Effect of Woof Ash on the Properties of Concrete as Partial Replacement of Natural Sand

Abstract

Sources of good quality river sand are depleting very fast all around the world and excessive sand mining is giving rise to many environmental issues. The demand of sustainable growth of infrastructure in modern times is to find an alternative material for river sand that should not only satisfy the technical specification of fine aggregate, but it should also be abundantly available. Waste wood ash is a by-product of boiler industry, which has a potential to be used as a partial substitute for natural sand in concrete. The objective of the present study was to explore the possibility of utilization of wood ash as a partial replacement of natural sand in concrete. Experimental tests were performed to evaluate workability, hardened properties, durability properties and characteristics of concrete with partial replacement of natural sand with wood ash at replacement levels of 5, 10, 15 and 20%, and all properties were compared with conventional concrete containing 100% natural sand. The properties of concrete studied were workability, density, compressive strength, splitting tensile strength, water absorption, sorptivity, chloride-ion penetration and XRD & SEM analysis. Test results indicate that at constant w/c ratio, workability of concrete decreased with inclusion of wood ash as partial replacement of natural sand in concrete. There was an significant improvement in compressive strength and splitting tensile strength of concrete containing wood ash as compared to control concrete, with concrete containing 5% wood ash showing maximum compressive and splitting tensile strength at 7, 28 and 90 days. A increase in water absorption, sorptivity and chloride-ion permeability was observed in all concrete mixes containing wood ash as partial replacement of natural sand in concrete except at 5% replacement of natural sand as compared to control mix. XRD analysis at 28 and 90 days shows that wood ash is mainly a pozzollanic material, which contribute in hydration process of cement. SEM analysis shows the progressive decrease in voids in wood ash concrete mixes as the replacement of natural sand with wood ash was increased which may be due to the filler effect of micro-fines.