Research On Characteristics And Detection Methods Of Asphalt Mixture Damage Induced By Water-temperature-radiation

Since the1980s, with the rapid development of the national economy and roadtransportation volume, highway construction in China has been drastically expanded. Due tothe advantages of smooth, low noise, high driving comfort and strong abrasion performance,etc., asphalt pavement has become the major construction pavement for most senior highwayin China.For the regions with frequent rain and high temperature in summer, serious prematuredamage of asphalt pavement will appear under the combined effects of the external factors,such as the frequent alternating changes of rain, high temperatures as well as sunshine, andthe traffic load. Frequent rain will not only make the asphalt pavement surfaceunconsolidated, but also cause the loss of fine aggregate inside the pavement, and thusdestroy the integrity. The effect of high temperature radiation will cause rapid asphalt aging,and the bond strength between asphalt and aggregate as well as deformation capacity decline.The alternating effects of rain and high temperature make external conditions of asphaltpavement instantly change, and a large temperature difference between inside and outside.Thus, micro cracks will appear, which make water invade internal road easily and roaddamage accelerate. Therefore, in order to accurately assess the combined effect of rain,temperature and radiation on asphalt pavement, and reveal the mechanism of the damage,new test methods and analytical methods are needed.Our study was funded by the National Natural Science Foundation Project "Theasymptotic properties analysis of asphalt pavement based on digital image processingtechnology"(51278222) and the National High Technology Research and DevelopmentProgram (863Program)"Research on road disaster parameter monitoring and identificationof early warning system in the seasonal froze zone"(2009AA11Z104). In the study, damageevolution mechanism and damage detection methods of asphalt mixture under the effect ofwater-temperature-radiation cycles have been systematically studied. The detailed researches are as follows:1．Response surface methodology method (RSM) was introduced to comprehensivelyoptimize design of asphalt mixture molding process with optimal value of pavementperformance as the goal. The single-factor tests were firstly conducted to assess the affect ofthe key factors on the asphalt pavement performance. Then the response surface modelsbetween each factor and pavement performance parameters were established based onBox-Behnken design theory. At last, the analytic hierarchy process (AHP) was applied todetermine weights distribution of each factor, and the optimal values of each factor andpavement performances was obtain. After comparing the performance of specimen made byspecification method with by RSM molding method, the road performance of specimenmade by RSM molding method obviously outperforms the molded specimens made byspecification method, with better flexibility, logicality and predictability.2．Using the indoor water-temperature-radiation cycles test to simulate the integratedenvironmental effects of rain, high temperatures and intense radiation, it can more practicallyand comprehensively reflect the damage caused by water-temperature-radiation cycles. Byanalyzing the changes of the structure parameters, pavement performance and the basicindicators of recycled asphalt under the action of water-temperature-radiation cycles, thedamage characteristics and damage mechanism of different graded asphalt mixtures can berevealed. In order to quantitatively analyze the damage degree and rate for different gradedasphalt mixtures, Logistic damage model is introduced to describe the damaging process ofasphalt mixture under the action of water-temperature-radiation cycles. Grey relationalanalysis method is used to correctly evaluate the affect of water-temperature-radiation cycleson asphalt mixture performance, and the merit of controlling factors that affect the asphaltpavement performance can be ranked.3．Based on injury and reliability theory, multivariate statistical Weibull model ofasphalt mixture damage evolution is constructed at the macro representation level under theaction of water-temperature-radiation cycles, and the corresponding algorithm is designedfor parameter estimation and optimization. Shape factor, scale factor and gradient factor ofasphalt mixture damage evolution model are used to assess the failure characteristics of each point inside asphalt mixture, the resistance of internal point to external adverse conditions,and the differences of damage development among different parts. Thus, the damagecharacteristics and evolution rule for different graded asphalt mixtures under the action ofwater-temperature-radiation cycles are obtained.4．CT scanning technology is adopted to obtain the microscopic images of asphaltmixture at different stages of water-temperature-radiation cycle test, and digital imageprocessing technology is used to analyze the internal voids deformation of asphalt mixture,property changes in the expansion process, and fractal properties of images. Grey pixeldifference analysis method is applied to extract the image alignment, effectively avoiding theaffection of human factors and systematic errors when extracting sectional images of asphaltmixture, which improves the comparability of the images before and after the damage. Shapeparameters of cross-sectional images were used to quantitatively describe four stages of theinternal void, which are formation, development, connectivity, and dissemination, reveal theevolution rule of void property inside asphalt mixture in the process of water-temperature-radiation cycle. Fractal method can effectively describe the cross-sectional void imageproperty of asphalt mixture, and variation of the fractal dimension can reveal the evolutiondirection and property of cross-sectional void in the process of water-temperature-radiationcycle.5．Ultrasonic detection method can quickly evaluate the damage state of dense gradedasphalt mixture after the action of water-temperature-radiation cycles and effectively predictthe damage degree. Firstly, the changes of acoustic parameters, such as ultrasonic waveform,amplitude and frequency, etc., are used to define waveform aberration rate, amplitudeattenuation degree and frequency attenuation degree to make a preliminary quantitativejudgment on dense graded asphalt mixture damage degree after the action ofwater-temperature-radiation cycles. Then, based on grey theory, Neural network method andsupport vector machine theory the regression models for prediction between ultrasonicvelocity and damage coefficient are, respectively, established in conditions of differenttemperatures and different water content. The model is also optimised according to differentconditions. It is found that support vector machine regression prediction method possesses favorable accuracy and stability, and strong generalization ability. It can accurately reflectthe relationship between ultrasonic velocity and damage coefficient. Therefore, this methodcan rapidly evaluate the damage state of asphalt mixture with strong practical significance.