Development of a New Modified TSRST Test to Measure the Thermal Stress of Asphalt Supporting Layer in the Slab Track System

The unique thermal stress environment of asphalt supporting layer (ASL) in the slab track system is critical to its service safety. The extra thermal load is responsible for causing large thermal stress in ASL. A new modified thermal stress restrained specimen test (TSRST) method was developed to measure the thermal stress develop-ment of ASL during the cooling process. The high density polyethylene (HDPE) blocks were assembled onto the asphalt mixture beam to provide extra thermal load automatically during the cooling process, the modified TSRST test were conducted on two types of asphalt mixture types comparing to the standard TSRST test. The tests results show that the extra thermal load accelerates the development of thermal stress in asphalt concrete and elevates the fracture temperature and transition temperature. The modified TSRST test was proved to charac-terize the effect of the extra thermal load effectively, and the test results have good repeatability.