Air voids characterisation and permeability of porous asphalt gradations used in different countries

Abstract

This paper presents the evaluation made on the properties of porous asphalt mixtures practiced in different countries. In order to fully understand the properties of porous asphalt mixtures, investigation should be conducted from different perspectives. Therefore this study was carried out to investigate the air voids properties and functional performance of porous asphalt simultaneously. An image analysis technique was conducted to analyse the air void properties within the gyratory compacted samples captured using a non-destructive scanning technique of X-ray Computed Tomography (CT). The results were then compared to the functional performance in terms of permeability. Four aggregate gradations of porous asphalt used in different countries i.e. Malaysia, Australia, Singapore and the United States were adopted for comparison. From the analysis, Australian mixture was found with the most homogeneous air voids distribution throughout the sample compared to other mixtures. The air void properties investigated have successfully described the air voids formation within the mixtures which reflects the result of permeability. This shows that air voids distribution within the sample plays an important role in determining the effectiveness of water transmission.