Air Permeability of Asphalt Concrete Made with Shredded-Tire Rubber-Modified Binders and its Relationship with Porosity

Permeability of bituminous mixtures has been recognized as an important parameter that affects directly the performance and durability of materials. The permeability of bituminous mixtures and their durability are assumed to be more or less proportional to the porosity. Some researchers suggested that the permeability of bituminous mixtures is a better indicator of durability than the porosity, because permeability measures the capacity of the porous medium to transmit fluids, while porosity says nothing about their exposure to the forces producing disintegration. Ideally, a mix should contain disconnected voids. Dimensions of the individual voids and their lack of interconnection could produce a specimen whose void content is relatively high but of low permeability. A wearing course with low permeability will resist the ingress of air and water and hence will slow down the process of binder hardening due to oxidation and evaporation. This paper presents the relationship between the measured permeability values using the Leeds Air Permeameter and measured porosity values of asphalt concrete made with different binders.