Field Aging and Oil Modification Study

2018Final Report; October 2016-July 2018PDFTech Report0092-17-04WHRP 0092-17-04Aging (Materials)Asphalt mixturesOilsPolymersAsphalt Mixture AgingOil ModificationMixture DesignFieldFlexibility IndexHWTRuttingCrackingBinder GradesWisconsinUnited StatesWisconsin. Dept. of TransportationBahia, Hussain U.Sadek, HusamRahaman, M. ZiaurLemke, ZacharySwiertz, DanReichelt, SigneUniversity of Wisconsin--MadisonBehnke Materials Engineering, LLCBitumix Solutions, LLCWisconsin. Dept. of Transportation. Research and Library UnitWisconsin Highway Research ProgramUS Transportation CollectionThe objectives of this research project included: 1. Develop laboratory short- and long-term aging protocols that will simulate field aging effects measured on plant-produced mixtures from field strip by comparing mixture and extracted binder properties to those of laboratory-produced mixtures, and 2. Verify the effects of softening oils and polymers used to adjust binder grades on results of short- and long-term aging protocols developed in this study. In addition to these objectives, to develop the laboratory short- and long-term aging protocols, a study on the effect of reheating and aging procedures was conducted at the beginning of the project. The analysis of the study results led to the following findings: \u2022Based on the oven comparison and pre-heating effects results call for the standardization of mixture handling and aging procedures to minimize possible influence of variation in mixture temperature. Size of containers used for sampling, condition of container (open versus closed), and checking distribution of temperatures within the oven are important items that should be included in standard sampling, handling, and aging of field produced mixtures. \u2022Mixtures produced in laboratory had comparable volumetric properties to plant-produced mixtures. However, it is noted that methods used for measuring Gmm could be variable and highly operator dependent. A careful look at details for measuring Gmm, and developing a more consistent protocol, is highly recommended. \u2022Properties at high temperatures (MSCR) and intermediate temperatures (LAS) of binders extracted and recovered from plant-produced mixtures are significantly different than properties of binders recovered from lab-produced mixtures. The same properties are also different than original binders collected from site. These differences could be due to solvent used in extraction as well as interaction with aggregates. This is particularly important for new MSCR parameters. It is highly recommended that this issue of solvent used in extraction and recovery be addressed to avoid disputes between suppliers and agency. \u2022In general, correlations between HWT and SCB-IFIT tests results of lab- and plant-produced mixtures are acceptable. It is therefore not recommended to change number of aging hours or oven temperature in the laboratory short-term aging to simulate plant short-term aging. \u2022The Flexibility Index (FI) parameter is highly sensitive to mixture aging and magnitude of FI is controlled by post-peak slope during test. However, change in P200 content, AC% or Dust to Binder Ratio values in plant-produced mixes does not appear to affect resulting FI for either binder grade. \u2022The eight blends prepared with different oils and additives to target PG58-34 resulted in binders with different properties and characteristics (%R and Jnr) which could affect performance of mixtures prepared with these blends. SCB-IFIT results showed that mixtures with REOB oil have the lowest FI values at all aging levels, but also the lowest aging rates when compared to the mixture with no oils or with bio-oils. The use of bio-oil significantly improved FI values at different aging levels, but also increased aging rate of FI. The mixtures with no oils showed similar FI results and aging rates to mixtures with bio-oils. \u2022The collective results from the field samples and oil modification of this study confirm that long-term oven aging of 14 hours(LTOA-14) is too severe for asphalt mixtures and not suitable to distinguish between mixtures. The use of 6 hours is therefore recommended as the standard long-term aging procedure for asphalt mixtures.79