Development of Volumetric Acceptance and Percent Within Limits (PWL) and Criteria for Stone Metrix Asphalt (SMA) Mixtures in Indiana
Lee, J., Haddock, J. E., & Jeon, J. (2022). Development of volumetric acceptance and percent within limits (PWL) criteria for stone matrix asphalt (SMA) mixtures in Indiana (Joint Transportation Research Program Publication No. FHWA/IN/JTRP-2022/29). West Lafayette, IN: Purdue University. https://doi.org/10.5703/1288284317580
SMA is to be designed based on SMA volumetric properties in terms of air voids content (Va), voids in the mineral aggregate (VMA), and adequate stone-on-stone contact. For construction quality assurance (QA) purposes, INDOT currently accepts SMAs based on aggregate gradation and asphalt binder content. Thus, there is a discrepancy between SMA design criteria and construction acceptance. To better align design and construction, it is necessary to consider SMA volumetric properties in the use of QA. For HMA mixtures, INDOT has already transitioned from volumetric QA acceptance procedures to PWL. Today, SMA still uses adjustment points not based on robust statistics for QA acceptance.
SMA QA samples and QA data sets were collected from projects constructed in 2019 and tested in the laboratory. The Hamburg Wheel Track Test (HWTT) was performed on the 2019 QA samples to evaluate SMA rutting performance. Additionally, the PWL for HMA was applied to the 2019 SMA QA data to see if the HMA PWL method would work for SMA. Possible SMA QA measurements were compared to past QA data and HMA QA measurements. In addition, Voids in the Coarse Aggregate (VCA) was evaluated as a possible SMA QA measurement. Finally, using the suitable QA measurements for SMA, a PWL parameter study was performed to find PWL that provides a Pay Factor (PF) equivalent to the current SMA Adjustment Point (AP) PF. The current SMA QA measurements (binder content, gradation, and density) are recommended for Indiana's SMA PWL. Based on the results of applying PWL to SMA QA data for the last four years, SMA PWL specification limits are recommended. Also, the SMA PF equations are suggested to get the SMA PWL to have PF equivalent to the current AP PF.
percent within limits (PWL), adjustment point, specification limits, pay factor, stone matrix asphalt (SMA), QC/QA
Joint Transportation Research Program
Indiana Department of Transportation
West Lafayette, IN
Date of this Version