Cement production requires considerable energy and natural resources, severely impacting the environment due to harmful gas emissions. Coal bottom ash (CBA) and coal boiler slag (CBS), byproducts of coal-fired powerplants having pozzolanic properties, can be mechanically ground and replace cement in concrete, which reduces waste in landfills, preserves natural resources, and reduces health hazards. This study was performed to determine the optimum cement replacement amount of ground CBA (GCBA) and ground CBS (GCBS) in concrete, which was 10% for GCBA and 5% for GCBS. GCBA-based concrete exhibited superior tensile strength, modulus of elasticity, and durability compared to the control. In the Rapid Chloride Penetration Test, 10% GCBA concrete resulted in 2026 coulombs at 56 days, compared to 3405 coulombs for the control, indicating more resistance to chloride penetration. Incorporating 2.5% nanoclay in GCBA-based concrete increased the optimum GCBA content by 5%, and the compressive strength of 15% GCBA concrete increased by 4 MPa. The mortar consisting of the finest GCBA(L1) having Blaine fineness of 3072 g/cm² yielded the highest compressive strength (32.7 MPa). The study discovered that the compressive strength of GCBA and GCBS-based mortars increases with fineness, and meeting the recommended fineness limit in ASTM C618 enhances concrete or mortar properties.

Cement production requires a significant amount of energy and natural resources, severely impacting the environment due to harmful gas emissions. Coal Bottom Ash (CBA) and Coal Boiler Slag (CBS), byproducts of coal-fired power plants, have pozzolanic properties. CBA and CBS can be mechanically ground to obtain Ground Coal Bottom Ash (GCBA) or Ground Coal Bottom Slag (GCBS), which can potentially replace cement in concrete, reducing waste in landfills, benefit the economy, preserving natural resources, and reducing health hazards. This study was performed to determine the optimum amount of GCBA and GCBS that can replace cement in concrete. The fresh, mechanical, and durability properties of the concrete containing GCBA were compared to a control mix consisting of 100% Portland cement. The optimum amount of cement replaced with GCBA and GCBS was 10% and 5%, respectively, based on compressive strength. The GCBA-based concrete's tensile strength, modulus of elasticity, and durability properties were better than the control. The compressive strength of the GCBA and GCBS-based mortars increased with an increase in fineness. GCBA and GCBS fineness should be within the limit recommended in the ASTM C618 standard to enhance concrete or mortar properties.

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.