Iowa Department of Transportation
Brent Pharesbphares@iastate.edu email >
Bridge Research Engineer, BEC
About the research
Since the 1970s, the Iowa Department of Transportation (DOT) has used concrete overlays as a means of restoring its bridge decks and, as a result, the service life of the deck is commonly extended many years. This procedure has proven to be both effective and economically attractive.
Despite that, concrete overlays cannot be considered a permanent repair as they are subjected to harsh conditions, similar to the original bridge decks. As time passes, the overlays often become delaminated from the original deck at or near the bond interface, leading to cracking and the intrusion of water and chloride ions, which accelerate the deterioration. A preservation solution involving the injection of epoxy resin into the cracks and voids has been developed and this solution has been implemented with success across Iowa. Even so, the length of additional service life and the most effective methods and materials of injection remain unknown.
The problem is two-fold. First, a better prediction of typical expected service life must be determined to best plan for additional repair or replacement. This requires a study of both previously and newly injected bridges to identify the effectiveness and durability of epoxy injection of delaminated bridge decks. Second, the seasonal constraints imposed on the injection process, coupled with the work load of Iowa DOT maintenance personnel, create a logistical problem; quite simply, there is more work to be completed than can be effectively accomplished in the available time.
A specification detailing the proper materials, equipment, and procedures was developed to enable others to perform the work. Both a field investigation and a thorough review of industry advances and practices were used to develop the specification.