Flexural behavior of reinforced concrete beams prepared with treated Wastewater, recycled concrete Aggregates, and fly ash

Utilizing treated domestic wastewater (TWW), recycled concrete aggregates (RCA), and fly ash (FA) in reinforced concrete (RC) structures is of great interest from a sustainability perspective. In this study, four RC beams (180 x 250 x 2000 mm) were fabricated and tested under a four-point bend flexure until failure. The test parameters include mixing water type (fresh water and TWW), coarse aggregate type (natural gabbro and RCA), and FA content (0% and 20%). The results suggested that the use of TWW, RCA, and FA had no significant effect on the beams' cracking patterns and reinforcement strain at yielding, whereas TWW and RCA decreased the beams' ductility by 8.7% and 15.9%, respectively. In addition, TWW reduced the beams' flexural capacity by 13.7%. On the other hand, the use of FA increased the beams' cracking and ultimate loads and concrete maximum strain and negligibility increased the ductility. The analytical investigations revealed that the ACI 318-19 code accurately predicted the beams' cracking moments, while the CSA-A23.3-14 code showed the least prediction error for the beams' ultimate moments. Additionally, the CSA-A23.3-14 showed an accurate prediction of the beams' load-deflection responses.