A Study on Microstructure Composition of Unsaturated Red Mud and its Impact on Hydraulic Characteristics

Micro-test approaches like XRF, XRD and SEM and routine soil tests were applied to analyze the chemical composition, mineral composition, microstructure and basic physical property indicators of three kinds of red mud, which were the Bayer red mud, sintering red mud as well as the mixed red mud prepared by sintering red mud and the Bayer red mud at the mixture ratio of 1:1. On this basis, in the dehumidification-moisture absorption process, the relationship among matric suction, hydraulic conductivity and moisture content of the three types of red mud was studied by transient hydraulic characteristic cyclic test of unsaturated mud. The results indicated: physicochemical properties of the three kinds of red mud, such as mineral composition, microstructure and size grading varied remarkably; on the condition of the same moisture content, SWCC and HCFC of the three kinds of red mud demonstrated obvious hysteresis effect, which is the most significant on the Bayer mud, less on the sintering red mud and the least on the mixed mud; the Bayer red mud possess smaller hydraulic conductivity, worse drainage and stability.