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In the current work, an extensive chloride-profiling programme was taken over a seven year period on a series of nine concrete monoliths placed at a marine location. These monoliths were 2.0m high and octagonal in plan with each vertical face 0.66m wide. The monoliths were placed at predefined locations to represent environmental exposure conditions of XS1 (exposed to airborne salt and not in direct contact with sea water) and XS3 (tidal, splash and spray zones) as defined with European Standard EN206-1. The concrete monoliths were constructed in groups of three (one each at the locations defined above): one group, which was used as a benchmark, represented normal portland cement concrete; the second group of monoliths was treated with waterproofing agent (caltite) added at the time off mixing and the third was treated with silane. Chloride profiles were taken at a number of positions on each monolith which were subsequently used to evaluate the performance of the concrete to chloride ingress for different exposure conditions.

Different types of carbonaceous materials have been added to concrete mixes and their effect on the mechanical properties and the corrosion of embedded steel have been studied. Using a constant water/cement ratio of 0.42 the flexural and compression strengths of concrete with different amounts of carbonaceous materials and different curing periods have been determined. Also, the effect of adding some amount of silica fume to the mix formulation has been considered. The addition of small quantities of carbonaceous materials to the mix produces an increase of mechanical strengths and a reduction of the concrete permeability. Due to this smaller permeability the corrosion levels of embedded steel are lower as compared to the ones in an admixture-free mix, in spite of the higher electrical conductivity of the composite.

In the framework of radioactive waste storage, the French atomic energy agency needs to design a concrete container with a service life of 300 years. Regarding durability and mechanical problems, we propose a mixture of proportions of high performance and self compacting concrete including a ternary blend. In order to evaluate the durability of such a formulation a large set of experiments was carried out. Gas and water permeability, diffusivity of chlorides, carbonation, freezing and thawing resistance were studied in laboratory. All results obtained during this study show that the concrete mixture proportions chosen are in accordance with the durability criteria imposed for security reasons. Nevertheless several complementary tests were performed to investigate the microstructure of the material, such as x ray diffraction, thermo-gravimetric analysis or microscope analysis, in order to confirm the results obtained for the durability indicators. In this paper we present all the results obtained during this experimental study, which has been carried out over two years. All values of durability indicators obtained will be introduced in mathematical models in order to verify the service life of 300 years.

Instead of the conventional method for evaluating an apparent diffusion coefficient of chloride ions (Cl-) from experimental Cl- concentration profile, this study introduces a novel method to estimate an effective diffusion coefficient (De) and non-linear binding parameters (a, b) of Cl- from a Cl- concentration profiles measured by electron probe micro analysis (EPMA). This estimation is made by the combination of numerical analysis by the finite-difference method of the non-linear diffusion equation and optimizing calculations. By using this method, De, a and b are estimated for several kinds of concrete having various type of cement and several levels of water-cement ratio. The estimated values of De show a positive linear relationship with values of De obtained by migration tests. The estimated values of a show a good correlation with the alumina content in cement as expected. These results indicate the validity of this method for estimating parameters required for predicting future Cl- concentration profiles.

Inhibitors against chloride induced corrosion of reinforcement in concrete have been briefly reviewed with emphasis on anodic inhibitors. A program designed to compare the performance of the common anodic corrosion inhibitor calcium nitrite, Ca(NO2)2, with the more recently discovered anodic inhibitor calcium nitrate, Ca(NO3)2, is discussed in detail. Calcium nitrate has been proven to inhibit reinforcing steel corrosion initiated by both intruded and intermixed chloride in long term tests, and to out-perform calcium nitrite in an accelerated test. The effect of the two admixtures on concrete properties is compared as well. It is shown by theory that the mechanism of nitrate and nitrite as corrosion inhibitors is similar in alkaline conditions like concrete. The kinetics for the nitrate reaction are slower than for nitrite, but this is only relevant for rapid tests since reinforcing steel corrosion in practice is a rather slow process. According to theory, calcium nitrate offers a larger buffer than calcium nitrite. Other advantages of using calcium nitrate rather than nitrite as a corrosion inhibitor are that it is cheaper, less harmful and more available. Between 3 - 4 % calcium nitrate of cement by weight seems sufficient to protect the reinforcing steel against corrosion due to intruded chlorides from the environment or intermixed chlorides from, for example, contaminated aggregate.