| Ultra-high performance concrete(UHPC) is a cementitious material withultra-high performance, such as ultra-high ductility, ultra-high strength, it obviouslyhave higher strength，higher ductility and higher durability，especially much highertensile strength and ductility compared to normal strength concrete(NSC). So it canpromote the cracking strength of construction and the durability of concrete withthese characteristics, also it can promote the durability of bridge if used in it.The way to promote tensile strength of UHPC is mainly depends on the steelfiber. With the addition of steel fiber, tensile strength and toughness could beimproved. The workability and mechanical property of UHPC affect by the fibercontent，aspect ratio and shapes are compared in this paper, and fibers with differentshapes (linear fiber，wave-shape fiber，hooked-fiber) were choosed. Strengthened andtoughened effect of UHPC with different fibers are compared through theload-deformation curves. At last this paper reveals the effect of the factors,such asfiber composite, aspect ratio and shapes, etc, on UHPC strength and toughness byapplying multivariate regression analysis. Through studying and discussion,this textdraws the following conclusions:(1):By means of the workability an physic mechanics property of UHPCexperiment, we found that the fluidity decreases to190mm with increaing fibercontent. With the fiber length to diameter ratio increases, the compressive strength ofUHPC have little changes. However, the flexural strength of UHPC increases with theaspect ratio of fiber increases, and the flexural strength of UHPC reaches themaximum value by the steel fiber with L/D about65.(2):Steel fibers with different shapes have almost the same influence on fluidityof UHPC. Effects on the mechanical performance of UHPC with different types fiberare diverse at a larte stage. UHPC with hooked-fibers has65.3%higher compressiveand bending performances than UHPC with linear fibers. From the ifber pull-outexperiment, we found that the effect of different types of fiber play a major role indetermining the adhesive property and stress transfer of steel fiber UHPC matrixinterface. And hooked-fibers has a adhesive property about23.9Mpa, wave-shapefiber are21.5Mpa, linear one are18.9Mpa. (3):With the increasing of fiber content, the workability of UHPC decrease, yetthe physic mechanics property increaces. The growth rate of compressive and flexuralstrength slowed down with the increasing of fiber content.(4):The crack load of UHPC with deformed fiber has been a slightly improvedcompared with linear fiber, and deformed fiber has shown a greater toughnessperformance than linear fiber in the later stages, further more, hooked-fibers is betterthan wave-shape fibers.(5):By means of the theory about mechanism of fiber-enhanced mortar，Thispaper derived the impact of strength and toughness of UHPC about length to diameterratio, adhesive strength and fiber content. By compareing with this results, we get afitted curve at last. |
