Effect of Silica Fume on Cement Mortar Cubes with Partial Replacement of Sand by Natural Pozzolan

Abstract

This paper presents an experimental investigation of the effect of silica fume (SF) in addition to the possibility of using local natural pozzolan (LNP) as fine aggregate replacement in cement mortars on the mechanical properties of cement mortars. The availability of local natural pozzolan in volcanic areas in Al-Madinah Al-Munawarah, KSA stimulated studying the possibility of utilizing LNP as a partial substitution for sand to reduce the density of the concrete and to improve the properties of eco-friendly concrete. The experimental work was carried out on seventy-five cement mortar cubes of 50 mm, nine cubes as control specimens, twelve cubes were made by replacing sand by volume with local natural pozzolan at replacement levels of 10, 20, 30 and 40% without addition of SF, fifteen cubes were made by replacing sand by volume with LNP at replacement levels of 10, 20, 30 and 40% and by replacing 5% of cement with silica fume, fifteen cubes were made by replacing sand by volume with LNP at levels of replacement of 10, 20, 30 and 40% and by replacing 10% of cement with silica fume. Twenty-four cubes were made without sand replacement and with cement replacement by weight with SF at replacement levels of 10, 20, 30 and 40%. The specimens were tested after 7, 14 and 28 days. The addition of SF showed a marked influence on the properties of the produced cement mortar cubes.