Problems with freshly poured concrete building pad.

[ben2go]

Yesterday, Friday 12/3, the wife and I, mixed and poured 70  80lbs bags of Quikrete concrete mix to make an extension on a small building pad. It's over tamped earth topped with tamped #5 washed stone. It had minimum fines in it. I could walk on the stone and not leave a dimple.

I went and checked it today. We have a 1ft by 6ft dip in our concrete and one corner slumped. We also came out with an extremely rough finish. The dip is just enough to be noticeable and the corner slumped about a 1/4 to 1/2 inch.

We have been reaching near freezing temps at night, with 50's and 60's during the day. We're expecting 40's-60's with rain from Sunday until Tuesday or Wednesday. To hold in heat, I have plastic sheet on the concrete, heavy canvas tarps on top of that, a large thick poly tarp covering it all, and held down around the edges with 4-inch concrete block. We made sure everything was laid out evenly and smooth.

I have left the forms in place, and they will stay there for at least a full week.

What can I do to get the corner and dip filled and back to level? I need the concrete strong enough to roll motorcycle lifts around, with a full dressed motorcycles, and not crack through the concrete. The pad is a full 4-inches.

[Redoverfarm]

Did you allow it sufficient time to set and trowel it out.  Placing the covering prior to it being at that stage will produce a rough finish.  As far as the dip that is because it has settled or air has worked it's way to the surface leaving a void which the concrete will settle into.  No other explanation that would come to mind.  Without removing that portion and repouring I might suggest a concrete leveling compound. I would imagine the weight you are describing would be in the neighborhood of 850 #.  It should not really affect the leveled area.  You might consider a rubber type snap together tile something similar to those you see for garage floors. The roughness can be dressed (ground ) if you plan on leaving it uncovered.

It is very difficult to get a good floor finish when you are mixing so little quanity (bags) at a time and adding it to the previous mix. Footers and the like don't require a good finish but floors I generally order pre-mix and make the pour at one time.  Once it has pre-set bull float, then after sufficient time using knee boards hand trowel the finish smooth. 

I doubt that the temperature is the culprit. The concrete will develop heat when curing and unless it is well below freezing for an extended time it should not affect it.  The temperature will affect the time for it to set to allow finishing though.  With cooler temperatures it may take twice as long as it normally takes to be able to finish it.     

[ben2go]

Did you allow it sufficient time to set and trowel it out.  Placing the covering prior to it being at that stage will produce a rough finish.  As far as the dip that is because it has settled or air has worked it's way to the surface leaving a void which the concrete will settle into.  No other explanation that would come to mind.  Without removing that portion and repouring I might suggest a concrete leveling compound. I would imagine the weight you are describing would be in the neighborhood of 850 #.  It should not really affect the leveled area.  You might consider a rubber type snap together tile something similar to those you see for garage floors. The roughness can be dressed (ground ) if you plan on leaving it uncovered.

It is very difficult to get a good floor finish when you are mixing so little quanity (bags) at a time and adding it to the previous mix. Footers and the like don't require a good finish but floors I generally order pre-mix and make the pour at one time.  Once it has pre-set bull float, then after sufficient time using knee boards hand trowel the finish smooth. 



I doubt that the temperature is the culprit. The concrete will develop heat when curing and unless it is well below freezing for an extended time it should not affect it.  The temperature will affect the time for it to set to allow finishing though.  With cooler temperatures it may take twice as long as it normally takes to be able to finish it.     

Yes. I let it set and troweled out a smooth finish. I wasn't going for a polished finish,but smoother than a brushed finish. Which is about what I eneded up with.

It's to much to cut out and redo. I have to have the building up and start moving in before Christmas. I'll try a technique I saw on youtube using cement mix and a bonding agent. I had considered doing a garage floor paint. I think epoxy coating may be overkill. I need to be able to roll my motorcycle lifts over the floor without hanging up and causing the motorcycle to flop off the lift. The wheels are tiny,about 1.5 to 2 inches in diameter.

[NathanS]

1/4 to 1/2 off you probably wouldnt' even notice once you have everything framed up.

The 'old way' to resurface concrete would be anywhere that needs a big patch you mix 1 portland to 2 sand, then level it out with a trowel and smooth with a sponge or sponge float. After that mix portland and water to a latex paint-like consistency and paint the whole slab. It will look good. You could add some of that bonding glue stuff with the water... the other really important thing is that you wet the concrete down before patching/painting.. that will make the new portland stick really well.


That is how they resurface concrete driveways, which is sort of a maintenance thing you have to do every year or two. But since your slab won't be in the elements it could be a pretty permanent solution. The nice thing with just using portland (which is basically white washing) is that you can always redo it as many times as you want... very forgiving.

Even without doing any of this the slab will easily support your motorcycles or anything else you put on there.

[ben2go]

I'm not worried about the base slab. It's re-enforced with rebar. I'm worried about chip out of the level coating I put down to get everything nice and smooth. I saw the video that talks about what you just stated.