Eco-friendly cement mortars using waste clay bricks and drinking water treatment sludge

The construction sector significantly contributes to environmental degradation, particularly due to the substantial CO2 emissions associated with cement production. At the same time, large quantities of drinking water treatment sludge (DWTS) and waste clay bricks (WCB) are generated annually, leading to major environmental and logistical challenges due to their accumulation in landfills. In response to these issues, the development of low environmental impact materials incorporating industrial waste emerges as a necessary and sustainable alternative. In this context, the present study explores the potential of using these two types of waste, DWTS and WCB, to formulate a more environmentally friendly cement mortar. Two experimental series were conducted: (i) DWTS was used as a partial replacement for cement at substitution levels of 5%, 10%, 15%, and 20% after being calcined at 800°C for one hour. (ii) In the second series, the DWTS replacement level was fixed at 10%, while WCB was used to replace sand in 25% increments, ranging from 0% to 100%. These mortar's performances were carefully assessed using several important criteria, including bulk density, water absorption, ultrasonic pulse velocity (UPV), compressive and flexural strength. The results show that 10% DWTS substitution led to a maximum compressive strength of 39.24 MPa and a flexural strength of 6.11 MPa at 28 days, compared to 36.34 MPa and 5.22 MPa for the control mix. However, WCB contents above 50% caused a clear decline in performance, with compressive and flexural strengths dropping to 22.87 MPa and 4.47 MPa, respectively, due to its porous and low-density nature. This dual strategy provides a sustainable answer for greener construction methods by drastically lowering CO2 emissions, conserving natural resources, and reusing construction waste. These results show that using DWTS and WCB in cement mortar production is an excellent strategy for mitigating the negative impact of these wastes and protecting the environment.