Study On Fatigue Performance Experiment Of Different Gradations Asphalt Concrete Under Water-Temperature-Salt Freeze-thaw Condition

Asphalt concrete pavement has become the major type of road construction, and fatigue cracking is one of its major damages. In order to prolong the service life of asphalt concrete pavement, and to enhance the comfort level and security, it is necessary to improve the fatigue performance of asphalt concrete pavement. In northern China, because of the big seasonal temperature differences, the high salt content of soil, and the wide application of de-icing salt, pavement is easy to suffer freeze-thaw damage by the combined effect of water, temperature and salt corrosion. Therefore, it is significant to research the fatigue performance of asphalt concrete pavement under the effect of salt freeze-thaw.Fatigue performance of asphalt concrete under freeze-thaw condition is investigated by the laboratory experiments. By simulating the seasonal temperature differences in northern China, the freeze-thaw cycle temperature is determined from-18℃to60℃, and asphalt concrete with3gradations (AC-13, AC-16, AC-20) are freezing and thawing in pure water and saturated sodium chloride solution under2,4,6and8times of freeze-thaw cycles, then their fatigue performance are tested by the indirect tensile experiment under3stress ratios (0.5,0.6,0.7).The test result shows that, the fatigue life of asphalt concrete gradually decreases under the effect of freeze-thaw cycle, and the decrease is intensified as freeze-thaw times increasing. By2times of freeze-thaw cycles, the fatigue life of asphalt concrete with3gradations in pure water decrease by26.0%,29.1%,31.9%, by8times of freeze-thaw cycles, they decrease by72.1%,76.1%,78.9%. It shows that the fatigue life of asphalt concrete with3gradations decrease in an order of AC-13, AC-16, AC-20. The fatigue life of asphalt concrete in pure water is longer than that in saturated sodium chloride solution. Under the3stress ratios conditions, in the case of AC-13asphalt concrete, the fatigue life decreases by61.9%,74.5%,80.2%, and after8times of freeze-thaw cycles, it decreases in an order of0.5,0.6,0.7.By analysing the effect of freeze-thaw, gradation, salt corrosion and stress ratio conditions on fatigue performance of asphalt concrete, the road performance is evaluated. Theoretical basis of the improvement of service life and durability of asphalt concrete pavement is provided, the optimal design parameter of pavement is defined, and the reference of construction of city pavement is provided.