Order and disorder in calcium-silicate-hydrate.

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• The atomic-scale structure of Calcium-Silicate-Hydrate (C-S-H), the primary binding phase in cement, is not fully understood.
• Recent molecular models propose an amorphous nanoscale structure for C-S-H, challenging previous crystalline models.

Purpose of the Study:

• To investigate the atomic order within a realistic simulated model of C-S-H.
• To compare the structure of C-S-H with crystalline tobermorite and an artificial glass.

Main Methods:

• Analysis of a realistic simulated model of C-S-H.
• Comparison with crystalline tobermorite and an artificial ideal glass.
• Detailed quantification of atomic order and disorder.

Main Results:

• Averaged over all atoms, C-S-H exhibits an amorphous structure.
• Analysis of local atomic environments reveals an intermediate degree of order.
• C-S-H retains some structural signatures of tobermorite, while hydrated species are fully amorphous.

Conclusions:

• The nanoscale structure of C-S-H is neither purely crystalline nor fully amorphous, but possesses a hybrid order.
• Understanding this intermediate order is crucial for advancing cement hydration modeling and material design.