Laboratory Investigation on the Resilient Modulus, Indirect Tensile Strength and Unconfined Compressive Strength of Cold In-Place Recycled Asphalt Mixes Using Foamed Bitumen

There has been a dramatic growth in asphalt recycling and reclaiming as a technically and environmentally preferred way of rehabilitating deteriorated pavements over the last couple of decades. One of the latest asphalt recycling techniques is cold in-place recycling using foamed bitumen. In recent years, there have been a number of successfully implemented cold in-place asphalt recycling projects in Iran; and it seems that the utilization of this method is gaining more acceptances amongst the road authorities and the contractors. At the same time, endeavors to evaluate the performance properties of foamed bitumen mixes were started and are still in progress. The present research, studies the mechanical and the performance properties of foamed bitumen mixes. In the first phase of the project, the effect of aggregate grading, bitumen and cement content and compaction efforts, on resilient modulus and indirect tensile strength (ITS) of 144 foamed bitumen specimens (of various curing conditions) has been investigated and analyzed. In the next phase, the effect of above parameters on resilient modulus and unconfined compressive strength (UCS) of 108 different samples was studied. Results indicate that for the tested materials, changing the aggregate grading from coarse to fine didn’t have a significant effect on resilient modulus, ITS, UCS and the moisture susceptibility of the specimens. Also the effect of increasing bitumen content from two to four percent is negligible. On the contrary, adding one percent cement and increasing it to two percent considerably improved the moisture susceptibility and the mechanical properties of the mixes. Based on the obtained data, a regression model between resilient modulus and ITS of the foamed bitumen mixes was developed to facilitate the prediction of the resilient modulus based on the corresponding ITS values.