| Highway mileage has been increasing year by year with continuous development of transport infrastructure construction in China.Asphalt pavement is widely used in the construction of road for its excellent driving comfort and construction convenience.Mineral aggregate is the main component of asphalt mixture and its properties directly affect the performance of asphalt mixture.Numerous researches have been done in China and abroad to analyze the relationship between properties of aggregate and performance of asphalt mixture.However,the relationship remains unclear because of aggregates' irregular geometry and its random distribution in mixture.In addition,the natures of mineral aggregate are usually tested by indirect methods which can not intuitively reflect the real characteristics.Therefore,in order to accurately analyze the influence of mineral aggregate's nature on performance of asphalt mixture,new test technologies and analytical methods are needed.This paper was developed combined with the Project supported by National Natural Science Foundation of China "Investigation on anisotropic properties of asphalt mixture based on digital image processing technology" and the Project supported by Doctoral Fund of Ministry of Education of China "Research on the creep damage mechanism of asphalt mixture based on digital image processing technology ".Firstly,the physical and chemical properties of filler and the morphological characteristics of coarse and fine aggregate were evaluated.Then,the relationships between properties of mineral aggregate and viscoelastic performance of asphalt mixture were investigated from three layers,that is asphalt mortar,asphalt sand and asphalt mixture,according to the mortar theory.Finally,the simplex lattice design method was used to obtain the optimal value morphological parameters of coarse and fine aggregate considering the high and low temperature viscoelastic properties of mixture.The specific works carried out in this paper are as follows:1.Considering the different effects of filler,fine aggregate and coarse aggregate on performances of asphalt mixture,the physical and chemical properties of filler and the morphological characteristics of aggregate were tested and analyzed respectively.Firstly,the microscopic morphology,specific surface area,mineral crystal and particle size distribution of different fillers were tested by scanning electron microscopy,specific surface area analyzer,X-ray diffractometer and laser particle size analyzer to compare the differences of physical and chemical properties and microscopic morphology of different fillers.Then,two-dimensional digital images of coarse aggregates and fine aggregates were captured by scanner and stereological microscopy respectively.The aspect ratio,roundness,angularity,erosion dilation ratio and fractal dimension of coarse and fine aggregates were obtained through digital image processing technology.And the distribution laws of aggregates' morphological characteristics were analyzed by statistical analysis.2.The influence of filler's content and physical and chemical properties on performances of asphalt mortar were systematically analyzed considering the indefinite relationship between properties of filler and performances of asphalt mortar.Firstly,the basic and viscoelastic properties of asphalt mortar with different content of limestone and diatomite were evaluated by penetration,softening point,viscosity,force ductility,dynamic shear rheological and bending beam rheological tests to analyze the relationship between the content of filler and the performances of asphalt mortar.Then,performances of asphalt mortar with same content of limestone,hydrated lime,fly ash and diatomite were evaluated by viscosity,softening point,force ductility and medium temperature dynamic shear rheological tests to investigate the effects of different filler on asphalt mortar at high and medium temperature.Furthermore,the correlation between physical and chemical properties of filler and performances of asphalt mortar were analyzed by gray correlation analysis method.The influential degrees of filler's characteristics on performance of asphalt mortar were determined and the most influential property of filler on asphalt mortar was identified.3.Influences of aggregate morphology on viscoelastic properties of asphalt sand and mixture were analyzed based on Burgers model.Firstly,composite roundness,composite angularity and composite erosion dilation ratio were proposed to characterize the morphological feature of mixed aggregate in consideration of the variability of aggregates' morphological characteristics with different particle sizes.Secondly,the mixing proportions of different aggregates were designed by simplex lattice design method,and thus aggregates with different morphological characteristics were obtained.Thirdly,the asphalt contents of asphalt mortar and mixture were determined by estimation method to eliminate influence of factors except aggregates on high temperature viscoelastic properties of asphalt mortar and mixture.Finally,the Burgers model was used to identify the viscoelastic parameters of asphalt mortar and mixture.The relationship between composite roundness,composite angularity and composite erosion dilation ratio of coarse and fine aggregates and Burgers model parameters were investigated by regression analysis to evaluate the effect of aggregates' morphological on viscoelastic properties of asphalt sand and mixture.4.The conversion between creep compliance and relaxation modulus was realized by Prony series and Laplace transformation.The influence of aggregate morphology on low temperature relaxation of asphalt mortar and mixture were furtherly analyzed based on the transformation.Firstly,the creep compliance of asphalt sand and mixture were obtained by the low-temperature bending beam creep test and converted into relaxation modulus by Prony series and Laplace transformation.Then,the logarithmic transformation of relaxation modulus with time curve was carried out.The transformed data was analyzed by regression analysis and the regression slope was used to evaluate the change rate of relaxation modulus.Moreover,the relationship between the change rate of relaxation modulus and aggregate morphological characteristics were investigated.In addition,considering the inverse influence of aggregates' morphology on high temperature creep and low temperature relaxation,the creep and relaxation parameters were used as responses of simplex lattice design to optimize the mixing proportion which take into account both high and low temperature viscoelastic properties of asphalt mixture.The corresponding composite roundness,composite angularity and composite erosion dilation ratio of aggregate could be calculated according to the aggregate mixing proportion. |
PDF Full Text Request