Mechanical Study of the Utilization of Niger Coal Bottom Ash as an Additive in Cement Production

Abstract

CBA (coal bottom ash) is an industrial waste generated by coal fired thermal power plant. In this work, we investigate the utilization as an additive material in composite cement of CBA resulting from the firing of the coal extracted in Tefereyre mine (TCBA) in a thermal power plant in Niger. Our investigations are carried out by using compressive mechanical tests on 40 × 40 × 160 mm 3 mortar specimens. These mortar specimens are made with a partial substitution of the cement by TCBA at levels of 0%, 5%, 10%, 15%, 20% and 25% by mass. The tests were performed on the specimens at 7, 14, 28, 45 and 56 days of age. The results were used to evaluate the pozzolanic activity index as the ratio of the compressive strength of mortar containing 25% of coal bottom ash on that of the control mortar containing 100% of cement, according to ASTM C618. From these data, the maximum rate of TCBA addition in Portland cement was derived. It was found that TCBA has a pozzolanic activity index of about 71% at 28 days and displays a maximum substitution rate of 15% in Portland cement. These results strongly support the development of composite cement using TCBA.