Lack of mechanistic foundation and poor correlations with field performance of conventional laboratory-based tests has accelerated the search for a mechanistic-based approach for screening of asphalt mixes for moisture-induced damages. According to recent studies, surface free energy (SFE) method can be used to mechanistically quantify bond strength and debonding of binder-aggregate system in presence of water. This study was undertaken to evaluate the effects of different additives, namely warm mix asphalt (WMA) additive (amine-derived), amine-based anti-stripping agent (ASA), polyphosphoric acid (PPA) and reclaimed asphalt pavement (RAP) on the moisture-induced damage performance of asphalt mixes through the use of laboratory-based performance tests and SFE method. For this purpose, different energy parameters were determined from SFE components of binder blends and aggregate. Asphalt mixes with different additives were produced to evaluate moisture-induced damage using indirect tensile strength (ITS) and Illinois semi-circular bend (IL-SCB) tests. A new parameter, known as fracture energy ratio (G_f ratio) obtained from IL-SCB test, was used to correlate fracture energy with moisture-induced damage potential of mixes. Also, the effect of short-term and long-term aging on the moisture-induced performance of asphalt mixes were evaluated. Furthermore, correlations between moisture-induced damage parameters from laboratory-based performance tests and SFE method were investigated.

The current study was undertaken to evaluate the effect of Polyphosphoic Acid (PPA) on rheological properties of different grades of asphalt binders containing a chemical Warm-Mix Asphalt (WMA) additive in presence and absence of a liquid Anti-Stripping Agent (ASA). Also, the effect of chemical WMA additive, PPA and ASA on rutting and moisture-induced damage potential of asphalt mixes was evaluated. Polymer-modified and non-modified asphalt binders were blended with different amounts of PPA, WMA additive, and ASA and tested in a Dynamic Shear Rheometer and a Bending Beam Rheometer. The results indicated that blending WMA additive and PPA with all tested binders increased their rutting and fatigue resistance. However, blending PPA with asphalt binders in presence of the WMA additive and ASA was found to reduce their resistance to fatigue cracking. Also, the use of WMA additive, ASA and PPA was found to reduce the effectiveness of the PPA in bumping the high-temperature Performance Grade (PG) of asphalt binder with an insignificant effect on low-temperature PG. Furthermore, conducting Hamburg wheel tracking and indirect tensile strength ratio tests on asphalt mixes containing WMA additive, PPA and ASA showed a low susceptibility to rutting with no significant indication of moisture-induced damage.

Different technologies, namely foamed asphalt, synthetic waxes, zeolites, and chemical additives, are used to produce warm mix asphalt (WMA). This study was undertaken to evaluate the effect of using different amounts of an amine-based chemical WMA additive on the rheology, performance grade (PG), and moisture-induced damage potential of an asphalt binder (PG 58-28). Superpave specifications were used to evaluate the rheological properties and PG of the asphalt binder. Also, a mechanistic approach-based on the surface free energy (SFE) method was used to evaluate the moisture-induced damage potential of the asphalt binder combined with commonly used aggregates in an asphalt mix. It was found that the dynamic viscosity of the asphalt binder was not significantly affected after blending it with the WMA additive. It was also observed that the Superpave high-temperature PG and the rutting factor did not reduce by an increase in the WMA additive content. However, the continuous low-temperature PG of the asphalt binder decreased with an increase in the amount of WMA additive. Furthermore, it was found that the fatigue resistance increased after blending the binder with the WMA additive. The SFE results of the asphalt binder revealed that the WMA additive used in this study reduced the moisture-induced damage potential of the asphalt mixes. However, the extent of this improvement was found to largely depend on the aggregate type. The outcomes of this study are expected to help better understand the influence of amine-based chemical WMA additives on rheological and long-term performance of asphalt mix.

Over the last decade, modifying asphalt binders with polymers and Polyphosphoric Acid (PPA) has become an essential part of the asphalt industry. There is a need to study the effect of polymer and PPA on asphalt binders’ compositions and mechanical properties. Changes in the rheological properties of modified binders due to oxidative aging are another important concern for pavement engineers. Although significant efforts have been made to characterize the rheological properties of modified asphalt binders in the past, the influence of molecular structure on these properties is still unknown. In the present study, three different types of asphalt binders, namely unmodified, polymer-modified, and PPA-modified, were tested. The Dynamic Shear Rheometer and Rotational Viscosity test results indicate an increase in stiffness and viscosity due to polymer and PPA modifications. Aging was also found to increase the binder’s stiffness and viscosity, irrespective of the binder type. The effect of the molecular structure on the asphalt binder’s properties was investigated by the X-ray Diffraction (XRD) technique. The aromaticity and crystallite parameters for unaged, short-term aged, and long-term aged binders were determined from the XRD spectra. The XRD analysis was able to detect the change in molecular structure because of aging, but no specific trend for the change in crystallite parameters was observed. The aromaticity and crystallite parameters were found to increase with polymer modification and decrease with PPA modification when compared to the unmodified binder. It was also found that asphalt binder loses its aromatic characteristic upon the addition of PPA.