Studies On Enhancement Of Fracture Destroy And Impact Resistance Performance By Composite Cement-Based Material With Steel Fiber

Cement based material is the most widely used in the world, which has various disadvantages in engineering including its low tensile strength, great brittleness and poor anti-crack performance. According to this, the cement based material performance was enhanced by reinforcing and toughening with “fiber composite” technology.Effects of steel fiber type and volume rate on flexural strength, flexural toughness, fracture toughness and impact ductility of test pieces were investigated in this study, which based on composite materials tests of bending strength, flexural toughness and impact resistance under different steel fiber types and volume rates by using digital image correlation(DIC). In addition, the mechanism of reinforcing and toughening with steel fiber was deeply analyzed combined with DIC full horizontal-strain summary.The main conclusions are as follows:(1) the test of compressive strength and bending showed that the cement based material flexural strength increased by 50% under volume rate of 1.5% was significantly enhanced with steel fiber while the improvement of compressive strength was relatively limited. The effect of indentation type steel fiber and end hook steel fiber on the flexural toughness of the cement matrix was basically the same, which can be improved by 5.4 times. With the ductility analysis of cracking load and specimen, it suggested that the effect of indentation type steel fiber on cracking load and bending strength is better. Bending fracture tests showed that crack stability improvement was more effect by cement based materials with steel fiber, which can ease the strain on the tip of the crack tip.(2) It suggested that the initial crack and number of damage of cement based materials were obviously increased, at the same time, the energy and ductility performance were effectively improved in impact experiments. Under the impact load, the effect of reinforcing and toughening on substrates by using end hook steel fiber was better than indentation type steel fiber.(3) According to the variation of samples surface strain distribution in bending test with DIC technology, the process of enhancement of composite cement based materials flexural failure with steel fiber was divided into three stages: micro crack propagation; macro crack diffusion; macro crack diffusion. The failure morphology of composite cement based materials with steel fiber enhancement was analyzed by the fact of changes of samples surface strain distribution in bending test. It suggested that with the increase of steel fiber volume ratio(0%~1.5%), the re-distribution process of specimen stress was extended, cracking point selection increased, changes in cracks became slow, the quantity and width of cracks were getting much and decreased respectively.