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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

Microcrack Detectionin High-Performance Cementitious Materials

Pietro Lura,

Ye Guang, Kyoji Tanaka,

and Ole Mejlhede Jensen

early age cracking
Early-age cracking

Tokyo Institute of Technology, Yokohama, Japan

microcracking
Microcracking

(Bisschop & van Mier 2002)

definitions

Chemical

shrinkage

Autogenous

shrinkage

Definitions

(Jensen & Hansen 2001)

solid

water

air

autogenous shrinkage in hpc
Autogenous shrinkage in HPC
  • Less water
  • More cement
  • Silica fume
slide6

Internal microcracking

  • Does autogenous shrinkage lead to internal cracks?
  • How to detect them?
slide8

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)

slide9

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)

slide10

Samples for crack detection

- 3 cement pastes

  • 1.5, 3, and 6-mm rods
  • sealed at 32C
slide11

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
slide13

Sample preparation

  • epoxy resin
  • grinding
  • polishing
  • crack examination: - optical microscope

- BSE

- EPMA

slide16

Conclusions

  • Cracks before intrusion can be distinguished
  • High shrinkage, big rod  Cracks
slide17

Further research

  • EPMA
  • Acoustic Emission
  • FE calculations