Effect of ultra-low dosage graphene oxide on the properties of recycled cement-based materials

Abstract

The utilization of recycled fine powder (RFP) from crushed concrete waste as partial cement replacement is limited by its low reactivity. Graphene Oxide (GO) is a two-dimensional amphiphilic conjugated polymer that can effectively improve the properties of cement-based materials, but its application is limited due to its high cost. This study investigates the ultra-low dosage GO on the properties of recycled cement-based materials. GO was dispersed using polycarboxylate superplasticizers (PCE) before incorporation in the pastes containing 25 % RFP as the binder. The results show that PCE can effectively improve the dispersion of GO in cement-based materials. The improvement effect of well-dispersed ultra-low dosage GO on the strength of recycled cement-based materials in the early stage was better than that in the later stage, and the improvement effect on the flexural strength was better than that on the compressive strength. The GO dosage was optimized at 0.004 % which improved the 3 days flexural strength by 52 % compared to the control sample without GO. Results showed that well-dispersed ultra-low dosage GO accelerated the hydration of recycled cement-based materials due to the nucleation effect and template effect, promoted the formation of additional C–S–H gels, and facilitated the development of C–S–H gels more orderly, reduced the porosity of the hardened pastes, and refined the microstructure. However, excessive GO reduced strength due to agglomeration. The improvement in strength and microstructure refinement demonstrates the positive role of GO in enhancing the reactivity of recycled cement-based materials. This process successfully reduced the dosage of GO in cement-based materials by about 90 % and provided an approach to utilizing recycled fine powder.