Research On Static And Dynamic Compressive Behavior Of 3D Braid Steel Fiber Reinforced Concrete

As one of the most widely used engineering materials, concrete are characterised by the inherent low tensile strength and brittleness. Mixing in a certain content of steel fibers is a way to overcome this defect. Research has shown that strength of steel fiber reinforced concrete (SFRC) is closely related to fiber volume percentage, length-diameter ratio, and fiber distribution. High fiber volume percentage, large fiber length-diameter ratio and well-proportioned distribution are beneficial to the strength and toughness of SFRC, which consequently lead to excellent anti-blast and anti-penetration performance, and obvious reduction of explosion induced spalling. This research aims at integrating 3D braiding technique with SFRC and developing 3D braided steel fiber reinforced concrete (3D-BSFC). Steel fibers are firstly braided and put into moulds, and then slurry is infiltrated in. Since fibers are not mixed in, fiber volume percentage in BSFC is not limited by the mix process as in SFRC, and the fiber orientation and distribution also can be designed. Furthermore, as braided steel fibers can work integrally, BSFC is expected to exhibited better performance than SFRC. This paper attempts to implement 3D-BSFC, and get specimens of BSFC, subsequently investigate the mechanical performance.One of the manufacturing procedures of making 3D-BSFC include: 1) lay fibers in two perpendicular directions within a plane; 2) a certain amount of slurry is infiltrated in; 3) lay another fiber layer, and infiltrate slurry; 4) after all of the horizontal fibers are placed, vertical fibers are inserted. The other include: 1) braid 3-D steel framworks; 2) lay 3-D steel framework into mould; 3) infiltrate slurry and shake. Then specimens of 3D-BSFC with steel fiber volume percentage (Vf) of 0(SC0), 5% (SC05) and 10% (SC10) were prepared.Specimens were tested uniaxially by a multifunction servo-controlled testing machine under two types of quasi-static low strain rate (10-4 s-1and 10-2 s-1). The whole stress - strain curve, strength, toughness and compression elasticity modulus were obtained. Compressive characteristics of 3D-BSFC and influences of steel fiber volume percentage and strain rate on the basic mechanical performances were investigated.Dynamic compressive properties of specimens were tested by a Split Hopkinson Pressure Bar (SHPB) of 75 mm diameter, and different strain rate levels were included. Some data about 3D-BSFC at different strain rates are received, e.g, dynamic stress-strain relations, dynamic increasing factor, the effect of fiber-content and type of fiber on the dynamic properties of materials and dynamic failure modes.Based on the experimental and numerical results, the constitutive model for 3D-BSFC is researched. Using the ZWT model considering the damage effect for constitutive fitting and the HJC model for numerical simulation respectively, credible results of 3D-BSFC were obtained.