Cold In-Place Recycling

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Evaluating Effective Asphalt Content in CIR Mixtures


Daniel Wegman and Mohammadreza Sabouri, Braun Intertec Corporation


This study evaluated the effect of emulsion content reduction during the CIR process in the field on mix properties. Three laboratory CIR mix designs were performed using the same RAP material and emulsion at three different mixing temperatures. The mix design results showed that as the mixing temperature increased, the optimum emulsion content decreased significantly. Also, increasing the mixing temperature improved the mixture compaction. Both the dry and retained stabilities were also higher for the high-temperature mixtures. The critical low temperatures of high-temperature mixtures were higher than the room-temperature mixture (indicative of a worse performance) but still lower than the -20°C requirement. From the results of this study, it appears that reducing the emulsion content of CIR mixtures during the heat of the day does not necessarily deteriorate mixture properties. This could result in substantial savings for agencies that use this process without sacrificing long-term performance.


Minnesota DOT Local Road Research Board Report No. 2019-43.