Performance evaluation of sustainable recycled aggregate concrete with colloidal nano-silica

Abstract

The use of recycled coarse aggregate (RCA) in concrete is a sustainable thing in the concrete industry. But during the recycling process of concrete waste for RCA, some mortar will be adhered to it and the coarse aggregate may have got fractured; if it was used in making the recycled aggregate concrete (RAC), it may produce inferior-quality RAC. To enhance its mechanical and microstructural characteristics of RAC, an admixture in the form of colloidal nano-silica (CNS) which are highly reactive in producing C-S-H gel with the hydrated cement and effectively fill the microvoids and crack in RAC and improves the interfacial transition zone (ITZ) was considered in the present experimental investigation with 100% replacement of natural coarse aggregate (NCA) with RCA and partially replacing the cement with CNS (0%, 1%, 2% and 4% by weight). The detailed analysis of the experimental results revealed that the replacement of cement with CNS in both the NAC and RAC mixes has enhanced the mechanical and microstructural characteristics; most notably, reduction in voids and improvement in the ITZ. The concrete mixes even with 100% RCA and partial replacement of cement with CNS satisfies the design requirements for its application in the construction industry.