Microstructure and Composition of Red Mud-Fly Ash-Based Geopolymers Incorporating Carbide Slag

Abstract

In order to find the possibility of recycling an industry waste solid red mud from earth, a kind of geopolymer material system based on red mud-fly ash-carbide slag has been developed entirely from waste. The microstructure and composition of the geopolymer material system at the age of 28 days was tested by the scanning electron microscope (SEM), back scattered electron (BSE), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric-differential scanning calorimetry (DSC-TG). It was showed that the compressive strength of the geopolymer sample was 15.1 MPa when the liquid solid ratio (L/S) was 0.7, sand-binder ratio was 3:1, alkaline activator used wet-based carbide slag, and the fly ash, red mud and carbide slag were prepared as the proportion of 4:3:3. Through scanning electron microscope, back scattered electron, energy dispersive spectroscopy, X-ray diffraction, and thermogravimetric-differential scanning calorimetry results, the spherical beads in fly ash were dissolved in the alkaline environment to form silicon and aluminum monomers and polymerized to synthesize C-S-H and C-A-S-H gels. Wet-based carbide slag played the role of calcium component support in C-A-S-H, C-S-H gels and alkaline activator.