### 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 language | English (US) |
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Title of host publication | Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018 |

Editors | Bernhard Pichler, Jan G. Rots, Günther Meschke |

Publisher | CRC Press/Balkema |

Pages | 15-24 |

Number of pages | 10 |

ISBN (Print) | 9781138741171 |

DOIs | |

State | Published - Jan 1 2018 |

Event | Conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018 - Bad Hofgastein, Austria Duration: Feb 26 2018 → Mar 1 2018 |

### Publication series

Name | Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete&amp;amp;amp;amp;amp;amp;amp;nbsp;and Concrete Structures, EURO-C 2018 |
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### Conference

Conference | Conference on Computational Modelling of Concrete and Concrete Structures, EURO-C 2018 |
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Country | Austria |

City | Bad Hofgastein |

Period | 2/26/18 → 3/1/18 |

### Fingerprint

### ASJC Scopus subject areas

- Modeling and Simulation
- Civil and Structural Engineering

### Cite this

*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&amp;amp;amp;amp;amp;amp;amp;nbsp;and Concrete Structures, EURO-C 2018). CRC Press/Balkema. https://doi.org/10.1201/9781315182964-2

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*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&amp;amp;amp;amp;amp;amp;amp;nbsp;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.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

TY - GEN

T1 - Century-long durability of concrete structures

T2 - Expansiveness of hydration and chemo-mechanics of autogenous shrinkage and swelling

AU - Bazant, Zdenek P

AU - Rahimi-Aghdam, Saeed

PY - 2018/1/1

Y1 - 2018/1/1

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85061175602&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85061175602&partnerID=8YFLogxK

U2 - 10.1201/9781315182964-2

DO - 10.1201/9781315182964-2

M3 - Conference contribution

SN - 9781138741171

T3 - Computational Modelling of Concrete Structures - Proceedings of the conference on Computational Modelling of Concrete&amp;amp;amp;amp;amp;amp;amp;amp;nbsp;and Concrete Structures, EURO-C 2018

SP - 15

EP - 24

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

A2 - Pichler, Bernhard

A2 - Rots, Jan G.

A2 - Meschke, Günther

PB - CRC Press/Balkema

ER -