Imca, i have no experience in Limestone but do with Concrete. It has been my experience with the concrete when crushed down to 3/4 inch tends to accept moisture very easily. Once this moisture soak's in it starts to degrade the concrete.
After a good soaking rain you can see a yellow stream of water running away from the material.
After about two years in place you can definatly see the degregation. I also wonder about the downstream runoff. It can't be good for the environment. Just my opinion. Gramps.