Long Term Monitoring of Asphalt Concrete Anti Stripping Test Sections

The South Dakota Department of Transportation (SDDOT) has used lime as an anti-strip additive for asphalt concrete (AC) for a number of years, as initial laboratory testing showed it to be a superior anti-strip agent. Recently, contractors have complained about personnel exposure and problems handling lime. They have requested the substitution of liquid or other anti-strip agents, instead of lime, to reduce moisture susceptibility. The problem is complicated by the lack of a suitable test of moisture susceptibility that can reliably predict field performance. For example, Minnekahta limestone performs poorly on tests such as ASTM D4867M Effect of Moisture on Asphalt Concrete Paving Mixtures but, as a calcareous aggregate, should not be very susceptible to stripping and has not exhibited a stripping problem in the field. The overall effect of using lime as an anti-stripping agent provides additional benefits beyond lowering stripping potential. It increases the stiffness of the mix, reduces asphalt requirements and is less sensitive to asphalt cement properties. Lime has an extensive track record nationally and is acknowledged as a superior anti-stripping agent. Many of the liquid or polymer anti-stripping agents are relatively new technologies, may be asphalt sensitive, and may adversely affect AC concrete properties in terms of overall performance. In addition, it is difficult to verify the actual amount of anti-stripping agent in the asphalt cement. Some liquid anti-stripping agents, when employed at too high a dosage, can actually increase stripping susceptibility. The level of confidence in allowing the use of alternative anti-stripping agents is not currently sufficient enough to justify substitution, even though there may be a significant cost savings in doing so. This research is proposed as a means of providing the guidance based on field performance necessary to make an informed decision with regard to future use of anti-stripping additives. In addition, the research will investigate ways to minimize safety and environmental concerns when lime is used as an anti-stripping agent. The objectives of this research project are to: (1) recommend improvements to the lime addition process that minimize personnel exposure and environmental impacts and that assure control of lime addition rate; (2) determine which available anti-stripping technologies are appropriate for field testing to insure long term performance; and (3) develop guidelines for future use of anti-stripping agents based on field performance, including economic factors, along with necessary testing protocols, specifications and procedures. Research tasks for this project include the following: (1) Review and summarize literature relevant to AC moisture susceptibility and mitigation of stripping. (2) Meet with the technical panel to review project scope and work plan, especially with regard to the installation of test sections during the 1999 construction season. (3) Conduct a survey to determine the state of the art for current moisture susceptibility testing and anti-stripping technologies with an emphasis on current practices in surrounding states. (4) Evaluate the performance of two existing field test sections near Brookings, SD incorporating a liquid anti-strip agent. (5) Examine current lime addition practices to determine alternative strategies that minimize safety and environmental concerns. (6) Conduct laboratory testing of candidate anti-stripping technologies including moisture susceptibility, stripping potential under load (Hamburg or other test protocol), resilient modulus, and asphalt concrete properties. (7) Develop and submit plan notes for inclusion into two construction projects, one in each of the 1999 and 2000 construction seasons. The plan notes should define a series of a minimum of four test sections, including a control, per project designed to evaluate the effectiveness of lime and other anti-stripping agents used in conjunction with susceptible aggregate. Asphalt concrete properties should be adjusted to provide direct comparison and to enhance the likelihood of stripping occurring. (8) Monitor and evaluate the construction of the test sections and document test results obtained during construction. Conduct additional testing deemed necessary on materials and samples from test sections including moisture susceptibility, asphalt content and properties, gradation and resilient modulus. (9) Monitor and evaluate the initial performance (including Falling Weight Deflectometer and other additional testing) of the test sections through the conclusion of the research and note any significant differences. (10) Recommend improved testing and evaluation procedures, practical guidelines and specification changes that will ensure improved handling of lime addition and provide alternative anti-stripping technologies which perform on an equal basis to lime and are economically competitive. (11) Submit an Interim Report after 12 months detailing progress and recommending guidelines or specification changes that can be implemented prior to the conclusion of the research. (12) Prepare a final report and executive summary of the literature review, research methodology, findings, conclusions, and recommendations. (13) Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.

    Language

    • English

    Project

    • Status: Active
    • Funding: $25000.00
    • Contract Numbers:

      SD2003-05

    • Sponsor Organizations:

      South Dakota Department of Transportation

      Transportation Building, 700 E Broadway
      Pierre, SD  United States  57501
    • Project Managers:

      Leibrock, Chris

    • Performing Organizations:

      University of Nevada, Reno

      College of Engineering
      Reno, NV  United States  89557
    • Principal Investigators:

      Sebaaly, Peter

    • Start Date: 20030701
    • Expected Completion Date: 0
    • Actual Completion Date: 20110430
    • Source Data: RiP Project 26334

    Subject/Index Terms

    Filing Info

    • Accession Number: 01461456
    • Record Type: Research project
    • Source Agency: South Dakota Department of Transportation
    • Contract Numbers: SD2003-05
    • Files: RiP, STATEDOT
    • Created Date: Jan 3 2013 1:46PM