Study On Fracture Performance Of Nano-CaCO₃ Basalt Fiber Reinforced Concrete

With the acceleration of infrastructure construction in our country,the hydraulic engineering has developed rapidly,but the hydraulic concrete structure is affected by the load and the harsh natural environment,the surface erosion and abrasion,cracks and freeze-thaw damage are easy to occur,among which the cracks are the most important factors that affect the durability of hydraulic concrete structure,thus affecting the safety and durability of hydraulic concrete structure.Nano-CaCO₃ is a kind of nano-scale material,which can improve the internal structure of concrete and reduce the formation of harmful pores.Basalt fiber has high elastic modulus,high tensile strength and can effectively increase the crack resistance of concrete.Therefore,the fracture resistance of concrete reinforced by double-doped nano-CaCO₃ and basalt fiber is studied,it is of great significance to the durability and safety of hydraulic concrete structure.The main work of this thesis is as follows:1.The compressive strength and tensile strength of concrete containing 0%,1.5%,2.0%,2.5%,3.0% and 3.5% nano-CaCO₃ were tested at different ages of 3d,7d,14 d and 28 d,the results show that the compressive strength and tensile strength increase first and then decrease with the increase of nano-CaCO₃ content.The SEM analysis also proves that nano-CaCO₃ can improve the internal structure of concrete and promote hydration reaction,so as to improve the mechanical properties of concrete.2.Under the condition of determining the optimal amount of nano-CaCO₃,the basalt fiber with the length of 3 mm,6 mm,9 mm and 12 mm is added with the amount of 0.00%,0.05%,0.10%,0.15%,0.20%,0.25% and 0.30% of nano-CaCO₃,the influence of double-doped nano-CaCO₃ basalt fiber on workability,compressive strength,tensile strength,flexural strength and failure form of concrete is analyzed,which can reduce workability and increase compressive strength,tensile strength and flexural strength of concrete.3.According to the above mentioned mixture ratio of double-doped nano-CaCO₃ basalt fiber concrete,the preformed notched beam fracture test is carried out,and theP-CMOD diagram is drawn based on the double-K fracture model,it is found that the fracture of nano-CaCO₃ basalt fiber concrete is divided into three stages: crack non-expansion,stable expansion and instability expansion,double-doped nano-CaCO₃ basalt fiber,the initial fracture toughness and the unstable fracture toughness can be improved in different degree.The results show that when the length is 3mm and the content of nano-CaCO₃ is 0.20%,the effect of toughening and anti-fracture of nano-CaCO₃ concrete is the best.4.Based on the Monte Carlo method theory,a random aggregate model was established,and the fracture failure of concrete was simulated at the Meso level based on the traction-separation principle of cohesive elements,the feasibility of numerical simulation is proved.