Rheological evaluation of nano-metakaolin cement pastes based on the water film thickness

Abstract

The aim of this study was to evaluate the rheology of nano-metakaolin (NMK) cement pastes based on the water film thickness (WFT). The effects of the NMK content, water-to-binder (w/b) ratio, superplasticizer (SP), environmental temperature, and hydration time were considered in the rheological test. The fluidity, apparent viscosity, yield stress, plastic viscosity, packing density, and WFT of the investigated NMK cement pastes were determined. The flocculation structures (flocs) of the NMK cement pastes were examined. A mathematical model and a BP neural network model were established to predict rheological parameters. The results showed that the NMK increased the apparent viscosity, yield stress, and plastic viscosity of fresh cement pastes. NMK weakened the effects of environmental temperature and hydration time on the rheology of fresh cement pastes. The NMK addition increased the number of flocs in fresh cement pastes and yielded a lower packing density and WFT. A mathematical model and a BP neural network model based on WFT were available to accurately predict the rheological parameters.