Use of unprocessed wood ash as partial replacement of sand in concrete

Abstract

The use of unprocessed low-calcium wood ash as partial substitution of natural sand in manufacturing of concrete has been explored in the present study. X-ray diffraction (XRD) spectrum indicates the presence of amorphous as well as crystalline silica in unprocessed wood ash. The total composition of silica, alumina, and ferric of 92.93% qualifies the unprocessed wood ash to be used as pozzolanic material. Experimental tests were performed in laboratory for workability, strength, and durability properties of concrete incorporating 0, 5, 10, 15, and 20% wood ash as substitution of natural sand. It was observed that at a fixed water-cement ratio (w/c), the slump of concrete decreased on inclusion of unprocessed wood ash as partial substitution of natural sand. The compressive strength and splitting tensile strength of concrete mixtures made with unprocessed wood ash were lower than control concrete. The wood ash concrete mixtures, except the concrete mixture containing 5% unprocessed wood ash, displayed higher water absorption, sorptivity, and chloride-ion penetrability compared to control concrete. XRD analysis of powdered concrete specimens indicated no qualitative change in phase formation on incorporation of unprocessed wood ash.