Causes of Common Mechanical Defects of Durable Road Markings in Urban Roads

In recent years, durable traffic road markings including hydrocarbon resins based on hot melt thermoplastics, and cold plastic paints based on 2K acrylics have been widely used in urban roads (particularly in Tehran).Durable road markings, in spite of high thickness, appropriate durability in comparison to solvent based cold plastics, and widespread application worldwide, suffer from three main mechanical failures during their service life, especially in the first year after a freeze thaw cycle, in which have given rise to doubts toward replacing these coatings with lower durable traffic paints (i.e. solvent and water based paints).The main failures are paint cracking, delamination of road markings from the surface, and asphalt degradation next to or under the markings. The main causes would be various forms of stresses (i.e. mechanical stress, internal stress, and weathering stress), insufficient adhesion of road markings to asphalt, and failing in cohesive strength of asphalt, respectively. The failures can have different causes, for example problems in paint formulation (e.g. incorrect filler content or wrong choice of resin), improper application of paint or even substrate conditions. In this article, each failure modes specific to durable road markings, will be discussed from scientific views and the rolls of internal and external stress as well as adhesion, and cohesion strength of paint and substrate will be explained. Future more, some remedies to prevent the failures will be suggested.