Microstructure and Chloride Diffusion Properties of Hardened Fly Ash Cement Paste with Three-dimensional Graphene

In this paper, the influence of three-dimensional graphene (3DG) on the microstructure and chloride diffusion properties of fly ash cement paste was investigated. 3DG accounting for 0.0–0.2% of cement mass was evenly dispersed in hardened cement paste containing fly ash by using ultrasonic and polycarboxylate superplasticizer. The microstructure of the cement paste was characterized by mercury intrusion test (MIP), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results indicate that an appropriate amount of 3DG accelerates the secondary hydration of fly ash and provides a platform for the growth of cement hydration crystals. Moreover, the hydrated crystal fills the pores, reduces the harmful porosity, and refines the pore structure. The enhanced microstructure significantly improved mechanical properties and chloride diffusion resistance of hardened fly ash cement. With the addition of 0.1% 3DG, the compressive strength increased by 31.33%, and the chloride diffusion coefficient was reduced by 49.44%. The findings are beneficial to promote the generalized application of 3DG in cement in the marine environment.