Seriously, it's just something that someone, somewhere, pointed out.. that limestone is used to make cement, mortar, and that if it was poured into a form, allowed to harden, then "finished", after a couple thousand years, you wouldn't be able to readily distinguish it from "regular" limestone..
I don't know if it's true, but it sure sounds like it would be plausible..
It would sure make transport easier..
Mix it on site, pour it into a large form, let it set..
No carrying large 11 ton block up to the next tier, and all the manpower, danger involved..
Who knows?
re: Your theory about forming the limestone blocks of the pyramid - I guess it's posssible. One very easy way to prove/verify the theory would be the discovery of artifacts contemporary with the construction of the pyramids INSIDE one of the blocks. If they indeed formed the blocks, it would be impossible to completely prevent contamination of the mix with tools, scraps of wood, cloth, food, etc.