| A Non-equilibrium Approach to Modeling Chemical Deterioration Processes in Concrete Structures Exposed to Variable Hygrothermal Conditions Dariusz Gawin1; Francesco Pesavento2; Marcin Koniorczyk1; 1LODZ UNIVERSITY OF TECHNOLOGY, Lodz, Poland; 2UNIVERSITY OF PADOVA, Padova, Italy; PAPER: 223/Geomechanics/Keynote (Oral) SCHEDULED: 16:20/Fri. 25 Oct. 2019/Athena (105/Mezz. F) ABSTRACT: Concrete structures are widely used in civil, environmental, and nuclear engineering. During their lifetime, the structures are often exposed to severe environmental conditions, causing various deterioration processes, which might significantly reduce their durability. The aim of this contribution is to present a general approach [1] to modelling various chemical deterioration processes in concrete, due to combined action of variable hygro-thermal, chemical and mechanical loads. For this purpose, mechanics of multiphase porous media and delayed damage theory are applied. The mass, energy, and momentum balances, as well as the evolution equations describing the progress of chemical reactions and the constitutive and physical relations are briefly summarized. The kinetics of physicochemical deterioration processes like calcium leaching [2], Alkali Silica Reaction (ASR) [3], and salt crystallization-dissolution [4, 5], are described by means of evolution equations based on linear thermodynamics of chemical reactions. The mutual couplings between the chemical, hygral, thermal and mechanical processes are presented and discussed, both from the viewpoint of physicochemical mechanisms and mathematical modelling. Numerical methods used for solution of the model governing equations are presented. For this purpose, the finite element method is applied for space discretization and the finite difference method for integration in the time domain. Some examples of the model application for analysis of transient chemo-hygro-thermo-mechanical processes in porous construction materials are presented and discussed. The first example deals with calcium leaching from a concrete wall due to chemical attack of pure water exposed to gradients of temperature and pressure. The second one describes cracking of a concrete element, caused by development of expanding products of ASR. The third example concerns salt crystallization during the drying of a wall made of concrete and ceramic brick, causing degradation of the surface layer due to development of crystallization pressure. References: [1] D. Gawin, M. Koniorczyk and F. Pesavento, Modelling of hydro-thermo-chemo-mechanical phenomena in building materials, Bulletin of The Polish Academy of Sciences: Technical Sciences 61(1) (2013) 51-63. [2] D. Gawin, F. Pesavento and B.A. Schrefler, Modeling deterioration of cementitious materials exposed to calcium leaching in non-isothermal conditions, Computer Methods in Applied Mechanics and Engineering 198 (37-40) (2009) 3051-3083. [3] F. Pesavento, D. Gawin, M. Wyrzykowski, B.A. Schrefler, L. Simoni, Modeling alkali-silica reaction in non-isothermal, partially saturated cement based materials, Computer Methods in Applied Mechanics and Engineering 225-228 (2012) 95-115. [4] M. Koniorczyk, D. Gawin, Modelling of salt crystallization in building materials with micro-structure - poromechanical approach, Construction and Building Materials 36 (2012) 860-873. [5] M. Koniorczyk, D. Gawin, B.A. Schrefler, Multiphysics model for spalling prediction of brick due to in-pore salt crystallization, Computers and Structures 196 (2018) 233-245. |
