Effects of End Constraint Conditions in Compression Test at High Temperatures

The triaxial compression test is mostly carried out to investigate the mechanical behaviour at higher temperature of asphalt mixtures in the laboratory. The test requires that the applied stresses are representative to the real stress conditions in the field as they are introduced by a moving wheel. In the triaxial test it is assumed that the stress situation is exactly known. However, the state of stress in the test is quite often non-uniformly distributed due to end effects which are mostly shear stresses on the end surfaces as a result of friction between the loading platens and the specimen. In order to better understand the influence of end friction on the test results two end friction conditions were used, being complete constrained end conditions realized by gluing the loading plates on the specimen and reduced friction conditions realized by using a friction reduction system (FRS). The tests were conducted on dense asphalt concrete (DAC) and porous asphalt concrete (PAC) specimens with a diameter of 65 mm and 130 mm in length. A deformation correction was developed to exclude the deformation of the FRS from the measured total vertical deformation by the built in displacement transducer. The stress-strain curves at those two end constraint conditions were plotted together and compared with respect to the tangent modulus and deviator failure strength. The results show that the end friction introduces extra confinement on the contact surface between loading platens and specimen surfaces and results in overestimation of the tangent modulus and failure strength. Confinement reduces the tendency of barreling due to the end constraints, but the values of the tangent modulus and failure strength are still overestimated since the existence of end constraint. Therefore application of a FRS as used in this study or a similar effective system is highly recommended for both monotonic and cyclic loading compression testing (for instance repeated permanent deformation testing).

• Supplemental Notes:
  • This paper was sponsored by TRB committee AFK50 Standing Committee on Characteristics of Asphalt Paving Mixtures to Meet Structural Requirements. Alternate title: Effects of End Constraint Conditions in Compression Tests at High Temperatures.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Wang, Jingang
  • Molenaar, A A A
  • van de Ven, M F C
  • Wu, Shaopeng
• Conference:
  • Transportation Research Board 95th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2016-1-10 to 2016-1-14
• Date: 2016

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Photos; References; Tables;
• Pagination: 16p
• Monograph Title: TRB 95th Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Asphalt concrete; Asphalt mixtures; Compression tests; Deformation curve
• Uncontrolled Terms: Dense graded asphalt mixtures; End constraint conditions; Friction reduction systems; Porous asphalt concrete; Triaxial compression tests
• Subject Areas: Highways; Materials; Pavements; I31: Bituminous Binders and Materials;

Filing Info

• Accession Number: 01590183
• Record Type: Publication
• Report/Paper Numbers: 16-3969
• Files: TRIS, TRB, ATRI
• Created Date: Feb 14 2016 4:01PM