As a relatively new material, geopolymer concrete offers benefits as a construction material for sustainable development. It utilizes waste materials such as recycled concrete sludge, fly ash, etc. It has a very low rate of green house gas emission when compared to ordinary Portland cement. In this study, the components of geopolymer are concrete sludge, metakaolin and water glass. NaOH was used as an alkaline activator. To improve the mechanical properties, silica fume was added as a bonding matrix from 0%-10% to replace part of the concrete sludge, and the specimens were cured in air, then their mechanical properties such as compressive strength and bending strength were measured and their microstructures were investigated.

Keywords: Geopolymer, Concrete, Silica fume, Concrete sludge, Metakaoli