Original Paper(Vol.61 No.1 pp.19-24)

Granulation Technique of Coal Ash and Cohesive Soil and Meterial Properties of Granulated Materials as Geo-Material

Norimasa YOSHIMOTO, Masayuki HYODO, Yukio NAKATA

Abstract:In recent years, the generation of coal ashes from many thermal power stations and various kinds of industries has been increasing. And also soft dredged soils annually disposed in marine area have become a serious geo-environmental problem of various countries. It is difficult to reuse as construction materials due to the fine grain size and flying dust, and the disposal sites of these materials have been decreasing. Therefore, it is very important to reuse these materials. Granulation technique is a method which converts coal ashes and soft cohesive soils into high-strength particles. This is one of the soil improvement methods to make efficient use of these materials. In this study, the granulation technique of these materials was examined. And the geo-material properties of granulated materials were investigated. (1) As making the granulated materials, they were sensitive to the addition volume of water and the best volume of water exists. The grain diameter became uniform by lengthening the granulation time and the uniformity coefficient became small. (2) The aspect ratio Ar of the granulated materials was lower and roundness coefficient Rc was higher than those of natural sands. In other words, the particles of granulated materials were closer to sphere than those of natural sands but their surfaces were rougher. It was clear that single particle crushing strength of granulated materials was lower than that of natural sands though it depends on being low the additive rate for cement. (3) Shear behaviour of granulated materials was similar one of sand with particle breakage. In each granulated material to which the coefficient of curvature is similar, it was also shown that the particle strength correlated well with the secant angle obtained from shear tests and it was possible to estimate the shear strength of granulated materials.

Key Words:Granulated materials, Coal ash, Cohesive soil, Geo-material, Granulation technique, Particle strength, Secant angle, Shear strength