Engineering application status of steel fiber concrete
After more than 30 years of research and development, scientific and technological circles at home and abroad have developed a variety of new fiber-reinforced cement composite materials based on the original practice, such as: synthetic fiber (nylon, polypropylene, etc.) reinforced cement composite materials, carbon fiber reinforced cement Composite materials, metal glass fiber reinforced cement composite materials, mortar infiltrated fiber reinforced concrete (SIFCON), high-strength and high-durability fiber-reinforced concrete, FRP (resin-bonded fiber reinforcement) prestressed concrete, etc. Although various types of fiber-reinforced composite materials are diverse and have their own characteristics, steel fiber concrete is the most widely used, technically mature, basic performance researched, and commercialized.
Steel fiber shotcrete was first applied in Idaho, USA in 1973. After that, it was successfully applied to tunnel liners, slope stabilization, culverts, reservoirs and other structural projects. In recent years, steel fiber concrete has been successfully applied to high-rise buildings in China. The steel fiber content is 1% of the concrete volume, which is equivalent to 78kg of steel fiber per cubic meter of concrete. The shear and twisted steel fiber produced by Yangzhong Engineering Fiber Factory is adopted, the concrete strength grade is C40, and the coarse aggregate particle size Dmax≤20mm. During the construction, the steel fiber and cement sand and gravel aggregate are mixed evenly and then water is added for normal mixing. There is one more process than ordinary concrete, and its shear strength is increased by 45%. In addition, the use of wet-sprayed steel fiber concrete has also been successful in the Xikang line's chair mountain tunnel project.
Due to the high compressive, tensile and shear strength of steel fiber concrete, it has a strong supporting function. The wet spray steel fiber concrete process saves manpower and material resources, and can simplify the process and reduce the cost. The sprayed concrete construction does not require a template, and only needs to be equipped with a sprayer and a mixer, which eliminates the process of supporting, pouring and demoulding, so that the concrete conveying, pouring and tamping are combined into one process, and the mutual interference between the processes is also reduced. Speed up the construction speed of the lining. Wet-sprayed steel fiber concrete can be used for construction of thin-walled structures in any direction at high altitudes or in small working spaces through a conveying hose. Therefore, it has a wide range of applications in tunnel construction and can be applied to linings above Class IV. Compared with dry spraying, wet spraying greatly reduces construction dust, and the appearance of concrete is rough, which can absorb sound waves and reduce echoes, so it has the function of reducing noise.
In recent years, due to the rapid improvement of domestic steel fiber production technology, the price of steel fiber has dropped sharply, and the investment of steel fiber concrete is not much different from that of ordinary concrete. The economic index of SFRC is to evaluate the engineering cost of steel fiber concrete from the perspective of comprehensive economic benefits. It can be found that the superiority of steel fiber concrete is very obvious.