Investigation Of Preparation And Flexuralproperties Of The Two-Dimensional Oriented Steel Fiber Reinforced Cementitious Composites

The application in pavements,pavements,bridge decks,and repair coverings is the main project scope of the current application of steel fiber reinforced cement-based composites(SFRC)for commercial applications.And it is already demonstrated the good behavior.In conventional SFRC,however,in which the steel fibers are randomly distributed in orientation and location,some fibers do not take any effect of reinforcement.Unlike the SFRC,if the fibers in matrix are aligned to tensile stress,all the fibers will reinforce the composite effectively,thus decreasing the cost of raw materials and increasing the mechanical properties of the composite.As to plate-like members used in pavement,bridge deck pavement and other projects,the direction of stress is distributed along the plane in multiple directions.Correspondingly,there exists a demand for the composites with a multi-directional reinforcement effect on the plane.The study of preparation method and flexure-tension properties of two-dimensional oriented steel fiber reinforced cement-based composites is of significance to the development and application of the composite.Firstly,an approach of arranging steel fibers in two-dimensional space in cement mortar was presented,based on the influence of the rotating electromagnetic field on steel fibers in cement matrix.The specimens of different steel fiber fractions of random and two-dimensional steel fiber distribution were cast to investigate the fiber distribution feature.The results show that the method of controlling the two-dimensional oriented distribution of steel fibers according to the principle of rotating electromagnetic field is effective.The number and the orientation feature of steel fibers at the crack section in specimens with steel fibers arranged in two-dimensional are significantly different from that of the specimens with random steel fibers.Compared to the random distribution of steel fibers,when the steel fibers are two-dimensionally oriented,the angle formed by any steel fiber in the matrix and the direction of tensile stress increases,increasing the projected length in the stress direction.And thus the probability of steel fibers crossing the crack section increases.Then,the splitting test of cubes,flexure test of prisms and round panels were conduct on two-dimensional and conventional randomly distributed steel fiber reinforced cement-based composites.The results show that the two-dimensional orientation distribution of the steel fibers significantly improved the flexure-tensile properties of the composite,compared with the conventional SFRC.Finally,the mechanism of the reinforcement of two-dimensional oriented steel fibers on the mechanical properties of cement-based composite is explored by means of acoustic emission analysis.Compared with the random distribution of steel fibers,the hits of acoustic emissions from two-dimensional orientation specimens during the destruction process increases,indicating that there are more steel fibers at the fracture cross-section.On the other hand,the specimens with two-dimensionally oriented steel fibers release small energy when the main crack generates.And the energy released during the whole damage process is more dispersed.The results indicate that the two-dimensional orientation of the steel fibers effectively prevents the crack propagation.Moreover,when steel fibers are two-dimensionally oriented,the characteristics of the signal of steel fiber pull-out,the smaller average frequency and rise angle,are obvious.The result indicates that the crack mechanism of the steel fibers is more prominent in specimens with the two-dimensionally oriented steel fibers,increasing the efficiency of the reinforcement of the steel fibers.