Short-Term Laboratory Conditioning of Asphalt Mixtures (2015) / Chapter Skim
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5 Background Asphalt mixtures may be produced in either batch or drum mix plants and then compacted at temperatures ranging from 220°F (104°C)
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6material flow is reversed, feeding the aggregate into an outer drum where it is mixed with asphalt before being discharged. As discussed, the changes in mixture components, mixture processing, and plant design have left many paving technologists questioning the validity of current mix design methods in adequately assessing the volumetric needs of asphalt mixtures and the physical characteristics required to meet performance expectations.
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7 Traxler 1961 Factor on Field Aging Binder chemistry and aggregate absorption major effects Chipperfield and Welch 1967 Aggregate gradation no effect Terrel and Holen 1976 Plant type significant effect; DMP < BMP due to lower temperature and less moisture Lund and Wilson 1984 & 1986 Binder type and binder source significant effects Chollar et al.1989 Slightly more aging from DMP than BMP Mogawer et al. 2012 • Production temperature, silo storage, inclusion of recycled materials, and reheating significant effects • Softer binder with RAP = harder binder without RAP Daniel et al.
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8Over the last few decades, a number of studies were performed (1) to evaluate the effect of various laboratory STOA protocols for HMA and WMA in order to achieve equivalent binder aging and absorption that occur during production and construction in the field and (2)
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9 pronounced than the short-term aging time. Among the five selected laboratory STOA protocols, 2 hours at 275°F (135°C)
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10 compared to the short-term aged mixtures, and that the stiffening effect was more pronounced for virgin mixtures (i.e., mixtures with 0 percent RAP) than the RAP mixtures.
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11 cated that a laboratory STOA protocol of 4 h at 275°F (135°C) was representative of the short-term aging occurring during production and construction.
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12 these two projects have already started, their conclusions were not available prior to the completion of NCHRP Project 9-52. To summarize, the main findings of the previous studies on long-term aging of asphalt mixtures are: • Field aging is primarily quantified based on pavement in-service time.
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