Abstract:
In an attempt to minimize the energy consumption and carbon footprint associated with the production of cement, several potential alternative binders have been proposed to partially replace cement in concrete. Cement production releases huge amount of carbon dioxide into the atmosphere which has negative influence on our environment. Recently, in the construction environment, issues relating to sustainability of natural materials have become a necessity than choice. In this research, the effectiveness of rice husk ash (RHA) and sugarcane bagasse ash (SBA) were investigated to partially replace cement in a concrete mixture. The percentage replacements employed in this study are 0, 5, 10, 15, 20, 25, and 30% by weight of ordinary Portland cement (OPC) with water/binder ratio of 0.45 and targeted strength of 20 N/mm2. Concrete cubes were produced in triplicates and prior to the casting of samples, workability of the concretes were assessed. The curing of concretes by immersion in water was done for 7, 28, and 90 days. Oxide composition of OPC, RHA, and SBA was determined using X – Ray Efflorescence (XRF). The compressive strength test, Flexural strength test, Rapid chloride penetration test (RCPT), Sorptivity test, X - Ray diffraction (XRD) analysis, Scanning Electron Microscope (SEM) analysis and thermo gravimetric analysis (TDA) were conducted on OPC and optimum RHASBABC concrete. The results confirmed the pozzolanicity of RHA and SBA. Replacement of cement with 5% RHASBA in concrete was found to increase the compressive strength at 90 days (25.47 N/mm2) as compared with OPC concrete at 90 days (21.65 N/mm2), flexural strength at 90 days was 7.48 N/mm2 in OPC concrete while it was 7.745 N/mm2 in 5%RHASBABC concrete. These reflect the effect of pozzolanic content, which gradually improved the hydration process and enhance the compressive strength by 15%, flexural strength by 3.4% at 90 days. Permeability was lowered by 50% and sorptivity lowered by 11.34% in 5%RHASBABC concrete as compared with OPC concrete at 90 days. Addition of pozzolans promote depletion of Ca(OH)2 crystals, converting it into CaH204Si (C-S-H gel) leading to the strengthening of bond in the concrete
