Determination of Nanomechanical Properties of Cementitious Materials Using an Energy-Based Approach

Abstract

Nanoindentation is increasingly being used for the determination of nanomechanical properties of cementitious materials. The method is based on elastic punch theory to extract mechanical properties of interest from experimental load-displacement data. This theory requires initial unloading stiffness and contact area to be known. In this study, the authors propose a simplified method for the evaluation of stiffness and contact area based on more accurate and realistic interpretation of the load-displacement data. Such interpretation allows them to evaluate both the initial unloading stiffness and the contact area directly as a function of normalized elastic work. The area function derived herein may be used to compute contact area whenever the ratio of indenter tip to maximum penetration depth ratio is in the range of 0.1-1.67. Indentation moduli obtained using these expressions are in good agreement with those obtained by the Oliver and Pharr method for all the phases of hardened cement paste.