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.
The unit weight calculation is: Unit Weight = Weight of Concrete Ã· Volume of Concrete. This calculation can be rearranged for volume, which is known as the yield calculation. In other words, it is the volume that a certain weight of material will yield.rom the batch ticket, we find that 5 cubic yards of concrete were batched. The total weight of cement, sand, and stone was 18,860 pounds, and 156 gallons of water were also batched. Since we know that water weighs 8.33 pounds per gallon: 156 gallons of water X 8.33 pounds per gallon = 1,300 pounds of water.