Expansive Pressure Caused by Alkali Silica Reaction in Mortars under Restaint

Abstract

It is significant for deeper understanding of features of ASR damages of concrete structures to reveal relations between expansive pressure under restraint and free expansions of mortars in laboratory tests. One of the purposes of this study is to estimate the amount of ASR gel produced within mortars by the combination of EDS analysis for the gels and pore solution analysis. In addtion, this study aims at elucidating relations between expansive pressure measured under a restaint condition, and the amount and composition of gels. The expansive pressure was approximately proportional to the amount of ASR gel formed, when alkali contents of ASR gels formed were less than a critical value. However, mortars containing ASR gels with a higher alkali content than the critical value showed extremely low expansive pressure, even when they greatly expanded in expansion tests without restraint. These results suggest that, in existing ASR affected concrete structures containing gels with a higher alkali content than a critical value, damages due to the secondary stresses caused by resraint might not be so significant, even if reactive aggregate used in the concrete have shown great expansions in mortar bar test in the laboratory.