Effect of recycled aggregate treatment methods by pristine graphene on mechanical and durability properties of concrete

Abstract

Using recycled concrete aggregates (RCAs) in concrete is a promising approach to minimise the environmental impacts associated with construction and demolition waste while simultaneously enhancing the sustainability of concrete. Improving the quality of RCAs is crucial for promoting confidence among materials suppliers and systematic utilisation of RCAs in construction. Pristine graphene (PG) suspensions (0.1% and 0.2% concentrations in water) were investigated for improving the properties of RCAs and thereby improving the mechanical and durability properties of concretes made with 100% RCAs as coarse aggregates. Two PG treatment methods were used – spraying and soaking. Nano-silica (NS) suspensions of the same concentrations were also used for comparison. Tests for axial compressive, splitting tensile and flexural strengths were performed; water absorption and drying shrinkage were also assessed. Microanalysis was conducted using scanning electron microscopy and micro computed tomography. PG was found to be more effective than NS for increasing strength properties and reducing water absorption and drying shrinkage of concrete due to its lower porosity. For a given nanomaterial concentration and type, concretes made with soaked RCA exhibited higher strengths and lower water absorption and drying shrinkage than concretes with sprayed RCA. The concretes made with soaked RCA also had lower porosity and fewer microcracks. The results are promising and indicate that treating RCAs reduces their water absorption, thereby improving concrete performance.