Research On The Technology Of Small-particle-size And Ultra-thin Asphalt Overlay With Fuctions Of Drainage And Skid Resistance

Safety and comfort of vehicle driving is adversely affected by problems including cracking and insufficient skid-resistance security on the surface course,under the influence of heavy transportation after 3 to 5 years of service of asphalt pavement.However,there exist defects such as short life cycle and noise in current preventive maintenance methods.Consequently,a small-partical-size and ultra-thin asphalt overlay with function of drainage and skid-resistance is proposed in this research.Laboratory research and simulation verification are carried out from the aspects of binder selection,gradation composition design,performances,mechanical simulation analysis,drainage simulation and key parameters of construction.Firstly,taking the dynamic viscosity of 60℃≧10,000 Pa·s as evaluation index,four types of high-viscosity modified asphalt are prepared with selection of 70# matrix asphalt,SBS modified asphalt and two kinds of high-viscosity modifiers(Type I and Type II).The blending type and blending ratio are determined(SBS: type I = 86:14,SBS: Type II = 86:14)via the FTIR,DSR,60 °C dynamic viscosity test and physical properties.Simultaneously,two kinds of gradation types,the coarse type(PAC-1)and the fine type(PAC-2),are designed referring to the volume design method and the Bailey design method.Based on the two gradations,optimal asphalt-aggregate ratios of four asphalt mixtures are tested and analyzed by the leak test,the scattering test and the Marshall stability test,and thus the basic parameters of the four kinds of asphalt mixtures are obtained.Secondly,the high-temperature stability,low-temperature crack resistance,moisture resistance and dynamic modulus with different temperatures and load frequency are evaluated by the rutting test,low-temperature bending beam test,freeze-thaw split test and dynamic modulus test.The results show that PAC-1-II type(1 represents the gradation type and II represents high-viscosity modifier type)has the best performance,with the dynamic stability as high as 8,400 times/mm.PAC-1-I type is not as good as PAC-1-II type in performances,and PAC-2-I type and PAC-2-II type are the worst.Skid-resistance and drainage ability of four types of asphalt mixtures were evaluated by dynamic friction coefficient test,pendulum friction test,structural depth test and water seepage test.The results show that drainage performance and the skid-resistance under medium and high-speed conditions of PAC-1-I and PAC-1-II are better than those of PAC-2-I and PAC-2-II,but the skid-resistance is reversed at low-speed conditions.The water seepage coefficients of PAC-1-I,PAC-1-II,PAC-2-I,and PAC-2-II are 7230mL/min,7273mL/min,6857 mL/min and 6316 mL/min,respectively.Thirdly,the surface simulation models with different overlay thicknesses are established by ABAQUS(finite element software).The effects of load frequency,environmental temperature and overlay thickness are analyzed on the mechanical properties of various structural layers.Results show that increase in the overlay thickness is helpful to reduce the surface deflection and improve the stress condition of the underlying layer.Simultaneously,the drainage effects of pavement structure with different overlay thicknesses are analyzed by SWMM(storm flood management software).The drainage capacity indicators of 15 mm,20mm and 25 mm overlayers are 17.4 mm,23.2 mm and 29 mm,respectively.Finally,the effects of different compaction temperatures and compaction times on the scattering performance are analyzed by laboratory compaction tests.To insure the scattering loss of over 10%,the initial compaction temperature of PAC-1-I and PAC-1-II types should not be lower than 150 °C,and that of PAC-2-I and PAC-2-II should not be lower than 165 °C.To insure the target void ratio of over 20%,the laboratory compaction times of PAC-1-I,PAC-1-II,PAC-2-I,PAC-2-II are 53,59,50 and 50 respectively.The correspondence between laboratory and filed compaction work is established according to the principle of energy equivalence,which helps to determine a reasonable rolling group and guide the filed construction of test section.A theoretical reference can be provided for the design of ultra-thin asphalt overlay,which is helpful to select and optimize the group of construction temperature and rolling methods.