| Fatigue damage is the result of water,temperature, load combine action. In this process, water and changeable temperature alter the single damage without water condition.This make the whole fatigue damage process has become more complicated.On the hand,load and deicing salt also accelerated asphalt concrete damage.Over the years, the fatigue performance of asphalt concrete has always been a main emphasis of road engineering research.According to the winter temperature in east China, indirect tensile fatigue tests were carried out to study the laws of fatigue life of asphalt concrete.This article conducts the research through tests from the following three aspects:1.The fatigue life of asphalt concrete after different freezing and thawing times.2.Salt erosion affects on the fatigue life of asphalt concrete.3.The fatigue life of asphalt concrete after different freezing and thawing temperature.4.The fatigue life of different types of asphalt concrete in the same condition.5. Prediction of asphalt concrete splitting strength by ultrasonic testing.Analysis is carried out of the impacts on fatigue life of asphalt from freezing and thawing times,chloride corrosion, asphalt type and freezing and thawing temperature respectively.The article main conclusions are as follows:(1) The fatigue life of asphalt concrete is on the decline with the increase of freezing and thawing times.At a certain temperature range(from-5℃to15℃),the fatigue life of AH-70asphalt concrete which is in water after2,4,6,8freeze-thaw cycle is75.1%,62.8%,49.6%,40.4%respectively of the fatigue life which is without freezing and thawing cycle.(2) Under the action of salt erosion and freezing,the surface of asphalt concrete become spalling and the fatigue life has a obviously a downward tendency. At the same temperature range and the same times of freezing and thawing, the fatigue life of asphalt concrete which is in salt water is lower than those which in water. Under the temperature of-5℃to15℃, AH-70asphalt concrete which is salt water after2,4,6,8freeze-thaw cycle,the fatigue life is respectively72.9%,58.1%,47.0%,28.1%of blank block. (3) After asphalt concrete is given freeze and thaw cycle under three temperate ranges of-5℃to15℃,-10℃to10℃,-15℃to5℃, indirect tension fatigue is tested and it is observed that the faster temperature drops and the lower the temperature stays,the more serious the frost damage is.(4) At the same freeze-thaw times and the same freeze-thaw temperature,the fatigue life of SBS modified asphalt concrete is higher than the fatigue life of AH-70asphalt concrete. With the increasing of freeze-thaw times, the rate of descent of SBS SBS modified asphalt concrete is lower than AH-70asphalt concrete.Under the temperature of-5℃to15℃,AH-70asphalt concrete which is in water after2,4,6,8freeze-thaw cycle,the fatigue life is respectively75.1%,62.8%,49.6%,40.4.%of blank block.SBS modified asphalt concrete which is in water after2,4,6,8freeze-thaw cycle,the fatigue life is respectively80.0.1%,71.8%,65.9%,56.0%of blank block.(5) The asphalt concrete under different test conditions is tested by ultrasonic.According to the data get regression equation about wave velocity and splitting strength, fc=0.1507e(00005v), R2=0.9196, fc=0.2594e0.0004v, R2=0.9297.Splitting strength can be predicted which is without splitting test by using the regression equation, in preparation for the indirect tensile fatigue test.In conclusion, freeze and thaw cycle and salt erosion have significant impact fatigue life on asphalt concrete. SBS modified asphalt concrete could reduce the impact of frost damage and salt erosion on fatigue life, reason being that addition of SBS modifier into matrix asphalt increases the melting point and reduces the brittle point of asphalt. It is thus necessary to further the research into SBS modified asphalt in engineering to reduce the damage of freeze and thaw to asphalt surface and generate theory basis for asphalt durability study. |
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