2025 Volume 32 Issue Supplement Pages S87-S93
This study investigates the reuse of recycled concrete powder —obtained via the heating and rubbing method—by adding to cement mortar as a substitute for JIS standard sand. When different proportions of recycled concrete powder (10%, 30%, and 40%) were added to ordinary Portland cement mortar, a reduction in compressive strength of up to approximately 10% was observed in relation to mortar without the recycled concrete powder. Conversely, when the same proportions of recycled concrete powder were added to cement equivalent to Class B blast furnace cement —i.e., a 60:40 mixture of ordinary Portland cement and ground granulated blast-furnace slag powder, an increase in compressive strength was observed as the addition rate increased, with a maximum increase of approximately 5%. This increase is believed to result from the activation of the recycled concrete powder by the ground granulated blast-furnace slag powder. In a sulfuric-acid resistance test, mortar with recycled concrete powder added to the Class B blast furnace cement-equivalent cement showed equal or better resistance in a 5%mass sulfuric acid solution compared to mortar without recycled concrete powder.
