EFFECTS OF AGGREGATE SIZE AND OF CEMENT TYPE ON CONCRETE MECHANICAL BEHAVIOUR AND ON GAS PERMEABILITY EVOLUTION WITH LOADING

This study concerns impact of aggregate size and of cement type on mechanical behavior and gas permeability evolution with mechanical loading of concrete-like materials. The work has been carried out using two types of materials: a microconcrete and a concrete, the both with the same water-to-cement ratio, as well as the same aggregate volume fraction. Specimens of the formulated materials have been submitted to compressive strength, porosity (MIP) and gas permeability tests, as well as to indirect tensile in the Brazilian splitting test till certain damage levels. Gas permeability have then been measured during loading for specimens loaded in indirect tension. A special lab-made device has been developed to control tensile loading in the pre-peak and the post-peak phases and to measure gas transfer during loading. For all the tested materials, the results emphasize that for both cement types, CEM I or CEM III, compressive and tensile strengths decrease and gas permeability increases, when aggregate size increases. Moreover, the obtained results highlight that the effects of tensile damage on gas permeability may be separated from the effects of aggregate size and cement type. This behaviour, independent on cement type, represents a strong potential for concrete modelling.