The primary objective of the study conducted herein was to assist MoDOT in the development of a balanced mix design asphalt specification in Missouri. At the onset of the study, a detailed climatic study was conducted. Next, asphalt performance testing was carried out across a range of temperatures to establish property-temperature relationships. Eleven mixtures were tested using the Disk-Shaped Compact Tension Test (DCT) across a range of low temperatures, while the Hamburg Wheel Tracking Test (HWTT) was conducted across a range of high temperatures. Mixture testing was carried out on both plant-produced mixtures and field cores. Two additional cracking tests were investigated in this portion of the study: the Illinois Flexibility Index Test, or I-FIT, and the IDEAL cracking test. Field performance data from MoDOT’s pavement management database was extracted to assist with the development of specification thresholds for the cracking and rutting tests investigated. For BMD specification development, a novel approach was taken herein whereby recommended specification thresholds were introduced for all three cracking tests currently under investigation in Missouri and across the Midwest (DC(T), I-FIT and IDEAL).
While the current study focused on mainline, high-type mixes, preliminary recommendations for shoulder mixes and other low traffic paving applications are provided, which may be of interest in larger urban areas and for municipal projects where closer control of asphalt performance via testing and materials investment is of concern. Stone-Matrix Asphalt mixes were not considered in this study. The recommended tests and thresholds provided herein should be viewed as preliminary and can be adjusted based on practical considerations and stakeholder discussions in a consensus process. Further validation of the proposed BMD tests and limits via long term field monitoring or testing on a controlled test road or test track facility is highly recommended. Additional work to apply the recommended BMD to quality control specifications and performance-related quality assurance specifications in a practical manner is also recommended.
Report number: cmr 20-010
Published: September 2020
Project number: TR201811
Authors: William G. Buttlar, Loreto Urra-Contreras, Behnam Jahangiri, Punyaslok Rath, and Hamed Majidifard
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