Mechanistic Characteristics of Moisture Damaged Asphalt Matrix and Hot Mix Asphalt Mixtures

Abstract

The Hot mix asphalt (HMA) can be characterized as a combination of three phases: air voids, coarse aggregate, and asphalt matrix (AM), which includes binder and fine aggregate. The coarse aggregate phase is stiffer than the matrix phase, and is elastic in nature. The matrix phase makes the HMA a visco-elastic material due to the time dependent strain response of the binder. The matrix phase is considerably weaker than the coarse aggregate phase, and more susceptible to moisture damage. This study focuses on the characterization of the mechanistic responses of the AM and the HMA mixtures under dry and moisture damaged conditions. The mixtures were made using limestone aggregates and two asphalt type: neat and hydrated lime-modified. The dynamic shear rheometer was utilized to determine fatigue damage at 25°C and complex shear modulus (G*) of AM mixtures for a range of temperatures and loading frequencies. An indirect tensile load test was conducted to characterize tensile strength, fatigue life, elastic and permanent deformation characteristics of HMA mixtures. The G*-master curve analysis revealed that the hydrated lime-modified AM significantly improves the visco-elastic response of the moisture damaged AM. The fatigue life of AM mixtures increased due to the increase in G* values as a result of hydrated lime addition. Moreover, the fatigue life and permanent deformation characteristics of the HMA improved due to decreases in the rates of accumulation of tensile and compressive plastic deformation, respectively. Finally, relationships were established between various HMA and AM mechanistic properties.