Study On Stress Characteristics And Road Performance Of Joint Sealing Material On Cement Concrete Pavement

With the rapid development of road transportation industry in our country,the cement pavement is one of the main type of pavement structure,has been widely used in highway,urban road,airport runway and port road.In addition,based on the joint cement pavement,the joint sealing material are mainly used to seal the joints,so as to maintain the integrity,smoothness and water quality of the pavement,and improve the durability and service quality of cement pavement.However,under the repeated loading and environmental factors,the function failure of the seam material,caused the defects of cement pavement,such as fracture,dislocation and pumping mud,which seriously affect the service life and road performance of the cement pavement.In this paper,based on the results of numerical simulation calculation,the stress and deformation characteristics of the cement pavement sealing material are clearly defined.The polymer modified asphalt based sealant are developed to satisfy the requirements of the road performance and mechanical properties of the cement pavement,so that the sealant can better adapt to the working conditions of the cement pavement joints,to enhance the durability of sealing material and prolong the service life of concrete pavement.It is one of the great significance to promote cement pavement development and application better and faster.First,based on the finite element analysis method,the numerical model is established.In the static analysis,in view of the joint deformation,width,affected by the temperature difference and other factors,the deformation index of sealing material is proposed corresponding.The results show that when the load is completely applied to the sealing material,it is the most unfavorable position of the force for sealant;The improvement of elastic modulus and Poisson's ratio of sealant is helpful to improve the influence of pavement deflection and reduce the vertical displacement of the road;With the increase or decrease of temperature of the road surface,sealant principal stress will increase linearly or decrease linearly.The temperature difference will make the sealing material produced more principal stress in the horizontal,and make the sealant open amount larger,leading to debonding,cracking phenomenon and so on.And the deformation index of the sealant in horizontal direction is greatly influenced by the temperature change,so it should be the main reference object to reduce the temperature difference making sealant in an unfavorable state.Secondly,the dynamic response of the pavement structure under the action of moving load is studied,and the mechanical index of the sealing material is proposed corresponding.By comprehensive the research results of static and dynamic analysis,the optimum geometry size of cement pavement sealant is determined.The results show that compared with the static load condition,when the load is 200 KN,the tensile stress and compressive stress of sealant under the action of dynamic load are 1.3 times that of the static force,and the shear stress is 3.6 times that of the static force.The increase of driving speed will have a serious adverse effect on the force of sealant.When width of the joint is 10 mm and the depth ratio is 1:3,the stress state can be improved obviously.Then,in order to improve the performance of sealing material,polymer modified asphalt based sealant is prepared to meet the above deformation and mechanical indexes.Styrene-butadiene-styrene(SBS),shape memory polyurethane(SMPU)and organosilicon(OS)were first used to modify asphalt based sealing material respectively,and the joint material suitable for cement concrete pavement was prepared.The thermostability,compatibility,phase composition and element composition of the polymer modified asphalt based sealant were characterized.Results indicated that the addition of modifier can significantly improve the thermal stability of the asphalt,react with functional groups of asphalt with generating a new group,and make the modifier and asphalt have good compatibility which can be mixed evenly.With the addition of SBS and PU modifier,it can absorb some of the components in the bitumen and make changes in the content of the asphalt components so as to improve the asphalt performance.When the OS modifier is added to asphalt,there is no obvious change of chemical reaction,but the modification of asphalt is achieved through the process of physical blending.Among them,the shape memory PU sealing modifier of asphalt based material filler effect is best.It can observably improve the thermal stability and aging resistance of sealing material,which enhancing the durability of the sealing material.Finally,the road performance is investigated,such as the low temperature ductility,high temperature fluidity and elastic recovery of the sealing material,and the mechanical properties are tested,inspected the preparation of sealing material whether meet the sealing material stress characteristics in the early stage of the finite element analysis results.The results show that when the modifier is added into the asphalt,the pavement performance and mechanical properties of the modified asphalt will be improved well,and it can meet the requirements for the mechanical index of the sealing material proposed in the finite element analysis.When the polyurethane modifier with the amount of 8% is used as the modifier of the modified asphalt based sealant,its performance is far better than the other formulas,and the road performance and mechanical properties of modified effect for the polymer modified asphalt based sealant is best.Therefore,choosing 8% dosage of polyurethane sealing modifier as the cement pavement material best optimal formula,it can adapt to the road performance requirements of the cement pavement.It is one of the great significance to prolong the service life of sealing material,enhance the sealing effect of the sealant and improve the durability of the cement pavement sealing material.