A Experimental Research On Brittleness Reducing Of Ultra-high Strength Concrete

With the development of society and economy, ordinary concrete can not meet the requirement of modern construction to material:high mechanical properties, high dimensional stability and high durability. Concrete is a brittle material, ultra-high strength concrete, which has high strength, also makes its issue of brittleness and volume stability further highlight, thus, it is necessary to study the brittle improvement of ultra-high strength concrete.Based on conventional technique and commonly materials, this paper aims to developing the ultra-high strength fiber reinforced concrete of C100, on this basement, analyzing the brittleness reducing, the microscopic mechanism of fiber on ultra high strength concrete and the durability of ultra high strength fiber reinforced concrete.The experimental results show:①Based on conventional technique and commonly materials, the ultra-high strength fiber reinforced concrete of C100with good workability can be developed, the strength of concrete at28d is up to126.4MPa and the slump is up to220mm with the water-binder ratio of0.20,the total cementitious material of600kg/m3and the steel fiber volume content within the range of1%-2%;②the incorporation of fiber can improve the mechanical properties of concrete, compared to the ultra-high strength concrete, the increase of compressive strength, flexural strength and splitting strength is up to18.8%,21.1%and249.1%after the incorporation of steel fiber, reduce the rittleness,and avoid the burst with the damage of ultra-high strength concrete, the specimens are more complete after the destruction, improve the failure modes;③by using Scanning Electron Microscope(SEM), the incorporation of steel fibers improves the micro-structure of transition zone between cement paste and aggregates, adds the interface of fibers and cement paste matrix, thus makes the interfacial transition zone of ultra-high strength concrete more dense;④Whether ultra-high strength concrete, or ultra-high strength fiber reinforced concrete, both have lower water-binder ratio and more dense internal structure, thus have higher durability, under the conditions of600freeze-thaw cycles, both of the interfaces are complete, the loss of mass and relative dynamic elastic modulus are less than1%, the electric flux is in range of130-230Coulomb, and the electric flux of ultra-high strength fiber reinforced concrete is slightly higher than the one of ultra-high strength concrete, under high temperature conditions of300℃, brittle burst happens on ultra-high strength concrete, but the interface is more complete and the compressive strength has improved after the incorporation of fiber, the fire resistance performance of concrete has significantly improved.