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Title: Sodium sulphate crystallisation, water transport and stone decay
Author: Hamilton, Andrea
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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Hydration pressure generated as the anhydrous salt (thenardite) hydrates to form the decahydrate (mirabilite) was originally thought to be responsible for the sever damage to stone buildings and monuments infected with this salt. New results based on an in situ temperature controlled dynamic XRD study show for the first time, the reformation of mirabilite during cooling and provides an insight into the supersaturation attainable in this experiment before reprecipitation of mirabilite. Also of practical interest is the behaviour of sodium sulphate in the presence of other commonly occurring cations. Ca was used for this study due to the wide spread occurrence of gypsum in relation to stone damage.  A synchrotron experiment conducted on beam line 16.4 at Daresbury Laboratory, shows for the first time the precipitation and dissolution of eugsterite (Na4Ca(SO4)3.2H2O) from the starting materials of solid mirabilite and gypsum, cycled up and down in temperature using a glycol cold cell in the path of the beam. Crystallisation by evaporation was also used as another method of investigating the effect of calcium on the crystallisation of sodium sulphate at a single temperature above the mirabilite-thenardite transition temperature of 32.4°C. A definite relationship was found to exist between the amount of calcium in solution, the formation of phase III and the eventual formation of eugsterite. Part of the Skara Brae settlement in Orkney, a site of cultural importance and showing signs of extreme weathering was investigated for sings of salt decay. Many different methods, including water transport analysis, were used to investigate the samples from the site itself and representative samples taken from close to the site to assess the relative important of the decay mechanisms found to exist. The final experimental section of this thesis deals with the analysis of water transport through three commonly used building materials. Characterisation of the materials using a variety of methods is given to explain their strong variation in the water transport properties.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available