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Chemical Properties of Metal-Silicates Rendered by Metal Exchange Reaction

Longo, Roberto C., Königer, Franz, Nefedov, Alexei, Thissen, Peter
ACS sustainable chemistry & engineering 2019 v.7 no.9 pp. 8449-8457
biological resistance, carbon dioxide, carbonates, cement, concrete, construction materials, corrosion, magnesium, phase transition, physicochemical properties, porosity
Calcium-silicates and calcium-silicate-hydrates (CS and CSH) are well-known as the most important building material, cement. Both CS and CSH phases react fast with CO₂ from the atmosphere. Due to the porosity of cement and concrete, such reaction goes deep into the material, producing phase transformations, crack formation and propagation. The aim of this work is 2-fold. In the first part, we compare the reaction of CO₂ with CSH phases and with magnesium-silicate-hydrates (MSH). Surprisingly, MSH did not show any contamination of carbonates in the infrared spectra. While the reaction of CO₂ with CSH has been well studied and explained, there is currently no explanation about the resilience of MSH to the interaction with CO₂. For the first time, the atomistic details of the reaction of CO₂ with MgSiO₃ are shown, and the chemical resistance of MgSiO₃ against CO₂ and other relevant chemicals for corrosion of cement and concrete is explained. Second, we demonstrate that Mg and other metals can undergo an exchange in situ process in CS and CSH phases. Depending on the type of metal exchanged, a completely new platform for rendering the properties of cement and concrete surfaces against corrosion is developed.