Experimental analysis of blistering and water bleeding on asphalt pavements

Asphalt pavement distress is generally attributed to traffic. However, blistering and water bleeding occur on surfaces with little or no traffic and can have consequences for life and safety. This study investigates air and water permeation that could trigger the two phenomena surveyed on a rehabilitated airport pavement. The components and formulation of the mix laid on the investigated runway were tested by varying the air voids content and thermal conditions. The coefficient of volumetric expansion of bitumen was measured between 25 degrees C and 80 degrees C. Its average value (i.e., 5.5 x10-4 degrees C-1) is 30 times higher than that of aggregates, and it thus can contribute to the reduction in saturated hydraulic conductivity when solar radiation increases the temperature of the wearing layer. Cold-hot-cold gravity filtration tests demonstrated that the logarithm of the hydraulic conductivity varies linearly with the air voids content at room temperature (i.e., from 1.57 x10-5 m/s to 3.23 x10-10 m/s with 10% to 5% residual voids) and decreases by about 50% when the surface temperature is varied from 20 degrees C to 65 degrees C; however, this process is sometimes not fully reversible. With regard to water bleeding, the evaporation rate (1.57 x10-7 m/s) according to the weighted evaporation method indicates high water permeability and air voids content on the studied wearing layer. The results confirm that variations in asphalt temperature and air voids content control flexible pavements' mechanical and physical properties so that local variations in water permeability can explain blistering and water bleeding. Further studies will investigate the relationships between asphalt's physical, mechanical, and volumetric properties that affect water and air flow into the pavement.