C30/37 w/c 0.5 xc4+xf3 Must not be troweled?

[MackanM]

Hello

I will be pouring concrete next week and have ordered according to the engineer
C30/37 w/c ratio 0.5 xc4+xf3.

The response from 2 concrete companies was that it should not be troweled because of the air. That the concrete might detach.

The only reason for troweling is because we want a concrete floor.

It's good with air because it's soon freezing temperatures and we are building with blocks that might not get a roof until next year.

How important is it with air and should we reduce or remove it completely?
We will pour when it's sunny for 3 days and 12 degrees Celsius.
We will manage to get over 5MPa in the slab.

I guess it is not possible to scrub the slab either because it becomes a dense surface

Share your tips and advice?

 

[xLnT]

What need underlies this concrete mix?
What do you mean by air in this context?

 

[MackanM]

xF3 means air according to the supplier. The air creates space in the concrete that helps if it freezes. Then the water can use that space to expand.

It is usually not used in residential slabs.

I will be casting next Tuesday, and it will be 10 degrees with sun for 3 days. It never goes below 6-8 degrees at night.

I prefer not to have air because I want to trowel, but it's not possible with this concrete mix.

We should reach 5mpa after 3 days.

 

[xLnT]

xF3 means air according to the supplier. The air creates space in the concrete that helps if there is a freeze. Then the water can use that space to expand.

You usually don't have it in residential slabs.

I will be pouring next Tuesday and then it will be 10 degrees sunny for 3 days. It will never drop below 6-8 degrees at night.

I prefer not to have air because I want to trowel, but it's not possible with this concrete mix.

We should achieve 5mpa after 3 days.

Then it seems there's nothing to be done.
Can you have a polished concrete floor if it contains air as you write?

 

[MackanM]

No, they say that the concrete can release on the surface. We are considering Microcement instead.

want to know what is cast when it's cold 10 degrees for 3 weeks

 

[xLnT]

No, they say that the concrete can release on the surface. We are considering Microcement instead.

I want to know what you pour when it is cold 10 degrees for 3 weeks

Why would that be a problem? Those are well optimal conditions for pouring in, right?
Cures slowly.

 

[MackanM]

Yes okay but is it that kind of weather that you need air in the concrete or can you manage without it?

 

[xLnT]

Yes okay but is it such weather that you need air in the concrete or can you manage without

I'm not knowledgeable enough to know why you would have air in the concrete at all if you're casting in above-freezing temperatures.
Normally, you vibrate the concrete to get rid of air.
But you have a designer who must be able to determine the issue, what does he say?

We cast our 350 sqm with regular 20/25 one November day, admittedly in Skåne but the temperatures were roughly the same as now.
On the other hand, we had no drying requirements on it either.

 

[MackanM]

I'm not knowledgeable enough to know why you would have air in the concrete at all if you're casting in above-zero temperatures. Normally, you vibrate the concrete to get rid of air. But you have a designer who must be able to determine the issue, what does he say?

We cast our 350 sqm with regular 20/25 one day in November, admittedly in Skåne, but it was about the same temperatures as now. On the other hand, we had no drying requirements for it either.

Yes, exactly. I will be casting in Malmö. Did you cast it yourself or hire a company?

 

[xLnT]

Yes, exactly. I am going to pour in Malmö. Did you do it yourself or hire a company?

We hired a company to pour, it needed to be sloped, etc., so we didn't dare to do it ourselves. We were recommended not to float, which we regret. The result wasn't great from just screeding. So we will probably grind the concrete even if we're going to lay flooring on top.

 

[MackanM]

How strange? Why did you get that recommendation? Is there a possibility to see some pictures of how it looks like only with slodning? Close-up normal picture.

 

[xLnT]

How strange? Why were you given that recommendation? Is it possible to see some pictures of how it looks only with slodning? Close-up normal picture

I have this from a thread I created after the casting.


The advice was that it would seal the pores and that it would be worse. But we finished the workshop, which turned out very well. So my advice is to trust your gut feeling, stand your ground, and question if you're uncertain.

 

[MackanM]

Did it become grainy or is the ballast too visible?

 

[xLnT]

Did it become grainy or is the ballast too visible?

In some spots, they didn't lower the ballast enough, so it's bumpy there, but you can sand that down quite easily. It's more that it became uneven in certain areas; the leveling and vibrating could have been done better.

 

[MackanM]

Aha okay. The dilemma we have is that we don't want the ballast visible, just polished concrete skin.