Reliability of using secondary and tertiary treated wastewater in concrete mixing and curing

Abstract

Water scarcity is a problem that faces many regions. In a developing and arid countries, the need for fresh water is exponentially increasing. One of the most water consuming industries is the construction industry, especially in concrete manufacturing. This research is an evaluation of the Reliability of recycled wastewater to be used in concrete manufacturing. Two different wastewater treatment regimens are implemented: secondary and tertiary treated wastewater. The treated wastewater, either secondary or tertiary, replaces potable water with percentages of 25%, 50%, and 100%. The mixture of the two types of water is used in concrete mixing and curing. Control specimens with pure potable water are cast for the comparison. The experimental program investigated the cement setting, and for fresh concrete slump test is performed on all concrete mixtures. The hardened concrete is tested in compression and flexural strengths at ages of 7 days, 28 days, and 90 days. To investigate concrete durability, permeability test is conducted in addition to sulfate attack resistance. The concrete chemical composition is compared using the X-Ray Defragmentation (XRD) test. The results show that the treated wastewater may delay both the initial and final setting. The phenomenon is more pronounced in secondary treated wastewater. No significant effect on concrete performance in the fresh state is detected. For the compressive strength, both treatment regimens can be safely used. However, the flexural strength is reduced at the late ages. Using treated wastewater affects the permeability of concrete to be more durable and protect the reinforcement steel from rusting. For the XRD test, the results show different intensities and positions of the peaks of the different compounds encountered in the treated wastewater. Under sulfate attach, the treated wastewater specimens give higher expansion compared with potable water. In conclusion secondary and tertiary treated wastewater can be used in concrete mixing and curing. However, the manufactured concrete should be protected from sulfate attack to avoid excessive expansion.