Experimental Study On Mechanical Behavior Of Short Carbon Fiber Reinforced Concrete Beam

Fiber cement-based composite materials is a composite material based on mortar or concrete with short fiber mixed in.With the rapid development of construction industry,the traditional engineering materials are unable to meet the needs of people.Fiber reinforced concrete and mortar is the product of traditional engineering materials transforming to high tensile,high toughness,high cracking resistance,high durability and intelligent materials.Carbon fiber belongs to the high modulus fiber which not only have the advantages of other fiber composite materials,but also can resist to corrosion,heat,aging and so on.Besides,the conducting properties of carbon fiber can be made into intelligent component,making the structure health monitoring possible.In this paper,tests were conducted to find the influence of the carbon fiber length on the properties of composite materials.The economic efficiency was considered to find the reasonable local reinforcement pattern of carbon fiber reinforced concrete beams,explore the influence of length and thickness of carbon fiber on the performance of composite beams.The main work and results are as follows:The influence of carbon fiber length on compressive strength,splitting tensile strength of concrete was studied.The result shows that concrete mixed with carbon fiber can effectively improve the tensile strength of concrete which can be increased by 26% using 10 mm carbon fiber,better than 5 mm and 15 mm carbon fiber;carbon fiber can not effectively improve the concrete compressive strength,on the contrary,can reduce the compressive strength when the concrete is mixed with 15 mm carbon fiber.Flexural strength of carbon fiber reinforced cement mortar and force-electric coupling effect were studied.Flexural strength increases obviously with the increase of carbon fiber length.Toughness of mortar specimens which mixed with carbon fiber improves significantly.Carbon fiber cement mortar has good strength-electrical sensitivity,in three loading stages,specimens shows obvious resistance variation characteristics.Pattern of partial carbon fiber reinforced concrete was proposed.Test of 14 large size specimens of four-point bending was conducted to find out that reinforcing the tension zone of the RC beams with carbon fiber can improve the mechanical properties.Major conclusions are as follows: Yield load of composite beam increases with the increasing of carbon fiber layer thickness.Among three kinds of carbon fiber length,yield load of CFRC-75-10 which reinforced with 10 mm carbon increases most which can increase by 26.59%.The effect of carbon fiber layer to the ultimate bearing capacity is not obvious,the rate of improvement is between 7% and 12%.Within certain range,the greater crack width is,the more obvious inhibitory effect of carbon fiber will be.Crack inhibition effect of CFRC-75-10 is remarkable.The mix of carbon fiber layer can improve the fracture morphology,reduce the maximum crack width and provide guarantee for durability.The formula for calculating the bearing capacity of carbon fiber composite beam was proposed based on the assumption of fiber reinforced concrete bending member.The results obtained are in good agreement with the experimental values,which can provide a reference for the design of bearing capacity of composite beams.