Influence of sodium borate on the early age hydration of calcium sulfoaluminate cement

Journal Article · Wed Apr 15 00:00:00 EDT 2015 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2014.12.010· OSTI ID:22475499

Champenois, Jean-Baptiste; Dhoury, Mélanie ^[1]; Mercier, Cyrille ^[2]; Revel, Bertrand ^[3]; Le Bescop, Patrick ^[4]; Damidot, Denis ^[5]

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1. CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze Cedex (France)
2. LMCPA, Université de Valenciennes et du Hainaut Cambrésis, 59600 Maubeuge (France)
3. Centre Commun de Mesure RMN, Université Lille1 Sciences Technologies, Cité Scientifique, 59655 Villeneuve d'Ascq Cedex (France)
4. CEA, DEN, DPC, SECR, F-91192 Gif-sur-Yvette (France)
5. Ecole des Mines de Douai, LGCgE-GCE, 59508 Douai (France)

Calcium sulfoaluminate (CSA) cements are potential candidates for the conditioning of radioactive wastes with high sodium borate concentrations. This work thus investigates early age hydration of two CSA cements with different gypsum contents (0 to 20%) as a function of the mixing solution composition (borate and NaOH concentrations). Gypsum plays a key role in controlling the reactivity of cement. When the mixing solution is pure water, increasing the gypsum concentration accelerates cement hydration. However, the reverse is observed when the mixing solution contains sodium borate. Until gypsum exhaustion, the pore solution pH remains constant at ~ 10.8, and a poorly crystallized borate compound (ulexite) precipitates. A correlation is established between this transient precipitation and the hydration delay. Decreasing the gypsum content in the binder, or increasing the sodium content in the mixing solution, are two ways of reducing the stability of ulexite, thus decreasing the hydration delay.

• OSTI ID: 22475499
• Journal Information: Cement and Concrete Research, Vol. 70; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
BINDERS
BORATES
CALCIUM COMPOUNDS
CEMENTS
CONCENTRATION RATIO
CORRELATIONS
GYPSUM
HYDRATION
MATHEMATICAL SOLUTIONS
PH VALUE
PHASE STABILITY
PRECIPITATION
REACTIVITY
SODIUM COMPOUNDS
SODIUM HYDROXIDES