Study of reinforced concrete slabs after three years of cathodic protection under severe conditions

International audienceThe objective of this study is to determine the influence of cathodic protection on the properties of concrete cover in concrete slabs. To accelerate deterioration, the slabs were subjected to freezing and thawing cycles and sprayed with sodium chloride solution. Cathodic protection was applied to the reinforcements for three years. Then, the test pieces underwent physico-chemical analysis. Scanning electron microscopy and X-ray spectrometry were used to study the reinforcement-concrete interface, in particular for detecting alkali-silica reaction due to the alkalization. Carbonation depths, chloride penetration profiles and examinations of the reinforcements showed the good condition of the concrete cover and the beneficial effect of the cathodic protection of embedded steel

A homoleptic SPS-based complex and a double-cubane-type sulfur cluster of an actinide element

International audienc

Chloride diffusion in cement materials at different leaching states : an experimental and numerical study

Due to common heavy snowfall in winter, concrete structures in cold countries are regularly in contact with water. Hence, concrete undergoes abnormal leaching of ionic species present inside the liquid pores of the material. The leaching slowly degrades the material, which can have an influence on the diffusive behaviour of the ionic species diffusing inside, like chloride, coming from the de-icing salts and responsible for the corrosion of the steel reinforcements present in the reinforced concrete. In this work, an experimental and numerical study is proposed to better understand the influence of the leaching state of cementitious material on the diffusive behaviour of chloride ions. Natural and accelerated diffusion tests were performed on samples of hydrated cement paste and concrete with lower chloride concentrations (50 mol/m³). The materials were conserved at different leaching state with care not to degrade the microstructure: Safe (S), Partially Leached (PL) and Leached (L). These various tests were then simulated using the PhreeqC reactive transport software to quantify the chloride diffusion. The numerical model allows distinguishing the influence of the geometry of the material (porosity, tortuosity, constrictivity…) to the chemical reactions that take place between chloride ions and the cementitious phases. It then appeared that chloride ions do not diffuse by the same way depending on the leaching state of the material. Same observations are done on hydrated cement paste and concrete samples. In a safe material, the chloride diffusion is lower than in a leached material. This difference observed seems not to provide from the material geometry nor the chemical reactions. The numerical model developed confirms this hypothesis as it allows to both distinguish and quantify their influence on the chloride diffusion. This study, therefore, highlights the importance of considering the leaching effects in the prediction model for concrete structure durability in cold countries