01661059

Component

For non-absorbing medium, it is easy to find vapor permeability using Darcy’s law. However, asphalt concrete (AC) sample absorbs moisture over time if it is exposed to humid environment which causes swelling of the binder materials. This action reduces the pore connectivity. As such, the flow properties of AC exposed to moisture can change with time due to clogging of capillary pores and reduced pore connectivity by swelling. To this end, this study develops a model by modifying the Darcy’s law to quantify vapor permeability of an AC sample. The resulting model considers asphalt’s swelling using air voids and sample thickness (represents flow length) in addition to regular parameters of a Darcy’s law. As a first step, the effects of air voids and thickness on vapor flow are evaluated. It is shown that vapor flow increases with an increase in air voids and with a decrease in thickness. Vapor flow shows a logarithmic correlation with time. As a second step, a permeability model is developed considering time dependent vapor flow rate in Darcy’s law. Next, the model is validated using laboratory tested data. The model is found to have good agreements with the tested data. The developed model is advantageous over simpler Darcy’s model for determining asphalt permeability considering binder swelling, pore connectivity and clogging.

This paper was sponsored by TRB committee AFK40 Standing Committee on Surface Requirements of Asphalt Mixtures.

18-04541

English

6p

2018

Transportation Research Board 97th Annual Meeting

Digital/other

Figures; References; Tables

Air voids; Asphalt concrete; Darcy's law; Gas permeability (Concrete); Mathematical models

Construction; Highways; Materials; Pavements

Transportation Research Board Annual Meeting 2018 Paper #18-04541

TRIS, TRB, ATRI

Jan 8 2018 11:06AM