The beam samples were cut from panels built from a sprayed primary layer, a sprayed waterproofing membrane layer and a sprayed second layer (Su & Bloodworth 2014). Steel fibre dosage of 35 kg/m3 was used in the concrete mix. The dimensions of the beams are 150 mm deep, 150 mm wide and 900 mm long with a 9 mm thick membrane near the top surface (see Fig. 1).