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.