Evaluation of shear strength and mechanical properties of granulated coal ash based on single particle strength

Abstract

The authors have been studying the mechanical properties of granulated coal ash formed by the milling process with a small amount of cement added, with particles almost equivalent in size to sand or fine gravel. The use of granulated coal ash has many advantages, such as the suppression of leaching of heavy metals and the possibility of outdoor curing. In addition, since granulated coal ash is produced artificially, their particle strength can be understood easily. Another advantage is that it is possible to control the particle strength, something which cannot be performed in natural sands. The present research was carried out in order to investigate the possibility of putting such advantages to good use.Single particle crushing tests were carried out on various kinds of granulated coal ash to evaluate the crushing characteristics of each individual grain. Also, the characteristics of the individual particle, such as shape, were investigated. Next, one-dimensional compression tests were conducted to investigate their compression characteristics. Finally, drained monotonic triaxial compression tests were performed under different confining pressures. The effects of the confining pressure on the shear characteristics, as well as their relation to shear strength, were examined with the single particle crushing strength taken into account.Contrary to observations in natural sands, the single particle crushing strength of granulated coal ash did not depend on particle size. Regarding compression characteristics, granulated coal ash compressed very easily because the crushing strength of a single particle was low. Therefore, the yield stress of granulated coal ash was found to be smaller than that of natural sands. Moreover, the crushing strength affected the shear characteristics, i.e., as the crushing strength increased, the shear stiffness became higher and the compressive volumetric strain became smaller. Therefore, crushing strength can be a useful parameter in evaluating the shear characteristic of granulated coal ash.