A CONTRIBUTION TO THE PROBLEM OF TRACKING GROOVES IN ASPHALT

From long-term field observations on sections of road in Switzerland and on laboratory tests, upper limiting values could be determined for binder content of mineral aggregates for bituminous pavements, beyond which the formation of wheel grooves in the surface are unacceptably large for the given boundary conditions. Lower limiting values of the voids content are given as 3 to 3.5%, upper limiting values of the degree of void filling at 75 to 80%. The voids content can be increased by sand-rich mixes. With the use of mixes having a low binder content or large void contents, attention should be given to the likelihood of damage due for example to fatigue behaviour or water-permeability. Until the material types summarized according to the results of the investigations prove themselves further and guarantee a sufficiently long life, periodic repair by filling the tracking grooves or replacement of the wearing course is recommended as a more economical solution for repair, instead of reconstructing the lower courses. (TRRL)