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The curing process of cold recycling mixture with emulsified asphalt is a process of emulsion breaking, water evaporation, and cement hydration, resulting in adhesion development and strength formation. There are many factors that affect this process, including curing temperature, curing time, reclaimed asphalt pavement (RAP) contents, and cement contents. However, the evaluation of the promoting effect of each factor is still not quite clear. Hence, in this paper, the curing temperature, curing time, and RAP contents were discussed to find out the dominating factor in this process. The development of moisture loss and indirect tensile strength (ITS) was measured and analyzed through establishing prediction models between them and curing time. Besides, the functional relationship between moisture loss and ITS was also analyzed to evaluate the promoting effect of each factor. The results showed that the curing temperature has a certain impact on the development of moisture loss and ITS and an increase in curing temperature would accelerate the reaction rate, while RAP contents can hardly affect this process. Through functional relationship between moisture loss and ITS, it was found that the development of early strength and adhesion was dominated by ITS despite the increase of curing temperature and RAP contents. Expanding the hydration effect of cement could promote the curing process. However, this dominating role weakened at higher temperature and moisture loss should be treated more carefully. [ABSTRACT FROM AUTHOR]

The entrance and exit sections of a tunnel are subject to different environments, pavements, and traffic conditions, which is quite different from the average highway, and it should be considered differentially, when designing pavement structures. However, there are no clear regulations on it in Chinese specifications. Over the years, a lot of studies were carried on the entrance and exit sections of a tunnel, but there are few ones on the pavement design and its mechanical response characteristics. In this paper, the Huangjiayu tunnel and the Yangkou tunnel in Shandong province were taken as case study engineerings and their pavement structures in the entrance and exit sections are referred to as Str-1 and Str-2, respectively. In Str-1, asphalt pavement was applied inside and outside the tunnel and a transition section was applied. In Str-2, asphalt pavement was applied outside the tunnel and concrete pavement was applied inside the tunnel when it was built in 2004 and a transition section was not applied. Meanwhile, 7 alternative pavement structures (referred to as Str-1a∼Str-1g), in which the lengths of transition sections were different, were proposed, simulated, and analyzed through FE program ANSYS. Through the analysis of maximum shear stresses in asphalt courses and tensile stresses at the bottom of base courses, it was found that setting a transition structure is essential, and it can ensure the continuity of pavements and significantly reduce the sudden change of shear stress of asphalt layer and thus prevent premature pavement distresses. Hence, Str-1 is more reasonable compared with Str-2. Besides, it was also found that when the asphalt surface outside the tunnel is designed to be three layers, it is more appropriate to use Str-1, in which the concrete slab in the transition structure has variable cross section, and the length of the concrete slab is 4.5 m. When the asphalt surface outside the tunnel is designed to be two layers, Str-1b is more reasonable and the length of the concrete slab is also 4.5 m. [ABSTRACT FROM AUTHOR]

Temperature responses of asphalt pavements are significant, because of their potential influence on pavement structure design and distress prevention, particularly in areas that experience large temperature difference. In this study, a 3D finite element model is developed based on transient heat transfer. The aim is to analyse the temperature responses of the Karamay–Altay Highway in northern Xinjiang, which tends to experience large temperature differences and low temperatures. First, the climatic characteristics and pavement distresses in northern Xinjiang were investigated, and the condition defining a large temperature difference was established. Then, to guide the design of the Karamay–Altay Highway pavement structure, the temperature fields of seven pavement structures were determined. The temperature field of the Str-m structure in the Karamay–Altay area was compared to that in Xi'an. In the Karamay–Altay area, it was observed that Str-4 exhibited the minimum temperature variation at the bottom of the asphalt course and base course. It was clear that the degree of downward temperature transfer was closely related to the structure combination type. The results also suggested that a thicker asphalt layer would effectively reduce temperature effects and diminish distresses resulting from temperature. By comparing of the temperature fields of the Str-m structure in the Karamay–Altay area and in Xi'an, it was observed that pavement temperature fields changed drastically in the case study area, and hence revealed that severe pavement cracks in this area were closely related to abrupt temperature changes, low temperatures and large temperature differences. Hence, it was concluded that in northern Xinjiang, pavement designers should consider the large temperature difference condition very carefully. [ABSTRACT FROM AUTHOR]

Temperature adaptability of asphalt pavements is very important, due to their potential influence on pavement structure design, particularly in areas that experience significant temperature differences. In this paper, a finite element (FE) model was developed, and Turpan-Xiaocao Lake Highway in southern Xinjiang was taken as a case study engineering, which tends to experience this adverse environmental condition (temperature difference: 25.5°C; July 14, 2008). In this model, the generalized Kelvin model and the Burgers model were used. The time-dependent tire pressure was considered. To guide pavement structure design and control pavement distresses in this area, seven alternative pavement structures were selected to simulate and analyze pavement temperature fields and the mechanical responses. It was observed that the influence of air temperature had the greatest impact on Str-1, possibly due to the thinnest asphalt course. Moreover, when rutting depth, maximum shear stress of the asphalt course, deflection on the pavement surface, and compressive strains at the subgrade top surface were taken as the evaluation indices, the adaptability of asphalt pavements using compound base courses had obvious advantage due to their strong absorption and reflection of load impact. The adaptability of seven structures analyzed in this paper decreased in the following order: Str-5 > Str-6 > Str-4 > Str-2 > Str-m > Str-1 > Str-3. In addition, it broke the traditional view that asphalt pavement with a flexible base had the poor ability on rutting resistance. Besides, it also suggests that when the thickness of asphalt courses was equivalent, increasing the thickness of chemical-treated base courses would help with the deformation resistance, and vice versa. [ABSTRACT FROM AUTHOR]