TY - JOUR
T1 - Confined Water in Layered Silicates
T2 - The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates
AU - Krishnan, N. M Anoop
AU - Wang, Bu
AU - Falzone, Gabriel
AU - Le Pape, Yann
AU - Neithalath, Narayanan
AU - Pilon, Laurent
AU - Bauchy, Mathieu
AU - Sant, Gaurav
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/12/28
Y1 - 2016/12/28
N2 - Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H’s nanostructure. We identify that confinement is dictated by the topology of the C-S-H’s atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.
AB - Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H’s nanostructure. We identify that confinement is dictated by the topology of the C-S-H’s atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.
KW - atomistic simulation
KW - confinement
KW - silicates
KW - thermal expansion
KW - topology
UR - http://www.scopus.com/inward/record.url?scp=85008195240&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85008195240&partnerID=8YFLogxK
U2 - 10.1021/acsami.6b11587
DO - 10.1021/acsami.6b11587
M3 - Article
AN - SCOPUS:85008195240
SN - 1944-8244
VL - 8
SP - 35621
EP - 35627
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 51
ER -