Suitability of corncob ash as a partial cement replacement

Cement is the most utilised construction material, and the second most consumed global commodity after water. Its demand has soared proportionately with the exponential rise in population to match required development. The heavily energy-intensive processes involved in its production contribute to about 7 to 10 per cent (%) of the total global emissions, with potentially adverse environmental implications and are expensive economically. These processes, and those of concrete production consume heavily on natural resources such as sand, gravel, water, coal and crushed rock, the mining of which mars the environment. It is however possible, that energy and cost efficiency can be achieved by reducing on the amount of clinker, and in its place utilising partial cement replacement (PCR) materials that require less process heating and emit fewer levels of carbon dioxide (CO2). This study investigated the ability of corncob ash to be used as a PCR, by testing for either pozzolanic or cementitious properties. Experiments were carried our by replacing cement by weight in concrete mixes with corncob ash at 5%, 7.5%, 10%, 15% and 20% steps at the point of need. The results were compared with a control specimen made with no cement replacement. Durability was tested using the sulfate elongation test. The highest compressive strength was observed at the 7.5% replacement. However, higher replacement levels also showed impressive strengths suitable for structural applications. The sulfate elongation test results were inconclusive. These findings showed good reproducibility and highlight the potential of corncob ash as an effective pozzolan.