A Study On Bending Capability And Impact Resistance Of Basalt Fiber Reinforced Concrete Under The Frost-thaw Condition

In cold region, the freeze-thaw damage of concrete is the main reason for decreasing its bearing capacity and reducing its service life. With the concrete increasingly wide use, especially in the airport pavement, coastal engineering, equipment base and so on, civil engineering not only requires concrete having excellent static mechanics performance, but also puts forward higher requirements to the dynamic mechanical properties. Basalt fiber is a pollution-free fiber material. It has many advantages: good mechanical properties, durability, easy to mix, low price. Basalt fiber is soft and it will not damage the tire. All of these make it become a kind of irreplaceable pavement concrete adding material.This article through to use basalt fiber reinforced concrete with different fiber dosage which under different freeze-thaw cycles to do bending test and impact test for analyzing the effect of the basalt fiber to concrete. At the same time, calculate the flexural strength, fracture toughness, impact toughness and other mechanical parameters. Using digital image correlation technique to film the process of the bending test and impact test, analysis the horizontal change rule of the specimen under stress and the factors which affect crack propagation direction. To comprehensive analysis above, find the toughening mechanism of basalt fiber.The final analysis conclusion:(1)Basalt fiber can not improve the compressive strength of concrete, but it can improve small amounts of flexural strength and a large number of impact number of times. 2.0 kg/m3 is the optimum content of the basalt fiber in this test.(2)Compared with the folding strength enhancement degree from basalt fiber before freeze-thaw cycles, incorporating fiber will make the flexural strength of concrete after freeze-thaw cycles more improvement. Compared with the shock resistance enhancement degree from basalt fiber before freeze-thaw cycles, incorporating fiber will make the shock resistance of concrete after freeze-thaw cycles less improvement. After more than a certain number of freeze-thaw cycles, basalt fiber reinforced function failure.(3)In bending test, the specimen cracking has three horizontal strain changes before process. They are strain adjustment stage, more choice stage, the upper specimen compression stage appear on both sides of the middle tension compression. Strain adjustment will cause damage to the coarse aggregate and cement base interface. In shock test, according to the specimen on the different features of horizontal strain increase regional extension, specimen impact damage forms can be divided into three categories: Impact fracture appear in the bottom of the specimen and extended to damage; Upper and lower horizontal strain increase at the same time,the bottom cracking after series; Specimen upper horizontal strain increases to the bottom, than the bottom cracking.(4)Toughening principles of the basalt fiber is the fiber links different concrete parts bear pressure together, so that increasing the concrete deformation area, than the concrete can take more strain.