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Conventional asphalt pavement has a deep surface color and large thermal inertia, which leads to the continuous absorption of solar thermal radiation and the sharp rise of surface temperature. This can easily lead to the permanent deformation of pavement, as well as aggravate the urban heat island (UHI) effect. Cool pavement with a reflective coating plays an important role in reducing pavement temperature and alleviating the UHI effect. It is of great significance to study the influence of temperature on the mechanical response of different types of pavement under vehicle loading. Therefore, this study examined the heat exchange theory between pavement and the external environment and utilized the representative climate data of a 24 h period in the summer. Two kinds of three-dimensional finite element models were established for the analysis of temperature distribution and the mechanical responses of conventional pavement and cool pavement. The results show that in this environmental condition, conventional pavement temperatures can exceed 50 °C under high temperatures in summer, which allows for the permanent deformation of pavement and further affects the service life of asphalt pavement. The temperature difference in a conventional pavement surface between 6 h (24.7 °C) and 22 h (30.2 °C) is much less than that between 22 h (30.2 °C) and 13 h (50.1 °C) in the summer. However, the difference in the vertical displacements of the pavement surface between 6 h and 22 h is much larger than that between 22 h and 13 h. One reason is that the difference in temperature distribution between the morning and night leads to changes in pavement structure stiffness, resulting in significant differences in vertical displacement. Cool pavement has a significant cooling effect, which can reduce the surface temperature of a road by more than 15 °C and reduce the vertical displacement of the pavement by approximately 11.3%, which improves the rutting resistance of the pavement. However, the use of cool pavement will not change the horizontal strain at the bottom of the asphalt base and will not improve the fatigue resistance of asphalt pavement. This research will lay the foundation for further clarifying the difference in the mechanical properties between the two types of pavements in the management and maintenance stage.

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The possibility of using the dynamic shear rheometer (DSR) with 4 mm parallel plates and 3 mm gap is investigated as an alternative experimental method to measure the rheological properties of asphalt binders at low temperature. A special butterfly silicone mold was prepared for this purpose and the corresponding testing procedure was also developed. Five different asphalt binders, which are part of two active research projects, were selected. Frequency and temperature sweep tests were conducted using the DSR with three plate–plate geometries: 4 mm, 8 mm, and 25 mm. The new testing procedure was used to measure at low temperatures. The method recently proposed by the Western Research Institute and based on DSR tests with 4 mm parallel plates and 1.75 mm gap was also used for comparison purposes. Black diagrams and Cole-Cole plots were then used to evaluate the experimental data. Complex modulus and phase angle master curves were generated, and the rheological parameters compared. Finally, the two spring, two parabolic elements, one dashpot (2S2P1D) model was selected to investigate the rheological properties of the binders. Results indicate that the proposed procedure is a simple and reliable experimental method and represents an alternative experimental option to measure and analyze the rheological properties of asphalt binders at low temperature.

As the use of warm and cold asphalt mixing technologies provides an opportunity to save energy during production, it is important to determine if this lower mixing temperature also has a long-term effect on the binder chemical and rheological properties and performance. In this study, a link between the chemistry and rheology of bituminous binders with a focus on short-term aging temperature is proposed. This link is made using a rheological aging index (RAI), the crossover temperature and a chemical aging index (CAI). The RAI is calculated using the difference in the integration areas under shear modulus master curves generated from Dynamic Shear Rheometer (DSR) data on unaged and aged bitumen. The cross over temperature is defined as that when the material transitions from elastic to viscous behaviour. The CAI is obtained from Fouriertransform infrared spectroscopy (FTIR) measurements by combining the carbonyl and sulfoxide indices. In addition, the effect of aging on the molecular size distribution of the binders was evaluated using Gel Permeation Chromatography (GPC). Two asphalt binders from two sources at two RTFOT aging temperatures 123 C and 163 C corresponding to warm mixing and hot mix mixing temperatures respectively were used.The rheological aging index, the chemical aging index and GPC delivered the same trends, showing that the short-term aging temperature has a significant effect on long-term chemical and rheological properties. The extent of this depends on the source as some binders were identified as being more aging resistant.

A. (2022). RILEM TC 279 WMR round robin study on waste polyethylene modified bituminous binders: advantages and challenges. Road Materials and Pavement Design.