Feasibility Study of Reusing Wash Water and Steel Fibre Simultaneously on Workability, Mechanical Properties and Fracture Toughness of Concrete

Water scarcity is the world's challenging issue, and every day huge amounts of wash water(W) are produced by the concrete batching plants and concrete mixer trucks. Therefore, wash water reuse can be a method of saving water. This experimental work was conducted to determine the feasibility of using wash water in normal concrete and fibre(F) reinforced concrete. Workability and compressive, tensile, and flexural strengths, as well as fracture toughness of concrete specimens, were carried out according to ASTM and BS. The slump test results showed a slight decrease while using wash water or steel fibre and using both of them concurrently. Using wash water instead of tap water increased compressive strength at 7,14 and 28 days. Adding steel fibre in the specimens containing tap water raised compressive strength sharply at all periods. Nevertheless, applying wash water and steel fibre instantaneously in the concrete sample decreased compressive strength. This consequence was confirmed by the SEM image. Both tensile and flexural strength increased while using wash water instead of tap water. The maximum tensile strength was observed when 100% wash water and steel fibre (W + F) were replaced by tap water. Using steel fibre for concrete samples using tap water increased flexural strength by around 14% compared to the control sample. The highest flexural strength was reached while 100% wash water and steel fibre (W + F) were used simultaneously. Substituting wash water with tap water increased fracture toughness, and adding steel fibre to the concrete sample applying tap water similarly raised fracture toughness compared to the control sample. While using wash water and steel fibre in the concrete sample instantaneously, the fracture toughness increased by 49%.

Automated summary

The study confirmed that the use of wash water and steel fiber in concrete may affect the mechanical properties of concrete. While the use of wash water and steel fibers can increase tensile and flexural strength, simultaneous use of both may decrease compressive strength. The maximum tensile and flexural strengths were achieved in concrete samples with 100% wash water and steel fibers, respectively.