Study of Dispersion, Hydration, and Microstructure of Graphene Nanoplates-Modified Sulfoaluminate Cement Paste

Low-carbon ecological cement composites are among the most promising construction materials. With low energy consumption, low carbon dioxide emissions, and high early strength, sulfoaluminate cement (SAC) is a low-carbon ecological building material. In addition, graphene nanoplates (GNPs) exhibit excellent performances. In this study, GNPs were dispersed by a combination of dispersant and ultrasonic treatment, and the dispersion effect of GNPs was characterized. The effect of GNPs on the hydration process and products of SAC was studied, revealing that GNPs accelerate SAC hydration. The hydration heat and ICP results showed that in the SAC hydrolysis stage, C(4)A(3)Š (ye’elimite) hydrolyzed and released Ca(2+). GNPs absorbed the Ca(2+), and the Ca(2+) concentration around C(4)A(3)Š decreased, which would promote the hydrolysis of C(4)A(3)Š and release more Ca(2+), accelerating the hydration of SAC and the nucleation effect of GNPs, and providing sites for the formation of hydration products. The analysis of XRD (X-Ray Diffraction) and TGA (Thermal Gravity Analysis) showed that GNPs promoted the hydration of SAC and formed more AFt (ettringite) and AH(3) (gibbsite). The generated hydration products fill the pores of the matrix and are closely connected to the GNPs to form a whole, which improves the cement matrix’s mechanical properties.