| Gussasphalt concrete shows good performances in water resistance, aging and fatigue resistance, and is highly compliant to steel decks, thus has been widely used in steel deck pavement in Europe and Japan. Both Germany and Japan have formulated gussasphalt deck pavement specifications, gussasphalt constructions in keeping with which could serve more than 20 years. This technology has been introduced to China, with the development of long-span steel bridges, on which a series of studies have been carried out, and then put into use in numerous projects. Judging from the application effect, the performances of gussasphalt are better than those of common asphalt concrete in water resistance, aging and fatigue resistance and low-temperature anti-deformation capacity. However, under heavy traffic conditions, local microfractures and net-shaped cracks could still be seen in gussasphalt works, for several possible inducements. One basic cure is to study and further enhance the fatigue resistance capacity of gussasphalt concrete, which has significant academic and engineering application value.In this thesis, the studies of the factors affecting the fatigue resistance of gussasphalt concrete is to be sorted into internal and external, in accordance with its different representation. Internal factors refer to those affecting fatigue performance in material composition and molding, and external factors to those affecting fatigue properties of concrete in simulated external use conditions. Then a method of determining fatigue properties for high strength modulus asphalt concrete is to be formulated, and comparative and analytic researches of the traditional and new ways are to be made. A comparative analysis on fatigue behaviour is also to be made by various analysis methods of guss asphalt, elastomeric modified concrete SMA10 and modified asphalt concrete AC10 under different conditions. Chief researches and results are summarized as follows:The internal factors take types, quantities, and mixing temperature into consideration for the concrete fatigue properties. Obtained by experiments, the type of a certain kind of asphalt makes a significant effect on its fatigue resistance. And based on the principle of energy dissipation, it could be derived that the cumulative dissipated energy of gussasphalt has a good linear relationship with loading times under log log coordinates. The prediction mould of fatigue life has been established in accordance with this principle, through which, fatigue life of gussasphalt concrete could be predicted at different strain conditions.When the asphalt-aggregate ratio increased from 8.5 to 9.5, fatigue life appears to reduce instead of increasing. This shows that there is an optimum asphalt quantity of the mixture. And different mixing temperature have an significant impact on initial stiffness modulus and decay rate of the stiffness modulus. As the temperature rises up, decay rate become faster, while the mixing temperature lows, slower the rate is. And there also exists correlativity between decay rate and initial stiffness modulus. At the temperature of 190℃to 210℃, it could show good properties of fatigue resistance, with over loading times over a million .As the temperature goes up, fatigue life decreases, particularly at a temperature of 240℃and 250℃, its loading times are just 100,000.In the study of external factors, test temperature, strain level and loading frequency are mainly considered. Through tests, it could be mastered out that these factors affects fatigue life greatly. The decay rate of gussasphalt stiffness modulus gets fasters with the loading times at a higher strain level. However, the strain level also influences the lag angle significantly,in a way of lag angle decreases with increasing strain level. And the initial stiffness modulus of gussasphalt is very sensitive to temperature. When the temperture is low at 5℃, it could reach to 19469MPa, As the temperature rises up, the initial stiffness modulus goes down. When the temperature is as high as 25℃, it is just 2131MPa. That is to say, the fatigue resistance capacity is quite low at a certain low temperature, while rising the temperature could cause the capacity to enhance.what's more, the effect of loading frequency on lag angle can be divided into three stages. When the temperature is at 5℃～10℃, the deformation of gussasphalt with the load is relatively small. This kind of deformation which is considered as recoverable belongs to elastic class. If the temperature is at 10℃~15℃, deformation could partly recover(this phase ,in fact, is a transition phase). Under the interaction of viscosity and elasticity, the deformation is called viscoelastic. While the temperature rises from 15℃to 25℃, deformation forms greatly, and the lag angle increases to a stable situation. Most of the deformation could not get back this time, and it mainly shows its viscous. Meanwhile, the initial stiffness modulus of gussasphalt increases as the the loading frequency goes up. If its loading frequency increases from 10Hz to 14Hz, cyclic loading times could be reduced greatly from millions to thousands. In the same way, the loading frequency also influences the lag angle. When it is from 8Hz to 14Hz, the angle decreases from 45.3 to 31.2. And gussasphalt cumulative dissipated energy could be largely influenced by the change of loading frequency. If it is from 4Hz to 10Hz, dissipated energy is not so sensitive. However, when if increases from 10Hz to 14Hz, the reducement of this energy could be greater both at rate and degree.The stiffness modulus of gussasphalt presents three phases as the loading times accumulate.1)stiffness modulus of mixture developing unstablly and fast;2)stiffness modulus changing sustainablly and stably with a certain rate. 3)rate of stiffness modulus decreasing rapidly until the fatigue failure occurs. Each phase takes the total fatigue life of, respectively,5-10%,70-85% and 5-10%. In accordance with the feature of high stiffness modulus of gussasphalt, a new determining method of fatigue has been created. That is to regard the turning point at the third phase of modulus decay as the fatigue failure. Compared with the traditional way, this new measurement could present the characteristics of fatigue behaviour precisely.Through the analysis of the dynamic fatigue failure process of gussasphalt, the change law of damage factors could be derived. And in accordance with the evolution law and after fitting these factors, a fatigue failure model of gussasphalt with temperature coupling has been established. It is the factor which damages the gussasphalt that is called the critical fatigue factor. And after calculation, we could come to a conclusion that when the temperature is at a range of 5℃to 20℃, the critical factor is about 0.55 to 0.75. In the same way, the critical factor is relatively less at a low temperature, however, increases gradually as the temperature goes higher.Difference analysis of the new and traditional methods indicates that stiffness modulus at fatigue failure determined by the new method could result in a higher differential rate at a lower strain level, the rate decreases with the rise of strain level. A larger difference in fatigue life could be obtained from a lower asphalt-aggregate ratio. When this ratio goes higher, the loading times derived from two fatigue determining get closer to each other. At the same time, the fatigue life of gussasphalt is extremely sensitive to temperature, and the weakening rate of stiffness modulus slows down with the increase of temperature, showing greater differences in fatigue life than that from the traditional method.From the studies of fatigue differences between gussasphalt and traditional asphalt concrete, it can be concluded that the three-phase determining method can determine more rationally the difference in fatigue behaviour of gussasphalt from other types of concrete. At different strain levels, the bending stiffness modulus, loading dispersion capacity and deformation resistance of GA-10 is much higher than those of SMA-10 and AC-10.At lower strain level, the difference in weakeing rates of initial stiffness are not so obvious as it is at a higher level. GA10 is less sensitive to strain than that of AC10 and SMAl0, presenting better toughness. Besides, the fatigue behaviour of gussasphalt performs obvious advantages over common types of concrete at low temperatures. However, as the temperature rises, this kind of mortar structure, which has the features of high asphalt and slag ratio, will be much more highly impacted by temperature than that of SMA10 and AC10. The rigidity and toughness of the mortar decrease rapidly, and will lose advantages in fatigue behavior. A similar law can be seen from these three kinds of stiffness modulus with the varieties of loading times, while the reduced range of fatigue life of GA10 is larger than the other two, indicating that the gussasphalt is much more sensitive to loading frequency than SMA10 and AC10.
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