Author : Muhammad Qamer, Arslan Ashraf, Mahboob Anwar Shad, Waqas Haider, Muhammad Awais Jan, Muhammad Usman, Muhammad Baqi Billah and Muhammad Ibrahim

The current study addresses the effect of substitution of silica fume and nanosilica on the mechanical and durability properties of self-compacting concrete containing recycled coarse aggregate (RCAs). A self-compacting concrete (SCC) was prepared by the incorporation of silica fume and nanosilica as a replacement of cement. Two series of concrete mixtures were prepared in the laboratory. In these series, RCAs with the replacement of 25%, 50%, 75%, and 100 % respectively were used with and without supplementary cementitious materials (SCMs). J-ring and Slump flow tests were conducted to investigate the fresh properties SCC. The incorporation of supplementary cementitious materials enhanced the properties of SCC and the result showed that the use of these cementitious materials can reduce water absorption and chloride diffusion up to a great extent. The mechanical and durability properties of SCC were determined by different tests like compressive strength test, water absorption test, and rapid chloride migration test. The use of cementitious materials showed a better result after 90 days of compressive strength. The test results indicate that silica fume and nano-silica were very effective and have great resistance against chloride diffusion.

Keywords: Recycled concrete aggregate, Silica fume, Self-compacting concrete, Water absorption, Chloride diffusion