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eq < 0.60% of the cement mass, according to EN 197-1 European standard for cement, [40] or by limiting the total alkali content in concrete (e.g., less than 3 kg Na 2 O eq /m 3 of concrete for a CEM I cement (OPC)). Example of standard for concrete in Belgium: NBN EN 206 and its national supplement NBN B 15-001; [41] [42]
A reducing atmosphere is an atmosphere in which oxidation is prevented by absence of oxygen and other oxidizing gases or vapours, and which may contain actively reductant gases such as hydrogen, carbon monoxide, methane and hydrogen sulfide that would be readily oxidized to remove any free oxygen.
Corrosion may occur where stale sewage generates hydrogen sulfide gas into an atmosphere containing oxygen gas and high relative humidity. There must be an underlying anaerobic aquatic habitat containing sulfates and an overlying aerobic aquatic habitat separated by a gas phase containing both oxygen and hydrogen sulfide at concentrations in excess of 2 ppm.
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When atmospheric carbon dioxide (CO 2), or carbonate ions (HCO − 3, CO 2− 3 dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, Ca(OH) 2) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite).
A concrete surface is alkaline, making it difficult for microbes to germinate. However, chemical processes by the environment and microorganisms themselves cause changes in the concrete. Environmental conditions combined with carbonization caused by select microbes fabricate negative changes in the pH of the concrete.
Electrical steel is one material that uses decarburization in its production. To prevent the atmospheric gases from reacting with the metal itself, electrical steel is annealed in an atmosphere of nitrogen, hydrogen, and water vapor, where oxidation of the iron is specifically prevented by the proportions of hydrogen and water vapor so that the only reacting substance is carbon being oxidized ...
Simple, low-cost steps can also make a difference. Regularly clean your roof and gutters to remove flammable materials like leaves and twigs. Keep flammable materials such as mulch, firewood and ...