Research On Preparation Technology And Performance Experiment Of Fiber-reinforced Concrete With Ultra-high Toughness

Ultra-high toughness fiber-reinforced concrete is a new functional cement matrix composite,which is reinforced by synthetic fiber with medium content.After reasonable design,it can give full play to the reinforcement and toughness of fiber.Compared with ordinary concrete,it has super high toughness,extensibility and crack control ability.Ultra-high toughness fiber reinforced concrete has great potential in the fields of long-span concrete structure,reinforced concrete protective layer and bridge maintenance and reinforcement.If it can be reasonably applied,it is of far-reaching significance to improve the durability and safety of concrete structures.At present,the research on ultra-high toughness fiber reinforced concrete at home and abroad is still in its infancy,because the composition characteristics of its raw materials in mix proportion are obviously different from those of conventional concrete or mortar.Moreover,the mix ratio used in the relevant literature at home and abroad is also quite different,so there is a lack of authoritative engineering experience and standard guidance on the technical details of the preparation of this new type of concrete material at present.At the same time,because the mixture ratio of the material is low and the fiber content is high,how to use conventional equipment to ensure that the fiber is fully dispersed and improve the mixing efficiency is the premise to determine the molding quality of concrete,so finding a reasonable mixing process is also a key part of the material preparation technology.Considering that different actual requirements necessarily require different adjustments in the mix ratio,it is also necessary to understand the influence of the parameters and content of each raw material on the basic properties of ultra-high toughness fiber reinforced concrete,in order to carry on the purposeful design instruction to the material to meet the different use and the demand.Based on the project "Research on Key Technology and Application of Ultra-high Toughness Fiber Reinforced Concrete in Seasonal Freezing Zone",the preparation technology and basic properties of ultra-high toughness fiber reinforced concrete are studied in this pape,in order to further study the properties and application of the material,the main contents and conclusions of this paper are summarized as follows:(1)In this paper,the raw material composition of ultra-high toughness fiber-reinforced concrete and its function in concrete are analyzed,the basic design theory of this new concrete material abroad is summarized,and its preparation process is optimized and improved.Then the influence of the change of raw material parameters such as fiber type,fiber length,sand particle size and the content of each raw material on the construction performance and mechanical properties of concrete is taken into account,and dozens of mixture ratios are designed to carry out the trial preparation test.The reasonable range of raw material parameters and content was screened out,and the preparation method details of ultra-high toughness fiber-reinforced concrete were preliminarily clarified.(2)The basic mechanical properties of ultra-high toughness fiber-reinforced concrete at different ages,such as bending strength,compressive strength and compression resilience modulus,were tested.The test results show that the ultra-high toughness fiber-reinforced concrete can not only reach the strength order of ordinary C40 concrete,but also have higher compression ratio and lower elastic modulus,that is to say,it has higher toughness and deformation ability.In the process of different forms of failure test,the fiber effectively limits the rapid propagation of cracks,and the specimen still has a high residual strength after the initial crack,and concrete is no longer a typical brittle failure form.The security of the structure is improved.(3)The bending characteristics of ultra-high toughness fiber-reinforced concrete are studied,and the unique large deformation capacity and multi-joint cracking characteristics of the material are verified.The deformation and hardening process of ultra-high toughness fiber-reinforced concrete prepared in this paper is shown by the load-deflection curve of four-point bending test of thin plate,and the characteristics of each stage in the bending failure process are described.The bending toughness index of super high toughness fiber-reinforced concrete is calculated,and it is proved that the ultra high toughness fiber reinforced concrete prepared in this paper belongs to hardened material with high toughness bending deformation ability.