Physico-chemical transformations of sulfated compounds during the leaching of highly sulfated cemented wastes
- CEA Centre de`Etudes de Saclay, Gif/Yvette (France)
- CEA Centre d`Etudes de Saclay, Gif/Yvette (France)
- Japan Nuclear Fuel Ltd., Tokyo (Japan)
- Taisei Corp., Yokohama (Japan). Technology Research Center
Cementation of sulfated evaporator concentrates leads to highly sulfated low level wastes, (ca. 25% w/w sodium sulfate solution as mix water), which exhibit the presence of U-phase, a sodium-bearing calcium monosulfphoaluminate-like phase. During the leaching of simulated highly sulfated OPC/BFS cements, cured at room temperature and containing U-phase, sodium sulfate, 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 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.
- OSTI ID:
- 561937
- Journal Information:
- Cement and Concrete Research, Vol. 27, Issue 10; Other Information: PBD: Oct 1997
- Country of Publication:
- United States
- Language:
- English
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