Low Carbon Recycled Aggregate Concrete: Roles of Slag and Silica Fume

Recycled coarse aggregate from construction demolition waste offers a promising and sustainable solution to overcome challenges facing the construction industry, in relation to the increasing landfill areas, decreasing natural aggregate reserves, and increasing environmental impact of concrete production. Previous studies have shown that recycled aggregate concretes (RAC) are, however, more susceptible to deterioration. This paper presents an experimental investigation to improve the performance of concretes manufactured with locally produced recycled coarse aggregate in the UAE. More specifically, it aims to investigate the potential of incorporating ground granulated blast-furnace slag (GGBS) and silica fume (SF) in RACs, and their influence on key engineering properties of concrete. It is shown that partial replacement of Portland cement with GGBS and SF is effective to reduce the resistance of RAC to chloride ion penetration (hence durability), and lower the drying shrinkage and CO2 emissions, with minimal influence on the long-term mechanical properties. A reduction of approximately 40% in CO2 emissions was found in a concrete mix with combined replacement of recycled and waste materials.