| With the progress and development of science and technology,many environment dirty place,such as corrosion by chloride ion erosion and freeze-thaw cycles of ocean engineering,also need to construction of concrete engineering,this will put forward higher request for concrete structures,such as high durability,high permeability,etc to ensure that the structure of the use fixed number of year because of its traditional Portland cement setting time is longer than the other Early strength low reason cannot satisfy the demand of the special projects,such as road pavement maintenance engineering emergency maintenance construction engineering projects such as fast construction Sulphur aluminate cement with high early strength Good frost resistance and impermeability Such outstanding advantages as low alkali and durability good show broad prospects for development,but at the same time there are also setting time is shorter The late strength reduction The high cost problem Therefore,in order to make the sulfoaluminate cement more widely received,it is necessary to make reasonable adjustment to its own shortcomings based on the engineering properties.Relying on the research task of recovery technology of key load-bearing structure materials for rail transit under complex environment in the national key research and development program project,this paper studies the durability of sulfoaluminate cement-based composite materials under seawater freeze-thaw cycle coupling corrosion and draws the main conclusions as follows:(1)The water-binder ratio and sand-binder ratio were investigated by orthogonal test Beads content and air content for sulphur aluminate cement base fiber composite materials in seawater freezing and thawing coupling mechanics properties and durability of the environment,the results show that the material has high early strength and excellent corrosion resistance,frost resistance at the same time,the dosage of water-binder ratio,beads as the main influence factors,two factors mastic than with the change of air content on the performance also exist,but the i MPact is smaller Through the electric flux experiment,it can be found that co MPared with C40 ordinary concrete,the electric flux value of this material is very small,which proves that this material has excellent durability from the side.(2)Nano Si O2 to join the sulphur aluminate cement base fiber compound material mechanics performance and durability performance further ascension,but there is the optimal dosage and at the same time,the addition of nano-Si O2 can inhibit the sulphur aluminate cement base material flexural strength in the late fall phenomenon,most of the specimen surface after water freezing and thawing coupling corrosion almost no change,showed excellent durability,electricity Flux experiment also proves it from the side.(3)Microscopic analysis by SEM and EDS,the morphology of ettringite is mainly for the needle bar and short column,the sea water corrosion,freezing and thawing coupling structure cracks,but the structure of relatively dense,the addition of nano-Si O2 can improve physical and mechanical properties and durability of the repair material,the reason is that nano Si O2 in hardened cement paste established on the basis of the original grid New grid structure,ettringite crystal intertwined to form a more dense mesh structure,through SEM found that due to the low sulphur aluminate cement alkalinity,reactant few beads surface,and the addition of nano-Si O2 improved the interface transition zone,although after seawater corrosion after freezing and thawing coupling matrix part still appear crack,but co MPared with not mixing nano group,fracture has been greatly reduced,the slurry The bulk-aggregate transition zone is more co MPact,which indicates that the addition of nano-Si O2 improves the structure density.(4)According to the existing durability assessment standard of concrete structure(GB/T 51355-2019)and Matlab programming software,the life prediction of concrete structure under seawater freeze-thaw coupling corrosion environment was carried out,and the transmission process of chloride ion in cement-based fiber composite material was simulated by programming software.And compare the results with Fick’s second theorem,the results show that both high inosculation,Matlab programming is more in line with the actual environment,for the prediction of concrete in such an environment has great significance to the development trend of the chloride ion concentration,due to the different boundary conditions,Fick’s second theorem formula can’t to life prediction of concrete structures after repair,This paper uses the programming software and the genetic optimization algorithm theory to predict the service life of the repaired concrete structure.The results show that the service life of the repaired concrete structure can be improved to a large extent by reasonably cleaning the surface of the original concrete structure and supplemented by the repair material.(5)On the basis of the completed research,2-3 groups of optimal ratio with comprehensive performance were selected to conduct bonding experiments on C40 ordinary concrete structures corroded by seawater freeze-thaw coupling environment.The effects of different interface bonding forms and other factors on the tensile strength of interface splitting under the same roughness depth of grinding with nano-roughness content were studied Studies have shown that interface roughness is the most main factors that affect the bonding properties,increase the grinding depth is can improve the performance of adhesive but the main reason for the roughness increases,the same roughness,specific surface area increased interface helps to improve the tensile splitting strength,but the processing of the interface between the interface damage easily,cause microfracture,reason should be within the reasonable range,appropriate increase interface specific surface area,the nanomaterials have little effect on the bond strength at the later stage,and the effect on the bond strength at the early stage may be more obvious. |
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