Influence of surface treatment of recycled aggregates on mechanical properties and bond strength of self-compacting concrete

In the last decade there has been a massive growth for development of concrete infrastructures all around the world. Take into account environmental concerns, concrete technology should direct efforts toward assuring development and fabrication of sustainable and resilient concrete. For this purpose, incorporation of recycled concrete aggregate in concrete products particularly self-compacting concrete (SCC) for structural and non-structural application would be significant achievement. In this study the fresh and hardened properties of SCC prepared by substituting natural aggregates (NA) with recycled coarse aggregates (RCA). In addition, bonding behaviour of reinforced RCA-SCC for structural application was investigated. Moreover, surface treatment of RCA using lithium silicate solution was proposed to investigate its feasibility to improve the fresh and hardened properties of SCC as well as its bonding strength. The mechanical properties including compressive strength, tensile strength and elastic modulus of SCC mixes using untreated RCA and treated RCA (TRCA) were investigated. The results showed an improvement in performance of SCC mixes made with TRCA in compare with the untreated samples. The bond behaviour between SCC made with RCA and steel reinforcement was studied and the relationship between the brittleness and bonding of SCC mixes using untreated RCA and TRCA determined. The effect of surface treatment on the interfacial transition zone (ITZ) between adhered mortar and RCA studied using scanning electron microscope (SEM). It was determined that the treatment of RCA improved the bond at the ITZ through densification. The results gave experimental evidence of the suitability of RCA-SCC for structural use and application in reinforced concrete.