Impact of sulfate activation of rice husk ash on the performance of high strength steel fiber reinforced recycled aggregate concrete

One of the sustainable substitutes for traditional concrete is to incorporate recycled concrete aggregates (RCA) as a substitute for natural aggregates and rice husk ash (RHA) as a partial substitute for Portland cement. Worldwide request for high-strength concrete (HSC) is raising quickly. HSC is very brittle, as it needs some type of reinforcement. Lately, hooked steel fibers (HSF) are gaining momentum in the concrete industry due to their high tensile strength. The problem with RHA-RCA concrete is its low early strength due to which researchers have suggested utilizing chemical activators (sodium sulfate) to enhance the early age strength of RHA concrete. In the present research, compression, and split tensile strength were assessed. For durability properties, water absorption, chloride penetration, sorptivity, and acid resistance test was conducted. It was noted that recycled aggregate concrete with chemically activated RHA had considerably improved strength than samples with no sodium sulfate, particularly in early age strength. The mix (R35-45RHA–SF–A) showed increased compression and split tensile strength among all mixes at 90 days. At 70% recycled aggregate, activated concrete with 45% RHA and 2% HSF displayed enhanced strength to the reference mix. The positive impact of the activator was likewise observed in the durability characteristics of samples with recycled aggregates. X-ray diffraction (XRD) analysis confirmed the development of strength of RHA concrete at later ages. Chemically activation of RHA could be a beneficial answer to address the problem of low strength and durability of RHA modified high strength fiber reinforced recycled aggregate concrete. © 2022 Elsevier Ltd