Adapting the RILEM 271-ASC accelerated salt weathering test to stone/ plaster combinations: First experimental results
B. Lubelli (TU Delft - Heritage & Architecture)
Davide Gulotta (Getty Conservation Institute)
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Abstract
Salt crystallization is one of the most common causes of decay in porous building materials. Plasters and renders, mainly due to their location at the surface of walls, where most often salt accumulation occurs, are particularly subjected to salt decay. Despite the relevance of the problem, there are no standard salt weathering tests for the assessment of the durability of plasters and renders against salt decay. This research proposes a salt weathering
procedure, based on an adaptation of the RILEM TC 271-ASC recommendation, and it validates it by applying it to three plaster types (based on hydrated lime, natural hydraulic lime and hydrated lime-cement). Combined stone/plaster specimens are prepared and contaminated with 10 % (weight salt/weight solution) sodium sulphate and sodium chloride solutions. The damage development is assessed by visual and photographic monitoring, gravimetric measurements of the material loss, assessment of salt distribution in the specimens, and SEM
observations supported by EDX mapping on thin sections. The results show that the test procedure is effective in causing damage in the tested plasters, within the time period of the test (about 4 months), and that damage increases with subsequent cycles. The decay severity and type differ depending on type of salt and/or of plaster.
Suggestions for further improvement of the procedure are provided.
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