How Oregon DOT Sold Contractors on Internally Curing Bridge Decks

Internal curing concrete offers several advantages for bridge deck construction, with the primary benefit being its ability to resist shrinkage cracking. However, convincing contractors of these benefits can be challenging, as the Oregon Department of Transportation (ODOT) discovered.

In an effort to make the concept more understandable and easier to implement, ODOT initiated steps to promote internal curing. The department began testing internal curing in 2017 to combat premature shrinkage cracking by introducing moisture within the concrete. By 2023, ODOT had completed 15 projects using this method. Despite its potential, contractors were hesitant to embrace the new process due to the perceived risks associated with using a different material.

Internal curing is an improved alternative to conventional curing, where water is typically applied only to the concrete’s surface. The primary objective is to extend the lifespan of bridge decks by 25-50 years, making them less susceptible to shrinkage cracks that can compromise the structure’s integrity.

The Federal Highway Administration explains that internal curing commonly involves replacing some normal-weight fine aggregate with pre-wetted lightweight aggregates with high absorption capacity. This ensures that curing water is distributed throughout the concrete body, rehydrating it as it naturally dries out.

While initially met with resistance, internal curing is gaining traction among various state Departments of Transportation, including those in New York, Indiana, Louisiana, North Carolina, Ohio, and Utah.

To address contractors’ concerns and demonstrate the benefits of internal curing, ODOT made several adjustments to its program. These included simplifying specifications, predetermining the amount of lightweight fine aggregate needed, and providing educational resources and approved product sources to contractors.

By conducting a cost-benefit analysis and sharing data showing a 70% reduction in crack density on internally cured bridge decks, ODOT was able to show that the new process was cost-effective in the long run. The department has since made internal curing its standard concrete for bridge decks and is exploring its application in paving and overlays.