Experimental investigation on rheological property of bitumen influenced by preheating process

Bitumen samples for laboratory tests are normally preheated at moderate temperature. However, the preheating process is suspect of influencing the aging process and bitumen property. This research aims to investigate the rheological property of bitumen influenced by preheating process. For this purpose, the matrix bitumen and bitumen aged by Thin-Film Oven Test (TFOT) were preheated for seven cycles, respectively. Dynamic Shear Rheometer (DSR) test was conducted to explore the influence of preheating process on rheological properties of bitumen. The results showed that preheating process shortened the differences in rheological properties between matrix and aged bitumen over preheating cycle. The effect of preheating process on bitumen could be divided into three stages: rapid change stage, stable stage, and aged stage. The rapid change stage, in which bitumen volatilizes rapidly resulting in apparent changes in rheological properties, typically occurs in the first two preheating cycles. The stable stage in which bitumen remains few changes with preheating cycle lasts for a longer period (3-5 preheating cycles). The aged stage, in which excessive heating time is applied on bitumen resulting in the aging of bitumen, usually starts from the sixth preheating cycle. The consequences of this study provide practitioners with proposals to reduce experimental error for bituminous tests by avoiding preheating bitumen more than six times.