Coupling statistical indentation and microscopy to evaluate micromechanical properties of materials: Application to viscoelastic behavior of irradiated mortars

In this work, an original method coupling statistical indentation and 3D microscope image analysis for heterogenous materials characterization is developed. Statistical microindentation test results performed on γ-irradiated and pristine mortar specimens are presented and analyzed using a clustering data mining technique. The outputs are compared with the phase identification from 3D image analysis to effectively reduce uncertainties in the material properties of one of the phases (cement paste). With respect to the effects of irradiations on cementitious materials, a significant increase of cement paste creep modulus and hardness, and a significant decrease of creep characteristic time, are highlighted after an exposition of 257 kGy at 8.5 Gy/min. Young's modulus of the cement paste is not significantly affected. These results confirm macroscopic concrete creep observations presented in previous studies fitted with dose-dependent logarithmic laws.