Bridge has concrete

--bridge-cemet-2It took just one day, Sept. 17, and a mere 430 yards of concrete, to cover the bridge at Old Town. The first 140 yards were placed from the south side until that boom couldn’t reach any further, then the rest was placed from the pumper on the north side.

The concrete is eight inches thick and took eight hours to finish, according to Howard County Engineer Nick Rissman. It then took another three hours to add burlap and sprinklers.
(1) First, the concrete was poured into the boom pump to be distributed across the rebar on the bridge. (2) Following that is a device that looks like a hand-held vacuum. It vibrates to help consolidate the concrete.

(3) Next is the screed, a roller-type tool that automatically levels the concrete and puts it at an exact slope. For this project it is a 1.5 percent slope. (4) Hand work is also done to smooth around the rebar sticking up out of the bridge, which divides the road from the walk/bike path. (5) Next, a worker brooms and rakes the concrete. The sidewalk section was not raked, so it’s not as rough. During this process, Rissman explained, “A white pigment, called curing compound, is sprayed on the concrete after it is raked.”

Lastly, it took about three hours to add acouple layers of burlap over the concrete and use sprinklers for moisture to help the curing process. The concrete is tested to see how well it has cured. Probably after seven days, the forms have begun to be removed and backfill can be added so the approaches can be poured.

A history of the bridge can be found on page seven.


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