Dynamics of water evaporation from porous asphalt

Abstract

Abstract The dynamics of water evaporation\xa0from\xa0porous asphalt\xa0mixture, with\xa0porosity\xa0ranging from 15% to 29%,\xa0have been investigated in this article. In order to test the same samples under different conditions, the pore structure of asphalt was\xa0quantified\xa0using\xa0X-ray\xa0Computed\xa0Tomography (CT) scans and\xa03D\xa0printed\xa0in transparent resin blocks.\xa03D\xa0printed transparent resin samples were tested under\xa0controlled laboratory conditions\xa0to understand the effect of\xa0pore space\xa0topology\xa0on the water\xa0retention\xa0and drying dynamics.\xa0The\xa0macroporosity, pore size distribution,\xa0air void tortuosity,\xa0water conductivity,\xa0and\xa0water retention curves\xa0of the 3D printed porous asphalt samples\xa0were\xa0quantified\xa0by means of\xa0image analysis. Moreover, a model was\xa0developed and\xa0tested experimentally to estimate\xa0the evaporation rates\xa0from porous asphalt materials\xa0under a wide range of\xa0porosities.\xa0Within\xa0the range of asphalt mixtures studied\xa0in the present work,\xa0the\xa0evaporation rate\xa0is related predominantly to\xa0the\xa0porosity, pore size distribution and tortuosity.\xa0It\xa0was\xa0found that\xa0the period over which\xa0water\xa0evaporation\xa0occurs\xa0at the surface is relatively short during drying of porous\xa0asphalt materials\xa0due to their relatively large pores weakening the capillary forces.\xa0This\xa0results in significantly shortening the so-called stage-1 evaporation (when the drying rate is controlled by liquid vaporisation at the surface) and early onset of the transition period (when both surface water evaporation and vapour diffusion inside porous asphalt play\xa0a\xa0comparable role in supplying the evaporative demand). The transition period is followed by the stage-2 evaporation when the process is limited by the vapour diffusion inside the porous asphalt. Our results\xa0illustrate that\xa0the\xa0beginning of the\xa0stage-2\xa0evaporation\xa0depends\xa0on the porosity and tortuosity of\xa0the\xa0porous asphalt material\xa0among other parameters.\xa0Our results and analysis provide new insights\xa0into\xa0the dynamics of water evaporation from asphalt materials.