Concrete Slab

[bobbybob]

Hi,

We have built up to DPC, and will be pouring the slab soon. The plan is to fill the area, level it with some 2x4, then bull float it, and finally finish it with a swimming pool trowel. I have some questions I'd like answered.

1. Once I've bull floated it, do I need to use a hand held magnesium float to remove the lines created by the bull float ? or can I use the finishing trowel ?
2. How long do I need to wait before I can finish trowel it ?

 

[chappers]

First a question, why do you need such a good finish, are you not screeding over the top.

in answer to your questions

1 No need
2 depends on lots of things, hard to measure in time, but basically once the wet sheen has gone and your not drawing water out of the slab with the steel trowel, but depending on the size of the slab you might need to take a view on this and start a bit earlier than ideal otherwise you might find that by the time you get to the end it's in-trowelable. Maybe consider a big blue steel float on a pole and chain, rather than a handheld steel float if it's a large area.

 

[^woody^]

Trying to get a smooth floor finish on concrete will be fun whatever trowel you use

 

[bobbybob]

First a question, why do you need such a good finish, are you not screeding over the top.

in answer to your questions

1 No need
2 depends on lots of things, hard to measure in time, but basically once the wet sheen has gone and your not drawing water out of the slab with the steel trowel, but depending on the size of the slab you might need to take a view on this and start a bit earlier than ideal otherwise you might find that by the time you get to the end it's in-trowelable. Maybe consider a big blue steel float on a pole and chain, rather than a handheld steel float if it's a large area.

I won't be screeding, it's for a garage floor, 30m^2 so pretty big. I'll be using poles for the bull float.
I want to try and achieve the best finish possible.

Trying to get a smooth floor finish on concrete will be fun whatever trowel you use

I shudder just at the thought of it - I'm not looking forward to it, I'll tell you that much.

 

[tomfe]

You'll get a good enough finished for a garage floor with a bull float.
You could hire a power float they are only about £50.
Then go over it at 90 degrees from the bull float with the blades down. Then leave it for a bit then trowel to a finish. It's not that hard.

 

[bobbybob]

Thanks Tomfe. I do want to power float but It's 50 quid to drop off/pick up the darn thing, + 50 for the day, that's well over 100 quid.

I've got another question, how long can I wait before I can put significant loads on the slab ? Once the slab is poured I will be getting around 500 dense blocks, and I won't have any place to put them other than on the slab.

 

[John D v2.0]

After 48 hours your cement should have set enough for traffic, to be safe you can put a board down to cushion it. Just don't go chucking the blocks at it!