The role of material fabric in confined concrete

Abstract

The paper is a comparative study of the role of material fabric in unconfined concrete and in concrete subjected to external confinement. In unconfined concrete, the material fabric is the principal reason for the early onset of shear bands in specimens with rounded aggregates. Anisotropy in the material fabric also determines the strength of the “internal confinement mechanism,” and contributes to higher macro strength in specimens with angular aggregates. In contrast, in confined specimens, fabric isotropy, typical of rounded aggregates, is found to be more suited to capture the benefits of external confinement. With increase in axial strain, the fabric dependent anisotropic contribution grows more slowly in specimens with rounded aggregates. This facilitates rapid mobilization of confining pressure, and contributes to the higher confining efficiency of such specimens. However, higher confining pressure in specimens with rounded aggregates also results in such specimens being more susceptible to mortar damage and Mode II interface fracture than their angular counterparts.