01123083

Component

For urban source areas, porous asphalt functions to provide hydrologic restoration while functioning as a filtration interface when properly designed. The pore-based functionality of porous pavement systems, whether asphaltic or cementitious, is controlled in large part by the aggregate gradation; as well as the binder coating the aggregate and partially filling the pore structure. This study examined the role of aggregate granulometry on the pore-based hydraulic indices of porous asphalt, specifically permeability (hydraulic conductivity), void ratio and porosity. For the experiments of this study, 3 different groups of porous asphalt gradations comprised of 12 series of samples and separated based on gradation size indices have been examined. Two groups represent common mix designs in Italy while the third group represents micro-draining mixes which are less common. For all samples the vertical (kv) and horizontal (kh) permeability were measured with the commensurate total void contents (e) and total porosity (n). Marshall tests were performed in order to control the stability of the mixes. The directional permeability values were strongly correlated with kh as 0.6 times kv, a strong relationship between the permeability and the void content, and as the void content increases, the permeability also increases linearly. In a similar manner, the asphalt content influences the permeability and the porosity. For a given aggregate gradation, each increment of asphalt content causes a decrement in permeability and porosity. For the groups 1 and 2 a strong correlation were found between the coefficient of uniformity (U) and the vertical permeability as well as the total void content which was not the case for group 3. To keep a good predictive index for these group 3 cases another indicator of the aggregate gradation is introduced. This index is the P5•P2•Dmax for which the relationships with vertical permeability and the total void content were very consistent for the entire range of porous asphalt mixes (groups 1, 2 and 3). As for the vertical permeability good regression curves were found as well as for the total void content with this predictive index.

01120148

09-3473

English

19p

2009

Transportation Research Board 88th Annual Meeting

DVD

Figures; Photos; References (13) ; Tables (2)

Aggregate gradation; Aggregates; Asphalt mixtures; Design; Mix design; Permeability; Porosity; Porous materials

Coefficient of uniformity; Void content

Design; Highways; Materials; I31: Bituminous Binders and Materials

Transportation Research Board Annual Meeting 2009 Paper #09-3473

TRIS, TRB

Jan 30 2009 7:53PM