bitumen is a sticky, black and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product; it is a substance classed as a pitch, it is mainly classify as below different quality: 40-50, 60-70, 85-100, 120-150, 150-200, 200-300 etc. 60-70 quality bitumen which is suit for normal climate is the product produce by standard production line, there is less manufacturer who can produce 40/50 quality bitumen whose price is high than bitumen 60-70, 40-50 bitumen is mainly used under high temperature road; production quantity for bitumen 85-100 which is mainly used under low temperature is very small. 
.