Combined effects of supplementary cementitious materials (silica fume, GGBS, fly ash and rice husk ash) and steel fiber on the hardened properties of recycled aggregate concrete

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Recycled aggregate concrete (RAC) is now getting much more attention than ever as a likely substitute for natural aggregate concrete, credited to the growing interest of many countries towards the sustainable environment and economy. To increase the goodwill of RAC its performance in terms of strength and durability needs to be optimized. This research article presents the effects of combined incorporation of supplementary cementitious materials (SCMs) and hook-ended steel fibers (HSF) on compressive behavior and durability of RAC. In this study, four different SCMs (i.e. silica fume (SF), ground granulated blast furnace slag (GGBS), fly ash (FA), and rice husk ash (RHA)) were used in RAC with 0% and 1% HSF, respectively. SF, GGBS, FA, and RHA were respectively used as 10%, 30%, 20%, and 15% by mass replacement of ordinary Portland cement (OPC). Studied properties included compressive strength, elastic modulus, splitting tensile strength, water absorption (WA), chloride penetration (CP), and acid attack resistance (AAR). The results of testing indicate that mechanical strength and durability of RAC can be improved substantially by the combined incorporation of SCMs and HSF reinforcement. SCMs show more contribution towards the development of durability properties of RAC, whereas, HSF shows more contribution towards the development of mechanical properties and AAR. 10%SF + 1% HSF and 15%RHA + 1% HSF helped in the production of RAC having superior mechanical and durability properties compared to that of the plain RAC. Moreover, the benefits of combined addition of HSF and SCMs are notably higher than the sum of the benefits achieved through individual incorporation of HSF and SCMs.