Fly Ash Geopolymer Concrete Research Articles

Long-term durability of iron-rich geopolymer concrete in sulphate, acidic and peat environments

This study assesses the behaviour of iron-rich type F fly ash geopolymer concretes (GC) exposed to simulated sulphate, acidic, and peat environments, typical of those encountered in tropical peatlands. GC and Portland cement (PC) concrete of comparable strengths were exposed to a range of simulated solutions for 18 months, including 5 % magnesium sulphate (MgSO4), 5 % sodium sulphate (Na2SO4), 1 % and 3 % sulfuric acid (H2SO4) and peat. The GC generally outperformed PC in all conditions. The GC showed a significant increase in strength in the first year, along with enhanced durability properties. Microstructural analysis indicated a decrease in total porosity and pore size. This was attributed to continuing geopolymerization leading to the foration of additional N-A-S-H gel, which filled the pores and solidified the concrete matrix. However, compressive strength decreased at 18 months due to crack propagation caused by drying shrinkage. In Na2SO4, GC attained an 8.9 % and 6.3 % increase in compressive strength at 12 and 18 months, respectively, again attributed to ongoing geopolymerization. GC exposed to MgSO4 exhibited a significant decrease in compressive strength of approximately 11 % at 12 months and 19.8 % at 18 months, attributed to the formation of lower-strength M-A-S-H from reaction between MgSO4 and N-A-S-H gel. After 12 months GC exposed to 1 % and 3 % H2SO4 demonstrated a decrease in compressive strength of approximately 1.2 % and 4.5 %, respectively, together with 2 % and 3 % mass loss. Chemical and microstructural data confirmed this strength reduction due to the vulnerability of N-A-S-H to when exposed to H2SO4. GC exposed to peat solution exhibited a 1.25 % increase in compressive strength at 12-month, but a decrease of 11.3 % at 18-month. Microstructural analysis observed a reduction in Na+ within GC matrix, and the presence of gypsum. The reduction in pore sizes and total porosity suggested generation of zeolite crystalline material was contributing to the pore filling.

EFEKTIVITAS PENAMBAHAN SERAT POLYPROPYLENE TERHADAP KUAT LENTUR BETON GEOPOLIMER dengan SUPERPLASTICIZER

Geopolymer concrete is concrete composed of a mixture of coarse and fine aggregate without Portland cement binder. Fly ash is used as a substitute, because it contains a lot of silica and alumina. Geopolymer concrete has good strength and durability, but concrete also has disadvantages, namely brittleness, workability and often cracking due to tensile loads. Superplasticizer (SP) is used at 2% of fly ash weight to improve workability. The SP used is Sika viscocrete 1003. The addition of polypropylene fiber is one way to overcome brittle properties and the appearance of fine cracks in concrete. In this paper using Sika fiberforce 48mm polypropylene fiber which has a tensile strength of 465N/mm2(MPa) at a dose of 0%, 0.5%, 1%, 1.5% and 2%. The alkaline activator used is a mixture of NaOH and Na2SiO3 solutions. The molarity of the NaOH solution used is 8M with a ratio of NaOH/Na2SiO3 2: 3. From the test results, it is known that the influence of polypropylene fiber is effective for increasing the bending strength of geopolymer concrete. The bending strength value of geopolymer concrete with the addition of polypropylene fibers increased by 60.19%. The polypropylene fiber content will be maximum at a percentage of 0.5% of the total volume of the mixture.Keywords: Fiber, Flexural Strength, Fly Ash Geopolymer Concrete, Polypropylene, Superplasticizer

Soft computing techniques for predicting the compressive strength properties of fly ash geopolymer concrete using regression-based machine learning approaches

Soft computing techniques for predicting the compressive strength properties of fly ash geopolymer concrete using regression-based machine learning approaches

Compressive Strength Prediction of Fly Ash Geopolymer Concrete Using Support Vector and Random Forest Regression

Compressive Strength Prediction of Fly Ash Geopolymer Concrete Using Support Vector and Random Forest Regression

Flexural performance and damage of reinforced fly ash and slag-based geopolymer concrete after coupling effect of freeze-thaw cycles and sustained loading

To better represent field conditions, the bending performance of reinforced geopolymer concrete (GPC) beams after the coupling effect of freeze-thaw cycling and sustained flexural load was investigated. Two types of GPC (G10 and G50) with different content of fly ash and slag were included and compared with ordinary Portland cement concrete (OPC). The mechanical strength of concrete and bond strength of rebars in concrete before and after freeze-thaw cycles were measured. It was found that the frost resistance of G10 was the weakest followed by OPC and G50. Three scenarios of bending tests on reinforced concrete beams were included: (1) control (without freeze-thaw damage); (2) individual freeze-thaw cycling; (3) coupling effect before bending. Rebound tests were conducted to evaluate frost damages at different areas of the beams as the base to analyze bending behaviors of the beams. The failure mode, load-displacement(strain) relationship, ultimate flexural strength, and bending stiffness of beams from bending tests are analyzed. All beams in scenario (1) were dominant in flexural failure. For scenario (2), G10 and G50 failed in debonding failure due to significant reduction in bond strength, while OPC failed in diagonal tension failure as OPC could sustain bond stiffness, thus preventing debonding failure. For scenario (3), damages in GPC were exacerbated, while damages in OPC were limited.

Bond Model for High Calcium Fly Ash Geopolymer Concrete

Concrete industries and researchers have devoted great efforts to promoting sustainability in the construction sector. This includes finding innovative alternatives to OPC concrete to ensure environmental sustainability and prevent the depletion of natural resources. The present research explained the steps to develop a bond stress-slip model for high calcium fly ash (HCFA) geopolymer concrete based on the experimental results in the literature. This model is based on the concrete compressive strength (fc), concrete cover (Cc), and bar diameter (db), which are considered the most influential parameters on the bond response between the reinforcement and surrounding concrete. The regressed model shows a quite accurate prediction of the bond behaviour of HCFA, particularly those with high strength. The slight difference was attributed to the difficulty in identifying the exact values of Slips (δr1 and δr2).

Potential of fly ash geopolymer concrete as repairing and retrofitting solutions for marine infrastructure: A review

Corrosion in maritime infrastructure, particularly in reinforced concrete, has emerged as a significant cause for concern due to the presence of chloride ions in seawater. To address this challenge, geopolymer concrete has been proposed as a viable solution for retrofitting and restoring marine structures. This review paper explores the potential application of fly ash geopolymer concrete in marine infrastructure restoration. Fly ash's properties make it ideal for marine infrastructure restoration. Its high levels of amorphous silica and alumina enable geopolymerization, forming a strong binder resistant to chloride corrosion. Its fine, spherical particles enhance concrete workability and density, improving mechanical strength and impermeability. This geopolymer binder offers excellent resistance to corrosion from chloride ions commonly found in seawater, making fly ash geopolymer concrete highly suitable for marine applications. Overall, fly ash's chemical composition and physical traits offer resilience and sustainability in restoring marine infrastructure, ensuring long-term durability against corrosion. This review paper explores the potential application of fly ash geopolymer concrete in marine infrastructure restoration. By examining the primary forms of damage and mechanisms underlying concrete degradation in marine settings, this study highlights the durability and sustainability of geopolymer concrete compared to traditional concrete. Additionally, it discusses current solutions for repairing and retrofitting concrete in marine environments, emphasizing the promising characteristics of geopolymer concrete for integration into such structures. Through this analysis, innovative and environmentally conscious approaches are introduced for addressing corrosion-related challenges in the maritime industry, offering a resilient solution for the construction of enduring marine structures. Finally, recommendations for further research on the application of fly ash geopolymer concrete in marine infrastructure restoration are presented.

Utilization of Plastic Waste in Fly Ash Geopolymer Concrete Containing Recycled Concrete Aggregate for Pavements

Utilization of Plastic Waste in Fly Ash Geopolymer Concrete Containing Recycled Concrete Aggregate for Pavements

Comparative fracture properties of ambient-cured geopolymer concrete containing four different fibers in mono and hybrid combinations using digital image correlation

This paper presents an investigation on the effects of four different fibers (polypropylene (PP), polyvinyl alcohol (PVA), recycled polypropylene (RPP), and steel (S) fibers) on the fracture behaviour of ambient-cured fly ash geopolymer concrete (GPC). The four fibers were added into GPC by both mono at 1.0% volume and hybrid combinations with steel fiber at 0.5% of each other type of fiber. The full-field strain distribution and the crack mouth opening displacement (CMOD) were monitored by digital image correlation (DIC) technology. The results reveal that adding fibers was effective in enhancing the fracture performance and hindering the cracking behaviour of GPC. Furthermore, 1.0% volume steel fiber exhibited to be most advantageous in enhancing the flexural strength by 100%, flexural toughness by 4000%, fracture energy by 3897%, and critical stress intensity factor by 98.8%. GPC with 1.0% volume PP fiber exhibited a characteristic length of 7909 mm, improving the characteristic length of GPC by about 2925%. Additionally, the CMOD was found to have a strong linear relationship with deflection which is unaffected by other factors. The presence of fibers significantly enhanced the ultimate strain. The steel fibers exhibited better performance in hindering the crack propagation. The fracture process zone (FPZ) characteristics differed between specimens with non-metallic and steel fibers, with the latter exhibiting more tortuous shapes and multiple cracks. Notably, a hybridization of steel and non-metallic fibers proves better than mono non-metallic fibers in improving strength, toughness, and ductility. This research provides valuable insights for concrete design and the selection of appropriate fibers based on specific requirements.

Properties of Fly Ash Geopolymer Concrete as Marine Artificial Reef Building Materials

Properties of Fly Ash Geopolymer Concrete as Marine Artificial Reef Building Materials

Compressive strength prediction and low-carbon optimization of fly ash geopolymer concrete based on big data and ensemble learning.

Portland cement concrete (PCC) is a major contributor to human-made CO2 emissions. To address this environmental impact, fly ash geopolymer concrete (FAGC) has emerged as a promising low-carbon alternative. This study establishes a robust compressive strength prediction model for FAGC and develops an optimal mixture design method to achieve target compressive strength with minimal CO2 emissions. To develop robust prediction models, comprehensive factors, including fly ash characteristics, mixture proportions, curing parameters, and specimen types, are considered, a large dataset comprising 1136 observations is created, and polynomial regression, genetic programming, and ensemble learning are employed. The ensemble learning model shows superior accuracy and generalization ability with an RMSE value of 1.81 MPa and an R2 value of 0.93 in the experimental validation set. Then, the study integrates the developed strength model with a life cycle assessment-based CO2 emissions model, formulating an optimal FAGC mixture design program. A case study validates the effectiveness of this program, demonstrating a 16.7% reduction in CO2 emissions for FAGC with a compressive strength of 50 MPa compared to traditional trial-and-error design. Moreover, compared to PCC, the developed FAGC achieves a substantial 60.3% reduction in CO2 emissions. This work provides engineers with tools for compressive strength prediction and low carbon optimization of FAGC, enabling rapid and highly accurate design of concrete with lower CO2 emissions and greater sustainability.

Intelligent optimization for modeling carbon dioxide footprint in fly ash geopolymer concrete: A novel approach for minimizing CO2 emissions

In the global effort to mitigate climate change and reduce CO2 emissions, this study introduces an innovative, pioneering approach that combines artificial intelligence and experimental methods to investigate the CO2 footprint (CO2-FP) in fly ash geopolymer concrete materials. Three powerful non-linear intelligent learners, including Gaussian Process Regression (GPR) with Response Surface Methodology (RSM), Support Vector Regression (SVR), and Standalone Decision Tree Regression (DTR) are employed. The models are developed using seven input features related to the curing temperature, fly ash content, concentrations of coarse and fine aggregates, alkaline activators (Na2SiO3, NaOH) content, and superplasticizer. To identify the most influential input features, three different combinations (combo-1, combo-2, and combo-3) of these features are utilized in model building. The models' performance is assessed using key metrics such as coefficient of correlation (CC), Nash Sutcliffe coefficient efficiency (NSE), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). During the verification phase, the GPR-3 [Combo-3] model emerges as the most efficient in predicting the CO2-FP, with a high CC value of 0.9645 and NSE value of 0.9292. Consistently, Combo-3 demonstrates superior performance across all the models, underscoring the significance of the selected features. The findings of this study provide valuable guidance to industries and policymakers, enabling them to optimize concrete compositions and minimize CO2 emissions, thus contributing to global environmental sustainability.

Low-carbon enhancement of fly ash geopolymer concrete: Lateral deformation, microstructure evolution and environmental impact

To provide a more environmentally friendly alternative to conventional cement-based concrete, the use of fly ash based geopolymer concrete (FGC) has been explored. However, FGC typically requires high-temperature curing to achieve optimal material performance, which results in significant energy consumption and carbon emissions, leading to negative environmental impacts. To address this issue, a small amount of ordinary Portland cement (OPC) has been added to FGC, facilitating its setting and hardening at room temperature. At four different ages, a series of basic mechanical properties were tested, including Poisson's ratio. At 28 days, the resulting OPC-FGC has demonstrated comparable polymerization reactions and mechanical properties to heat-cured FGC, including lateral deformation ability and compressive behavior. Microscopic tests have shown that OPC-FGC has a denser matrix and a more reasonable pore structure distribution over time than heat-cured FGC. Furthermore, a life cycle assessment has indicated that OPC-FGC has a lower negative impact than heat-cured FGC. These findings suggest that OPC-FGC can be a viable substitute for conventional cement-based concrete, providing both mechanical properties and environmental benefits in engineering applications.

Strength and micro-structural performance of geopolymer concrete using highly burned rice husk ash

Globally, many researchers use rice husk ash as a supplementary material in cement and geopolymer concrete. pozzolanic admixture. However, silica is insufficient for effective pozzolanic reaction in cement concrete and geopolymerization in geopolymer concrete. Therefore, choosing silica in the amorphous form is the primary objective, particularly agro-based as a precursor. Therefore, this experimental study was to synthesize geopolymer from rice husk ash (RHA) collected from a brick kiln and fly ash to utilize both materials effectively. In this study, the material characterization of both precursors was studied, and it was observed that RHA has desirable qualities as a precursor along with fly ash. The effects of adding RHA (0–20 by weight in percentage) to fly ash geopolymer concrete were examined. The partial inclusion of RHA content increased the compressive strength of the fly ash geopolymers. The very persistent and amorphous silica phase in the geopolymer concrete was primarily responsible for the enhancement of the geopolymer matrix. Because it was dissolved in the alkaline-activated solution, the amorphous silica significantly aided in the geopolymerization process. Although fly ash particles were still present in the geopolymer matrix, the unreacted fly ash particles did not add strength. However, performance would be better if the RHA content were more than 15% in the geopolymer concrete. The results presented in the study highlight the significant benefits of highly burned rice husk ash: it enhances geopolymerization and strength. Therefore, such in-depth investigation is imperative to judge the applicability of an appropriate form of RHA to attain higher strength and micro-structural performance.

Long-term strength development and durability index quality of ambient-cured fly ash geopolymer concretes

While the geopolymer binder system is considered the foremost eco – friendly alternative to conventional Portland cement, its long – term performance has not yet been fully established. This study evaluated the long – term strength development and durability performance responses of fly ash (FA) – based geopolymer concrete mixtures activated using combined sodium silicate and sodium hydroxide solutions mixed at a varied ratio of the former to the latter, ranging from 0.72 to 4.89. The foregoing investigation was done focusing on effects of physico – chemical parameters comprising SiO2/FA, Na2O/FA and H2O/FA ratios. Concrete samples were cast then ambient – cured for one year, or oven – cured at 60 °C for 24 h followed by ambient – curing until testing. Various tests were done at 28 days or one year, including compressive strength, durability indexes, water absorption and volume of permeable pores. The durability indexes measured were water sorptivity, oxygen permeability and chloride conductivity. It was found that ambient – cured geopolymer concretes exhibited strong long – term strength gains of 60 to 90%, normal pore structure characteristics and good durability quality. However, the chloride conductivity test seemed to display erratic outputs, possibly due to ion fluxes, hence further research is needed to evaluate the method’s suitability for testing geopolymer concretes.

Determination of stress-strain relationship based on alkali activator ratios in geopolymer concretes and development of empirical formulations

Fly ash-based geopolymer has recently gained attention of researchers due to its potential application, as well as being an alternative binder with low emissions compared to ordinary Portland cement (OPC) in concrete production. Studies which are conducted on the design and mechanical properties of structural members produced from fly ash geopolymer concrete (GPC) are very important in terms of increasing the use of this concrete. The aim of this study is to obtain experimental data on the effect of sodium silicate/sodium hydroxide (SS/SH) and alkali activators/fly ash (AA/FA) ratios on the mechanical properties of a low calcium heat-cured fly ash geopolymer. In addition, it is to reveal the similarities and differences of OPC and GPC by comparing the mathematical formulations in existing regulations and concrete models with experimental data. Thus, geopolymer cylinder concrete samples were produced using 15 different mixtures with SS/SH ratios of 1.5, 2.5 and 3.5, while AA/FA ratios of 0.4, 0.5, 0.6, 0.7 and 0.8. At the end of the study, the optimum SS/SH ratio was obtained as 2.5. A decrease in the AA/FA ratio increases the compressive and splitting tensile strength, while an increment increases the ductility and consuming energy. In addition, the relationship between the experimental data and the splitting tensile strength and modulus of elasticity formulations depending on the compressive strength given in other studies and regulations as a part of literature was investigated, and then, two alternative empirical formulations considering the ratios of alkali activators were proposed at the end of the regression analysis. When the stress-strain relationship of OPC concrete models and GPC mixtures were compared, the closest unconfined concrete model for GPC concrete was the Hognestad model.

Compressive Strength Study based on Fly Ash Geopolymer Concrete at the age of 28 days under very High Temperature

Due to creeping process at the burning material, material’s elastic modulus and yield strength will decrease.Three fire protection system are exist in handling the fire problem: active fire protection, passive fire protection, and safety management. In correlation with material problem due to fire, passive fire protection is a strategy to counter it. This paper presents the results of fire protection by using Suralaya fly ash geopolymer concrete. Three molaritas of geopolymer concrete mixture design are 2M, 4M, and 6 M. Sodium Silicate (Na2SiO3) and Sodium Hydroxide (NaOH) are used as alkaline activator. The results of the experiment were analysed by compressive strength for the optimum values. This study found that the value of compressive strength of steam curing is higher than that of water curing, the value of geopolymer concrete compressive strength of 2M is higher than that of 4M, and the value of geopolymer concrete compressive strength of 6M is higher than that of 4M.

Effect of high temperatures on the properties of lightweight geopolymer concrete based fly ash and glass powder mixtures

Given the large manufacturing and consumption of concrete globally, there has been widespread speculation that it is a significant source of greenhouse gas emissions. Consequently, scientists are looking for sustainable and beneficial solutions to the environment. The influence of adding expanded clays (Leca) and crushed recycled bricks clay lightweight aggregates (RBA) on the fly ash and glass powder-based geopolymer concrete were investigated at ambient and high temperatures. High temperature influences the significant characteristics of mortar and lightweight aggregate geopolymer concrete. Low calcium fly ash was utilized as a binder in the concrete paste with a 10% replacement rate of Glass Powder. The concrete specimens were heated to 200, 400, 550, and 800 °C at a 7 °C/min rate for 60 min. Lower coarse aggregate strength is a contributing factor to concrete compressive strength reductions. The influences of high temperatures on geopolymer concrete were studied in terms of mass loss, cracking, water absorption, and microstructure. The research outcomes show that the geopolymer concrete suffered damage and dehydration at a heating temperature of 550 °C and above. Acceptable correlation between the temperature degree and Ultrasonic Pulse Velocity UPV with the compressive strength of the lightweight concrete. The test results showed the residual compressive strength 110.2%, 92.9%, 71.9%, and 55.6% as well as 109.2%, 91.5%, 79.6%, and 52.6% in addition to the density reduced 0.17%, 2.56%, 7.29%, and 12.18%, and 0.74%, 3.97%, 6.31%, and 13.25% in 200,400,550, and 800 °C for Leca and RBA type respectively. The equations showed acceptable results with experimental data. The impact of replacing waste glass powder with fly ash on the development of microstructures and gels was also investigated.

Flexural Behavior of Low Calcium Fly Ash Based Geopolymer Reinforced Concrete Beam

Pioneering studies have been conducted on alternative cementitious material in the manufacturing of conventional concrete to reduce carbon emission and improve the overall efficacy. However, there are limited studies on eco-friendly materials with low calcium fly ash. This study aims to examine the strength fly ash geopolymer concrete and reduce carbon emission. In this investigation, flexural test is done for conventional and geopolymer concrete (GPC) beam samples after the fulfillment of rest period and 24 h steam curing at 60 °C. The experimental results prove that the initial characteristics of both specimens are almost similar. When GPC specimens reached the service, yield, and failure stages, the load carrying capacity, deflection increased up to 21.5 and 8.75%, respectively and better load bearing capacity, moment resistance, and crack propagation were observed more than in conventional cement. Fresh property test results indicated the achievement of standard workability without the addition of any admixture. Our study show that low calcium based geopolymer can be used as an efficient material for the alternate of cement in cement-based industries with eco-friendly nature.

Enhancing class F fly ash geopolymer concrete performance using lime and steam curing

BackgroundProducing fly ash geopolymer concrete (FGPC) which can be cured by air, water, or steam instead of thermal curing without decreasing its mechanical properties will facilitate using FGPC in cast-in situ applications and precast concrete industry. Furthermore, it will decrease the consumed energy in FGPC production. This research attempts to achieve this goal by investigating the efficacy of supplementing class F FGPC with lime while using different curing processes to generate lime-fly ash geopolymer concrete (L-FGPC) that could be a feasible alternative to ordinary FGPC.MethodsThe studied variables included lime content, molarity of sodium hydroxide (NaOH), additional water content, curing type, and moisture of aggregates. The comparative criteria were setting times of fresh concrete, mechanical properties of hardened concrete, and voids ratio. SEM and X-ray diffraction tests were used to validate test results.ConclusionsSteam curing generated the best mechanical properties of L-FGPC. Using 2% lime content with steam-cured L-FGPC yielded proper setting times and the best mechanical properties. Microstructure tests revealed compact microstructure and decreased voids ratio upon using 2% lime content in L-FGPC. Increasing molarity of NaOH, decreasing additional water content, and decreasing moisture of aggregates enhanced L-FGPC’s mechanical properties.