PLC Mixes Elevate Bayway Bridge Construction
Throughout the U.S., there are more than 600,000 bridges. No matter its size, each bridge is an important element of our transportation system. Yet the 2021 ASCE Infrastructure Report Card notes some sobering statistics: 42% of bridges are at least 50 years old; 7.5% of the nation’s bridges are considered structurally deficient; and there are 178 million daily trips across these structurally deficient bridges. Repairing and replacing this critical infrastructure will be a focus for many years.
In Florida, bridges are everywhere. In a state heavily dependent on tourism, they are especially important for access to the 663 miles of beaches and small islands along Florida’s 1350-mile long coastline. In Pinellas County Florida, south of St. Petersburg, the island of Tierra Verde and its renowned beaches are accessed via SR 679, Bayway Bridge-Structure E. In 2018, FDOT, the Florida Department of Transportation began a $56.8 million design-build project to: to replace the 60-year old bascule bridge with a high-level, fixed bridge to reduce congestion and minimize delays related to boat traffic; repave the existing SR 679 roadway between SR 682 and the new bridge; and replace a seawall south of the bridge along SR 679 in Pinellas County.
These structures are all in a marine exposure. Although marine exposures are aggressive to reinforced concrete because chlorides corrode steel, encasing metal reinforcement in concrete protects it from salt and corrosion. Sensing an opportunity to promote sustainable and performance aspects of concrete, the ready mix concrete supplier provided submittals for portland-limestone cement (PLC) mixes to the contractor, American Bridge Company. FDOT already encourages the use of PLC in all their projects. Durable concrete can be achieved equally well with either ordinary portland cement or PLC and the same techniques used to improve corrosion resistance of OPC mixes are equally applicable to PLC mixes. As a result, PLCs were used for much of the 17,704 cubic yards of concrete, excluding precast elements.
The Bayway Bridge reconstruction is expected to be completed in the fall of 2021.