An investigative study on the feasibility of wastewater use in concrete production

Abstract

This report presents findings on the effects of the use of waste water in placement of potable water in concrete production with regards to effects on properties of concrete structures and cost implications. Like many low income countries, Uganda is struggling with wastewater management and experiences water supply deficit which makes it difficult to meet the Sustainable Development Goal (SDG6) related to sanitation. On the other hand, the construction industry is growing tremendously. With this growth comes an increase in demand for construction materials and other inputs required for construction. This research is centered on concrete as a popular construction material; taking up over 70% of most structures and large amounts of water consumed in its production. This research thus sought to find an alternative to using potable water; by incorporating wastewater in concrete production, which could possibly reduce the cost of concrete production and demand for potable water. In this research, a number of tests, for instance water tests such as TSS, Salinity, pH, chloride and sulphate ion tests were performed as well as Concrete tests such as compressive strength, workability, carbonation and water absorption tests, to find out the feasibility of using wastewater in concrete production. Waste water was found to be more saline and alkaline in comparison to the Potable water. Concrete mixed with waste water had a greater slump value than that mixed with potable water making it more workable. It was seen that all concrete cubes cast with waste water had compressive strength that deteriorated at 14 and 28 days in contrast to those mixed with potable water. Carbonation was seen to have taken place in cubes cast with use of wastewater with a depth of carbonation of 6mm. Water Absorption tests performed also revealed that all cubes cast with waste water were more porous in comparison to those mixed with potable water making it prone to cracking and corrosion of reinforcement due to possible ingress of harmful substances. Despite this, using waste water in concrete production proved to be more cost effective during production of concrete but shall however call for more futuristic costs during the lifespan of the structure.