Effects of pozzolan additives on mechanical and microstructural properties of concrete made with 100% recycled aggregate

Abstract

Reusing recycled materials made from concrete wastes is one way of preserving natural resources and promoting sustainable development. The effect of pozzolan additives (silica fume (SF) and nanosilica (NS)) on the strength, durability and microstructural properties of concrete made with 100% recycled aggregates (RAs) was investigated in this study. The concrete mixtures were made with complete substitution of natural aggregates with the same grading of RAs. As proportions of the cementitious materials, the contents of SF were 0%, 5%, 10%, 15% and 20% and the contents of NS were 0%, 1%, 2%, 3% and 4%. Compressive strength, tensile strength, flexural strength, water permeability and chloride permeability were measured at 7, 28 and 90 days. Microstructural investigations were performed using scanning electron microscopy on selected concrete mixtures. The test results showed that the addition of the pozzolan additives improved microstructure and strength and durability properties of the concrete made with 100% RA. According to the results, a concrete mixture with 15% SF content is a suitable and environmentally friendly replacement for ordinary concrete.