Strain-hardening Geopolymer Composites Research Articles

Interface bonding properties of polyvinyl alcohol (PVA) fiber in alkali-activated slag/fly ash

This paper presents an experimental study on the interface bonding properties of polyvinyl alcohol (PVA) fiber in alkali-activated slag/fly ash (AASF) pastes. Three interface bonding properties (i.e., the chemical bonding energy Gd, the initial frictional bond strength τ0, and slip-hardening behavior) were determined using single-fiber pullout tests. The microstructure and chemical composition of the reaction products in the fiber/matrix interfacial transition zone (ITZ) and the nearby matrix were also characterized to reveal the influence of PVA fiber to its surrounding matrix. It is found that Gd increases primarily with increasing Ca/(Si+Al) ratio of C-(N-)A-S-H gel. Unlike that in cementitious materials, the inclusion of PVA fiber in AASF pastes promotes the formation of a high-Ca C-(N-)A-S-H phase rather than crystalline portlandite near the fiber surface. This study provides useful guidance for tailoring the interface bonding properties of AASF and also the development of high-performance composites such as strain-hardening geopolymer composites.

Strain hardening geopolymer composites with hybrid POM and UHMWPE fibers: Analysis of static mechanical properties, economic benefits, and environmental impact

With unique ultra-high toughness, strain-hardening cementitious composite (SHCC) has attracted considerable attention. However, environmental and economic concerns have hindered its engineering application due to the high consumption of Portland cement and expensive high-performance fibers. To address this issue, geopolymer concrete and polyoxymethylene (POM) fibers are adopted to replace Portland cement and ultrahigh molecular weight polyethylene (UHMWPE) fibers, respectively, to prepare strain-hardening geopolymer composite with hybrid POM and UHMWPE fibers (POM/PE-SHGC). Static mechanical properties, economic benefits, and environmental impact of POM/PE-SHGC with different POM fiber replacement ratios are investigated. Axial compression and tensile tests on POM/PE-SHGC with different POM fiber replacement ratios (0%, 25%, 50%, 75%, 100%) are conducted to investigate the effect of different POM fiber replacement ratios on the static failure mode, tensile crack development, compression behavior, and strain-hardening behavior of POM/PE-SHGC. In addition, Carbon emissions and energy consumption of POM/PE-SHGC were estimated and compared with SHCC. An evaluation method that comprehensively considers environmental and economic benefits and mechanical properties is proposed. The results indicated that under the condition of a total fiber volume fraction of 2%, POM/PE-SHGC with a POM fiber replacement ratios under 75% exhibited good strain-hardening behavior. The compressive strength, ultimate compressive strain, and ultimate tensile strain of POM/PE-SHGC reached a maximum at a POM replacement ratios of 50%, except for a decrease in its tensile strength. Furthermore, the cost, carbon emissions and energy consumption of POM/PE-SHGC was significantly lower than that of SHCC. This study verified the feasibility of producing green, high-performance SHGC and promoted the engineering application of this material.

Optimization of fiber aspect ratio for 90 MPa strain-hardening geopolymer composites (SHGC) with a tensile strain capacity over 7.5%

This study developed high-strength strain-hardening geopolymer composites (SHGC) containing 2% (by volume) polyethylene (PE) fibers. A high-strength geopolymer matrix with a compressive strength of over 100 MPa was achieved using liquid crystal display glass powder and ground granulated blast furnace slag. To determine the optimum aspect ratio of PE fibers, five different types of PE fibers with aspect ratios ranging from 300 to 900 were considered. The average bond strength of PE fibers in the high-strength geopolymer matrix was 1.55 MPa, similar to that of high-strength cement matrices. The PE fibers with higher aspect ratios were more effective for improving the tensile performance of high-strength SHGC than those with lower aspect ratios, and a robust strain-hardening characteristic with saturated micro-crack patterns was obtained when the fiber aspect ratio exceeded 600. The energy-based pseudo strain-hardening index (Jb′/Jtip) was found to be 25.3 at a fiber aspect ratio of 600, and it increased to 104.3 with the increase in the fiber aspect ratio up to 900. The best tensile performance—tensile strength of 5.73 MPa, strain capacity of 7.58%, and strain energy density of 309.6 kJ/m3—was achieved in the high-strength SHGC reinforced with PE fibers having an aspect ratio of 900.

Feasibility of developing strain-hardening geopolymer composite plates by hot-pressing method

Fly-ash-based strain-hardening geopolymer composite (SHGC) plates were manufactured by hot-pressing on a plate vulcanizing press machine. The strain-hardening behavior of SHGC was examined by direct tensile tests, displaying an ultimate strain more than 4%. The flexural behavior of SHGC was investigated by centrally loaded square plates. The parameters under investigation included liquid-to-solid ratio, age, temperature, pressure, fiber type and content. The influence of these parameters on load carrying capacity, deflection, toughness and failure mode were analyzed. The results showed that the load carrying capacity increased with temperature, pressure and age, while the ductility decreased slightly. The specimens gained 66% and 89% load carrying capacity at 1 d and 7 d, respectively, in the reference to that for 28 d. The plates reinforced with 1.5% by volume fiber gave performance comparable to that for 2%. The plates with oiled polyvinyl alcohol (PVA) fibers are around 20% higher than those with non-oiled PVA fibers in maximum load and deflection under flexure. This study has proven the feasibility of fabricating high-ductility SHGC plates by a hot-pressing machine readily available from the market, which could be a preferred option for applications in precasting industry.

A critical review of engineered geopolymer composite: A low-carbon ultra-high-performance concrete

“Bendable concrete” or, more formally, engineered cementitious composite (ECC) is a special type of ultra-high-performance concrete that possesses strain-hardening properties with high tensile ductility. Despite their improved performance, ECCs contain about two to three times higher ordinary Portland cement (OPC) content than conventional concrete. Given the high carbon footprint of OPC, the environmental impact of ECCs is significant. Although copious research has been conducted on replacing OPC in ECCs with low-carbon binders, e.g., blended cements, such materials can only partially replace OPC in ECCs. One promising alternative that can fully replace OPC in ECCs is geopolymer, an alkali-activated cement. Research on replacing OPC with geopolymers in ECCs started about a decade ago, and such composites have become known in the literature as Engineered Geopolymer Composites (EGCs) or Strain-Hardening Geopolymer Composites (SHGCs). This paper provides an extensive literature review of all published studies on EGCs to date. The paper starts with a scientometric analysis using science mapping to provide a holistic overview of the current research progress on EGCs. Comparisons between EGCs and ECCs in terms of their pseudo-strain-hardening behavior and mechanical properties are provided. The effects of varying parameters related to the matrix, fibers, and curing conditions, on the performance of EGCs, are also discussed. Finally, durability, self-healing, and environmental impact, among other aspects of EGCs, are highlighted. The conducted review revealed the promising potential of EGCs as low-carbon and ultra-high-performance concretes. However, research on EGCs is still developing, and further investigations are needed before the full potential of EGCs can be realized.

Behaviour of strain hardening geopolymer composites at elevated temperatures

Strain hardening geopolymer composite (SHGC) is a sustainable fibre-reinforced material that exhibits superior strain-hardening and multiple cracking behaviour under tension. The geopolymer binder synthesised through alkali-activation of aluminosilicate precursors sourced from industrial by-products is chemically stable at elevated temperatures. This paper presents a systematic experimental study on behaviour of fly ash-slag based SHGC reinforced with polyvinyl alcohol (PVA) fibres exposed to elevated temperatures up to 800 °C through weight loss, uniaxial compressive, ultrasonic pulse velocity (UPV) and uniaxial tensile tests as well as thermal analysis using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and derivative thermogravimetry (DTG), X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). Results indicate that the compressive strength of SHGC is increased until exposure to 250 °C, followed by a decline up to 600 °C and a regain at 800 °C. The strength gain mechanisms include further geopolymerisation that refines the microstructure, fibre bridging action and sintering that densifies the binder gels, while the strength reduction can be attributed to the damage induced by internal moisture removals and evaporation of fibres, decomposition of calcium compounds, and empty channels introduced by vanished fibres. Besides, the SHGC specimens exposed up to 250 °C exhibit high ductility performance with saturated microcracks when subjected to uniaxial tension, whilst those at 105 °C demonstrate the best strain-hardening degree because of the desired fibre-matrix interaction and enhanced matrix strength. Moreover, no spalling can be observed in SHGC due to its relatively porous structure.

Influence of copper slag on Mechanical, durability and microstructural properties of GGBS and RHA blended strain hardening geopolymer composites

To enhance sustainability, two major slag based industrial wastes viz., Ground Granulated Blast furnace Slag (GGBS) and copper slag were adopted in this study to develop Engineered Geopolymer Composites (EGC) replacing commonly used fly ash and silica sand. A small fraction of agricultural waste viz., Rice Husk Ash (RHA) was also used as a part of the binder which proved to improve the efficiency of GGBS in geopolymer composites. Higher volume of industrial wastes were intended to reduce the impacts of CO2 and land degradation due to cement production and dumping of industrial wastes respectively. PolyVinyl Alcohol (PVA) fibres and sodium-based activators were considered from the literatures to impart the strain-hardening and geo-polymerization reaction respectively. Dosages of activator, superplasticizer and extra water contents were optimized based on the workability test. Keeping the other mix-design factors as constant, the effect of the content of copper slag in proportion with Manufactured Sand (M Sand) in the proposed EGC mixtures were studied in this research with respect to mechanical, durability and microstructural parameters. Content of copper slag anything above 60% resulted in poor bonding and segregation. Replacement of copper slag upto 40% produced the maximum compressive strength of 39.6 MPa after 90 days of ambient curing conditions. The best among the mixes was M60C40 (40% copper slag) which recorded about 1.98 MPa and 12.75 MPa of tensile and flexural strength respectively with a maximum tensile strain capacity of about 6.12%. The specimens were excellent in resisting the seawater attack which did not show any significant weight or strength loss whereas sulphate attack showed considerable strength loss upto 5%. During the microstructural investigations with Scanning electron microscope (SEM) and Energy Dispersive X-ray analysis (EDAX), the effects caused by the aggressive environments could be clearly visualized with the observations towards the internal physical structure and intensity of chemical elements respectively.

Experimental study on static and dynamic properties of fly ash-slag based strain hardening geopolymer composites

Strain hardening geopolymer composite (SHGC) is a special group of fibre reinforced geopolymer composites, which exhibits ultra-high ductility and multiple microcracks under tension. This paper presents an experimental study on the effect of polyvinyl alcohol (PVA) fibre content (0%, 1%, 1.5%, and 2%) on engineering properties of fly ash-slag based SHGC cured at ambient temperature in terms of flowability, drying shrinkage and mechanical properties, with a special focus on strain hardening behaviour and dynamic compressive behaviour. Single-crack tension test and three-point bending test were conducted to determine the micromechanical properties of SHGC, dynamic properties of which were explored using Split Hopkinson pressure bar. Results indicate that the flowability, drying shrinkage and compressive strength of SHGC reduce with the increase of PVA fibre content, while the tensile strength and ultimate strain of SHGC under uniaxial tension are significantly improved because of the fibre bridging effect. The dynamic compressive behaviour of SHGC is strongly associated with the strain rate. The dynamic compressive strength of SHGC with various PVA fibre dosages is increased by 9.26–29.97% and 41.59–69.78% as the strain rate increases from 50 s−1 to 100 s−1 and 150 s−1, respectively. Overall, the mixture containing 1.5% PVA fibre can be regarded as the optimal mixture for SHGC considering static mechanical properties and dynamic compressive behaviour.

Enhancing the Static and Dynamic Properties of Fly Ash-Slag Based Strain-Hardening Geopolymer Composites Using Recycled Tyre Steel Fibres

Enhancing the Static and Dynamic Properties of Fly Ash-Slag Based Strain-Hardening Geopolymer Composites Using Recycled Tyre Steel Fibres

Influence of elevated temperatures on the residual and quasi in-situ flexural strength of strain-hardening geopolymer composites (SHGC) reinforced with PVA and PE fibers

Interest in geopolymers (GP) has been continuously increasing due to their comparable-to-concrete mechanical properties and enhanced durability characteristics. Despite their chemical stability at high temperatures, the brittle nature of geopolymers may prevent their use in applications requiring inelastic deformability, e.g., strengthening layers or elements subjected to dynamic loading. Strain-hardening geopolymer composites (SHGC) made with short high-performance fibers appear as a promising new class of materials that can yield a quasi-ductile tensile behavior under increasing loading. This article assesses distinct types of metakaolin-based SHGC with respect to the temperature effects on their mechanical performance. In particular, the efficiency of Na and K alkali solutions is compared when combined with short fibers made of polyvinyl alcohol (PVA) and ultra-high molecular weight polyethylene (PE). Flexural properties were obtained for all material variations after exposure to a temperature of 100 °C or 200 °C in cooled down state (residual) and in hot state (quasi in-situ). Additionally, thermogravimetry (TGA), mercury intrusion porosimetry (MIP), dilatometry, and environmental scannning electron microscopy (ESEM) techniques were used. At room temperature, NaGP-based composites showed higher flexural strength due to the superior properties of the matrix and crack-bridging performance of the fibers. All quasi in-situ tested specimens demonstrated higher losses in strength and ductility when compared to the residual ones. This can be traced back to higher deformability of the fiber when in hot state. As opposed to PVA, the PE fibers yielded a higher thermal sensitivity in terms of crack-bridging capacity due to their lower melting temperature.

Effect of recycled tyre polymer fibre on engineering properties of sustainable strain hardening geopolymer composites

Strain hardening geopolymer composite (SHGC) processing superior tensile ductility and multiple cracking is a promising alternative to traditional ductile cementitious composites whereas the extremely high cost of polyvinyl alcohol (PVA) fibres limits its large-scale application. This paper presents a feasibility study of replacing PVA fibres with recycled tyre polymer (RTP) fibres to reduce the material cost of fly ash-slag based SHGC and ease the pressure on environmental impact induced by the vast amount of waste tyres, focusing on the influences of PVA fibre content (1.0–2.0% by volume) and RTP fibre replacement dosage (0.25–1.0% by volume) on the engineering properties especially uniaxial tensile behaviour, microstructure, material cost and environmental impact. Results indicate that the incorporation of RTP fibres into SHGC can lessen the loss in flowability and compressive strength due to the addition of PVA fibres. The drying shrinkage of SHGC containing RTP fibres is effectively reduced by about 35.69% and 17.33% as compared with the plain matrix and SHGC containing 2.0% PVA fibre, respectively. Although the presence of more RTP fibres diminishes the uniaxial tensile behaviour of SHGC, the cost and embodied energy of SHGC utilising RTP fibres are reduced by up to 34.52% and 16.23%, respectively. SHGC with 1.75% PVA fibre and 0.25% RTP fibre can be considered as the optimal mixture as it provides adequate engineering properties including a tensile strain capacity of around 2.5%, lower material cost and lower environmental impact compared to the typical SHGC with 2.0% PVA fibre.

Artificial intelligence for the compressive strength prediction of novel ductile geopolymer composites

Engineered Geopolymer Composites has proved to be an excellent eco-friendly strain hardening composite materials, as well as, it exhibits high tensile strain capacity. An intelligent computing tool based predictive model to anticipate the compressive strength of ductile geopolymer composites would help various researchers to analyse the material type and its contents; the dosage of fibers; producing tailor-made materials; less time consumption; cost-saving etc., which could suit for various infrastructural applications. This paper attempts to develop a suitable ANN based machine learning model in predicting the compressive strength of strain hardening geopolymer composites with greater accuracy. A simple ANN network with a various number of hidden neurons have been trained, tested and validated. The results revealed that with seventeen inputs and one output parameters respectively for mix design & compressive strength and thirteen hidden neurons in its layer have provided the notable prediction with R2 as 96% with the RMSE of 2.64. It is concluded that a simple ANN model would have the perspective of estimating the compressive strength properties of engineered geopolymer composite to an accuracy level of more than 90%. The sensitivity analysis of ANN model with 13-hidden neurons, also confirms the accuracy of prediction of compressive strength.

Fracture properties and microstructure formation of hardened alkali-activated slag/fly ash pastes

This study presents a comprehensive experimental investigation on the fracture properties of hardened alkali-activated slag/fly ash (AASF) pastes in relation to the microstructure formation and reaction product composition. The main reaction product in AASF is C-(N-)A-S-H gel along with minor hydrotalcite phase, with the polymerization of C-(N-)A-S-H gel substantially governed by its Ca/Si ratio. Strong positive correlations are identified between the Ca/Si ratios of C-(N-)A-S-H gel and the fracture properties KIc (Jtip), whereas, the compressive strength of AASF pastes is primarily determined by its capillary porosity (>0.01 μm). The disagreements between the Ca/Si ratios and corresponding intrinsic mechanical properties of C-(N-)A-S-H gel as proof by contradiction indicate that the fracture properties KIc (Jtip) of AASF pastes could be dominated by a cohesion/adhesion-based mechanism. These findings provide promising guidance for fine-tuning the fracture properties of AASF and also advise on the tailoring strategies for high-performance composite such as strain-hardening geopolymer composite.

Soft Computing Techniques for the Prediction and Analysis of Compressive Strength of Alkali-Activated Alumino-Silicate Based Strain-Hardening Geopolymer Composites

A futuristic class of concrete that has ductile nature with zeroed cement and eco-friendly materials is popularly known as Engineered Geopolymer Composites (EGC). Research on strain-hardening geopolymer composites have started a decade back and there is an extensive opportunity for utilizing this kind of eco-material in the construction sector for sustainable development. The focus of this article is to develop predictive models for the compressive strength of EGC with the objective of assisting the experimental researches and to analyze the type of locally available eco-materials that could be adopted in developing the novel ductile geopolymer composites for structural applications. A database has been created with ten mix-design factors, including material contents and curing conditions as inputs. Three soft-computing tools viz., Artificial Neural Networks (ANN), Response Surface Methodology (RSM) and Gene-Expression Programming (GEP) have been exercised to create, train and validate the predictive models. Also, a critical comparative analysis has been performed. The accuracy of predictive models is tested with regression tools. Among these artificial intelligence tools, the RSM model has shown an accuracy level of 96% with the least RMSE of 2.8 and the ANN [10:8:1] model has shown 93% accuracy with RMSE 3.4. Only 80% accuracy has been shown for the GEP model with RMSE 6.2. The sensitive parameter in concrete composites is compressive strength where the prediction error should be minimum. This article concludes that the developed ANN and RSM models worked effectively in prediction whereas GEP is comparatively less accurate, which can be improved when influencing mix-design parameters are lesser.

Effect of sand content on engineering properties of fly ash-slag based strain hardening geopolymer composites

Strain hardening geopolymer composite (SHGC) is a tailored group of sustainable high-performance fibre reinforced geopolymer composites with strain hardening behaviour and ultra-high ductility. This paper experimentally investigates the effect of fine silica sand content (0–40% by weight of the geopolymer binder) on engineering properties of fly ash-slag based SHGC cured at ambient temperature, including workability, setting time, drying shrinkage, compressive strength, and flexural strength as well as deflection hardening behaviour that is particularly emphasised. The results indicate that all SHGC specimens exhibit deflection hardening characteristics along with large deflection and multiple microcracks distributed over the tensile side of the specimens. The widths of microcracks are within 300 μm and mostly smaller than 45 μm. The flowability, setting time, drying shrinkage and compressive strength of SHGC reduce with the increase of sand content at early ages up to 28 d. However, at 28 d, the incorporation of sand up to 20 wt% increases the flexural strength and toughness of SHGC, but the further increase of sand content up to 40 wt% results in a decrease in flexural strength and toughness.

Engineering properties of strain hardening geopolymer composites with hybrid polyvinyl alcohol and recycled steel fibres

Strain hardening geopolymer composite (SHGC) is an alkali-activated material reinforced with randomly dispersed short fibres, which exhibits high ductility and strain hardening and multiple cracking behaviour. This paper presents an experimental study on the effect of hybrid polyvinyl alcohol (PVA) and recycled tyre steel (RTS) fibres on engineering properties of fly ash-slag based SHGC cured at ambient temperature, including flowability, setting time, drying shrinkage, compressive strength and flexural behaviour in terms of stress–deflection response, first-crack strength and flexural strength, flexural toughness and toughening mechanisms. Four mix proportions of specimens with various volume fractions of hybrid PVA and RTS fibres including 1.5% PVA, 2% PVA, 1.75% PVA + 0.25% RTS and 1.5% PVA + 0.5% RTS were considered. The results indicated that the hybridisation of PVA fibre with RTS fibre led to a significant reduction in flowability, setting time and flexural strength of SHGC. However, the resistance to drying shrinkage and compressive strength of SHGC were greatly improved. Moreover, all specimens exhibited the expected deflection hardening behaviour with multiple stable microcracks formed over the tensile face of specimens under four-point bending. The addition of RTS fibre resulted in reduced crack widths in specimens where over 90% of cracks had a width of smaller than 60 μm. The mixture containing 2.0 vol% PVA fibre can be regarded as the optimal mixture for SHGC considering the strengths and deflection (or strain) hardening behaviour.

Tensile behavior of strain-hardening geopolymer composites (SHGC) under impact loading

Strain-hardening geopolymer composites (SHGC) exhibit remarkable ductility, crack control and high energy dissipation capacity when subject to quasi-static tensile loading. However, their mechanical performance under dynamic loading has not yet been explored. A comprehensive assessment of possible rate effects is required to facilitate a targeted material design for various practical applications. The article presents the results of an experimental investigation on the mechanical behavior of two types of SHGC under both quasi-static and impact tensile loading. The composites were reinforced with 2% of either short polyvinyl alcohol (PVA) fiber or ultra-high molecular-weight polyethylene (UHMWPE) fiber. The experiments were performed both at the composite scale and at the fiber level. The impact tests on the plain geopolymer matrix and SHGC were performed in a gravity-driven split-Hopkinson tension bar (SHTB) at strain rates of up to 300 s−1. The tests were accompanied by optical measurements to assess specimen deformation and multiple cracking by means of Digital Image Correlation (DIC). The dynamic fiber-matrix bond properties were investigated in a miniature split Hopkinson bar. Both under quasi-static tensile loading and impact tensile loading, the SHGC made with UHMWPE fibers exhibited superior mechanical performance compared to the composite made with PVA fibers. When comparing the impact tensile performance of SHGC with normal-strength SHCC from previous studies, SHGC demonstrated higher dynamic tensile strength and energy dissipation capacity, making SHGC promising for strengthening/prospective applications against highly dynamic actions.

On the mechanical performance of K- and Na-based strain-hardening geopolymer composites (SHGC) reinforced with PVA fibers

Strain-hardening cementitious composites (SHCC) are known by their high deformation capacity due to a multiple cracking tolerance under increasing tensile loading. While SHCC have been well investigated, the design of geopolymer (GP) composites in the same context is not sufficiently understood, mainly due to varying precursor materials used in previous studies. In this work, two metakaolin-based GP mixtures were produced, using K and Na as alkali sources. The incorporation of fine-grained sand was extensively investigated to evaluate its compatibility with both strain-hardening geopolymer composites (SHGC) reinforced with short polyvinyl-alcohol (PVA) fibers. Their mechanical properties were analyzed by means of compression, bending, and tension tests. Digital Image Correlation (DIC) was used to evaluate the fracture mechanisms under uniaxial tension. Particle size distribution (PSD), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and mercury intrusion porosimetry (MIP) were conducted. Additionally, single-fiber pullout tests with subsequent Environmental Scanning Electron Microscopy (ESEM) were carried out. NaGP composites, reinforced with fine-grained sand, yielded improved mechanical responses, reaching a strain capacity of approximately 4.5%, with enhanced multiple cracking, as opposed to the lower performance observed for KGP composites, that did not present a typical strain-hardening curve when in presence of fine-grained sand, but a strain-softening one. When compared to typical SHCC responses, Na-based SHGC showed a mechanically improved multiple cracking behavior, indicating the potential of this material for a wide range of applications, such as dynamic loading and requirements of long-term durability.

Micromechanics-guided development of a slag/fly ash-based strain-hardening geopolymer composite

Strain-hardening geopolymer composite (SHGC) lately emerged as a promising alternative to traditional strain-hardening cementitious composite with added advantages of industrial by-product utilization and enhanced sustainability. However, as the design of SHGC requires multi-factor optimization, the application of traditional trial-and-error method is inefficient and hinders the development of this material.This paper aims at the development of a slag/fly ash-based SHGC with low slag content using a micromechanical model to guide the composite mixture design. To this end, experimentally characterized physical properties of fiber, matrix and interface are used as input for the micromechanical model, which serves as a predictive tool for the tensile performance of SHGC. Following the guidance, a slag/fly ash-based SHGC with tensile strain capacity of 4.8% and ultimate tensile strength above 3.8 MPa was systematically developed. The feasibility and effectiveness of using micromechanics as the design basis of SHGC are demonstrated and experimentally verified.

Mechanical behavior of strain-hardening geopolymer composites reinforced with natural and PVA fibers

Geopolymers have been increasingly used in civil construction. They are obtained through the mixture of an aluminosilicate with an alkali medium, and its properties may vary according to processing conditions. They demonstrate a brittle behavior, and several types of fibers can be used as reinforcement in distinct forms. This study presents an experimental evaluation of GP-composites reinforced with natural and synthetic fibers, using a mixture based on metakaolin and sodium. Compression, tensile (analyzed by Weibull statistics) and pull-out tests were performed. The microstructure was investigated through scanning electron microscopy (SEM). All composites exhibited a strain-hardening behavior with multiple cracking formation.