Thin crack about 10 feet long.

[sullyb]

This crack appeared several weeks after gunite was placed. I’ve notified the pool builder and he said he would look at it when he returns. I’m in Utah, and we are waiting for warmer weather (March) to continue building. Is this overly concerning, and if so, what are the proper steps to resolve? The pool was poured per engineered drawings, and the rebar exceeded the detail in the drawings. Bar placement was tighter then 12” OC as called out in spec.

 

[ajw22]

Welcome to TFP.

That crack does not look structural. Concrete devlelops those type of stress cracks. The plaster will seal the crack.

It is a bit late now but was the gunite watered after it was shot?

Watering New Gunite and Concrete - Further Reading

www.troublefreepool.com

 

[sullyb]

It was covered with concrete blankets in temps ranging from 45 to 30 degrees for two weeks.

 

[PoolStored]

It was covered with concrete blankets in temps ranging from 45 to 30 degrees for two weeks.

OOF!!

You have two dimensions working against your concrete strength...hydration and temperature...


Isothermal (constant shotcrete temperature) strength gain curves based on the Arrhenius function.

Watering New Gunite and Concrete - Further Reading

www.troublefreepool.com

 

[sullyb]

Concrete cylinder breaks came in over 4000 psi at 28 days. The mix had hot water and 1 lb of microfiber/yard. I believe the blankets did a descent job at trapping water and keeping the slab conditions humid. I’m not an engineer, just my observation of the shell as I monitored conditions generally.

 

[PoolStored]

Concrete cylinder breaks came in over 4000 psi at 28 days. The mix had hot water and 1 lb of microfiber/yard. I believe the blankets did a descent job at trapping water and keeping the slab conditions humid. I’m not an engineer, just my observation of the shell as I monitored conditions generally.

You may be ok, maybe not. At 45 Degrees F, 7 Degrees C, the air is fairly dry. We will likely never know. As @ajw22 indicated, the plaster should seal the cracks. Look forward to some swimming!

 

[sullyb]

Thanks. Is it beneficial to seal the crack with epoxy or something else prior to applying plaster. Also, since we’re on the topic, what is the minimum temperature requirements to ensure the structural integrity of the plaster?

 

[PoolStored]

Thanks. Is it beneficial to seal the crack with epoxy or something else prior to applying plaster. Also, since we’re on the topic, what is the minimum temperature requirements to ensure the structural integrity of the plaster?

I'll defer to @ajw22, but I would not put any intermediary sealant between the shotcrete and the plaster.

For applying the plaster, in general not below 40F and preferably warming up to at least 60F and not above 90F.

 

[sullyb]

Thanks for your input.

 

[ajw22]

Thanks. Is it beneficial to seal the crack with epoxy or something else prior to applying plaster.

Absolutely not. Plaster will not adhere to epoxy.

Let your builder handle it.

It is a common non-problem.

Also, since we’re on the topic, what is the minimum temperature requirements to ensure the structural integrity of the plaster?

You want the application air temperature to be above 50F and nighttime temperature not be below 40F.

You want them to limit calcium added to accelerate curing.

Plaster Installation and Maintenance - Further Reading

www.troublefreepool.com

 

[SecoSteve]

Where is the crack located in the pool?

 

[sullyb]

approximately where I’ve highlighted red in the attached picture. It’s roughly 10 ft long, most of it is kind of hard to see except the portion I posted in the original post. Only a couple of feet are obvious.

 

[AQUA~HOLICS]

Was the dirt hydrated prior to shotcrete application?

 

[sullyb]

Was the dirt hydrated prior to shotcrete application?

It was moist from previous storms, but not overly saturated.