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Title: Retention of alkali ions by hydrated low-pH cements: Mechanism and Na{sup +}/K{sup +} selectivity

Low-pH cements, also referred to as low-alkalinity cements, can be designed by replacing significant amounts of Portland cement by pozzolanic materials. Their pore solution is characterized by a pH near 11, and an alkali concentration much lower than that of Portland cement. This work investigates the retention of sodium and potassium by a hydrated low-pH cement comprising 60% Portland cement and 40% silica fume. It is shown that sorption of potassium is higher than that of sodium and mainly results from counterion charge balancing of the C-S-H negative surface charge. To explain the greater retention of potassium compared to sodium, it is postulated that potassium, unlike sodium, may enter the interlayer of C-S-H to compensate the negative charges in the interlayer, in addition to the external surfaces. This assumption is supported by structural characterization of C-S-H using X-ray diffraction.
Authors:
;  [1] ;  [2] ;  [1] ;  [2] ;  [1] ;  [2]
  1. Commissariat à l'Énergie Atomique et aux Énergies Alternatives, DEN/MAR/DTCD/SPDE, BP 17171, 30207 Bagnols-sur-Cèze Cedex (France)
  2. ICB, UMR 6303 CNRS Université de Bourgogne, 21078 Dijon (France)
Publication Date:
OSTI Identifier:
22220808
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 51; Other Information: Copyright (c) 2013 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:
36 MATERIALS SCIENCE; ACID NEUTRALIZING CAPACITY; PORTLAND CEMENT; POTASSIUM; RETENTION; SODIUM; SODIUM IONS; SOLUTIONS; SORPTION; SURFACES; X-RAY DIFFRACTION