Political boundaries are often formed by physical boundaries. An example of this is the Rio Grande River that separates the US from Mexico. An ethnographic boundary or a cultural boundary is a boundary line that runs along differences in ethnicity.
Steel has a density of about 490 pounds per cubic foot, which is more than three times the density of concrete, so the generally accepted density of normally reinforced concrete is 150 pounds per cubic foot which results in a cubic yard weighing 4050 pounds, but this depends on the quantity and grade of the rebar used.
How many cubic feet of concrete are in 1 ton US (short)? The answer is: The change of 1 sh tn (ton US (short)) unit of concrete measure equals = to 13.31 cu ft-ft3 (cubic foot) as the equivalent measure for the same concrete type.