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Performance Evaluation of Cold In-place Recycling Mixtures in Nevada: Laboratory Testing
AdvisorSebaaly, Peter P.S.
Civil and Environmental Engineering
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Cold In-place Recycling (CIR) consists of pulverizing and rebinding a portion of the existing asphalt concrete layer with asphalt emulsion and chemical additives without heating to produce a restored pavement layer. However, a severely damaged asphalt concrete mix presents a challenge for the design engineer due to the uncertainty in its performance after construction. This research evaluated the rutting and cracking performance of CIR by means of the dynamic modulus master curve, Repeated Load Triaxial Test (RLT), Hamburg Wheel Track Test (HWTT), Overlay Tester (OT), and the beam fatigue test. Mechanistic evaluations of the CIR mixtures were performed after obtaining the rutting and fatigue models of the studied mixtures. CIR mix designs for graded RAP from Southern Nevada (District Ӏ) with four different emulsion types and at a 4.5% lime slurry level were performed using the Superpave mix design method and verified by the Hveem mix design method with few modifications on both methods. The moisture susceptibility of the mixtures was evaluated using the Tensile Strength Ratio (TSR) criteria. Results showed high stripping and rutting resistance of the evaluated mixture. Even though the mixtures had low crack propagation rates indicating a good reflective cracking resistance, the required energy to initiate a crack was low as well. In addition, a stiff-brittle behavior was observed in the beam fatigue test. The predominant mode of failure of CIR pavements was fatigue cracking of the CIR layer with a coefficient of 0.23 for Southern Nevada. Hence, due to the lack of statistical difference between the average fatigue performance models for the Northern and Southern CIR mixtures., it can be concluded that the source of the RAP materials does not have a significant impact on the performance of the CIR pavement. Therefore, it is recommended that an average structural layer coefficient for the CIR layer of 0.25 should be used for the design of CIR pavements throughout Nevada.