Evaluation of criteria for selection of materials for surface treatments based on performance

Abstract

Surface treatments are often used in Brazilian pavements. Among those, chip seals (CS) are commonly used in the Low Volume Roads (LVR) in the Northeast Region. This Master’s Thesis aims to propose criteria for selection of aggregates and binders for CS Coats aiming to achieve best performance regarding functional problems such as aggregate loss and bleeding For this purpose, this research was s ubdivided into three parts that were organized in paper format . In the first paper , changes that occur during service life in features of the asphalt emulsions used in CS treatments were evaluated. In this regard, two methods of laboratory aging were evaluated: ultraviolet (UV) and Pressure aging vessel (PAV). In this first paper , rheological parameters of emulsion residue were analyzed, as well as the ir relat ion to the performance of coats It was observed that the effects of UV aging are different from th ose found in PAV, depending on the material. It was also observed that these effects reflect in implications in the performance of coats. The second paper addresses the binder aggregate bond and the phenomena of adhesiveness and cohesiveness. The aged resi dues of emulsion were tested with the Bitumen Bond Strength (BBS), adherence test recommended for asphalt binders. The adherence of these materials to the aggregate after aging was then observed. It was noticed that aged binders tend to present higher Pull off tensile due to the effects of UV and PAV in adhesiveness/cohesiveness, and in moisture damage. The third p aper focused on aggregate loss as it is the major failure factor in CS, considering pavements in the state of Ceara. Aggregate shape and uniformity were defined as the parameters and their influence on performance was evaluated from the perspective of aggregate loss distress . For this purpose, aggregates with variations in these parameters were selected and samples of s pecimen were constructed in laboratory and tested by using the Wet Track Abrasion Test (WTAT). It was observed that the organization of the particles of aggregate on the surface of the coat, summed to both high uniformity and low flatness/elongation, is re levant to the acquisition of better performance concerning aggregate loss. In this research , it is possible to conclude that properties found in the aggregates and in the asphalt binders might present effects on the performance of CS pavements. In relation to the binder these properties also might present notorious variation during service life due to aging. Based on that, it is relevant to consider these effects in projects, as well as techniques to avoid the loss of quality of the materials during servic e life.