Experimental Study On Mechanical And Pressure-sensitive Properties Of Iron Tailings Carbon Fiber Cement-based Materials Under Salt Freezing

Carbon fiber reinforced concrete(CFRC)is a new smart material with good mechanical properties and good pressure sensitivity.It is reasonably integrated into engineering structures and can be used for intelligent health monitoring of structures.In order to improve the pressure sensitivity of CFRC and make rational use of waste iron tailings,this paper mainly studies the mechanical properties and pressure-sensitive properties of iron tailings carbon fiber reinforced concrete(ICFRC)mixed with an appropriate amount of iron tailings,as well as the effects of sulfate freeze-thaw environment on its mechanical properties,pressure-sensitive properties and durability.The main research work is as follows:(1)Considering the different content of iron tailings and carbon fiber,63 groups of 189 cube and prism test blocks were designed and manufactured.Through compressive and splitting tensile tests,the main mechanical properties of ICFRC such as cube compressive strength,splitting tensile strength and axial compressive strength were studied,The main laws of the effects of different amounts of iron tailings and carbon fiber on the mechanical properties of cement-based materials are analyzed,the stress-strain constitutive equation of the corresponding materials under compression is established,and the main parameters and parameters in the constitutive equation are fitted.The results show that the mechanical properties of ICFRC are higher than those of CFRC.Generally,the compressive strength and tensile strength of ICFRC are increased by about 10% and 8% respectively.In addition,the stress-strain constitutive model of ICFRC established in this paper is in good agreement with the experimental values,and can be used to analyze the mechanical properties of this kind of materials.(2)The durability tests of 42 groups of 126 corresponding material test blocks under sulfate freeze-thaw environment were carried out by using the rapid freeze-thaw test method.The effects of different carbon fiber content,iron tailings content and freeze-thaw cycle times on the mechanical properties of ICFRC were studied.The appearance damage,mass loss rate,relative dynamic elastic modulus The general variation of compressive strength and strength loss rate with the number of freeze-thaw cycles.The experimental results show that under the same freeze-thaw environment and freeze-thaw cycle times,the durability of ICFRC is better when the content of carbon fiber is 0.4% and the replacement rate of iron tailings is 30%,and the durability of ICFRC is better when the number of freeze-thaw cycles is less under the same freeze-thaw environment.(3)The pressure-sensitive properties of ordinary cement-based materials,carbon fiber cement-based materials and iron tailings carbon fiber cement-based materials under general conditions and sulfate freeze-thaw environment were studied by four electrode method,and the effects of iron tailings content and freeze-thaw cycle times on the pressure-sensitive properties of the above materials were analyzed,The general variation law of pressuresensitive properties of materials with different parameters is discussed,the correlation between stress and resistivity is established,and the corresponding mechanism is analyzed.The test results show that in general,the pressure-sensitive performance of carbon fiber cement-based materials is significantly improved than that of ordinary cement-based materials,and the pressure-sensitive performance of ICFRC is more obvious,especially when the content of carbon fiber is 0.4% and the substitution rate of iron tailings is 30%;Under sulfate freeze-thaw cycle,due to the corrosion of sulfate solution on iron tailings,the conductivity of the material is reduced,which reduces the pressure sensitivity of ICFRC.Attention should be paid to its research and application.