ASR PROBLEMS IN JAPAN AND A MESSAGE FOR ASR PROBLEMS IN THAILAND

Abstract

Alkali silica reaction, ASR is still a durability problem in Japan although
countermeasures have been established since 1986. The problems of this
Japanese situation are thought to be caused by lack of verification of the
effectiveness of the adopted countermeasures. In this critical review, the
background of the Japanese countermeasures against ASR and a new
approach that Japan has to introduce are explained. It will be informative for
many countries to prepare ASR countermeasures. As an example of new
methodology, a case of ASR damage in Thailand was analyzed from the
viewpoint of petrography using concrete thin section. The ASR found in a
footing was caused by cryptocrystalline quartz in granite mylonite, which is
typical mineral for late expansion. Although ettringite formation was
accompanied, the major mechanism of expansion is considered as ASR
judging from the texture of expansive phase produced in aggregate and
cement paste. Another important highly reactive phase was identified during
this analysis. Mica in granite can be altered to highly reactive opal in hot
and humid climate, which is a typical mineral for rapid expansion showing
compositional pessimum effect. This alteration product can be common all
over Southeast Asia and considered as a possible serious cause of ASR
damages.