Problem with pour? soft surface

[ersatzs2]

OK so I got set up to prep my floor prior to the epoxy-coat finish. I got the power washer out intending to give it a good cleaning prior to etching. Instead, I found that holding a 40 degree nozzle an inch from the surface removed the surface skin. The rough underside looks great from an adhesion standpoint, but I just spent 5 hours and didn't finish one bay. Not sure how to have avoided this. Unfortunately I wasn't here when they poured. They had strict instructions not to use any curing agents, and I asked for a rough surface. But it is pretty smooth and comes off easily with the washer...

 

[bmwpower]

Oh man. Sounds like the slab got too cold/wet after they poured. Was it cold that day/night? I had the same type of problem when after they poured mine. The next day it poured rain and some of the slab got wet.

This was all pretty much fixed when I ground down the surface for epoxy...the top layer came with it.

 

[PAToyota]

Actually, without curing compounds did you do anything to keep the slab moist? As BMWPower says, if you have too much water - either bleed water or a heavy rain - it can cause problems. But also drying too quickly will do what you say yours is doing.

 

[ersatzs2]

Actually, without curing compounds did you do anything to keep the slab moist? As BMWPower says, if you have too much water - either bleed water or a heavy rain - it can cause problems. But also drying too quickly will do what you say yours is doing.

Here are some photos. No it didn't rain, and it wasn't extraordinarily hot or cold. Maybe it did dry too quickly; it was late september. I asked them not to use curing agents because back when I was assuming I'd have someone do this professionally, that's what they advised. Sheesh. It is going to take me about 12-13 hours to prep the rest of the floor...

 

[bmwpower]

Hold on. I wonder if a floor scrubber with a course pad will accomplish the same thing? That would take you 1/4 of the time, at most. Looks just like mine did though.

 

[PAToyota]

Typically, if we aren't using curing compounds we ask that burlap be put down and kept moist for seven days. I can't really get a feel from your photos, but if it's like an eggshell coming off the top of the concrete then that is the surface "crust" that dried too fast.

 

[vinculum]

I found that the course pad will actually start to polish the floor if you spend too much time in one area. When i rented the machine, i choose the black pad, which was the roughest pad they had (Home Depot). I spent enough time to remove the tire marks and clean up any dirt and quickly moved on. Since he is doing an epoxy coating as opposed to a sealer, like me, this may not be the best option. I think I've seen reference to a "scarifier" machine thats even more aggressive to concrete floors. Might be something to look into...

Dr V

 

[ersatzs2]

So I went out and rented a scarifier. Yes it actually 'polished' some areas initially, so I changed all the abrading wheels (it uses two pairs of three spoked axles with 10-15 star shaped washers) It cut curved rings into the surface, but didn't remove nearly as much material as power washing. So I made a lot of dust but didn't get anything like the 100 grit feeling of the first bay. But life has to go on so tomorrow I will acid etch and call that prepped. Once again, I see the value of having the pros do this. Thanks for the comments.

UPDATE: Ok so after using the scarifier, I went over those areas with the power washer. now the surface really came away easily. I then acid etched all the areas where the surface wasn't completely removed. Today it looks pretty good. Also UPS arrived today (mon) with my spiked shoes so this weekend I am ready to put down the epoxy.