Nonlinear fracture behaviour of fiber reinforced concrete

Prediction of damage in plain and fiber reinforced concrete due to static loadand low velocity impact is an important step in evaluating the service life ofstructural elements fabricated from them. An extensive study was carried out toevaluate the real role of discrete short fiber in enhancing mechanical propertiesand fracture toughness of conventional high strength concrete (HSC) underboth static and dynamic loads. Furthermore, linear elastic and nonlinearfracture mechanics concepts were adopted in the present analysis. Theapplicability of linear elastic fracture mechanics (LEFM) to the present highstrength fiber reinforced concretes (HSFRC) with high value of coarse to fineaggregate ratio was examined.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/rrr’silica 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 andin hybrid form of equal shares, i.e. making three different mixes of fiberreinforced concrete (FRC). Variable dosages of superplasticizer were added tothe different mixes of FRC to keep their workability at limits. The traditionalmechanical properties tests, i.e. compression, indirect tension, flexural, andfracture toughness test, three point bending (3PB), were conducted. Especiallyfabricated free falling DROP weight impact machine was manufactured at thelaboratory of Zagazig University to conduct the low velocity impact tests oncompression, shear, and flexural specimens.