Long-Term Evaluation of Cold-in-Place Recycling and Factors Influencing Performance

AbstractCold in-place recycling (CIR) is a type of rehabilitation strategy that has shown to significantly improve the condition of flexible pavements with adequate subgrade support. The process involves milling the distressed existing surface layer(s), adding asphalt binder (e.g., emulsion, foamed) and then recompacting the modified mixture. Over time, there has been a steady increase in CIR rehabilitation projects in Iowa. Although pavement restoration is the primary goal, it is equally important to investigate factors that influence CIR performance to determine the effectiveness of the rehabilitation method on the pavement structure. This study evaluated the performance of approximately 100 CIR sections in the State of Iowa. The pavement sections included in the study showed that CIR rehabilitation significantly reduced pavement distresses. The analysis found that CIR mitigates pavement distresses such as transverse cracking, longitudinal cracking, and fatigue cracking while improving the roughness or the international roughness index (IRI). The IRI, a measurement of serviceability and performance, showed that thicker CIR layers remained smoother longer. The overall findings of this study can be used as guidance for making future decisions for pavement rehabilitation and understanding the interplay between CIR thickness and IRI.