Long-term behavior of the micro-texture of aggregates used on roads subjected to extreme climate conditions and winter maintenance operations

Abstract

The micro-texture of fine and coarse aggregates used on roads is one of the main factors responsible for the skid resistance of asphalt pavements. However, the long-term behavior of this property regarding the effects of traffic and climate conditions has been poorly studied. Therefore, in this paper, two types of aggregates, schist and amphibolite, commonly used on roads that are subjected to winter maintenance actions and high temperatures in summer have been studied. The micro-texture of the aggregates has been characterized with an optical roughness tester, fluorescence microscopy and the Polished Stone Value test. The extreme climate conditions have been simulated in a laboratory with durability tests (freeze-thawing and thermal stress cycles) including the NaCl used as deicer during winter maintenance operations. Results have shown that the wearing mechanisms of the aggregates’ surfaces are different regarding their composition and internal texture. On schist aggregates, weather conditions applied do not significantly deteriorate their micro-texture. However, the combined effect of traffic and extreme climate conditions with NaCl, double the decrease of the surface roughness measured when these aggregates are subjected to extreme climate conditions in the laboratory, improving, in some cases, their skid resistance. Conversely, the external factors considered have the same effect on the micro-texture of the analyzed amphibolite aggregate.