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I'm in the process of prepping the concrete underneath a new coal bin and boiler room in the basement. The area is only about 115 ft² and I have a few tight spaces that wouldn't accommodate a grinder, so I'm acid etching the surface.
The concrete was placed around 18 months ago. I did tarp the slab and wet cure it for over a week. I don't think the mason applied a curing compound, but I'm not sure (he didn't want to do the job my way, e.g., I had to vibrate all the basement walls myself because he didn't think it was necessary).
When I applied a phosphoric acid (1:4 dilution) last night, the solution frothed up a little initially, but didn't continue to bubble for more than 30-60 seconds. I was expecting a little more action, but I can't seem to find a video of anyone etching with phosphoric acid to confirm my suspicion. As I rinsed off concrete and vacuumed, I noticed a slimy texture here and there. I also noticed that the surface was drying white (calcium carbonate?)
Do you think the phosphoric acid reacted properly, or was some sort of surface treatment interfering with the process?
If the concrete doesn't actually have curing compound or sealer on it, I'm going to rent an electric pressure washer to try to remove the white film that the formed on the surface, then I'm going to etch a second time (this time with muriatic acid). Should I use bleach along with the pressure washer? Do you think I need to take steps to neutralize the acid, e.g., baking soda?
The concrete was placed around 18 months ago. I did tarp the slab and wet cure it for over a week. I don't think the mason applied a curing compound, but I'm not sure (he didn't want to do the job my way, e.g., I had to vibrate all the basement walls myself because he didn't think it was necessary).
When I applied a phosphoric acid (1:4 dilution) last night, the solution frothed up a little initially, but didn't continue to bubble for more than 30-60 seconds. I was expecting a little more action, but I can't seem to find a video of anyone etching with phosphoric acid to confirm my suspicion. As I rinsed off concrete and vacuumed, I noticed a slimy texture here and there. I also noticed that the surface was drying white (calcium carbonate?)
Do you think the phosphoric acid reacted properly, or was some sort of surface treatment interfering with the process?
If the concrete doesn't actually have curing compound or sealer on it, I'm going to rent an electric pressure washer to try to remove the white film that the formed on the surface, then I'm going to etch a second time (this time with muriatic acid). Should I use bleach along with the pressure washer? Do you think I need to take steps to neutralize the acid, e.g., baking soda?
