The effect of rainfall on asphalt surfacing materials

This paper reports the findings of a laboratory investigation to determine the effect of rain on the 3-d drainage characteristics of asphalt surfacing mixes. A rainfall simulator was developed to apply differing rainfall intensities and surface flow assessed at different crossfall slopes. Different stages in the development of surface flow during simulated rainfall were evaluated for 5 different types of surface. A model was developed to related rainfall intensity, crossfall and texture depth with Time of Transition Flow. This is the duration into a rainfall event at which road surface texture has filled with water and surface runoff starts. The findings illustrate that surface runoff characteristics can be evaluated in the laboratory prior to full-scale road trials.