Optimization and performance study of graphene oxide reinforced geopolymer

Geopolymer is an environmentally friendly material with fast setting time, high early strength, and low cost. It shows promise as a sustainable alternative to traditional cement-based grouting materials. This study proposed an alternative grouting material using a graphene oxide (GO) reinforced fly ash (FA) and ground granulated blast furnace slag (GGBS)-based geopolymer. This study employs the central composite design (CCD) method within response surface methodology (RSM) to design an optimal mix proportion for the geopolymer, considering the content of fly ash in the precursor, the content of graphene oxide, the alkali activator modulus, and the alkali content as influencing factors. The effects of these four factors and their interactions on the fluidity, initial/final setting time, and compressive strength at different curing ages of geopolymer are discussed. Microstructural analysis (XRD, SEM) is conducted to illustrate the mechanism underlying the strength enhancement of this grouting material. The results indicate that RSMCCD can accurately optimize the mix proportion of geopolymer. Considering both the strength development and workability of the slurry, the optimal proportion was determined to be 20 wt% fly ash content, 0.027 % graphene oxide content, an alkali content of 7, and a modulus of 1.2. Under these conditions, the 28day compressive strength can reach 80.41 MPa, which represents a 19.52 % increase compared to the group without GO. Under the influence of an activator with a moderate modulus and alkali equivalent, the synergistic effect of fly ash and graphene oxide (GOFA) can effectively improve the fluidity and setting time of the slurry, facilitating the formation of a well-structured, dense, and mechanically robust spatial structure in the geopolymer grouting material. The optimal proportion proposed in this study can serve as a basis and reference for the engineering application of geopolymer grouting materials.