Studies On The Influence Of Stainless Steel Fiber On The Performance Of UHPC

Ultra high performance concrete?UHPC?is characterized by high strength,high toughness and high durability.The incorporation of fibers can not only improve the compressive properties,but also significantly improve the toughness.Research and application show that steel fiber can obviously improve the mechanical properties of UHPC.In the engineering application,the most used is copper plated steel fiber,while the surface of the fiber is plated with copper,but in the process of UHPC preparation,copper plating is easily damaged by the friction between materials.In actual engineering,the surface of UHPC with copper steel fiber is easy to rust,especially in some bad environment,such as ocean,freezing and thawing cycle.Using organic fibers instead of copper plated steel fibers can improve the corrosion of UHPC surface,but the effect of mechanical improvement is not as good as that of copper plated steel fibers.Both stainless steel fiber and copper plated steel fiber are steel fibers,but the stainless steel fibers are not easy to rust and resist high temperature,and the influence of stainless steel fiber on the mechanical properties of UHPC is not clear.The mechanical properties and corrosion resistance of stainless steel fiber to UHPC were studied in this paper.The effect of stainless steel fiber on the compressive strength,flexural strength and modulus of UHPC was studied by adding stainless steel fiber with different length to diameter ratio and fiber content.The effect of stainless steel fiber on the corrosion of UHPC surface was studied by the dry and wet cycle test of UHPC mixed with stainless steel fiber and copper plated steel fiber respectively.The test results show that:The addition of stainless steel fiber can improve the compressive strength of UHPC.When the ratio of length to diameter is 80,and the content of stainless steel is2%,the strength of UHPC containing stainless steel fiber is 32%higher than that of UHPC no containing stainless steel fiber.When the fiber content is the same,the compressive strength of UHPC has little change with the increase of length diameter ratio.When the fiber length to diameter ratio is the same,when the fiber content increases,the increase of UHPC compressive strength is greater.But when the value exceeds a certain value,the compressive strength will be reduced.The incorporation of stainless steel fibers can increase the compression modulus of UHPC.When the fiber content is the same,the elastic modulus of UHPC with stainless steel fiber with different length-diameter ratios is basically unchanged.When the length diameter ratio is the same,when the fiber content increases from 0%to 2.5%,the elastic modulus of UHPC increases continuously.The flexural strength of UHPC is significantly increased by stainless steel fibers.When the ratio of length to diameter is 80,and the content of stainless steel is 2%,the bending strength of UHPC is increased by 137.6%than that of UHPC no containing stainless steel fiber.When the fiber content is the same,the larger the ratio of length to diameter,the better the flexural strength of UHPC will be.Under the same fiber aspect ratio,the growth rate of UHPC increases with the increase of the volume.The incorporation of stainless steel fibers into UHPC significantly improved the toughness.The UHPC with fiber content of 2%increased significantly compared with the toughness index I₅,I₁₀0 and I₂₀0 of UHPC.The influence of the addition of stainless steel fiber on the initial crack strength of UHPC is lower,and the peak strength can be greatly improved.The peak strength increases as the amount of the addition increases.In the same fiber content and fiber length to diameter ratio,both stainless steel fiber and copper plated steel fiber can significantly improve the compression and bending strength of UHPC.The volume of stainless steel fiber is 2%,the length diameter ratio is 80 UHPC than no containing stainless steel fiber UHPC,the compressive strength is increased by 36.8%,the bending strength is increased by137.6%.The volume content of the copper plated steel fiber is 2%,the length diameter ratio is 80.The compressive strength of UHPC is 34.4%higher than that of no fiber UHPC,and the bending strength is increased by 141.9%.It is considered that stainless steel fiber and copper plated steel fiber have the same improvement effect on the compressive and bending properties of UHPC.The UHPC doped with stainless steel fiber has excellent corrosion resistance compared with the UHPC doped steel fiber.After 11 cyclic drying and wet tests,the surface of the stainless steel fiber has no rust on the UHPC surface,while a large amount of rust appears on the UHPC surface of the steel fiber coated steel fiber.