Numerical modelling of volume changes at early ages-Potential, pitfalls and challenges

Abstract

A B S T R A C T R I~ S U M I ~For quantification of early deformations of hardening cement-based systems a number of conceptual and numerical models have been proposed. In this contribution some aspects of these models will be discussed and evaluated with respect to the mechanisms that are considered to be responsible for volume and length changes at early ages. Emphasis will be on systems hydrating under sealed conditions. The fact that volume changes at early ages, and more in particular autogenous shrinkage, should be considered as the response of a continuously changing system is discussed. These changes concern at least the pore system and the state of moisture in the pore system. Numerical models should, therefore, be able to simulate the evolution of the pore system with progress of the hydration process explicitly. Parallel with the modelling of the evolution of the pore system, c.q. the microstructure, the state of stress and associated deformations should be considered. The potential of numerical simulation models to deal with this coupled problem is discussed. Pitfalls encountered when developing and validating numerical simulation models will be addressed and discussed. The potential of numerical models is illustrated with examples. Un grand nombre de modules conceptuels et num~riques ont gt~ proposes pour la quantification des d~formations pr~-coces relatives au durcissement de syst~mes ~ base cimentaire. Dans cette contribution quelques aspects de ces modules seront abord~s et ~valu~s au regard des m~canismes que l'on consid~re comme responsables des changements de volume et de dimension aux jeunes @,es. L'accent sera mis sur les syst~mes en cours d'hydratation clans des conditions ~tanches. L'article examine Ie fait que les changements de volume aux jeunes dges, et

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“…where g stands for surface tension, r stands for the radius of gel particles (Van Breugel, 2001). When the curing humidity is bigger than 42%, the capillary stress is a key factor.…”

Effect of natural rubber latex on the shrinkage behavior and porosity of geopolymer concrete

“…It is found that the disjoining pressure is nothing but the change in volume at relative humidity beyond 50%. 23 The characteristics of an intervening fluid can modify to potential energy interaction between two planar surfaces. Both surface force and corresponding shrinkage may be changed by the presence or absence of a shrinkagereducing admixture in capillary pore solution.…”

Numerical Simulation of the Autogenous Shrinkage of Hardening Portland Cement Paste

“…Three fundamental mechanisms were proposed: surface tension mechanism, capillary pressure mechanism, and disjoining pressure mechanism [4][5][6][7][8][9]. Based on these mechanisms, some numerical models [4,7,8] were established to predict autogenous shrinkage.…”