Most paved roads in the United States are surfaced with asphalt. These asphalt pavements suffer from fatigue cracking and thermal cracking, aggravated by the oxidation and hardening of asphalt. This negative impact of asphalt oxidation on pavement performance has not been considered adequately in pavement design. Part of the reason is that the process of asphalt oxidation in pavement is not well understood.
This work focused on understanding the asphalt oxidation kinetics and on developing pavement oxidation model that predicts asphalt oxidation and hardening in pavement under environmental conditions.
A number of asphalts were studied in laboratory condition. Based on kinetics data, a fast-rate ? constant-rate asphalt oxidation kinetics model was developed to describe the early nonlinear fast-rate aging period and the later constant-rate period of asphalt oxidation. Furthermore, reaction kinetics parameters for the fast-rate and constant-rate reactions were empirically correlated, leading to a simplified model. And the experimental effort and time to obtain these kinetics parameters were significantly reduced. Furthermore, to investigate the mechanism of asphalt oxidation, two
antioxidants were studied on their effectiveness. Asphalt oxidation was not significantly affected. It was found that evaluation of antioxidant effectiveness based on viscosity only is not reliable.
The asphalt oxidation kinetics model was incorporated into the pavement oxidation model that predicts asphalt oxidation in pavement. The pavement oxidation model mimics the oxidation process of asphalt in real mixture at pavement temperatures. A new parameter, diffusion depth, defined the oxygen diffusion region in the mastic. A field calibration factor accounted for the factors not considered in the model such as the effect of small aggregate particles on oxygen diffusion. Carbonyl area and viscosity of binders recovered from field cores of three pavements in Texas were measured and were used for model calibration and validation. Results demonstrated that the proposed model estimates carbonyl growth over time in pavement, layer-by-layer, quite well.
Finally, this work can be useful for incorporating asphalt oxidation into a pavement design method that can predict pavement performance with time and for making strategic decisions such as optimal time for maintenance treatments.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2012-05-10940 |
| Date | 2012 May 1900 |
| Creators | Jin, Xin |
| Contributors | Glover, Charles J. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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