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Old 04-13-2017, 10:09 PM   #5
NN5I
Carl, nn5i
 
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Join Date: Sep 2011
Location: Tallahassee, FL
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That is pretty quick. After the columns come the pier caps, then the beams. Once the beams are in place, the bridge is perhaps 1/4 built.

Carpenters build forms for the concrete diaphragms that go between the beams. Then the diaphragms are poured (wait several days for them to set), screed rails erected lengthwise, deck forms built (a major job), and reinforcing bars placed inside the forms (along with the cardboard-like contraction- and expansion-joint separators). Then comes a big day: pouring the deck and leveling it with a "screed" which is a huge oscillating straightedge that travels on the screed rails, all the while oscillating sideways. Then the concrete-finishing crew work and broom the concrete surface and spray it with a temporary waterproof spray ("curing compound") to keep it from drying out before it sets (drying out would weaken the concrete disastrously). Sometimes, instead, they just put sprinklers out to keep it wet for a week.

Then they form and pour the curbs, wingwalls, etc., and at last install guardrails, handrails, and stuff.

I left out a lot, such as the surveying crew that sets the elevations along the screed rails, and stuff like that. If they're actually going to finish it in May, they have to be quick.
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