Permeability is the hydraulic property of the porous material which is the measure of durability. Since water is the enemy of bituminous topped pavement because when rain water infiltrates and percolate through the pores, break down the bonding between bitumen and aggregate. Ultimately pavement fails before service life. It is well aware that bitumen mixture at different air voids content represents different permeability characteristics for the different composition of bitumen. In order to measure permeability of bituminous mixture, an instrument was fabricated which follows the Darcy’s falling head method. Permeameter is designed in such a way that it can consist of Marshall’s sample and tested in the lab. This equipment is capable to measure vertical as well as horizontal permeability. It was found that the horizontal and vertical permeability varied largely over the entire range of air voids content. However, relationship between horizontal and vertical permeability ratio and percent air voids was established. Four types of asphalt mixtures for different composition namely BC 20mm aggregates, BC stone dust as filler, BC cement as filler and SDBC was used in the lab test for estimation of permeability. However, Composition of bitumen varied over 4.5%-7.0% and percent of air voids varied over 2%-8% on the basis of laboratory investigation of various asphalt mixtures. Permeability increases with increase of void ratio and found ratio of vertical and horizontal permeability is 1.12.
