Laboratory and Field Evaluation of Cold-in-Place RAP Recycling

Cold in-place recycling (CIR) is a viable pavement rehabilitation technique that recycles 100% of the reclaimed asphalt pavement (RAP) in situ, without heat. Six test sections were constructed on a heavy traffic road in the south of Brazil using CIR with cement and cationic slow set polymer modified emulsion (CSS-1P). Different thickness of the recycled layer (80mm, 110mm, and 150mm) and two types of asphalt surface layers (HMA and Microsurfacing) were investigated. The RAP was sampled during the recycling operations and brought to the laboratory for its characterization and further mechanical tests evaluation (tensile strength, moisture sensitivity, and triaxial resilient modulus). Field samples were obtained from the test sections to evaluate the performance of recycled mixture. They were tested for rutting resistance (Laboratoire Central des Ponts et Chausees (LCPC) wheel tracking test) and indirect tensile resilient modulus. Structural evaluation of the test sections were performed through the falling weight deflectometer (FWD) in different seasons of the year. It was observed a decrease in the modulus of the recycled layers during the rainy season, in comparison with the dry season results. The laboratory tests also indicated a moderate moisture sensitivity material. The backcalculated resilient moduli of the CIR layer presented the same order of magnitude of the moduli obtained in the laboratory tests. The CIR presented reduced permanent deformation in the laboratory and low rutting in the field after two years of the rehabilitation.