Re-plaster and pool start-up: delay?

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D

Do it myselfer

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Oct 28, 2015
2
portland oregon
I'm about to do a pool replaster for my brother in Dallas. Everything I have read indicates that it is a good idea to delay filling the pool with water after the replaster for at least six hours, and preferably 24 hours.

IS there any reason not to wait for 2, or 3 days, or a week, or two weeks, to fill the pool after the plaster has been put on? Everything I have ever done with Portland cement based products indicates a very long cure time. Why is it a bad idea to wait a week or two to begin filling the pool and give the plaster time to cure?

Any feedback would be helpful.

Thanks
 
Do it myselfer said:
I'm about to do a pool replaster for my brother in Dallas. Everything I have read indicates that it is a good idea to delay filling the pool with water after the replaster for at least six hours, and preferably 24 hours.

IS there any reason not to wait for 2, or 3 days, or a week, or two weeks, to fill the pool after the plaster has been put on? Everything I have ever done with Portland cement based products indicates a very long cure time. Why is it a bad idea to wait a week or two to begin filling the pool and give the plaster time to cure?

Any feedback would be helpful.

Thanks
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Any links that mention waiting to fill after the plaster? I've seen some builds that wait till next day, but usually they are pebble plasters. I did quartzscapes (blue) and when the plaster hardened I did acid wash within two hours. Immediately started filling after the acid wash. If I recall correctly, Diamondbrite specs suggest a time, but also state to get a good feel of how the plaster is curing. Once dry, or hard, then move one is what it says. Quartzscapes doesn't have anything in writing, I even called them directly so I did everything based on the feel of the plaster. I wouldn't wait more than 24 hours, especially if your in a hot zone.
 
Portland Cement does cure and hydrate for many years. However, it is best to allow curing to take place with plenty of moisture available so that it doesn't dry out.
Cement (and pool plaster contains a lot of cement in the mix) also shrinks when drying takes place. Therefore, it is best to cure underwater, but only after a sufficient amount of time to allow the immediate surface to harden properly. To do that generally requires at least 6 hours to a maximum of 24 hours depending on temperature and humidity. The higher the humidity, the cooler it is (as long as it isn't freezing), the longer you can wait.

Many plasterers are afraid of the plaster cracking due to drying out, and therefore, start the water immediately after finishing. But that is not the best practice. Waiting six hours is not going to make a significant difference. If the plaster mix is thick (with a low water to cement ratio), and with no water troweling, and no calcium chloride added, then the chances of cracking are very minimal. Placing a tarp over the pool is also a good practice in hot and dry weather to prevent cracks.
 
onBalance said:
Portland Cement does cure and hydrate for many years. However, it is best to allow curing to take place with plenty of moisture available so that it doesn't dry out.
Cement (and pool plaster contains a lot of cement in the mix) also shrinks when drying takes place. Therefore, it is best to cure underwater, but only after a sufficient amount of time to allow the immediate surface to harden properly. To do that generally requires at least 6 hours to a maximum of 24 hours depending on temperature and humidity. The higher the humidity, the cooler it is (as long as it isn't freezing), the longer you can wait.

Many plasterers are afraid of the plaster cracking due to drying out, and therefore, start the water immediately after finishing. But that is not the best practice. Waiting six hours is not going to make a significant difference. If the plaster mix is thick (with a low water to cement ratio), and with no water troweling, and no calcium chloride added, then the chances of cracking are very minimal. Placing a tarp over the pool is also a good practice in hot and dry weather to prevent cracks.
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Thanks for the wisdom! It sounds like the main danger for waiting is that drying 'plaster' (cement) could shrink and crack. Anyone know of other reasons not to wait longer? By the way, OnBalance, I love all the work you have done to bring science and rigor to the pool plastering industry, and the rigorous science you bring to the complex chemistry of concrete curing. Assuming one could control cracking (by using dryer cement, slowing cure times, waiting for humid/cool days, using acrylic/other additive?) is there any reason not to wait 2,days, or a full week for filling? I know you have done experiments with 0, 6 hour, 24 hour, etc- but have you looked at a full 7 day cure for pool plaster?

Also, some people say that you cannot work a plaster seam that is setting up with freshly applied plaster- is this an aesthetic issue, or would it create water-permeable seams? For example, if I plaster a portion of the pool, and then work back so that a wet line of plaster is abutting a portion that is an hour or two old, would that be a problem? I know it won't feather out very pretty, but won't the 'green' plaster and the fresh plaster still form a chemical bond, rather than a seam? I'm asking because I am working alone, and can't use a pump to spray and trowel the plaster fast enough. Thanks in advance for your advice. (I'm not planning on using any accelerators, using very dry plaster, and possibly adding a bonding and/or anti-shrinking additive.)
 
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If it rains, that causes etching of the plaster surface - because "rain" is very aggressive.
The plaster can be stained due to dirt, leaves, etc.
If the plaster cracks, it also can delaminate (bonding failure) from the substrate beneath. This issue would be very likely by not filling within a few days.

Waiting just six hours to start filling with water would not make enough difference to cause cracking problems. It usually takes 24 to 48 hours to fill most new plaster pools anyway, and six hours more is not a major difference.
 
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