New slab question

[premierjax]

Hey guys I just had a 36x60 slab poured on 12/31. I finally am getting around to cleaning it off so I can put a sealer on it. My question is 36x36 was power trowled, and when I started pressure washing it with an old home depot press. washer the polished top coat started coming off!!! I can see the rock now and the finish is def. not smooth!! Any ideas? Should I not pressure wash to prepare for the sealer?

 

[readhead]

Probably dried to fast. Why did you wait till now to seal it although it probably doesn't matter. Call the concrete guy and ask him what he is going to do about it.

 

[premierjax]

I dont think it dried to fast, it was pretty cold and I kept it wet. I guess my question is, is this normal? Or should I be concerned

 

[kd3pc]

not normal and your contractor should make it his concern....something is not right

 

[readhead]

Not normal at all. Concrete guy needs to see it asap.
How cold was cold? could it have frozen?

 

[brownbagg]

why are you pressure washing soft concrete, how old is it, only a month old, i would of waited till at least 90 days, yes strength suppose to be 28 days. why are you putting a sealer, its a garage

 

[premierjax]

It was around 50 or so when we poured but 8 or 9 days later we did hit mid 20s and it has been cold this whole month around low to mid 30s

 

[premierjax]

why are you pressure washing soft concrete, how old is it, only a month old, i would of waited till at least 90 days, yes strength suppose to be 28 days. why are you putting a sealer, its a garage

The night of the pour it rained so dirt jumped up on the edges, so trying to clean it enough to seal it. Im not doing anything fancy just the Legacy HD6600 so it will resist fluids and what not better than without. After over 30 days it wouldnt be hard enough to pressure clean?

 

[nolimits76]

Sounds like delamination.

http://www.concretenetwork.com/concrete-delamination.html

 

[premierjax]

Sounds like delamination.

http://www.concretenetwork.com/concrete-delamination.html

After reading about delamination I just went around and banged on the whole slab, everything sounds good and solid

 

[ConCretin]

when I started pressure washing it with an old home depot press. washer the polished top coat started coming off!!! I can see the rock now and the finish is def. not smooth!!

If the concrete surface is coming up in 'sheets', it's de-lamination. This occurs when air and/or bleed water are trapped just below the surface of the concrete creating a plane of weakness. It usually occurs in hot windy weather when the surface sets quicker than the underlying concrete. Air entrained concrete is especially subject to de-lamination with a hard toweled surface

De-lamination is usually found be dragging a chain, hammer, etc. across the surface listening for changes in tone.

If the surface is 'eroding' away under the water pressure, I'd suspect a frozen or otherwise deficient concrete surface. Based on your description, it doesn't sound like freezing. The surface probably would't be damaged by freezing as long as the concrete had a day or two to gain strength (about 500 psi) before experiencing freezing temps. A very low water/cement ratio or a lot of water added to the surface during finishing could have created this problem.

 

[premierjax]

If the concrete surface is coming up in 'sheets', it's de-lamination. This occurs when air and/or bleed water are trapped just below the surface of the concrete creating a plane of weakness. It usually occurs in hot windy weather when the surface sets quicker than the underlying concrete. Air entrained concrete is especially subject to de-lamination with a hard toweled surface

De-lamination is usually found be dragging a chain, hammer, etc. across the surface listening for changes in tone.

If the surface is 'eroding' away under the water pressure, I'd suspect a frozen or otherwise deficient concrete surface. Based on your description, it doesn't sound like freezing. The surface probably would't be damaged by freezing as long as the concrete had a day or two to gain strength (about 500 psi) before experiencing freezing temps. A very low water/cement ratio or a lot of water added to the surface during finishing could have created this problem.

LLWillysfan, it was down for 8 days before we hit the mid 20's so I think Im alright there. Because it was so cold the day of the pour we went late into the night waiting for it to set up so we could power trowel it. The concrete was down by noon and I wasnt paying attention to what times we troweled but the last time was around 7-8 at night. While he was troweling he just had a bucket of water that he would sprinkle water down every now and then in front of the machine, so I dont think there was to much water down while finishing. I told the guys I wanted a floor that resembles a commercial or Home Depot style finish. The finisher told me that he will be back at 5:30 the next morning to "burn it in". Ive talked to someone that said troweling that long after the pour will make the surface weak. Do you think this might be the issue? Or should I just give it more time before washing it?

 

[Stuart in MN]

Another thought is how powerful is your pressure washer, and were you spraying straight down at the surface or spraying at an angle? I can see where putting the nozzle right up against the surface would cause it to erode, but if you're just sweeping the spray back and forth across the concrete it doesn't seem like it should cause any damage.

 

[nolimits76]

Do you have a copy of the mix design by chance? Also, do you know if any additives (hot water, water reducer, etc) was added?

What doesn't make sense to me is you say temps were okay during the pour. Then you say you waited until later that evening (7-8pm) to trowel because it was too cold when you poured. Typically temps drop at night, not increase.

No offense meant, I'm just not sure I clearly understand the situation.


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[PWC Repair]

Sounds like too much water was brought up during the finishing process....finishing started too early.

 

[premierjax]

Do you have a copy of the mix design by chance? Also, do you know if any additives (hot water, water reducer, etc) was added?

What doesn't make sense to me is you say temps were okay during the pour. Then you say you waited until later that evening (7-8pm) to trowel because it was too cold when you poured. Typically temps drop at night, not increase.

No offense meant, I'm just not sure I clearly understand the situation.


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It was in the 40's during the pour, they started troweling maybe around 2 and hit it about once every hour till 8, they said because it was cold it wasnt setting like it should. I just spoke to one of the finishers he said there was calcium added to the mix but that doesnt show on the receipt, it just shows how may gallons of water were added per truck. It was cold all week but didnt hit freezing temps until 8 days later

 

[premierjax]

Another thought is how powerful is your pressure washer, and were you spraying straight down at the surface or spraying at an angle? I can see where putting the nozzle right up against the surface would cause it to erode, but if you're just sweeping the spray back and forth across the concrete it doesn't seem like it should cause any damage.

I believe its a 3500 psi form home depot. I was using a 15" surface cleaner.