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.

Concrete usage is increasing rapidly; subsequently, the industry’s carbon footprint is increasing and impacting the environment significantly. Large amounts of fine and coarse aggregate, including cement, are needed to fulfill the increased demand, leading to increased natural aggregate usage. Therefore, finding a fine aggregate replacement in concrete is essential. Coal bottom ash (CBA) and coal boiler slag (CBS), byproducts of coal-burning power plants with pozzolanic properties, can replace fine aggregate in concrete to reduce global natural material depletion, health hazards, and technical and economic problems associated with power plants’ solid waste. This study was conducted to determine the optimum fine aggregate replacement amount of CBA and CBS in concrete while improving concrete performance. The optimum CBA and CBS content is 50%, which reduces fine aggregate usage in a concrete mix by 50% while maintaining equivalent or better concrete strength than the control. The optimum CBA content has a unit weight lower than the control for all mixes tested in this study, which makes the CBA mix lightweight concrete. The optimum CBA concrete has 15%, 43%, and 42% higher compressive strength than the control after 7 days, 28 days, and 56 days of curing, respectively. On the other hand, the optimum CBS concrete has 12%,16%, and 16% increased compressive strength than the control after 7, 28, and 56 days of curing, respectively. The compressive strength of optimum CBA concrete was higher than the optimum CBS, indicating that CBA concrete yields higher compressive strength than CBS, possibly due to the difference in physical properties, water absorption capacity, and bulk density. Nanoclay increased CBA concrete compressive strength at an early stage and increased the optimum content to 80% CBA. Therefore, using CBA and CBS can significantly reduce natural material usage and environmental harm by reducing CBA waste disposal and improving concrete performance.

Coal bottom ash (CBA) is a byproduct of coal-burning power plants. This material can be used as a fine aggregate replacement in concrete to reduce global natural material depletion. Concrete usage is increasing rapidly; subsequently, the industry’s carbon footprint is increasing. Using CBA in the construction industry will reduce the technical and economic problems associated with power plants by reducing solid waste. This project aimed to determine if adding new sustainable materials, such as CBA, to concrete will reduce natural raw material usage, energy consumption, and greenhouse gas emissions while improving performance. This study included two projects: comparing increased CBA content to the two-control project and determining the optimum content based on the compressive strength. The optimum CBA content is 50%, which reduces fine aggregate usage in a concrete mix by 50% while maintaining equivalent or better concrete strength than a pure Portland concrete mix without CBA. The air content of the concrete mix containing % CBA decreased with increased CBA content and compressive strength, possibly due to the spacing factor of the voids in the mix and CBA’s porous and fineness behavior. The CBA optimum content had a unit weight lower than the controls for both projects, which makes the CBA mix a lightweight concrete. Using this material can significantly reduce natural material usage and environmental harm by reducing CBA waste disposal and improving concrete performance.