Compaction

A Harvard miniature compaction device was used to determine the optimum moisture content (OMC) and maximum dry unit weight (MDW) of the ash samples. Samples were prepared at water contents ranging from 10-50% and compacted in three layers (25 tamps per layer). Water content measurements were taken from the middle of each sample after extrusion. To identify error associated with operator variability which has been discussed as a major flaw of using a Harvard miniature compaction device (Araújo Santos et al. 2019), multiple compaction tests were performed on a single sample of biomass fly ash as a proxy. Results indicated that the operator had consistent application of compaction force, as MDW values had a percent error of less than 1% compared to the average value. For wildfire ash samples prepared at water contents nearing the liquid limit, compaction by hand-tamping was necessary to prevent bearing capacity plunging failure.