Study on the Hardening Mechanism of Bayer Red Mud-Based Geopolymer Engineered Cementitious Composites

Abstract

The Bayer red mud-based geopolymer is an economical and environment-friendly substitute for cement because of its superior performance. In this paper, low field nuclear magnetic resonance, rheometer, isothermal calorimeter and other means were used to explore the geopolymerisation mechanism of Bayer red mud-based geopolymer engineered cementitious composites, and establish the geopolymerisation kinetics model under different preparation parameters. The results showed that the geopolymerisation process of Bayer red mud-based geopolymer engineered cementitious composites can be divided into reorganization period, acceleration period and degenerating period according to low-field NMR, and can be divided into induction period, stability period and acceleration period with respect to time-dependent viscosity. When the Bayer red mud dosage is less than 50%, the inhibition effect on the delay of reaction rate is slight. When the activator modulus is 1.5M, the effect of reaction promotion is the most obvious. It can be seen from the geopolymerisation kinetics model that when the activator modulus is lower than 1.5 M, the NG product crystallization nucleation and growth process is dominant. When the activator modulus is higher than 1.5 M, the phase I boundary reaction is dominant. The research results promoted the application of Bayer red mud-based geopolymer engineered cementitious composites, and improved the resource utilization efficiency of red mud and other solid wastes.

Keywords: Bayer red mud, geopolymer cementitious material, low-field nuclear magnetic resonance, Rheology, geopolymerisation kinetics