A Study of The Dynamic Behavior of Asphalt Material Under Milling Conditions
Public DepositedThe success of the pavement industry relies on the successful design and construction of resilient roadway infrastructure. Milling, which is the most widely used method for the recovery of Reclaimed Asphalt Pavement (RAP), involves the forced removal of existing aged material under high loading rates. Current milling specifications are based on industry guidelines, which do not take into account the potential effect of the temperature, long-term aging of the in-place mix, and the high strain rate on the dynamic response of the asphalt pavement during milling. Thus, the objective of this research study was to investigate the impact of these three key milling factors on the dynamic behavior and fragmentation of asphalt material. The dynamic characteristics of asphalt mortar under high strain rates were investigated through the Split Hopkinson Pressure Bar (SHPB) experiments. Asphalt mortar samples were subjected to long-term oven aging and conditioned at three temperatures to simulate the milling conditions within a laboratory environment. Fourier transform infrared spectroscopy (FTIR) was conducted to quantify the changes in the functional groups related to asphalt oxidation after long-term oven aging. The dynamic compressive stress-strain relationships of asphalt mortar under high strain rates were characterized by a rate and temperature-dependent viscoelastic constitutive damage model. Moreover, a numerical analysis of the effect of long-term aging and temperature on milling-induced stresses below the milling depth for two Hot Mix Asphalt (HMA) materials was performed. Lastly, particle size analysis was carried out to evaluate the effect of temperature and milling loading on the gradation characteristics of the fragmented asphalt mortar samples collected after the SHPB experiments, and milled RAP samples from the field. The outcomes of the SHPB experiments provided important insights into the dynamic compressive properties of asphalt mortar under milling conditions. Asphalt mortar exhibited greater compressive strength and energy absorption at higher temperature under high strain rates. Statistical analysis indicated that the temperature has the most significant effect on the dynamic strength, elastic modulus, and ultimate strain of asphalt mortar. The proposed constitutive damage model was calibrated and validated using the results of the 72 SHPB experiments. Therefore, it can serve as a preliminary theoretical framework for characterizing the dynamic compressive behavior of asphalt mortar under milling loading conditions. The results of the finite element simulations highlighted the crucial importance of selecting the appropriate timing for milling operations and conducting a thorough evaluation of the properties of the underlying layers for each rehabilitation project. Particle size analysis revealed that the increase in the drum rotational speed from 100 RPM to 118 RPM results in a greater uniformity coefficient of milled RAP samples. The statistical Weibull function was successful in predicting the gradations of the asphalt mortar and the milled RAP under varying milling conditions. Thus, these findings provide valuable knowledge that can be utilized for the effective control of the milling process, which, in turn, can significantly contribute to constructing sustainable and longer-lasting asphalt pavements.
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- etd-105971
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- Orcid
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- Year
- 2023
- Date created
- 2023-04-27
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- etd-105971
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- License
- Dernière modification
- 2023-06-29
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