Cit:Pel.etal:2014
| Autor | Pel, L. and Gupta, S. |
| Jahr | 2014 |
| Titel | Paradoxical drying due to salt crystallization; the effect of ferrocyanide |
| Bibtex | |
| DOI | 10.5165/hawk-hhg/264 |
| Link | Datei:7 SWBSS-2014 Pel etal.pdf |
| Bemerkungen | In: De Clercq, Hilde (editor): Proceedings of SWBSS 2014. Third International Conference on Salt Weathering of Buildings and Stone Sculptures Royal Institute for Cultural Heritage, Brussels, Belgium, 14-16 October 2037, S. 77-87 |
Eintrag in der Bibliographie
| [Pel.etal:2014] | Pel, L.; Gupta, S. (2014): Paradoxical drying due to salt crystallization; the effect of ferrocyanide. In: Hilde De Clercq (Hrsg.): Proceedings of SWBSS 2014 3rd International Conference on Salt Weathering of Buildings and Stone Sculptures,KIK-IRPA, Royal Institute for Cultural Heritage Brussels 77-87, 10.5165/hawk-hhg/264. |   |
Keywords[Bearbeiten]
NaCl, crystallization, drying, inhibitor, NMR
Abstract[Bearbeiten]
Salt damage of historical porous materials is mainly due to the crystallization of soluble salts due to drying. It is known that efflorescence changes the drying kinetics of porous media by changing the boundary conditions near material/air interface. In this study we focused on the influence of NaCl on the drying behavior. The results show that salt changes the drying process. At low relative humidities (RH ~ 0%), the drying rate of a brick saturated with NaCl solution is much lower than the drying rate of water saturated brick. Moreover, the presence of salt suppresses the development of a receding front. In this case homogenous drying of the material continues to very low saturation values. This is due to salt crystallization near the surface of the brick that causes blockage of the pores. This blockage reduces the evaporation rate at the surface. Increasing the relative humidity to 55% and 70% RH with the brick saturated with the salt solution leads to a paradoxical situation with evaporation rates greater than for 0% RH. The paradox is explained by the impact of the efflorescence microstructure on the evaporation rate, leading to the formation of a blocking crust for sufficiently high evaporation rates and non-blocking efflorescence for sufficiently low evaporation rates. With the addition of ferrocyanide crystallization inhibitor at low relative humidity, due to its effect on crystal morphology, salt crystallizes as efflorescence and the saturation concentration was attained very slowly inside the brick; the fired-clay brick dries much faster than without inhibitor.