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Heading: 1.1.1concrete roping, balls in concrete, doing flatwork
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What should a contractor do when they pour a slab and theres a ball in the concrete?

How can a mix plant prevent this from happening?

What causes this to happen?




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Sarah Wittenauer


This can be caused by several things, but hey are usually out of control of the contractor. If concrete gets to the job and it has cement balls, all you can do is pull them out.

Usually this problem is related to the order in which materials are placed into the mixer. Truck mixers are more notorious for this problem. Usually the charging order for the materials is"

Coarse aggregate
Fine aggregate
50% of the water
Cement + 40% of the water
Remaining 5-10% of the water, depending on hold-out.

Of course the problem can also be caused by blade wear or very dry concrete.

I'm not a producer, so some people may have better suggestions for charging order.

Jay
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Jay Shilstone


Merts, Inc. builds very fast transit mix concrete plants, and the following sequence is what our customers have told us works, and we have seen this happen when loading a 10 yard batch into the truck in 60 seconds.

put 60 -75 % of water into mixer (head water)
start aggregate, then start cement in a ribbon feed, with cement finishing before aggregates (NEVER introduce water and raw cement into the mixer at the same time, this is what causes the balls)
When cement is finished, the balance of the water (tail water) can go in with the last of the aggregates, to wash down the truck loading hopper.

We have seen this work for many years with some large volume companies.

Bill Mangum
MERTS, INC.
Sales Manager

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Bill mangum Mangum
 
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