Creep Mechanisms of Calcium–Silicate–Hydrate: An Overview of Recent Advances and Challenges

Abstract

A critical review on existing creep theories in calcium-silicate-hydrate (C-S-H) is presented with an emphasis on several fundamental questions (e.g. the roles of water, relative humidity, temperature, atomic ordering of C-S-H). A consensus on the rearrangement of nanostructures of C-S-H as a main consequence of creep, has almost been achieved. However, main disagreement still exists on two basic aspects regarding creep mechanisms: (1) at which site the creep occurs, like at interlayer, intergranular, or regions where C-S-H has a relatively higher solubility; (2) how the structural rearrangement evolutes, like in a manner of interlayer sliding, intra-transfer of water at various scales, recrystallization of gelled-like particles, or dissolutiondiffusion-reprecipitation at inter-particle boundary. The further understanding of creep behavior of C-S-H relies heavily on the appropriate characterization of its nanostructure.

A Review and Comparative Study of Existing Shrinkage Prediction Models for Portland and Non-Portland Cementitious Materials

“…Also, according to the experimental results (see Figure 1(a)) showing that the moisture loss of AAS is larger than that of OPC, the withdrawn disjoining pressure is, correspondingly, larger than that of OPC. On the other hand, the release of disjoining pressure in hindered adsorption region shows notably time-dependent properties (associated with internal water movement and redistribution [87]), which agrees with timedependent shrinkage behavior of AAS (see Figure 1(b)). However, this speculation needs further investigation.…”

Effect of Alkalis on Cementitious Materials:Understanding the Relationship between Composition, Structure, and Volume Change Mechanism

“…The creep deformation can be sub-divided into reversible (short-term) and irreversible (long-term) components. The reversible component is typically related to the micro-diffusion of water between capillary pores, while the irreversible component is attributed to the rearrangement and redistribution of C-S-H (Ye 2015). Therefore, the delayed accumulation of creep in AAS is likely to indicate that more proportion of creep deformation in AAS is irreversible.…”

“…However, it should be noted that the nature and magnitude of stresses in C-S-H nanostructure would be different for the same system under drying and loading (Ye 2015).…”

Nanoscale origins of creep in calcium silicate hydrates

“…Although dislocation 1 and shear transformation zones 2 , 3 are at the heart of creep in crystalline materials and metallic glasses, the nanoscale mechanisms underlying time-dependent deformation in cementitious materials are complex and still the subject of intensive fundamental research 4 – 7 . For calcium-silicate-hydrates (C-S-H), the main binding phase in cementitious materials, this complexity can in parts be attributed to the presence of nanoconfined water, the material’s layered structure at the nanoscale 8 – 10 , its globular texture at the mesoscale 11 and its multiscale porous structure 12 , 13 . These complexities further hinder the inherent difficulty in studying nanoscale longtime phenomena that arise from 18 orders of magnitude difference between characteristic time scales in atomic vibrations and creep deformation.…”