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MEASUREMENT OF MIXING EFFICIENCY IN PAVEMENT RECYLCING

Complaints have been voiced in recent years that the quality of asphalt cement has deteriorated, that it "isn't sticky", etc.. This is thought to have caused problems in mixes, such as tenderness, stripping, raveling, and premature aging. The oil embargo is mentioned as having contributed to this situation. The study reported in this paper was to determine the validity of these complaints. There are othe aspects of asphalt pavements to be considered as having caused these problems, such as changes in the manner of specifying asphalt grades, introduction of drum-mix plants, use of bag-house fines, new types of rollers (vibratory), etc. Several sets of data on asphalt cements were collected. These included the FHWA fingerprint file with test results on more than 400 asphalts collected in the period 1950-1970, programs of Asphalt Institute, some in cooperation with FHWA, in the 1970s, and new data collected by the authors in recent years up to 1980-81. The data sets are essentially 311 asphalts from 1950, 58 from 1960, 68 from 1977, 125 from 1979, and 77 from 1981. The oil embargo was in 1973. In addition, loose box samples of mix and field cores were taken from 50 construction jobs. The tests made to characterize the asphalt cements included kinematic viscosity at 275 F, absolute viscosity at 140 F, penetraton at 77 F and 39.2 F, softening point, and Rostler-Sternberg analysis. Samples were also aged in the thin-film oven test and the consistency tests repeated. The test results and the analyses of the data are presented in various ways--tables, bar graphs, scatter plots, etc. Statistical analyses are used to determine whether or not there are significant differences in the data according to year of production. Without going into these details, thee conclusions state that except for temperature susceptibility there have been no long term, significant changes in asphalt properties that can be identified by the analytical techniques being used. This does not mean that a decrease in asphalt quality has not occurred; if it does exist, current tests cannot detect it. (Author)

  • Supplemental Notes:
    • Paper from the Proceedings of the Association of Asphalt Paving Technologists, Vol. 52 pp 61-87, 1983.
  • Corporate Authors:

    Minnesota Department of Transportation

    395 John Ireland Boulevard
    St Paul, MN  United States  55155
  • Authors:
    • Lee, T
    • Terrel, R L
    • Mahoney, J P
  • Publication Date: 1985-4

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Filing Info

  • Accession Number: 00395851
  • Record Type: Publication
  • Files: TRIS, STATEDOT
  • Created Date: Feb 28 1986 12:00AM