Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/412488
28 November 2014 Better Roads Applications & Innovations towns surrounding Mount Rushmore have resident popula- tions that number in the hundreds, the memorial is visited by nearly 3 million people each year. Furthermore, snowy win- ters – Mount Rushmore is 5,680 feet above sea level – mean- ing that prime construction times coincide with the tourist season. The repair schedule for Highway 16A was restricted to the narrow window of time in which temperatures were warm enough to accomplish the roadwork but closures in- conveniencing the traveling public were minimized. Repairing bridges with epoxy chip seal By April 14, repair efforts on four pigtail bridges were under- way. The repair method chosen was two-coat bridge deck ep- oxy chip seal. As per the South Dakota Department of Trans- portation (SDDOT) Standard Specifications for Roads and Bridges, ep- oxy used must consist of a base component and a hardener; the second component of the system is a cover aggregate that conforms to specified hardness and gradation. The placement process on Highway 16A involved application of the mix at 40 sq.-ft. per gallon with a second application occurring three or four hours later, applied in the amount of 20 sq-.- ft. per gallon, explains Ryan Steinback, project manager, J.V. Bailey Co., Inc., the prime contractor for the bridge work. The two coat application of the product improves the surface's life span and wearablilty. Epoxy chip seal is a favored method of bridge repair when dealing with worn decks because it seals micro-cracks in the concrete decking, protecting the structure's rebar from salts. The epoxy resin also binds well with concrete decking on the bridge. Cover aggregate provides skid resistance, improving the safety of the roadway. Epoxy chip seal's easy application process and the fast cure time also help keep project sched- ules on track. SDDOT specifications require diamond grinding of bridge decks in preparation for the placement of epoxy chip seal overlays. Grinding eliminates existing tining and irregularities in the road surface. A ground profile affords a clean and uni- form surface, improving the adhesion of the chip seal coating. The SDDOT specifications dictate longitudinal grinding that results in parallel corduroy texture consisting of grooves be- tween 0.090 and 0.130 inches (2 and 3 mm) wide, with the distance between grooves being between 0.060 and 0.125 inches (1.5 and 3 mm). The peaks of the ridges are required to be equal to or less than 1/16-inch (1.5 mm) higher than the bottom of the grooves. The existing surface on the 16A bridges had been in place since 1991 and was very rough, so Epoxy chip seal is a favored method to bridge repair when dealing with worn decks because it seals micro-cracks in the concrete decking, protecting the structure's rebar from salts.