Numerical Study of the Relation Between Internal Swelling and Surface Degradation

Re-assessment of structures affected by internal swelling reactions (ISR) such as alkali-silica reaction (ASR) or delayed ettringite formation (DEF) often requires the use of numerical models to simulate concrete expansive behavior with more or less sophisticated constitutive equations. In the case of real structures, for which few information is available, applying these tools would imply expensive and time-consuming in-situ examination and laboratory analysis in order to achieve a direct identification of model parameters. However, these real structures are usually subjected to monitoring policy, which implies that a large number of reports of apparent disorders (cracks, deformation, etc.) are available. This communication takes place in a project aimed at developing numerical techniques to identify parameters of a model representing ISR-affected concrete based on information provided by the sole visual inspection of the structure surface. Due to its high complexity, this identification problem is first treated on simplified structural elements. This communication will focus on a series of numerical examples representing the prism of plain concrete and reinforced concrete, affected by ASR or DEF and submitted to various conditions of temperature (constant or varying with time), moisture (uniform, spatial heterogeneity, variation with time due to drying…) and stress (no stress, uni-axial stress, multi-axial stress). Then, numerical indicators representing surface degradation will be presented. Finally, the relationship between these indicators and the different parameters of the ISR-affected concrete model will be analyzed. This analysis is the first step to achieving a methodology for identifying these parameters.