Hello, I am a landscape contractor who has been asked to re-do a bluestone walk that has failed. It buckled, and many of the stones are actually cracked. It is in NH, where the winters are long and cold. I thought maybe that the base wasn't done right, but we lifted a few stones, and found ~8" of gravel under 3"+ of stone dust. Do you think that the stone dust is holding too much water and didn't drain properly, and that's why the walk has failed? WHen we relay it, isn't it better to use masonry sand rather than stonedust? Thanks for your comments.