A massive amount of industrial waste is readily available for civil engineering works. However, even a small amount can cause serious ecological problems. Global warming, on which cement production has a significant impact, has led to greater awareness of cement replacement materials. In this study, composites of alluvium clay with various percentages of cement (7%, 10%, and 13%) and two different proportions of coal bottom ash (20% and 40%) in two different densities (1,600 and 1,800 kg/m(3)) at 7, 28, and 60 days of curing period were prepared to investigate engineering properties, microstructure, and sustainability performance. Porosity, strength, and initial shear modulus values of composites were determined and strength-porosity relationships were proposed for these materials at all curing ages. The microstructure of the composites was investigated to evaluate the mechanism of the chemical reactions. The 20% coal bottom ash replacement level showed the highest strength (approximate to 30% compared with control samples) and the highest improvement in the initial shear modulus. Samples with 13% cement and 40% coal bottom ash showed an 8% reduction in porosity at 60 days. The proposed relationships could be valuable to estimate the engineering properties of coal bottom ash clay blends and promotes higher waste utilization in civil engineering applications based on the coal bottom ash content and density. Additionally, the sustainability performance of laboratory-produced composites was analyzed based on equivalent carbon dioxide (eCO(2)) emission, embodied energy, and cost calculation. This study may help to evaluate the performance of composites composed of waste and promote sustainable construction works.