The effect of using treated domestic wastewater with different pHs on workability, mechanical, and durability...

In the present work, we used treated domestic wastewater with different pHs in self-compacting concrete (SCC) to find the effect of treated wastewater with different pHs on the workability, mechanical, and durability properties of SCC. Eight different SCC mixtures were designed, including two control samples using tap water with a water-to-cement ratio (W/C) of 0.5 with 400 kg/m³ of cement and W/C of 0.36 with 440 kg/m³ of cement. Six SCC samples with the same characteristics as control samples except using treated domestic treated wastewater with different pHs. The results indicate that the workability of the SCC sample using the treated domestic wastewater in acidic pH was higher than the alkalinity state. Using treated domestic wastewater instead of tap water in SCC samples decreased compressive, flexural strength, and fracture toughness by less than 10%. Also, carbonation, 30-min water adsorption, and capillary water adsorption of SCC samples increased when treated domestic wastewater was used. The compressive strength of SCC samples made with treated domestic wastewater in an acidic state is less than about 5% in an alkaline state. The energy dispersive spectroscopy and the scanning electron microscope images confirmed that using treated wastewater instead of tap water, in SCC samples, reduced compressive strength because the Ca/Si ratio increased when treated domestic wastewater was used. The SCC samples with treated domestic wastewater in the alkaline state have a lower Ca/Si ratio. The higher compressive strength belongs to concrete samples that used treated domestic wastewater in an alkaline environment with a lower Ca/Si ratio.