Unknown pool bottom

[Cheeto02]

Hello everyone, I am hoping someone can help me with a newbie issue.
I purchased my home about 2 years ago and decided this year to put in a new liner. The old liner had a leak, likely on the bottom of the shallow end, and a lot of wrinkles. The pool was new in 2006 but I cannot find anyone at this point who knows who put it in. FYI this is a 20' x 40' inground pool with a 3'5" shallow end and a 9'4" deep end. I pulled out the old liner so I could get the most accurate measurements for the new liner and I am now stuck trying to figure out how to repair the bottom and sides of the pool. A majority of the bottom is hard as rock, a screwdriver can barely nick the surface. However a large area around the stairs and ladder and some of the perimeter has cratered really bad. Also where the sides meet the hopper have crumbled really bad. I've attached some photos for a visual. These damaged areas where the surface has degraded has nothing left but what looks to me like sand. It almost appears as though the bottom of the pool is nothing more than sand with a very thin hard layer on top. I've been doing research trying to figure out what the bottom is so I can repair it but I'm at a loss.

Any insight would be appreciated. Thanks.

 

[jamjam]

it could be a portland cement sand mix - basically x parts sand to x parts cement. It could also be just sand with some kind of binder prayed on top in parts. How much of it needs to be patched, % wise?

Inground Vinyl Pool Floor Options

Inground Vinyl Pool Floor Options are basically vermiculite, or concrete, or sand, or some mix or blend of the three. Read More...

blog.intheswim.com

 

[Cheeto02]

it could be a portland cement sand mix - basically x parts sand to x parts cement. It could also be just sand with some kind of binder prayed on top in parts. How much of it needs to be patched, % wise?

Inground Vinyl Pool Floor Options

Inground Vinyl Pool Floor Options are basically vermiculite, or concrete, or sand, or some mix or blend of the three. Read More...

blog.intheswim.com

Hard to say for sure but I would guess around 10% of the total surface area needs to be repaired.
Would a portland cement sand mix harden throughout? in this case it appears that only the surface has hardened, although that could just be due to years of decay.

 

[jamjam]

i think that might depend on how it was applied - if it was packed dry then sprayed with water, it could be that the water only penetrated the top - not an expert so I am just guessing - I am sure one of the pros here might chime in.