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Sulfuric acid attack on hardened paste of geopolymer cements. Part 2. Corrosion mechanism at mild and relatively low concentrations
At mild concentrations of sulfuric acid (pH = 2), the first step of the total corrosion process, i.e. the ion exchange reaction between the charge compensating cations of the framework (Na(+) and Ca(2+) and H(+) or H3O(-) ions from the solution along with an electrophilic attack by acid protons on polymeric Si-O-Al bonds resulting in the ejection of tetrahedral aluminium from the aluminosilicate framework, continues until it results in the formation of shrinkage cracks. When shrinkage cracks become wide enough, sulfate anions diffuse into the cracks, and react with the counter-diffusing calcium ions, resulting in the formation and deposition ofgypsum crystals. At relatively low concentrations of sulfuric acid (pH nearly 3) and for limited periods of exposure time (<= 90 days), the corrosion mechanism is exactly the same as that of pH 3 nitric acid, i.e. simply leaching of charge compensating cations and ejection of tetrahedral aluminum with no gypsum deposition.
Sulfuric acid attack on hardened paste of geopolymer cements. Part 2. Corrosion mechanism at mild and relatively low concentrations
At mild concentrations of sulfuric acid (pH = 2), the first step of the total corrosion process, i.e. the ion exchange reaction between the charge compensating cations of the framework (Na(+) and Ca(2+) and H(+) or H3O(-) ions from the solution along with an electrophilic attack by acid protons on polymeric Si-O-Al bonds resulting in the ejection of tetrahedral aluminium from the aluminosilicate framework, continues until it results in the formation of shrinkage cracks. When shrinkage cracks become wide enough, sulfate anions diffuse into the cracks, and react with the counter-diffusing calcium ions, resulting in the formation and deposition ofgypsum crystals. At relatively low concentrations of sulfuric acid (pH nearly 3) and for limited periods of exposure time (<= 90 days), the corrosion mechanism is exactly the same as that of pH 3 nitric acid, i.e. simply leaching of charge compensating cations and ejection of tetrahedral aluminum with no gypsum deposition.
Sulfuric acid attack on hardened paste of geopolymer cements. Part 2. Corrosion mechanism at mild and relatively low concentrations
Aggresivität von Schwefelsäure an ausgehärteter Geopolymerzementpaste. Teil 2: Korrosionsmechanismus bei milder und relativ geringer Konzentration
Allahverdi, A. (Autor:in) / Skvara, F. (Autor:in)
Ceramics Silikaty, Prag ; 50 ; 1-4
2006
4 Seiten, 5 Bilder, 16 Quellen
Aufsatz (Zeitschrift)
Tschechisch
Geopolymer , Zement , Schwefelsäure , Korrosion , Konzentration , Anion , Kation , Ionenaustausch , Schrumpfriss
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Nitric acid attack on hardened paste of geopolymeric cements, Part 2
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Nitric acid attack on hardened paste of geopolymeric cements, Part 1
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Corrosion of hardened cement paste by acid attack
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