Abstract
This paper reports the characteristics of the pozzolan generated at different temperatures and times of exposure for the calcining process of millet husk for the determination of optimum metrics of production. Some millet husk samples were procured from a market in Nigeria and cleaned to remove sand and other impurities. The cleaned husks were burned in a muffle furnace at temperatures of 600 ⁰C, 750 ⁰C, and 900 ⁰C, with a dwelling time of 2 hours and 4 hours each. The six resulting brands of the ashes were analysed for chemical composition using X-ray fluorescence Spectrometry and further evaluated for pozzolan classification. The microstructure of the millet husk ash (MHA) calcined at 900 ⁰C and a 2-hour dwelling time, the optimum condition, was investigated through the scan electron microscope. The summation of SiO2, Al2O3 and Fe2O3 content of 92-96%, which is more than 70% benchmark for Class C ASTM C618-12 quality pozzolan, was computed for the MHA produced at 750 and 900 ⁰C calcination temperatures and the two dwelling times; while the corresponding values were 62-63% for the specimen produced at 600 ⁰C in the furnace closed environment, implying a different brand of pozzolan. Further, the per cent silica content of the MHA brand calcined at 600, 750, and 900⁰C for a dwelling time of 4 hours is less than those of the 2 hours (32.8%, 55.2% and 52.1% respectively as against 34.2%, 55%, and 58.3%), making the 900 ⁰C temperature and 2 hours calcination period the most optimum production metric for high silica content pozzolan from millet husk bio-wastes.

Key words: Temperature Pozzolan, Pearl millet husk, Calcination, Bio-wastes