Structural Strength Characteristics of Cement-Cassava Peel Ash Blended Concrete

Abstract

This study focuses on structural strength characteristics of cement-CPA blended concrete. Cement was replaced partially by CPA between 5 and 25% by weight of cement at 5% interval. Water binder ratios (w/b) of 0.5, 0.55, 0.6, 0.65 and 0.7 were used to produce the blended concrete of mix 1:2:4. The results of the investigation indicated that as the replacement of CPA increases, more water was required to make the blended concrete workable, hence, w/b of 0.7 was found to be optimum to produce workable blended concrete. The compressive strength of the blended concrete increases with age and reduces with increase in CPA content but at 5, 10 and 15% CPA the strength activity indices (SAIs) are 83, 82 and 79% at 28-day while at 120-day strength SAIs are 99, 95 and 87% showing that CPA contributes to later strength development than early strength development, a property that is peculiar to pozzolanic materials. Also, these values were greater than 75% specified by ASTM C311-98 showing that up to 15% is adequate. Similar trend was observed for flexural strength development as flexural crack was independent of the CPA content in the blended concrete. The results further show that CPA does not have appreciable influence on the density of the blended concrete. Regression analysis was conducted on the data and models showing relationship between compressive strength and curing ages for up to 15% CPA are proposed

Keywords: Cassava peel ash, cement, pozzolan, workability, compressive strength and flexural strength