Influence of Water–Cement Ratio on Performance of Concrete Using Waste Concrete Aggregates

Waste concrete aggregate (WCA) may be used instead of natural aggregate (NA) to produce concrete. This minimizes waste, preserves natural resources, and saves landfill space. While produced with the same concrete mix design, natural aggregate concrete (NAC) can frequently possess better durability and strength than waste aggregate concrete (WAC). Many studies show chemical admixtures may improve these concrete properties. However, the influence of this chemical admixture combined with recycled aggregate concrete (RAC) with different water–cement ratios is not well established. Therefore, this study aims to assess the performance of RAC with different water–cement ratios. A comprehensive experimental study was carried out with different NA replacement ratios (0%, 25%, 50%, and 100%) by waste aggregates as coarse aggregates. Waste stone aggregate (WSA), a specific type of waste aggregate, has been used, and the Los Angeles Abrasion test was conducted, where the abrasion value equaled 40.36%. Superplasticizer was incorporated into half of the manufactured specimens at water–cement ratios of 0.4, 0.45, and 0.5. Results of compressive, splitting tensile, and flexural strengths of concrete with superplasticizers showed significant enhancements, and rapid chloride ion permeability and ultrasonic pulse velocity tests showed significant durability improvements for different water–cement ratios. The compressive strength of WAC was reduced by 17.9%~31.03% without the superplasticizer and 10.43%~28.57% with the superplasticizer of concrete mixes at 28 days from the reference mixes. A similar pattern was shown for concrete tensile and flexural strengths. In addition, WAC’s permeability to chloride ions has been increased. The results demonstrated the potential advantages of employing superplasticizers to improve WAC’s mechanical and durability properties for different water–cement ratios.