Research On Intelligent Temperature Control Asphalt Pavement Based On Thermochromic Materials

Asphalt pavement is the main surface of high-grade pavement in China,with many advantages.However,due to the black pavement,which absorbs more heat in summer,the temperature of asphalt pavement is too high,and it is easy to cause high temperature related diseases such as rutting and hugging.In winter,the black body heat radiation is fast,which causes the road temperature to drop too fast.At present,the existing asphalt pavement cooling methods have certain effect,but also have their own disadvantages.In this paper,based on the thermochromic materials,the thermochromic modified asphalt is prepared.The performance of the thermochromic asphalt is tested and analyzed from four aspects: micro mechanism,asphalt binder,asphalt mixture and the actual temperature control performance of outdoor environment.Firstly,3%,6% and 10% thermochromic asphalts were prepared by using red,blue and black thermochromic materials respectively.The samples were tested by FTIR.It was judged that no new functional groups were produced by the change of absorption peak.Therefore,the temperature control performance mainly depends on the property of thermochromic material.Gel permeation chromatography(GPC)test showed that Mn and Mw increased with the increase in the content of 6%,but decreased after more than 6%,probably because the 6% thermochromic materials had been saturated with light components.Atomic force microscope(AFM)test results show that 70 × asphalt used in this experiment does not have bee structure,but thermochromic asphalt all has bee structure,and it reaches the maximum when the content is 3%,a larger content reduces the number of bee structure and the roughness of the material surface.Secondly,the mechanical properties,Superpave rheological properties,thermodynamic properties and temperature control properties of 9 groups of thermochromic asphalt and 70# base asphalt were tested.The mechanical properties include penetration,softening point and ductility.The rheological properties include dynamic shear rheological test,low temperature bending beam rheological test and Brookfield rotational viscosity test.The thermodynamic properties include differential scanning test and specific heat test.The test results show that the three indexes,high-temperature performance and rotational viscosity are improved with the increase of the content of asphalt,but the performance of low-temperature performance is decreased when the content is more than 6%.In addition,the specific heat of thermochromic materials is also increased with the increase of the content,which is conducive to reducing the temperature fluctuation of asphalt pavement.Considering the test results and economy,it is recommended that the content of thermochromic material should be 5% ～ 6%.Then,based on the optimum content,the thermochromic 70# asphalt and thermochromic SBS thermochromic asphalt were prepared,and SMA-13 gradation was formed.For 70# asphalt,rutting test,low temperature bending beam and residual stability test were used.For thermochromic SBS asphalt,dynamic creep,low temperature semicircle bending,freeze-thaw splitting and semicircle fatigue tests were used to test the performance of asphalt mixture.The test results of two kinds of asphalt mixtures show similar results.The black and blue thermochromic materials significantly improve the high temperature,low temperature and fatigue performance of asphalt mixture,especially the black thermochromic asphalt mixture has the best performance,but the red thermochromic material weakens the performance of asphalt mixture,so it is not recommended to use.The specific reasons need further study.Finally,the temperature control effect of each group of three-layer pavement structures was tested by using iodine tungsten lamp to simulate sunlight and low temperature box to simulate winter environment.The test results show that the temperature rising rate and the maximum temperature of the pavement structure on the top layer of the thermochromic asphalt mixture are slow at high temperature,and the temperature falling rate is slow at low temperature,and the time to reach the freezing point is also later.In addition,the temperature control performance of the samples after two rounds of thermal aging and ultraviolet aging is reduced,but it is still better than the traditional asphalt pavement.In this study,the microcosmic mechanism of thermochromic asphalt is explored,the optimal content and road performance of thermochromic powder are determined,the temperature control effect of thermochromic asphalt mixture is verified,which provides a reference for improving the temperature field of pavement and prolonging the service life of asphalt pavement.