Ductility of the Four-Year-Old Steel Fibre Reinforced Concrete

The paper deals with the results of an experimental investigation into the ductility of Steel Fibre Reinforced Concrete (SFRC) with a steel fibre content of between 0,5% and 2% by volume, and that of a comparable concrete without fibres. These investigations are part of a large-scale research project on the SFRC that lasted 4 years. At their age of 4 years high compressive strength has been achieved, with average values in the range of approximately 60 to 115 MPa. These concretes can be divided into two groups: 1^st group - concrete with a maximum nominal grain size (D_max) of 16 mm with compressive strength of 90 to 115 MPa and 2^nd group - concrete with D_max = 4 and 8 mm with a compressive strength of 60 to 80 MPa. The ductile behavior of SFRC was evaluated by the ductility factor 1/B. 1/B is a parameter for evaluating the behavior of FRC, which takes into account the entire surface under the load – CMOD curve. In this way it is possible to evaluate the behavior of the FRC with only one parameter. Wedge Spit Test (WST) method was used to obtain load – CMOD curves. In 1^st group, a large influence of the fiber aspect ratio (l_f/d_f) on the increase of 1/B and the lower impact of the aggregate type is visible. In 2^nd group, the influence of polymer, D_max in addition to fibers on ductile behavior, can be noticed.