Time-Space-Resolved Chemical Deconvolution of Cementitious Colloidal Systems Using Raman Spectroscopy

Area of Science:

• Materials Science
• Chemistry
• Civil Engineering

Background:

• Concrete is a vital construction material, with early workability being a key property.
• Understanding cement hydration is crucial for optimizing concrete performance and durability.

Purpose of the Study:

• To investigate the early hydration kinetics of ordinary Portland cement (OPC) using advanced in situ techniques.
• To visualize the spatial and temporal evolution of hydration products at the submicron level.
• To elucidate the role of calcium hydroxide formation in the cement setting process.

Main Methods:

• In situ underwater Raman microspectroscopy for high-resolution imaging.
• Analysis of spectral features in the hydroxyl stretching region.
• Application of two-point correlation functions to study phase relationships.

Main Results:

• Confirmed coexistence of Ca-OH and Si-OH bonds in disordered C-S-H gel.
• Experimentally identified disordered calcium hydroxide (Ca(OH)₂) in the mixture before setting.
• Spatially and temporally resolved phase transformations of clinker, C-S-H, and Ca(OH)₂.
• Quantitatively validated that cement setting is a percolation process.

Conclusions:

• Calcium hydroxide crystallization is essential for cement paste setting.
• Hydration products form an interconnected network, signifying the percolation process of setting.
• The developed characterization method offers valuable insights into cementitious colloidal systems for materials design.