Experimental Study On Size Effect Of C30 Steel Fiber Reinforced Concrete

Concrete is a quasi-brittle material,the mechanical properties of concrete in addition to its own nature of the material,but also closely related with the size of the geometric size.From a microscopic point of view,the aggregate of concrete contains many holes and microfractures,which are typical nonuniform materials.The strength-size effect is the unique property of such materials.With the increase of the size of the specimen,the compressive and tensile strength of concrete will be reduced to different degrees.In the actual project used in the concrete geometric size is large,if the use of similar size of the specimen to carry out strength test is very difficult,so most scholars use the scale simulation method to carry out concrete mechanical performance test,through the trial launched Size effect formula to calculate the concrete strength of the actual project.In recent years,with the engineering structure of the concrete performance requirements,in order to meet the needs of various areas of concrete material strength,scholars and structural research experts are exploring how to improve the mechanical properties of concrete,through a large number of experimental verification found,Adding a small amount of steel fiber to the concrete can improve the strength performance of the concrete effectively.However,the research on the steel fiber concrete is not comprehensive enough at this stage,so it is necessary to study the mechanical properties of the steel fiber reinforced concrete.Nowadays,C30 concrete is widely used in practical engineering,and it is widely used.Therefore,the size effect of C30 steel fiber reinforced concrete is studied in this experiment.In view of the above situation,this study selected C30 steel fiber reinforced concrete compressive strength,splitting tensile strength and flexural strength of three aspects of the size effect of the study,the main contents are as follows:1.steel fiber reinforced concrete compressive strengthThe specimens were packed in cubes and prisms.They were divided into 100 mm,150 mm and 200 mm sizes.The volume fraction was 0% and 0.75% respectively.And 1.5% of the steel fiber,in the standard conditions(temperature 20 ± 2 ℃,relative humidity ≥ 95%)under the conservation of 28 d,after curing to take out the compressive strength test.The experimental results show that the compressive strength of steel fiber concrete does have the size effect.In the case of the same steel fiber volume ratio,the larger the specimen size,the lower the compressive strength.Based on the size effect theory of Bazant energy release,the compressive strength formula of C30 steel fiber concrete with different specimen size and different steel fiber volume ratio is established.The dimensional conversion factor of the strength of different size cube specimen and the cube and prism The relationship between thecompressive strength of the specimen.2.Steel fiber concrete splitting tensile strengthThe scale effect of steel fiber concrete splitting tensile strength test,the test form for the cube,divided into 100 mm,150 mm and 200 mm three different sizes,the size of the sample were added volume rate of 0%,0.75% and 1.5% of the steel fiber,under the standard conditions of conservation for 28 d,after curing in accordance with the standard test method of steel fiber concrete splitting tensile strength test.The results show that there is a size effect on the splitting tensile strength of steel fiber reinforced concrete,and the splitting tensile strength tends to decrease with the increase of specimen size.And the size conversion coefficient of the tensile strength of steel fiber reinforced concrete was obtained by the test results.The formula of splitting tensile strength of C30 steel fiber reinforced concrete was deduced.3.Steel fiber reinforced concrete flexural strengthThe steel fiber concrete strength test was carried out,the test form for the prism,divided into 100 mm × 100 mm × 400 mm,150 mm × 150 mm × 550 mm two different sizes,the size of the specimen were added volume The rate of 0%,0.75% and 1.5% of the steel fiber,under the standard conditions of conservation for 28 d,after curing to take out the bending strength test.The results show that there is a size effect on the flexural strength of steel fiber reinforced concrete,and the flexural strength tends to decrease with the increase of specimen size.The formula for calculating the flexural strength of C30 steel fiber reinforced concrete was deduced by regression analysis of the test data.The scale conversion coefficient of steel fiber reinforced concrete was obtained by the test results.