City of Winnipeg crews tore up the side walk in front of my building last year and poured a new sidewalk. Instead of sand, they used crushed limestone (1/4 inch down, which is mostly limestone dust) as a base. (Don't know how thick the bed of crushed limestone was.) But, one of the foremen I talked to said that crushed limestone was much better to pour concrete onto than sand because it packed down so much harder. (They used a gasoline engined "Wacker" machine to pack down the crushed limestone so that it was so hard you could walk on it without disturbing the limestone.) He said that you just couldn't do that with sand because sand grains are rounded and don't have sharp edges like particles of crushed limestone, so they just didn't stick together as well as crushed limestone.
Would it be better to use crushed limestone and rent a "Wacker" to pack it down real hard before pouring the concrete, or do they only use crushed limestone here because we have lots of limestone in Manitoba so it's cheap?