Improving the mechanical properties of recycled aggregate concrete with graphene

This article presents the results of a preliminary research to explore the feasibility of using graphene to improve mechanical properties of recycled aggregate concrete (RAC). Graphene of different nominal flake sizes (5, 10 and 20 mu m) and concentrations of 0.01%, 0.02%, 0.05% and 0.1% of the combined weight of cement and sand were incorporated into RAC with and without crumb rubber. The results indicate that there was no improvement in mechanical properties of recycled aggregates (RAs) concrete with crumb rubber. Also, if aggregates were not washed, even without any crumb rubber, adding graphene was not effective in improving mechanical properties of RAC due to excessive dust of unwashed RAs. However, the results reveal that by agitating RAs in water to remove excessive dust, adding small amount of graphene improves the mechanical properties of RAC. By adding 0.01% graphene flakes, the average compressive and splitting tensile strengths of RAC were increased from those of RAC without graphene by 43.9% and 24.1% to 39.14 and 3.76 MPa, respectively, which are comparable to those of concrete using natural aggregates (NAs). However, using more graphene flakes did not result in any further improvement.