TENSION SOFTENING OF FIBRE-REINFORCED CEMENTITIOUS COMPOSITES

Abstract The complete tension softening behaviour of short-fibre-reinforced cementitious composites which exhibit extensive matrix cracking is established by combining a fracture mechanical approach for bridged, discontinuous cracks with a statistical approach for a bridged, through-crack via consistent relationships for the bridging stress. These relationships account for adhesive and frictional bonding of fibres along a crack and are capable of accommodating the effects of fibre content and pre-peak cracking upon the fibre-binder interfacial properties. The combined approach is adapted to mortars based on a conventional high-strength cement binder and a dense, homogeneous cement-silica binder (DSP composite), and good agreement is obtained between the uniaxial tensile strength so calculated and that based on the rule of mixtures. Although the tension softening model needs many geometrical and mechanical properties of the mix constituents, as well as of the hydration products (e.g. interfaces) and the initial post-peak crack configuration, it provides a powerful tool for microstructural design of fibre-reinforced cementitious composites, particularly DSP mortars.

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