A super(1)H NMR relaxometry investigation of gel-pore drying shrinkage in cement pastes

The first systematic study of the temporal evolution of the pore-size-distribution (PSD) in mature cement pastes following one and two cycles of drying and rewetting is presented. The PSD is measured using super(1)H nuclear magnetic resonance (NMR) relaxometry. For millimetre sized paste samples dri...

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Bibliographic Details
Published in:Cement and concrete research 2016-08, Vol.86, p.12-19
Main Authors: Gajewicza, A M, Gartnerb, E, Kanga, K, McDonalda, P J, Yermakoub, V
Format: Article
Language:English
Subjects:
Cements
Drying
Evolution
Moisture content
Nuclear magnetic resonance
Pastes
Porosity
Water distribution
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Summary:The first systematic study of the temporal evolution of the pore-size-distribution (PSD) in mature cement pastes following one and two cycles of drying and rewetting is presented. The PSD is measured using super(1)H nuclear magnetic resonance (NMR) relaxometry. For millimetre sized paste samples dried fairly strongly, the volume of water taken up shortly after rewetting slightly exceeds the pre-drying amount. The volume of water in pores > 10 nm far exceeds that in smaller pores. This reverses the situation observed prior to drying. Over subsequent days the water distribution reverts to its original form, so that the dominant fraction is again in the smaller pores. Since the total water content scarcely changes, this indicates a re-arrangement of the nano-scale porosity. Over two drying-rewetting cycles, both reversible and irreversible changes are seen. The effect is not observed in moderately dried pastes.
ISSN:0008-8846
DOI:10.1016/j.cemconres.2016.04.013