Effect of cut-size particles on the pozzolanic property of bottom ash

Abstract

Currently, most bottom ash (BA) from the Mae Moh power generating plant is being dumped in landfills rather than being utilized in the concrete industry, in contrast to fly ash, which has been technically proven viable and beneficial and widely used as a pozzolanic material. In some cases, BA is recommended as a partial substitute for sand, while the pozzolanic function of BA or a cement replacement is rarely considered. Therefore, the objective of this study was to investigate the effect of cut-size particles on the effective utilization of BA as a cementitious material to enhance the pozzolanic reaction. BA particles that were received directly from a power plant were prepared via separation through sieves of various sizes and ground until 95 ± 1 wt.% of the particles passed through a No. 325 sieve. River sand was ground to the same fineness for evaluating the pozzolanic reaction of the ground BA in terms of the strength activity index (SAI). The results demonstrated that all samples of ground BA had pozzolanic properties and that the compressive strength of the ground BA mortar increased with curing age. Ground BA that was produced from smaller particles resulted in a higher SAI than the samples that were prepared from larger particles. The findings of this study supported the suitability of SAI as a tool for determining a pozzolanic reaction. Moreover, by sieving to smaller sizes before grinding, the ground BA resulted in different percentages of insoluble waste as well as in different amorphous contents. The coarser particles of ground BA had higher insoluble waste and lower amorphous content than the finer particles. A lower compressive strength was obtained in case of coarser particles.