Preparation And Properties Of Overlay Repair Mortar For Denudation Layer Of Concrete Pavement

In the cold saline-alkali areas of our interior,the problem of concrete pavement denudation is particularly prominent due to the synergistic effects of salt erosion,freezing and weathering.If the eroded pavement is not repaired in time,it will cause structural damage to the concrete pavement and affect its service life.Therefore,to solve the engineering problem of the concrete pavement prone to denudation and destruction in cold and saline areas,a new concrete pavement repair material is developed to suitable the environment,which is not only the technical need of the concrete pavement repair in cold and saline-alkali areas,but also has important guiding significance for the construction of the new concrete pavement project.This topic applies the principle of composite modification of material to develop a corroded concrete pavement material,which can suitable for the environment of cold saline-alkali area-mortar for overhaul repair,the concrete pavement overlay repair mortar is prepared with silicate cement,dihydrate gypsum,magnesium oxide,UEA expansive agent,basalt fiber.The surface repair mortar strength,cleavage resistance and deformation performance and freezing-thawing resisting performance were studied by orthogonal test,single factor test and contrast test method.The main work contents and conclusions are shown as follows:(1)The addition of MgO,UEA and dihydrate gypsum expansion agents will play a corresponding role in the shrinkage of concrete pavement repair mortar.Among them,the addition of 6%MgO,4%dihydrate gypsum and 10%UEA can make mortar expand respectively,without dry shrinkage.In contrast,under the condition of 6%MgO,its expansion and shrinkage values are relatively stable.During the repair process,no self-stress is generated due to expansion,and no secondary cracks are generated due to shrinkage.(2)When the mortar set ratio is 40:60,the ratio of basalt fiber to diameter is 9mm,the content of basalt fiber is 0.5%,and addition of gypsum is 4%,the mortar has the smallest shrinkage rate and good volume stability,which is most suitable for using as mortar for concrete road mask surface repair.(3)The study of silane coupling agent to enhance the bonding performance of the new and old interfaces of concrete pavement shows that adding silane coupling agent to the repair mortar can significantly improve the strength of the repair mortar,and then improve the strength of the repair mortar.Among the three silane coupling agents kh-550,kh-560 and kh-570,kh-550 had the best enhancement effect.Compare with the benchmark specimen without coupling agent,the flexural strength at 3 days improved 51%,and the compressive strength at 28 days improved 32%.For the splitting tensile strength,the splitting tensile strength with kh-560 silane coupling agent is significantly improved,which is 140%higher than that of the benchmark specimens.Therefore,it is more appropriate to choose kh-560 silane coupling agent as the interface adhesive of the concrete road mask surface repair mortar.(4)The quick freeze-thaw cycle test of repair mortar shows that the mass loss rate and the dynamic modulus loss rate decreased rapidly after 125 times,while decreased slowly in 0-75 times.The amount and type of expansion agent have the greatest influence on the dynamic elastic modulus of the repair mortar.Because of the expansion agent hydration products of ettringite,calcium hydroxide and magnesium hydroxide crystal,the mortar generated matrix expansion stress in advance,and then result the generation of crack,which will not only reduce the cover face repair mortar strength,but also lead to the freeze-thaw cycle in the process of mortar dynamic modulus of elasticity loss rate was accelerated.The content and the ratio of length to diameter of basalt fiber have a great influence from 100 to 175 times.The ratio of slurry set is 40:60,the content of basalt fiber is 0.5%,the ratio of basalt fiber length to diameter is 9mm,and the type and content of expansion agent is 4%of gypsum.The quality loss rate and moving modulus loss rate of the surface covering repair mortar prepared by the expansion agent are both small,which is suitable for the surface covering repair mortar of concrete road in cold areas.