Effects of aggregate mineralogy and crusher type on the surface properties of hot mix asphalt

One of the most important properties of flexible pavements in terms of tire-pavement interface is surface texture. The texture of the pavement surface and it is ability to resist the polishing effect of traffic is of prime importance in providing skidding resistance. Pavement surface macrotexture greatly contributes to tire-pavement skid resistance which has a direct effect on traffic operation and safety particularly at high speeds. Doubtless, there exists a close relationship between the surface texture and the angularity characteristics of the aggregates within the pavement system.The study describes the evaluation of the angularity characteristics of the aggregates crushed with different types of crushers, and their impact on the surface properties of the pavements such as texture and surface friction. For this purpose, Limestone and Basalt aggregates were prepared using impact, jaw, and roll crushers. Following the determination of the angularity characteristics of the aggregate using ASTM C1252 and modified ASTM C1252, involving two different test methods (Methods A and B), and the EN 933-6. The asphalt slabs (65x65 cm) have been prepared and compacted at their optimum bitumen contents. Surface properties of the slabs have been studied using sand patch method and laser scanner. The frictional properties have been also determined by means of Dynamic Friction Tester (DFT). Finally, evaluations have been made to determine the relationship of aggregate angularity and the surface properties.