The coarse aggregate may consist of gravel or crushed limestone. When gravel is used, it shall be graded uniformly from coarse to fine, meeting the following requirements: It shall all pass a two-inch mesh screen; twenty-five (25) percent must be retained on a one-inch screen and not more than ten (10) percent shall pass a quarter-inch screen. When crushed limestone is used, it shall be of the quality equal to a Tyrone or High Bridge variety. It must be crushed so that one hundred (100) percent will pass a 2½-inch screen, fifty (50) percent to seventy-five (75) percent to pass a 1¼-inch screen, and not more than five (5) percent to pass through a quarter-inch screen. It must be free from clay, soft or disintegrated stone or other foreign substance.