Ceramics-Silikáty 32, (1) 85 - 91 (1988)

Ke studiu koroze oxidem siřičitým a uhličitým byly použity vzorky pěnobetonu. Vzorky byly podrobeny korozi v atmosféře SO₂ samostatné nebo ve směsi SO₂ a CO₂ při různé vlhkosti prostředí. Plynné exhaláty negativně ovlivnily jak fyzikálně mechanické, tak i fyzikálně chemické vlastnosti pěnobetonu. Vliv koncentrace oxidu siřičitého je zřetelný zejména na poklesu hodnot pH, výrazněji potom ve směsi CO₂ a SO₂. Konečným produktem sulfatace betonu jen za přístupu vodní páry byl sádrovec, kdežto při opakovaném působení kapalné vlhkosti monosulfát (C₃A.CS.H₁₂), resp. ettringit (C₃A.3CS.H₃₂).

Cellular concrete specimens were subjected to direct effects of sulphur dioxide and SO₂ + CO₂ mixtures at various relative humidities. Physico-chemical and physico-mechanical test showed that corrosion of cellular concrete by sulphur dioxide alone produces crystalline new formations, namely CaSO₃.1/2H₂O, CaSO₄.1/2 H₂O as well as CaSO₄.2H₂O (Figs. 3 through 7) and brings about degradation of the original material which is responsible for decreasing strength (Fig. 2). The effect of relative humidity is decisive at lower SO₂ concentrations, this being not the case at higher concentrations. The influence of SO₂ is essential, being associated with the decrease of pH values (Fig. 1). A more pronounced decrease of pH values resulted from synergic corrosion caused by mixtures of SO₂ and CO₂. During this type of chemical attack, the elevated concentration of CO₂ brings about creation of fine-grained carbonate new formations - vaterite, calcite and possibly aragonite, which further react with SO₂, the reaction rate being dependent on humidity. Alternate exposure to liquid water, in the presence of gypsum, was shown to produce calcium monosulphate while trisulphate was formed in media with higher 802 concentration. Creation of these new formations depends above all on the pH value.