Alaska Hot Mix Asphalt Job Mix Formula Verification

AUTC project number: 309024

PI(s):

Juanyu (Jenny) Liu (UAF)

Funding:
  • US Department of Transportation (RITA)
  • Alaska Department of Transportation & Public Facilities
  • Start Date: Aug 1, 2009
  • End Date: Jan 31, 2012

Project Summary

Some asphalt pavement does not last as long as it should, which means that every year, the state spends significant sums on repair and maintenance of Alaska’s paved roads. Since hot mix asphalt is the major paving material used in Alaska, assuring the quality of this material is a critical issue for contractors, ADOT&PF, and other agencies responsible for pavements. This project is assessing elements related to HMA quality assurance specifications and evaluating how well contractors meet the requirements of job mix formulas. During summer 2010, researchers field-tested a rehabilitation and resurface project at Mile 287–305 of the Parks Highway, just south of Nenana. Asphalt mixtures with four different scenarios were sampled from nine sublots. The mixtures included specimens mixed and compacted using JMF in the laboratory, loose mixtures collected from windrow, and either compacted in the field using a portable gyratory compactor or compacted in the laboratory, AUTC Ongoing Projects and cores retrieved from the field. Pertinent data from ADOT&PF and from contractors at each phase of lab/design, production, and new construction were obtained, including general project information, details of the materials and JMF used in the construction, and all construction test data. Over the next year, four primary tests for JMF properties will be conducted in the university lab, including aggregate gradation, asphalt content, mix volumetrics (e.g., air voids and voids in the mineral aggregate), and density. In addition, hot mix asphalt performance will be investigated to further verify the JMF and evaluate any impact of the construction process. These performance tests will include an indirect tension test for low-temperature performance and a dynamic modulus and rut test with a simple performance tester. Project results will lead to revision of current mix design protocols, benefit the asphalt-paving process, and ensure the quality of HMA. Verification will enhance the long-term performance of HMA pavements and significantly reduce the state’s pavement maintenance and repair budget.