The Texas Department of Transportation (TxDOT) has approximately 50,000 bridges in its inventory andthe deterioration of concrete under these bridge structures, most of which are reinforced, has been a criticalissue affecting the service condition of these bridges. Recent research on deteriorated concrete pillars onbridges in Texas indicated that microbial colonization might be a factor promoting the surface deteriorationof bridge pillars continuously exposed to water. Although microbial induced deterioration (MID) on sewersystems, agricultural construction, and concrete cooling towers has been extensively documented, littleresearch has been performed on damage from MID on bridge structures. In this study, a visual inspectionand a number of in situ and laboratory tests were performed on pillars of twelve TxDOT bridges withsuspected MID issues. In situ tests included rebound hammer, ultrasonic pulse velocity, covering thickness,half-cell corrosion potential and phenolphthalein pH analyses were performed. Water, mud, core andsurface concrete samples of pillars were also collected for laboratory analysis of microbial and chemicalcomposition, mineralogy and petrographic analysis to investigate the potential cause and extent of thedeterioration. Results from this comprehensive study were used to provide evidence of concretedegradation and ascertain the degree of deterioration caused by microbial attack.
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