IRAN BITUMEN GRADE 60/70 Bitumen penetration grade 60/70 is semi-hard penetration grade bitumen using as paving grade bitumen suitable for road construction and repair also for the production of asphalt pavements with the below technical specification. This grade of bitumen is mainly used in the manufacture of hot mix asphalt for bases and wearing courses.Bitumen 60/70 is most used bitumen grade and basic material for all other bituminous products.