Identification of fracture parameters of fiber reinforced concrete beams made of various binders

Geopolymer concrete (GPC) is currently a hot research area. This work aims to study the fracture behavior of beam specimens with and without steel reinforcement and cast with different binders. Forty-eight notched-beams with dimensions of 100×150×1000 mm were used and tested in three-point bending loads. Different variables taken into consideration mainly, notch height (0, 50, 75 mm), reinforcement ratio (0%, 17%), replacement ratio of fly ash with cement (0%, 20%, 30%, 50%) in GPC, replacement ratio of cement with fly ash (0%, 50 %) in Portland cement concrete (PCC), polypropylene fibers content (0%, 0.5%, 0.75%). were studied. The load-deflection, and crack mouth opening displacement (CMOD) were considered as the characteristic responses at various stages of loading. Fracture Toughness (KIC), Fracture Energy (GF), Characteristic Length (Ɩch), Brittleness (B), J- Integral (JIC) were calculated to evaluate the fracture behavior of the beam specimens without reinforcement. Whereas, brittleness number (NP), dimensionless number (S), and the ratio of plastic moment / critical moment (MP/MF) were calculated to evaluate the fracture behavior of the beam specimens with reinforcement. The results revealed that, the GPCs exhibit similar behavior and fracture properties that those determined in PCCs. Hence, the inclusion of polypropylene fibers to different concrete mixtures noticeably enhanced their fracture properties, while the brittleness was reduced with the increase of the polypropylene fibers content.