Aggregate size effects on the mechanical behaviour and on the gas permeability at damaged state of cement-based materials with and without slag

Abstract

The purpose of this article is to investigate the effects of aggregate size on the mechanical and mass transfer behavior of concrete. The experimental work is carried out using three types of materials: microconcrete, concrete and macroconcrete. All these materials chosen have the same water-to-cement ratio and the same aggregate volume fraction. They are prepared using two different cement types, CEM I and CEM III as alternative binder for environmental considerations. In order to study the evolution of the microstructure due to changes in aggregate size, gas permeability, water and mercury porosity measurements are first carried out on sound materials. Then, some specimens of the formulated materials are subjected to a series of controlled uniaxial compression cycles in the pre-peak phase to achieve intended damage levels corresponding to 30, 60 or 80% of their compressive strength, respectively. Gas permeability is then measured on the damaged specimens after unloading. For all the materials, the results suggest that mechanical strength decreases and gas permeability increases when aggregate size increases. Use of cement CEM III with slag show an increase of mechanical properties and reducing the strain. But the slags seems to be more sensitive to the drying that can be increase the strain and strength characteristics. Moreover, the results also show that the effect of compressive damage on permeability may be separated from the effect of aggregate size using two distinct functions. As a result, such behaviour, independent of cement type, is a major advantage for concrete modelling.

Keywords:

• Aggregate size effect
• concrete
• slag
• mechanical behaviour
• gas permeability
• damage

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support received from the national network MAREVA (MAquette de REalité Virtuelle d’Aménagement portuaire) and the French Interdepartmental Funds is gratefully acknowledged.