Identification and assessment of the dominant aggregate size range of asphalt mixture.

摘要

The importance of aggregate structure on asphalt mixture performance has been well established on the basis of experience and is well documented in the literature. Furthermore, coarse aggregate structure is most important for resistance to rutting, and recent work has shown that it can also play a significant role in resistance to damage and fracture. Therefore, large enough aggregates should engage dominantly in the structure for good mixture performance. This study focused on the development of a conceptual and theoretical approach to evaluate coarse aggregate structure based on gradation.; According to a well-known fact in soil mechanics, the porosity of an assemblage of granular particles (e.g., the aggregate within an asphalt mixture) must be no greater than 50% for the particles to be in contact with each other. This also implies that one can use porosity as a criterion to assure contact between large enough particles within the mixture to provide suitable resistance to deformation and fracture.; A theoretical analysis procedure was developed to calculate the center to center spacing between specific size particles within a compacted assemblage of particles of known gradation. Thus, the 70/30 proportion can be used to determine whether particles on contiguous Superpave sieves can form an interactive network of particles in continuous contact with each other. The range of particle sizes determined to be interactive was referred to as the dominant aggregate size range (DASR) and its porosity must be no more than 50% for the particles to be in contact with each other.; It was concluded through the extensive analysis with existing database and lab tests that porosity of the DASR may provide a good criterion for determining the suitability of gradation for dense-graded asphalt mixture. The approach should be further developed and evaluated for use in mixture design and analysis.