An Investigation into the Compaction of Sandstone Aggregates Stabilised with Cement and Fly Ash

This paper experimentally investigated the compaction properties of sandstone aggregate stabilised with a mixture of Portland composite cement and Class F fly ash. It determined the influence of fly ash content on the maximum dry density, optimum moisture content and air void content of the stabilised sandstone using the 2.5 kg rammer compaction method. Fly ash contents of 0, 10, 20, 30 and 40% by mass of aggregate were added to sandstone aggregate samples with a constant cement content of 5% by mass of aggregate. The investigation showed that the maximum dry density peaked at 5% cement without fly ash, while the optimum moisture content was the lowest among all investigated fly ash contents. It also showed that for every increment of 10% fly ash with a constant 5% cement content, the maximum dry density decreased linearly, and the optimum moisture content increased exponentially. From 10 to 30% fly ash content, the air void content increased and subsequently decreased from 30 to 40% fly ash content. The investigation concluded that fly ash is an effective stabiliser when cement-to-fly ash ratios are between 1:2 and 1:4 and should not exceed 1:6.