Content area
Full Text
This past fall, work was completed on the deck rehabilitation of the historic 107-year-old Hartland Covered Bridge, the longest covered bridge in the world. Existing wooden planks covered with asphalt were replaced with new timbers coated with a low-modulus, low-viscosity epoxy polymer overlay intended to protect the wood and steel deck components from water and salts and prevent corrosive intrusion to the concrete slab.
The bridge, which crosses the St. John River between Hartland and Somerville in New Brunswick, Canada, officially opened on July 4, 1901, with a 3c" toll charged for pedestrians, 6e1 for a single horse and wagon, and 1 2f for a double team. It measures 1,282 ft (391 m) in length and consists of seven covered spans with four reinforced concrete slab spans. A Canadian national historic site since 1980, the bridge today handles automobile traffic (toll free), although restrictions include a maximum vehicle weight of 1 0 tons and a maximum height clearance of 13 ft, 9 in (4.2 m).
For the bridge's recent extensive renovation, the bridge owner, the Government of New Brunswick Department of Transportation, opted to use an epoxy polymer coating system instead of asphalt or concrete as a protective barrier on the new wood deck because it is lighter, more flexible, and more corrosion-resistant, says Stephen L. Raleigh, Eastern Area manager with Unitex Chemicals (Kansas City, Missouri), the manufacturer of the epoxy polymer used in this project.
"The wooden bridge is unique because there are so few that exist. Restoring it required a different type of thought process," says Raleigh. "There are two concerns with preserving a wooden bridge. The steel post tensioning system and the concrete slab need to...