Predictive Framework for Modeling Changes in Asphalt Mixture Moduli with Oxidative Aging

This paper presents a predictive framework for asphalt mixture moduli as a function of aging time with two levels of sophistication. This work is built on the method currently implemented in Pavement mechanistic-empirical (ME) that uses an effective time/frequency concept based on time-aging superposition to model the effect of aging on a mixture’s modulus. Time-aging superposition implies that an asphalt mixture’s modulus mastercurves, corresponding to different aging levels, coincide when they are shifted horizontally on the log-frequency axis. This study improves the accuracy of the existing model by decoupling the time-temperature and time-aging shifts. The new framework also uses the binder dynamic shear modulus | G*| as an aging index instead of the viscosity, which is used in Pavement ME. The | G*| aging index is used to calculate an effective frequency at short-term aging (STA), which is then used in the asphalt mixture sigmoidal model to calculate the corresponding asphalt mixture modulus with aging. The pavement aging model introduced by NCHRP 09-54 predicts log | G*| at 64°C and 10 rad/s for a specific field-aged condition and pavement depth. The proposed framework can use the predicted log | G*| to predict the mixture’s corresponding dynamic modulus (| E*|) at that aging level and pavement depth. Level 1 of this framework requires characterizing the | G*| at STA and calibrating the NCHRP 09-54 pavement aging model as well as measuring the mixture | E*| at STA. Level 2 does not require any binder testing, providing relatively less accurate predictions but relieving some testing requirements.

Experimental Study on Asphalt Composite UV Absorption Anti-Aging Agent

In order to compound high performance asphalt UV absorption anti-aging agent, light screener, antioxidant, light stabilizer were used in experiment, ultraviolet rays aging equation of asphalt was established, was used to stand for final aging quantity of asphalt pavement, aging equation and were used to research the performance of UV absorption anti-aging agent in different compound mode, optimum composite system of asphalt composite UV absorption anti-aging agent was found, and compliance dosage of components in optimum composite system was research after then. The results of the study show that: The aging law of asphalt ultraviolet radiation aging follows the equation next, ; asphalt UV absorption anti-aging agent composed by 5% antioxidant and 1.5% light stabilizer have the best anti-aging performance to UV radiation.

Asphalt Pavement Aging and Temperature Dependent Properties through a Functionally Graded Viscoelastic Model, Part-II: Applications

This is the second article in a series of two papers describing simulation of functionally graded viscoelastic properties in asphalt concrete pavements. The techniques developed are applicable to other viscoelastic material systems with continuous, spatial grading of material properties. A full-depth asphalt concrete pavement has been simulated to demonstrate the applicability and importance of the graded viscoelastic analysis method. Based on the graded finite elements developed by Kim and Paulino[1], Buttlar et al. [2] used graded finite elements to determine typical responses to tire loading for an aged asphalt concrete pavement. In the current study, a similar pavement section is studied using the viscoelastic graded analysis (rather than elastic). Graded, layered and homogeneous material variations were used for a series of simulations, and the results from different approaches were compared.

Verification and Improvement of the Rate of Asphalt Aging Simulated by AASHTO PP1–98 Protocol

It is well documented that environmental effects play a significant role in characterizing material properties, which in turn affect pavement performance. Studies under the Strategic Highway Research Program (SHRP) were carried out on the age-hardening characteristics of asphalt binders and mixes. As a result, laboratory procedures to simulate the field hardening of asphalt binders and mixes, AASHTO Provisional Protocols PP1–98 and PP2–99, were developed. The approaches followed in these procedures are of great value for the ongoing research on pavement aging; however, due to limited resources and time constraints under the SHRP program, these provisional procedures have certain limitations. A research study, NCHRP Project 9–23, was initiated to overcome these limitations and enhance the predictive capabilities of these protocols. The current research paper is a part of NCHRP 9–23, which deals with the PP1–98 protocol. Binders and field cores were obtained from long-term pavement performance and other sites across the United States. Original, laboratory-aged, and field-aged binders were characterized through dynamic shear rheometer testing. The existing protocol was verified; on the basis of the findings, the protocol was improved to include the effect of field aging conditions and mix properties. The developed model was calibrated and validated with field data. Parametric analysis was performed on the final model to ascertain the practicality of the output. On the basis of those findings, a recommended provisional protocol was developed. The recommendations apply only for conventional, nonmodified binders.

Modeling of Oxidative Aging Behavior of Asphalts from Short-Term, High-Temperature Data as a Step toward Prediction of Pavement Aging

The oxidative aging data collected during the Strategic Highway Research Program have been analyzed in terms of kinetics of viscosity change with time and temperature. Changes in viscosity have been used as the measure of the progress of aging. The objective is to model viscosity increases accurately enough to be able to predict aging (in terms of viscosity changes) at pavement temperatures from short-term test data acquired at high temperature. This involved constituting a mathematical model, based on oxidative reactions, and a nonlinear regression of the data to test predictability of the proposed model. Clearly, there is a point beyond which viscosity change becomes independent of time, but no data were collected to that extent. Separately, it has been shown that oxidation of aliphatic sulfide to sulfoxide and oxidation of benzylic carbon to carbonyl are the principal chemical reactions that contribute to an increase in viscosity. The data fit the proposed equation sufficiently well to allow calculation of rate constants of viscosity increases for both reactions, and, hence, allow development of an Arrhenius temperature relationship. Finally, it is hoped that the proposed equation will provide reasonable estimates of rates of oxidative aging of asphalts at pavement temperatures from short-term, high-temperature oxidative aging data measured in a laboratory.