In recent years, fiber reinforced concrete has been increasingly used not only for industrial floors but for many other loadbearing structures as well. The different types of synthetic fibers have distinct effects on concrete: micro fibers to reduce plastic shrinkage cracking of concrete, and macro fibers to give higher fracture toughness. This paper investigates whether when using mixed fibers (a blend of micro and macro fibers) the advantages of the two types remain separate or whether a new effect arises. Three-point bending tests are made to examine the effect of the different fiber types on the ductility of concrete. The existing theoretical smeared models’ predictions of expected experimental results are not accurate enough because of the high deviation of the data. In this study a new mechanical model is applied which takes into consideration the real distribution of the fibers in the concrete matrix. Comparing the experimental results with the theoretical model proves that micro fibers help the embedding of macro fibers by reducing micro cracks, and consequently the use of mixed fibers results in an increased fracture toughness.
#ASCE #FRC #makro #micro
