ABSTRACT
The properties of fibre reinforced cementitious materials are dependent on the structure of the composite. Therefore, in order to analyze these composites, and to predict their performance in various loading conditions, their internal structure must be characterized. The three components that must be considered are:
2.1 MATRIX
The bulk cementitious matrix is not significantly different from that in other cementitious materials, and it can be divided into two types depending on the particulate filler (aggregate) which it contains: paste/mortar (cement/sand-water mix) and concrete (cement-sand-coarse aggregate-water mix). Fibre reinforced cement pastes or mortars are usually applied in thin sheet components, such as asbestos cement, which are used mainly for cladding. In these applications the fibres act as the primary reinforcement and their content is usually in the range of 5 to 20% by volume. In fibre reinforced concretes, the fibre volume is much lower (<2% by volume) and the fibres act as secondary reinforcement, mainly for the purpose of crack control. The properties of such matrices, and their control through changes of the mix composition, are well documented in various textbooks.1-3
2.2 FIBRES
A wide range of fibres of different mechanical, physical and chemical properties have been considered and used for reinforcement of cementitious matrices, as outlined in Chapter 1. The fibre reinforcing array can assume various geometries and in characterizing its nature two levels of geometrical description must be considered: (1) the shapes of the individual fibres, and (2) their dispersion in the cementitious matrices (Fig. 2.1).
