0 0 0 2517 Pebbles, gravel, broken or crushed stone, for concrete aggregates, for road metalling or for railway 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 and 2516, whether or not heat-treated