Study on reduction of hexavalent chromium elution from cement-improved soil

Abstract

Hexavalent chromium may elute from a part of cement-improved soils when cement solidifications are used for the purpose of ground improvement. Particularly, the likelihood of elution increases when the type of soil is volcanic cohesive soil. Hexavalent cohesive chromium is extremely toxic to the human body. Therefore, in the above-mentioned cement solidifications, it is recommended to consider its elution when volcanic soil is used. In this study, strength and dissolution tests of hexavalent chromium are conducted on cement-improved soils in which cement solidifications and andosols are mixed. Three different waste materials (sugar syrup, burned fish bone, and rice husk ash) are used to verify their reduction properties for hexavalent chromium. According to the results of the test, the strengths of the specimens with the three different materials do not change significantly, and the improved soils maintain the required strengths. In addition, the elution amount of hexavalent chromium from the specimen mixed with a sugar syrup is lower than that from an unmixed specimen. This fact suggests that the waste syrup can reduce the elution of hexavalent chromium.