Effects of crack width and permeability on moisture-induced damage of pavements

The purpose of this study was to evaluate the pavement distress associated with moisture and cracks. A feedback-controlled test was developed to generate a crack with a controlled width in asphalt concrete specimens. Three different mixtures, i.e., dense graded, stone mastic asphalt (SMA), and porous asphalt (PA), were tested for moisture-induced damage aggravated by cracking and high void contents. An exponential relationship was found to exist between permeability and air voids. The intrusion of water can be greatly reduced when the asphalt mixture is properly compacted to an air void level of 7% or less. As water penetrated into the mixtures, PA and SMA coated by a thicker asphalt film showed more resistance to water damage than the dense mixture by a thinner one. The test results indicated that voids in these three types of mixtures could be categorized as impervious, semieffective, and effective, respectively. The corresponding permeability was found to be 10(-2) cm/s or higher, 10(-2) to 10(-4) cm/s,and 10(-4) cm/s or lower, respectively. When cracks became wider than 0.2 cm, the indirect tensile strength of all three mixtures reduced significantly in the presence of water. The effect of cracks on a pavement was similar to an increase in voids in a mixture regarding water damage. A pavement showing 0.2 cm cracking is recommended to have immediate maintenance. The present research may provide insight into establishing criteria for a durable asphalt pavement.