Gravel 3/4 (10mm to 20mm) The basic size for structural concrete mixes, pre-stress or pre-cast concrete products and asphalt concrete mixes. Gravel G1 (20mm to 40mm) Used in Concrete pavements, massive foundations, granular bedding/filler, and for asphalt concrete mix with coarser design specifications. Gravel 3/8 (6mm to 10mm) Used in high-strength concrete mixes, usually for densely reinforced structures, pre-stress/pre-cast products and for asphalt wearing and surface courses. Sand S1 (0 to 6mm) Fine aggregates from crushed rocks used as structural bedding, pavement seal coat, fairways sand cap and a very vital ingredient in all concrete and asphalt mixes.