Steel Fiber Reinforced Shotcrete?For Rock Support and Fire Protection

by Reidar Kompen, Aker Entreprenor A/S-Robocon,

Document Type: Proceeding Paper

Part of: Shotcrete for Underground Support V


Rapid development in concrete technology and development of equipment has led to a change from dry hand-operated to wet robot shotcreting in Norway. Shotcrete of more than 100 MPa cube strength can be achieved by the wet method. Wet process shotcreting equipment has been modified to produce shotcrete with a capacity up to 20 m3/hour. Low rebound (5-10%) and no excess rebound of steel fibre combined with the high production capacity, are important contributions to economy and efficiency in rock support. Incorporation of steel fibres first of all gives high fracture energy, i.e. ductile tunnel linings. Tensile properties are also improved, especially under adverse curing conditions. Where frost insulation and sheltering from water leakages are needed, e.g. in caverns and traffic tunnels, sheets of polyethylene foam have proved both effective and economic. To provide fire protection, a special light-weight steel fibre reinforced cement mortar is shotcreted at a thickness of 20-30 mm. A 20 mm thick layer of this material satisfies fire class A120, the material has a high tensile strength, approx 30% of the compressive strength.

Subject Headings: Steel fibers | Fiber reinforced concrete | Material properties | Strength of materials | Fiber reinforced composites | Material mechanics | Tunnels | Norway | Europe

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