Creep of hardened cement paste - The role of interfacial phenomena

Real-time changes in the microstructure of hardened cement paste subjected to a sustained load were followed through the coupling of an a. c. impedance frequency analyzer with a miniature loading system. A rationale for the time dependent effects of the sustained load on the characteristics of the impedance spectra is provided. The analysis suggests that the sustained load can influence the conductivity of the solid-liquid interface, the thickness of the Stern layer and pore structure parameters in a manner that would result in a time dependent increase in the diameter of the high frequency arc. This was demonstrated experimentally. The impedance analysis included an assessment of the relevance of the high frequency arc depression angle to creep behavior of cement paste. A possible explanation of the changes to the depression angle with time under load in terms of interfacial phenomena at the nanoscale is given.