Materials. The preparation of ordinary steel fiber reinforced concrete mainly utilizes low-carbon steel fibers. For refractory concrete, stainless steel fibers are a must. The diameter of circular cross-section, long straight steel fibers is generally 0.25 to 0.75mm; flat steel fibers have a thickness of 0.15 to 0.4mm, a width of 0.25 to 0.9mm, and all have a length of 20 to 60mm. Additionally, steel fibers with bent hooks at the ends are used to enhance interfacial bonding.

Steel fiber concrete typically uses 425 or 525 ordinary portland cement, while high-strength steel fiber concrete can utilize 625 portland cement or aluminate cement. The coarse aggregate particle size should not exceed 15mm. To improve the workability of the mixture, a water-reducing agent must be used. The sand content of the concrete should generally not be less than 50%, and the cement dosage should be about 10% higher than that of ordinary concrete without fibers.

(2) Dosage. To ensure even distribution of the fiber in concrete, the length-to-diameter ratio should not exceed 100, typically ranging from 30 to 80. Each type of fiber has a dosage limit, usually between 0.5% to 2% (by volume).

(3) Mixing. Steel fiber reinforced concrete should be mixed using a forced-action mixer. To ensure even dispersion of the fibers in the concrete, the addition should be done through a sieve shaker or a disperser. The mixing sequence differs from that of regular concrete. One method involves first adding the coarse and fine aggregates, cement, and water to the mixer, mixing until uniform, and then adding the fibers. Another method involves three steps: first, mix the coarse and fine aggregates thoroughly; then add the fibers and mix; finally, add the cement and water and mix again.

(4) Compaction. Different compaction methods greatly affect the orientation of fibers. Pumping into the storage without inserting causes a three-dimensional random orientation of fibers; using an insert-type vibration compaction device results in most fibers being three-dimensionally random, with a few being two-dimensionally random; using a flat vibration compactor leads to most fibers being two-dimensionally random, with a few being three-dimensionally random; jet compaction makes fibers two-dimensionally random on the jet surface; using the "centrifugal method" or "extrusion method" places the fiber orientation between one-dimensional orientation and two-dimensional randomness; if compacted in a magnetic field, fibers distribute along the magnetic force lines.

(5) Mechanical Properties. The addition of steel fibers significantly enhances the mechanical properties of concrete. Within the permissible range, it can increase tensile strength by 30% to 50%, toughness by 10 to 50 times, impact strength by 2 to 9 times, with a lesser increase in compressive strength, up to 15% to 25%. Steel fiber concrete can also reduce drying shrinkage by 10% to 30%.

High-cost steel fiber reinforced concrete is also challenging to construct, and it should only be used in appropriate engineering projects. Such as important tunnels, subways, airports, elevated road beds, spillways, and anti-explosion and seismic projects.