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Microcrack Detection in High-Performance Cementitious Materials

Microcrack Detection in High-Performance Cementitious Materials. Pietro Lura, Ye Guang, Kyoji Tanaka, and Ole Mejlhede Jensen. Early-age cracking. Tokyo Institute of Technology, Yokohama, Japan. Microcracking. (Bisschop & van Mier 2002). Chemical shrinkage. Autogenous shrinkage.

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Microcrack Detection in High-Performance Cementitious Materials

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  1. Microcrack Detectionin High-Performance Cementitious Materials Pietro Lura, Ye Guang, Kyoji Tanaka, and Ole Mejlhede Jensen

  2. Early-age cracking Tokyo Institute of Technology, Yokohama, Japan

  3. Microcracking (Bisschop & van Mier 2002)

  4. Chemical shrinkage Autogenous shrinkage Definitions (Jensen & Hansen 2001) solid water air

  5. Autogenous shrinkage in HPC • Less water • More cement • Silica fume

  6. Internal microcracking • Does autogenous shrinkage lead to internal cracks? • How to detect them?

  7. Superabsorbent polymers (SAP)

  8. Autogenous relative humidity Paste C (w/c 0.30 + 20% SF +0.6% SAP) Paste A (w/c 0.35) Paste B (w/c 0.30 + 20% SF)

  9. Autogenous strain Paste C (w/c 0.30 + 20% SF +0.6% SAP) Paste A (w/c 0.35) Paste B (w/c 0.30 + 20% SF)

  10. Samples for crack detection - 3 cement pastes • 1.5, 3, and 6-mm rods • sealed at 32C

  11. 10 1.2 µm ] 1 m µ [ r e t e m a i d e 0.1 r o P 0.01 1.6 MPa 0.1 1 10 100 Intrusion pressure [MPa] Properties of Gallium - melting point 29.8 C • does not wet cement paste • nontoxic

  12. Gallium intrusion

  13. Sample preparation • epoxy resin • grinding • polishing • crack examination: - optical microscope - BSE - EPMA

  14. Crack detection (1)

  15. Crack detection (2)

  16. Conclusions • Cracks before intrusion can be distinguished • High shrinkage, big rod  Cracks

  17. Further research • EPMA • Acoustic Emission • FE calculations

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