Dense Bituminous Macadam:

A Dense Bituminous Macadam (DBM) is a close-graded premix material having a voids content of 5-10 per cent. Two gradings are normally adopted :

Grading 1

Nominal size of aggregates 40 mm Layer thickness 80-100 mm Bitumen content 4.0 minimum

Grading 2

Nominal size of aggregates 25 mm Layer thickness 50-75 mm Bitumen content 4.5 minimum

The mix design is done by the Marshall method. The binder used is 60/70 penetration grade. Premixing is done in a hot-mix plant, and laying is done by a paver finisher. Rolling is done by 80-100 kN vibratory roller.