80 research outputs found
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/mÂł). 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, constrictivityâŠ) 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
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