Evaluating the Moisture Susceptibility of Asphalt Mixes in Oklahoma

Moisture damage in the form of stripping is a common mode of failure in asphalt pavements. Stripping occurs in asphalt mixtures through the combined effect of the loss of cohesion in the asphalt binder and loss of adhesion between the aggregate surface and the asphalt binder. Water penetrating the asphalt pavement causes a scouring action under traffic which also contributes to stripping. Water inside the asphalt pavement enters between the aggregate-asphalt binder interface and breaks the bond between the aggregate and the asphalt binder. The adhesion force between the aggregate and the asphalt binder is determined by the chemical interaction at the aggregate-asphalt binder interface. Adhesion is also promoted by the aggregate texture and the absorbed asphalt inside the aggregate pores. The effect of moisture can be assessed by measuring the strength, stiffness, or fatigue performance of the mix before and after moisture damage. The procedure currently utilized in AASHTO T 283 is based on subjecting the compacted asphalt specimens to partial vacuum saturation followed by a freeze-thaw cycle. The conditioned specimens are tested to determine their tensile strength. A tensile strength ratio (TSR) is calculated representing the ratio of the tensile strength of the moisture-conditioned specimens to that of unconditioned specimens. Oklahoma uses AASTHTO T 283 to evaluate the stripping susceptibility of mixtures in Oklahoma (ODOT 2019). Several states including Oklahoma have raised concerns related to the ability of AASHTO T 283 to predict field performance. Several problems have also been identified regarding the conditioning procedure followed in AASHTO T 283. These problems include the forced saturation using vacuum which could damage the internal structure of the asphalt, which does not reflect the in-situ field conditions. The AASHTO T 283 conditioning protocol also does not account for the effect of traffic. The moisture induced stress tester (MiST) was introduced to simulate the effect of moisture in the field by applying a cyclic pore water pressure to mimic the pore water pressure generated under traffic. In the MiST test, a special device is used to condition the compacted specimens using a 2-stage conditioning protocol. The first stage of conditioning is intended to simulate the loss of adhesion in the mix by soaking the specimens in hot water for 20 hours. During this stage, the specimens undergo normal saturation without applying vacuum. The second stage of conditioning simulates the effect of traffic on the loss of cohesion in the mix through subjecting the soaked specimens to 3,500 pressure cycles. These pressure cycles represent the effect of traffic causing water scouring in the mix. The effect of MiST conditioning is assessed by comparing the indirect tensile strength of the unconditioned and conditioned specimens. In this research, the MIST conditioning protocol will be evaluated using mixes prepared with raw materials from Oklahoma. The raw materials will be selected to produce mixes that represent a wide range of expected moisture-susceptibility performance. The mixes will also include antistripping additives to improve the moisture-susceptibility performance of poor-performing mixes. The mixes will also be subjected to conditioning using the AASHTO T 283 standard procedure. The ability of the AASHTO T 283 and the MiST procedure to rank the mixes will be evaluated.

  • Supplemental Notes:
    • 22BOSU57

Language

  • English

Project

  • Status: Active
  • Funding: $138000
  • Contract Numbers:

    69A3551747106

  • Sponsor Organizations:

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Managing Organizations:

    Transportation Consortium of South-Central States (Tran-SET)

    Louisiana State University
    Baton Rouge, LA  United States  70803
  • Project Managers:

    Mousa, Momen

  • Performing Organizations:

    Oklahoma State University, Stillwater

    School of Civil & Environmental Engineering
    207 Engineering South
    Stillwater, OK  United States  74078
  • Principal Investigators:

    Elkashef, Mohamed

  • Start Date: 20220401
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers Program

Subject/Index Terms

Filing Info

  • Accession Number: 01844951
  • Record Type: Research project
  • Source Agency: Transportation Consortium of South-Central States (Tran-SET)
  • Contract Numbers: 69A3551747106
  • Files: UTC, RIP
  • Created Date: May 9 2022 10:14AM