A laboratory activity titled “Reusing Treated Wastewater in Concrete” was conducted to investigate the effect of using treated wastewater as a partial replacement for fresh water in preparing concrete mortar and producing compression test cubes. The activity included preparing a concrete mix using treated wastewater and performing the necessary tests to assess its suitability for structural applications. After 7 and 28 days, compressive strength tests were carried out for all cubes using the compression testing machine to measure strength development and compare the results with those of conventional mixes. This activity contributes to enhancing students’ understanding of sustainability and reuse practices in the construction sector.