Durability of Asphalt Mixtures Exposed to Long-Term Moisture Conditioning

Durability of asphalt mixtures immersed in water at 60°C for up to 70 days were investigated to better under the moisture-damage phenomenon. Moisture-damage in asphalt mixtures can be defined as the loss of adhesion between the aggregate and asphalt mastic bond or the loss of cohesion within the mastic in the presence of moisture that leads to loss of durability. The mixtures investigated comprised a limestone aggregate, two mineral fillers (granite and limestone), and a 40/60 pen bitumen and were compacted to three nominal air void levels (4, 6, and 8 percent) using a gyratory compactor. Durability of the asphalt mixtures was estimated using indirect tensile stiffness as a function of moisture conditioning time. Stiffness generally decreased with conditioning time (and consequently water content) except at low exposure times where low water content was associated with a slight but repeatable increase in stiffness. Mixtures containing granite filler and/or high air voids were less durable than similar mixtures containing limestone. The effect of moisture exposure on durability was found to be reversible as moisture conditioned asphalt mixtures that had lost up to 80% of the initial stiffness upon drying fully recovered. The reversible nature of the moisture-induced stiffness degradation suggests a plasticization process whereby the bulk mastic is softened and the critical stress concentration location is moved from the interfacial region of the aggregate-mastic bond into the bulk mastic. Estimates of mastic thickness and length of diffusion paths obtained from image analysis of micro-CT scans of the asphalt mixtures internal structure suggest moisture diffusion was mainly restricted to the bulk mastic and not the aggregate-mastic interface. The results suggest cohesive rather than adhesive failure dominate the durability of asphalt mixtures under the long-term moisture exposure used in this study.

• Supplemental Notes:
  • This paper was sponsored by TRB committee AFK40 Characteristics of Asphalt-Aggregate Combinations to Meet Surface Requirements.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Apeagyei, Alex K
  • Grenfell, James R A
  • Airey, Gordon D
• Conference:
  • Transportation Research Board 93rd Annual Meeting
  • Location: Washington DC
  • Date: 2014-1-12 to 2014-1-16
• Date: 2014

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Photos; References; Tables;
• Pagination: 16p
• Monograph Title: TRB 93rd Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Asphalt mixtures; Durability; Limestone aggregates; Mastic asphalt; Moisture content; Tensile strength; Thickness
• Subject Areas: Highways; Materials; I33: Other Materials used in Pavement Layers;

Filing Info

• Accession Number: 01515140
• Record Type: Publication
• Report/Paper Numbers: 14-0127
• Files: TRIS, TRB, ATRI
• Created Date: Feb 21 2014 3:16PM