Effect of Sulphate and Acid on Self-Compacting Concrete Containing Corn Cob Ash

Abstract

Self-compacting concrete requires high powder content which implies increased cost and increased CO2 emission into the environment; hence, the need for the inculcation of a supplementary cementitious material (SCM) to the concrete mix such as corn cob ash (CCA) which is obtained by drying, grinding and burning the corn cobs. The chemical composition of the corn cob ash showed that it was pozzolanic as it conformed to the requirements stated in ASTM C618. Replacement of cement with CCA was carried out at levels of 0% (control), 5%, 10%, 15% and 20% and workability test was conducted at each replacement levels. The curing of the cubes was conducted for 7, 14 and 28 days in 3 mediums; water, hydrochloric acid (HCl) and magnesium sulphate (MgSo4). The cubes were weighed and crushed from which it was observed that 5% replacement showed better compressive strength, proving to be the optimum result. Results from 15% and above were unable to attain close enough values to the required strength but showed better resistance when submerged in the sulphate and acid solution. It was also observed that increasing CCA content, reduced the strength deterioration factor (SDF) of the concrete, indicating improved durability and the possible use of CCA for partial replacement of cement in SCC. However, replacement levels from 15% and above require longer curing period to attain better strengths as increase in CCA levels decreases the compressive strength of the concrete.