Application of concrete produced from reused ready-mixed concrete wastewater filtration residue

Abstract

During the production of ready-mixed concrete, waste slurry was filtered under pressure to obtain Wastewater Filtration Residue (WFR). Physical and chemical analysis of the WFR was conducted using methods such as XRD, SEM. The flowability and activity index of the cement mortar with composite admixtures, prepared by replacing fly ash (FA) with WFR powder at weight ratios of 0%, 25%, 50%, 75%, and 100%, were tested. Different strength grade concretes were prepared by replacing FA at weight ratios of 0%, 25%, and 50%, and replacing fine aggregate at weight ratios of 0%, 5%, and 10%, in order to analyze the variation of concrete strength. The results indicate the following: 1) The WFR was primarily composed of fine particles with various shapes and loose surfaces, making it suitable for concrete preparation. 2) WFR had poor flowability (59.83%) and hydration activity (51.7%), but FA addition improved both. Increasing FA content enhanced flowability ratio and hydration activity. At 1:1 FA-to-WFR ratio, flowability reached 81.44% and hydration activity reached 75.73%. 3) When WFR replaced FA (25%, 50%) or manufactured sand (5%, 10%) in concrete preparation, the strength of the concrete decreased with an increase in the WFR content. In low-strength grade concrete, the strength reduction was significant when WFR replaced FA. However, the strength reduction was less influenced by the design strength of the concrete when WFR replaced manufactured sand. 4) It was recommended to replace fine aggregate with WFR for concrete preparation, with the replacement ratio not exceeding 10% by weight.