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Title: Multi-Decade, Multi-Scale Modeling of Aging Basic Creep of Concrete

Author(s): Brock D. Hedegaard

Publication: Materials Journal

Volume: 117

Issue: 6

Appears on pages(s): 17-27

Keywords: creep; dissolution precipitation; hydration; multi-scale modeling

Date: 11/1/2020

Abstract:
This study presents a multi-scale model for predicting multidecade basic creep of concrete. Aging of cement is modeled through hydration, densification, and polymerization of the calcium- silicate-hydrate (C-S-H) phases. The model accounts for the separate mechanisms of viscoelastic compliance and aging viscous flow of the C-S-H, and for the dissolution-precipitation of elastic and viscoelastic phases during hydration that causes apparent creep in the composite. Upscaling is performed in the time-domain simultaneously for all loading ages. The results show that short-term viscoelastic compliance observed from nanoindentation tests dominates short-term creep, but cannot explain long-term creep rates observed in macroscopic concrete creep tests. Such observations can only be replicated by considering viscous flow that develops over time scales unobservable by minutes-long tests on the microscale. Dissolution creep may explain some irreversible basic creep at very early ages but rapidly diminishes in relevance as the concrete continues to age.


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