Fracture in fibre reinforced concrete

Fracture behavior of plain and fibre reinforced concrete where studiedusing fracture mechanics principles. It was found that there is no single valuefor plain strain fracture toughness and it appear to change with crack size.Adding steel fibres to concrete results in a large increase fracture toughnessand was found to be due to their effect in reducing the stress field around thecrack tip and lowers the value of stress intensity.Fracture mechanics model was constructed to quantitati vel y predictcritical stress intensity for crack propagation taking into account closingeffects of fibres due to their bridging. Predicted results using the above mentioned fracture mechanics model are in good agreement with experimental results.Empirical correlation based on experimental values relate bet weenfracture toughness and tensile strength and bending strength. Such correlationis useful in predicting the values of fracture toughness using the availableresults of tensile split tests and bending tests.Bending strength was predicted by assuming that the beam is crackedwhere the crack depth equal to the maximum aggregate size and the beam wasassumed to fail when the stress intensity at the crack tip reaches the plain strain fracture toughness. Results of such model were in good agreement with the experimental results.