r7.01.12 Modeling thermohydration, drying and shrinkage of concrete

Summary

Two types of phenomena occurring at distinct periods in the life of concrete are described here:

• on the one hand, a thermo-hydration reaction causing a so-called endogenous shrinkage, which occurs at a young age of concrete (the first 100 days),

• on the other hand an evaporation of some of the water not used in the hydration process, a phenomenon called drying and resulting in a shrinkage of desiccation. Depending on the dimensions of the concrete structure used, this phenomenon can last from a few months to several years.

These phenomena are modelled in Code_Aster in the form of diffusion equations whose solution is represented by new variables making it possible to directly calculate the deformations of endogenous shrinkage (due to hydration) and of desiccation shrinkage (due to drying).

Table of Contents

• 1. Introduction
  • 1.1. Phenomenological aspects of the behavior of concrete at a young age: thermohydration
  • 1.2. Drying and desiccation removal
• 2. Formalization of thermo-hydration
  • 2.1. Thermohydration equation
  • 2.2. Exploitation of the adiabatic test for the determination of the affinity function and the heat of hydration.
• 3. Discretization of the thermo-hydration problem
  • 3.1. Choosing the resolution method
  • 3.2. Resolution algorithm
• 4. Formalization of drying
  • 4.1. Drying modeling and equations
  • 4.2. Diffusion coefficient
  • 4.3. Common distribution laws
  • 4.4. Modeling boundary conditions
• 5. Integrating drying into Code_Aster
  • 5.1. Introduction of the concept of behavior in the nonlinear thermal operator
  • 5.2. Implementation of boundary conditions for drying
  • 5.3. Digital integration of drying
• 6. Formalization of endogenous withdrawal and desiccation
  • 6.1. Withdrawal in Code_Aster
  • 6.2. Integration of shrinkage into mechanical laws of behavior
  • 6.3. Tangent matrix
• 7. Bibliography
• 8. Description of document versions