Layer coefficients of cold in-place recycled layers from performance data

With cold in-place recycled (CIR) pavements becoming an increasingly popular treatment for pavement life extension, it is important for local agencies to have data that justifies the design parameters that influence the effectiveness of such treatments. Studies have shown that the effectiveness of CIR depends on its milling depth, and in order for agencies to better decide the pavement design, depth of CIR to be milled and placed, the authors have developed a procedure to back-calculate the structural layer coefficient of CIR layers based on performance data, in order to evaluate their structural capacity. This paper attempts to establish a relation between the structural capacity of the CIR layer and the international roughness index (IRI) of the pavement over time, using the results of previous research determining a definite differential between the IRI of pavements with different CIR thicknesses.