Study on the Setting and Hardening Process of red mud-coal metakaolin geopolymer concrete by Electrochemical Impedance Spectroscopy

Abstract

The setting and hardening of red mud-coal metakaolin geopolymer concrete (RCGC) was studied. To this end, four sets of RCGC blocks with different water-binder ratios (0.50, 0.55, 0.60, and 0.65) were prepared. The workability, setting time, and compressive strength of four RCGC specimens with different water-binder ratios were evaluated. The electrochemical performance of RCGC was analyzed by electrochemical impedance spectroscopy (EIS), and the process of coagulation and hardening was analyzed through equivalent circuit parameters. X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and scanning electron microscopy-energy dispersive analysis (SEM-EDS) were used to investigate the coagulation and hardening mechanism of RCGC materials. The experimental results show that the increase of the water-binder ratio prolonged the setting time of RCGC and increased the slump. There is a good linear relationship between the compressive strength and the impedance parameters Rs and Rct. Over time, the pores of the material are gradually filled with coagulation and hardening products, and the microstructure is gradually developed