Feasibility of using clay-free bricks manufactured from water treatment sludge, glass, and marble wastes: An exploratory study

The global generation of millions of tonnes of water treatment sludge (WTS) per day is triggering waste management problems and the up-cycling of WTS in masonry bricks is an eco-friendly solution. Effect of different dosages of WTS on the performance of clay bricks has been studied by researchers. Scant work is available regarding the performance of no-clay bricks i.e. bricks made exclusively with the WTS. This study aims to investigate the engineering performance of no-clay bricks having WTS, glass, and marble wastes. For this reason, WTS bricks are manufactured with different dosages of glass and marble wastes (i.e. 0–15%). Mechanical, durability, thermal, and microstructural performance of all the brick specimens is explored. X-ray fluorescence results show that the collective amount of fluxing agents in WTS exceeds 9% (similar to low refractive clay). All the bricks manufactured in this study exhibited water absorption between 5.3 and 12.6% and can be classified as first-class and severe weather resistant bricks as per ASTM C373-18 and ASTM C62-17, respectively. The thermal conductivity and porosity of no-clay WTS bricks were observed 1.014 W/mK and 11%, respectively. Moreover, the higher compressive strength and bulk density of all the brick specimens fulfill the international building code obligations. Furthermore, no-clay WTS bricks meet the ASTM C902 and ASTM C62-17 requirements for light vehicular traffic and severe weather-resistant bricks, respectively. Empirical relationships between the compressive strength, thermal conductivity, porosity, and density of brick specimens developed in this study can be used to predict the performance of WTS bricks. Therefore, no-clay WTS bricks having glass and marble wastes can be used to produce strong, durable, and sustainable buildings leading towards a cleaner environment and natural clay conservation.