Effects of paver stoppage on temperature segregation in asphalt pavements

Temperature segregation, which occurs as a result of differential cooling of asphalt mixtures, is a serious challenge during asphalt paving operations. The objective of this study is to investigate temperature segregation caused by paver stoppage through field measurements, laboratory tests, and finite-element (FE) analyses. Five Louisiana asphalt rehabilitation projects were selected for the study. A multisensor infrared temperature scanning bar (IR-bar) system was used for field measurements of the real-time thermal profiles of uncompacted asphalt mats behind the paver. Laboratory performance of thermally segregated asphalt pavements from three selected projects were evaluated by measuring the fracture resistance of field asphalt samples at 25°C using the semicircular bend (SCB) test. From field measurements, it was clear that temperature segregation occurs whenever the paver stops, and the level of segregation (temperature drop) is dependent on the duration of paver stoppage, e.g., temperature segregation of more than 55°C can occur within less than 1 h of the stoppage. Laboratory performance test results showed that the asphalt samples from unsegregated areas generally had better fracture resistance than the samples from the segregated areas did. FE analysis results showed nonlinear decreases of temperature in the uncompacted asphalt mats. Furthermore, the cooling rate of hot-mix asphalt (HMA) was almost twice as fast as the warm-mix. To avoid high-severity temperature segregation (more than 21°C), it is recommended that paver stoppage time should be kept minimum with a maximum duration of 4 min for hot-mix and 6 min for warm-mix asphalts, respectively