Rapid Evaluation of the Pozzolanic Activity of Bayer Red Mud by a Polymerization Degree Method: Correlations with Alkali Dissolution of (Si+Al) and Strength

Abstract

A large amount of Bayer process red mud is discharged in the process of alumina production, which has caused significant pollution in the environment. The pozzolanic activity of Bayer red mud as a supplementary cementitious material is a research hotspot. In this work, a new method for Fourier-transform infrared spectrometry is used to determine the polymerization degree of Bayer red mud in order to evaluate its pozzolanic activity. Based on the results of the dissolution concentration of (Si+Al), strength index and polymerization degree of Bayer red mud, the relationships between different evaluation methods were analyzed, and the relevant calculation formulas of pozzolanic activity were obtained. The results showed that different evaluation methods can reflect the variation law of pozzolanic activity in Bayer red mud. The polymerization degree of Bayer red mud had a good linear relationship with the pozzolanic activity index obtained by the strength index and dissolution concentration of (Si+Al), respectively. The polymerization degree was negatively correlated with pozzolanic activity index and dissolution concentration of (Si+Al), and the correlation coefficients were greater than 0.85. Therefore, this method was found to be effective and hence can be used as a rapid and simple test for pozzolanic activity evaluation of Bayer red mud.

Investigation of the Pozzolanic Activity Improvement of Yellow Phosphorus Slag with Thermal Activation

“…The polymerization degree method used Origin software to fit and calculate the peak area of Si(Al)Q n at 800-1200 cm −1 of the FTIR spectra. Then, the polymerization degree of [SiO 4 ] was evaluated using the concept of the relative bridging oxygen bond (RBO) according to Equation (2) [35]:…”

“…The high degree of polymerization indicates that silicon and aluminum are relatively stable. The lower degree of polymerization demonstrates that the Si-O-Si(Al) in YPS ash is broken, and the active silicon and active aluminum in YPS ash are increased [35]. The RBO of the YPS100 is the smallest, with a value of 0.3757.…”

“…The peaks of 800-1200 cm −1 correspond to the asymmetric tensile vibrations of Si-O-(Si, Al) linked to the tetrahedral of [SiO 4 ] or [AlO 4 ] − [32]. The peaks at 600-800 cm −1 are the symmetric stretching vibrations of Si-O-Al or Si-O-Si in the tetrahedra of [SiO 4 ] or [AlO 4 ] − [35]. The peaks in the 400-600 cm −1 range are the bending vibrations of Si-O-Si(Al) [29,35].…”

“…The peaks at 600-800 cm −1 are the symmetric stretching vibrations of Si-O-Al or Si-O-Si in the tetrahedra of [SiO 4 ] or [AlO 4 ] − [35]. The peaks in the 400-600 cm −1 range are the bending vibrations of Si-O-Si(Al) [29,35]. The positions and areas of the peaks of 800-1200 cm −1 vary with temperature, indicating that the bonds between Si, Al and O in YPS ash are combined or broken.…”