ABSTRACT
Concrete may be regarded as a composite material in which the hardened cement paste constitutes the continuous phase, and the aggregate particles, which are embedded in the paste, are the discrete phase. Accordingly, it may be surmised that concrete strength will be determined by the strengths of the hardened cement paste and the aggregates, the strength of the paste-aggregate bond and the aggregate concentration in the paste, i.e. the aggregate content in the concrete. This is, indeed, the case but, as it will be seen later, the effect of some of these strength-determining factors is comparatively small and it is ignored, therefore, in everyday practice.
