Nano-mechanism of graphene oxide reinforced fly ash-slag based geopolymer materials to form high polymerization degree C-(A)-S-H: A new view of physical-chemical synergistic effect

This study mainly investigated the effect and mechanism of graphene oxide (GO) on the nucleation of C-(A)-S-H in fly ash-slag based geopolymer. A variety of material characterization methods and electronic structure analysis methods were combined to analyze the nanostructure changes and electronic transitions generated during the reduction of GO in an alkaline environment. Based on this change, the effect of GO/RCO on the binding and mode of calcium ions was explored, which provided a basis for revealing the nucleation and development of C-(A)-S-H. The results show that, GO is reduced in an alkali-excited environment, resulting in nanostructure changes and the formation of a strong electron cloud/field at its edge, thereby changing its binding mode to calcium ions (from chemical binding to physical electrostatic adsorption). This physical-chemical change makes the edge of GO form a calcium ion enrichment environment, which provides sites and prerequisites for inducing and driving the nucleation and growth of C-(A)-S-H. However, excessive GO will lead to the metastable state and multi-aluminum phase structure of C-(A)-S-H, which is not conducive to the development of comprehensive properties such as mechanics of geopolymers.