Evolution of Asphalt Mixture Stiffness under Combined Effects of Damage, Aging, and Densification under Traffic

Abstract

The long-term evolution of asphalt mixture stiffness in the field represents a complex process in which three factors play an essential role: damage, aging, and densification under traffic. To take the factors into account adequately, not only must the level of each factor be known, but also how each level modifies the modulus of the asphalt mixture for the temperature and frequency range corresponding to field conditions. The research presented is based on experimental data from four flexible sections tested at the test track of the Centro de Estudios y Experimentación de Obras Públicas (CEDEX), in Spain. The stiffness of the asphalt layer was periodically evaluated with falling weight deflectometer back-calculation and with dynamic modulus testing in the laboratory. During a 28-month period, 1,323,600 loads were applied on the pavements. This loading caused a high level of deterioration in all sections and significant asphalt densification. The loading also provided time for some aging effects to develop. From the results of this full-scale test, different conclusions could be deduced concerning the evolution of damage, aging, and densification and how this evolution modifies the stiffness of the asphalt mixture. The effects of changes in the parameters of the original master curve have also been quantified. The model and methodology incorporated in the CalME design procedure were successfully used to reproduce the evolution of the asphalt layer modulus during the test. In particular, the assumptions of this model regarding how the dynamic modulus master curve was modified by each of the three factors were found to be valid for this experiment.

Utilización de técnicas petrográficas para evaluar los efectos inducidos del NaCl, condiciones climáticas extremas y el paso del tráfico en las superficies de las carreteras españolas

“…It was observed that the wheel tracking tests after thermal-stress decreased the deformability of the mixtures analyzed (Figure 3). This phenomenon could result from the possible aging of the binder after its exposure to high temperatures (54)(55)(56). In addition, petrographic analysis showed the surface loss of the binder (Figure 5c), causing a higher exposure of the aggregate surface to the effect of the NaCl solution and increasing the intensity of the cracking, in contrast to the lower amount of cracks detected after the freeze-thaw cycles.…”

Evaluation of Structural Response of Cracked Pavements at CEDEX Transport Research Center Test Track

“…2) was used for both mixtures, whose parameters were obtained with the Excel Solver utility. More details about this characterization are available elsewhere (6). Soils moduli were determined with backcalculation from FWD tests.…”

“…Once ω was determined, it was possible to determine the asphalt modulus for any combination of frequency and temperature by using Equation 3, which is part of the CalME asphalt damage models. Details about the application of the CalME model to CEDEX sections are available elsewhere (6,9).…”

Relationship between Backcalculated and Estimated Asphalt Concrete Dynamic Modulus with Respect to Falling Weight Deflectometer Load and Temperature

“…In a study performed at the CEDEX test track in Madrid, E Lab and E NDT were compared for four new pavement sections ( 11 ). A load frequency of 15 Hz was assumed based on the load duration of the KUAB FWD used in this study.…”

“…A load frequency of 15 Hz was assumed based on the load duration of the KUAB FWD used in this study. It was determined that the E NDT is roughly equivalent to E Lab determined by testing field cores ( 11 ).…”