LAUSR

Abstract Returned fresh mix concrete (RFC) is a problem with both economic and environmental impacts. Therefore, investigators have recommended various ways to decrease the amount of RFC in manufacturing facilities. Among the most common procedures are dumping concrete in landfill, recycling it, using the aggregate, and using it to produce concrete blocks. In this study, the authors investigated the behavior of various proportions of RFC mixed with ready-mix plain and retarded concrete. The authors also studied the influence of aging by producing specimens after one, two, three, and four hours. In addition, the researchers investigated controlled and uncontrolled environments by mixing the samples both indoors and outdoors. Workability, setting time, and compressive strength of cylindrical mixed specimens was then evaluated. The results presented acceptable setting times and compressive strengths for most specimens, which means mixing RFC with ready-mix concrete is a suitable alternative for recycling RFC. It is also possible to mix higher proportion of RFC with plain concrete in comparison to retarded concrete, though it is difficult to estimate the optimum combination of RFC and plain concrete.