عنوان مقاله [English]
The response of flexible pavement layers to applied loads in field tests such as falling weight deflectometer (FWD) to a high extent relates to bound layer temperature. Therefore, sensitivity of recorded deformations and back-calculated moduli to temperature has been investigated in this research. In addition to conventional asphalt layer, this study has focused on the response of cold recycled layer with bitumen emulsion and cement. In this regard, Semnan-Damghan highway has been considered as the case study in which the cold recycled layer has been constructed during the rehabilitation process. Non-destructive tests including FWD and ground penetrating radar (GPR) were performed to estimate the layers elastic moduli and thickness. Back-calculation analysis was accomplished using ELMOD software. Furthermore, a back-calculation analysis method has been proposed by implementing a code by BASIC programming language. In order to validate the back-calculated moduli, destructive tests were performed by sampling in some of studied stations. Indirect tensile stiffness modulus and triaxial tests were accomplished to measure the bound and unbound layer moduli in laboratory, respectively. Based on the obtained results for both asphalt and recycled layers the back-calculated moduli obtained by recommended method were more precise than the ELMOD software. The temperature sensitivity of asphalt and recycled layers were compared with each other. Since the recycled layer contained two binders including bitumen emulsion and cement, the dependency of its behavior to temperature was to some extent different from hot mix asphalt. At the final stage the temperature correction coefficients were determined for the material and testing condition encountered with in the current research study. The precision of results obtained from these coefficients were compared with those presented in the literature. According to the obtained results the presented correction coefficients resulted in a more precise modulus estimation and therefore higher reliability in direct pavement design procedure.