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ULTRAHIGH-PERFORMANCE CONCRETE: Material Engineering by Nano-indentation Testing and Nano-mechanical Analysis

  • P. ACKER

  • LAFARGE - Centre de Recherche



Why do we need nanotesting in concrete technology?

  • Can we determine the constitutive equations of concrete from those of its components?

  • do the homogenization techniques work for concrete?

  • Can we measure the intrinsic characteristics of each component in situ? (including C-S-H?)

  • is the nano-indentation footprint size compatible?

  • considering that:

  • Cement hydration depends on local conditions (can only be reproduced in vivo)

  • SEM observations do not say anything about the local mechanical state



SUMMARY

  • The tested material: Ductal® (UHPFRC)

  • Nano-indentation testing and protocol

  • Results and discussion

  • Conclusions and perspectives



What is Ductal® ?









Principle of Ductal® mix design

  • Principle of Ductal® mix design



The volumetric balance of hydration:



Volumetric balance for OPC, HPC, and UHPC



Thermodynamic relationship between RH and capillary pressure



TEM photos of C-S-H from Ductal®



Indentation Testing is now possible on a smaller scale:



Typical results of a nano-indentation test



Typical curve obtained on C-S-H:



Nano-indentation test results on Ductal®



Main conclusions

  • On the microscopic scale, each component is elastoplastic or viscoplastic; no damage occurs;

  • C-S-H is the only component that shows creep;

  • viscous strain of C-S-H is totally unrecoverable.



Other conclusions



What we know about shrinkage





Suggested mechanism for C-S-H creep





LAFARGE - Centre de Recherche




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