Microstructural Evaluation of Cement Mortar Modified with Treated Wastewater under Varying Mixing and Curing Conditions

ABSTRACT Water scarcity impedes access to safe drinking water for billions and hampers global development initiatives. Conservation and reuse of potable water in concrete or mortar production is of great interest to fostering sustainable resource management in the construction industry. This research study sought to evaluate the comprehensive superiority of using alternative water sources in the construction industry. The use of treated wastewater at secondary and tertiary treatment levels for preparing cement mortar was evaluated. To simulate worst-case scenarios, treated wastewater was utilized in both mixing and curing. Municipal- and industrial-treated wastewater were selected to evaluate the fresh, mechanical and microstructural properties of cement mortar. Rheological behavior was assessed to investigate the flow properties of tap water and treated wastewater. Toxicity characteristic leaching procedure (TCLP) test was conducted on 90-d cured samples to examine leaching potential. The test results revealed variations in yield stress and plastic viscosity with change in water quality. Industrial-treated wastewater increased the initial and final setting times by 45 and 70 min, respectively. Secondary-treated wastewater used for both mixing and curing showed a 13 % reduction in compressive strength and a 21 % reduction in flexural strength at 28 d compared to the control mix. Microstructural analyses (scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy) indicated that treated wastewater had no significant adverse effects on concrete or mortar properties. Furthermore, TCLP results confirmed the absence of heavy metals even after longer curing periods. The findings showed that secondary-treated wastewater can be safely used for concrete production with acceptable strength performance and regulatory compliance. This confirms its suitability as a sustainable alternative to potable water.