A blurred border between ordinary concrete and SFRC

Steel fibre reinforced concrete is a well-established construction material. So far its specific properties have been defined and assessed using multiple, literature defined factors and limits. In 2010 there was published fib Model Code which defines strength classes SFRC. The strength classes are based on values of residual strength tested according to EN 14651. Thus it is now possible to tackle SFRC properties in a very precise way. In the paper the research programme aims to define the blurred border between ordinary concrete and SFRC (made on the basis of aggregate of a largest size of 4 mm). The main goal was to get a minimum critical volume of fibre which would transform ordinary concrete into SFRC with an official strength class.