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 compressive strength of Bayer red mud-based geopolymer engineered cementitious composites increased when the modulus of the activator lower than 1.5 M, and then decreased, and the compressive strength decreases with the increase of red mud dosage. When the modulus of the activator is 1.5 M and the content of red mud is 50%, the compressive strength of the 3d reached 11.24 MPa. The variation curves of T2 relaxation time and viscosity with hydration time can be obtained that the geopolymerisation process of Bayer red mud-based geopolymer engineered cementitious composites is divided into three stages. When the modulus of activator is 1.5 M, the effect of promoting geopolymerisation reaction is most obvious. From the geopolymerization kinetics model, it can be seen that the reaction rate constants are always K1 > K2 > K3 with changes in the modulus of the activator and the red mud dosage, indicating that NG product crystallization nucleation and growth process is dominant in the geopolymerization process. The change curve of dα/dt shows that when the modulus of the activator is 1.5 M, the excitation effect is best. 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.