Split Keel Repairs ?

[Ahnlaashock]

There is a 30 footer in Chicago, that has a split keel.
From the look of the damage, it appears to be concrete inside fiberglass, with the fiberglass split open and the concrete decayed/crumbling out. The weight of the boat settling on it due to the cradle not supporting the boat properly, or the keel having water in it and freezing would seem to be the suspects here. Either way, the concrete is rotten to some extent.
How big of a job is it to fix something like this?
I emailed them and they sent me a set of instructions that called for drilling and using resin to stabilize the concrete, and then glassing back over that.
That might work on the outside, but does not seem capable of addressing whatever caused the rotten concrete in the keel in the first place.
What is considered a proper repair in a situation like this?