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To make up for the deficiency of the widely used ratio of dissipated energy change (RDEC) approach in the study of fatigue damage characteristics, the deficiencies of RDEC approach were pointed out by analyzing the RDEC evolution, and the ratio of cumulative dissipated energy change (RCDEC) was defined by the monotonically increasing cumulative dissipated energy and its evolution was analyzed. The damage variable of asphalt mixture was defined by the RCDEC, and a damage model was established to analyze damage evolution. The material fatigue damage resistance was analyzed by the RCDEC. The results show that RDEC cannot distinguish and characterize the nonlinear continuous damage evolution behavior of the asphalt mixture under diiferent conditions. The defined RCDEC can fully consider the energy dissipation history, distinguish and characterize the nonlinear continuous damage evolution behavior of asphalt mixture. The proposed fatigue damage model can accurately describe the nonlinear continuous damage evolution behavior. RCDEC can reflect the fatigue damage resistance, and the increase of RCDEC wiil lead to the acceleration of damage evolution rate and the corresponding decrease of fatigue life. [ABSTRACT FROM AUTHOR]

To study the factors that influence the test precision of percent air voids of asphalt mixture based on mesoscopic scale, German Phoenix v I tome I x S240 industrial X-ray CT was utilized in combination with orthogonal test and variance analysis to study how different CT parameters and gradation types influenced the 3D reconstruction volume parameters of asphalt mixture. Marshall specimens were scanned by changing the parameters of CT and gradation types of asphalt mixture and the results were used for three-dimensional analysis, the relation between influence factors and percent air voids was also built, and then determine the optimal scanning parameters. The test results showed that it is feasible to make three-dimensional volume analysis of asphalt mixture on the basis of meso-scale; the scanning parameters and gradation types have different levels of effects on reconstruction results; the test accuracy would be improved by increasing scaning voltage and current properly and as well as choosing the appropriate filters. The percent air voids that obtained on the base of both meso-scale and macro-scale had good correlation under the condition of appropriate parameter of apparatus, in addition can improve the accuracy and economy of the test. [ABSTRACT FROM AUTHOR]

In order to determine the spraying amount of waterproof binder for bridge deck pavement, rubbex modified binder and two typical kinds asphalt mixtures were used to analyze different factors that affect the shearing properties of waterproof bond layer by skew shear test and direct shear test, the mechanical properties of waterproof bond layer was also studied in the paper. The results show that the maximum shearing stress increases linearly as the loading speed increased, the temperature also has significant effect on the shear performance of waterproof bond layer, with the increase of temperature, the shear resistance performance became worse dramatically. The shear stress and deformation obtained from shear test can be used as the indicators to evaluate the bliear resistance performance. Based on the research of above, the method of determining binder spraying amount can be proposed. [ABSTRACT FROM AUTHOR]

A finite element model combined with bridge deck pavement structural style is established to analyze mechanical properties and influence factors of bridge' deck pavement structure. The effect of different levels braking force coefficients, top and bottom layer material modulus combination of bridge deck pavement, deck pavement thickness variation are analyzed. Results show that different horizontal loads have little effect on principal stress but much effect on shear stress inside the pavement layer. With the increase of horizontal load, the maximum shear stresses inside pavement layer and waterproof adhesive layer increase linearly. Principal stress inside the pavement layer changes little, while shear stress between layers decreases in a small amplitude with the increase of combination modulus of pavement layer. Increase of the thickness of pavement layer has little effect on principal stress and maximum shear stress between layers decreases with increase of thickness. Conclusions obtained by this paper can be used to provide theoretical reference for material selection and structure design of bridge deck pavement. [ABSTRACT FROM AUTHOR]