It's my belief that the contractor is referring to limestone dust, not any type of crushed aggregate. Any one who's ever put a load of #53's down on the driveway knows how full of "fines" that particular grade of product is, and how well and how hard it packs after getting wet and settling. True limestone DUST acts almost like a crude cement in the fact that it will coagulate and clump together. Ask the guy who services the equipment and pumps at your local limestone quarry.
Having said that, and believing that I understand the reasoning behind such a procedure, I still have my doubts as to its effectiveness. Then again, I'm not sold on Bentonite's abilities to plug a leak either.
Southern Indiana....Limestone capital of the world....
