Search

The cathedral of Santa Maria, where the Munoz Chapel is located, is the most remarkable monument of the UNESCO Wold Heritage City of Cuenca (Spain). This emblematic chapel suffers an intense stone weathering by crystallization of a complex mixture of salts including epsomite, hexahydrite, gypsum, chlorides and phosphates. The salt dynamics is controlled by a variable indoor environment with daily and seasonal cyclicality. A methodology combining salt analysis, environmental monitoring and non-destructive stone inspection was adopted in order to understand the salt crystallization dynamics and finally, to design an adapted preventive conservation plan focused on the mitigation of the salt damages. Moreover, new parameters are designed in order to quantify the microenvironmental variability, establishing a new methodology for the analysis of indoor environments. Obtained results reveal that stone weathering is mainly due to: (1) the transformation of both CaSO4 and MgSO4·4H2O into CaSO4·2H2O and MgSO4·6H2O, respectively; and (2) the direct crystallization of MgSO4·6H2O in the porous system. These phases crystallize as efflorescences and as subflorescences, causing granular disintegration, peeling and scaling on the stone. Several preventive measures are finally proposed, being focused on two main objectives: (1) reducing the access of salts and moisture to the monument; and (2) establishing a nonaggressive environment, keeping temperature and relative humidity constants in the range of 15−20 °C and 40–50%, respectively. This proposed climate range is defined in order to avoid both the crystallization of new salts in the porous system of the stone as well as volume changes of the present salts. This study constitutes a pilot project where to test the efficiency of these preventive measures that could be extensive to the whole cathedral complex.

This work analyses the characterization of the hygric behaviour of a stone heritage material by solving the inverse problem using experimental data obtained from a water absorption by capillarity test (EN 15801). This common test is undemanding and requires relatively simple equipment as compared to other hygric characterization tests. For the solution of the direct problem of transient flow in partially saturated porous media, a computational module was developed in COMSOL Multiphysics that includes the conceptual model from the standard EN 15026. The selected material was the heritage stone of the Cuenca Cathedral, differentiating between two characteristic lithotypes: one with greater porosity and another that is more resistant, with more reduced porosity. Based on the experimental results, the intrinsic permeability and the parameters of the moisture storage function are estimated for the two lithotypes. Similarly, contrast tests were conducted to quantify the estimation error. A stochastic analysis was performed to assess if the estimated hygric parameters satisfactorily characterize the behaviour of the studied stone.

This paper presents a user-friendly tool&mdash, FLoW1D (One-Dimensional Water Flow)&mdash, for the estimation of parameters that characterize the unsaturated moisture transfer in porous building materials. FLoW1D has been developed in Visual Basic for Applications and implemented as a function of the well-known Microsoft Excel&copy, spreadsheet application. The aim of our work is to provide a simple and useful tool to improve the analysis and interpretation of conventional tests for the characterization of the hygric behavior of porous building materials. FLoW1D embraces the conceptual model described in EN 15026 for moisture transfer in building elements, and its implementation has been verified and validated correctly. In order to show the scope of the code, an example of an application has been presented. The hygric characterization of the limestone that is mostly employed in the Cathedral of Santa Maria and San Julian in Cuenca (Spain) was conducted based on an analysis of the conventional water absorption by capillarity tests (EN 15801).

The good knowledge of the moisture transfer in materials used in the construction of architectonic cultural heritage is a key issue to define conservation and restoration actions. In recent years, numerical models are used in this field to improve the hygrothermal characterization of these materials. However, the structure of state functions involved in the modelization is not standardised, and they present a highly empirical parametrization . For this reason, the main objective of this work is to review the structure of the state functions corresponding to moisture transport (moisture content, liquid and vapour water permeabilities) and to suggest more compact functional structures that allow reducing the number of parameters. Two conventional tests used to characterize the hygrothermal behaviour of heritage elements, (i) water absorption by capillary test (EN 15801) and (ii) water vapour permeability test (EN 15803) have been simulated to check the capacity and quality of the moisture transfer simulation with the new functions. These numerical exercises were carried out using a moisture transport module implemented in COMSOL Multiphysics. The material selected was the limestone used in the construction of the Cathedral of Santa Maria and San Julian (Cuenca, Spain). The satisfactory results obtained demonstrate the utility of the functions proposed to model the hydraulic conductivity and diffusion resistance factor. A significant reduction in the number of material parameters is achieved without compromising the simulation capacity.

The historic city of Cuenca is a first-rate architectural complex in terms of its architectural and cultural landscape. The conservation of the existing stone requires comprehensive studies that take into account the petrological and petro-physical source materials (historical quarries) and condition (study of pathologies) of the material used. Porosity and pore-size distribution are important properties as they partially determine weathering. This paper studies the pore system of the historic building stones of Cuenca. These stones have a total porosity of 10–20 % with pore-size intervals of 0.1–10 μm. These characteristics make them sensitive to processes such as salt and ice crystallization pressures. New introduced stones (e.g., Vara del Rey stone) with a different porosity and pore-size intervals may cause incompatibility problems in the short and middle term.