Recession rate of carbonate rocks used in cultural heritage: Textural control assessed by accelerated ageing tests

Abstract

• Quantification of the relation between grain-size and recession in carbonate rocks. • Improved understanding of the complexity of recession rate in carbonate rocks. • Definition of correction coefficients to be applied to known recession equations. • New methodological approach to estimating future stone deterioration in cultural heritage. In this study, the recession rate of eleven carbonate stones widely used in the cultural heritage of northeastern Italy and differing in their textural features and mineralogical composition was investigated. Samples of stones known as Vicenza (Nanto and Costozza varieties), Carrara marble, Verona (Red and Brown varieties), Asiago, Istria (Orsera variety), Aurisina, Chiampo (Ondagata and Paglierino varieties), and Botticino were subjected to accelerated ageing tests in an environmental test chamber for simulating the effect of rainfall, using two different water compositions corresponding to rainwater chemistry in the cities of Bologna (pH ∼ 7) and Stresa (pH ∼ 6) in Italy. Bulk stone recession was evaluated considering sample weight loss as a function of the number of wetting cycles. Moreover, direct measurements of recession were performed by confocal microscopy, which allowed 3D surface reconstruction of the stone surface and evaluation of differential recession as a function of calcite grain size. The results also allowed the definition of correction coefficients for calculating more precisely the recession rate of carbonate rocks using known recession equations from the literature. This pilot study illustrates a rapid and efficient methodological approach that can be used for providing reliable estimates of future stone deterioration in cultural heritage, related to specific environmental conditions and expected climate scenarios, which can be exploited for evaluating risk-based protection measures of a variety of historical artifacts and structures.