Mineralogical Study on the Consistency Property of Bentonite Mixed Soil

Bentonite mixed soil, which is a mixture of bentonite with sand and gravel, can be easily compacted by adjusting the blending degree, and it is difficult for water to pass through and exhibits low permeability. It is widely used at construction sites because it can be mixed on-site and has good workability. Examples of its use include impermeable layers at waste disposal sites and measures to contain heavy metals from rocks generated from construction sites. The main component of bentonite is smectite, which is a swelling clay mineral, and the swelling property and consistency characteristics determine the engineering properties. In particular, low permeability is considered to be strongly influenced by the electrochemical properties at the crystal level peculiar to smectite. In this study, the mechanism of expression of engineering properties of bentonite mixed soil was investigated focusing on the mineralogy properties of smectite. Specifically, X-ray and near-infrared analysis were performed to clarify the crystal structure of smectite and the adsorptivity of water molecules. The change in interlayer distance were clarified by XRD. Information on the behavior of water molecules was obtained by NIR. From these analyses, we obtained information on the swelling, consistency and micro-physical properties of smectite, which is the main component of bentonite, related to water permeability.