Hydration of Concrete: The First Steps.

Area of Science:

• Materials Science
• Surface Chemistry
• Mineralogy

Background:

• Concrete is a crucial construction material, yet its porous nature leads to infrastructure corrosion.
• Understanding the surface chemistry of concrete, particularly its reaction with water, is essential for corrosion prevention.

Purpose of the Study:

• To investigate proton transfer reactions on calcium-silicate (CS) surfaces upon exposure to water.
• To elucidate the role of surface chemistry in concrete formation and corrosion processes.
• To compare the reactivity of CS surfaces with water and methanol.

Main Methods:

• Employed a Surface Science approach using a well-defined mineral, Wollastonite (a calcium-silicate).
• Utilized Infrared (IR) spectroscopy to analyze surface species after exposure to H2O.
• Performed first-principles computational studies using density functional theory (DFT) to aid data interpretation.

Main Results:

• IR spectroscopy showed H2O exposure leads to dissociation and formation of OH-species on the CS substrate.
• Proton transfer was observed with water but not with methanol, indicating specific surface interactions.
• Combined experimental and theoretical data provided a consistent model for proton transfer in CS and calcium-silicate-hydrate (CSH) phases.

Conclusions:

• Proton transfer is a critical reaction governing both cement hydration (concrete formation) and concrete corrosion.
• The distinct reactivity with water versus methanol highlights the importance of specific surface interactions.
• Findings offer insights for developing strategies to protect concrete infrastructure from aqueous corrosion.