Henry County, Tennessee is home to an important automotive corridor in the southeastern United States. On a well-trafficked stretch of road there, TDOT identified a number of bridges for deck replacement as part of a statewide infrastructure plan. The DOT actively monitors bridge repair and replacement needs while seeking methods to reduce environmental impact of construction projects. 

Working closely with their cement suppliers, ready mix concrete producers began testing PLC mixes for compressive strength, setting time, air content, slump, and bleed potential. They used a mixture containing 620 lbs/cu ft of PLC with a 25% fly ash replacement. The fly ash provided better consistency for the mix. After running some 450 trial batches, producers were confident in the compressive strength results of 4000 psi at 28 days, noting little to no difference between the PLC mixes and their typical Type I/II mixes. Ready mix employees commented that it was easy to make the change.

With this information in hand, the ready mix producer approached TDOT about using PLC concrete for its bridge decks. TDOT agreed to use the PLC/fly ash mixes. As a result of the 1:1 replacement level for traditional portland cement and the additional 25% fly ash content, TDOT was able to use PLC to reduce the carbon footprint for several bridge decks while obtaining concrete with the required properties. 

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