2018 Volume 67 Issue 1 Pages 67-70
The natural resources should be utilized effectively while circulating, and regarding targeted resources the acid sulfate soil often appearing among surplus soil and tsunami deposits is no exception. As acid sulfate soil usually contains the gypsum dihydrate which is the reaction products with sulfuric acid and carbonate mineral, ettringite crystal is produced by adding hydrated lime, and the coagulation hardening of the soil is promoted. In this study, we have investigated a relation with the strength increase and ettringite production on acid sulfate soil treated using only hydrated lime and the stabilizers which include an iron oxide in raw materials through the unconfined compression test, X-ray diffraction analysis and differential thermal analysis. The iron oxide is a residue deriving from the rare earth magnet grinding waste. We have mixed unslaked lime, calcium carbonate, granulated blast-furnace slag fine powder and anhydrous gypsum fine powder into the wet or dry iron oxide under a certain proportion and have called such stabilizers the iron oxide-lime based materials. Additive contents of hydrated lime and iron oxide-lime based materials were 6 to 10 percent for dry mass of acid sulfate soil. The specimens were cured in an incubator regulated to a temperature of 20 degrees Celsius for up to 360 days. From a result of the unconfined compression test and thermogravimetry, it was ascertained that not only the strength increase but also the ettringite production rose with additive contents provided the strength increase was more than 0.5MN/m2.
