Sulfonation of graphene and its effects on tricalcium silicate hydration

Sulfonate graphene nanosheet (SGN), as a new chemical admixture obtained by sulfonation of graphene, has been used to investigate the effects on tricalcium silicate (C3S - Conventional cement chemistry notation is often used in this article to specify the composition of solid phase, whereby C = CaO, S = SiO2, F = Fe2O3 and H = H2O) hydration. Results show that SGN can prolong the dissolution period and induction period during C3S hydration owing to its adsorption behavior. In situ X-ray diffraction analysis demonstrated that the crystal growth on 001 planes of Calcium hydroxide (CH) will be enforced by addition of SGN, which is probably by the following steps: 1) Ca2+ released by C3S more likely diffused to the surface of SGN prior to nucleation of CH; 2) the nanosheets provide a template for aligned growth of the CH especially on the 001 planes. Meanwhile, scanning electron microscope photos directly show that the growth of CH is layer by layer on the 001 plane when SGN was added. Hopefully, the mechanism of C3S hydration cooperating with SGN proposed in this paper can make a guidance for the application of SGN in cement based materials. (C) 2019 Published by Elsevier Ltd.