Study On Mechanical Properties Of Polypropylene Fiber Reinforced Concrete

With the rapid development of economy and the continuous improvement of people’s living standards,the defects of traditional concrete materials such as low tensile strength,easy cracking,low impermeability and poor deformation ability are gradually revealed,which can not meet the high-performance needs of building materials in the field of civil engineering.Adding an appropriate amount of polypropylene fiber to concrete can effectively improve the compressive strength and tensile strength of concrete,and improve its disadvantages such as low tensile strength and easy cracking.Therefore,the research on polypropylene fiber concrete has important practical significance and engineering application prospect.In this paper,through the compression and splitting tensile tests of polypropylene concrete with different fiber content,fiber length and curing time,the optimal fiber content and length of C30 concrete are obtained;In view of the problems of eccentricity and tensile stress concentration in the current concrete axial tensile test,a new type of fiber reinforced concrete axial tensile test device is designed and developed,and the axial tensile test of polypropylene fiber reinforced concrete is completed.The results of splitting tensile test and axial tensile test are co MPared and analyzed;ABAQUS finite element software is used to establish the numerical model of separated polypropylene fiber concrete.With the help of the research method of the combination of numerical simulation and test,the accuracy of the established separated numerical model is verified,the relevant parameters are analyzed,and the relevant change laws are obtained,which can be applied to practical projects in the future.The main contents and research results of this paper are as follows:(1)Through the compression and splitting tensile tests of polypropylene fiber concrete with different fiber content,fiber length and age,the optimal content of C30polypropylene fiber concrete is 0.9kg/m~3.The test results show that the compressive strength and splitting tensile strength increase with the increase of content.When the content exceeds 0.9kg/m~3,the compressive strength and splitting tensile strength show a downward trend;The compressive strength and splitting tensile strength of polypropylene fiber concrete at the age of 14d,28d and 60d increased by different ranges co MPared with the reference group regardless of the dosage.When the dosage was 0.9kg/m~3,the mechanical properties of concrete at the age of 14d,28d and 60d increased the most co MPared with the reference group;The optimum fiber length of polypropylene fiber concrete is 19mm.The compressive and splitting tensile test results of 6mm group and12mm group are less than 19mm group.(2)Through the self-developed fiber concrete axial tensile test device,the axial tensile test of polypropylene fiber concrete is completed.The test results show that the axial tensile strength of concrete increases with the increase of content,and the tensile strength decreases when it exceeds 0.9kg/m~3;The axial tensile strength of concrete aged14d,28d and 60d increased by different ranges co MPared with the reference group regardless of the content.When the content was 0.9kg/m~3,the axial tensile strength of concrete aged 14d,28d and 60d increased the most co MPared with the reference group;Co MParing the splitting tensile and axial tensile test results,when the fiber content is0.3kg/m~3and 0.6kg/m~3,the difference between the test results is 0.45MPa,when the fiber content is 0.9kg/m~3and 1.2kg/m~3,the difference between the test results is 0.41MPa,and when the fiber content is 1.5kg/m~3,the difference between the test results is 0.48MPa.(3)The random distributed polypropylene fiber coordinates are generated by using the rand function of MATLAB software,and the three-dimensional model of polypropylene fiber is established by importing ABAQUS finite element software.The polypropylene fiber model is embedded and assembled with the concrete model to establish the separated polypropylene fiber concrete model.The numerical simulation of three mechanical tests on fiber reinforced concrete model is carried out.and the simulation results were co MPared with the test results,and it was found that the numerical simulation and the test results were basically consistent;For the conical failure surface,the simulated damage cloud image of the split tensile test is basically consistent with the actual test failure shape,and two triangular failure areas appear.The results of the axial tensile test are basically consistent with the simulation results.The fracture surfaces show irregular failure with a small amount of aggregate falling off,The accuracy of the separated polypropylene fiber concrete model is verified.