Investigation of microscopic creep and shrinkage deformations of cement paste assisted by digital image correlation technique

Abstract

New in-situ microscopic mechanical tests in Environmental SEM (ESEM) and climatic chamber (CC), assisted by Digital Image Correlation (DIC) technique, have been developed. The developed testing frameworks speed up the drying duration at least 200 times compared to classical test methods. We mitigate the risk of cracking to focus on the intrinsic drying creep and shrinkage. Free drying shrinkage is assessed at a micro-scale and exhibits a high correlation with the mass loss for relative humidity above 60% relative humidity (RH). We observe a water cavitation effect between 50–60% (RH). Although the drying conditions in ESEM occur at low pressure compared to ambient air-drying conditions in a climatic chamber, the shrinkage deformations at equilibrium at 20% RH are quite the same. The evolution of desiccation creep with drying shrinkage is bilinear in uniaxial and linear under biaxial compression. The drying creep Poisson’s ratio is negative, between −0.1 and 0.