United States Department of Transportation
i
Effect of moisture and aging on asphalt pavement life : part 1 - effect of moisture.
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1996-01-01
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[PDF-4.22 MB]
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Abstract:Considerable research has been carried out on the effect of water on asphalt mixtures, and test methods to investigate the effect of water have been developed. However, most of this work has been related to stripping and the effect of additives, where external water enters or affects the pavement following construction. There is little published research directly concerned with the problems of mixing moisture in hot mixed asphalt concrete and long-term durability related to mixing moisture. This report presents the results of a study to investigate the effects of mixing moisture on mechanical properties of asphalt mixtures. The potential benefits of lime and Pavebond Special were also investigated. The repeated load diametral test device was used to measure the resilient modulus, fatigue, and permanent deformation characteristics of laboratory specimens prepared with and without moisture (0, 1, and 3%) and with and without lime (0, 1%) and Pavebond Special (0, 0.5%). Mixtures were prepared which were representative of two projects for which considerable field data were available. One project utilized marginal aggregate and the other good quality aggregate. To evaluate the long-term durability of mixtures, they were tested before and after conditioning using the Lottman approach. The test results showed that inferior performance occurred for mixtures with 3% moisture, but was most pronounced in mixtures with high void contents. However, the mixtures with marginal aggregate showed improved performance at 1% moisture content, associated with their lower void contents, which may be due to absorbed moisture preventing asphalt absorption and the higher effective asphalt content of these mixtures. The addition of lime resulted in distinct improvement of performance for moist samples from the project which had good quality aggregate, but high air void contents. However, neither additive showed substantial benefit for moist mixtures from the project with marginal aggregate and low air void contents.
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