DOI QR코드

DOI QR Code

A Numerical Model for the Freeze-Thaw Damages in Concrete Structures

  • Cho Tae-Jun (Dept. of Civil & Env. Eng., Cheongju University)
  • 발행 : 2005.10.01

초록

This paper deals with the accumulated damage in concrete structures due to the cyclic freeze-thaw as an environmental load. The cyclic ice body nucleation and growth processes in porous systems are affected by the thermo-physical and mass transport properties, and gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and diffusion of chloride ion effects are hard to be identified in tests, and there has been no analytic model for the combined degradations. The main objective is to determine the driving force and evaluate the reduced strength and stiffness by freeze-thaw. For the development of computational model of those coupled deterioration, micro-pore structure characterization, pore pressure based on the thermodynamic equilibrium, time and temperature dependent super-cooling with or without deicing salts, nonlinear-fracture constitutive relation for the evaluation of internal damage, and the effect of entrained air pores (EA) has been modeled numerically. As a result, the amount of ice volume with temperature dependent surface tensions, freezing pressure and resulting deformations, and cycle and temperature dependent pore volume has been calculated and compared with available test results. The developed computational program can be combined with DuCOM, which can calculate the early aged strength, heat of hydration, micro-pore volume, shrinkage, transportation of free water in concrete. Therefore, the developed model can be applied to evaluate those various practical degradation cases as well.

키워드

참고문헌

  1. Setzer M., Modeling and testing the freeze-thaw attack by micro-ice-lens model and CDF/CIF test, Micro-structure and durability to predict service life of concrete structures, 2004, pp.17-27
  2. Maekawa K., Kishi T., 'Multi-Component Model for Hydration Heating of Portland Cement', JSCE, Vol.29, No.526, 1995, pp.98-112
  3. Zhu Y.B., Multi-scale constitutive model of concrete based on thermodynamic states of moisture in micro, Thesis of the University of Tokyo, 2004, pp.36-41
  4. Mihashi H., Z. Y. Zhou, Micro mechanics model to predict macroscopic behavior of concrete under frost action, RILEM proceedings PRO24, 1997, pp.235-241
  5. Hobbs, J.P., C.S.P. Sung, K. Krishnann, and S. Hill, 'Characterization of surface structure and orientation in polypropyl-ene and poly(ethylene terephthalate) films by modified attenu-ated total reflection IR dichromism studies,' Macromolecules, 16, 1983, pp.193-199 https://doi.org/10.1021/ma00236a008
  6. Hesstvedt, E., The Interfacial Energy Ice/Water, Norges Geotekniska Institutt, Publikasjon nr. 56, Oslo, 1964, pp.823-833
  7. Wolfe J.and Bryant G., 'Cellular cryobiology: thermodynamic and mechanical effects', International Journal of Refrigeration, Vol.24, Issue5, 2001, pp.438-450 https://doi.org/10.1016/S0140-7007(00)00027-X
  8. Maekawa K., Pimammas A., and Okamura H., Nonlinear Me-chanics of Reinforced Concrete, Spoon Press, 2002, pp.431-564
  9. Ueda T., M. Hasan, K. Nagai, and Y. Sato, Prediction of structural performance during service life from microstructure, Microstructure and durability to predict service life of concrete structures, 2004, pp.39-50
  10. Kim J. Lee Y., Yi S., 'Fracture characteristics of concrete at early ages', Cement and Concrete Research, Vol.34, 2004, pp.39-50, 507-519
  11. Powers, T.C, Freezing Effects in Concrete, in Durability of Concrete, ACI SP-47, 1975, pp.1-11
  12. Bentz, D.P., Garboczi, E.J., and Stutzman, P.E., 'Computer Modelling of the Interfacial Zone in Concrete', In Interfaces in Cementitious Composites, Ed. J.C. Maso, 18, 1992, pp. 39-50, 107-116
  13. Setzer M., 'Micro-Ice-Lens Formation in Porous Solid', Journal of Colloid and Interface Science, 243, 2001, pp.39-50, 193-201