Geopolymer Mix Research Articles

Effect of Source Type on Pore Structure and Properties of Aerated Geopolymer Concrete

A study has been carried out to produce environmentally friendly lightweight concrete by substituting cement with alternative geopolymer binders. Fly ash and silica fume (waste materials) were used as source materials and their effect on pore structure and properties of aerated geopolymer concrete was evaluated. Autoclaved aerated concrete, locally known as thermostone, was supplied from the market and tested as a reference mix. Three aerated geopolymer concrete mixes (around 550 kg/m3 density) were produced by mixing source materials (fly ash and silica fume), activator solution (sodium silicate and sodium hydroxide), and aeration agent (aluminum powder). It was found that by not only enhancing the pore structure but also improving the binder medium, the aerated geopolymer mixes were stronger and less absorbed than the autoclaved aerated concrete mix. However, the thermal insulation of the aerated concrete mix was better than those of aerated geopolymer concrete mixes. In terms of the source material, it was found that usage of fly ash helped in enhancing the strength by about 100% of autoclaved aerated concrete. In addition, unless its lowest density, aerated geopolymer mix made with fly ash and silica fume in combination absorbed less water than the other investigated mixes. Adding superplasticizer to the geopolymer mix helped in enhancing its pore structure by making the pores smaller, their irregularity lesser, and their number higher. In general, an environmentally friendly lightweight material with strength and absorption better than those of autoclaved aerated concrete was produced by adopting a geopolymerization process.

Expansion and Strength Evolution Mechanism of Granite-Based Geopolymer Based on the Reactivity of Calcium Expansive Agents

Abstract In this article, the role of the reactivity of different heat-treated calcium oxides on the properties of a granite-based geopolymer was investigated for low-temperature application to attain high linear expansion and its strength as well as understanding the probable underlying mechanism. The reactivity of the calcium oxide was investigated using the combination of isocalorimetry and BET. The heat-treated calcium oxides were classified as low reactive, medium reactive, and highly reactive with respect to their heat release in water. In addition to this, the resultant effect of the heat-treated calcium oxide was explored in terms of the exothermic behavior, linear expansions, compressive strength, and the pore volume distribution at a dosage of 0.1 wt% of the solid phase of the geopolymer mix. The results indicate that the different reactivities of the calcium oxide impact the linear expansion as well as the compressive strength. The different reactive calcium oxides improved the linear expansion by at least 100%. However, the low reactive calcium tends to decrease the compressive strength by 35% as a result of overexpansion. Therefore, this calls for the optimization of the reactivity of CaO for its application geopolymer for the best properties.

Impact of calcium content and pH value on MICP crack healing of geopolymer concrete

In recent years, microbial-induced carbonate precipitation (MICP) is becoming a popular method of soil stabilisation and concrete crack healing. In MICP, calcium is a necessary reactant, and pH value is a crucial factor for living bacteria. Both parameters (i.e., calcium and pH) are adjustable for geopolymer concrete mix design. Given the attractive potential for future applications of geopolymer concrete, understanding the impact of calcium content and pH value of MICP crack healing in geopolymer concrete mix design is of great importance. In this study, it was found that high calcium content in geopolymer concrete mix design is helpful to improve the healing effect. When CaO% in mix design increases from 7.5 % to 18.3 %, the healing degree increases. When Na2O% increases from 4.4 % to 11.6 %, the pH value of geopolymer concrete is improved by around 1, and it was also found that the impact of pH value depends on the way healing is implemented. In the case where bacteria were applied from outside of the healing surface cracks, the effect of pH value was almost negligible. However, when bacteria were used for internal healing, the lower pH value of the geopolymer mix design was beneficial for bacteria to provide a more suitable environment for bacterial activity and thus generate healing products. Therefore, the adjustment of calcium content and pH value in the geopolymer mix design can enhance the effectiveness of MICP crack healing for geopolymer concrete.

Suitability Study on Strength Properties of Crumb Rubber in Geopolymer Concrete

Due to an incessant upsurge in the construction industry and the steep increase in the cost of raw materials, researchers are focusing on various resources that can be replaced with cement as a construction material. One such material that is rich in Silicon and Aluminium is Flyash. Flyash as an additive to concrete made a way for a contemporary material that was coined as Geopolymer Concrete (GPC). In Geopolymer, alkaline activators such as sodium hydroxide or potassium hydroxide are mixed with sodium silicate so as to form geo-polymerization with products like GGBS, flyash etc. and which as a result binds the aggregate. This paper mainly emphasizes on role of Crumb Rubber (CR) in the formation of GPC replacing the fine aggregates by various percentages (5% - 15%) of CR. The Geopolymer mix design is proposed for M40 grade. Compressive and tensile strength tests were carried out on concrete modified with Flyash and GGBS (Ground Granulated Blast Furnace Slag) in 60:40 ratios. At a molarity of 14M, ratio of sodium silicate to sodium hydroxide is maintained as 2.5. The samples were placed in an ambient condition and were tested for strength on 7, 14 and 28 days. Based on the experimental results, it was observed that use of CR in GPC does not enhance the strength properties and cannot be used in high-end structural applications only.

Taguchi-optimized triple-aluminosilicate geopolymer bricks with recycled sand: A sustainable construction solution

Rapid infrastructure development has led to an enormous demand for cement and a huge production of construction and demolition (C&D) waste. The ever-growing demand for cement is leading to a very high amount of CO2 emissions in the atmosphere. This research article focuses on addressing these two major issues of CO2 emission and inadequate handling of C&D waste by developing novel geopolymer bricks by utilizing the three-aluminosilicate waste materials, which includes rice husk ash (RHA), ground granulated blast furnace slag (GGBS), and red mud, and using recycled washed sand as filler. Taguchi’s method was used to develop the geopolymer mix design by making use of four factors, i.e., binder percentage with six levels and three levels for alkaline solutions, sodium silicate/sodium hydroxide (SS/SH), and alkaline to binder ratio(A/B). A novel approach is adopted for preparing the alkaline solution using three different techniques which are highlighted in this research study. The compressive strength and water absorption were tested, and the optimum percentage of mix was found with B5 binder, which includes 60 % RHA, 20 % GGBS, and 20 % red mud with an alkaline solution of A2, SS/SH as 2, and alkaline/binder as 0.45. The maximum compressive strength found to be 27.34 MPa, and the minimum water absorption was also recorded at this combination, which was 5.68 %. The compressive strength and water absorption were negatively correlated with a degree of 96 % found by using the parametric map. Desirability analysis and statistical analysis using ANNOVA techniques were used to discover the optimum percentage. Microscopic analysis was performed on the highest and lowest values of the L18 design of the experiment by Taguchi’s method. Along with this, a clustering algorithm was used to evaluate the scanning electron microscope (SEM) images. The overall research study suggested that the percentage of binder and alkaline solution were the governing factors for the properties of geopolymer bricks.

Performance assessment and economic and ecological analysis of carbon-negative recycled crumb rubber-based geopolymers

Geopolymer technology offers several compelling ecological and economic advantages regarding waste management. This research investigates the effect of size (less than equal to 4 mm) and amount (5–15 vol%) of crumb rubber (CR) as fine aggregate on the physical, mechanical, and durability properties of geopolymers. The economic and ecological analyses were also performed to determine the effect of producing CR-based geopolymers on cost and the environment. The results revealed that the addition of CR negatively influences the physical, mechanical, and durability properties; nonetheless, incorporation of 5–10 vol% CR with a size less than 2 mm exhibited satisfactory performance fit for medium-strength structures such as foundations, partition walls, sidewalks, drainage structures, etc. Additionally, although the incorporation of CR slightly increases the production cost (3.99–11.97%) and embodied energy (0.08–0.24%) of resulting geopolymers, the embodied CO2 emission of 5, 10, and 15 vol% CR-incorporated geopolymer mixes is 90.4, −143.6 and −377.6 kgCO2e/m3, respectively. In contrast, the embodied CO2 emissions of conventional geopolymer mix is 324.4 kgCO2e/m3, which shows the negative carbon emission potential of CR-modified geopolymers, providing a glimmer of hope for sustainable development in the construction industry.

Engineering and microstructural properties of carbon-fiber-reinforced fly-ash-based geopolymer composites

Alkali-activated fly ash and slag-based geopolymer composites offer sustainable cement alternatives to conventional cement materials. Incorporating fibers mitigates issues such as brittleness, insufficient toughness, and cracking in geopolymers. However, limited systematic research exists on the influence of carbon fiber characteristics on geopolymer performance. In this study, the effects of carbon fibers having varying lengths (6 mm and 12 mm) and volume fractions (0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) on multiple properties of geopolymers, including workability, water absorption, porosity, mechanical strength, drying shrinkage, uniaxial tensile properties, fracture toughness, and microstructure, are investigated. Results indicate that the incorporation of carbon fibers diminishes the flowability of the geopolymer mix and accelerates its setting time. Parameters such as water absorption, porosity, and compressive and flexural strengths initially decrease and then increase with increasing fiber content. Carbon fibers positively affect drying shrinkage, particularly during the early stages. The fiber bridging effect enhances uniaxial tensile properties, reducing brittleness. Carbon fiber addition improves the fracture toughness of the composite, achieving an optimal volume fraction at 0.6%. At this volume fraction, carbon fibers of 6 mm length exhibit better crack initiation toughness and resistance to instability cracking than fibers of 12 mm length. Moreover, the presence of carbon fibers promotes the formation of hydration products, minimises the occurrence of microcracks, and interacts synergistically with the slurry matrix to enhance overall crack resistance and material toughness. This study provides a valuable reference for the development and application of fiber-reinforced geopolymer materials.

Effect of Micro Lime on The Ambient Cured Sugarcane Bagasse Ash-Based Geopolymer Concrete

Geopolymer concrete has been the ideal replacement for Ordinary Portland cement concrete in producing green concrete. The binder in geopolymer concrete is a cementitious paste made from amorphous Aluminosilicate and activated by an Alkaline solution. The geopolymerization process is initiated at elevated temperatures. Thus, the curing requires elevated temperatures. This curing method limits the application of geopolymer concrete in the construction industry. In a geopolymer mix, the presence of Calcium ions allows the formation of Calcium Aluminate Silicate and Calcium Silicate Hydrate gels, allowing ambient temperature curing. Therefore, this study investigates the effect of micro lime on the Sugarcane Bagasse Ash-based geopolymer concrete. The micro lime was added to the geopolymer concrete in 1, 3, 5 and 7% by the Sugarcane Bagasse Ash weight. A mix design was based on a Densified Mix Design Algorithm. The tests carried out included compressive strength and water absorption. Ambient curing of the SCBA-based geopolymer concrete was achieved with 1% of the micro lime. The compressive strength increased with the increase of the micro lime, 10N/mm2 at 1%, to 18.25N/mm2 at 7% micro lime. The ambient temperature-cured geopolymer concrete at 3% micro lime had the lowest water absorption rate.

Developing Geopolymer Concrete by Using Ferronickel Slag and Ground-Granulated Blast-Furnace Slag

Geopolymer concrete is gaining recognition as an environmentally friendly alternative to traditional cement-based materials, offering potential solutions for reducing the carbon emissions of the construction industry. This study aims to develop GGBFS–FNS geopolymers utilising ferronickel slag (FNS) and ground-granulated blast-furnace slag (GGBFS). Ground FNS (GFNS) is a potential candidate for replacing fly ash in geopolymers. This research aims to develop for the first time a GGBFS–FNS alkali-activated concrete. Numerous trials were conducted including different GGBFS–FNS blend percentages, several chemical admixtures and varying activator concentrations to develop the optimal binder mix composition. The effects of different chemical admixtures on the properties of geopolymer pastes, mortars, and concretes were investigated. The study evaluated setting time, compressive strength, shrinkage, and physical and durability properties. The results indicate that conventional admixtures have limited impact on the setting time, while increasing the water/solid ratio and decreasing the GGBFS content could extend the initial and final setting times. The presence of FNS aggregate could improve the compressive strength of geopolymer mortars. The water absorber admixture was highly effective in reducing shrinkage and increasing chloride diffusion resistance. The geopolymer mix containing 50 wt.% GFNS and 50 wt.% GGBFS with the presence of the water absorber admixture presented high chloride diffusion resistance, non-reactivity to the alkali–silica reaction and high sulphate resistance. Overall, the GGBFS–FNS geopolymers exhibited promising potential for engineering applications as an environmentally friendly material, particularly in aggressive environments.

Residual Properties of Geopolymer Concrete for Post-Fire Evaluation of Structures.

The research focuses on effectively utilizing industrial by-products, namely fly ash (FA) and ground granulated blast furnace slag (GGBS), to develop sustainable construction materials that can help reduce carbon emissions in the construction industry. Geopolymer mix design using these by-products is identified as a potential solution. The study investigates the impact of different water to binder ratios (W/B) ranging from 0.4 to 0.6 on the residual properties, including compressive strength (CS), of geopolymer concrete (GPC), in accordance with Indian Standard for Alkali activated concrete. Lower W/B ratios were found to result in a more compact and less porous microstructure in the GPC. Additionally, the research explores the post-fire performance of GPC with varying grades (M10, M20, M30, & M40) and different W/B ratios, following the ISO 834 standard fire curve. It was observed that concrete samples exposed to elevated temperatures displayed a more porous microstructure. The mass loss of GPC with 0.4 W/B was found to be 2.3-5.9% and for 0.6 W/B ratio, the loss was found to be 3-6.5%, after exposing to 30-, 60-, 90-, and 120-min of heating. In the case of strength loss, for 0.4 W/B ratio, the loss was 36.81-77.09%, and for 0.6 W/B ratio the loss was 38.3-100%, after exposing to 30-, 60-, 90-, and 120-min of heating. Overall, the findings suggest that optimizing the W/B ratio in geopolymer concrete can enhance its compressive strength, as well as residual properties, and contribute to its suitability as a sustainable construction material. However, the response to elevated temperatures should also be considered to ensure its performance in fire scenarios.

Mechanical properties, flexural behaviour, and ductility characteristics of fibre-reinforced geopolymer mortar

This study aims to explore the potential of ambient-cured geopolymer as a substitute for ordinary Portland cement (OPC)-based mortar. However, due to their brittle nature, geopolymer materials require reinforcement to enhance ductility. To address this, an experimental program was conducted to investigate the effects of adding polypropylene (PP) and micro steel (MS) fibers to fiber-reinforced geopolymer mortar (FRGM) at volume fractions of 0%, 0.5%, 1%, and 1.5%. The ternary blended geopolymer mortar consisting of fly ash (FA), and ground granular blast furnace slag (GGBS), along with a novel pozzolan called eco-processed pozzolan (EPP) was investigated. The present study assessed the hardened properties of the FRGM, including compressive strength, splitting tensile strength, modulus of elasticity (MoE), ultrasonic pulse velocity (UPV), and the compressive strength of the material when exposed to elevated temperatures. The aim of this study was also to investigate the load–deflection response in terms of deflection, load, flexural strength, and toughening mechanisms; and also, the bonding between the fibers and the mortar matrix was examined using field emission scanning electron microscopy (FESEM). The results indicated that including 0.5% PP fibers and up to 1.5% MS fibers marginally improved compressive strength and MoE. The corresponding increments in splitting tensile strengths were 5% and 134%, respectively. The addition of fibers improved the fracture parameters of the FRGM. The inclusion of both MS and PP fibers significantly enhanced post-cracking flexural and toughness energy. At deflection L/150, MS fiber mixes exhibited 4–5 times higher toughness energy than PP fiber mixes, and also its evidently observed in the FESEM micrographs. The incorporation of 1.5% fiber volume to non-fibrous mix resulted in an improvement of 43.2 N.m. and 10.1 N.m. in toughness (T150) for MS and PP mixes, respectively. At an elevated temperature of 600 °C, the FRGM specimens gained a massive reduction in compressive strength, with the maximum result being at 87% for 1.5PP and 71% for 0.5MS. Overall, the MS fiber-reinforced geopolymer mixes exhibited superior performance as compared to PP fibers.

Physical, hydrolytic, and mechanical stability of alkali-activated fly ash-slag foam concrete

Foam concrete is prone to instability during mixing, casting, and curing. Besides preformed foam stability characteristics and volume, several geopolymer mix parameters, viz., precursor composition, silica modulus, alkali content, and water content, influence the overall foamed concrete stability, the understanding of which is still limited. This study evaluates the effect of the above parameters on the physical, hydrolytic, and mechanical stability of fly ash and slag-based foamed geopolymer. Physical stability was assessed by the design of experiments using a central composite design (inscribed), while systematic laboratory experiments assessed hydrolytic and mechanical stability characteristics. The foamed geopolymer behavior is sensitive to silica modulus and solid alkali-to-binder ratio, showing maximum interaction effects for producing stable foamed geopolymer for i) target to actual fresh density difference and ii) settlement along the height. The water-to-binder ratio was the most significant factor affecting the homogeneity across the cross-section along the height.Further, the alkali and slag content significantly affected the hydrolytic and mechanical stability characteristics. An optimum proportion of slag content, silica modulus, solid alkali-to-binder ratio, and water-to-binder ratio is suggested for the maximum benefit of fly ash and slag-based foamed geopolymer. This study provides a framework for comprehensive stability assessment of foamed geopolymers and can aid in developing sustainable lightweight materials for industrial applications.

Green Synthesis of the Effectively Environmentally Safe Metakaolin-Based Geopolymer for the Removal of Hazardous Industrial Wastes Using Two Different Methods.

Untreated wastewater pollution causes environmental degradation, health issues, and ecosystem disruption. Geopolymers offer sustainable, eco-friendly alternatives to traditional cement-based materials for wastewater solidification and removal. In this study, we investigate how wastewater containing organic and inorganic pollutants can be removed using geopolymer mixes based on metakaolin incorporation with cement kiln dust as an eco-friendly material. The present investigation compares the efficacy of two different techniques (solidification and adsorption) for reducing dye contaminants and heavy metals from wastewater using a geopolymer based on metakaolin incorporation with cement kiln dust. This study investigated the adsorption capacity of a geopolymer based on metakaolin incorporating two different ratios (20% and 40% by weight) of cement kiln dust (MC1 and MC2) for the reactive black 5 dyeing bath effluent (RBD) only and in a combination of 1200 mg/L of Pb2+ and Cd2+, each separately, in aqueous solutions under different adsorption parameters. The results of the adsorption technique for the two prepared geopolymer mixes, MC1 and MC2, show that MC1 has a higher adsorption activity than MC2 toward the reactive black 5 dyeing bath effluent both alone and in combination with Pb2+ and Cd2+ ions separately. The study also looked at using MC1 mix to stabilize and solidify both the dyeing bath effluent alone and its combination with 1200 mg/L of each heavy metal individually inside the geopolymer matrix for different time intervals up to 60 days of water curing at room temperature. The geopolymer matrix formed during the process was analyzed using FTIR, SEM, and XRD techniques to examine the phases of hydration products formed. The results showed that MC1 effectively adsorbs, stabilizes, and solidifies the dying bath effluent for up to 60 days, even with high heavy metal concentrations. On the other hand, geopolymer mixes showed an increase in mechanical properties when hydration time was increased to 60 days. According to our findings, the type of geopolymer developed from metakaolin and 20 wt.% cement kiln dust has the potential to be employed in the treatment of wastewater because it has good adsorption and solidification activity for the reactive black 5 dye effluent alone and for a mixture of dye pollutants with both Pb2+ and Cd2+ ions separately. Our results have significant implications for wastewater treatment and environmental remediation efforts, as they offer a sustainable solution for managing hazardous waste materials.

Influence of different waste-derived fillers in extruded geopolymeric matrix for 3D printing

One of the key challenges for the development of 3D printing in construction is the optimization of proper mix design in the fresh and hardened state. It is well known that the incorporation of nano- or micro-sized fillers generally improves thixotropic properties of the mixtures, having a great influence on the performance of extruded geopolymers by 3D printing.This work reports the preliminary results related to the optimization of geopolymer mix design for extrusion purpose. The effect of different fillers on fresh and hardened properties was assessed by manually extrusion of different geopolymeric mixes. Geopolymers and alkali activated materials are innovative binders with comparable and sometimes superior properties compared to traditional cementitious materials. The setting time of these materials is generally quite fast and usually occurs at room or at low (less than100 °C) temperature. In addition, they exhibit satisfying mechanical properties, hydraulicity and mesoporous microstructure.In this study, micro-sized fillers, sourced from different industrial wastes, such as fly ash and ceramic waste from porcelain tile grinding and lapping processes, were tested. For comparisons’ purpose, calcium carbonate was also tested as reference filler. The microstructure of the investigated materials as fillers was analyzed by particle size distribution, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Then, geopolymers were prepared by mixing metakaolin and the selected fillers with sodium hydroxide and sodium silicate solutions, considering the following molar ratios: SiO2/Al2O3 = 2.24, Na2O/Al2O3 = 0.64, Na2O/SiO2 = 0.28. All the samples were cured at room temperature in sealed conditions. The optimized filler concentration was selected by investigating the workability of the fresh mixes using a mini-cone slump tester. Preliminary attempts of extrusion process were manually carried out using a 5 mm-conical nozzle in air at room temperature. Moreover, the setting time was evaluated by Vicat test, while physical properties of hardened samples were analyzed by hydrostatic weighing. The preliminary results exhibited that the particle size and shape of the fillers strongly influence the fresh properties of the mix and thus the suitability of the selected mixes for extrusion in the final 3D printing application.

Composite material design for bricks manufacturing

Goa generates huge quantities of iron ore tailings (IOT) that require proper and effective monitoring, handling, and disposal. IOT consumes a lot of land, resulting in acid mine drainage. The smaller portion of IOT is returned to mine areas as backfill, while the majority is stockpiled or sent to the tailing dam. The ongoing research intends to develop a geopolymer mix for brick manufacturing using IOT. After going through various works of literature on brick manufacturing using IOT, seven different compositions were synthesized, wherein the percentage of IOT was kept at 50% while cement and lime were each at 5% for all trials. The fly ash content was in 5% increment, and GGBS was in 5% decrements. The physical and chemical characteristics of GGBS, fly Ash, and IOT were analyzed. The IOT contains Fe2O3 of 63.09%. Fly Ash belongs to class F. The major chemicals in GGBS include Calcium Oxide, Silicon dioxide, and Aluminium Oxide. The findings indicate that the compressive strength decreased with a rise in Fly Ash and a drop in GGBS content. The mix of 10% Fly Ash and 30% GGBS with 50% IOT achieved the highest compressive strength.

Synthesis of sustainable one-part geopolymers for well cementing applications

This work describes the synthesis of a novel one-part granite-based geopolymer mix design for well cementing applications by screening and improving the early-age performance of the geopolymers. The dissolution rate of granite and potassium silicate (K2SiO3) is slightly enhanced when they are blended, compared to the situation when granite was mixed with alkali solution. It was revealed that the chemical composition of granite requires modification. Ground granulated blast-furnace slag (GGBFS) was incorporated up to 90% of total weight (wt.%) within the solid precursor to find out the optimum design, based on its effect on fluid-state and solid-state properties. Pumpability and strength development of the slurries were studied to establish the applicability of the mix designs. To further characterize the final products, the mineralogy and morphology of the specimens were examined. The use of GGBFS, to modify the chemical composition of the granite, reduces the pumping time significantly. Moreover, the use of GGBFS increases the density and initial consistency value of the slurry proportionally to the increase in GGBFS content. Additionally, a threshold effect was observed in the mechanical strength development. The higher the GGBFS content (up to 50 wt%), the higher the early-age compressive strength. The highest measured compressive strength for the neat rock-based geopolymer recipe was around 6 MPa within 1-day to 7-day for a mix of 47 wt% GGBFS to the solid precursor, while its optimized mix was around 12 MPa within the same period.

Development of One-Part Rock-Based Geopolymers for Downhole Cementing Applications

AbstractThe use of geopolymers as a full replacement for cement in oil well cementing applications requires the development of not only environmentally friendly but also user-friendly cementitious materials. This study aims to investigate the early-age mechanical and chemical properties of synthesized one-part geopolymers, which are heat-cured rock-based products. These geopolymers were synthesized from granite-based precursors and were activated by solid powders of potassium silicate, with a small portion of potassium hydroxide (KOH) as an accelerator to enhance the setting time and early strength. The mechanical and chemical properties of the one-part geopolymers were characterized, and the mineralogy of the solidified samples was analyzed through crystallography to better understand their microstructure. The study found that the investigated one-part geopolymer mixes, which were activated by a solid activator with a modulus ratio of 2.4, developed acceptable compressive strength of around 7 to 13 MPa within 24 h and up to 7 days. The use of one-part geopolymers has the potential to provide environmentally- and user-friendly slurries that can facilitate their utilization for large-scale in-situ applications in the petroleum and civil engineering sectors.

Identifying Optimal Precursors for Geopolymer Composite Mix Design for Different Regional Settings: A Multi-Objective Optimization Study

Global objectives to mitigate climate change in the construction industry have led to increasing geopolymer development as an alternative to carbon-intensive cement. Geopolymers can have similar mechanical properties and a lower carbon footprint. However, geopolymer production is not as homogeneous as cement because it is produced by synthesizing alkali solutions with different aluminosilicate precursors. This study assessed the feasibility of using conventional (fly ash, blast furnace slag, and metakaolin) and alternative precursors (steel slag, mine tailings, glass waste, sewage sludge ashes, and municipal solid waste incineration bottom ashes (MSWI BA)) in geopolymer mixes for different European regions (Belgium and Finland) from a sustainability perspective, using environmental, economic, and resource availability indicators as the criteria. A multi-objective optimization technique was applied to identify optimal precursors for geopolymer mixes using two scenarios: (1) considering both conventional and alternative precursors; (2) only considering alternative precursors. The results from the first scenario show that one of the most optimal precursor combinations for the geopolymer mix is 50% fly ash, 25% MSWI BA, and 25% sewage sludge ash for Belgium. For Finland, it is 19% fly ash, 27% mine tailings, and 45% MSWI BA. For the second scenario, one of the most optimal precursor combinations for Belgium is 87% MSWI BA and 13% steel slag. For Finland, it is 25% mine tailings and 75% MSWI BA. Subsequently, linear regression analysis was applied to predict the compressive strength of the identified optimal mixes, and the results for Belgium and Finland were between 31–55 MPa and 31–50 MPa for the first scenario and between 50–59 MPa and 50–55 Mpa for the second scenario, respectively.

An alkali activated geopolymer concrete brick incorporated with devri stone quarry dust

Geopolymer is a concrete alternative which incorporates waste residues like fly ash. The properties that are required for application in construction are possessed by GPC that are fly ash based and it has been proved by recent studies. To meet growing demand for cement required to create infrastructural facilities, one tonne of carbon dioxide is produced during cement manufacture, which has a negative aftermath on nature. The aim of study is investigation of impact of devri stone quarry dust in geopolymer brick, also focus on characteristics strength of geo-polymer material. In this experimental approach, 25% ground granulated blast furnance slag and 75% fly ash were taken into consideration. This investigation focuses on the substitution of devri stone quarry dust for natural river sand in the production of geopolymer brick. Here 10% of quarry dust and 90% natural sand was used to produce materials with excellent compressive strength and hardness and a geopolymer mix was blended with 30% NaOH and 70% Na2Sio3, so as to achieve good compressive strength.

Effects of various additives on the crumb rubber integrated geopolymer concrete

The use of scrap tyres in construction materials has been promoted to curb the environmental exploitation caused by the open disposal of non-biodegradable waste rubber. Tyre grinds as aggregates in geopolymer concrete (GPC) would increase its sustainability value by reducing the consumption of natural aggregates. Although there is limited literature addressing the damage to GPC characteristics caused by rubber aggregates, this investigation was designed to determine the extent of possible side effects of using crumb rubber (CR) in GPC. Additionally, this investigation aims to address any resulting reduction in strength and durability using additives such as cement and fibres. Geopolymer specimens with CR replacement of fine aggregates by volume (0, 5, 10 and 15%) showed a compressive strength reduction of up to 17% when tested according to ASTM standards. Substituting the total binder by weight with Ordinary Portland cement (OPC) (0%, 5%, 10%, 15%, and 20%) improved the microstructural integrity of the rubberised geopolymer mix with the highest percentage of OPC. Despite producing new and additional binding products (CSH and CASH gels), the GPC surface readily disintegrated under acid exposure. Optimum glass fibres (GF) reinforcement (0.30%) effectively disrupted the GPC pore network, consequently reducing the acid permeability of the matrix. Further addition of steel fibres (SF) enhanced the GPC specimen's compressive and flexural strength. To analyse the cumulative effect of these additives on GPC microstructure, supporting tests such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were carried out. Although these additives enhanced the overall performance of rubberised geopolymer, it might somewhat reduce its green aspect.