Compaction behaviour of fly ashes

Abstract

Fly ashes are used widely in many geotechnical applications. In most of the applications, compaction of the fly ashes is essential to improve their engineering behaviour. This paper presents the compaction behaviour of fly ashes along with the mechanisms controlling their behaviour. To this end, their compaction curves have to be presented on recently proposed volume-based parameters, namely solid volume occupation and water volume content, instead of weight-based parameters such as dry density and water content. For a given fly ash the variation in solid volume occupation with water volume content for any given compactive effort has been explained as being due to variation in the pore water pressure. Fly ashes resist the external compactive effort by shear resistance and positive pore water pressure development. The strength of fly ashes at any point on the dry side of optimum is the same, and on the wet side of optimum decreases with water volume content. The variation between the compaction curves of different fly ashes is essentially due to their differences in fineness and frictional characteristics.