Material characterization of hot-mix recycled bituminous pavements
Abstract
Hot mix bituminous pavement recycling is a process in which reclaimed bituminous pavement materials, reclaimed aggregate materials, or both are combined with new bitumen, and/or rejuvenating agents, and/or virgin aggregate as necessary to produce hot-mix paving mixtures meeting all standard materials specifications and construction requirements for the type of mixture being produced. The technique has become widely used in a practical manner. However, there are several fundamental questions still unanswered in the area of hot mix recycling that require immediate research. Among them are homogeneity, compatibility and rate of hardening of a recycled mix when compared to a virgin mix. In addition, assurance is needed that weathering actions, long term behavior, mechanical properties of compacted recycled mixtures and the effect of repeated loads on recycled pavements are not problems. A detailed laboratory investigation was performed to characterize the performance of the hot mix recycled asphalt pavement in comparison with a virgin mix. A virgin mixture and three recycled mixtures were evaluated. Marshall size specimens were fabricated and evaluated using the pulse velocity, resilient modulus, indirect tensile strength, Hveem stability and Marshall stability tests. In addition the recycled binder itself was evaluated using a stage extraction technique and the thin film oven test results. Long term aging of recycled mixtures was also studied. Subjective conclusions were established for the performance of recycled mixtures under various conditions. Virgin mixture stiffness and strength parameters were higher than those of recycled mixtures. However, long term aging properties of two of the recycled mixtures were better than the virgin mix, especially when regarding the failure tensile strain. The thin film oven test and the indirect tensile test were identified as additional criteria for the choice of type and amount of recycling agent to be used. The results of this study will provide the highway engineer with a better understanding of the effect of different factors on the tensile and resilient characteristics of hot recycled bituminous paving mixtures.
Degree
Ph.D.
Advisors
Wood, Purdue University.
Subject Area
Civil engineering
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