Century-long durability of concrete structures

Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling

Zdenek P Bazant, Saeed Rahimi-Aghdam

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)

Abstract

Computations of long-time hygrothermal effects in concrete structures necessitate a physically based model for autogenous shrinkage and swelling of hardened portland cement paste. The present goal is to propose such a model. As known since 1887, the volume of cement hydration products is slightly smaller than the original volume of cement and water. However, this does not mean that the hydration reaction causes contraction of the cement paste and concrete. According to the authors’ recently proposed paradigm, the opposite is true for porous cement paste as a whole. The growth of C-S-H shells around anhydrous cement grains pushes the neighbors apart and thus causes volume expansion of the porous cement paste as a whole, while the nanoscale volume contraction of hydration products contributes to porosity. The growth of ettringite and portlandite crystals may also cause additional expansion. On the material scale, the expansion always dominates over the contraction, i.e., the hydration per se is, in the bulk, always expansive, while the source of all of the observed shrinkage, whether autogenous or due to external drying, is the compressive elastic or viscoelastic strain in the solid caused by a decrease of chemical potential of pore water, with the corresponding decrease in pore humidity, increase of solid surface tension and, mainly, decrease of disjoining pressure. The low density C-S-H and high density C-S-H are distinguished in the proposed model. The selfdesiccation, shrinkage and swelling can all be predicted from one and the same unified model, as confirmed by comparisons with with the existing experimental evidence. The model is ready for use in finite element programs.

Original languageEnglish (US)
Title of host publicationComputational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018
EditorsBernhard Pichler, Jan G. Rots, Günther Meschke
PublisherCRC Press/Balkema
Pages15-24
Number of pages10
ISBN (Print)9781138741171
DOIs
StatePublished - Jan 1 2018
EventConference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018 - Bad Hofgastein, Austria
Duration: Feb 26 2018Mar 1 2018

Publication series

NameComputational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018

Conference

ConferenceConference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018
CountryAustria
CityBad Hofgastein
Period2/26/183/1/18

Fingerprint

Hydration
Concrete Structures
Swelling
Durability
Shrinkage
Concrete construction
Mechanics
Cements
Contraction
Decrease
Water
Model
Drying
Humidity
Chemical Potential
Adhesive pastes
Porosity
Surface Tension
Chemical potential
Portland cement

ASJC Scopus subject areas

  • Modeling and Simulation
  • Civil and Structural Engineering

Cite this

Bazant, Z. P., & Rahimi-Aghdam, S. (2018). Century-long durability of concrete structures: Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling. In B. Pichler, J. G. Rots, & G. Meschke (Eds.), Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018 (pp. 15-24). (Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018). CRC Press/Balkema. https://doi.org/10.1201/9781315182964-2
Bazant, Zdenek P ; Rahimi-Aghdam, Saeed. / Century-long durability of concrete structures : Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling. Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018. editor / Bernhard Pichler ; Jan G. Rots ; Günther Meschke. CRC Press/Balkema, 2018. pp. 15-24 (Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018).
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title = "Century-long durability of concrete structures: Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling",
abstract = "Computations of long-time hygrothermal effects in concrete structures necessitate a physically based model for autogenous shrinkage and swelling of hardened portland cement paste. The present goal is to propose such a model. As known since 1887, the volume of cement hydration products is slightly smaller than the original volume of cement and water. However, this does not mean that the hydration reaction causes contraction of the cement paste and concrete. According to the authors’ recently proposed paradigm, the opposite is true for porous cement paste as a whole. The growth of C-S-H shells around anhydrous cement grains pushes the neighbors apart and thus causes volume expansion of the porous cement paste as a whole, while the nanoscale volume contraction of hydration products contributes to porosity. The growth of ettringite and portlandite crystals may also cause additional expansion. On the material scale, the expansion always dominates over the contraction, i.e., the hydration per se is, in the bulk, always expansive, while the source of all of the observed shrinkage, whether autogenous or due to external drying, is the compressive elastic or viscoelastic strain in the solid caused by a decrease of chemical potential of pore water, with the corresponding decrease in pore humidity, increase of solid surface tension and, mainly, decrease of disjoining pressure. The low density C-S-H and high density C-S-H are distinguished in the proposed model. The selfdesiccation, shrinkage and swelling can all be predicted from one and the same unified model, as confirmed by comparisons with with the existing experimental evidence. The model is ready for use in finite element programs.",
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Bazant, ZP & Rahimi-Aghdam, S 2018, Century-long durability of concrete structures: Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling. in B Pichler, JG Rots & G Meschke (eds), Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018. Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018, CRC Press/Balkema, pp. 15-24, Conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018, Bad Hofgastein, Austria, 2/26/18. https://doi.org/10.1201/9781315182964-2

Century-long durability of concrete structures : Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling. / Bazant, Zdenek P; Rahimi-Aghdam, Saeed.

Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018. ed. / Bernhard Pichler; Jan G. Rots; Günther Meschke. CRC Press/Balkema, 2018. p. 15-24 (Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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Bazant ZP, Rahimi-Aghdam S. Century-long durability of concrete structures: Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling. In Pichler B, Rots JG, Meschke G, editors, Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018. CRC Press/Balkema. 2018. p. 15-24. (Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018). https://doi.org/10.1201/9781315182964-2