concrete curing in impervious tank

[Soldierson]

Hi,
I have an unique project requiring the curing of concrete cast in a fiberglass tank. I am designing a footing retrofit inside an existing fiberglass sewage wet well lift station. The concern of the client is time. The lift station retrofit needs to be completed as quickly as possible so that downtime is minimized. The plan is to install a spray on liner on the footing to prevent chemical corrosion of the concrete and steel. How can I determine the proper amount of curing time when the concrete can only cure to the top surface so that the spray on liner doesnt a) inhibit the curing, and b) the concrete doesnt continue to cure and shrink away from the liner. The liner company has been consulted and indicates 10-14 days, but I would like to hear other opinions.
- Soldierson

 

[JedClampett]

Concrete curing intent is to reduce the amount of water escaping from the surface, instead of forming the cement water matrix. Water curing, liquid membranes and sheets all are applied to do this. So your spray on liner is actually a better curing situation than most. You should have no concerns.

 

[epoxybot]

Don't they have moisture test kits in the flooring & coatings market?

 

[cvg]

amount of shrinkage is dependant on mix design, you may be able to get more data from your concrete supplier on cure time, strength gain and shrinkage rate. shrinkage continues for years, so you need to determine how much is allowable. However, it is clear that the shrinkage will be very small and that quite a bit will occur in the first few days

https://insights.basf.com/files/pdf/Shrinkage_Of_Concrete_CTIF.pdf

 

[Soldierson]

Thanks to all,
The curing concern is to prevent the liner from separating from concrete due to excess moisture. A local expert agreed with the moisture testing suggestion. We are developing a plan to monitor surface moisture and compare against the manufactucturers recommended moisture for liner application.
Soldierson