Effects of Treated Sewage Water on the Performance of Concrete

In construction industry concrete is commonly used material worldwide, ever since concrete was invented, it has been mixed with drinking water. It is observed that there is an increase in water scarcity with population growth and urbanization. However some studies show that water that is not safe for human use might be used in concrete for mixing and/or curing purposes. In this experimental study; the applicability of treated sewage water on concrete production was tested. For this purpose, set of experiments are performed: slump test; setting time; permeability; compressive, splitting tensile and flexural strengths; sulfate attack; pH test; ultrasonic test and corrosion tests. Collected treated sewage water which was provided from Gazimağusa Sewage Treatment Plant was used. Four different concrete mixes were produced by using potable water (PW) and treated sewage water (TSW) either for mixing and/or curing purposes with 0.47 w/c. Utilization of TSW caused little increase on workability, however it is pointed out that there is no adverse effect on workability. The initial setting time of TSW showed an increament 30 minutes when compared with the initial setting time of PW, showing that TSW slows down the hydration rate of concrete which is an advantage for hot countries. It has not been determined that there is a negative effect on the alkali character of concrete in the use of TSW. It is indicated that utilization of either for casting with TSW (CasT) or curing with TSW (CurT) result in a lower permeability of concrete. It is noted that the use of TSW for mixing or curing improves long-term durability and strength. Using TSW either curing or mixing caused reductions in compressive strength as 8-14% at 28 days. However at 150 days the reductions were between 3-9%. The lowest weight loss was observed in (CasT CurT) mix while the highest was observed in (CasP-CurP, CasP-CurT) mixes for 72- hour exposure time. However, after 168 hours, it is observed that the corrosion rate increased in time for all mixtures. Also the most weight loss was seen in (CasT CurP) as 55% and nearly 20% weight loss was observed in (CasP-CurT and CasT CurT) when compared with CasP-CurP after 168 hours. Keywords: concrete, mixing water, curing water, treated sewage water, mechanical properties, permeability, corrosion.