Fly Ash Based Geopolymer Mortar Research Articles

High-temperature resistance of ceramic sanitaryware waste and fly ash-based geopolymer and hybrid geopolymer mortars produced at ambient curing conditions

In this study, five different hybrid geopolymer mortar mixtures were prepared, incorporating two different geopolymers and low percentages of Portland cement (PC), (16.6 % and 33.3 %). In geopolymer mixtures, 100 % ceramic sanitaryware waste (SW) and 100 % fly ash (FA) were used as precursor materials. In hybrid mixtures, the precursor materials include FA+ PC, SW+PC, and FA+SW+PC. The flexural and compressive strengths of mortars were determined up to 56 days to investigate their strength development. Additionally, the mortars were exposed to elevated temperatures up to 800 °C, separately. After the high-temperature exposure, phase (XRD) and microstructure (SEM/EDS) analyses were conducted on the selected mortars. All the hybrid geopolymers had higher flexural and compressive strengths than the geopolymers for all the curing ages. The highest 28-day flexural and compressive strength values of 5.3 MPa and 37.0 MPa were obtained on the mixture where FA+SW+PC precursors were used in equal amounts, respectively. The geopolymer and hybrid geopolymer mortars (containing 16.6 % PC) performed well under the high-temperature effect up to 800ºC. The strength values of all the mortars were obtained higher at 800ºC than at 600ºC. After high-temperature exposure, additional crystalline phases such as gehlenite were detected in hybrid mortars.

Fibre hornification improves the long-term properties of hemp fibre-reinforced fly ash-based geopolymer mortar

The study investigates the impact of the fibres’ hornification, subjected to 5 wetting/drying cycles, on the physical and mechanical properties of short hemp fibre-reinforced fly ash-based geopolymer mortars at distinct ages (1, 2.5 and 18 months) cured under laboratory conditions and additionally of the mortars underwent the accelerated ageing of 10 wet/dry cycles. The study reveals that fibres’ hornification induced fibrillation and fibres' cleaner surfaces, most likely enhancing fibres' dispersion within the matrix. This phenomenon leads to suppressing the degradation of all tested mortar’s properties. Considering the curing under laboratory condition, in the case of the density, the suppression is more pronounced in the long term. After 18 months, the hornificated fibre-reinforced mortar nearly matches the water absorption capacity of the plain mortar. Furthermore, the fibres’ hornification contributes to the enhancement in compressive- and flexural strengths of the reinforced mortar at the age of 18 months. In the long term, by increasing the pre-peak segment of the force-displacement curves, the fibres’ hornification slightly increases the energy absorption capacity of the raw fibre-reinforced geopolymer mortar. In the case of the mortars’ curing under wet/dry cycles, the hornification proves to slightly (10 %) improve the physical (increase in density, decrease in water absorption) and mechanical properties (increase in compressive- and flexural strength, as well as energy absorption capacity) of the fibre-reinforced mortar. Due to the mortars’ exposure to the dry cycles (happen at 60 °C), the further geopolymerisation speeds up, which results in the denser matrix, increase in its compressive- and flexural strengths, but a general fibre/matrix bond deteriorates and therefore the fibre-reinforced mortars’ energy absorption capacity decreases, when compared to their counterpart tested at the same age but cured under laboratory condition.

Bond performance of fly ash-based geopolymer mortar in simulated concrete sewer substrate

Geopolymers have been extensively explored as a promising repair material for deteriorated Ordinary Portland Cement (OPC) concrete elements. However, knowledge of the adhesion performance of geopolymer to concrete substrates is limited. This study investigates the bond performance of low calcium fly ash geopolymer (FAGP) mortar and concrete for holistic acidic environmental conditions, such as in sewer rehabilitation. The bond evaluation was conducted by slant-shear test, performed at different substrate conditions, namely Rough-Dry, Rough-Saturated, Smooth-Dry and Smooth-Saturated, to simulate the in-service condition of a typical sewer pipe wall. The standard OPC repair mortar and a commercially available proprietary geopolymer repair product (P-GP) were evaluated and compared as controls to ascertain the viability of geopolymer for repair application. The shear bond strength of FAGP mortar was found to be in the order of 14 MPa, outperforming OPC and P-GP in all substrate conditions. Even though FAGP bond strength was insensitive to roughened substrate moisture levels, the synergistic effect of smoothness and moisture condition appeared detrimental. The testing of the prototype geopolymer-coated concrete pipe under line loading showed no sign of delamination at the bond plane. OPC and P-GP exhibited a distinct bond separation, which commenced at only 20 % of the ultimate load. The acid resistance and low permeability of FAGP mortar appeared to aid in preserving the repair bond.

On the surface roughness properties of fly ash-based geopolymer mortars with teff straw ash from the image analysis viewpoint

Fly ash (FA)-based geopolymer mortar is being considered for sustainability since it enjoys peculiar properties such as high mechanical properties and environmental benefits. However, the high curing temperatures of FA-based geopolymer mortar play a complex role in its outstanding mechanical behaviour thereby requiring other precursors, such as teff straw ash (TSA). In this study, we develop surface roughness properties of FA-based geopolymer mortars with TSA, where the ambient temperature is used for curing. The surface roughness characteristics of the FA-based geopolymer mortars with TSA exploit the surface roughness simulations from Gwyddion and the approach is demonstrated here in the contexts of spatial, hybrid and amplitude roughness parameters. The results show that some roughness parameters, including Ra and Rq values for FA-based geopolymer mortars with TSA, exhibit significant decreasing trends as the TSA contents increase. However, in comparison with the CA specimens (ambient temperature curing) and CE specimens (elevated temperature curing), the trends among the majority of the roughness parameters for FA-based geopolymer mortars with TSA turn out not to be very good probably due to changes in the internal structures of the mortars. Moreover, without the kurtosis values (Rku) of less than 3, it is easy to demonstrate that all the profiles of the investigated specimens reflect sharp valleys and peaks. The findings of surface roughness properties allow one to grasp the roughness parameters of FA-based geopolymer mortars with TSA. The approach for generating surface roughness properties of FA-based geopolymer mortars with TSA offers significant quantitative and qualitative information required for the bonding of mortar layers.

Development of high-strength geopolymer mortar based on fly ash-slag: Correlational analysis of microstructural and mechanical properties and environmental assessment

Given the insufficient mechanical performance of existing fly ash-based geopolymer mortars under ambient curing conditions, this study is dedicated to developing a high-strength geopolymer mortar that meets the requirements of modern structural engineering. Based on the rheological performance tests of the fresh geopolymer mortar, the evolution of its rheological characteristics was revealed. Through macroscopic mechanical performance tests, the influence of slag content on the compressive and flexural strength of geopolymer mortar was clarified. Employing microstructural performance testing methods such as Thermogravimetric and Mercury Intrusion Porosimetry, the micro-mechanisms behind the improvement of mechanical properties were revealed. Utilizing the grey relational analysis method, a framework was established to analyze the correlation between the microstructural and macroscopic mechanical properties of geopolymer mortar. Additionally, an assessment system for evaluating environmental and economic benefits was developed using statistical analysis methods. The results show that increasing slag content enhances the yield stress and plastic viscosity of geopolymer mortar. Optimizing slag content boosts the compressive strength of fly ash-based geopolymer mortar, reaching up to 88.13 MPa under ambient curing conditions. An optimal amount of slag also promotes gel formation during polymerization, improving the internal pore structure. Furthermore, the content of reaction products correlates more strongly with macroscopic mechanical properties than pore structure characteristics. Geopolymer mortar also presents significant environmental and economic advantages over traditional cement-based materials, with its carbon and economic intensity indices at only 5.50 % and 10.80 %, respectively, of those in cement-based materials.

A comparative investigation of eco-friendly fly ash-based geopolymer mortar produced by using electrical and heat curing: Mechanical properties, energy consumption and cost

This study investigates the eco-friendly fly ash-based geopolymer mortar (GM) production using electrical curing (EC) and heat curing. Within the scope of the study, GM produced using the EC method was compared with GM produced using the heat curing (HC) method in terms of mechanical properties, energy consumption, and cost. The study consists of a preliminary experiment to determine the parameters to be used, mortar experiments using the limited parameters defined in preliminary experiments, and an energy consumption and cost analysis. In the preliminary experiments, different mix designs produced according to different MS modulus and Na2O concentrations were studied to decide an applicable range for temperatures of HC and an applicable range for voltages of EC. In the second stage, EC and HC were compared according to temperature changes in GMs, current changes in GMs, and compressive strength (CS). As a final stage, an energy consumption and cost analysis were performed to compare two curing methods according to the updated dollar-based unit prices for electricity per kWh for industrial uses in various countries in February 2024. Results showed that the MS modulus should be at least 1.2 and the Na2O concentration should be 10 % on average to obtain a workable mortar. The compressive strength of all mortars with any MS modulus increased up to 100 °C and then decreased HC applied samples. Stress values of 20, 25, 30, and 35 volts are applicable and the highest compressive strength values could be obtained with 25 volts, and 6 h of application is sufficient at 25 volts EC. MS module is a key parameter in current and temperature change. In EC application, 30 volts is the threshold value, and when an electrical voltage above 30 volts is applied, the mortar's internal temperature suddenly reaches the peak value and the desired compressive strength results cannot be achieved. According to the cost analysis, it is seen that the HC electricity cost is 6.78 times more than the EC cost. A comprehensive efficiency calculation is strongly recommended for future studies. It has also been concluded that geopolymers could gain strength at much lower voltage values, so they have the potential to consume less electrical energy in comparison to conventional concrete.

Optimizing toughness and cost-effectiveness in one-part geopolymers via fiber reinforcement: A comprehensive investigation of PVA, PE, and glass fibers

This study explores developing and characterizing a one-part geopolymer, an innovative and sustainable construction material. The effects of incorporating polyvinyl alcohol (PVA), polyethylene (PE), and glass fibers (GF) on the toughness of slag and fly ash-based one-part geopolymer mortars were investigated through compressive, three-point flexural, and four-point bending tests. The findings demonstrate that fiber incorporation reduces fluidity and compressive strength due to increased porosity, lower elastic modulus of fibers, and weak interfacial bonding. However, fibers significantly enhance damage resistance and toughness via crack bridging and load transfer mechanisms. Formulations with 2 % PVA fibers and combinations of 1 % PVA with 1 % PE fibers and 1 % PVA mixed with 0.5 % PE and 0.5 % GF demonstrate excellent toughness. Notably, the latter two fiber blends achieve 14 % and 10 % cost reductions, respectively, compared to using only PVA fibers, making them economically viable for large-scale applications. Scanning electron microscopy and X-ray diffraction provided insights into the toughening mechanisms, including crack bridging, fiber pull-out, and enhanced stress distribution within the geopolymer matrix. Digital image correlation techniques further elucidated the fibers' role in improving the post-cracking behavior and structural resilience under load.

Effect of Clay Brick Dust (CBD) on compressive strength of fly ash based geopolymer mortar

Effect of Clay Brick Dust (CBD) on compressive strength of fly ash based geopolymer mortar

Study on the synergistic effects of OPC and silica fume on the mechanical and microstructural properties of geopolymer mortar

This study investigated the synergistic effects of ordinary Portland cement (OPC) and silica fume (SF) in fly ash-based geopolymer mortar (FA-GPM). The research comprehensively evaluated the impact of replacing fly ash (FA) with varying proportions of OPC and SF on the flowability and mechanical properties of the geopolymer mortar (GPM). Furthermore, this study analyzed the interaction mechanisms of these effects by examining the microstructure and hydration products. The results showed that increasing amounts of SF initially enhanced but subsequently reduced flowability, while the inclusion of OPC consistently decreased it. The combination of SF and OPC significantly improved the mechanical performance and microstructure of the GPM. Optimal mechanical performance, with compressive strengths of 37.66 MPa at 7 days and 50.52 MPa at 28 days, was achieved by adding 10% SF and 20% OPC. Microstructural analysis revealed that using OPC and SF together enhanced the dissolution of alumino-silicate materials in the alkaline activating solution, leading to increased polymerization reactions in the GPM. This process resulted in the formation of calcium-alumino-silicate-hydrate (C-A-S-H) gel, sodium-alumino-silicate-hydrate (N-A-S-H) gel, and calcium-silicate-hydrate (C-S-H) gel, creating a denser structure with reduced porosity and enhanced mechanical properties. This study highlights the advantages of incorporating SF and OPC into FA-GPM, providing valuable insights for further research and practical applications of geopolymer materials.

Efflorescence of fly ash-based geopolymer mortars under quasinatural conditions: The relationship between curing temperature, ion transport, and compressive strength

This investigation reports the effect of curing temperatures ranging from 20 °C to 80 °C on the efflorescence of fly ash-based geopolymer mortars under quasinatural conditions. The microstructures of the geopolymers before and after efflorescence were characterized by SEM and MIP, respectively. These characterizations are adopted to further explain the change in compressive strength. The micromorphology and phase assemblage of the efflorescence products were identified by SEMEDS and XRD, respectively, indicating that the significant ions involved in the efflorescence include Ca2+, Na+, and CO32-; then, the concentrations of those ions in the leachate were detected by ICP, AAS, and acidbase neutralization titration, respectively. The results show that low curing temperatures (≤ 50 °C) promote the diffusion of ions into the leachate, while high curing temperatures (> 50 °C) contribute to the transportation of ions towards the drying part for the formation of hollow structured Na2CO3·7 H2O. Although the increase in the compressive strength of the geopolymers resulting from efflorescence decreased with increasing curing temperature, the 50 °C-cured geopolymer exhibited the highest compressive strength during efflorescence. This study provides a reference for mitigating efflorescence and improving practicability in the hydraulic engineering of geopolymers.

Properties of Basalt Fiber-reinforced Lightweight Geopolymer Mortars Produced with Expanded Glass Aggregate

Geopolymers are new-generation construction materials that have attracted attention recently and can be an alternative to cement. In the production of these materials, aluminosilicate powder materials are used together with alkali or acid solutions. Geopolymers have different types of superiorities, such as rapid strength gain, high mechanical properties and good durability. This experimental study investigated the properties of expanded glass aggregate-bearing Class F fly ash-based lightweight geopolymer mortars. The fresh unit weight, water absorption capacity, compressive strength and high-temperature resistance (upon exposure to 900°C) of the mortars were determined. In addition, basalt fiber addition's effects on these properties were investigated. The inclusion ratios of basalt fiber were 0.1%, 0.2% and 0.4% by volume. The compressive strengths of fiber-free lightweight mixture and mixtures, including 0.1%, 0.2% and 0.4% basalt fiber, were found to be 8.2, 8.9, 9.0 and 8.0 MPa, respectively. The compressive strength of all lightweight mortars increased between 61.3% and 76.4% after the high-temperature effect. The results proved that it is possible to produce expanded glass aggregate-bearing lightweight geopolymer mortars with acceptable mechanical properties.

Bacteria-based crack healing of 3D printed PVA fiber reinforced geopolymer mortars

Geopolymers have been regarded as a promising environmentally friendly alternative to cementitious materials in 3D printing. In this study, 3D-printed fly ash based geopolymer mortars containing silica fume were produced with PVA fiber at 0%, 0.5%, 1%, and 1.5% ratios. Cracks were created in the specimens using flexural strength test after 28 days. Then, bacterial self-healing process was applied to the half of cracked samples and the remaining cracked samples were used as control samples. Sporosarcina pasteurii was used for healing. Lastly, the visual inspection, flexural strength, compressive strength, and water absorption analyzes were conducted mechanical properties to evaluate the healing performance of 3D-geopolymer samples containing PVA. In addition, the samples were subjected to microstructural examination using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR) to determine the changes in the microstructural of bacterial based healing. As a result, CaCO3 precipitates, which are the bacterial healing output, filled the cracks and boosted the mechanical characteristics of 3D-geopolymer. The application in 3D-printed PVA fiber reinforced geopolymer mortars of bacterial healing resulted in a significant 36.23% improvement in flexural strength and an 11.57% reduction in the capillary water absorption coefficient compared to the non-healed samples.

Effect of Different Ceramic Waste Powder on Characteristics of Fly Ash-Based Geopolymer

The escalating demand for construction materials driven by rapid population growth has heightened the reliance on cement binders, resulting in increased CO2 emissions from the cement industry. Geopolymers, considered environmentally friendly alternatives, have been explored in various studies to address this challenge. This research specifically investigates the impact of different types of ceramic waste bricks (BT), floor tiles (FT), roof tiles (RT), and sanitary ceramics (ST) on the physical and mechanical properties of fly ash-based geopolymer mortar. To provide a comprehensive understanding, this research examines the compressive strength, mineral phase, chemical bonds, and microscopic evolution of fly ash geopolymer mortar incorporating varying proportions of each ceramic waste type (25% and 50% fly ash replacement). A consistent mixture of Na2SiO3and NaOH was used for the alkaline solution in all formulations. The curing process was carried out at room temperature for 7, 14, and 28 days prior to the compressive strength test. The result revealed that the inclusion of 25% BT experienced higher strength compared to the control sample after 14 days, but the strength became comparable after 28 days at 40.24 MPa. A reduction in strength was evident with the addition of other ceramic components. Moreover, higher incorporation of CWP correlated with a faster setting time for fresh geopolymers. This was also linked to the degree of gel formation, as indicated in the microstructure images. The emergence of plagioclase minerals was evident in all formulations of the geopolymer products under XRD analysis, while the bond of the geopolymer signature, Si-O-T (T = Si or Al), was identified from the infrared spectra. The microstructure of the binder showed a geopolymer matrix alongside unreacted fly ash particles. Overall, CWP replacement up to 25% can be potential in fly ash geopolymer without sacrificing significant strength loss and remaining in the range of normal strength mortar. Doi: 10.28991/CEJ-2024-010-02-06 Full Text: PDF

Effect of initial curing conditions on the durability performance of low-calcium fly ash-based geopolymer mortars

Geopolymer composite production has become an indispensable product to reduce carbon dioxide emissions, which have become an important problem today, and to provide green sustainability. Concerns about the global climate change problem have also accelerated geopolymer studies. This research investigated the mechanical and durability characteristics of low-calcium fly ash (LCFA) based geopolymer mortars with different curing temperatures and times. Two forms of curing conditions were applied; the first one was standard curing at room temperature (20±3°C and RH 65±10%) and the second one was cured in the hot air at 40°C, 60°C, and 80°C for 24h, 48h, and 72h followed by standard curing. After all curing processes, compressive strength, flexural strength, water absorption, void ratio, resistance to elevated temperatures, and freeze–thaw conditions were determined experimentally. In addition, SEM analysis was performed before and after durability tests for comparison purposes. Also, XRD and TGA analyzes were performed. According to test results, curing specimens at longer times and higher temperatures has been shown to increase compressive strength results. The highest compressive strength value was reached at 80°C after 72h of curing. Geopolymer specimens subjected to elevated temperatures (600°C and 900°C) lost a significant part of their strength value. After the freeze–thaw test, LCFA-based geopolymer specimens showed more than 70% resistance. The freeze–thaw resistance of geopolymer samples was positively affected on long-term curing at high temperatures, but high-temperature resistance was impacted negatively.

The influence of microwave curing on the strength of silica fume-added fly ash-based geopolymer mortars

Geopolymer concretes a substitute for traditional Portland cement as a more environmentally sustainable alternative. In addition, one of the most significant advantages of geopolymer concrete is the high setting speed that can be achieved with thermal curing, that is, the short curing period. Research on geopolymer concrete has focused on curing, where curing is usually done with conventional ovens. Microwave curing initiates heat generation at the molecular level, which results in a minimal heat increase on the surface of the specimens compared to traditional thermal curing methods. In addition, it provides internal, rapid, and homogeneous heating and rapid strength development. This study is based on research that examined the effect of microwave cure on the compressive strength of silica füme-modified geopolymer mortar. In the study, sodium silicate and sodium hydroxide were used for activation, and first of all, fly ash substituted geopolymer mortar specimens were subjected to conventional thermal curing in an oven. On the other hand, the mortar specimens with the same composition were subjected to short-duration (10 minutes) microwave curing at power levels of between 200-600 W. When the results were compared regarding compressive strength, void and percent water absorption, UPV, and SEM-internal structure examination, it was revealed that microwave curing could be used faster than the conventional oven curing method in silica füme-added fly ash-based geopolymer mortars. This research can be considered an essential step for further optimizing and popularising geopolymer concrete and microwave curing and proposes a method that should be considered in the future development of more sustainable construction materials.

Impact of Low-Reactivity Calcined Clay on the Performance of Fly Ash-Based Geopolymer Mortar

Availability of aluminosiliceous materials is essential for the production and promotion of geopolymer concrete. Unlike fly ash, which can only be found in industrial regions, clays are available almost everywhere but have not received sufficient attention to their potential use as a precursor for geopolymer synthesis. This study investigates the effectiveness of calcined clay as a sole and binary precursor (with fly ash) for the preparation of geopolymer mortar. Fly ash-based geopolymer containing between 0 and 100% low-grade calcined clay was prepared to investigate the effect of calcined clay replacement on the geopolymerization process and resultant mortar, using a constant liquid/solid ratio. Reagent-grade sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were mixed and used for the alkali solution preparation. Six different mortar mixes were formulated using sand and the geopolymer binder, comprising varying fly ash-to-calcined clay ratios. The combined effect of the two source materials on compressive strength, setting time, autogenous shrinkage, and porosity was studied. The source materials were characterized using XRD, SEM, FTIR, and XRF techniques. Isothermal calorimetry was used to characterize the effect of low-grade calcined clay on the geopolymerization process. The addition of calcined clay reduced the surface interaction between the dissolved particles in the alkali solution, leading to slow initial reactivity. Geopolymer mortar containing 20% calcined clay outperformed the reference geopolymer mortar by 5.6%, 17%, and 18.5% at 7, 28, and 91 days, respectively. The MIP analysis revealed that refinement of the pore structure of geopolymer specimens containing calcined clay resulted in the release of tensional forces within the pore fluid. Optimum replacement was found to be 20%. From this study, the mutual reliance on the physical and inherent properties of the two precursors to produce geopolymer mortar with desirable properties has been shown. The findings strongly suggest that clay containing low content of kaolinite can be calcined and added to fly ash, together with appropriate alkali activators, to produce a suitable geopolymer binder for construction applications.

Use Recycled Glass As Fine Aggregate in Slag-Blended Fly Ash-Based Geopolymer Mortar

Geopolymer has emerged as the potential alternative to Portland cement in recent years. In addition, fly ash and recycled glass are abundant by-products derived from the industry. The purpose of this study was to evaluate the potential of using recycled glass to replace the sand aggregate in slag-blended fly ash-based geopolymer mortar. For geopolymer synthesis, the mixture of water glass (Na2SiO3) and sodium hydroxide (NaOH) solution with a NaOH concentration of 14 mol/l was used as an activator. In the mortar mixture, the recycled glass's investigated replacement level of the sand aggregate was up to 100 %. Using recycled glass (RG) as fine aggregate was seen to increase the mechanical strength compressive strength and flexural strength of mortar after 28 days of curing. Otherwise, there was a reduction in the drying shrinkage of mortar samples with a high recycled glass content of 80 and 100 %.

Time Dependence of Viscosity of Alkali-Activated Fly Ash Based Geopolymer Mortar

FA was used as the raw material, and the net slurry of FA base Geopolymer was set as the control group to study the influence of sand content, gradation, reaction temperature and time on the time dependence of the viscosity of alkali-activated fly ash based geopolymer mortar. The experimental results show that the curing reaction of alkali-activated fly ash based geopolymer mortar was affected by the temperature dependence of fluid viscosity and the activation energy of the chemical reaction, which is relatively complex. This paper will divide the whole polymerization process into three stages to elaborate. The increase of sand cement ratio will increase the viscosity of FA base polymer mortar. If the sand is too coarse or too fine, the viscosity of FA base polymer mortar will increase significantly, and the fine sand has a greater impact on the viscosity of FA base polymer mortar than the coarse sand. Increasing temperature will significantly accelerate the reaction speed and increase the influence of chemical reaction activation energy on the viscosity of the system while the too high temperature will make the viscosity of the system decrease more significantly in the reaction. This study will reveal the intrinsic relationship between the viscosity of geopolymer and the reaction process, the reaction mechanism of the curing process so that the reaction stage can be represented by the viscosity state of the slurry.

Effect of GGBS on Fly Ash Based Geopolymer Mortar at Ambient and Heat Curing

AbstractThis study investigates and shows the effect of incorporation of ground granuated blast furnace slag (GGBS) content in fly ash (FA) based geopolymer mortar by assessing the strength properties of geopolymer mortar in both ambient (25 °C) and heat (60 °C) curing. The percentage of GGBS is varied from 0% to 50% with FA in geopolymer mortar. Sodium silicate (SS) and sodium hydroxide (SH) solutions are used to activate the main binders. For all the mixes the alkali/binder ratio, molarity (M), and sodium silicate (SS)/sodium hydroxide (SH) ratio are fixed to 0.45, 12 M, and 2, respectively. The fresh property in terms of slump flow and other properties like compressive strength, water absorption, and dry density of the geopolymer mortar are determined. The result of this study shows that the inclusion of GGBS content in FA‐based geopolymer mortar significantly increases the compressive in both the curing conditions. Maximum compressive strength of 44.33 MPa is obtained when 50% GGBS is added to the mixes at a curing temperature of 60 °C.

Performance of eco-friendly fly ash-based geopolymer mortars with stone-cutting waste

In this study, the physical and mechanical properties of the geopolymers formed by substituting red (RSW) and yellow (YSW) stone-cutting wastes into geopolymer mortars based on class F fly ash at 10–40 wt% rates were investigated. Sodium hydroxide (NaOH) solution was used as an activator in the production of the mortars. Produced samples were thermally cured at 90 °C for 24 h. Workability, unit weight, flexural strength, compressive strength, water absorption, porosity, and elevated temperature resistance tests (400, 600, and 800 °C) were applied to the produced geopolymer mortars. In addition, the chemical analysis (XRF), crystal phase analysis (XRD) of wastes/selected mortars, and microstructural analysis (SEM) of before and after elevated temparature resistance tests were carried out to investigate the effect of stone-cutting wastes on geopolymer mortars. SW up to 40% enhances mechanical strength up to 26–30.7 MPa from 16.4 MPa due to its high Si/Al ratios and Ca content and needle-like crystals formed by stone-cutting waste. The crystalline phases are determined to be mullite, quartz, anorthite, and zeolite derived from stone-cutting waste in the selected mortars. As a result, it was seen that the use of stone-cutting wastes up to 40% improved the physical, mechanical, and microstructural properties of fly ash-based geopolymer mortars.