The significance of dispersion of nano-SiO2 on early age hydration of cement pastes

Abstract

Nano-materials have various promising properties to concrete material. However, the poor dispersion of nano-materials remains to be a big challenge which impairs the target performances and thus increases the economic cost. In this study, we focused on one of the most widely used nano-materials, nano-SiO2 and investigated the influence of its dispersion on the early age hydration of cement pastes. A recently developed method was applied to chemically graft polycarboxylate superplasticizer onto nano-SiO2 particles to produce well dispersed particles with the shell core structure (nano-SiO2@PCE). Dispersity of nano-SiO2@PCE in deionized water (DI water) and in simulated pore solution of cement pastes was carefully characterized by Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectrometer (FTIR) techniques. The effects of nano-SiO2 dispersion on the early age hydration of cement pastes were investigated. The results showed that with good dispersion only 0.5% by mass of nano-SiO2 can significantly accelerate hydration. The retarding effect unintentionally caused by PCE was observed to influence particularly on the length of induction period rather than other stages of hydration. BNG model was used in the end to quantitatively analyze and shed more lights on the influence of nano-SiO2 on the kinetics of C3S hydration.