Feasibility study of using wash water from ready mixed concrete plant and synthetic wastewater based on tap water with different total dissolved solid to produce self-compacting concrete

Abstract

Lack of freshwater, especially in arid climates, persuades many countries to work on optimized water consumption. One of the industries, which uses a vast amount of tap water for producing concrete is construction. In this regard, researchers encourage to study the feasibility of using wash water from ready-mixed concrete plants or different types of wastewater instead of tap water in the concrete. In the present work, the workability, mechanical, and durability properties of the self-compacting concrete (SCC) with 0.5 water to cement (W/C) ratio, 400 kg/m3 cement, and 175 kg/m3 limestone powder was studied. The Visual Stability Index (VSI) and the slump flow time(T50) results indicate that the use of wash water from the ready-mixed concrete plant or synthetic wastewater negatively affects the workability of SCC compared with the control sample(C). Besides, the results of the J-ring and column segregation index of different SCC specimens increased in comparison with the control sample. However, all mentioned workability is in the range of Integrated Command Accounting and Reporting(ICAR) System recommendations. It means that using wash water and synthetic wastewater in SCC may be applicable in practice regarding workability. The 28 days compressive strength of all SCC specimens using wash water or synthetic wastewater instead of tap water was reduced, excluding concrete using synthetic wastewater containing 1000 mg/L Total Dissolved Solid (TDS) that increases the compressive strength by 13.35%. The compressive strength of concrete using the wash water from the ready-mixed concrete plant decreased by 2.87% compared to control specimens. The 28 days of flexural strength of SCC specimens using wash water or synthetic wastewater were increased, except using synthetic wastewater with TDS of 5000 and 10,000 mg/L, which flexural strength decreased. The use of synthetic wastewater or wash water instead of tap increased 30- minute water adsorption compared to control samples, except for synthetic wastewater with a TDS of 1000 mg/L. The Rapid Chloride Permeability Test (RCPT) results of the SCC sample are in the low permeability range, except for applying synthetic wastewater with a TDS of 10,000 mg/L. The Scanning Electron Microscope (SEM) images also confirmed a decrease in durability and compressive strength when using wash water or synthetic wastewater with TDS of 3000,5000 and 10,000 mg/L. As a general, wash water from ready-mixed concrete plants and synthetic wastewater with different TDS using in SCC need further research for using them in practice.