Investigation of the creep properties of blended cement pastes using combined nanoindentation and SEM imaging
Résumé
The mechanisms underlying creep in cementitious materials have been extensively studied, with pioneering contributions shedding light on its origins. However, the amplitude and precise causes of creep remain less understood, particularly in modern mixes incorporating significant proportions of supplementary cementitious materials (SCMs). Nanoindentation offers a rapid and reliable method for investigating creep at the microscale, enabling the evaluation of individual cementitious phases under small loads over short durations. In this study, the creep of five cement pastes incorporating ground-granulated blast furnace slag (GGBFS) and calcined clay was studied. In our study, the creep of five cement pastes incorporation ground-granulated blast furnace slag (GGBFS) and calcined clay was studied. The mechanisms of the observed creep on the pastes scale were discussed in the light of nanoindentation results. Gaussian mixture model (GMM) and scanning electron microscopy (SEM) imaging (GMM-SEM) were combined to assess the micromechanical properties and the volume fractions of the individual phases in these binders. Results shows that GGBFS incorporation results in the formation of low density C-S-H, but the creep of the overall paste is balanced by the high amount of unhydrated particles (of cement and GGBFS) compared to the other blended pastes. In addition, the joint incorporation of GGBFS and calcined clay enables the formation of high density C-S-H more resistant to creep. Finally, the results of GMM-SEM were supplied to a recent analytical homogenization scheme and creep of the different pastes was accurately predicted compared to microindentation measurements. The results of this study may be used to design blended concretes with high resistance to creep and facilitate micromechanical properties evaluation.