Feasibility of Using Calcined Water Treatment Sludge in Rendering Mortars: A Technical and Sustainable Approach

Abstract

Many current industrial processes, such as water treatment, produce large amounts of waste. The water treatment sludge (WTS) must be properly disposed of and/or used as raw material for application in other sectors, such as the construction industry. The rendering mortar production can be an environmentally friendly alternative to recycle the WTS, this being the object of this research. In this way, mortars were produced with 2.5%, 5%, 7.5%, and 10% calcined WTS to replace natural sand. The water absorption, compressive strength, bond strength, and flexural strength properties were evaluated. A natural carbonation was carried out for the determination of CO2 uptake due to carbonation. The results showed that the incorporation of calcined WTS has an influence on all the properties evaluated. Considering 50 years of service life, the CO2 uptake potential for mortar with 10% calcined sludge WTP is 111 kg CO2/t. In the sustainability approach, it was observed that CO2 uptake due to carbonation is higher in mortars with the addition of WTS, and could be an environmentally friendly alternative that compensates emissions from the cementitious materials production.