Design,Preparation And Mechanical Performance Of Full-field Aligned Steel Fiber Reinforced Cement-Based Composites

Cement-based composite has low tensile strength and large brittleness,and it is vulnerable to crack once subjected to tension.The incorporation of steel fibers can limit the appearance and expansion of internal cracks in the cement-based composite when it is subjected to external loads,and improve tensile properties,cracking resistance and brittleness of cement-based composite.In ordinary steel fiber reinforced cement-based composite(SFRC),short steel fibers are randomly dispersed.Some steel fibers that are inconsistent with the direction of the principal stress can not fully paly the role of strengthening and toughening during the process of stress,resulting in the reduction of steel fiber reinforcement.In aligned steel fiber reinforced cement-based composite(ASFRC),steel fibers align to a single direction.When the orientation of steel fibers can be aligned to the direction of the principal stress,the reinforcement of steel fibers will be improved greatly.In the practical engineering,the direction of the principal stress of structural elements that under stress is not aligned to a single direction,but generally varies with location.If the orientation of steel fibers can also be changed with the principal stress and steel fibers in all positions can be aligned with the direction of the principal stress,the reinforcement and toughening effects of steel fibers will be maximized,and the he properties of materials and elements will be improved greatly.In this investigation,the full-field aligned steel fiber reinforced cement-based composite(FASFRC)with the fiber aligned to the principal stress is designed,prepared,tested and analyzed.First,a finite element model of the specimen when subjected to external loads is established to determine the distribution of the principal stress direction.Then the direction of the steel fibers is designed to parallel to the principal stress of the specimen.Secondly,the preparation of FASFRC was investigated.FASFRC specimens are prepared by using external electromagnetic field.Then the orientation distribution of the steel fibers in cementitious matrix and the cracked section of specimens is analyzed.Finally,the mechanical properties of the FASFRC specimens,e.g.,the flexural and tensile properties,are experimentally examined and analyzed through four-point flexure test and uniaxial tensile test.The results show that the finite element numerical simulation technology can theoretically design the direction of steel fibers.The designed direction of steel fibers is consistent with the direction of the specimen when it subjected to external loads.In FASFRC specimen that prepared by electromagnetic fields,the actual direction of the steel fibers is basically the same as the design direction.Compared with the SFRC specimen,the distribution density of the steel fibers on the fractured section of the FASFRC specimen increases.The orientation and distribution of steel fibers have a great influence on the flexural strength and uniaxial tensile strength of the cement matrix.Compared with SFRC specimens,FASFRC specimens have significantly improved in mechanical properties.