Has anyone had experience with the concrete-lifting technology "Uretek"? It is a deep-injected polymer that is lightweight and fills in gaps in foundations and lifts fallen porches, driveways, etc. back to level. My porch has pulled away from our house and sunk slightly due to clay soil compaction. We got an estimate from a company that uses Uretek (for $2,600). Our biggest fear is that it won't last. (We tried mudjacking 5 years ago but it the porch sunk back.) Another contractor recommends "rip and replace" over any 'liquid-lifting' methods, but this could cost twice as much. Thanks,