaining the anticipated results. Experimental data of 45 rubbercrete mixtures (from the previous study) have been utilized to develop ANOVA models. These models have also been validated to predict the properties of rubbercrete based on different percentages of CR content and w/c. All models are significant with Prob > F is less than 0.05, and the difference between predicted R-squared and adjustable R-squared is less than 0.2. Also, an experimental validation has been performed for three of the optimized mixtures, and the results have been compared, and the variation in the results have found to be less than 5%. It has been concluded that the optimization can be performed for any target strength with desirability as approximately one by improving the performance, reliability for the product and processes.

This paper proposes a new type of lightweight concrete called bubble concrete, which was developed by mixing concrete with high-strength hollow bodies. In the present study, concave and spherical steel hollow bodies were used not only to form multiple cavities in the concrete but also to transfer internal stresses. Through compression tests, the shape effects and distribution effects of the hollow bodies on the strength and Young’s modulus of concrete were investigated. In addition, the mechanical characteristics of the bubble concrete were simulated by nonlinear elastoplastic finite element analysis to study the stress distribution and failure mechanism. The results indicate that with the proper combination, bubble concrete can reduce its density to 1.971–2.003 g/cm3 (83.3–84.7%, compared to control concrete) and its strength reaches 27.536–28.954 N/mm2.

To avoid explosive spalling during elevated temperature, crumb rubber (CR) is being added to the manufacturing of engineered cementitious composites (ECC). However, the addition of CR particles adversely affects the mechanical properties of ECC. Therefore, to overcome this issue, nano-silica (NS) is added into rubberized ECC mixture as cementitious material additives. Response surface methodology (RSM) has been utilized to optimize the mixtures of the rubberized ECC with variables: CR (0, 2.5, and 5 vol.%), polyvinyl alcohol (PVA) fiber (0, 1, and 2 vol.%), NS (0, 1, and 2 vol.%), and fly ash (0, 25, and 50 vol.%). The experimentally measured responses are flexural strength, direct tensile strength, elastic modulus, Poisson’s ratio, creep, and drying shrinkage. Mathematical models to predict the targeted responses have been developed using RSM. As a result, a high correlation between the factors and responses has been exhibited by the developed models and the accuracy of fit, where less than 9.38% of the variation was found between the predicted and validated results. The experimental results revealed that the rubberized ECC with the incorporation of nano-silica exhibited a higher compressive strength, direct tensile strength, flexural strength, elastic modulus, Poisson’s ratio, and lower drying shrinkage.

An engineered cementitious composite (ECC) is a type of high-performance fibre-reinforced composite developed based on micromechanical principles. To improve the modulus of elasticity and minimise the drying shrinkage in self-compacting (SC) ECC without adversely affecting its ductility, nano-silica (NS) is included in the cementitious composite. Twenty SC-ECC mixtures were proportioned, cast, cured, and tested to determine the fresh and hardened properties by using two variables: polyvinyl alcohol (PVA) fiber and NS particles. Five levels of NS (0%, 1%, 2%, 3%, and 4%) and four levels of PVA (0.5%, 1%, 1.5%, and 2%) were considered. A response surface methodology was used to conduct multi-objective optimisation and develop mix proportions that produce the best response to the compressive strength, modulus of elasticity, and energy absorption. It was found that mixtures with 2% PVA and 1.89% NS produce the most desirable responses.

Introdcution:Engineered cementitious composite (ECC) has gained attention among researchers due to its superior tensile properties. To improve its modulus elasticity, due to absence of coarse aggregate, nano-silica (NS) has been added to ECC mixture.Method:To facilitate the usage of the NS-ECC in the construction industry, using nondestructive tests such as rebound hammer (RH) and ultrasonic pulse velocity (UPV) to predict the compressive strength of NS-ECC is worthwhile. Twenty mixtures with two variables which are four PVA% (0.5, 1, 1.5 and 2) and five NS% (0, 1, 2, 3 and 4) have been proportioned, cast, cured and tested using RH, UPV and then crushed to determine the compressive strength at age of 28 days.Results and Conclusion:Response surface methodology (RSM) has been performed to develop models for predicting the compressive strength of NS-ECC utilizing results from RH and UPV. It has been established that the newly developed models are significant with values of “Prob > F” less than 0.05 and also have variance less than 0.2. Therefore, these models can be used to predict the compressive strength of NS-ECC using rebound hammer or/and ultra-pulse velocity.

Geopolymer system is new binding materials in concrete industry that is produced by the alkaline solution and materials rich in aluminosilicate such as fly ash. The effect of the alkaline solution to fly ash ratios of 0.3, 0.4 and 0.5 on mortar geopolymer properties was an issue in this study. The results showed that the higher alkaline solution to fly ash ratio improves the workability and brings a longer setting time, whereas the lower alkaline solution to fly ash ratio gains the significant compressive strength. It was a similar pattern with conventional mortar used ordinary Portland cement, which the compressive strength at 7 days was 85%-90% for 28 days compressive strength, whereas conventional mortar is only 65%-75%. This was due to the higher reactivity in geopolymer system that was faster than the pozzolanic reaction.

In this study, different types of plasticizers were used to investigate their effects on the fresh and hardened properties of high calcium fly ash geopolymers (HCFA). Modified polycarboxylate polymers (G3) and lignin-based polymers (G1) were used as plasticizing admixtures and the results were compared to the effect of tap water addition. The results showed that all the admixtures used are effective in increasing the workability of the HCFA geopolymers mixtures and the workability increased by 25-48% compared to the control mixtures. However, the use of G3 has adversely affected the strength by a reduction of 20%. While the use of G1 reduced the final setting time by 7% which is critical in the case of HCFA geopolymers where the final setting time occurs within 70 minutes. Water can be considered as the best admixture in terms of cost, setting time, and effect on compressive strength and it can be used where medium workability enhancement is required.

Twenty-seven large-scale beams with dapped-end have been prepared, cast and tested to failure in the three points loading arrangement. One control beam has been designed in accordance with requirement of standard code while the dapped-end reinforcement scheme of other beams has been derived from the control beam. In selected beams, engineered cementitious composites (ECC) has been utilized in the dapped-end region. The test results exhibited that DR is more appropriate and higher capacity than HR in resisting the shear force. In addition, the reinforced engineered cementitious composites dapped-end beams (R-ECC-DEB) showed higher structural performance compared to the normal reinforced concrete dapped-end beams (RC-DEBs). The strength of ECC also has direct effect on the failure capacity of the R-ECC-DEB, in which higher strength of ECC leads to higher failure capacity of R-ECC-DEB.

Engineered cementitious composite (ECC) requires a lot of material tailoring for the desired self-compacting properties at fresh state and controlled crack width with strain hardening behavior at hardened state to be attained. Finding a balance between these two important stages (fresh and hardened) of the composite without compromise on any of the desirable properties is not an easy task. This research was aimed at utilizing the technique of multi-objective optimization in trying to determine an optimal Polyvinyl alcohol (PVA) fiber volume fraction and HVFA replacement of cement (two of the most important ingredients of ECC) to develop a self-compacting HVFA-ECC (SC-HVFA-ECC) with desirable properties at both fresh and hardened stages without compromise. Using the central composite design (CCD) of RSM, 13 mixes of varying combinations of the input factors (PVA: 1–1.5 %, FA: 50–70 %) were developed on which six responses (fresh state: v-funnel time, T500 and slump flow; hardened state: compressive strength, flexural strength and tensile capacity) were investigated. Six response models (5 quadratic and 1 linear) were successfully developed and validated using ANOVA. All the models turned out to have a very high R2 value ranging from 87 to 97 %. The multi-objective optimization yielded optimal values of the variables (PVA: 1.67 % and FA: 53.61 %) and predicted optimized values for the responses. The predicted values were experimentally validated and found to compare very well with the experimental values at less than 5 % error.

Due to its encapsulation capacity and low carbon emission, geopolymer mortar is recognized as a possible substitute for Portland cement. This paper reports an experimental procedure of producing geopolymer mortar using petroleum sludge ash (PSA) and fly ash. Replacement levels of PSA were 0 – 20% by the weight of fly ash, 8 – 16 molarity of NaOH, 1.5 – 2.5 ratio of Na2SiO3 to NaOH were used. The 28 days compressive strength of geopolymer mortar made with 10% PSA was found to be the highest (31 MPa). Using variance analysis, the influence of NaOH concentration, the ratio of Na2SiO3 to NaOH, and PSA on the behavior of geopolymer mortars was acquired. The defined models were found to be significant for p-values

Hypothesis-driven physical examination emphasizes the role of bedside examination in the refinement of differential diagnoses and improves diagnostic acumen. This approach has not yet been investigated as a tool to improve the ability of higher-level trainees to teach medical students.To assess the effect of teaching hypothesis-driven physical diagnosis to pulmonary fellows on their ability to improve the pulmonary examination skills of first-year medical students.Fellows and students were assessed on teaching and diagnostic skills by self-rating on a Likert scale. One group of fellows received the hypothesis-driven teaching curriculum (the "intervention" group) and another received instruction on head-to-toe examination. Both groups subsequently taught physical diagnosis to a group of first-year medical students. An oral examination was administered to all students after completion of the course.Fellows were comfortable teaching physical diagnosis to students. Students in both groups reported a lack of comfort with the pulmonary examination at the beginning of the course and improvement in their comfort by the end. Students trained by intervention group fellows outperformed students trained by control group fellows in the interpretation of physical findings (P0.05).Teaching hypothesis-driven physical examination to higher-level trainees who teach medical students improves the ability of students to interpret physical findings. This benefit should be confirmed using validated testing tools.

Inclusion of crumb rubber from scrap tires in concrete as partial replacement to fine aggregate in production of rubbercrete has provided many beneficial impacts to both environments and concrete. Many properties of rubbercrete are improved compared with conventional concrete. However, drawbacks such as reduction in rubbercrete strengths have limited the application of rubbercrete drastically. Therefore, this paper presents a new method on producing rubbercrete with comparable compressive strength to the reference mixture (0% of crumb rubber) by adding nano silica. Twenty four mixtures, with four levels (0%, 10%, 25% and 50%) of crumb rubber replacement to fine aggregate by volume and six levels of nano silica addition (0%, 1%, 2%, 3%, 4% and 5%), were prepared and tested. The microstructure of these mixtures is also investigated and analyzed. It has been found that the inclusion of nano silica would refine the size of the pores and densify the interfacial transition zone between cement matrix and aggregate in hardened rubbercrete. This has resulted rubbercrete with fair compressive strength compared to conventional concrete.

Including polyvinyl alcohol (PVA) fiber to develop a ductile engineered cementitious composite (ECC) is an effective way to overcome the brittle behavior of conventional concrete and to increase the efficiency of composite slab construction. Two groups of full-scale composite slabs were prepared, cast and tested until failure. Each group consists of three PVA-ECC composite slabs and one control specimen made with normal concrete topping. The first group has been tested with long shear span of 900 mm while for the second group, the shear span was 450 mm. Test results have been analyzed and the longitudinal shear bond strength has been computed using both methods of m–k and partial shear connection (PSC). In addition, comparison with other types of composite slabs using the same profiled steel sheeting was also carried out. The longitudinal shear bond strength was found to be 0.46 MPa and 0.387 MPa using m–k and PSC, respectively, with difference of 15.87%. The results showed that the failure modes of the PVA-ECC composite slabs are ductile with enhanced load carrying capacity. Therefore the use of PVA-ECC composite slabs in the construction industry would consider a better economic solution.

Geopolymers are novel binding materials produced by the alkaline activation of rich aluminosilicate materials. Geopolymer binders are considered as green building materials that have increasing potential to replace the ordinary Portland cement in the concrete industry. This study investigated the alkali solution effects on the physical and mechanical properties of the high calcium fly ash based geopolymers. The parameters involved in this study were the NaOH solution molarity and the Na 2 SiO 3 /NaOH ratio. Three NaOH concentrations (8, 10, and 12 molars) were investigated. The Na 2 SiO 3 /NaOH ratio was varied between 1 and 2.5. The results showed that the studied parameters significantly affected the properties of the produced geopolymer mortars. The workability and setting time were found to decrease by increasing the NaOH concentration or by increasing the Na 2 SiO 3 /NaOH ratio. The influence of the NaOH concentration was higher on the workability and setting time while the Na 2 SiO 3 /NaOH ratio highly affected the compressive strength. The initial setting time was in the range of 45-105 minutes while the final setting occurred quickly after that within 70-115 minutes. Oven curing method resulted in high strength at early ages where all of the mixes were able to achieve more than 75% of the 28 days strength within the first 3 days. The 28-days compressive strength ranged between 60-85 MPa, which promotes the use of the high calcium fly ash for the production of early high strength geopolymer concrete.

Eight large-scale reinforced self-compacted engineered cementitious composite (R-SC-ECC) beams with different steel reinforcement ratios have been designed, prepared, cast, cured, and tested to failure at the age of 28 days. The experimental results have been compared with theoretical values predicted using EC2, RILEM, and VecTor2 models. Results show that failure modes in flexure and shear of R-SC-ECC beams are comparable to that of normal reinforced concrete beam. Nevertheless, contrary to VecTor2, models of EC2 and RILEM are not suitable for predicting reasonable ultimate moments for the beams, while results using VecTor2 model have successfully predicted the failure modes and load-deflection curves for all R-SC-ECC beams. It has been concluded that R-SC-ECC fall in the category of ductility class medium to high which gives advantages of using R-SC-ECC beams in regions susceptible to seismic activities.

The dapped-end reinforcements of a control beam have been designed conforming to requirement of the PCI code. The dapped-end reinforcements of other beams were derived from the control beam that involve the scheme variation of the hanger or diagonal reinforcements. Some selected beams utilize the engineered cementitious composites (ECC) in the dapped-end region. Twenty-seven large-scaled beams with dapped-end have been prepared, cast and tested. All beams were tested under the three-point loading up to failure. To localize effect of the shear failure, the shear span-depth ratio ( a v / d ) of 1.43 has been carried out. Dapped-end beam (DEB) specified in PCI code has nominal shear span-depth ratio ( a n / d ) less than 1, but in this study, several beams use a n / d larger than 1. For analytical purpose, the design equations specified in PCI code have been used for the analysis requirement. By comparing against the test results, the analysis results that using the design equations of PCI code provide a significant difference, in which the mean value of analysis-test results ratio is 0.71. The design equations specified in PCI code were reliable to design the dapped-end reinforcements, but these equations have not yet able to accommodate adequately, in analyzing and predicting the failure load of DEBs that have the dapped-end reinforcements scheme varied.

Waste and industrial by-products, such as crumb rubber and fly ash, are being utilized as raw materials for making various masonry products. Rubberized concrete interlocking brick (RIB) is a newly developed product incorporated 10% crumb rubber, as a partial replacement for sand, and 56% fly ash, as a partial replacement for cement. The study experimentally emphasized understanding the behavior of masonry walls made of the developed rubberized interlocking bricks under out-of-plane load, with and without precompression load. The compressive strength of the developed loadbearing RIB was 18.4 MPa. The results of flexural strength, moment–curvature relationship, displacement responses, joint opening, and failure modes for masonry walls made of the developed RIB under lateral load parallel to the dry bed joints are discussed. An analytical analysis to predict the cracking flexural load is presented and compared with the experimental results. The results show that by increasing the pre-compression load, flexural strength, and moment capacity of the rubberized interlocking masonry walls increased linearly. The lateral displacement was 10.82, 24.99, and 29.69 mm for masonry walls subjected to a 0, 56, and 112 kN pre-compression loads, respectively. Flexural failure along the width of masonry walls with a course opening at mid-height was the dominant failure mode. It can also be concluded that the theoretical cracking flexural load closely matches the laboratory load.

This paper is aimed to investigate the engineering properties of high calcium fly ash-based one-part geopolymer concrete using different paste aggregate ratio (0.57, 0.45 and 0.35) and curing conditions (ambient curing, solar curing, and water curing). High calcium fly ash was activated with anhydrous sodium metasilicate powder at 12% of the total precursor materials and cured at three different curing conditions. Workability, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, Poisson’s ratio, water absorption, and porosity have been investigated. The experimental results showed that the mechanical strength of one-part alkali-activated concrete (OPAAC) increases with the decrease in paste aggregate ratio across all the curing methods considered. The strength growth for ambient and water cured specimens is gradual and almost comparable to the solar cured specimens. Compressive strength of almost 70 MPa was obtained for ambient and water cured OPAAC and 90 MPa for solar-cured OPAAC. The paste aggregate ratio has little effect on the porosity of the OPAAC. Regardless of the curing methods, the developed one-part alkali-activated concrete exhibits excellent deformation and durability properties.

This paper reports the findings of the effect of elevated temperature on the compressive strength and durability properties of crumb rubber engineered cementitious composite (CR-ECC). The CR-ECC has been tested for its compressive strength and chemical resistance test against acid and sulphate attack. Different proportions of crumb rubber (CR) in partial replacement to the fine aggregate and polyvinyl alcohol (PVA) fiber have been utilized from 0 to 5% and 0 to 2%. The experiments were designed based on a central composite design (CCD) technique of response surface methodology (RSM). After 28 days curing, the samples were preconditioned and exposed to high temperatures of 100 &deg, C, 200 &deg, C, 300 &deg, C, 400 &deg, C, 500 &deg, C, 600 &deg, C, 700 &deg, C, 800 &deg, C, 900 &deg, C, and 1000 &deg, C for one hour. Although the residual compressive strength of CR-ECC was negatively affected by elevated temperature, no explosive spalling was noticed for all mixes, even at 1000 &deg, C. Results indicated that CR-ECC experiences slight weight gain and a reduction in strength when exposed to the acidic environment. Due to the reduced permeability, CR-ECC experienced less effect when in sulphate environment. The response models were generated and validated by analysis of variance (ANOVA). The difference between adjusted R-squared and predicted R-squared values for each model was less than 0.2, and they possess at least a 95% level of confidence.

The behavior of rubberized interlocking masonry walls is substantially influenced by the properties of the waste materials used, which makes them behave differently from conventional interlocking masonry systems. Ten each of hollow and grouted walls were constructed using rubberized interlocking bricks and then tested under compressive loading. Rubberized interlocking bricks are made using 10% crumb rubber and 56% fly ash as a partial replacement for fine aggregates and cement by volume, respectively. The structural behavior, including strength, load-deformation performance, stress-strain relations, and failure mechanisms of the tested load-bearing walls have been investigated. The results reveal the ability of rubberized interlocking masonry walls to withstand axial compressive of 3.87 MPa for hollow and 5.75 MPa for grouted specimens, which is approximately 15–20% lower than in conventional interlocking masonry walls. Web splitting, vertical cracking and face spalling were common failure modes for hollow and grouted rubberized interlocking masonry walls. In contrast to conventional interlocking walls under compressive loading, rubberized interlocking walls show increased ductility and undergo measurable post-failure loads with significant displacement due to the presence of crumb rubber, which permits a large expansion of microcracks inside the specimens after failure. Rubberized interlocking walls also tend to have large initial deflections as the bricks settle and the gaps caused by dry joints close.

Despite the excellent beneficial mechanical properties and durability behaviour of cementitious composite, the modulus of elasticity is low due to the absence of coarse aggregate and this has hindered in the lone application in structures. The addition of steel fibres in the form of Tirewire along with the PVA (polyvinyl alcohol) as hybrid fibre in cementitious composite, with proper volume of high and low modulus fibers is expected to improve tensile stresses, modulus of elasticity and meanwhile balancing the strain capacity. The partial replacing the fine aggregate with the crumb rubber is to ensure the dispersion of fibres and to limit the fracture toughness of the matrix to improve the performance. The mix designs have been developed using response surface methodology (RSM). The fresh properties for self-compacting were studied and detected that Tirewire diminishes the workability and was conserved through PVA fibre, crumb rubber and superplasticizer. The various hardened properties such as, direct tensile strength, flexural strength and modulus of elasticity was optimized by developing the model equations through analysis of variance (ANOVA). The results revealed that the Tirewire fibre has enhanced the tensile strength, flexural strength and modulus of elasticity. The optimization mixtures were obtained based on the RSM results and are experimentally validated with the less than 5% of error.