Abstract
Long-term creep (i.e., deformation under sustained load) is a significant material response that needs to be accounted for in concrete structural design. However, the nature and origin of concrete creep remain poorly understood and controversial. Here, we propose that concrete creep at relative humidity ≥ 50%, but fixed moisture content (i.e., basic creep), arises from a dissolution-precipitation mechanism, active at nanoscale grain contacts, as has been extensively observed in a geological context, e.g., when rocks are exposed to sustained loads, in liquid-bearing environments. Based on micro-indentation and vertical scanning interferometry data and molecular dynamics simulations carried out on calcium-silicate-hydrate (C-S-H), the major binding phase in concrete, of different compositions, we show that creep rates are correlated with dissolution rates - an observation which suggests a dissolution-precipitation mechanism as being at the origin of concrete creep. C-S-H compositions featuring high resistance to dissolution, and, hence, creep are identified. Analyses of the atomic networks of such C-S-H compositions using topological constraint theory indicate that these compositions present limited relaxation modes on account of their optimally connected (i.e., constrained) atomic networks.
| Original language | English |
|---|---|
| Article number | 054701 |
| Journal | Journal of Chemical Physics |
| Volume | 145 |
| Issue number | 5 |
| DOIs | |
| State | Published - Aug 7 2016 |
Funding
support for this research provided by the U.S. Department of Transportation (U.S. DOT) through the Federal Highway Administration (Grant No. DTFH61-13-H-00011), the National Science Foundation (Grant No. 1562066 and CAREER Award No. 1235269), the Oak Ridge National Laboratory operated for the U.S. Department of Energy by UT-Battelle (LDRD Award No. 4000132990), and the University of California, Los Angeles (UCLA). Access to computational resources was provisioned by the Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), the Laboratory for the Chemistry of Construction Materials (LC2), and the Institute for Digital Research and Education (IDRE) at UCLA. This research was conducted in the Laboratory for the Chemistry of Construction Materials (LC2) and Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab) at UCLA. The authors gratefully acknowledge the support that has made these laboratories and their operations possible. The contents of this paper reflect the views and opinions of the authors, who are responsible for the accuracy of the datasets presented herein, and do not reflect the views and/or policies of the funding agencies nor do the contents constitute a specification, standard or regulation. This manuscript has been co-authored by the Oak Ridge National Laboratory, managed by UT-Battelle LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.