Title: The Influence of Aggregate on the Compressive Strength of Normal and High-Strength Concrete

Author(s): Francois de Larrard and Albert Belloc

Publication: Materials Journal

Volume: 94

Issue: 5

Appears on pages(s): 417-426

Keywords: aggregates; bond; compressive strength; high-performance concrete; mathematical model; maximum paste thickness; water-cement ratio;

DOI: 10.14359/326

Date: 9/1/1997

Abstract:
This paper presents a comprehensive theory describing the influence of aggregate on the compressive strength of concrete. A first distinction is made between topological and mechanical aspects. The former, called 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 as the mean distance between two adjacent coarse aggregates. Equations are given to calculate MPT, and its effect on compressive strength. The second type of effects 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 been performed on 13 mixtures made up with 5 sources of aggregate, in order 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 MPa, on the studied mixes. Such a model is suitable to be incorporated in a software for computer-aided mixture-proportioning and quality-control of structural concrete, up to the high-performance concrete range.