Dynamic Compressive Properties of Carbon Nanofibers Reinforced Concrete under Impact Load

Abstract To explore the dynamic compressive properties of carbon nanofibers reinforced concrete (CNFC), a 100mm-diameter Split Hopkinson Pressure Bar (SHPB) was used to carry out the impact compression test respectively on the plain concrete samples and the CNFC samples with different fiber volume fractions (respectively, 0.1%, 0.2%, 0.3% and 0.5%). On this basis, the change characteristics of concrete at five different strain rate levels in dynamic compressive strength, dynamic compression deformation, impact toughness and dynamic elastic modulus of concrete were compared and analyzed. The results show that the dynamic compressive strength, dynamic compression deformation and impact toughness of concrete are enhanced by carbon nanofibers to varying degrees. Specifically, when the content of carbon nanofibers is 0.3%, its enhancement effect on dynamic compressive strength is the best; when the content of carbon nanofibers is 0.2%, it helps enhance the dynamic elastic modulus of concrete, but other content can only have the opposite effect. The dynamic compressive strength, impact toughness and dynamic elastic modulus of plain concrete and CNFC gradually increase with the increase of strain rate level, indicating the existence of significant linear relationship; although the dynamic peak strain and ultimate strain increase wholly with the increase of strain rate, there is no obvious linear correlation between them. In addition, the micro test results show that the addition of an appropriate amount of carbon nanofibers help exert the small size effect, strengthen crack resistance and improve the microstructure of the matrix, effectively enhancing the dynamic compressive properties of concrete under impact load.