Investigation the Application of the Steel Fiber in Special Steel Fiber Concrete and its Effect on Concrete Permeability and Compression Strength Parameters

Steel fibers have high elasticity modulus and failure strain. According to their deformability and high tensile strength, these products are considered as one of the most suitable and economic types of fibers. Additionally, seeping the fluid materials into the hardened concrete has an unfavorable effect on the concrete endurance. The amount of seepage depends on the permeability rate of hardened concrete. Essentially, in construction of the concrete tanks and dams, compression strength and permeability parameters of concrete against water is very important and it is so common to use the special concretes in these types of projects. Therefore, in the present study it has been tried to investigate the behavior of steel fibers concrete against permeability and its compression strength with a change in percentages of steel fibers. The effects of maximum coarse aggregate size on the compression strength and concrete permeability have also been studies. To achieve this goal, 4 mixing plans were designed based on the compression strength 40 MPa, water to cement ratio (W/C) equal to 0.42, the maximum coarse aggregate were respectively 19, 12.5, 9.5, 4.75 and then a suggested percentage of micro-silica and super-plasticizer was added in order to enhance the concrete properties. Each mixing design also includes steel fibers with volumetric percentages 0, 0.3, 0.6, 0.9 and 1.2 of the concrete. In the next step, compression strength of fiber cubic samples in considered ages of 7 and 28 days were determined and registered by the concrete- compression test apparatus. Meanwhile, the fiber cylindrical specimens in age of 28 days were also tested by the permeability tests apparatus. Results of these experiments showed that applying the metal fibers in low percentages (0.3 and 0.6), does not have considerable effect on the compression strength of samples, but in high percentages of metal fibers (0.9 and 1.2), compression strength of samples also increases. Additionally, in all cases, the concrete permeability of metal fibers is less than the ordinary concrete, so that in most designs, as steel fiber percentage increases and size of gravel aggregate decreases, the permeability coefficient tends to reduce. Finally, based on the experimental results, steel fiber concrete with the maximum gravel aggregate (9.5 mm) and the percentage fiber equal to 1.2 was introduced as the best mixing design