Investigation On Orientation Control And Enhancement Effect Of Steel Fibers In Cementitious Materials

The direction of steel fibers is a important factor that affects the improved degree of mechanical properties in cementitious materials. By using a magnetic field the direction of steel fibers can be controlled and become the same with magnetic induction line.Then the orientation factor and enhanced efficiency of steel fibers can all be improved greatly. In addition to the intensity of magnetic field and the viscosity of paste, orientation and distribution of fibers in concrete tend to be also influenced by many other factors such as the coarse aggregates or steel fibers. Based on the above understanding, some researches involving the influened factors on oriention of steel fibers and mechanical properties of aligned steel fiber reinforced concrete (AFC) are investigated. The main contents of my project are as follows.The paper mainly studies the load condition and movement rule of steel fibers in fresh cement paste when a magnetic filed is applied. Then the method of making all steel fibers be directional in the paste is determined.Then the paper analyses the load conditions of steel fibers with different shapes in the paste when a magnetic filed is applied, probing into the effect of fiber shapes on the movement rule of steel fiber. The studies show that all steel fibers with complex shapes would result in different change trend in the aspect of orientation of steel fibers compared with round straight steel fibers because of the change of magnetic filed force and flowing resistance in the paste. Further the paper also studies the movement rule of steel fibers in AFC that include various dosages of coarse aggeregates or steel fibers, determing its influenced law on the orientation control of steel fibers.In the end the enhanced mechanism of steel fibers in concrete are investigated briefly. By testing the mechanical properties of SFRC and AFC including splitting tensile strength and shear strength, the effect of direction of steel fibers on the mechanical properties are also verified experimentally.The research shows that AFC can be prepared successfully through controlling of the magnetic field, viscosity of paste, dosage of steel fibers and coarse aggregates and so on. This new building material could show better mechanical properties, crack resistance and toughness.