| Carbon fiber has entered the vision of many fields of researchers for its excellent performance.In the construction field,carbon fiber can greetly improve performance as a reinforcing material mixed with cementitious materials.Carbon fiber reinforced cementitious materials have played an increasingly important role in construction projects.It is helpful to develop a kind of repairing and reinforcing material with stronger applicability than epoxy resin.The purpose of this paper is to provide a theoretical basis for strengthening reinforced concrete members with carbon fiber cementitious composites as binders.This paper will analysis the physical behavior,work properties,mechanical performance,uniaxial compressive stress-strain curve,maximum interfacial bonding force with old concrete,micro-structure and macro-properties of carbon fiber reinforced cementitious materials Through a combination of physical experiment and theoretical analysis method,.Besides,the reinforced concrete beams are strengthened by using the optimized carbon fiber reinforced cementitious materials as inorganic binders bonding carbon fiber cloth and fiber braided mesh.The failure process and menchanical properties of the strengthened beams are studied by experiments to verify the feasibility of carbon fiber cementitious materials as inorganic binders.The main conclusions and innovative achievements are as follows:(1)Carbon fiber reinforced cementitious composites have lighter weight characteristics than the baseline group cementitious composites due to the fact that the addition of short carbon fibers.Its lightweight characteristics are conducive to popularization and application.In addition,the fluidity of CFRP cementitious composite paste is much lower than that of the reference group cementitious paste,and the loss of fluidity with time is slightly smaller than that of the reference group cementitious paste.(2)The flexural strength of carbon fiber cementitious material prism can reach three times of the reference group cementitious composite,and it is positively correlated with the content of fiber.The compressive strength of the cube after fracture is slightly higher than that of the reference group,and increases first and then decreases with the increase of fiber content.The influence of water-binder ratio on carbon fiber cementitious composites is similar to that of ordinary cement mortar,and has a negative correlation.The influence of fiber length on the flexural strength and compressive strength of carbon fiber cementitious composites is small when medium and short fibers are selected.(3)The change of uniaxial compressive strength of carbon fiber cementitious material prism with water-binder ratio,fiber content and fiber length is similar to that of cube.The compressive modulus of elasticity is slightly smaller than that of base group cementitious composite.The ultimate compressive strain is positively correlated with compressive strength and the carbon fiber reinforced cementitious materials show good toughness in the process of compressive failure.The uniaxial tensile strength is mainly affected by the content of carbon fibers.The more the content of fibers,the greater the uniaxial tensile strength of the test block,and it can reach 2-3 times of the reference block.(4)In the micro-morphology of carbon fiber cementitious materials,on the one hand,the fiber fills the voids,on the other hand,it connects the matrix to enhance the strength of the test block.Through a series of micro-structure analysis,it can be seen that the effect of short carbon fibers on the properties of carbon fiber cementitious composites is far greater than other factors.The experimental results of micro-structure and macro-performance can be mutually confirmed.(5)The maximum interfacial bonding force between the carbon fiber cement matrix composites and the deteriorated old concrete in the simulated environment of coal mine is greatly affected by the deterioration period of the old concrete.The environmental impact coefficient obtained by linear regression of the test results can be used to establish the maximum bonding force model.The theoretical value obtained by the model has little error with the experimental value.(6)The ultimate bearing capacity of reinforced concrete beams degraded under the coupling action of coal mine environment and static load can be increased by about 20%with CFRP as binder,and the failure mode of the reinforced beams has changed.The crack generation and expansion are restrained during the failure process,which verifies the feasibility of this kind of material as binder strengthening member.This paper has 46 figures,40 tables,81 references. |
