What is the best way to specify the shotcrete reinforcement?
A. Specifications can be either performance-based (eg. 360 J on a standard RDP test) or recipe-based (eg. 8 kg/m3 of fibre X). It is our view that the former is preferable, as it ensures the designer considers what is desired from the shotcrete in terms of the performance and yet allows the contractor the flexibility to use whatever materials are currently available to meet the specification. With the increasing speed of technological improvements, it is not always possible for designers to be abreast of the latest materials. A recipe-based specification is self-defeating if the contractor uses the specified materials in a poor manner.
