To meet the unique factors involved in constructing mass concrete elements on the Stan Musial Veterans Memorial Bridge, contractors Massman, Traylor, Alberici (MTA) commissioned a thermal control plan from engineering consultants at CTLGroup.
“We needed to develop and implement a good plan to reduce the thermal control period for the mass concrete elements,” says project manager Tom Tavernaro.
A key factor in successfully meeting critical strength requirements and keeping the project on schedule was using a concrete mix with a high volume of slag cement, which achieves higher strength and sustains less cracking than traditional concrete.
Following CTL’s recommendations, MTA took extra measures to cool the concrete. The contractor assembled a system of cooling tubes within the pier footings by installing more than 1.5 miles of polyethylene pipe in a 5x5-foot grid. Ice-cold water from the Mississippi River was pumped through the tubes and then returned to the river.
“With the combination of insulation on the sides of the forms and on top of the footing and using the cold river water, we were able to keep the temperature differential within an acceptable range,” says Tavernaro. The contractor also used maturity meters and temperature sensors embedded in the placements to monitor the concrete’s temperature and performance.
The special cooling measures allowed contractors to keep the bridge construction ahead of spring flooding. “If the concrete hadn’t achieved strength so quickly, the project could have been set back for two or three months,” says Mark Luther, a senior technical service engineer for Holcim (US) Inc.