International Journal of Science, Engineering and TechnologyAuthors: Assistant Professor Md. Anzar Rabbani, Tambir Hussain
Abstract: This work investigates the complex interplay between blast furnace slag (BFS), metakaolin, and the compressive strength of concrete, with the objective of clarifying their synergistic effects as supplemental cementitious materials (SCMs). The study examines the pozzolanic characteristics of metakaolin, obtained from calcined kaolin clay, and the latent hydraulic reactivity of blast furnace slag, a byproduct of iron manufacturing. Controlled laboratory studies were conducted on concrete samples with varied amounts of SCM substitution (0–40%) to measure their compressive strength development at 7, 28, and 90 days. The inquiry examines microstructural development, water absorption rates, and calcium hydroxide consumption to evaluate hydration kinetics. This work elucidates how supplementary cementitious materials (SCMs) improve pore structure and augment binding capacity when compared to traditional Portland cement systems, establishing a clear correlation between their chemical composition, particle size distribution, and mechanical performance. The thesis also examines the fundamental processes influencing strength variations, highlighting the significance of BFS in long-term strength enhancement and metakaolin in early-age microstructural densification. Advanced characterisation methods, including as SEM-EDS and XRD, elucidate how these materials enhance the interfacial transition zone (ITZ) and diminish permeability. The research determines ideal replacement ratios (e.g., 20–30% BFS + 10% metakaolin) that optimise workability, durability, and compressive strength while reducing clinker use. Fluid absorption studies indicate a 30–50% decrease in capillary porosity for SCM-blended concretes, clearly associating their pore-blocking capacity with enhanced sulphate and chloride resistance. These results highlight the environmental and technological benefits of SCMs, endorsing their use under harsh exposure circumstances.
