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Concrete Deterioration of Prestressed Bridge Beams

Many prestressed concrete beam bridges in Michigan constructed in the 1970’s and 1980’s are showing mild to significant concrete deterioration due to Akali Aggregate Reactivity (AAR), including, but not limited to, Akali-Silica Reactivity (ASR), Akali-Carbonate Reactivity (ACR), and other material compatibility issues. Cracking and spalling deterioration tends to be more evident on fascia beams, and in some cases has required full superstructure replacements much earlier than anticipated, with ASR confirmed as a contributing factor. It is currently unknown how widespread this problem is in Michigan’s bridges, and if it extends to bridges built with prestressed beams constructed in the 1990’s and beyond. MDOT instituted specifications to test and mitigate for ASR in approximately 2012, but that leaves a significant portion of the bridge inventory whose susceptibility to AAR and durability may be unknown. Michigan Department of Transportation (MDOT) has recently tried several rehabilitation techniques but short and long-term durability of these approaches is relatively unknown.