We are just about to start plaster on a new gunite pool and I was squirting off the mud and extra mortar when I saw two cracks on the stairs.

Squirting more water, I was able to go down about 5 inches with just hose pressure and it is not holding water. I believe this area was hand packed. Another area has sand like consistency where they had to dig up a pipe. It has been about 6 weeks so I would think it is cured.

Where can I send a sample off to insure it is strong enough?