Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 8, Issue 51, Pages 35621-35627Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.6b11587
Keywords
silicates; thermal expansion; atomistic simulation; topology; confinement
Funding
- Infravation ERA-NET Plus Grant [31109806.0001]
- U.S. Department of Transportation via the Federal Highway Administration [DTFH61-13-H-00011]
- U.S. National Science Foundation [1253269, CMMI 1562066]
- California Energy Commission [PIR 12-032]
- Oak Ridge National Laboratory in the form of Laboratory Directed Research and Development (LDRD) support
- U.S. Department of Energy [DE-AC05-00OR22725]
- Directorate For Engineering
- Div Of Civil, Mechanical, & Manufact Inn [1562066] Funding Source: National Science Foundation
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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 examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in 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.
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