Practice run finishing concrete - harder than I thought!

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Old 11-13-16, 06:19 PM
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Practice run finishing concrete - harder than I thought!

Hi,

I made a 2'x1' form and poured 1 bag of quickcrete concrete into it and ran through the finishing steps. screed, darby and float.

It was not as easy I thought it would be. I could bring up cream Ok but it seems like the aggregate was too close to the surface and made it difficult to get a smooth surface even though I brought up plenty of cream and I was angling the float. Seemed like the cream was thin also - in videos it looks like the cream is pretty stiff. On videos it looks effortless and I don't see the floats catching on any aggregate.

I hoping it's because maybe the bagged concrete is not optimized for finishing?

for my project I will be getting the concrete by trailer. I have done this before but only for rough slabs that were covered with stone or brick.

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Old 11-14-16, 03:08 AM
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Properly mixed bag concrete should finish the same as concrete out of a truck. On small slabs I take a garden rake to both work out any air pockets and settle the aggregate. How big of a slab will you be pouring?
 
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Old 11-14-16, 04:51 AM
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What they probably don't show on the video is how long you need to wait before you trowel the concrete. If you trowel concrete too soon it just brings a lot of water to the surface. Done improperly, the slurry you create by troweling too soon will weaken the surface of the pad. You pour the concrete, strike it off with a board (sawing motion) then you wait. Once the concrete is the proper consistency, then you trowel it. How long you wait depends on how wet the mix was in the first place, the temperature and humidity... and any additives placed in the mix.
 
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Old 11-14-16, 01:28 PM
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Thanks,

I'll try it again. The article I read says use the darby right after screeding but I'll try waiting.


After thinking about it, my problem is that the cream is way too watery like you said so the float will simply move the cream around and scrape the aggregate. Like they say wait until the sheen is gone, right?

I have a 35'x4' walkway already formed but I know I need help on that. It's not just a simple screed because it has 3 circular drains that will require sloping the concrete (they are about 1" below edge of form).

Also need to replace about 12' of sidewalk and if I mess that up everyone will get a good laugh!
 
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Old 11-14-16, 02:34 PM
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For me the hardest part of finishing concrete has always been the wait for the initial set. I have had to wait more than an hour at times before I could do the finish troweling, maybe as long as two hours on occasion.
 
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