Utilization of Coal Combustion Residues as Supplementary Cementitious Materials for Sustainable Concrete

Carbon dioxide emissions from cement production are a current environmental challenge. This research attempted to evaluate the pozzolanic reaction of residuals from coal-fired power plants, such as coal bottom ash (CBA) and coal boiler slag (CBS), as a supplementary cementitious material to lessen the deleterious effect on the environment. The residues’ fineness modulus and specific gravity were determined using the No. 325 sieve and Le Chatelier flask, respectively. Chemical characterizations were conducted using X-ray diffraction (XRD) and X-ray fluorescence (XRF). The results indicated that the percent passing of both residues was greater than 66%, as the American Society for Testing Materials (ASTM) requires, and their specific gravity was comparable to that of cement. Subsequently, in concrete specimens, 20% of the weight of cement was replaced by CBA and CBS to determine the strength development of fresh and hardened characteristics compared with the control specimens. Experimental findings revealed that by the 90th day, concrete made with CBA achieved 98% of the compressive strength of the control concrete, while the concrete made with CBS reached 79% of the control concrete’s compressive strength. Moreover, CBA-based concrete achieved 97% of the flexural strength of the control concrete, while CBS-based concrete outperformed the control by 2% on the 90th day. A lower severity level of chloride ion penetration by both CBA- and CBS-based concrete was achieved in the rapid chloride penetration test, indicating the durability of the concrete.