The Mechanical Properties Of Steel Fiber-reinforced Concrete At Low Fiber Content

The steel-fibre reinforced concrete (SFRC) is a new kind of multiply-composite material with a better toughness and crack-resistance besides a higher strength compared with the normal concrete. This paper discussed the influence of the steel-fiber dosage, type and the matrix strength on the basic mechanical properties, elastic modulus, flexural toughness and early-age crack-resistance of steel-fiber reinforced concrete at low content based on experiments. The following is main research contents and achievements.1. In this paper, the mechanic properties influenced by the steel-fiber dosage, type and the matrix strength of SFRC at low content, including the cubic compression strength, splitting tensile strength, axis compressive strength, shear strength and flexural strength, are studied by the experiments. The results of the study show that the steel fiber can improve the splitting tensile strength, shear strength and flexural strength greatly except the compressive strength. The compressive strength of SFRC at low content improved a little and the improving effect is much influenced by the matrix strength. When the matrix strength is low, the compressive strength of SFRC improved with the increase of the fiber dosage, and it is higher than the normal concrete's. When the matrix strength is high, the compressive strength of SFRC drop firstly and then improved, and it is lower than the normal concrete's when the dosage is small.2. The influence of the steel-fiber dosage, type and the matrix strength on the static modulus of elasticity and bending elastic modulus, the relation of static modulus of elasticity and compressive strength and the relation of bending elastic modulus and flexural strength are discussed in this paper by the experiments. The results of the study show that the matrix strength is the main factor influencing the modulus of elasticity of SFRC with a small dosage but not the steel-fiber dosage and type. Because of the experimental methods, the static modulus of elasticity is a little higher than the bending elastic modulus, and the ration is about 1.05.3. Based on the load-deflection curves obtained from the experiments of flexural toughness of 54 test beams of 100×100×400(mm), the effects of the dosage and type of steel-fiber and matrix strength on the bending performance, the failure mode and the cracking development of SFRC at low content are discussed. The curves, the flexural toughness indices and the flexural toughness ratios are calculated and compared. The results of the study show that the cracking bending strength determined by the matrix strength and it is equal to or close to the ultimate bending strength when the dosage of steel-fiber is small. The flexural toughness indices and the flexural toughness rations increase with the increase of the steel fiber content.4. Based on the observation and analyzing the measured results of the cracks of five test SFRC slab and one concrete slab at one day, the effects of the dosage and type of steel-fiber and the matrix strength on the crack-resistance of SFRC at early age are discussed in this paper. The results of the research show that a small fraction of steel-fiber can reduce the area and the width of cracks resulted by self-shrinkage at a large degree. The dosage of steel-fiber is bigger and the length is longer, the crack-resistance of SFRC at low content is better.