How Thick Is the Ballast?
10mm ballast is a mixture of 10mm gritstone and grit sand. It is used for mixing concrete in small amounts where a finer mix is required. The size range of grains in 10mm ballast is similar to that of 5/8" and 7/16". However, due to its coarse texture, this type of ballast does not become embedded in the concrete as easily as finegrained ballast.