When a tanker truck crashed into a bridge on a high-traffic interstate in May 2020, the Texas Department of Transportation (TxDOT) moved quickly to make emergency repairs. Traveling along I-10 in Luling, the truck was too tall to clear the underpass, taking out the bridge’s cross beams.
To replace the damaged cross beams with new ones, TxDOT first installed 10 concrete pedestals to support the beams. The plan was to install the cross beams as soon as the pedestals reached 3000 psi to accept the load. Because TxDOT wanted the beams to be placed within a 24-hour time frame to minimize traffic disruption, engineers specified a fast-setting concrete mix with high early strength. Final specified compressive strength needed to be 4000 psi.
Rapid Set® Concrete Mix met and exceeded all project requirements. The high-performance structural repair material sets in 15 minutes and reaches compressive strengths of 3000 psi in one hour and 4500 psi in 24 hours. It can be applied from 2 inches to 24 inches thick and is ideal when fast strength gain, high durability and low shrinkage are required.
THE RIGHT MIX
Contractor Hunter Industries of San Marco, TX, formed the 10 7-inch-tall pedestals during the day and placed five 28-inch-thick precast concrete beams on top of the pedestals later in the evening.
Because daytime temperatures rose as high as 92 degrees Fahrenheit, the contractor worked with CMC Ready Mix of Helotes, TX, to extend the concrete’s workability. They did this by adding two packets each of Rapid Set® FLOW Control® water-reducing additive and Rapid Set® SET Control® set-retarding admixture to every four-bag batch of Rapid Set® Concrete Mix. As per TxDOT requirements, 3.9 quarts of water were added per bag. The contractor used two concrete batches to complete each pedestal.
The concrete was blended via gas-powered concrete mixer, placed, finished by trowel, and allowed to wet cure. Local engineering firm PaveTex created and tested concrete cylinders for each pedestal to confirm compressive strength.
