Atom Probe Tomography for Nanomodified Portland Cement

Abstract

The study presents the use of Atom Probe Tomography (APT) to investigate the interaction between nanolimestone and Portland cement. APT is an analytical imaging technique that generates a three-dimensional atom-by-atom image of a specimen, with sub-nanometer spatial resolution. For the APT tests, a polished Portland cement clinker with nanolimestone on the surface was hydrated between 2 and 4 h. The hydrated Portland cement clinker was then imaged with a scanning electron microscope to visually determine the degree of hydration. Tip specimens for APT were then formed by FIB lift-out in a FEI Helios Nanolab, followed by annular ion-beam milling to form APT tips targeted on the nanolimestone/cement clinker interface, so that the nanolimestone is located at the apex of the specimen. The results show that the nanolimestone had reacted with the cement clinker. This demonstrates that the use of nanolimestone may not be only providing nucleation sites for cement hydration but is also chemically reacting with the Portland cement clinker within the first few hours of hydration.