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Capillary pressure and cracking in early age concrete



Title: Capillary pressure and cracking in early age concrete
Author(s): V. Slowik, T. Hübner, B. Villmann, M. Schmidt
Paper category : conference
Book title: International RILEM Symposium on Concrete Modelling - ConMod '08
Editor(s): E. Schlangen and G. De Schutter
Print-ISBN: 978-2-35158-060-8
e-ISBN: 978-2-35158-076-9
Publisher: RILEM Publications SARL
Publication year: 2008
Pages: 673 - 680
Total Pages: 8
Nb references: 9
Language: English


Abstract: Shrinkage and cracking of concrete in the early age, i.e. within the first few hours after casting, is mainly caused by the capillary pressure build-up in the two-phase system consisting of solid particles and water. Due to evaporation at the concrete surface, the water content in the system decreases and, eventually, the solid particles can not be covered by a continuous and plane water film anymore. As the curvature of the water surface between the superficial particles increases, a negative capillary pressure is built up in the liquid phase resulting in shrinkage.
The presented 2D model allows to simulate the described physical process and to investigate influences of the material composition on the capillary pressure and on the early age cracking risk. Circular rigid particles are uniformly distributed in a liquid phase and the water front between the particles is calculated by assuming constant surface curvature.
Evaporation leads to an increase of this curvature and simultaneously to an increase of the capillary pressure. Particle mobility is controlled by interparticular forces. It is demonstrated that under increasing capillary pressure air penetrates locally into the system. This may lead to discontinuities in the displacement field and to the formation of cracks.


Online publication: 2009-06-15
Publication type : full_text
Public price (Euros): 0.00