Elucidation of the Mechanism of Portlandite Depletion Due to Reaction With Aggregates：a Case Study of Concrete Subjected to Long-Term Heat Exposure

Key Points

• This study aims to identify the mechanism behind the depletion of portlandite in concrete exposed to high heat.
• Sample extraction from concrete core collected from a cement facility rotary kiln base.
• Polarized light microscopy and electron microscopy were used for detailed analysis.
• Comparison of structural surface and deeper layer samples to assess portlandite presence.
• Portlandite was not detected in deeper structural samples due to reactions with aggregates.
• Formation of a reaction zone primarily composed of tobermorite was identified at aggregate quartz and chert particle edges.
• The reaction was attributed to moisture in concrete micro-voids facilitating interaction between quartz and portlandite.