Effect of fiber on the crack width, tortuosity and permeability of concrete

In order to study the effects of different fibers (steel fiber (SF), macro polypropylene fiber (Macro-PP) and micro polypropylene fiber (Micro-PP) on the permeability of fractured concrete under loading, different cracks(50-200 μm) were introduced by splitting test. The effects of different fibers on the crack width and tortuosity after unloading were compared. The influence of different fiber types, dosage and hybrid methods on the permeability of concrete with different crack width under load was analyzed by using the permeability test setup. It is found that the permeability decreases by 95.7%, if the steel fiber content increases from 25 kg/m³ up to 55 kg/m³. Compared with single-doped SF, the hybrid use of SF and macro-PP fibers indicates clear positive composite effect on the permeability; It has little change in permeability of cracked concrete reinforces with SF, micro-PP fiber and the combination of both fibers. The investigation demonstrates that the micro-PP fibers show low effect on restriction of the structural crack and the permeability. Steel fibers and macro-PP fibers restrictes the expansion of cracks effectively, increases the tortuosity of crack surface greatly, and reduces the permeability of cracked concrete greatly.