Nanoindentation size effect of cement pastes

Title: Nanoindentation size effect of cement pastes
Author(s): Jirí Nemecek, Luboš Kopecký, Zdenek Bittnar
Paper category : conference
Book title: NICOM 2: 2nd International Symposium on Nanotechnology in Construction
Editor(s): Y. de Miguel, A. Porro and P.J.M. Bartos
Print-ISBN: 2-912143-87-X
e-ISBN: 2912143888
Publisher: RILEM Publications SARL
Publication year: 2006
Pages: 161 - 168
Total Pages: 8
Nb references: 11
Language: English

Abstract: This paper focuses on nanoindentation of cement pastes and the evaluation of mechanical properties at microlevel. Nanoindentation belongs to the group of the experimental techniques that can be used for direct measuring of the mechanical response of a material at submicron length scale. In case of cement paste, micromechanical response can be measured for its individual material phases (hydrated and unhydrated) and results evaluated statistically. This paper addresses important issues that have to be taken into account in evaluation of nanoindentation data. Similarly to large-scale structures one can observe a size effect in material properties if the penetration depth is varied. Such property was already reported for plastic materials like metals. Although nanoindentation is a powerful technique, evaluation of results has to take into account a lot of microscale phenomena that are not present in macroscopic tests. Multiple experiments have been conducted on cement paste where penetration depths were ranging from 200 to 5500 nm. It was found cement paste exhibits strong size effect in elastic properties measured by nanoindentation and evaluated by standard Oliver-Pharr procedure for some cases of loading. Therefore, nanoindentation results should always be considered together with the indentation size. A number of reasons are responsible for such behavior. Besides the well-known factors it was found that the major effect is the loading time and associated creep of the material. As shown in the paper evaluation of elastic properties of creeping material like cement paste must be done with care and suitable testing method have to be employed.

Online publication: 2005-11-17
Publication type : full_text
Public price (Euros): 0.00