Influence of the parameters of cementing materials on transfer properties

Our study aims for characterizing the influence of the parameters of cementing materials composition on the two properties of transfer: the diffusion of chlorides and the oxygen permeability. An experimental database on three types of materials (cement pastes, mortars and concretes) with two different water-cement ratios was established. The information concerning the porous structure of material was obtained by four different techniques (degree of hydration, open porosity measured by water saturation, porosity measured by mercury penetration and observations at SEM). The effective coefficient of diffusion of the material was obtained by the use of an accelerated method under electrical field (LMDC Diffusion Test) and the apparent and intrinsic oxygen permeability were evaluated by the mean of a permeameter to constant charge (CEMBUREAU Method). The influence of the characteristics of the granular phase studied by the transfer properties is highly dependent on the transfer mechanism evaluated: for the low cement-water ratio and high aggregate content, low coefficients of diffusion were obtained with calcareous aggregate, a high fineness modulus and a cement CPA CEM I 52. 5 R. A slight decrease of the diffusivity as function of the aggregate size is verified. Similar conclusions were obtained for permeability with the exception of the fineness modulus. A second part is devoted to the exploration of different models enumerated in the literature aiming for connecting the transfer properties and the characteristics of the microstructure. The predictions for diffusivity and permeability obtained with these models are limited. (author)