Temperature segregation of warm mix asphalt pavement: Laboratory and field evaluations

Temperature segregation refers to as different mixture cooling areas during construction in asphalt pavements. The objective of this study is to evaluate the effect of temperature segregation on warm mix asphalt (WMA) with laboratory and field tests. The performance of WMA compacted at four various temperatures was evaluated in the laboratory. The temperatures were measured during construction in the field sections with infrared thermography and plug-in thermometers. The pavement quality indicator (PQI) was applied to measure the density and the air void content at 216 testing locations the day after construction. In addition, field cores were collected to verify some of the PQI results. The test results showed that temperature segregation of WMA had a remarkable effect on the aggregate structure, density, water stability, high temperature stability, low temperature cracking and tensile strength. The reason for temperature segregation and related preventive measures are recommended at the same time. Based on the study, the preliminary temperature segregation criteria are recommended with the consideration of the field measurement. In application, the temperature segregation of a typical gradation with a nominal maximum aggregate size of 19 mm, referred to as AC-20 WMA, was suggested to be divided into four levels in view of the air void content: no segregation, low-level segregation, medium-level segregation and high-level segregation. The corresponding temperature differences were <3 °C, 3-8 °C, 8-18 °C and >18 °C, respectively.