Thaumasite non-sulphate attack at ambient temperature and pressure
Journal Title: Architecture Civil Engineering Environment - Year 2017, Vol 0, Issue 0
Abstract
One of the products of concrete sulphate corrosion, besides gypsum and ettringite, is thaumasite. The thaumasite is a very dangerous, non binding crystalline phase, which is forming at the expense of C-S-H phase. There was a conviction that the conditions required for the formation of thaumasite in concrete are: source of calcium silicate, sulfate ions, carbonate ions and a very wet, cold (below 15°C) environment. The corrosion of concrete caused by the external source of sulphate ions dur- ing which thaumasite is formed was called thaumasite sulphate attack (shortly TSA). While the TSA is recognized, the thau- masite non-sulphate attack (T n S A ) must be highlighted, because is also possible. The purpose of this work is to show that thaumasite, or solid solutions of Ett-Th (ettringite with thaumasite) are able to form in hardened cement paste with- out external source of sulphate ions, at ambient temperature and pressure (25±2°C (298.15 K) and 102±1 kPa). The exper- iment appeared on thaumasite formation in corroded specimen made of CEM I (Portland cement) and of CEM III (slag cement) after 4 days of immersion in saturated water solution of NH4Cl.
Authors and Affiliations
B. Słomka-Słupik, A. Zybura
Keywords
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