Materials and Structures

, Volume 48, Issue 3, pp 517–529 | Cite as

Role of carbonates in the chemical evolution of sodium carbonate-activated slag binders

  • Susan A. Bernal
  • John L. Provis
  • Rupert J. Myers
  • Rackel San Nicolas
  • Jannie S. J. van Deventer
Original Article


Multi-technique characterisation of sodium carbonate-activated blast furnace slag binders was conducted in order to determine the influence of the carbonate groups on the structural and chemical evolution of these materials. At early age (<4 days) there is a preferential reaction of Ca2+ with the CO3 2− from the activator, forming calcium carbonates and gaylussite, while the aluminosilicate component of the slag reacts separately with the sodium from the activator to form zeolite NaA. These phases do not give the high degree of cohesion necessary for development of high early mechanical strength, and the reaction is relatively gradual due to the slow dissolution of the slag under the moderate pH conditions introduced by the Na2CO3 as activator. Once the CO3 2− is exhausted, the activation reaction proceeds in similar way to an NaOH-activated slag binder, forming the typical binder phases calcium aluminium silicate hydrate and hydrotalcite, along with Ca-heulandite as a further (Ca,Al)-rich product. This is consistent with the significant gain in compressive strength and reduced porosity observed after 3 days of curing. The high mechanical strength and reduced permeability developed in these materials beyond 4 days of curing elucidate that Na2CO3-activated slag can develop desirable properties for use as a building material, although the slow early strength development is likely to be an issue in some applications. These results suggest that the inclusion of additions which could control the preferential consumption of Ca2+ by the CO3 2− might accelerate the reaction kinetics of Na2CO3-activated slag at early times of curing, enhancing the use of these materials in engineering applications.


Alkali-activated slag Sodium carbonate X-ray diffraction Nuclear magnetic resonance X-ray microtomography 



This work has been funded by the Australian Research Council, through a Linkage Project cosponsored by Zeobond Pty Ltd, including partial funding through the Particulate Fluids Processing Centre. We wish to thank Adam Kilcullen and David Brice for preparation of pastes specimens, John Gehman for his assistance in NMR data collection and Volker Rose and Xianghui Xiao for assistance in the data collection and processing on the 2BM instrument. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357. The work of JLP and SAB received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement #335928 (GeopolyConc), and from the University of Sheffield.


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Copyright information

© RILEM 2014

Authors and Affiliations

  • Susan A. Bernal
    • 1
  • John L. Provis
    • 1
  • Rupert J. Myers
    • 1
  • Rackel San Nicolas
    • 2
  • Jannie S. J. van Deventer
    • 2
    • 3
  1. 1.Department of Materials Science and EngineeringThe University of SheffieldSheffieldUK
  2. 2.Department of Chemical & Biomolecular EngineeringThe University of MelbourneParkvilleAustralia
  3. 3.Zeobond Pty LtdDocklandsAustralia

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