PERFORMANCE BASED EVALUATION OF CRACKING IN ASPHALT CONCRETE USING VISCOELASTIC AND FRACTURE PROPERTIES

Cracking is one of the major distresses encountered in pavements. Pavements that fail prematurely due to cracking precipitate lower ride quality, elevate the chance of road accidents, and cause agencies to spend considerable amount of public funds on pavement maintenance and rehabilitation. As part of the concerted endeavor to ensure high performing pavements, extensive research is being undertaken throughout the United States to develop more effective and efficient performance based materials selection and specification procedures as well as mechanistic-empirical (M-E) methods for pavement cracking performance evaluation. However, agencies have been hesitant to introduce the methods to their specifications, pavement evaluation protocols and design procedures for reasons related to complexity and uncertainty associated to precisions and accuracy of these methods. This dissertation contributes to the ongoing performance based specifications and design efforts by addressing known gaps related to linear viscoelastic and fracture characterization of asphalt concrete. Overarching goals of this dissertation research has been enhancement of performance property determination processes and increased confidence in asphalt pavement performance predictions. Specific research contributions include, a simple and robust method is provided to determine phase angle from stiffness data and BBR low temperature specification parameters, stiffness (S) and relaxation properties (m-value), from DSR measurement for linear viscoelastic characterization of asphalt concrete. The ability of dynamic modulus and phase angle master curve parameters to capture the changes in mixture properties is investigated. Finally, increased understanding is achieved regarding fracture properties of asphalt mixtures as it relates to the effect of mix variables and number of replicates to be tested to obtain representative measurement to help agencies make informed decision during mix design and production

Disc shaped compact tension (DCT) specifications development for asphalt pavement

The disc-shaped compact tension (DCT) fracture energy test has been shown to discriminate between asphalt mixtures with respect to their thermal cracking potential. This research refines the DCT fracture energy testing procedure, identifies needed adjustments in asphalt mixture to increase fracture energy, determines the suitability of DCT-test-based parameters as indicators of reflective cracking, and proposes threshold values to lower the potential for premature reflective cracking in asphalt overlays. A number of recommendations have been developed to implement outcomes of this research as well as to fill knowledge gaps identified through this study

Simulating plant produced material in the laboratory to replicate rheological and fatigue properties

As part of an effort by agencies and industry to move towards performance-based design to evaluate mixtures in the laboratory at a smaller scale before moving to full scale operation, laboratory protocols exist to simulate the aging that occurs as a material is produced. However, recent research has shown that these existing protocols may not accurately represent the changes a material experiences in a plant. Moreover, due to the focus of previous studies on the ability of the current method to replicate mixture characteristics and performance in an undamaged state, there is a lack of information as it relates to the damaged state. This paper presents a concise description of a study undertaken on a particular mixture to evaluate the differences in the behaviour of a standard asphalt concrete mixture produced in the laboratory and in the plant to assess the anticipated field performance at the mixture design stage. The results, in terms of the rheological properties of binders extracted and recovered from laboratory and plant produced mixtures as well as rheological, repeated cyclic fatigue, and cracking performance evaluation of the asphalt mixtures, have shown the ability of a short-term oven aging protocol to replicate plant produced material in the laboratory

Simulating plant produced material in the laboratory to replicate rheological and fatigue properties

As part of an effort by agencies and industry to move towards performance-based design to evaluate mixtures in the laboratory at a smaller scale before moving to full scale operation, laboratory protocols exist to simulate the aging that occurs as a material is produced. However, recent research has shown that these existing protocols may not accurately represent the changes a material experiences in a plant. Moreover, due to the focus of previous studies on the ability of the current method to replicate mixture characteristics and performance in an undamaged state, there is a lack of information as it relates to the damaged state. This paper presents a concise description of a study undertaken on a particular mixture to evaluate the differences in the behaviour of a standard asphalt concrete mixture produced in the laboratory and in the plant to assess the anticipated field performance at the mixture design stage. The results, in terms of the rheological properties of binders extracted and recovered from laboratory and plant produced mixtures as well as rheological, repeated cyclic fatigue, and cracking performance evaluation of the asphalt mixtures, have shown the ability of a short-term oven aging protocol to replicate plant produced material in the laboratory