Color durability of pigmented slurry surfacing after artificial aging tests simulating weathering and traffic

In the new vision of complete street, the use of colored pavements has been promoted in recent years to improve road user safety and to enhance the reorganization and aesthetic of the urban environment. But, besides several benefits these pavements undergo environmentally and traffic induced changes in appearance, faster than the traditional ones, a few months after installation. Thus, the laboratory-scale investigation analyzed the color durability of pigmented slurry seals, which were prepared using a clear synthetic emulsion and mineral pigments, subject to different artificial accelerated aging procedures. They simulated the exposition to sunlight at high temperature (QUV weathering tester), the aggression of chemical products (salt brine bath) used for winter maintenance operations and the dynamic actions of vehicle tires (loaded wheel tester). The analyses of color change measured with a spectrophotometer highlighted the extreme sensitivity of pigmented thin surfacing to physical and mechanical stresses. Specifically, the thermal and photo-oxidation of the binder film induced by the UV exposure at high temperature and its wear caused by the dynamic passage of rubber tire produced a large supra-threshold color difference on the samples' surface. These results suggest how a correct mix-design, both in the materials choice and ingredients dosage, should be properly calibrated on the basis of the pavement end-use and of the prevailing climatic conditions to ensure color consistency throughout the pavement lifetime.