Preventive action of organosilicon treatments against disfigurement of wood under laboratory and outdoor conditions

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In situ, in vitro and in silico analysis of coating performance

Service life prediction (SLP) is a complex yet essential method for analysing coating performance. Accurate and precise assessment is crucial for a strong position on the market. Correct knowledge of the critical failure points, maintenance/replacement frequency and related costs are part of this approach. This paper describes the scale-dependent tools within a bio-engineering framework that are applied for coating research, ranging from modelling, X-ray tomography, lab testing, controlled fungal infestation up to continuous moisture set-ups and large-scale window frame weathering

Moisture conditions in coated wood panels during 18 months natural weathering at five sites in Europe

Wood moisture content of coated panels of Scots pine sapwood was recorded during 18 months natural weathering in Vienna by logging electric resistance and temperature near the surface. Eight coating systems with various film thicknesses were used, including three solvent borne alkyd stains, three water borne acrylic stains and two water borne acrylic paints. At five sites in Europe wood moisture content of panels coated with three solvent borne alkyd stains, a brow acrylic stain and a white opaque acrylic paint was recorded weekly by changes in panel mass. Fluctuations in wood moisture content were influenced by the film thickness, moisture protection and colour of the coating systems used. Degradation phenomena led to decreasing moisture protection of less durable coating systems over time of exposure. Differences between the exposure sites were relatively low, except the site in the UK where moisture conditions were higher

Modelling of long-term dynamic leaching tests applied to solidified/stabilised waste

International audienceThe paper aims at simulating the closed-system dynamic leaching of a cement-based monolith containing lead with the numerical reactive transport code HYTEC in a 3D-cylindrical geometry. The model considers, simultaneously, the chemical evolution of pore water, the progression of mineralogical alteration fronts, and the concomitant release of elements from the S/S waste. In good agreement with the experiment, element releases were found to be mainly controlled by either diffusion (Na, K, and, to a lesser extent, Cl), by surface dissolution (Ca, Si) or by a mixed evolution (Pb, SO4). All of the calculated mineralogical transformations take place in a thin layer beyond the monolith surface. Consequently, modelling of Ca, Si and SO4 releases was quite sensitive to the node size of the simulation grid and was improved by taking into account the increase of porosity and effective diffusion coefficient due to mineral dissolution in the leached layer. In agreement with experimental results, the deepest front corresponds under closed-system conditions to portlandite dissolution and calcium silicate hydrates CSH 1.8 transformation into CSH of lower Ca/Si ratio. A second, distinct and intermediate, front is made by ettringite dissolution. The network of CSH is globally preserved in the leached layer, complete dissolution occurring over a very small thickness only. Finally, hydrotalcite precipitation in the leached layer is expected by modelling due to pH drop

Siberia

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