Research On The Effect Of Temperature On The Static Properties Of Asphalt Concrete

As a mixture of asphalt,hydraulic asphalt concrete has good impervious resistance and durability,so it is widely used in large dam structures.The asphalt concrete core dam is considered to be the most promising dam type and the most common hydraulic dam type at home and abroad at present.The mechanical parameters and other properties of the core dam can be analyzed by static triaxial test,and the mechanical parameters can be calculated by using Duncan Zhang model based on static triaxial test.In addition,due t.o the differences in engineering environmental conditions in various regions,especially in the north and south,the asphalt concrete core dam needs to take into account the actual operating temperature of the hydraulic dam body,so it is necessary for us to carry out research,on the mechanical properties of asphalt concrete at different temperatures.Current on mechanical parameters of hydraulic asphalt concrete at home and abroad in the study,using the most is Duncan model,but due to the temperature sensitivity of asphalt,leads to the form of asphalt concrete under different temperature are completely different,generally with the temperature of asphalt concrete material with a process of transition from brittle to viscoelasticity,Therefore,the research on the constitutive model of asphalt concrete has become an important subject in the theoretical research field of asphalt concrete.In this paper,based on the static triaxial test of asphalt concrete,the change law of its mechanical properties with temperature is studied with the materials transported from a project as the test raw materials.Based on the Duncan Zhang model,the variation law of the model parameters with temperature was studied,and the fitting degree of the model without temperature was analyzed by using the idea of statistics.The main research contents and results of this paper are as follows:(1)On the basis of qualified testing of raw materials,carry out mix proportion design research.Firstly,the orthogonal experiment was used to design the mix ratio of 9 groups,and the split test was carried out.The results of the split test were calculated by the range analysis method,and the mix ratio of 3 groups of primary election was obtained.Then,a series of mechanical properties tests were carried out on the three groups of mixture ratio,including compression test,tensile test,trabecular bending test,permeability test,water stability test,static triaxial test,Marshall stability and flow value test,etc.Finally,the optimal mixture ratio was determined to be 6.5%of asphalt and stone,11%of filler dosage,and 0.39 of gradation index.(2)Static triaxial test was carried out on the above mixture ratio(6.5%oil-to-stone ratio,11%filler dosage,0.39 gradation index).The static triaxial test results of asphalt concrete under four different temperatures(4℃,10℃,16℃ and 22℃)and four different confining pressures(0.3MPa,0.5MPa,0.7MPa and 0.9MPa)are mainly analyzed,including the change rule of stress-strain curve with temperature.The change law of volume deformation and axial deformation with temperature and the change law of failure deviatoric stress with temperature.The test results show that the higher the temperature of asphalt concrete,the smaller the deviatoric stress,i.e.the smaller the failure strength,and the lower the overall deviatoric stress,the more obvious the stress softening phenomenon,the more obvious the shear expansion phenomenon.(3)The static triaxial test data of asphalt concrete were processed and analyzed by using Duncan Zhang hyperbolic model,and the variation rule of each parameter with temperature was analyzed.It was found that each parameter of asphalt concrete gradually decreased with the increase of test temperature,and only the volume modulus index increased with the increase of temperature.Then the theoretical deviatoric stress of asphalt concrete is calculated by using the test parameters of Duncan Zhang model,and the correlation coefficient between theoretical deviatoric stress and test deviatoric stress,the standard error of estimation and the goodness of fit are calculated by using the idea of statistics.By analyzing the fitting degree of Duncan Zhang model and test curve at different temperatures,it is concluded that Duncan Zhang model fits well at low temperature and low confining pressure,but it can not simulate the softening phenomenon of asphalt concrete,so the mechanical properties of asphalt concrete at high temperature and high confining pressure do not conform to Duncan Zhang hyperbolic model.