Study on leaching of hexavalent chromium from hardened concretes using tank leaching test

Abstract

Tank leaching tests were carried out to investigate the behavior of leaching trace elements from monolith samples. This study consists of two series, and the trace element used was hexavalent chromium. In Series I, the influence of the leachant/surface area of the specimen (L/S ratio) on the leaching amount was investigated. The leaching amount was found to increase with the amount of worked water. This shows that any L/S ratio can be selected in the tank leaching test. In Series II, the influence of the curing conditions of concrete on the leaching amount was investigated. In the case of concrete cured under sealed conditions, hexavalent chromium hardly leached. On the other hand, in the case of concrete dried in the room, the amount of leaching of hexavalent chromium became large. Carbonation was found to cause the decomposition of cement hydrates and the release of fixed hexavalent chromium. The leaching of hexavalent chromium from using concrete was evaluated from these results. When water works continuously against concrete, the leaching of hexavalent chromium hardly affects the environment for water. When rainwater flows on the drying surface of concrete, the amount of leaching at the first rainfall was comparatively large, but deceased with subsequent rainfall. Copyright © 2007 Japan Concrete Institute.