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Physico-chemical transformations of sulphated compounds during the leaching of highly sulphated cemented wastes
Cementation of sulphated evaporator concentrates leads to highly sulphated low level wastes, (ca. 25 % w/w sodium sulphate solution as mix water), which exhibit the presence of 'U-phase,' a sodium-bearing calcium monosulphoaluminate-like phase. During the leaching of simulated highly sulphated Ordinary Portland Cement/Blast Furnace Slag cements, cured at room temperature and containing U-phase, sodium sulphate, and ettringite, physico-chemical transformations have been pointed out (transformation of U-phase into ettringite). Samples having the same chemical composition, but cured at high temperature (maximal temperature during curing: 120 deg C), do not contain ettringite initially, but secondary ettringite is formed during leaching. XRD spectra point out the existence of precipitation fronts (or of phase formation fronts) varying linearly versus the square root of time. The analysis of leaching solutions has provided complementary data used in a code, the aim of which is to assess cement degradation, based on coupling between transport by diffusion and chemical reactions (DIFFUZON code). The U-phase-ettringite transformation is confirmed.
Physico-chemical transformations of sulphated compounds during the leaching of highly sulphated cemented wastes
Cementation of sulphated evaporator concentrates leads to highly sulphated low level wastes, (ca. 25 % w/w sodium sulphate solution as mix water), which exhibit the presence of 'U-phase,' a sodium-bearing calcium monosulphoaluminate-like phase. During the leaching of simulated highly sulphated Ordinary Portland Cement/Blast Furnace Slag cements, cured at room temperature and containing U-phase, sodium sulphate, and ettringite, physico-chemical transformations have been pointed out (transformation of U-phase into ettringite). Samples having the same chemical composition, but cured at high temperature (maximal temperature during curing: 120 deg C), do not contain ettringite initially, but secondary ettringite is formed during leaching. XRD spectra point out the existence of precipitation fronts (or of phase formation fronts) varying linearly versus the square root of time. The analysis of leaching solutions has provided complementary data used in a code, the aim of which is to assess cement degradation, based on coupling between transport by diffusion and chemical reactions (DIFFUZON code). The U-phase-ettringite transformation is confirmed.
Physico-chemical transformations of sulphated compounds during the leaching of highly sulphated cemented wastes
Physikalisch-chemische Umwandlung von sulfathaltigen Verbindungen bei der Auslaugung von hochsulfatreichen Zementabfallstoffen
Lovera, P. (author) / Bescop, P. Le (author) / Adenot, F. (author) / Li, G. (author) / Tanaka, Y. (author) / Owaki, E. (author)
1997
10 Seiten, 9 Bilder, 7 Tabellen, 11 Quellen
Conference paper
English
| British Library Conference Proceedings | 1997
| British Library Online Contents | 1997
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