Laboratory versus plant production: impact of material properties and performance for RAP and RAS mixtures

ABSTRACT

Agencies are moving towards performance-based design methodologies for asphalt pavements, and different methods to evaluate the asphalt performance in the laboratory have been developed. The laboratory performance can be evaluated at the mix design and/or production stages. A good understanding of differences in the behaviour of mixtures produced in the laboratory and plant is required to assess anticipated field performance at the mix design stage. The objectives of this paper are to compare the measured properties of plant-produced and laboratory-produced mixtures, to evaluate the effect of mixture variables on the differences observed, and to translate these to anticipated differences in fatigue performance through pavement evaluation using a linear viscoelastic layered analysis. In this study, 11 plant mixed, plant compacted, and their corresponding laboratory-mixed, laboratory-compacted mixtures are evaluated through binder and mixture testing. Mixture variables include aggregate gradation, binder grade and source, and recycled materials’ type and content. Performance grading on extracted and recovered binders, and complex modulus and SVECD fatigue testing on mixtures were conducted, and fatigue life was predicted using layered viscoelastic pavement design for critical distresses software. Most of the results show the laboratory mixtures are generally stiffer than the plant mixtures, but there is no constant shift for all mixtures. Larger differences are observed for the 19 mm and PG 58-28 mixtures and binder source appears to influence the differences as well. Different plants result in different effects on the properties of plant and lab-produced mixtures. This study provides a unique set of data that expands understanding of differences between laboratory and plant production of asphalt mixtures.

KEYWORDS:

• HMA
• laboratory mixtures
• plant-produced mixtures
• RAP
• RAS
• dynamic modulus
• SVECD fatigue
• pavement evaluation

Acknowledgements

The authors would like to acknowledge New Hampshire Department of Transportation (NHDOT) for sponsoring this study, Beran Black and Matthew Courser at NHDOT for their efforts in fabricating LMLC specimens and conducting binder testing, and Mary Westcott, David Duncan, and Peter Moore at Pike Industries Inc. for fabricating PMPC specimens and providing production information.