Study On Water Damage Mechanism Of Asphalt Mixture In Multi-factor Environment Of The South Coast

Under the influence of high temperature and humidity in summer,micro freeze-thaw in winter,salty and multi-factor environment,the asphalt pavement and asphalt concrete pavement of bridge deck are prone to water damage diseases such as falling particles,looseness,potholes and crowding deformation in the early service period,which seriously affects the service quality and service life,and increases the maintenance cost.Based on the research on recycling and industrialization technology of recycled asphalt pavement materials(201419),which is a scientific and technological project of Ningbo Transportation Committee of Zhejiang Province,and based on the characteristics of multi-factor environment in the south coastal area,this paper takes asphalt mastics and asphalt mixtures as research object,and explores the water damage mechanism of multi-factor environment on asphalt mixture from a multi-scale perspective.The research results can provide theoretical basis and data support for the selection and optimization design of asphalt mixture material composition in the south coastal saline area,and provide reference for the maintenance of asphalt pavement and asphalt concrete pavement of bridge deck during the service period.The main research contents are as follows:Basic performance test,Fourier transform infrared spectroscopy(FTIR),gel permeation chromatography(GPC)and atomic force microscope(AFM)technology were used to test samples of the based asphalt mastic and SBS modified asphalt mastic.The results show that the water,chloride and sulfate test environment and increased numbers of dry-wet and freeze-thaw cycle(DW-FT)all promote the association between the molecules of the asphalt mastics,and enhance the intermolecular interaction,resulting in the increase of sulfoxide(Is=o),aromatic functional group index(IAr),and fatty chain index(IB,a)And butadiene index(Ic=c)decreased.the molecular weight distribution of asphalt mastics moved to the macromolecular direction,the weight average molecular weight and dispersion increased significantly,and the roughness index Ra and Rq decreased.The corresponding macroscopic performance is that the penetration and softening point increase,the ductility decrease,the high-temperature stability of asphalt mastics was improved,and the low-temperature performance was reduced;the growth rate of Is=o of based asphalt mastics was higher than that of SBS modified asphalt mastics,and its resistance ability of the salt corrosion was lower than that of SBS modified asphalt mastics.The correlation analysis and grey entropy correlation analysis show that the chemical indexes,surface roughness and basic properties of asphalt mastics have great correlation.It is recommended that the Is=o index would be used to characterize the aging degree of asphalt mastics under the action of high temperature and humidity in summer and micro freeze-thaw salt environment in winter.Dynamic shear rheometer was used to analyze the viscoelastic characteristics,high temperature stability and medium temperature fatigue characteristics of asphalt mastics during salt erosion "DW-FT" cycle test.Compared with based asphalt mastics,the SBS modified asphalt mastics had the better high temperature stability and resistance to salt erosion "DW-FT' aging.Compared with traffic load,the increase of salt erosion "DW-FT" cycle has less effect on the fatigue life of the mastics.Correlation and grey entropy correlation analysis show that the Is=o index and LMS%are the main factors affecting the high-temperature stability of the asphalt mastics,and the chemical composition of the asphalt mastics had a significant impact on the macroscopic mechanical behavior.The surface free energy parameters of the asphalt mastic and aggregate were tested by the Wilhelmy hanging plate method and the lying drop method.Based on the surface free energy theory,van der Waals theory and Lewis acid-base theory,the adhesion work,stripping work and water stability evaluation indexes of them were calculated.The results show that the addition of mineral powder was increased the hydrophilicity of the based asphalt,and the effect on the hydrophilicity of the SBS modified asphalt was unknown.With the increase of the number of salt erosion"DW-FT" cycles,the adhesion work of the asphalt mastics and aggregates system were decreased,the stripping work of the asphalt mastics and water and aggregate system were increased,and the water stability evaluation index(ER2)were decreased.The adhesion the between SBS modified asphalt mastics and limestone aggregate were the best,and the resistance to water damage of them were the best.By using CT scan and digital image technology,combined with the water stability and splitting fatigue test of the SMA-13 asphalt mixture,the damage mechanism of salt erosion "DW-FT" of the mixture was explored by analyzing the correlation between macroscopic characterization index and microscopic observation index of the water stability.The results show that:with the increase of the number of salt erosion "DW-FT" cycles,overall porosity of the CT scan and measured porosity of the mixture specimens were tend to increase,and the splitting strength,TSR and fatigue life were tend to decrease,the anti-fatigue performance of the asphalt mixtures were weakened and the stress sensitivity were enhanced.Water stability of macro representation index and micro view index correlation analysis showed that,it is reasonable to use the index of Ic=c and LMS%to characterize the aging effect of SMA-13 asphalt mixture,It is feasible to use the surface energy index of ER2 to evaluate the water stability of mixture.The order of the influence of test environment on the performance of asphalt mastics and mixtures were:sulfate environment>chloride environment>water environment.