Good I’ve seen the fibreglass ones float after they’ve been pumped and a heavy rain comes. If the pipes are ok what I would try would be stone veneer mortar You can get it at most lumber yards it has an epoxy type glue in it. Chip out as much as you can use air compressor to blow all loose concrete and dust if concrete is damp good if it is bone dry squirt a little water on it. Then mix according to instructions on bag and forcefully Chuck, throw it in to the area, then with a small pointing trowel smear it to all sides scraping mashing it into existing concrete to form bond. Depending on how wide and deep the hole is you might have to make two or three applications repeating the method each time. Should work.