Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/307110
Better Roads May 2014 13 bridge replacement being too costly, CDOT began a repair project to extend the life of the bridge an additional 10 to 15 years. Patching was completed in December 2010, and the whole bridge project was completed in Spring 2011. Crews removed deteriorated con- crete and sandblasted the newly ex- posed, undamaged surfaces, replacing reinforcing steel and adding galvanized wire mesh for structural reinforce- ment. This left areas up to 6 inches deep and 8 feet wide to be filled with concrete repair material, and a fast- setting product was needed to com- plete the work in a short timeframe. Rapid Set Mortar Mix was selected for the project, as it was able to be applied 6 inches deep in a single application and reached initial set in 15 minutes. Final set was achieved in 35 minutes, with a 2,500-psi compressive strength achieved one hour later, allowing crews to move to the next repair sec- tion. Rapid Set Flow Control, which increases the strength and reduces the shrinkage of the mix when used as a replacement for mixing water, was used to keep the repair material flowable while still retaining the same strength. Because of its superior speed and workability as well as its resistance to cracking, Rapid Set Mortar Mix was used to repair all of the bridge's horizontal and vertical overhead ar- eas, covering 5,500 square feet of the substructure. Because the rapid-setting mortar mix was able to be applied in a single application, the project saved an estimated 25 percent in labor costs and completion time. Route 95 Bridge Rehabilitation Because of the high-traffic volume on this 50-year-old interstate bridge in Foxboro, Massachusetts, the Massa- chusetts Department of Transportation (MassDOT) aimed to complete deck repairs throughout the course of two weekends. Crews milled the existing asphalt concrete and removed deteriorated concrete. Those areas were filled with a rapid-setting concrete that contained Rapid Set Low-P cement and fly ash. Rapid Set Low-P has low permeability and improved resistance to attack from chlorides and de-icing salts, and fly ash was added to eliminate any potential alkali silica reactivity problems. After patching, they placed a concrete over- layment; the 3-1/2- to 4-inch over- layment used the same rapid-setting concrete mix as the patched areas, a first for such a specification in Mas- sachusetts. Concrete was mixed on site in mobile mixers, saving time and eliminating waste. This combination of techniques and materials demonstrated that bridge deck repair can be accom- plished in a short period of time. I-55 bridges near St. Louis area Like many states, Missouri wanted to reduce lane-closure times while its bridge decks were being repaired. Many of the state DOT's early experi- ments with materials offering fast cure times had proven to be non-durable. In 2008, the Missouri Department of Transportation (MoDOT) used Rapid Set Low-P Cement for the first time in one of its bridge overlays. Follow- up testing of the material indicated excellent compressive strengths, low permeability, good bonding properties and minimal shrinkage. Based on Low-P's earlier success, the St. Louis Area District approved its use. Concrete Strategies, the highway and bridge contractor on this proj- ect, performed work on a total of six overpasses using Low-P; in every case, compressive strengths, permeability and pull off tests were well within specified range. Highway J Bridge The Highway J Bridge near Chillicothe, Missouri, was scheduled for replace- ment as part of the state's Safe & Sound