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

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.
Authors:
;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  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)
Publication Date:
OSTI Identifier:
22475499
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 70; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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