Pennsylvania DOT (PennDOT) oversees the nation’s third-largest inventory of state-owned bridges: 25,400. Average age is 50 years; typical life span, 75 years. The state also has the nation’s second-highest number of bridges rated “poor” in the Federal Highway Administration’s (FHWA) National Bridge Inventory (NBI).
The $7 billion that’s budgeted every year to maintain roads and bridges is $8 billion less than necessary to fully restore the state’s transportation network, which is the size of New Jersey, New York, and the New England states combined. To invest the driving public’s tax dollars as wisely as possible, PennDOT seeks repair materials that are durable and easy to install.
One such material is Rapid Set® Concrete Mix. The structural repair material is a blend of belitic calcium sulfoaluminate (BCSA) cement and aggregate that reaches 3000 psi (20.7 MPa) compressive strength in an hour, enabling DOTs to minimize inconvenience to the driving public by quickly reopening roads and bridges to traffic. The material’s chemistry is inherently more resistant than portland cement concrete to alkali-silica reaction (ASR), sulfate attack, shrinkage cracking, and freeze-thaw cycles. This minimizes deterioration that will require future maintenance.
For these reasons, Rapid Set Concrete Mix has been on PennDOT’s qualified products list (QPL) for at least two decades. In 2021, HRI Inc. of State College, Pa., used the material to conduct partial deck replacement on four bridges on Route 309 near the cities of Wilkes-Barre and Pittston.
Rapid Set Concrete Mix is mixed, placed, and finished similarly to portland cement-based concrete repair material. Every second a crew can save between mixing and placing Rapid Set Concrete Mix increases efficiency. As a long-time PennDOT contracting partner, HRI has developed a process for maximizing the material’s 15-minute working time.
Every night, HRI puts three 3,000-pound supersacks in a gravity bin mounted on a flatbed truck equipped with a vibrator pack and a water tank. At the jobsite, the vibrator pack ensures the mix flows smoothly and continuously from the gravity bin into a skid steer loader-mounted mobile mixer while a hose attached to the water tank feeds the mixer. Crew members don’t waste time and risk injury climbing onto equipment to keep production moving, so they’re ready and waiting to spread and finish the mix when it’s delivered to the patch.
“Our operations manager, who grew up on a farm, came up with that idea,” says HRI Project Manager Matt Degma. “It’s pretty slick.”
Lanes are closed at 7 pm and reopened to traffic by 6 am daily Sunday through Thursday. HRI first opens all patches. Crews jackhammer out the existing concrete to just below the first rebar mat or, if conditions warrant, the deck pan. They saturate surface-dry the exposed area, pour to the deck’s elevation, and finish the surface.
Armed with a repair tool box that includes rapid-hardening cement, PennDOT is slowly but surely improving its NBI ranking. The number of state-owned bridges in poor condition has decreased 60%, from 6,034 in 2008 to roughly 2,400 today.
Click here to watch a brief video about the project.
