Low-temperature phase transitions of pore water in hardened cement paste

Title: Low-temperature phase transitions of pore water in hardened cement paste
Author(s): R.E. Beddoe
Paper category : conference
Book title: International RILEM Workshop on Frost Resistance of Concrete
Editor(s): M. J. Setzer, R. Auberg and H. - J. Keck
Print-ISBN: 2-912143-30-6
e-ISBN: 2351580370
Publisher: RILEM Publications SARL
Publication year: 2002
Pages: 161 - 168
Total Pages: 8
Nb references: 7
Language: English

Abstract: Differential scanning calorimetry (DSC) was used to investigate the sub-zero behaviour of pore water in hardened cement paste (hcp) stored at different relative humidities (61 to 96 %RH) and in solutions containing up to 9 wt.% NaCl. A special cyclic measuring procedure revealed three phase transitions in the gel pore water. The transitions occur at -39, -31.0 and -24°C during cooling and are due to different distinct levels of water structuring in pores falling into three size groups covering pore radii between 2 and 5 nm. The curvature of the pores is approximately cylindrical. Chloride ions in the pore water cause the transitions to shift and broaden towards lower temperatures in accor¬dance with the bulk NaCl-H2O phase diagram. The entropy of the pore water is lowered by bulk solution effects and the enhancement of pore water structuring by chloride ions.

Online publication: 2010-06-28
Publication type : full_text
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