Low temperature properties of PMA binder and mixes and thermal cracking prediction of asphalt pavement
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2005
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Abstract
This thesis describes a system for the evaluation of the low temperature properties of asphalt mixes resisting thermal cracking. Two modifiers, SBS and EVA, were used for asphalt modification. BBR and DTT were used to investigate low temperature creep and fracture properties of asphalt binders; IDT was used to study those of asphalt mixes. The modification with SBS was found more effective than that with EVA. Two existing empirical methods for mix stiffness prediction were evaluated. It was found that the Bonnaure method predicts relatively accurate mix stiffness, but the Heukelom and Klomp method significantly underestimates it. The possibility to predict the mix tensile strength was also investigated. It was found that the normalized mix tensile strength is well-correlated with the mix failure stiffness; the maximum tensile strength of mixes is well correlated with that of binders. It is suggested that the current Superpave asphalt binder specification (AASHTO MPla) should not use the pavement constant 18 and the DTT binder strength to predict the mix cracking temperatures. The thermal stress should be calculated using the mix creep properties predicted from those of the binders. The mix tensile strength can be found by the concept of practical stiffness and the mix maximum tensile strength, which can be either tested using IDT or predicted from that of the binders. The two existing explicit models, CAS and CASB, were examined to extend stiffness master curves. The stiffness master curves predicted by Van der Poel nomograph were modified as an alternative model for the same purpose. The restraint by the pavement surface course itself is one of the predominant factors to cause thermal cracking. Based on this mechanism and the analysis of the stored strain energy in asphalt pavement due to temperature drop, a theoretical cracking frequency prediction model using the energy criteria was developed. It was found that the prediction with this model is generally consistent with the IDT testing results in terms of the low temperature property evaluation of asphalt mixes and also consistent with the field observations, that the thicker the asphalt pavement, the longer the crack spacing.
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Bibliography: p. 216-240
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Bai, B. (2005). Low temperature properties of PMA binder and mixes and thermal cracking prediction of asphalt pavement (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/249