Evaluation of the degradation of aggregates shape properties

ABSTRACT The aggregates shape properties (form, angularity, and surface texture) have an influence on the asphalt pavement surface texture, which is directly related to tire-pavement adhesion, to stability and to road safety. Due to the importance of studying these characteristics, this research has the main objective of evaluating the effect of aggregate degradation on their shape properties. In order to achieve this, the shape properties of aggregates with three different sizes were analyzed by means of traditional methods and also with the use of aDigital Image Processing (DIP) technique. These properties were analyzed with the use of the Aggregate Image Measurement System 2 (AIMS2), before and after the use of the Micro Deval (MD) and the Los Angeles abrasion equipment, besides the conventional test of uncompacted void content. The aggregates particles angularity values decreased during the degradation process for both equipment used in the analyses. The aggregates sphericity after the use of MD did not change significantly. This could be explained because smaller abrasive charges are used in this particular test. The surface texture evaluated after the Los Angeles abrasion test did not vary significantly, which can be explained due to the tendency of breakage during the test, a process that is more related changes in form conditions. Furthermore, the results showed that the aggregate size and the presence of water influenced the degradation processes of the aggregates. The combination of the characterization of aggregate shape properties by means of image techniques with the use of laboratorial mechanical processes that are capable of modifying these properties might be an adequate solution for the prediction of asphalt pavements performance in relation to adhesion loss throughout the time.