STUDIES ON EFFECT OF GGBFS CONTENT ON THE PERFORMANCE OF GEOPOLYMER CONCRETE

Abstract

Geopolymer concrete (GPC) is an innovative, sustainable, cementless, and eco-friendly material that significantly reduces carbon emissions by entirely replacing cement in concrete production. Cement manufacturing is a major contributor to CO₂ emissions, and GPC offers a viable alternative. In this experimental investigation, the fresh, chemical, and mechanical properties of GPC were evaluated across various parameters to determine the optimum mix design. The study examined fly ash-to-GGBFS (alccofine) ratios ranging from 100/0 to 75/25, liquid-to-binder (L/B) ratios from 0.35 to 0.65, superplasticizer contents from 0.5% to 2.0%, sodium hydroxide molarity from 8M to 14M, and sodium silicate-to-sodium hydroxide ratios from 0.5 to 3. Durability tests included exposure to seawater, magnesium sulfate (sulfate attack), acid attack, and wetting-drying conditions. Workability was assessed using slump and density tests, while mechanical properties were evaluated through compressive strength, splitting tensile strength, flexural strength, elastic modulus, and rebound hammer tests. Durability tests measured residual compressive strength, visual inspections, and density variations. The results revealed that oven-cured samples consistently outperformed ambient- cured samples, with the 75/25 fly ash-to-alccofine ratio achieving the highest engineering strength. The compressive strength peaked at an L/B ratio of 0.55, with strength increasing up to this point before declining randomly at higher ratios. A mix containing 1.5% superplasticizer and a 0.45 L/B ratio demonstrated superior strength compared to other combinations. Increasing the NaOH molarity up to 12M enhanced compressive strength, but strength declined beyond this point under both curing conditions. Similarly, strength improved with higher alkaline ratios, peaking at a ratio of 2, before decreasing. Mechanical strength also increased with curing temperature, reaching an optimum at 100°C, after which it began to decrease. Durability tests showed that seawater exposure initially increased strength and density but led to degradation after 12 weeks. Alccofine-based GPC exhibited better resistance to seawater and sulfate attacks compared to other compositions. Both types of specimens followed similar patterns of strength and mass loss under these conditions, with alccofine-based samples demonstrating superior stability. Under wetting-drying cycles, alccofine-based GPC also exhibited greater durability and resistance to degradation. For the final optimum values, the Advanced machine learning techniques, including Artificial Neural Networks (ANN), Gene Expression Programming (GEP), Support Vector Regression (SVR), Bi-LSTM, and Self-Improved Jelly Search Optimization (SIJSO), demonstrated significant v potential in predicting the mechanical properties of GPC. These methods offer powerful tools for optimizing mix designs and enhancing performance. This study underscores the potential of Alccofine as a high-performance supplementary material and highlights the role of advanced ML techniques in advancing sustainable construction practices.