Sugar cane bagasse ash as a pozzolanic admixture in concrete for resistance to sustained elevated temperatures

In the present investigation, a feasibility study is made to utilize the sugar cane bagasse ash (SCBA) as an admixture in concrete and examine its role in imparting resistance under elevated temperatures. The ash was obtained from a sugar mill in India where the bagasse was recycled as fuel for the mill. It was characterized for its physical properties and chemical composition. Incorporated as a supplementary cementing admixture, SCBA replaced Portland cement from 0 to 25% by mass fraction at 5% increments. Besides a series that was examined at room temperature, the resulting concrete was subjected to elevated temperatures of 300 °C, 400 °C and 500 °C, being exposed for 2 h in each case. The residual compressive and flexural strength were evaluated and compared with the reference performance at room temperature. The results show that the SCBA sample had a grain size distribution very similar to that of the Type GU Portland cement used in this study. X-ray florescence revealed that this ash was chiefly composed of SiO2 (∼70%). At room temperature, the compressive strength of concrete increased till up to 10% SCBA incorporation. Even at 15% cement substitution, it matched that of the reference mix containing Portland cement alone. While there was a consistent drop in the compressive strength at higher temperatures, the inclusion of SCBA marginally slows down this deterioration. On the other hand, the flexural strength of concrete containing SCBA was always lower than that seen with Portland cement alone. However, once again, the drop was seen to be less significant up to 10% cement substitutions. The findings strongly endorse that bagasse ash when used as a supplementary cementing admixture, imparts resistance to concrete against elevated temperatures.