ABSTRACT
Justifying the mechanical behaviour of fibre-reinforced sprayed concrete for permanent or long-term temporary structures is a major issue for the development of this technical possibility in underground works in France. One of the aims of this study is to ensure that a minimum tensile strength of class 3c can be achieved, in order to benefit from a significant structural contribution. In addition, a test method specifically adapted to sprayed concrete was standardised in Europe in November 2023 to assess flexural tensile behaviour. For cast elements, this behaviour is assessed using small notched beams subjected to a 3-point bending test (standardised reference test: EN 14651). The design is then carried out in accordance with the Model Code 2010, using the results of this reference test. Fib Bulletin 55 requires correlation parameters to be established between the reference method and any alternative methods. The second objective of this study is therefore to compare the results of the reference test with those obtained using method B of standard EN 14488-3. To do this, three similar concrete mix designs incorporating different metal fibres were characterised with both methods, demonstrating the advantages of the new one: more representative test bodies and significantly reduced scatter in the results. Progressive optimisation of the concrete matrix and the test body spraying technique resulted in a 4c classification, better than expected. New opportunities for improvement are envisaged.
