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Title: Kinetics of lime/bentonite pozzolanic reactions at 20 and 50 °C: Batch tests and modeling

The effects of duration (1–100 days) and temperature (20 and 50 °C) were assessed from batch tests for Ca-bentonite mixed with 10 wt.% lime. The pozzolanic processes were monitored over time by {sup 29}Si NMR (Cement Concr. Res. 42, 2012), TGA-DTA, XRD and chemical analysis. Modeling considered kinetics and thermodynamics of mineralogical transformations and cation exchange. Kinetic laws were dependent on pH and temperature (Arrhenius energy). Lime hydration occurs within hours, modifying the bentonite exchangeable population and increasing the pH. These alkaline conditions initiate the pozzolanic reactions in a second stage. The rate-limiting step is the dissolution kinetics of the bentonite minerals, i.e. a relatively fast and total consumption of cristobalite in parallel to a long-term slower dissolution of montmorillonite. First C–S–H and then C–A–S–H are formed consequently. Temperature speeds up the pozzolanic reaction kinetics by a factor 5 from 20 to 50 °C, corresponding to an apparent activation energy of 40–50 kJ/mol.
Authors:
 [1] ;  [2] ;  [3] ;  [2]
  1. Mines-ParisTech (Ecole des Mines de Paris), Centre de Géosciences, 35 Rue St-Honoré, 77305 Fontainebleau Cedex (France)
  2. LUNAM, IFSTTAR, Institut Français des Sciences et des Technologies des Transports, de l'Aménagement et des Réseaux, BP 4129, route de Bouaye, 44332 Bouguenais (France)
  3. (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France)
Publication Date:
OSTI Identifier:
22323136
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 59; Other Information: Copyright (c) 2014 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; ACTIVATION ENERGY; BENTONITE; CALCIUM SILICATES; CRISTOBALITE; DIFFERENTIAL THERMAL ANALYSIS; DISSOLUTION; ION EXCHANGE; MONTMORILLONITE; NUCLEAR MAGNETIC RESONANCE; REACTION KINETICS; SILICON 29; SIMULATION; THERMAL GRAVIMETRIC ANALYSIS; X-RAY DIFFRACTION