I have a shotcrete pool that sits entirely above ground. There are a couple small voids/hollow spots on the outside of the pool shell. Also, water slowly seeps through one of the hollow spots. This is not causing significant water loss, just pointing out that the area is wet.
The problem is that some critter (squirrel?) is stashing acorns in these spaces. Since water is available, the nuts are sprouting. This has me worried that it might create cracks in the shell. I've fished out this year's supply of acorns but need to cover the holes before next winter's nutfest.
What is the best way to fill these voids?