Eco-friendly utilization of rice husk ash and bagasse ash blend as partial sand replacement in self-compacting concrete

Abstract

Self-compacting concrete (SCC) is largely used construction material worldwide, uplifting the demand for river sand along with all of its constituents due to the recent construction boom. Rice husk ash (RHA) and Bagasse ash (BA) are the biomass waste of the abundantly produced crops in Pakistan, which causes several cardiovascular diseases to humans and poses threats to degrade air quality as well.Characterization of both RHA and BA was performed at the macro and microstructural level to study their suitability as fine aggregate in SCC. This research aims to study the effect of environment-friendly substitution of river sand with blended waste ashes of RHA and BA on microstructural, fresh, physicomechanical and sulfate resistant properties of SCC.The results of microstructural characterization revealed the pozzolanic nature of ashes is evident in Chapelle activity test and the adsorptive natured siliceous micro-sized ash particles contribute toward higher water demand in SCC. The scanning electron microscopy (SEM) analysis of SCC mixes containing blended ashes of RHA and BA revealed that the formation of secondary calcium silicate hydrate (CSH) gel occurred at a calcium to silica (Ca/Si) ratio of 1.41 as evident in Energy Dispersive X-ray Spectroscopy (EDX) analysis. The results of rheological properties revealed that the fluidity of SCC mixes reduced due to the porous nature of incorporated ashes, whereas the viscosity of the mixes improved upon the incorporation of blended ashes. The physicomechanical properties include water absorption, hardened density, compressive strength, and split tensile strength. The physicomechanical properties depicted that the 20% collective incorporation of waste ashes produced structural lightweight concrete confirming ACI 213R with the compressive strength and hardened density values of 20 MPa and 1816 Kg/m3, respectively. Conclusively, the eco-friendly utilization of blended ashes of RHA and BA improved the microstructure, viscosity, physicomechanical properties, and sulfate resistance of SCC.