Mixed Mode Crack Propagation In Fiber Reinforced Concrete

Studies of mode I Fracture of fib er reinforced concrete (FRC) haveconfirmed the applicability of fracture mechanics concept to FRC. However,despite the successful applications of fracture mechanics to mode I fracture ofconcrete, the failure mechanisms, the effect of KII /K1 on the fracture behavior offib er reinforced concretes and the associated energy dissipation in mixed mode crack propagation (Mode 1& Mode II) are still not clearly manifested.Mixed-mode fracture characteristics of FRCs were investigated experimentally.Dolomite as a coarse aggregate with 14 mm maximum aggregate size andsiliceous sand were mixed together with a ratio of 1: 1.675. Cementitiousmaterial content of about 443 Kg/m3 ordinary Portland cement and 49 Kg/m3silica fume was used and w/c was 0.29. Two different types of short fibers,namely galvanized steel and alkaline resistance glass fibers with 0.8% volumefraction and length of 2.5 cm, were added to plain concrete mix separately and in hybrid form of equal shares, i.e. making three different mixes of fib er reinforced concrete (FRC). Variable dosages of superplasticizer were added to the different mixes of FRC to keep their workability at limits. The traditional mechanicalproperties tests, i.e. compression, indirect tension, flexural were examined.Different test configurations of fracture toughness tests i.e. three point bending (3PB), and four point shear (4PS), with different notch locations and sizes were conducted at the laboratory of Zagazig University. The test results were interpreted using both linear and nonlinear fracture mechanics concepts .In addition a study on large scale reinforced concrete beams with different pre notchpatterns of plain and steel fiber reinforced concrete was conducted at thelaboratory of the University of Waterloo as a part of Egyptian governmental scholar ship to Canada.