Pioneering the Evaluation of Balanced Asphalt Mix Design in Oklahoma

There is a national effort, including the Oklahoma Department of Transportation (ODOT), to move toward a balanced mix design (BMD) approach for the design of asphalt mixtures. This paper presents the findings of ODOT’s Phase I implementation of BMD in Oklahoma, whose objective was to evaluate selected ODOT mixtures to assist with determining test procedures, specifications, and special provisions for evaluation and eventual adaptation of a BMD procedure for ODOT. The test plan consisted of evaluating I-FIT test results from 31 existing mixes and I-FIT and Ideal CT_Index tests from nine mixes from three ODOT projects, consisting of three control mixes and six BMD mixes. Inconsistent results were found from the testing within and between the data sets. BMD mixes differed from control mixes by the addition of RAP, increased VMA, and increased asphalt content. Many of these high VMA BMD mixes collapsed in the field resulting in void properties below specification limits. It is recommended that ODOT consider adopting the Ideal CT test due to ease of testing and perform this testing on all mix designs submitted for use on ODOT projects.