Research On Dynamic Modulus Of Asphalt Mixture Based On Multi-scale Specimens

This paper mainly takes the dynamic modulus of two pavement materials commonly used in Shandong province highway pavement structure as the main research object,that is,the dynamic modulus and conversion of two types of asphalt mixtures of SMA-13 and AC-20 types with different scales Relationship research.Based on the basic theory of asphalt mixture viscoelasticity and the principle of time-temperature equivalence,the uniaxial compression dynamic modulus test and the two-point bending trapezoid beam dynamic modulus test were carried out on the two types of asphalt mixture specimens of different scales.The influence of temperature,loading frequency and specimen size on dynamic modulus,and the main curves of dynamic modulus and phase angle of different scale specimens were drawn;using regression software to fit the dynamic modulus data of different scale specimens,we got different The conversion model between the dynamic modulus of the scale specimen;the typical value range of the dynamic modulus of the asphalt mixture commonly used in the upper and middle layers of the highway in Shandong Province is recommended.The main research contents and conclusions are as follows:By comparing and analyzing the main curves of the dynamic modulus of the two types of asphalt mixtures at different scales,it can be seen that the influence of temperature and loading frequency on the dynamic modulus of the different scales is the same,that is,the dynamic modulus gradually increases with the temperature Decrease,gradually increase with the increase of loading frequency;phase angle becomes larger with the increase of temperature,and gradually decreases with the increase of frequency.The trends of dynamic modulus and storage modulus of trapezoidal beam specimens with temperature increase are consistent,both decrease with increasing temperature,and the loss modulus increases first and then decreases;the three modes The quantities are gradually increased with the increase of the loading frequency,but the loss modulus changes with the loading frequency is limited.When the temperature is low,as the loading frequency increases,the loss modulus changes little;the phase angle As the temperature increases,it becomes larger and larger.When the temperature is lower than 30?,the phase angle gradually decreases with the increase of the loading frequency.When the temperature is 40?,the phase angle increases with the increase of the frequency.It can be seen from the main curve of dynamic modulus that the change trend of the main curve of dynamic modulus obtained by the two test modes is the same,but the frequency domain of the SPT test is wider;compared with the main curve of dynamic modulus The main angle difference is relatively large.Although the phase angles of the two test modes are reduced overall,the phase angle of the SPT test is obviously increased first and then decreased.At high frequencies,the phase angles of the two are relatively close.At low frequencies,the phase angles of the two are quite different.The phase angle of the asphalt mixture obtained by the trapezoidal beam test is large and the amplitude of the change is also large as the frequency increases.By comparing and analyzing the dynamic modulus test data of different scale specimens,it can be seen that the larger the height-to-diameter ratio of the specimens of the same type of asphalt mixture at different scales at 20?and 10 Hz,the greater the dynamic modulus.Taking the natural logarithm of the dynamic modulus of the specimens at different scales at 20?and10Hz,the data regression analysis software was used to establish the conversion relationship model between the dynamic modulus of the specimens at different scales.Diameter ratio 1:0.38sample conversion relationship is y=-0.0864x~3+0.9228x~2-2.1698x+3.3794,AC-20high-diameter ratio 1.5:1 and high-diameter ratio 2:1 sample conversion relationship is y=0.1074x~3-1.3189x~2+6.4256x-7.5096,SMA-13 and AC-20 height-to-diameter ratio 1.5:1specimens and trapezoid beam specimens dynamic modulus is y=0.2815x~2-1.556x+5.4815,y=-0.9659x~2+8.3695x-14.185.Finally,the dynamic modulus test was carried out on the core samples of 4 highways in Shandong Province,and the numerical conversion was carried out using the conversion relationship model between different scale specimens.The dynamic modulus of the standard scale specimens was obtained,and the new version"The range of dynamic modulus values of commonly used asphalt mixtures at 20?and 10Hz in the Design Specification for Highway Asphalt Pavement was compared.Through the research in this paper,it is recommended that Shandong Province expressway when designing asphalt pavement structure,the upper layer dynamic modulus value range is6000~9000MPa,the middle surface layer dynamic modulus value range is 7000~12000MPa.