P acker lafarge centre de Recherche

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