Influence of concrete mixer washing waste water on the chemical and mechanical properties of mortars

Abstract

The world's population will be facing water shortage problems by 2050. Recycling and treatment of residual water and reusing it in real life applications may help to solve this problem. However, the total cost of the treatment processes is estimated to be very high. The reuse of concrete mixer washing waste water without previous treatment may contribute to a significant reduction in the cost associated with the treatment process. This process may also reduce the consumption of drinking water, which is used by default in concrete fabrication and for washing purposes in concrete plants. This research paper studies the feasibility of reusing washing water of concrete mixer trucks without treatment to fabricate cementitious matrices and evaluates its influence on their chemical and mechanical properties. An experimental program was conducted by using 3 different types of waste water from washing concrete mixer trucks. The hydration kinetics of cement pastes was evaluated by isothermal calorimetry. Mortar workability was studied by the consistency index. The properties of mortars in the hardened state were evaluated by determining their porosity, tensile and compressive strength. Results showed that the waste water did not significantly influence the hydration kinetics nor the properties of the fresh and hardened state of mortars, indicating its possible use as mixing water to produce cement mixtures with no previous treatment. This research presents a promising sustainability key either for elimination of treatment cost or for water shortage that threatens many regions in the world.The following specific conclusions may be derived from the results obtained in this experimental program: