| dc.description.abstract | This first part of the thesis investigates a fast, non-destructive testing method to characterize asphalt mixtures. While dynamic modulus was recommended by NCHRP Project 9-19 as a test to represent pavement performance, the time consumed by the commonly used cyclic test method hampers its adaptation. The possibility of using the resonance test method for determining the complex modulus in a quicker, simpler, and reliable way was evaluated to address this gap. For comparison purposes, complex modulus testing was performed on two asphalt mixtures using the cyclic loading and the resonance frequency methods. The results plotted in Cole-Cole space show that the measurements from both the tests are consistent. The AASHTO R 84 and Havriliak-Negami models were used to estimate the master curves of dynamic modulus and phase angle. The AASHTO R 84 standard procedure could not be extended to fit the resonance test measurements.
The second part assesses a new optimum asphalt mixture design procedure using the proposed micromechanics-based performance indicator. The original Superpave mixture design relies only on the material specifications and volumetrics criteria to ensure satisfactory mixture performance. Also, to better predict the asphalt mixture performance, understanding the influence of individual mixture components is necessary along with the effective bulk properties, which is often overlooked. These two shortcomings in the current asphalt mixture design procedure were addressed in this thesis by introducing a new performance indicator. The prediction equations from a micromechanical framework developed by Onifade and Birgisson (2021) were used to find the mixture constituents’ modulus. The microstructure characteristics like the volume fraction of phases, the shape and texture of aggregates, and the arrangement of constituents are also incorporated within the equations used. Based on the predicted stiffness values of the mixture and the constituents, a performance parameter termed the mixture/mastic stiffness ratio is introduced. This parameter can provide preliminary analysis indicating the rutting and fatigue performance of a mixture design without the need for extensive testing. The stiffness ratios correlated well with flow number and critical strain energy at the test temperature and frequency. Further, the ratio was sensitive to mixture gradation and aging. | en |
