Interactions of fully formulated epoxy with model cement hydrates

Abstract

The surface energy of cement paste components (calcium silicate hydrate [C-S-H], ettringite and portlandite) before and after treatment with an organic coating has been characterised by X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography at 35 °C using n-alkanes, 1-alkene, chloroform, tetrahydrofuran, diethyl ether and CCl₄ molecular probes. Complementary investigations on the interfacial chemistry were also conducted by Fourier transform infrared spectroscopy and Differential scanning calorimetry analyses. Changes in the dispersion contribution to the surface energy () and acid–base interaction energies were found to be significantly reduced by the organic coating. The XPS allowed the surface chemistry changes induced by the organic coating to be monitored. In particular, the C1s spectra were peak fitted in order to deduce the contribution of the organic coating materials to the total carbon content on the surface. This study showed not only the existence of hydrate-hardener donor–acceptor adduct formation but also presence of interactions between the hydroxide groups OH of the epoxy and portlandite.

Keywords:

• C-S-H
• ettringite
• portlandite
• cement paste
• adhesives
• adhesion
• wetting
• XPS
• IGC
• surface energy

Notes

1. Hydraulic binders are mineral compounds, such as cement, whose reaction with water leads to the formation of hardened cementitious matrices.