Evaluation of Premature Deterioration of Concrete Bridge Barriers by Petrographic Examination

Many of the current-generation concrete bridge barriers used in Michigan have deteriorated at a rate greater than expected. For an assessment of the possible causes of this premature distress with the objective of alleviating future occurrences, sixteen core specimens from eight sites constructed between 1983 and 2001 were evaluated. The evaluation included visual inspection, stereo and petrographic optical microscopy, and scanning electron microscopy. The major observations revealed through this analysis were that poor consolidation, marginal air-void systems, alkali-silica reaction associated with chert and siltstone in the fine aggregate, corrosion of reinforcing steel, and possibly frost susceptibility of fine siltstone aggregates were responsible for the deterioration. These results provide the basis for improving the quality of such barriers in future construction.