Influence of sand-sized aggregate particles on permanent deformation in asphalt concrete pavements

Abstract

The presence of sand-sized aggregate particles play a very important role in the rutting performance of asphalt concrete pavements. The influence that these particles have on permanent deformation is investigated in this research study. A comprehensive field evaluation is presented to prove that physical characteristics of sand-size aggregate particles have a strong influence on rutting. A detailed laboratory investigation is carried out in order to (1) quantify the influence on resistance to rutting when rounded, smooth, sand-sized aggregate particles are replaced by rough, angular, porous particles, and (2) evaluate the ability of test procedures to identify good rutting resistant mixtures, based on the quality of the sand-sized particles. A state of the art theoretical approach is described and developed. In this approach, hyperbolic equations are introduced to model the compressive creep and recovery compliances, and the aggregate's role in the permanent deformation behavior of the mixture is assessed by means of a new parameter: the "p" value. The new compliance equations are further developed into a rutting prediction model. A new technique based on image processing is applied to the characterization of texture in sand-sized aggregate particles. The technique is known as fractal analysis. Octahedral shear stress theory is used to evaluate potential to rutting of asphalt concrete mixes containing low quality sand-sized particles (rounded, smooth, non-porous) and high quality sand-sized particles (rough, angular, porous). A combination of the new theoretical approach, the laboratory long-term performance of the mix, and the octahedral shear stress analysis, is recommended as the preferred approach to evaluate the influence of sand-sized aggregate particles on permanent deformation in asphalt concrete mixtures.