Strategies for Accelerating Concrete Construction.
Accelerated construction projects are driven by time – whether it’s the people working, equipment available, high priority interest, or minimizing a public inconvenience. When it comes to accelerated concrete construction, a shorter curing time means adding the next story to a concrete building sooner, or re-opening a major interchange faster.
Common methods of accelerating concrete strength involve using heat or concrete accelerating admixtures. And often it comes at a cost. When the cement chemistry is accelerated, the shrinkage is also accelerated. This acceleration can quickly lead to shrinkage cracks, which occur due to volume change caused by the drying process as well as other mechanisms. Shrinkage cracks provide immediate access to water and deicing chemicals – directly to the steel reinforcement and internal concrete of a structure. Long-term, this leads to significant repairs and maintenance, and a need for a replacement well before the expected life cycle of the structure.
PREVent-C® technology is one of the only concrete admixtures that has the ability to maintain volume stability and defend against shrinkage cracks in accelerated concrete. By blending expansive components with pore water surface tension reduction, PREVent-C can increase the expected life of the structure. It has been proven to reduce shrinkage cracking by 90 to 100 percent, depending on the mix design and amount utilized.
Crack-free Accelerated Concrete
In late March of 2017, a large fire caused an Interstate 85 bridge to collapse in Atlanta, Georgia. The bridge was at the heart of a major route for commuters, resulting in temporary shutdown of businesses and thousands of people opting to work from home. The Georgia Department of Transportation (DOT) needed to rely on accelerated construction techniques to minimize the economic impact.
Prior to the repair of the I-85 Bridge, the Georgia DOT used PREVent-C as an admixture in three other bridge repair and maintenance projects. Using the technology in the concrete mix designs provided dramatic improvement versus the traditional concrete mix designs. PREVent-C® technology was selected to be added to the concrete mix for the I-85 project to ensure an efficient construction timeline and a strong, effective bridge reconstruction that would not require extensive and costly maintenance in the near future.
The Georgia DOT selected an accelerated mix and a 3-day curing period versus a more standard 7-day curing period. The selected mix design allowed for a shorter construction schedule leading to a much earlier than anticipated opening of the interstate. When accelerated strength and minimal curing are used, cracking would be visible immediately following the end of curing. When the curing was removed from the I-85 Bridge, there was no observance of cracking. A review of the bridge deck after one year in service showed changes in the concrete which remained crack free.
Put it to the Test
Order a sample of PREVent-C and schedule a trial mixture to evaluate its effectiveness on shrinkage cracking, as well as its effects on other fresh and hardened concrete properties. Or, send us your general questions about accelerated concrete construction. Contact PREVent-C experts today.