Research On The Morphological Characteristics Of Mineral Powder And Its Influence On The Properties Of Asphalt Mastics

As one of the main component of asphalt mastic,the properties of mineral powder will directly affect the performance of asphalt mastic,and then have a certain impact on the mechanical properties of asphalt mixture.In order to study the properties of mineral powder and its relationship with the performance of asphalt mastic,scholars from various countries have carried out a lot of work.However,the mineral powder has small particle size and tendency to aggregate,it is difficult to quantitatively characterize the morphological characteristics of mineral powder,which makes the relationship between the morphological characteristics of mineral powder and the performance of asphalt mastic is still unclear.At present,studies on the morphological characteristics of mineral powder are mostly based on scanning electron microscope imaging technology,while it is impossible to quantitatively describe its different quantitative indexes.The present paper quantitatively characterizes the morphological characteristics of mineral powder by using the self-developed sample slide method and digital image technology.Besides,the influence of the morphological characteristics of mineral powder on the performance of asphalt mastic based on the basic properties of mineral powder is also studied.Twelve kinds of mineral powder were prepared via the same grinding process and sieving method,and their basic properties were tested.For any lithologic mineral powder,the hydrophilic coefficient is less than 1.As the particle size decreases,the density and porosity decrease gradually,and the specific surface area increases gradually.Compared with basalt powder,limestone powder（with higher Ca O content）and granite powder（with higher Si O₂content）particles have more abundant folds and more complex microstructure.A method of uniform distribution of single particle was created,and the morphological characteristics of mineral powder were quantitatively characterized and evaluated by means of digital image technology.The results show that,for any lithologic mineral powder,the contour shape becomes more regular,and the angularity and surface texture become less abundant with the decreasing particle size.For the mineral powder of the same particle size range,granite powder has a more contour shape,richer angularity and surface texture than limestone powder and basalt powder.The shape factor,angularity index AI₁ and fractal dimension can better reflect the sensitivity of lithology and particle size range of the mineral powder to the contour shape characteristics,the angularity characteristics and the surface texture characteristics.Based on the basic properties of mineral powder,the influence of the morphological characteristics of mineral powder on the interface performance between mineral powder and asphalt binder,and their relationship were studied.The results show that the arrangement and accumulation of limestone powder and granite powder and their surface morphology are not favorable to the rapid infiltration of high-temperature asphalt compared with basalt powder.The interface area is distributed with tiny holes or fine pores presenting more folds and bulges.When the asphalt binder and volume fraction are constant,the larger the specific surface area of mimeral powder per unit volume,the lower the Si O₂ content,the more regular the contour shape,and the less the edges and angles,thus the better the interface performance of mineral powder and asphalt binder,while the surface texture characteristics of the mineral powder have no significant influence on the interface performance of mineral powder and asphalt binder.The interface performance of mineral powder and asphalt binder are well correlated with the specific surface area and contour shape of mineral powder,but poorly correlated with other properties of mineral powder.The fractional derivative dynamic viscoelastic model is constructed.The fitting parameters are determined by the fitting analysis of the dynamic shear rheological test results of asphalt mastics at different test temperatures,and their physical significance is clarified.The correlation analysis between the composite morphological characteristics of mineral powder and the fitting parameters was also carried out.The results show that the fractional derivative dynamic viscoelastic model can accurately and reliably describe the dynamic shear rheological properties of asphalt mastics at different test temperatures.Asphalt mastics prepared with limestone powder with more regular contour shape and richer angularity or granite powder with richer angularity and surface texture help to improve its resistance to deformation at high temperature.The temperature sensitivity of asphalt mastics has a good correlation with the composite contour shape and composite angularity characteristics of mineral powder,but has a poor correlation with the composite surface texture characteristics of mineral powder.The fractional derivative burgers creep damage model is constructed.The fitting parameters are determined by the fitting analysis of the low-temperature bending creep stiffness test results of asphalt mastics.The damage factor and relaxation time are used as the indexes to evaluate the low-temperature creep damage behavior and low-temperature stress relaxation capacity of asphalt mastics,respectively.Besides,the correlation analysis between the composite morphological characteristics of mineral powder and the damage factor and relaxation time was constructed.The results show that the fractional derivative burgers creep damage model is in good agreement with the low-temperature bending creep stiffness test results of asphalt mastics.In the early stage of creep loading,the composite contour shape characteristics and composite angularity characteristics of limestone powder or the composite contour shape characteristics and composite surface texture characteristics of granite powder paly a major role in the damage factor.However,in the middle and later periods of creep loading,the composite contour shape characteristics and composite surface texture characteristics of limestone powder or the composite angularity characteristics and composite surface texture characteristics of granite powder play the key role in the damage factor.During the creep loading process,the relaxation time has a poor correlation with mineral powder composite contour shape characteristics,but has a good correlation with mineral powder composite surface texture characteristics.