2021 Volume 75 Issue 1 Pages 356-363
Waste gypsum board is treated as managed industrial waste, and its use due to recycling is low, so there is an urgent need to consider new effective use destinations from the viewpoint of future disposal site limits and treatment costs.
In this study, from the viewpoint of processing cost, we focused on the recycled dihydrate gypsum powder obtained by crushing and separating waste gypsum board. Focusing on the expansion promoting action of regenerated gypsum powder, the possibility of effective use as a filler by mixing with air mortar was examined. From experiments, it was clarified that the air mortar mixed with dihydrate regenerated gypsum powder satisfies the set target values in terms of the general required performances of lightness, fluidity, and strength characteristics. The air mortar mixed with dihydrate regenerated gypsum powder satisfies a wet density of 0.5 to 1.3g/cm3, a flow value of 180±20mm, and a compression strength of 1.0N/mm2 or more. A mixture of recycled dihydrate gypsum powder can carry more air than the base. Furthermore, as a material for studying new effective use destinations, the relationship between the amount of air contained and the compressive strength was quantified. The air mortar mixed with the recycled dihydrate gypsum powder exhibits the same strength as the base having the same amount of air when the content of air increases to about 50％.
