Investigation of the partial replacement of cement with cassava brewery waste ash in mortar for masonry

Abstract

Cement is a major construction material throughout the world. However, in the past years, the use of supplementary cementing materials has become an integral part in the construction industry due to escalating costs of building materials and the environmental hazards associated with the use of cement. There is also need to use alternative, cost-effective, non-conventional, locally available materials, especially those that can partially or wholly replace cement in both mortar and concrete mix designs. This study has tested the possibility of using Cassava Brewery Waste Ash (CBWA) as a partial replacement for Ordinary Portland Cement (OPC) in masonry works through standard laboratory procedures to determine the chemical properties of the ash, compressive strength and shrinkage tests on mortar cubes. The specimens were made with cement partially replaced by CBWA of varying percentages ranging from 10-80% and tested at 7, 14 and 28 days of curing. The research revealed that mortars produced with up to 50% replacement of cement with CBWA yielded a compressive strength of 5.13 N/mm2 for 1: 4 and 5.00 N/mm2 for 1:5 ratios after 28 days of curing, below 5.2 N/mm2 (Horng, 2010), which is the required minimum strength of clay bricks. The results also show an increase in compressive strength of mortar with age but a decrease in compressive strength of mortar with increasing content of CBWA. The results from shrinkage show a gradual reduction in shrinkage of mortar cubes with age and with percentage replacement of CBWA and these findings relates to results of (Markus, 2011). Chemical composition of the ash shows that the cementitious compounds (SiO2-53.85%, Al2O3- 11.85%, Fe2O3 -5.58%) sum up 71.28% above the minimum as specified in ASTM C618 -98 for replacement of cement hence CBWA has a potential for use in construction works. The unit cost of mortar produced on Partial replacement is higher than that for conventional mortar due to high transport and incineration costs