Experimental Research On Uniaxial Compression Performance And Constitutive Relationship Of Basalt Fiber Reinforced Concrete

Concrete is naturally brittle,easy to crack,and has low tensile strength.Basalt fiber has become one of the popular materials for strengthening concrete due to its excellent properties.At present,basalt fiber reinforced concrete is mostly used in road engineering,and the relevant application specifications need to be further improved.Therefore,in order to promote the application of basalt fiber reinforced concrete in practical engineering and solve the problem of insufficient design parameters of basalt fiber reinforced concrete,this paper focuses on the uniaxial compression constitutive relationship of basalt fiber reinforced concrete with different strength grades.Against this background,this paper obtained the optimal fiber volume fraction through the test of macroscopic mechanical properties and microscopic pore structure of basalt fiber reinforced concrete,and determined the mix ratio of basalt fiber reinforced concrete with different strength grades.Through the stress-strain full curve test and regression analysis,the uniaxial compression constitutive equations of basalt fiber reinforced concrete with various strength grades were obtained,which revealed the uniaxial compression deformation performance of basalt fiber reinforced concrete.The main work and conclusions of this paper are as follows:1.According to the fiber volume ratio method,basalt fiber reinforced concrete with different strength grades was prepared.The basic mechanical properties test and nuclear magnetic resonance test of concrete were carried out.The results showed that with the increase of basalt fiber volume fraction,the mechanical properties and pore structure of basalt fiber reinforced concrete show the law of first optimization and then deterioration,the decrease in the mechanical properties of concrete is caused by the increase in the number of internal multi-harmful pores.Based on the combination of macroscopic mechanical properties and microscopic pore structure,the optimal basalt fiber volume fraction in concrete is 0.2%,and based on this,basalt fiber reinforced concrete of C25,C30,C40,C50 and C60 was prepared.2.The axial compression test of concrete was carried out,and the stress-strain curves of basalt fiber reinforced concrete of different strength grades were obtained.The peak strain of basalt fiber reinforced concrete with different strength grades is between 0.001627 and0.001950.As the strength grade increases,the elastic modulus also increases gradually.The lateral deformation properties of basalt fiber reinforced concrete were analyzed.The volume of basalt fiber reinforced concrete of various strength grades begins to expand at a relatively rapid rate when the stress ratio is about 0.8 to 0.9.The Poisson’s ratio of basalt fiber reinforced concrete is recommended to be 0.23.Finally,according to the test data,the uniaxial compression constitutive equation of basalt fiber reinforced concrete was obtained by regression analysis of the constitutive equation in the specification,and the fitting degree is high.3.The axial compression test of basalt fiber reinforced concrete based on DIC method was carried out.The changing laws of the lateral and vertical strain cloud diagrams of the specimen surface under different stress stages of basalt fiber reinforced concrete with different strength grades were analyzed,and the failure process of basalt fiber reinforced concrete under axial compression was obtained.The lateral strain concentration area can better predict the appearance and development of concrete cracks.The stress-strain curve of the rising section obtained by the DIC method is in good agreement with the strain gauge-displacement sensor method.Considering the strain equivalence principle and the damage factor d,the axial compression damage constitutive model of basalt fiber reinforced concrete was established,which can describe the damage process before peak stress of basalt fiber reinforced concrete to a certain extent.