Research And Application Of Ultra High Toughness Concrete Functional Gradient Composite Structure

The performance of concrete not only has an important impact on the performance of the structure,but also has a direct impact on structural safety.However,a large number of engineering practices shows that this single-layer structural design cannot meet the service requirements.The probability of occurrence of concrete structure disease is increasing especially in complex stress environment.The reason is that the inherent brittleness of concrete materials leads to lower structure bending strength and crack resistance.Therefore,we need designing material-structural combining concrete structure to improve the service performance of traditional single-layer design.Based on the Young Scientist Training Program of Jiangxi Province(Project ID:20142BCB23012)and major engineering projects of Department of Transportation Jiangxi Provincial(Project ID: 2016C0008).According to the concept of functional / structural integration design,a kind of ultra-high toughness concrete(UTC)with excellent mechanical properties and simple preparation process was developed.In this paper we designer a new type of ultra-high toughness concrete functionally graded composite structure and explored the application of the new structure in practical engineering The main work and research results includes:1.In this paper the concept of functionally graded material is introduced to optimize the concrete monolayer structure.In order to meet the different requirements of different parts of the material,and the different requirements of different parts of the structural stress performance,Ultra-high toughness concrete is applied to the weak parts of key parts.The design concept of UTC function gradient combination structure is established.At last we developed the UTC function gradient combination structure design principles and preparation methods.2.Based on the maximum tight packing and fiber reinforced toughening theory,a new type of ultra-high toughness concrete was developed through conventional process and curing conditions.The experimental results show that UTC has high compressive strength,bending resistance and splitting tensile strength which reaches 130 MPa,30MPa and 10 MPa respectively.The impact resistance and bending toughness of UTC increased by 2.6 times and3 times when compared with C50 concrete and ordinary steel fiber reinforced concrete.3.By changing the thickness of the UTC functional composite beams,the law of the bending toughness of the UTC functional gradient beam with UTC layer thickness is studied.The results show that the flexural capacity of UTC functionally graded beams decreases withthe thickness of UTC layer.For example,the ultimate bearing capacity increases by 50% to450 kN when the thickness increases from 0.16 h to 0.5h.However,the bending capacity of the composite beam is slowed when the UTC layer exceeds 0.5h.The toughness and crack resistance of the composite girder are increased with the increase of the thickness,especially when the thickness is about 0.4h-0.6h.For example,the bearing capacity with the 0.2mm crack width increases by 100% when the thickness increases from 0.33 h to 0.5h;The increase is slowed when the thickness exceed 0.6h.Considering the influence of the relative thickness of the super high toughness concrete layer on the development of the crack and the overall bending resistance of the beam,combined with the economic cost of the project,the optimal thickness of the ultra-high toughness concrete in the design of the multi-high toughness concrete functionally graded composite structure is 0.4h?h?0.2hf.4.The application of UTC function gradient combination structure in the wet joint of the simply-supported continuous beam bridge is explored.The research on the key technology of the preparation of ultra-high toughness concrete and the function gradient combination of ultra-high toughness concrete are carried out.The engineering practice shows that the interface with high toughness concrete functionally gravitational interface has good bonding performance,great practical value and good economic benefit.