Deteriorated hardened cement paste structure analyzed by XPS and 29Si NMR techniques

• The polymerization of silicate of the C–S–H in the HCP can be observed by XPS.
• The structure of C–S–H changed with the degree of calcium leaching.
• The NMR result about silicate in C–S–H was in good agreement with the XPS result.

In this report, X-ray photoelectron spectroscopy (XPS) and 29Si-MAS-NMR was used for the evaluation of deteriorated hardened cement pastes. The deterioration by ammonium nitrate solution was accompanied by changes in the pore structure as well as by structural changes in the C–S–H in the hardened cement paste. The CaO/SiO2 ratio of the C–S–H decreased with the progress of deterioration, there was also polymerization of the silicate in the C–S–H. It was confirmed that the degree of polymerization of silicate of the C–S–H in hardened cement paste can be determined by XPS. It was also shown that the polymerization depends on the structure of the C–S–H.