Deformation mechanism of hardened cement paste under high stress and application of flow law

Abstract

In this study, a creep test was performed on hardened cement paste (HCP) with stepwise load increase at different confining pressures and saturation degrees. The strain rate-stress relationship, obtained under a stress of >75% of the maximum strength and plotted on a log-log chart, showed a slope of six. From previous studies on crystalline materials, such as rock, metal, and ice, it can be inferred that this slope indicates a deformation governed by dislocation creep. If dislocation creep occurs in HCP, the deformation may be governed by crystalline hydrates other than calcium silicate hydrate (C-S-H) because dislocation creep is generally not defined for gel materials. Further study and careful discussion are required because a slope of six is a necessary condition for the dislocation creep. The activation volume was evaluated, and the flow law was applied to calculate the strain rate of HCP. The obtained activation volume gives a better fit for the measured results than the previously reported values.