Identifying and correcting rut-susceptible asphalt mixtures

TLDR: In this paper, a field evaluation of Texas highway pavements was conducted to provide evidence that sand-size aggregate particles have a significant influence on rutting, and the aggregate's role in the permanent deformation behavior of the mixture was assessed by means of a novel parameter termed "p" value.

Abstract: A field evaluation of Texas highway pavements was conducted to provide evidence that sand-size aggregate particles have a significant influence on rutting. A laboratory investigation was performed 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 while other aggregates and the total gradation remain unchanged, (2) evaluate the ability of certain test procedures to differentiate between rut-susceptible and rut-resistant mixtures, (3) develop a new rutting model for predicting pavement performance which incorporates characteristics of the aggregate, and (4) examine fractal dimension analysis as a method of quantifying aggregate angularity and surface texture. Octahedral shear stress theory was employed to compare the rutting potential of asphalt concrete mixes containing low quality sand-size particles (rounded, smooth, non-absorptive) and high quality sand-size particles (rough, angular, absorptive). Five mixtures with varying amounts of the different aggregates were tested. A state-of-the-art theoretical approach was developed in which hyperbolic equations are introduced to model the compressive creep and recovery compliances. The new compliance equations are further developed into a rutting prediction model. The aggregate's role in the permanent deformation behavior of the mixture is assessed by means of a novel parameter termed "p" value. A new technique, known as fractal dimension analysis, offers a great deal of potential in providing a direct quantitative measure of aggregate angularity and surface texture which has heretofore been impossible. A combination of the new theoretical approach, the long-term laboratory 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.