Research On Performance Damage And Deterioration Process Of Ultra-high Performance Concrete In Deicing Salt Environment

The pavement structure with cement concrete used in the cold regions of northern China has been subjected to the combined effects of freeze-thaw cycles and vehicle loads all the year round,but there is a large amount of Cl-in deicing salt,with the accumulation and infiltration of harmful ions,it will cause the deterioration of pavement concrete structure performance,steel corrosion and other phenomena,leading to the deterioration of pavement structure durability,and damage ahead of time.At present,the destruction of cement concrete pavement structure caused by deicing salt and the decrease of durability have become a major engineering problem in road engineering.After the ordinary cement concrete pavement is corroded,it will produce a large number of cracks,which will accelerate the destructive action of harmful examples.Therefore,reducing the occurrence and expansion process of cracks in cement concrete is an important way to improve the resistance of pavement structure to salt and freeze erosion,it is necessary to study high toughness cement-based materials for pavement structure.This thesis fully understands the erosion process of deicing salt to cement concrete pavement structure and the application progress of super high toughness cement-based composite materials at home and abroad,focusing on improving the toughness of cement concrete by using fiber and other materials,reduce cracking,in this thesis,a detailed experimental study is carried out on the mixture ratio design,working performance of fiber composite cement-based materials and the deterioration process of fiber composite cement concrete in salt-frozen environment and its failure process as continuous structure of bridge deck.The main research work includes:(1)study on the performance and tensile properties of fiber composite cement-based materials.The preparation method of fiber-cement composite was put forward through the changing process of fluidity and extensibility of cement-based composite under different water-binder ratio,fly ash content and fiber content,the compounding process and flow chart of the material were established.The tensile properties of fiber-cement-based composites are analyzed,and the effect of fiber on improving the cracking process of cement-based composites is revealed.(2)study on damage process of fiber reinforced cement concrete in deicing salt environment.The freeze-thaw failure process of fiber-concrete in deicing and salt environment was studied,and the appearance,mass loss and dynamic modulus loss of fiber-concrete were analyzed In this thesis,the effect of fiber-concrete resisting salt-induced damage is analyzed from microstructure,and the damage degradation model of fiber-concrete composite under salt-induced damage is established.(3)study on the cracking process of fiber-cement concrete composite deck pavement in deicing salt environment.In order to improve the effect of fiber-cement concrete composite used in bridge deck pavement under ice-salt environment,the tensile and flexural properties of fiber-cement concrete composite were studied by four-point bending test and numerical method,the excellent anti-cracking performance of fiber-cement concrete composite as bridge deck pavement is verified.