PREMATURE CONCRETE DETERIORATION DUE TO ASR/DEF IN TEXAS

In Texas, there are over 49,000 concrete bridges and over 13,000 lane miles of concrete pavement. Overall, these concrete structures and pavements have provided excellent long-term performance, usually exceeding their expected performance. However, there have been instances where the performance of these structures and pavements has been severely compromised due to premature concrete deterioration (PCD) resulting from alkali-silica reaction (ASR) and/or delayed ettringite formation (DEF). Whenever premature deterioration of concrete structures and pavements takes place, the Texas Department of Transportation (TxDOT) conducts forensic investigations to identify the cause(s) and determine proper repair methods and future remedial measures. These may include the modification of specifications, design standards, and construction guidelines. This paper summarizes the findings of recent forensic investigations of premature concrete deteriorations in structures and pavements conducted by TxDOT. The overall findings include (1) ASR causes premature deterioration of concrete in pavements and structures, (2) DEF could cause PCD in not only pre-cast concrete members, but also in cast-in-place concrete, and (3) in prematurely deteriorated concrete, even though both alkali silica gel and evidence of sulfate attack due to DEF usually coexist, ASR was the cause for the initial deterioration with subsequent ettringite formation.