  Crushed stone, for example, has a density of 100 pounds per cubic foot (lb/ft3), which is 1600 kilograms per cubic meter (kg/m3), which is 1.6 metric tons per cubic meter. Packed earth is about 95 lb/ft3, or 1520 kg/m3.
Harvard Business Review. Harvard Business Review. The Harvard Business Review (HBR) is a general management magazine published by Harvard Business Publishing, a wholly owned subsidiary of Harvard University. It is published 6 times a year and is headquartered in Brighton, Massachusetts.
RE: What is difference between SBR and NBR? Thanks. SBR is Styrene Butadiene Rubber, NBR is acryloNitrile Butadiene Rubber. Acrylonitrile is more polar than styrene, giving the NBR much better resistance to petroleum fluids and oils. SBR is a more general purpose rubber than NBR which is more expensive and used for applications where oil resistance is needed. Regards,