The Federal Highway Administration’s Western Federal Lands Highway Division and Glacier National Park partnered on a project to replace the Upper McDonald Creek Bridge in Glacier National Park, near Kalispell, MT, with a double-lane, clear-span bridge utilizing Internal Curing technology (ASTM C1761). Internal curing dramatically reduces the cracking in concrete which leads to increased service life of these bridges and pavements.
The process involves substituting pre-wet fine expanded shale, clay, and slate (ESCS) lightweight aggregate for about 400 lbs. of sand in the concrete mix. This technology is now used in bridges across the country, including in Indiana, New York, Ohio, Oregon, Texas, and other states.
According to Schellinger Construction Company (ready mix supplier for the McDonald Creek Bridge), the internally cured concrete mix performed outstandingly despite logistical challenges and the remoteness of the bridge (located approximately 2.5 hours away from the batch plant). According to the FHWA inspector, “The concrete deck placements went very well. No cold joints and the mix looked good!” The new McDonald Creek Bridge will provide access to the northwest shore of Lake McDonald, including access to private homes, the Lake McDonald Ranger Station, and trailheads. The new bridge (completed in the Fall of 2024) is approximately 30 feet upstream of the existing bridge, requiring a realignment of the road approaches.
There are many opportunities to improve concrete projects by using internal curing. In the case of bridges, Anthony E. Fiorato, past president of ACI, said, “Durability is a driving force on the choice of material in bridge construction.” Concrete in the 21st century is being improved through the choice of ingredients, engineered systems, and practices, rather than relying on methods that are effective by on-the-job practices and weather. Instead of external curing with water after the fact, water will be engineered into the concrete using water-absorbent materials like ESCS fine lightweight aggregates. For more information, please contact www.escsi.org
