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The cracks in concrete are a fast transport path for chlorides and influence the service life of concrete structures in chloride environments. This study aimed to reveal the effect of crack geometry on chloride diffusion in cracked concrete. The chloride diffusion process in cracked concrete was simulated with the finite difference method by solving Fick’s law. The results showed that the apparent chloride diffusivity was lower in more tortuous cracks, and the cracks with more narrow points also showed lower apparent chloride diffusivity. For tortuous cracks, a higher crack width meant relatively more straight cracks, and consequently, higher apparent chloride diffusivity, while a lower crack width resulted in more tortuous cracks and lower apparent chloride diffusivity. The crack depth showed a more significant influence on the chloride penetration depth in cracked concrete than crack geometry did. Compared with rectangular and V-shaped cracks, the chloride diffusion process in cracked concrete with a tortuous crack was slower at the early immersion age. At the same crack depth, the crack geometry showed a marginal influence on the chloride penetration depth in cracked concrete during long-term immersion.

The human retina is a complex neural tissue that detects light and sends visual information to the brain. However, the molecular and cellular processes that underlie aging primate retina remain unclear. Here, we provide a comprehensive transcriptomic atlas based on 119,520 single cells of the foveal and peripheral retina of humans and macaques covering different ages. The molecular features of retinal cells differed between the two species, suggesting the distinct regional and species specializations of the human and macaque retinae. In addition, human retinal aging occurred in a region- and cell-type- specific manner. Aging of human retina exhibited a foveal to peripheral gradient. MYO9A− rods and a horizontal cell subtype were greatly reduced in aging retina, indicating their vulnerability to aging. Moreover, we generated a dataset showing the cell-type- and region- specific gene expression associated with 55 types of human retinal disease, which provides a foundation to understand the molecular and cellular mechanisms underlying human retinal diseases. Together, these datasets are valuable for understanding the molecular characteristics of primate retina, as well as the molecular regulation of aging progression and related diseases.

International audience; The increasing international interest in contemporary architecture has drawn attention to the numerous listed buildings made of reinforced concrete in Europe, and especially in France. The main source of deterioration of this cultural heritage is the corrosion of rebars through carbonation or chloride contamination, but also often by a combination of both. The present study explored this combined corrosion mechanism in reinforced concretes, and investigated Electrochemical Chloride Extraction (ECE) as a technique to stop or decrease corrosion. The analytical approach was based on physico-chemistry, electrochemical measurements, Raman spectroscopy and SEM examinations. The results evidenced the aggressiveness of the combined carbonation and chloride-induced corrosion, and demonstrated the efficiency of the ECE treatment in terms of chloride extraction and reduction of corrosion rate. It appears that ECE treatment only reduces corrosion activity by increasing pH to a value of 10. Nevertheless, the long term durability of the treatment is questionable as the return to a sound concrete passivity is not obtained.

Permeability of concrete is regarded as a basic indicator of its durability. This paper proposed a simple model to predict the permeability of engineered cementitious composites (ECC), which are fiber reinforced cementitious composites with extremely high ductility and toughness. The permeability of cement paste in ECC was firstly determined based on the general effective media theory. The needed microstructure information of cement paste was obtained from a simulated microstructure. Porosity of the interfacial transition zone (ITZ) was obtained with an ITZ porosity model, and then used to calculate the permeability of ITZ. The permeability of the matrix was determined according to the general self-consistent scheme, and the influence of fiber was simplified with its volume fraction. The calculated permeability of ECC was verified with results from water permeability tests and the accuracy of the model was acceptable for cement-based materials.

International audience; The aim of this study was to assess the efficiency of a realkalisation treatment using sacrificial anodes applied to reinforced concrete degraded by carbonation. Analytical determinations (acid/base indicators, quantitative pH, alkaline profiles, SEM and micro-Raman) together with electrochemical characterizations (rest potential, impedance, linear polarisation resistance and corrosion current densities) were performed on artificially carbonated slabs, before and after treatment (mainly 15 days, 11 weeks, 6 and 12 months). The treatment efficiency was demonstrated by an increase of pH and by an alkaline ion penetration in the concrete cover. Rest potential and corrosion current densities indicated a slight decrease of the rebar corrosion activity. Complementary Raman spectroscopy showed a change in the oxide species and SEM observations indicated that the cement matrix remained almost unchanged. (C) 2011 Elsevier Ltd. All rights reserved.