Evaluation of the mechanical properties of sea sand-based geopolymer concrete and the corrosion of embedded steel bar

Abstract. The manufacturing of cement for use in construction sites all over the world has resulted in tonnes of carbon dioxide being released. It is better to replace an alternative material such as geopolymer which contributes less carbon footprint than traditional Portland cement. Concrete is the most versatile building material, yet it has drawbacks in mechanical and physical properties, such as limited ductility, high water absorption, and low compressive strength. This study aims to determine the effect of the addition of composite fibers on the mechanical and physical properties of geopolymer concrete. In this research, the physical and mechanical properties of geopolymer concrete were investigated by mixing Class F fly ash with an alkaline activator consisting of sodium hydroxide and sodium silicate. Steel fiber and polypropylene cut into 2 mm fiber were added into the geopolymer concrete as reinforcement. Various volume percentages ranging from 0% to 2% are used. Density, water absorption, workability, and compression testing were performed on all geopolymer concrete reinforced with steel and polypropylene fiber with varying volume percentages. The density of geopolymer concrete is similar to that of Ordinary Portland Cement (OPC), which is around 2400 kg/m3, and it has gradually increased with the inclusion of steel fiber, while more polypropylene fiber causes lesser density. With an increment of steel fiber and a decrement of polypropylene fiber, the result of water absorption percentage shows a decrement. Besides, the inclusion of steel fibers reduces the workability of geopolymer concrete. However, the addition of polypropylene fibers shows a higher workability. Plus, the inclusion of steel fiber and the reduction of polypropylene fiber improve the compressive strength.

This research explores the application of Artificial Intelligence (AI) techniques to assess the mechanical properties of geopolymer concrete made from a blend of Banana Peel-Ash (BPA) and Sugarcane Bagasse Ash (SCBA), using a sodium silicate (Na2SiO3) to sodium hydroxide (NaOH) ratio ranging from 1.5 to 3. Utilizing three AI methodologies—Artificial Neural Networks (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS), and Gene Expression Programming (GEP)—the study aims to enhance prediction accuracy for the mechanical properties of geopolymer concrete based on 104 datasets. By optimizing mix designs through varying proportions of BPA and SCBA, alkaline activator molarity, and aggregate-to-binder ratios, the research identified combinations that significantly enhance mechanical properties, demonstrating notable international relevance as it contributes to global efforts in sustainable construction by effectively utilizing industrial by-products. The experimental results demonstrated that increasing the molarity of the alkaline activator from 4 to 10 M significantly enhanced both the compressive and flexural strengths of the geopolymer concrete. Specifically, a mixture containing 52.5% SCBA and 47.5% BPA at a 10 M molarity achieved a maximum compressive strength of 33.17 MPa after 20 h of curing. In contrast, a mixture composed of 95% SCBA and 5% BPA at a 4 M molarity exhibited a substantially lower compressive strength of only 21.27 MPa. Additionally, the highest recorded flexural strength of 9.95 MPa (77.25% SCBA and 22.5 BPA) was observed at the 10 M molarity, while the flexural strength at 4 M was lowest, at 4.12 MPa (95% SCBA and 5% BPA). Microstructural analysis through Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (ED-SEM) revealed insights into the pore structure and elemental composition of the concrete, while Thermogravimetric Analysis (TGA) provided data on the material’s thermal stability and decomposition characteristics. Performance analysis of the AI models showed that the ANN model had an average MSE of 1.338, RMSE of 1.157, MAE of 3.104, and R2 of 0.989, while the ANFIS model outperformed with an MSE of 0.345, RMSE of 0.587, MAE of 1.409, and R2 of 0.998. The GEP model demonstrated an MSE of 1.233, RMSE of 1.110, MAE of 1.828, and R2 of 0.992, confirming that ANFIS is the most accurate model for predicting the mechanical and rheological properties of geopolymer concrete. This study highlights the potential of integrating AI with experimental data to optimize the formulation and performance of geopolymer concrete, advancing sustainable construction practices by effectively utilizing industrial by-products.

In this study, the effects of steel fibers on the mechanical properties of the geopolymer concrete – compressive, splitting tensile, and flexural strength; compressive elastic modulus; and fracture properties – were evaluated. Milling steel fibers were incorporated into the geopolymer concrete, and the volume fraction of the steel fibers was varied from 0 to 2.5%. Fly ash and metakaolin were chosen as the geopolymer precursors. Fracture parameters – critical effective crack length, initial fracture toughness, and unstable fracture toughness – were measured by a three-point bending test. The results indicated that all the mechanical properties of the geopolymer concrete are remarkably improved by the steel fibers with the optimum dosage. When the steel fiber content was under 2%, the cubic and axial compressive strength and the compressive elastic modulus increased. The inclusion of 2% steel fibers enhanced the cubic and axial compressive strength and the compressive elastic modulus by 27.6, 23.7, and 47.7%, respectively. When the steel fiber content exceeded 2%, the cubic and axial compressive strength and the compressive elastic modulus decreased, having values still higher than those of the geopolymer concrete without steel fibers. The splitting tensile strength and flexural strength of the concrete were enhanced with increasing steel fiber content. When the steel fiber content was 2.5%, the increment of the splitting tensile strength was 39.8%, whereas that of the flexural strength was 134.6%. The addition of steel fibers effectively improved the fracture toughness of the geopolymer concrete. With 2.5% steel fibers, the initial fracture toughness had an increase of 27.8%, and the unstable fracture toughness increased by 12.74 times compared to that of the geopolymer concrete without the steel fibers.

In order to alleviate the environmental pollution and energy consumption problems caused by ordinary Portland cement, geopolymer came into being as a new type of green building material. The special three-dimensional mesh structure of geopolymer concrete makes it show excellent durability under fire, so it has been deeply studied by many scholars. This paper mainly expounds the research results of the basic static properties of inorganic geopolymer concrete at high temperature from the following four aspects: compressive strength, tensile strength, modulus of elasticity and stress-strain relationship. Due to the obvious differences in the mechanical and structural properties of geopolymer concrete in terms of raw materials, mix ratio, curing temperature, etc. There is no corresponding material and structural design specification for geopolymer concrete and it needs more incisive research before it applies to engineering construction.

Ordinary Portland cement (OPC) is the essential binding material to produce the OPC concrete. Production of OPC is recently attaining a rate of 2.6 billion ton per year worldwide and growing 5% annually. OPC contributes at rate of 5 – 8% of human-worldwide CO2 emissions which are the greenhouse gases pollute the atmosphere. Geopolymer concrete (GPC) is a creative, sustainable, economical and eco-friendly material for construction industry, which is a suitable alternative to the OPC concrete, able to extensively curb the CO2 emissions. To prepare this kind of concrete, a combination of pozzolanic material such as fly ash (FA), and/or ground granulated blast furnace slag (GGBS) rich with silica and alumina can react with alkaline activator solution producing aluminosilicate gel, acting as a superb binding material for fine and coarse aggregates under special conditions of curing. This study highlights the recent explorations on geopolymer mortars and concrete. Effect of chemicals such as sulphuric acid, effect of fly ash partial replacement with different binding materials, effect of concentration of alkaline activator solutions and the effect of temperature and time of curing variation have been discussed on durability and mechanical properties of geopolymer concrete. Results have shown superb resistance of geopolymer concrete to the detrimental effects of sulphuric acid on weight and compressive strength. Furthermore, fly ash partial replacement with silica fume, OPC or GGBS, or nanosilica inclusion in GPC has a positive effect on the GPC properties. Finally, using high concentration of sodium hydroxide has a detrimental effect on GPC properties.

This paper presents the results of an experimental study on the behavior of fly ash-, bottom ash-, and blended fly and bottom ash-based geopolymer concrete (GPC) cured at ambient temperature. Four bathes of GPC were manufactured to investigate the influence of the fly ash-to-bottom ash mass ratio on the microstructure, compressive strength and elastic modulus of GPC. All the results indicate that the mass ratio of fly ash-to-bottom ash significantly affects the microstructure and mechanical properties of GPCs

Comparative study on mechanical properties of fly ash & GGBFS based geopolymer concrete and OPC concrete using nano-alumina

This paper presents the change of material properties, such as decreasing of the compressive strength, splitting tensile strength, and porosity. The main objective of this paper is to analyze the mechanical properties of fly ash-based geopolymer concrete after being exposed to high temperature. The 28 th -day test specimens were burned for one hour at specified temperature variation of 200°C, 400°C, 600°C, and 800°C. Ordinary Portland Cement (OPC) concrete was used as a comparison. After burning at 400°C, the compressive strength of geopolymer concrete was surprisingly increased up to 27% of its normal strength. On the other hand, the compressive strength of OPC concrete decreased 67% from its normal strength. The splitting tensile strength of geopolymer concrete also decreased at the range of 50-70%. The porosity of concrete has a sufficient effect to compressive strength and splitting strength. X-Ray Diffraction (XRD) test of geopolymer concrete at temperature 400°C until 600°C showed some minerals change. Geopolymer concrete is proved to have better fire resistance compares to Portland Cement Concrete.

In the present study, the mechanical properties of geopolymer concrete (GPC) has been investigated. GPC represents a novel technology that is giving significant concern in industrial construction, especially in term of the current emphasis on sustainability. In this study, the NaOH and Na2SiO3 solutions were used as an alkaline solution in all GPC mixes. Na2SiO3 with 10 concentration of molarity, activator-to-FA ratio of 0.4, Na2SiO3/NaOH ratio of 1.75, and two curing regimes viz., ambient curing, and heat curing at 75 °C for 26 h were employed. The experimental results indicated that the geopolymer concrete strengths, modulus of elasticity, and other mechanical properties increased with heat curing as compared to ambient temperature curing. The elastic modulus of GPC was associated with the compressive strengths and similar to those of OPC concrete. Furthermore, the geopolymer concrete mixture requires proper mix proportion and temperature-controlled curing conditions to accomplish good results.

This paper presents results from experimental work on mechanical properties of geopolymer concrete, mortar and paste prepared using fly ash and blended slag. Compressive strength, splitting tensile strength and flexural strength tests were conducted on large sets of geopolymer and ordinary concrete, mortar and paste after exposure to elevated temperatures. From Thermogravimetric analyzer (TGA), X-ray diffraction (XRD), Scanning electron microscope (SEM) test results, the geopolymer exhibits excellent resistance to elevated temperature. Compressive strengths of C30, C40 and C50 geopolymer concrete, mortar and paste show incremental improvement then followed by a gradual reduction, and finally reach a relatively consistent value with an increase in exposure temperature. The higher slag content in the geopolymer reduces residual strength and the lower exposure temperature corresponding to peak residual strength. Resistance to elevated temperature of C40 geopolymer concrete, mortar and paste is better than that of ordinary concrete, mortar and paste at the same grade. XRD, TGA and SEM analysis suggests that the heat resistance of C–S–H produced using slag is lower than that of sulphoaluminate gel (quartz and mullite, etc.) produced using fly ash. This facilitates degradation of C30, C40 and C50 geopolymer after exposure to elevated temperatures.

In order to implement the concept of sustainability in the field of construction, it is necessary to find an alternative to the materials that cause pollution by manufacturing, the most important of which is cement. Because factory wastes provide siliceous and aluminous materials and contain calcium such as fly ash and slag that are used in the production of high-strength geopolymer concrete with specifications similar to ordinary concrete, it was necessary for developing this type of concrete that is helping to reduce CO2 (dioxide carbon) in the atmosphere. Therefore, the aim of this study was to study the influence of incorporating various percentages of slag as a replacement for fly ash and the effect of slag on mechanical properties. This paper showed the details of the experimental work that has been undertaken to search and make tests the strength of geopolymer mixtures made of fly ash and then replaced fly ash with slag in different percentages. The geopolymer mixes were prepared using a ground granulated blast-furnace slag (GGBFS) blend and low calcium fly ash class F activated by an alkaline solution. The mixture compositions of fly ash to slag were (0.75:0.25, 0.65:0.35, 0.55:0.45) by weight of cementitious materials respectively and compared with reference mix of conventional concrete with mix proportion 1:1.5:3 (cement: sand: coarse agg.), respectively. The copper fiber was used as recycled material from electricity devices wastes such as (machines, motors, wires, and electronic devices) to enhance the mechanical properties of geopolymer concrete. The heat curing system at 40 oC temperature was used. The results revealed that the mix proportion of 0.45 blast furnace slag and 0.55 fly ash produced the best strength results. It also showed that this mix ratio could provide a solution for the need for heat curing for fly ash-based geopolymer.

Effect of graphene nanoplatelets on engineering properties of fly ash-based geopolymer concrete containing crumb rubber and its optimization using response surface methodology

Industrial waste such as Ground Granulated Blast-Furnace Slag (GGBS) and Granite Waste Powder (GWP) is available in huge quantities in several states of India. These ingredients have no recognized application and are usually shed in landfills. This process and these materials are sources of severe environmental pollution. This industrial waste has been utilized as a binder for geopolymers, which is our primary focus. This paper presents the investigation of the optimum percentage of granite waste powder as a binder, specifically, the effect of molar and alkaline to binder (A/B) ratio on the mechanical properties of geopolymer concrete (GPC). Additionally, this study involves the use of admixture SP-340 for better performance of workability. Current work focuses on investigating the effect of a change in molarity that results in strength development in geopolymer concrete. The limits for the present work were: GGBS partially replaced by GWP up to 30%; molar ranging from 12 to 18 with the interval of 2 M; and A/B ratio of 0.30. For 16 M of GPC, a maximum slump was observed for GWP with 60 mm compared to other molar concentration. For 16 M of GPC, a maximum compressive strength (CS) was observed for GWP with 20%, of 33.95 MPa. For 16 M of GPC, a maximum STS was observed for GWP, with 20%, of 3.15 MPa. For 16 M of GPC, a maximum FS was observed for GWP, with 20%, of 4.79 MPa. Geopolymer concrete has better strength properties than conventional concrete. GPC is $13.70 costlier than conventional concrete per cubic meter.

Concrete plays an important role in the construction industry worldwide. New technology has made for easier development of new types of construction and alternative materials in the concrete area. Cement is the major component in the production of concrete, but its manufacture causes environmental issues and thus there is a need for alternative materials. Geopolymer concrete is a new type of material with that potential, commonly formed by alkali activation of industrial alumina silicate byproducts, such as fly ash and ground granulated blast furnace slag (GGBS). For this paper, mechanical properties of geopolymer concrete with fly ash and GGBS cured under ambient temperatures were studied. Five different grades of concrete were considered. The results were encouraging: The workability of the geopolymer concrete was similar to that of conventional concrete. Experimental results of flexural and splitting tensile strength revealed insignificant variation compared to conventional concrete. The mechanical properties of fly ash and GGBS-based geopolymer concrete were comparable with conventional concrete.

The demand for concrete is increasing day by day. As the consumption of cement is increased, environmental issues arise due to the release of CO2 during the manufacturing of cement. The objective of this research work is to produce a pollution free concrete with a combination of fly ash and GGBS (Ground granulated blast furnace slag) and without the use of cement. In this paper an attempt was made to study the mechanical properties of high strength geo-polymer concrete of grade M60 using GGBS, fly ash and micro silica. The testing program was planned for the mechanical properties of geo-polymer concrete and flexural behavior of corresponding beams. The experimental results indicated that the geo-polymer concrete M60 grade has a compressive strength of 70.45 MPa at the age of 28 days cured at ambient condition. Further, flexural strength and split tensile strengths for M60 grade high strength geo-polymer concrete at 28 days were observed to be 5.45 MPa and 3.63 MPa respectively. The modulus of elasticity was higher than the theoretical value proposed by IS 456-2000. It was also observed that the load carrying capacity of M60 grade high strength geo-polymer concrete found to be more than corresponding grade conventional concrete. The load-deflection, moment-curvature relationships were studied. The experimental results were encouraging to continue for further research in the area high strength geo-polymer concrete.