Study On Basic Mechanical Properties And Crack Resistance Mechanism Of Basalt Fiber Reinforced Cement-based Composite

The cement-based composite material is a composite material composed of cement paste,mortar,concrete,etc.as the matrix,and fiber as the reinforcing material.The traditional concrete material is a discontinuous,non-uniform quasi-brittle material,and its internal defects will inevitably produce pores,micro-cracks and other defects,which restrict its wider application.After blending fibers,it can effectively suppress the development of cracks and greatly improve the working performance of concrete materials,but its structure and crack resistance mechanism are not yet perfect,so it is necessary to do further research on its crack resistance enhancement mechanism.This article uses a combination of theoretical analysis and experimental research to explore the factors and laws affecting the mechanical properties and crack resistance mechanism of basalt fiber-reinforced cement-based composites,in order to provide the necessary theoretical guidance for practical engineering applications.The main contents are as follows:(1)Based on the energy theory of fracture mechanics,analysis of the evolution of energy transfer during the entire process of crack initiation,appearance,expansion,and instability To prevent further crack growth.Combined with the theory of composite materials and the theory of fiber spacing,it is known that there is a reasonable combination of dosage and length-to-diameter ratio that allows basalt fiber composite materials to obtain better crack resistance.(2)Through the cube compressive and splitting tensile tests,study the influence of different basalt fiber content and length-diameter ratio on the compressive strength and splitting tensile strength.The test results show that the brittle failure of the test piece is significantly improved after the basalt fiber is added.When the fiber length is 6mm and the volume content is 0.1%,the compressive strength of the test piece peaks and is increased by 19.75% compared with the non-fiber content test piece;when the fiber length is 12 mm and the content is 0.2%,the test piece splits and tensile The strength is the largest and it is 13.8% higher than that of the non-fiber mixed specimen.(3)Through the fracture characteristics test of the three-point bending beamwith prefabricated cracks,the influence of different fiber content and length on the fracture performance was studied.From the test results,the cracking toughness and instability of the specimen after blending basalt fiber Fracture toughness,fracture energy and other fracture performance parameters have been improved to varying degrees.When the blending length is 12 mm and the blending amount is 1.0%,the fracture performance of the test piece is significantly improved.The full field displacement value provided by the Digital Speckle Correlation Method(DIC)can accurately obtain the length of the fracture process zone of the specimen under any load,and more intuitively understand the whole process of crack propagation in the fracture process zone.(4)Through the uniaxial direct tensile test of dumbbell-shaped specimens,the effect of fiber content on tensile properties was studied.The test results show that after the basalt fiber is added,the ultimate tensile strength and ultimate tensile strain of the test piece increase significantly,and when the dosage is 1.5%,the ultimate tensile strain is the largest and 0.023%.Based on the results of this experiment,a tensile constitutive model of basalt fiber-reinforced cement-based composites was proposed.