Assessment of the strength properties of concrete using partial replacement of cement with cassava brewery waste Ash.

Abstract

This report details a study on use of Cassava brewery waste ash (CBWA) as a supplementary cementitious material in concrete. OPC was replaced with CBWA up to 25% at 5% interval. 12 concrete cubes and 12 beams were prepared for each of the 6 mix proportions for compressive and flexural strength testing respectively at curing periods of 7, 14, 28 and 90 days. Other laboratory tests such as Chemical composition of CBWA, Standard consistency and Setting times, and Slump were carried out. The sum of SiO2, Fe2O3 and Al2O3 of CBWA exceeded the minimum limit of 70% (i.e. SiO2 + Al2O3 + Fe2O3 = 72.27 > 70%) prescribed by ASTM C 618 for Pozzolans, and therefore the material was found to be chemically suitable as a pozzolanic material. The result of setting times indicates that as the percentage of CBWA increases, the initial and final setting times increased indicating the potential of CBWA ash as a set retarder. The workability of concrete decreased as the CBWA content increased. The results on compressive and flexural strength showed a decrease with increasing CBWA content and an increase with curing age. Up to 10% CBWA replacement yielded acceptable compressive and flexural strength results in accordance with the Ministry of Works and Transport (MoWT) General Specifications for roads and bridges and IS 456: 2000 respectively.