Assessment of Sustainable Composite Fly Ash Bricks Prepared using Kiln Wastes

Abstract

An increasing demand for sustainable construction materials is required for a reduction in the consumption of natural clay and an increase in the beneficial use of industrial waste. This study aims the investigation of the possibility of using Brick Kiln Dust (BKD) and fly ash as partial replacements of conventional clay for clay brick production. Brick specimens were prepared with different replacement levels of BKD (0, 5, 10, 15, 20 and 25%) and their physical, mechanical, durability and non-destructive properties such as unit weight, weight gain, apparent porosity, water absorption, compressive strength, modulus of rupture, sulfate resistance and Ultrasonic Pulse Velocity (UPV) were assessed. The results indicated that the increase in BKD content resulted in a decrease in the unit weight from 107 to 102 kg/m², an increase in the apparent porosity from 35.54 to 38.11%, and an increase in water absorption from 21.85 to 24.30. The compressive strength decreased from 9.13 to 5.95 MPa, and the percentage strength reduction after the sulfate attack increased from 16.6 to 25.9%. UPV decreased from 1944.34 to 1556 m/sec at higher BKD contents indicating less internal compactness. In general, low to moderate BKD replacement levels, especially 5–15%, provided a better compromise between waste utilization and engineering performance, while higher replacement levels require further adaptation. Besides, fly ash provides further opportunities for particle packing improvement, with environmental benefits and increased sustainability for BKD-based bricks. The proposed technique can lessen the reliance on fertile clay, prevent the dumping of brick-kiln waste and assist in the creation of greener masonry materials.