Microcrack and Porosity Development in Sealed Cement Mortars Measured with Micro-Computed Tomography

Area of Science:

• Materials Science
• Civil Engineering
• Chemical Engineering

Background:

• Microcrack development is a critical factor in concrete durability.
• Understanding the influence of binder properties on microcracking is essential for advanced material design.

Purpose of the Study:

• To investigate the impact of hydration kinetics on microcrack formation in cementitious materials.
• To compare microcrack development in ordinary Portland cement (OPC) with varying fineness and an alkali-activated binder (H-cement).

Main Methods:

• Utilized micro-computed tomography (μ-CT) with 2.2 µm resolution to analyze microcrack development.
• Examined three binder types: fine-grained OPC (391 m²/kg), coarse-grained OPC (273 m²/kg), and H-cement.
• Monitored microcrack width and occurrence during sealed hydration.

Main Results:

• Most observed microcracks ranged from 5-10 µm in width.
• Microcrack occurrence increased with the progression of sealed hydration.
• Fine-grained OPC showed over twice the number of microcracks compared to H-cement and coarse-grained OPC, which had comparable counts.

Conclusions:

• Higher hydration kinetics correlate with increased microcrack formation.
• Rapid microcracking can lead to crack coalescence and eventual concrete disintegration.
• Achieving durable concrete requires utilizing slow hydration kinetics or alkali-activation strategies to minimize microcracks.