Performance enhancement and environmental impact of cement composites containing graphene oxide with recycled fine aggregates

The rapidly growing volume of construction and demolition (C&D) waste produced by construction industry has led tremendous pressure on environmental protection. This study focuses on the improvement of the use of C&D waste as recycled fine aggregates (RFA) in cement composites by adding graphene oxide (GO), which is desirable to promote the application of recycled aggregates, decrease the exploitation of natural aggregates (NA) and alleviate environmental burden. In order to investigate the performance enhancement of RFA cement composites, the physico-chemical properties, microstructural performances, and environmental benefits of RFA mortars prepared with different GO contents (0.05 wt%, 0.1 wt%, and 0.2 wt%) have systematically examined. Electrochemical and mercury intrusive analysis revealed that the RFA mortars containing GO exhibited lower porosity and denser pore structure, compared to RFA mortars without any GO. The incorporated GO could further reduce ionic conductivity and thus improve the service life of RFA mortars. In addition, the interfacial transition zone (ITZ) between the RFA and cement paste was filled with hydration products when examined by scanning electron microscopy (SEM). Compared to those of RFA mortars without GO, the 28-day compressive and flexural strengths of RFA mortars with 0.2 wt% GO were increased by 19.2% and 47.5%, respectively. Finally, life cycle assessment (LCA) indicated that, compared to mortars with NA at the equivalent mechanical strengths, RFA mortars (containing 0.2 wt% GO) have better environmental performance (6.7% CO2 emission reduction or 2.2% primary energy demand saving). Overall, the addition of GO could significantly improve the quality of RFA mortars, which could further apparently improve the recycling of C&D waste, and then promote the sustainable development of construction sector. (C) 2018 Elsevier Ltd. All rights reserved.