Effect of Specimen Geometry and Test Configuration on Fracture Process Zone for Asphalt Materials

The Illinois Flexibility Index Test (I-FIT) is a fracture test for asphalt concrete (AC) using a notched semi-circular sample that is subjected to three-point bending. Specimen’s thickness, air void content, and notch length, as well as loading rate may affect the I-FIT results. This study evaluates the effect of these variables on the fracture process zone (FPZ). The FPZ is the region surrounding the notch tip in which micro cracks are formed before a macro crack is observed. Hence, the energy dissipation due to the deformation that occurs in this region eventually controls the global response of the specimen. The work presented in this paper investigated the effect of modifying the notch length, specimen thickness, loading rate, and air void content, on the size of the FPZ. A high-resolution camera was used during testing to allow digital image correlation (DIC) measurements of the strain and displacement fields. It was found that thicker specimens exhibit larger FPZ area than the thinner ones. Similarly, the size of the FPZ increased with higher air void content. However, the size of the FPZ area decreased with loading rate as AC becomes stiffer. Finally, no distinct relationship between the FPZ and notch length was observed because at longer notches, the FPZ region interacted with the compressive strain region surrounding the loading head. This important observation also suggested that notch length should be limited when conducting fracture tests with semi-circular bending geometry.

• Supplemental Notes:
  • This paper was sponsored by TRB committee AFK50 Standing Committee on Structural Requirements of Asphalt Mixtures.
• Corporate Authors:

  Transportation Research Board

  ,    
• Authors:
  • Rivera-Perez, Jose
  • Ozer, Hasan
  • Al-Qadi, Imad L
• Conference:
  • Transportation Research Board 98th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2019-1-13 to 2019-1-17
• Date: 2019

Language

• English

Media Info

• Media Type: Digital/other
• Features: References;
• Pagination: 4p

Subject/Index Terms

• TRT Terms: Air voids; Asphalt concrete; Specimens; Thickness
• Identifier Terms: Illinois Flexibility Index Test (I-FIT)
• Uncontrolled Terms: Digital image correlation; Fracture process zone; Loading rate; Notch length; Specimen geometry; Specimen size
• Subject Areas: Highways; Materials; Pavements;

Filing Info

• Accession Number: 01698409
• Record Type: Publication
• Report/Paper Numbers: 19-05168
• Files: TRIS, TRB, ATRI
• Created Date: Mar 2 2019 3:41PM