| Geopolymer cementitious materials have excellent durability and resistance to acid and salt erosion,and have great application potential in the surface protection of marine and hydraulic concrete,but their brittle nature limits their large-scale application.Fiber composite can effectively improve the toughness of geopolymer materials,but the microscopic mechanism of fiber geopolymer reinforcement and toughness is still unclear,and it is difficult to guide the performance optimization research of composite materials.In this paper,the orthogonal test method is used to optimize the formula based on the existing formula,and through the optimization of curing conditions and silicone modification,the problem of material curing and cracking is solved.XRD and FI-IR analysis show that the The amorphous structure of the mineral bonding material has undergone the polycondensation reaction of Si-O and Al-O.The best formula determined by the orthogonal test is: metakaolin: sodium hydroxide: water glass:water(mass ratio)=26:4.5:25:5,and the compressive strength of the corresponding material is 16.77 MPa.The prepared mineral bonding coating material has good bonding performance with the concrete substrate,and the bonding strength reaches7.98 MPa,and the fracture surfaces occur in the coating body and the concrete substrate respectively.The mineral bonding material toughened by high-strength and high elastic modulus PVA short fiber obtains good fracture toughness.The three-point bending test of the material with 2vol% fiber addition ratio reaches 13 MPa,and a significant quasi-strain-hardening effect appears.The deformation rate is 9%.According to related research,the converted ultimate tensile rate of the material reaches more than 3%.Through the analysis of the three-point bending deformation characteristics of the specimen and the force analysis of the specimen,it is found that the quasi-strain-hardening effect of the composite material originates from the multi-cracks in the material deformation process,which is manifested as the bridging effect of the fibers in the microscopic view.Under the combination of bridging force,fiber and matrix strength,the fiber will prevent the stress concentration at the crack tip,induce numerous micro-cracks in the brittle matrix,and avoid rapid growth and instability of the material along a single crack.The formation mechanism and microscopic analysis of the quasi-strain-hardening effect play an important role in material design.By designing the strength of the fiber and the matrix in the composite material system,and the interface force between the fiber and the matrix,a highly ductile mineral bonded material with greater deformation capacity will be prepared.Used as a surface protective coating for hydraulic concrete.By preparing the fiber-geopolymer composite material,it helps to improve the durability of the protective coating on the surface of hydraulic concrete. |
