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Impedance spectroscopy to characterise microsctructural changes in liquid and solid phases of mortars exposed to high temperature



Title: Impedance spectroscopy to characterise microsctructural changes in liquid and solid phases of mortars exposed to high temperature
Author(s): I. Sánchez, M. Sánchez, M.A. Climent, and M.C. Alonso
Paper category : conference
Book title: 2nd International RILEM Workshop on Concrete Spalling due to Fire Exposure
Editor(s): E.A.B. Koenders and F. Dehn
ISBN: 978-2-35158-118-6
e-ISBN: 978-2-35158-119-3
Publisher: RILEM Publications SARL
Publication year: 2011
Pages: 43 - 51
Total Pages: 9
Nb references: 21
Language: English


Abstract: The moisture content evolution and distribution during fire in the bulk of concrete seems to have a significant role in the response under fire. The influence of the liquid phase in phenomena such as spaling is very important, so it is desirable to look for alternative techniques that allow studying, in a non destructive way, the evolution of both liquid and hydrated solid phases during heating. In recent studies High Frequency Impedance Spectroscopy (HFIS) has proved to be a technique very sensitive to moisture content of cementitious materials, as well as to changes of the solid phase, however the use of HFIS has been restricted to ambient temperature.

In this work the HFIS in the frequency range from kHz to MHz has been used to characterize mortars exposed at different temperatures from 20 to 250ºC. The first results show that the measurements can be easily taken in this range of temperature, the technique is very rapid, and sensitive. The analysis of the spectra has been done using a model that separates solid and liquid phase contributions. The results indicate that changes of the solid phases start at temperatures lower than 100 ºC, but they become important among 150ºC and 200 ºC. The liquid phase evolves and completely has disappeared at temperatures 200ºC.


Online publication: 2012-01-17
Publication type : full_text
Public price (Euros): 0.00