Assessment of Mechanical Properties of Environmentally Friendly Concrete with Emphasis on Selection of Optimal Mix Designs in Terms of Resistance and Economy

The main purpose of this study is to investigate the possibility of constructing environmentally friendly concrete. To achieve this purpose, the concrete waste was recycled and reused in constructing concrete. On the other hand, due to the high volume of environmental pollutants in the ordinary Portland cement (OPC) manufacturing process, OPC was replaced with ground granulated blast furnace slag (GGBFS). Therefore, this study was investigated the mixing designs by 0, 50 and 100% natural aggregates (NA) replaced with recycled concrete aggregates (RCA) and 0, 15, and 30% OPC with GGBFS. In addition, the mixing designs were reinforced with 0, 0.5, and 1% hooked-end steel fiber. In total, this study was investigated 27 different mix designs containing RCA, GGBFS, and steel fibers. Various tests such as slump, water absorption, UPV, compressive, splitting tensile, and flexural strength were performed on specimens. The results showed that using RCA and GGBFS had a negative effect on the workability and compressive strength of concrete. Finally, by economic analysis and optimization of mixing designs, it was concluded that it is justified in terms of resistance and economy to use RCA as a replacement for NA to 50% and the use of GGBFS as a replacement for OPC to 30%. Furthermore, the results showed that the weakness of using RCA and GGBFS can be compensated by adding steel fibers.