Study On Coupling Effect Of Steel Fiber Length And Coarse Aggregate Size On Flexural Behavior Of SFRC

Steel fiber reinforced concrete is a type of modified concrete material which is formed by the uniformly and disorderly distributed steel fiber in concrete matrix. In order to get the suitability of different steel fiber length and coarse aggregate size and promote the application of SFRC in engineering, this paper studied the coupling effect of steel fiber length and coarse aggregate size on the properties especially flexural properties of SFRC with the steel fiber length from 30 mm to 60 mm, coarse aggregate maximum size from 10 mm to 40 mm, the ratio of steel fiber length and coarse aggregate maximum size in the range of 1-4. The main content is as follows:1. The research on the effect of steel fiber length and the maximum size of coarse aggregate on steel fiber reinforced concrete mixture working performance has been done. The experimental results show that the mixture slump presents increasing trend with steel fiber length or coarse aggregate size increasing.2. Through the compressive and splitting tensile experiments on 192 cube specimens with size of 150mm×150mm× l50 mm, the effects of steel fiber length and coarse aggregate maximum size on compressive strength and splitting tensile strength of SFRC have been studied. The experimental results indicate that steel fiber length and coarse aggregate size have no obvious influence on the cube compressive strength of steel fiber reinforced concrete. The splitting tensile strength of steel fiber reinforced concrete approximately linearly increases with steel fiber length increasing. In general, along with the increasing of coarse aggregate size it shows a trend of increasing at first then decreasing. The ratio of splitting tensile strength of steel fiber reinforced concrete to matrix concrete shows the same trend.3. Through the four-point bending experiments on 96 prism specimens with size of 150 mm×150 mm× 550 mm, the effects of steel fiber length and coarse aggregate maximum size on flexural strength and flexural toughness of SFRC have been studied. The experimental results suggest that when steel fiber length and the maximum size of coarse aggregate ratio is 1.25-3, the improvement effect of steel fiber on flexural performance of concrete is better, and the effect of long fiber on strengthening and toughening of large size aggregate concrete is considerable.4. Through counting the steel fiber of the four-point bending specimens fracture section after the bending experiments, study of the effect of steel fiber length and coarse aggregate maximum size on fiber distribution has been done. The experimental results indicate that the distribution uniformity of steel fiber in concrete is lightly influenced by steel fiber length and reduces with the coarse aggregate maximum size increases.5. The load-deflection curves obtained from four-point bending specimens have been converted into the corresponding stress-strain curves. The damage evolution equation and damage constitutive model of steel fiber reinforced concrete under flexural load have been established considering the effect of steel fiber length and coarse aggregate size based on the damage theory and Weibull statistical distribution theory. It is shown that the damage constitutive model can effectively describe the flexural behavior of steel fiber reinforced concrete under the strain at a range of 0 to 1.5 times of the peak strain.