Concrete pool deck settling.

Our pool is 38 years old, but always well-maintained, with no major problems.
Until now.
Over the past month or so, I've noticed 3 areas where the concrete slab surrounding the pool has started settling along the control joints. In all cases the settling is on the outside of a corner of a slab, causing the corresponding inside corner to rise up damaging the coping on the pool's edge.
The settling is only about 1/2 to 3/4", but I'd hate to see it continue as the damage could be significant.
Each slab is roughly 3' x 5-6'and is approx. 5" thick.
There is no-one within 150 miles+ of where I live that does the foam injection leveling I have seen online. The contractors I have talked to want to jackhammer the slabs out and re-pour, but I want to think that would be the last resort due to damage to the surrounding area, fencing, and the pool itself, not to mention the total expense involved.
I have seen some youtube videos where canned expansion foam is injected through holes drilled through the slab, but I'm not convinced due to the inaccuracy of the leveling. The situation could be made worse.
I am thinking of digging beneath the settled corners of the slabs and using jack(s) to bring them level, then refilling the void with material that won't compress.
All ideas, recommendations, warnings most appreciated!

 

I'm having a similar problem. My pool and deck is 45 years old. There aren't any mudjackers near me either but they do travel. I really can't picture trying to lift the deck myself.

 

You need to look at those videos' a little closer. Guy at work was telling me the same thing, but those cans do not have the pressure needed to raise a slab. The ones that actually do it physically raise the slab with jacks, excavate the area underneath then spray the foam under the slab.

I've had both foam and mud jacking, the only problem I had was one slab raised with foam expanded a little too much before they caught it so wasn't thrilled about that but it has held up for 6-7 years so far!

 

Easiest is to hire a mud jacking company. They will drill some holes through the concrete and inject grout at high pressure to lift the slab. The grout hardens and forms permenant support under the concrete. Nobody in my area does mud jacking so it's a pretty expensive process for a small job since most of the expense is travel time. But, if you have a bigger job or live in a bigger city it may be reasonably priced.

I have done some jacking of slabs. I used a method similar to the videos online but instead of using spray can foam I bought a structural, two part foam kit. The foam is more expansive and much stronger when cured. I first mechanically lifted the slab then injected the foam through multiple points to support it so it wouldn't settle back down. The foam is expensive but it was less than $1'000 for the job I did.

 

Good to know, I'm not the only one with this problem!
I have a line on a company, now. Wish me luck!

 

The only thought that I had that is concerning is raising the deck near the pool and have the pressurized product push the coping and tile out. My primary fill is sandlike.