THE INFLUENCE OF AGGREGATE ON THE COMPRESSIVE STRENGTH OF NORMAL AND HIGH-STRENGTH CONCRETE

This paper presents a comprehensive theory describing the influence of aggregate on the compressive strength of concrete. A first distinctio n is made between topological and mechanical aspects. The former; call ed confining effect, includes the effect of the volume and the maximum size of the aggregate, which are best described by means of a single physical parameter the maximum paste thickness (MPT). MPT is defined a s the mean distance between two adjacent coarse aggregates. Equations are given to calculate MPT, and its effect on compressive strength. Th e second type of effect concerns the bond between paste and aggregate (bond effect), and a limitation of the strength that originates in the intrinsic strength of the rock (ceiling effect). Experiments have bee n performed on 13 mixtures made lip with 5 sources of aggregate, in or der to compare the strength development on pure paste vs. composites ( mortar and concrete). The quantitative assessment of the three effects of aggregate on compressive strength gives an accuracy close to 2.2 M Pa, on the studied mixes. Such a model is suitable to be incorporated into software for computer-aided mixture-proportioning and quality-con trol of structural concrete, up to the high-performance concrete range .