Inspection of Texas Concrete Bridge Pillars with Suspected Microbial-Induced Deterioration

The Texas Department of Transportation (TxDOT) has approximately 50,000 bridges in its inventory and the deterioration of concrete under these bridge structures, most of which are reinforced, has been a critical issue affecting the service condition of these bridges. Recent research on deteriorated concrete pillars on bridges in Texas indicated that microbial colonization might be a factor promoting the surface deterioration of bridge pillars continuously exposed to water. Although microbial induced deterioration (MID) on sewer systems, agricultural construction, and concrete cooling towers has been extensively documented, little research has been performed on damage from MID on bridge structures. In this study, a visual inspection and a number of in situ and laboratory tests were performed on pillars of twelve TxDOT bridges with suspected 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 and surface concrete samples of pillars were also collected for laboratory analysis of microbial and chemical composition, mineralogy and petrographic analysis to investigate the potential cause and extant of the deterioration. Results from this comprehensive study were used to provide evidence of concrete degradation and ascertain the degree of deterioration caused by microbial attack.