| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4674814 | Procedia Earth and Planetary Science | 2015 | 4 Pages |
Degradation of concrete caused by the formation of secondary hydrous sulfate minerals (e.g. thaumasite, ettringite and gypsum) can cause serious problems concerning the durability of building structures. To provide a better understanding of the formation conditions of these sulfate minerals we have investigated thaumasite (Ca3Si(OH)6(CO3)(SO4)•12H2O), ettringite (Ca6Al2(SO4)3(OH)12•26H2O) and gypsum (CaSO4•2H2O) with the aim of extracting crystal (i.e. structural) water and analysing its stable O and H isotopes. The crystal water was released and collected using a heating and vacuum distillation method followed by δ2H and δ18O analyses on a liquid water isotope analyser. Results indicated that this setup is highly promising to trace the isotopic composition of water involved in the precipitation of the various hydrous sulfate mineral. Based on our data we calculated O and H isotope fractionation factors for thaumasite and ettringite between crystal and aqueous H2O. The results agree with previous findings that the sulfate mineral formation, responsible for concrete damage, is occurring in highly concentrated solutions (5000 up to 30000 mg L-1 SO4) due to evaporation.
