title: A dissolution-precipitation mechanism is at the origin of concrete creep in moist environments.
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.
authors: Laboratory for the Chemistry of Construction Materials (LC), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA.
authors: Isabella
authors: I
authors: Pignatelli
authors: Materials Science and Engineering Department, Missouri University of Science and Technology, Rolla, Missouri 65409, USA.
authors: Aditya
authors: A
authors: Kumar
authors: Giatec Scientific, Ottawa, Ontario K2H 9C4, Canada.
authors: Rouhollah
authors: R
authors: Alizadeh
authors: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Yann
authors: Y
authors: Le Pape
authors: Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA.
authors: Mathieu
authors: M
authors: Bauchy
authors: Laboratory for the Chemistry of Construction Materials (LC), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA.
authors: Gaurav
authors: G
authors: Sant