Research On The Mechanism And Prevention Technologies Of Water Damage In Asphalt Pavement Under Spring Thawing Environment

In season frozen region,pavement diseases tend to be concentrated outbreak at spring thawing season.This paper was funded by the national natural science fund project “Research on the key technology of asphalt pavement water damage based on oil stone consolidation enhanced and improving of the mixture overall performance” and the project of Heilongjiang province “Research on oil-stone interface adhesive technology based on the stone surface modification”.The damage mechanism and control technology of asphalt pavement water damage were studied under the special climate characteristics of spring thawing conditions.This research can provide theoretical and technical support for pavement structure design and construction in season frozen region.The main contents of this paper are as follows:(1)Moisture diffusion will influence the properties of asphalt binder in spring thawing condition.Based on the molecular diffusion theory and the asphalt binder desorption theory,the property developing law of asphalt membrane was studied under freezing-thawing cycle.Firstly,asphalt membrane samples were made to suffer freezing-thawing cycle.Then a variety of tests were finished to analyze the changing law of asphalt properties.After several freezing-thawing cycles,the properties of asphalt decrease,silane silica can slow down this trend.For the asphalt with more sulfur,the changing of sulfoxide group S=O can be used to evaluate the aging degree of asphalt under freezing-thawing cycle.The TG experiment shows that the modified material has good dispersion in the asphalt.Ts and Tp can be used to compare the thermal stability of modified asphalt,and Me for the dispersible uniformity of modified material.(2)The relationship between the moisture content and the shearing strength of the asphalt-aggregate interface was determined through test method designed by ourselves,and the effect of temperature and modified material were considered seriously in this research.This method can also be used to study the relationship between the tensile strength and moisture content of interface.The method can replace the traditional boiling method well.The study of asphalt aggregate adhesion can be changed from qualitative evaluation to quantitative analysis.The regression equation of shear strength and interface moisture content was obtained by fitting the experimental results.The shear strength decreases significantly as the interface water content increases,especially when the temperature is higher.(3)The mechanism of the pumping suction and scouring phenomenon for asphalt pavement was studied.The unsaturated and saturated pore models were established to simulate the pavement scouring phenomenon from meso level.Then the pavement pumping suction phenomenon was simulates and analyzed based on the Biot porous media theory.Finally,pore water pressure was measured on the actual pavement surface.The results of scouring simulation show that the pore water pressure and velocity are positively correlated with the speed of the wheel load,and the water pressure of unsaturated pore is a little larger than that of saturated model.The pumping suction is the main cause of water damage under lower vehicle.When the speed is fast,the positive peak of the pore water pressure is superimposed by the water pressure caused by dynamic water scouring and the pumping suction.The long term action of these two modes will accelerate the development of water damage.(4)Freezing-soaking-scouring specimen processing method was designed to simulate the spring-thawing climatic characteristics acted on the asphalt pavement.The damage law of the specimens can be found in this environment.The effect of the freezing cycle on all aspects of asphalt mixture properties is most significant.The scouring cycle has a larger impact on the durability than the soaking cycle,and it has the opposite characteristics for the water stability and high temperature properties.Freezing and scouring have the highest correlation degree with durability,while soaking has the highest correlation degree with high temperature properties.In addition,the Logistic judgment model was used to study the damage process which can describe the damage degree and velocity of the road material properties.(5)The formation law and development mechanism of water damage in spring thawing environment were analyzed and discussed.Interface consolidation and overall structure performance were found as two key factors to the prevention of water damage.In combination with respective advantages of silane silica and silane coupling agent,the modified asphalt mixture was designed which can resist the water damage well.In addition,this chapter introduces the theory of fuzzy comprehensive evaluation to establish a comprehensive evaluation system for the whole properties of the mixture,so that we can understand the properties of modified mixture clearly,and this also can make it easy for decision makers to choose suitable type for practical application.