NaCl-related weathering of stone: the importance of kinetics and salt mixtures in environmental risk assessment
Godts, Sebastiaan; Orr, Scott Allan; Desarnaud, Julie; Steiger, Michael; Wilhelm, Katrin; De Clercq, Hilde; Cnudde, Veerle; De Kock, Tim
(2021) Heritage Science, volume 9, issue 1, pp. 1 - 13
(Article)
Abstract
Salt weathering is one of the most important causes of deterioration in the built environment. Two crucial aspects need further investigation to understand the processes and find suitable measures: the impact of different climatic environments and the properties of salt mixture crystallization. We demonstrate the importance of kinetics in quantifying
... read more
crystallization and dissolution cycles by combining droplet and capillary laboratory experiments with climate data analysis. The results proved that dissolution times for pure NaCl are typically slower than crystallization, while thermodynamic modelling showed a lower RHeq of NaCl (65.5%) in a salt mixture (commonly found in the built heritage) compared to its RHeq as a single salt (75.5%). Following the results, a minimum time of 30 min is considered for dissolution and the two main RHeq thresholds could be applied to climate data analysis. The predicted number of dissolution/crystallization cycles was significantly dependent on the measurement frequency (or equivalent averaging period) of the climatic data. An analysis of corresponding rural and urban climate demonstrated the impact of spatial phenomena (such as the urban heat island) on the predicted frequency cycles. The findings are fundamental to improve appropriate timescale windows that can be applied to climate data and to illustrate a methodology to quantify salt crystallization cycles in realistic environments as a risk assessment procedure. The results are the basis for future work to improve the accuracy of salt risk assessment by including the kinetics of salt mixtures. [Figure not available: see fulltext.]
show less
Download/Full Text
Keywords: Built heritage, Crystallization, Damage prediction, Porous materials, Salt mixture, Sodium chloride, Weathering, Conservation, Archaeology, Archaeology
ISSN: 2050-7445
Publisher: Springer
Note: Funding Information: This research was funded by the Belgium Science Policy (Belspo) within the framework of BRAIN-be 2.0, Belgian Research Action through Interdisciplinary Networks: project B2/191/P1/PREDICT (Research action B2); joint PhD project PREDICT, Phase Transitions of Salts under Changing Climatic Conditions. The authors further acknowledge the funding for the GenRH humidity generator through “BOF, project UG_2832369580”, “JPI-JHEP project KISADAMA” and “FWO Research Grant 1521815N”. Funding Information: This paper is the extended result of a network project KNOWMORE (Heritage stone Monitoring and Remediation: knowledge exchange placements (2019?2021) between the Royal Institute for Cultural Heritage (KIK-IRPA), Ghent University, Oxford University and The Belgian Building Research Institute (BBRI) and an introduction to the continuing BRAIN 2.0 joint PhD project PREDICT, Phase Transitions of Salts under Changing Climatic Conditions. The authors wish to thank Prof. Dr. Heather Viles (University of Oxford) for her valuable input and inspirational discussions during the KNOWMORE project. We also wish to thank Prof. Dr. Steven Caluwaerts (UGent) and the MOCCA project (http://observatory.ugent.be) for climate data. Alexandre Gillon, (Polytech Clermont-Ferrand, Engineering Physics, France) is thanked for his help with the analysis of NaCl crystallization-dissolution carried out as part of his distance learning internship at KIK-IRPA. We acknowledge Alice Vrancken (University of Antwerp, ARCHES), as the results from her Master thesis supported decisions made throughout the experimental and theoretical work. Publisher Copyright: © 2021, The Author(s).
(Peer reviewed)
See more statistics about this item