Abstract: Cement is the most utilized construction material, and the second most consumed commodity in the world after water. Its demand has soared proportionately with the exponential rise in population in a bid to match the required development. The heavily energy-intensive processes that are involved in its production contribute to about 7 to 10 per cent (%) of the total global emissions, with potentially adverse environmental implications, and are also economically expensive. These processes, and generally those of the production of concrete consume heavily on natural resources such as sand, gravel, water, coal and crushed rock, 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 supplementary cementitious materials (SCMs) that require less process heating and emit fewer levels of carbon dioxide (CO₂). This study investigated the ability of corncob ash (CCA) to be used as a SCM by testing for pozzolanic or hydraulic properties and performance in sulfate environments. Experiments were carried our by supplementing cement by weight in concrete mixes with CCA at 5%, 7.5%, 10%, 15%, 20%, 25% and 30% steps at the point of need. Results were compared with a control specimen, which was made with 100% cement. Durability was tested using the sulfate elongation test. The results showed impressive compressive strengths that were suitable for structural applications. It was concluded from the sulfate elongation test that CCA supplemented concrete could be used in aggressive environments with an advantage. The results showed good repeatability and highlight the potential of CCA as an effective pozzolan, which could enhance the sustainability and economic aspect of concrete, as well as improve its properties in both the wet and hardened states.
 
Keywords: Cementitious materials, corncob ash, partial cement replacements, pozzolans.

Cite: John Kamau, Ash Ahmed, Paul Hirst, Joseph Kangwa, "Suitability of Corncob Ash as a Supplementary Cementitious Material," International Journal of Materials Science and Engineering, Vol. 4, No. 4, pp. 215-228, December 2016. doi: 10.17706/ijmse.2016.4.4.215-228