New plaster problems

[thetanman]

We had our pool replastered the end of April. Plaster with quartz (Altima Mission Bay) they did sandblast and bond coat. Within 2-3 weeks some spots (stains?) appeared. Not all over pool,but just on steps and benches. They look like (for lack of better description) wet spots on concrete. The company that replastered the pool says it is a chemical problem...Ph was low and so was alkalinity. My pool guy said that even with chemicals being off, that wouldn't cause a problem this soon or just in certain spots. We are still having a problem getting the alkalinity up. We have added over 40 lbs of sodium Bicarb. Checked the levels this morning...PH 8.4 and alkalinity 50. All other levels are good. Any ideas as to what could have caused this problem? I will try to upload pictures.
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[onBalance]

Overall aggressive water would not cause those large spots. Even "acid" start-ups don't do that. In my opinion, someone may have accidently spilled some water or something else on those areas before the pool was filled. Or it is also possible that a small amount of acid could have been added undiluted in those areas once the pool was full and the pool water wasn't moving around because the circulation system was off. Check the spots for the smoothness and compare to the unaffected areas.

 

[thetanman]

The spots are on the steps and on the benches in different sides of the pool. The area with the spots almost seem to be alittle bit concaved, and smoother than the rest of the pool. I was also wondering if there might be something in the plaster that would cause the low alkalinity problem. We have been fighting it since filling the pool. The total alkalinity is at 50.

 

[Melt In The Sun]

It sure looks like something pooled there, especially in that last picture. You can see two little pools, one on each step. Any idea what could have sat there, before the pool was filled?

 

[thetanman]

Nothing that I know of, no rain or anything else, just a normal fill. When they put on the bond coat, I saw spots where moisture was seeping up through it. I mentioned it to the plaster guy and he told me not to worry about it. Some of the spots you see in picture are where I saw the seeping. Could that be the problem?

 

[onBalance]

Yes, wet spots in the gunite (which are called "weepers" by many plasterers), could be why those areas are darker. That situation changes and affects the hydration rate of the cement and could keep the plaster from lightening up as it hardens.
Also, the water in the gunite could have slowly seeped through and in and ended up causing a puddle there before completely filled. Unfortunately, I think removing that discoloration will be difficult without draining. I think the pool will have to be drained and the plaster allowed to dry out for a couple of days. I hope that will work.

No, nothing in the plaster would cause a "low alkalinity problem."