Analysis of interactions between damage and basic creep of HPC and HPFRC heated between 20 and 80 A degrees C
Résumé
The present study concerns the uniaxial compressive creep of High Performance Concrete (HPC) at moderate temperatures, 20-80 A degrees C. The study was conducted on four formulations of HPC including two fibrous concretes envisioned for future storage structures of Intermediate Level Long-Life Nuclear Wastes. These wastes are exothermic and lead to maximal temperatures in the field ranging from 50 to 70 A degrees C (Andra, R,f,rentiel des mat,riaux de stockage de d,chets A haute activit, et A vie longue, 2005). Here, we investigate the basic creep under uniaxial compression at 50 and 80 A degrees C and compare it to that obtained on the same HPC at 20 A degrees C. The objective of this research is to contribute to a better understanding of the phenomenon of interaction between damage and basic creep of HPC at moderate temperature, especially with a view to its integration in Thermo-Hydro-Mechanical models dealing with the design of special structures (massive structures, specific serviceability conditions in nuclear or hydroelectric power plants, etc.). This test campaign allowed us to assess the effect of temperature on the magnitude of basic creep of HPC, and also the impact of various temperature and mechanical loading conditions on the Young's modulus of HPC. Heating to 80 A degrees C damages HPC (instantaneous Young's modulus decrease) and thereby increases the creep capacity, showing a relation between damage and creep amplitude. Moreover, this study gives global activation energy of basic creep of HPC that should be useful for practitioners dealing with concrete structures sensitive to delayed strains and subjected to moderate temperature.