Reaction of clinker surfaces investigated with atomic force microscopy

The application of microscopy to investigate cement hydration has widely spread in the last decades. For instance, scanning electron microscopy (SEM) is of primary importance to detect the formation of microstructures and detect their chemical composition. In this work, atomic force microscopy (AFM), which is a relatively less diffused technique, is applied to illustrate and estimate changes of the surface roughness of a clinker substrate, treated with different electrolytic solutions, with and without superplasticizer, at different times of hydration. Furthermore, SEM images are collected to characterize the chemical composition of hydration products formed on the clinker surface. It is shown that surface reaction increases drastically with the increase of the pH, and that surface roughness changes occur mainly in the first minutes of hydration. Moreover, the formation of hydration products is reduced when the clinker is treated with solutions containing polycarboxylate ether-based superplasticizer. Additionally, AFM images collected in tapping mode revealed the presence of nano-structures on calcium silicate phase.

Graphical abstractThe formation of portlandite on clinker surface after 18 h of hydration is reduced by the presence of superplasticizer (PCE).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Clinker reaction is studied by AFM and EDX varying the hydration time and the solutions. ► Surface reaction increases with pH and main surface roughness changes occur after 10 min. ► The hydration is slowed down in presence of superplasticizer. ► AFM images show nano-structures with heterogeneous elasticity and adhesion forces.