Combined impacts of polypropylene fibres on workability, strength and permeability of SCC

The workability, strength and permeability of self-consolidating concrete (SCC), reinforced with polypropylene monofilament fibre, collated fibrillated polypropylene network fibre and a hybrid of these two, are investigated. Combined impacts of polypropylene fibres on SCC are then analysed using the theory of Bingham plastic flow, the principle of fracture mechanics and the composition of microstructure based on scanning electron microscopy. Results show that: (a) in the case of identical fibre volume fraction, the workability of fresh SCC reinforced with polypropylene monofilament fibre is better than that with fibrillated polypropylene network fibre; (b) when the fibre volume fraction is less than 0·10%, strength properties and water impermeability of hardened SCC increase with the fibre addition, and the charge passed increases slightly, but when the fibre volume fraction is higher than 0·15%, the charge increases dramatically; (c) SCC with polypropylene monofilament fibre has better impermeability, but lower static strength than that with fibrillated polypropylene network fibre; (d) compared with ordinary SCC, SCC with the hybrid of 0·05% volume fraction of polypropylene monofilament fibre and 0·05% collated fibrillated polypropylene network fibre has a 22% increase in flexural tensile strength, a 21% increase in splitting strength and a 56% decrease in water penetration depth, and the Coulomb value of chloride ion penetrability is low, about 1013 C at 56 d.