Im doing some gravel borders on my drive which im flagging in a row of block pavers. Firstly ive dug for a 75mm thickness of concrete, is that enough bearing im mind its not trafficed over. I was thinking of using up some building sand i have in the concrete and thought 3ballast 1building sand 1 cement? . The ballast is mostly shsrp sand and 20mm stone. At least that would get rid of some of my building sand
