Effect of rejuvenation on cold recycled and multiple cold recycled asphalt mixtures

Abstract eng:
Cold recycling of asphalt pavements is a standardized and well established set of techniques used for decades in pavement engineering and road rehabilitation. The crucial aspect of these techniques is the re-use of deteriorated (aged) material which is processed cold by adding bitumen emulsion, foamed bitumen and/or cement. Related phenomena, which was so far studied only in a limited extent is the mix behavior after the cold recycled material is aged and deteriorated in the pavement again (e.g. after 15–25 years) and has to be reused again. This was tested and simulated as part of the presented research. Reclaimed asphalt was firstly used for standardized cold recycled mix design with common set of tests which are done for these materials. Then the cold recycled mixture was aged, crushed and reused again in a new type of cold recycled mixture. In one case of assessed cold recycled mixtures emulsion with rejuvenating agent was used to assess the effect of such rejuvenator on multiple recycled mixtures. For all stages of recycling always same set of tests was done (moisture susceptibility, indirect tensile strength, stiffness and resistance to crack propagation). For the ageing a test protocol was used which is prescribed in the prepared prEN standard heating the test specimens at 85°C for several days. Results presented in the paper show on one hand the abilities of multiple recycling with some recommendations on possible limits which are related mainly to the reasonable bitumen content. Some positive effects of rejuvenating agent are shown related to reduced stiffness and strength properties which helps to limit later possible problems with premature cracking.

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