Specifying and testing fibre reinforced sprayed concrete: Advantages and challenges of some testing methods

Abstract

The mechanisms through which FRSC (Fibre Reinforced Sprayed Concrete) controls deformations and absorbs energy are complex and involve the technicalities of both the sprayed concrete process and the fibre properties.Toughness is generally the main criterion for FRSC as ground support. However, for the FRSC to have the highest strength and toughness, there must be an optimal design and combination of concrete strength, fibre anchoring and placement method.Consequently, the choice of fibre type and content must correspond to the ground conditions of a specific area and the expected concrete mixture design. There is no unique design method broadly accepted for the design of FRSC for ground support. General guides exist, but there is no specific/complete design guide accepted for FRSC as ground support.Multiple performance criteria: flexural strength, residual flexural strength after cracking, moment-normal force (M-N) behaviour, energy absorption (toughness). This paper will underline, as mentioned in the European standard EN 14487-1, the different ways of specifying the ductility of FRSC in terms of residual strength and energy absorption capacity. The energy absorption value measured on a panel can be prescribed when - in case of rock bolting - emphasis is put on energy, which has to be absorbed during the deformation of the rock. This is especially useful for primary sprayed concrete linings. The residual strength can be prescribed when the concrete characteristics are used in a structural design model. This paper will present the majors results on a research project undertaken this year at Laval, Roma and Bochum University. The characterization of a fiber reinforced concrete made with EFNARC is similar to what obtained with EN 14651 beam tests.