Pebbles, gravel, broken or crushed stone, of a kind commonly used for concrete aggregates, for road metalling, or for railway or other ballast; shingle and flint, whether or not heat-treated; macadam of slag, dross or similar industrial waste, whether or not incorporating the materials cited in the first part of the heading; tarred macadam; granules, chippings and powder, of stones of heading 2515 or 2516, whether or not heat-treated