Modelagem dos fenômenos de transporte termo-hídricos em meios porosos submetidos a temperaturas elevadas: aplicação a uma bicamada rocha-concreto

Abstract

Concrete is an extremely complex material, whose properties are not yet fully understood. The difficulties in describing and predicting the behavior of concrete structures are due to aspects related to the heterogeneity of medium - which is porous and multiphase - presenting fluids in liquid and gas forms. When exposed to high temperature conditions, such difficulties are even increased because of the occurrence of physical and chemical phenomena, which alters the porous structure and properties of the material. As the cement hydration reaction is reversible and thermo-activated, exposure of concrete to elevated temperatures causes deleterious effects, such as dehydration of the cement-based matrix, cracking due to internal pressures generated by evaporation of free water and spalling. This work aims the study of the hygro-thermal behavior of structures composed of bilayers rock-concrete - commonly found in tunnels and underground repositories. It was developed an experimental program consisting of thermal analysis in which bilayer samples made of two types of concrete - conventional and high performance - were submitted to temperatures up to 750ºC. These tests provided data for the implementation of a hygrothermal model on the Cast3m code - which was used to simulate the same experiments developed in the laboratory. The numerical results allowed the evaluation of the quality of the proposed model, and serve as a basis for future developments that take into account the thermo-hydro-mechanical coupling to describe the material behavior.