Nanomechanical Study of Cement Pastes by Statistical Nanoindentation and Peakforce QNM

Abstract

The study is related to the EU 7th Framework Programme CODICE (COmputationally Driven design of Innovative CEment-based materials) project. The main aim of the project is the development of a multi-scale model for the computer based simulation of mechanical and durability performance of cementitious materials. As part of the task to study the micromechanical properties of computationally driven designs and validate the model predictions, extensive work on micro/nano-mechanical characterisation of cement-based materials has been conducted, which cover synthetic C3S, C2S pastes, cement pastes hydrated at different ages and pastes subjected to accelerated calcium leaching, etc. Statistical nanoindentation and micro-mechanical property mapping technique was used to study intrinsic properties of different hydrate phases and microstructures down to approximately 1 µm. A new experimental technique – Peakforce QNM was also used to examine mechanical properties of cement paste micro/nano-structures down to approximately 10 nm. The importance of proper specimen preparation is highlighted, particularly for the early-aged and leached samples due to their weak and fragile microstructure. The results obtained from the two experimental techniques are presented and advantages/limitations for each technique discussed.