Effect of bottom ash particle size on strength development in composite geomaterial

This study investigated how the particle size of bottom ash affects the frictional resistance and pozzolanic reaction of bottom ash-added composite geomaterial. A composite geomaterial (CGM) consists of dredged soil, bottom ash, and cement. The frictional resistance and pozzolanic reaction were evaluated using bottom ash-added mixtures with three different particle sizes: the original bottom ash and two generated bottom ashes. These three bottom ashes had almost identical chemical components and differed only in particle size. Three kinds of mixtures were prepared with various bottom ash contents ranging from 0 to 100% by the weight of dry dredged soil. Several series of laboratory tests including unconfined compression tests, SEM analyses, and physical tests, were carried out on the mixtures at various curing times ranging from 7 to 120 days. The results indicated that the unconfined compressive strength of CGM increased with an increase in bottom ash content and curing time due to the frictional resistance and pozzolanic reaction, which were induced by adding bottom ash to the mixture. During the early stages of curing time (less than 28 days), the strength development was mainly governed by the hydration reaction and frictional resistance. However, for curing times greater than 28 days, the pozzolanic reaction contributed to the strength development as a function of curing time. Experimental results indicated that smaller particles of bottom ash produced more strength development with increasing curing time from the pozzolanic reaction than larger particles of bottom ash.