Bridge Answer Man column: Work nearly done on Eighth Street bridge
Question: What improvements are being made to the Eighth Street bridge deck?
Preceding the Eighth Street Bridge closure, many motorists didn’t even realize there was a bridge there. Some even thought the Grand Avenue Bridge would be closed for 10 days when this work was announced. Many of you are probably wondering why the Grand Avenue project required closing the Eighth Street Bridge. Here’s what you need to know:
The new Eighth Street connection will serve as a crucial link during the August 2017 Grand Avenue bridge detour. All traffic that would have gone over the bridge will be detoured onto the Eighth Street connection, over the Eighth Street bridge to Midland to access West Glenwood.
Crews have been working to make repairs to the Eighth Street bridge deck to accommodate the increase in traffic during the 2017 detour. To do this, crews first removed all asphalt from the bridge deck. The bridge’s waterproof membrane was then removed to get at the underlying deck.
After the asphalt and waterproof membranes were removed, crews began to “sound” the deck. This is a process were crews drag a chain over the deck area. This chain will detect hollow sounds and alert crews of any areas that are deteriorating. In the case of the Eighth Street Bridge, the deck was in good condition.
After the sound test is complete, crews then shot blast the bridge deck. Shot blasting is an environmentally friendly method of surface preparation for asphalt paving. Shot blasting works with an airless, centrifugal wheel that propels metal abrasive toward the surface of the deck at a high velocity in a controlled pattern and direction. Shot blasting is a time-saving process that simultaneously strips, cleans and profiles surfaces, leaving the surface dust-free and ready for asphalt application.
There is one last step before asphalting: installing the waterproof membrane on the deck. The membrane is designed to prevent water penetration through pavement surfaces and prevent potential moisture damage.
Once the waterproof membrane is installed, crews begin the finishes of asphalting and striping. The asphalt takes several hours to cure before it is drivable. Once the Colorado Department of Transportation has inspected the asphalt cure time, crews will open the Eighth Street bridge to vehicles, which is anticipated Tuesday.
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