USE OF LOCAL BREWERY WASTE AND BITTER CASSAVA FLOUR AS A PARTIAL REPLACEMENT OF CEMENT FOR PLASTERING ECO HOUSES

Abstract

Cement is a major construction material throughout the world. However, given the escalating costs of building materials and the environmental hazards associated with the use of cement there is need to use alternative, cost-effective, non-conventional, locally available materials, especially those that can partially or wholly replace cement. This study tested the possibility of local brewery waste and bitter cassava flour as a partial replacement for cement for plastering traditional eco-houses (earth-based) in Northern Uganda. The following were examined through standard laboratory procedures; physical and chemical properties, compressive strength, shrinkage test and durability or bonding test. The specimens were made with cement partially replaced by local brewery waste or bitter cassava of varying percentages ranging from 10-50% and tested at 7, 14 and 28 days. The results obtained show that bitter cassava flour and local brewery waste reduces the cracking in plaster mortar. It is also determined that bitter cassava increases the shrinkage and the mixes containing only 40% and 50% bitter cassava cracked for mix ratios of 1:3 and 1:4, while local brewery waste reduces the shrinkage of the mortar and no crack was observed. The results also show that the compressive strength of the plaster mortar reduces as more cement is replaced with bitter cassava flour and local brewery waste. However, it is to be noted that the target minimum strength required is 2.5 MPa for mortar plaster for plastering earth-based walls. The results further reveal that for a mix ratio of 1:3 compressive strengths of 28.3 MPa is obtained for 0% bitter cassava flour, 21.9 MPa for 10% bitter cassava flour and 18.1 MPa for 20% bitter cassava flour. For a mix ratio 1:4 compressive strengths of 20.4 MPa is obtained for 0% bitter cassava flour, 17.5 MPa bitter xv cassava flour for 10% bitter cassava flour and 13.8 MPa for 20% bitter cassava flour. For a mix ratio 1:6 compressive strengths 11.5 MPa for 0% bitter cassava flour is obtained, 8.5 MPa for 10% bitter cassava flour and 6.9 MPa for 20% bitter cassava flour. These strengths are above the minimum required compressive strength of earth stabilized block of 2.5 MPa according to Kenya Standards, 2.8 MPa according to BS and 2.0 MPa according to ASTM hence indicating the potential of using bitter cassava flour and local brewery waste in plaster mortar for traditional eco-houses.