Mitigation Techniques for Structures with Premature Concrete Deterioration due to ASR/DEF

摘要

From 1998 to 2003, a comprehensive investigation was conducted in Texas on the structural performance of in-service bridges with premature concrete deterioration. The premature concrete deterioration is attributed to two expansive distress mechanisms: alkali-silica reaction (ASR) and delayed ettringite formation (DEF). While chemically different, both mechanisms require moisture. The service life of deteriorated structures can be extended by suitable mitigation techniques. This study addresses the comparative effectiveness of surface treatments. It was found that existing ASTM tests for ASR and DEF were not useful for this purpose. A new test method, involving cycles of controlled wetting and drying, was found to be useful; and this method was used to compare the effectiveness of proposed surface mitigation treatments. Based on that comparison, a surface mitigation treatment consisting of silane followed by an appearance coat of breathable paint is recommended to extend the service life of structures with premature concrete deterioration due to ASR/DEF.