Research

14 pages, 6361 KiB

Open AccessArticle

Natural Cement in Portugal: Context in Cement Production and Architectural Use

by Ana Velosa, Slavka Andrejkovičová, Clara Pimenta do Vale and Fernando Rocha

Heritage 2024, 7(2), 638-651; https://doi.org/10.3390/heritage7020031 - 29 Jan 2024

Viewed by 1361

Natural cement, also known as “Roman cement”, was used across Europe during a historic period, mainly in many building facades, due to its hydraulic properties and aesthetic qualities. In Portugal, the use of natural cement occurred in buildings from the second half of [...] Read more.

Natural cement, also known as “Roman cement”, was used across Europe during a historic period, mainly in many building facades, due to its hydraulic properties and aesthetic qualities. In Portugal, the use of natural cement occurred in buildings from the second half of the 19th century to the beginning of the 20th century, a period during which the use of lime binders decreased and before the massive use of Portland cement. Recent conservation and rehabilitation actions resulting from necessary interventions in heritage buildings from this period have played an important role in revealing evidence of the use of natural cement and clarifying the lacunae of information about this material. Due to the inadequate use of reparation materials in previous conservation and rehabilitation interventions, this study summarizes the historical production, study, and use of natural cement in Portugal. Natural cement results from the calcination of clay-rich limestone (marlstone) without any compositional changes after extraction, distinguishing itself from hydraulic lime due to its higher clay content and allowing for the formation of higher quantities of hydraulic reactive phases without free lime. Although this topic has been approached at a European level, mainly focusing on the production and use of natural cement in Central Europe, in Portugal, it is still necessary to produce and disseminate information on this specific subject. Therefore, this study focuses on the evolution of cement production in Portugal and an analysis of the existing knowledge of the binders used in architectural heritage based on the scientific and historical bibliography. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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13 pages, 28404 KiB

Open AccessArticle

Characterization and Analysis of the Mortars of the Church of San Francisco of Quito (Ecuador)

by M. Lenin Lara Calderón, Inés del Pino, Sol López-Andrés and David Sanz-Arauz

Heritage 2023, 6(12), 7495-7507; https://doi.org/10.3390/heritage6120393 - 29 Nov 2023

Viewed by 1737

Abstract

The relevance of the Franciscan community is reflected in the San Francisco church in Quito, which was built between 1535 and 1755. This architectural work belonging to the Franciscan complex was implanted on a plot of land with an area of 3.5 hectares [...] Read more.

The relevance of the Franciscan community is reflected in the San Francisco church in Quito, which was built between 1535 and 1755. This architectural work belonging to the Franciscan complex was implanted on a plot of land with an area of 3.5 hectares and was one of the first buildings in the Audience of Quito. Eleven mortar samples that covered the walls of the central nave and side chapels were taken from the church’s main temple. The procedure proposed by the authors is based on a combined methodology following the standards and protocols for the less-invasive extraction of heritage samples. Tests included X-ray diffraction, petrography, and scanning electron microscopy with a microanalysis of the samples. Mortars with a rustic composition and rough manufacturing were identified to differentiate two types of mortar, one of earthen with volcanic aggregates and another of lime with volcanic aggregates. The mining data validated the existing historical documentation, the imaginary process, and the stages of the established constructions. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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19 pages, 3913 KiB

Open AccessArticle

Formation of Calcium Oxalate Patinas as Protective Layer on Basaltic Stone Surfaces of 17th Century Raigad Hill Fort, India

by Manager Rajdeo Singh and Rajendra Yadav

Heritage 2023, 6(7), 5374-5392; https://doi.org/10.3390/heritage6070283 - 14 Jul 2023

Cited by 2 | Viewed by 1426

Abstract

This work reports calcium oxalate film formation on basaltic stone surfaces of the 17th-century western India Raigad Hill Fort. Nine stone samples extracted from the exterior surfaces of different historical structures of the fort were investigated under FTIR, optical microscopy, XRD, and SEM-EDX. [...] Read more.

This work reports calcium oxalate film formation on basaltic stone surfaces of the 17th-century western India Raigad Hill Fort. Nine stone samples extracted from the exterior surfaces of different historical structures of the fort were investigated under FTIR, optical microscopy, XRD, and SEM-EDX. The FTIR spectroscopy revealed intense peaks for Ca-oxalate patinas on basaltic stone surfaces. Observation under optical microscopy clearly showed milky white oxalate films, and peaks for crystalline calcium oxalate, including rock silicates, were prominently observed through XRD investigations. The surface morphology, the origin of the oxalate film, and the state of conservation of the basalt rock were investigated through SEM-EDX. The massive structures at Raigad, at a height of about 800 m, have hardly been chemically cleaned or coated with preservatives in the past. The presence of organic filaments in SEM photomicrographs indicated the biological origin of the oxalate patina due to the thick growth of microbiota on the monument stone during very heavy monsoons. The oxalic acid secreted by microbes dislodged the Ca-rich plagioclase of the stone, ensuring Ca-ions’ availability for film formation. The optical and mineralogical analyses suggest that the film is not the result of simple deposition but of the surface transformation of basaltic stone. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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21 pages, 13730 KiB

Open AccessArticle

Quantification of Moisture in Masonry via AI-Evaluated Broadband Radar Reflectometry

by Daniel Frenzel, Oliver Blaschke, Christoph Franzen, Felix Brand, Franziska Haas, Alexandra Troi and Klaus Stefan Drese

Heritage 2023, 6(7), 5030-5050; https://doi.org/10.3390/heritage6070266 - 26 Jun 2023

Viewed by 1474

Abstract

Humidity, salt content, and migration in building materials lead to weathering and are a common challenge. To understand damage phenomena and select the right conservation treatments, knowledge on both the amount and distribution of moisture and salt load in the masonry is crucial. [...] Read more.

Humidity, salt content, and migration in building materials lead to weathering and are a common challenge. To understand damage phenomena and select the right conservation treatments, knowledge on both the amount and distribution of moisture and salt load in the masonry is crucial. It was shown that commercial portable devices addressing moisture are often limited by the mutual interference of these values. This can be improved by exploiting broadband radar reflectometry for the quantification of humidity in historic masonry. Due to the above-mentioned limitations, today’s gold standard for evaluating the moisture content in historic buildings is still conducted by taking drilling samples with a subsequent evaluation in a specially designed laboratory, the so-called Darr method. In this paper, a new broadband frequency approach in the range between 0.4 and 6 GHz with improved artificial-intelligence data analysis makes sure to optimize the reflected signal, simplify the evaluation of the generated data, and minimise the effects of variables such as salt contamination that influence the permittivity. In this way, the amount of water could be determined independently from the salt content in the material and an estimate of the salt load. With new machine learning algorithms, the analysis of the permittivity is improved and can be made accessible for everyday use on building sites with minimal intervention by the user. These algorithms were trained with generated data from different drying studies on single building bricks from the masonries. The findings from the laboratory studies were then validated and evaluated on real historic buildings at real construction sites. Thus, the paper shows a spatially resolved and salt-independent measurement system for determining building moisture. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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13 pages, 3211 KiB

Open AccessFeature PaperArticle

The Susceptibility to Salt Fog Degradation of Stone Cladding Materials: A Laboratory Case Study on Two Limestones from Portugal

by Vera Pires, Luis G. Rosa, Pedro M. Amaral and Joaquim A. R. Simão

Heritage 2023, 6(1), 492-504; https://doi.org/10.3390/heritage6010026 - 07 Jan 2023

Cited by 3 | Viewed by 1760

Abstract

The evaluation of stone cladding material suitability can be a challenge due to the way that stone physical and mechanical properties, and characteristics such as mineralogy, might influence stone performance as a cladding element in a ventilated facade application. Salts can affect natural [...] Read more.

The evaluation of stone cladding material suitability can be a challenge due to the way that stone physical and mechanical properties, and characteristics such as mineralogy, might influence stone performance as a cladding element in a ventilated facade application. Salts can affect natural stone performance, and one of the experimental methods available to study and predict it is through accelerated aging tests such as salt fog chamber cycles. Aging test results should include the analysis of critical stone physical–mechanical properties to fully understand decay effects. The aim of this study was to reduce the lack of knowledge regarding the implications of salt fog on certain fundamental characteristics of stone cladding requirements, such as elastic properties and flexural strength, because these are particularly important properties for ventilated facade systems. A systematic methodology based on artificial salt fog cycles in a climatic chamber, microscopic analysis, weight measurement, flexural strength, and dynamic elastic modulus was performed on two limestones from Portugal: Moleanos (MO) and Semi-Rijo (SR). This study aims to contribute to improved selection stone methods linked to more sustainable stone facades, and the experimental methodology can be further applied to other stone types, particularly the ones most selected for stone cladding applications near coastal areas. In this work, results of salt fog decay cycles are presented and discussed considering their direct contribution for a better stone-cladding dimensioning process. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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21 pages, 6455 KiB

Open AccessArticle

Evaluation of Natural Stone Weathering in Heritage Building by Infrared Thermography

by Giovanna Pappalardo, Simone Mineo, Davide Caliò and Annamaria Bognandi

Heritage 2022, 5(3), 2594-2614; https://doi.org/10.3390/heritage5030135 - 06 Sep 2022

Cited by 12 | Viewed by 2738

Abstract

The application of non-contact diagnostic methodologies is the current challenge in the frame of the cultural heritage, referred to as preservation, monitoring and restoration. Inspired by the potential shown by infrared thermography in rock mechanics’ non-destructive applications, this paper presents the results achieved [...] Read more.

The application of non-contact diagnostic methodologies is the current challenge in the frame of the cultural heritage, referred to as preservation, monitoring and restoration. Inspired by the potential shown by infrared thermography in rock mechanics’ non-destructive applications, this paper presents the results achieved by its use for the quick survey of different weathering types affecting natural stones at historical buildings. Infrared thermography allowed recognizing and mapping the different surface temperatures arising from the presence of efflorescence, subflorescence, alveolization, black crusts and bioweathering at limestone and basalt stones. Infrared data were sided by photogrammetric three-dimensional models of surveyed spots, which provided quantitative data on the thickness of rock affected by mechanical weathering, and key correspondence between the two techniques is highlighted. Achieved results show that infrared outcomes are related to different aspects primarily involving the stone face morphology and color, as well as the environmental conditions at the surveying time. Provided interpretations were validated by field visual inspections, which confirmed the good potential of infrared thermography as a quick weathering diagnostic tool. This study can be therefore considered a starting reference for knowledge development in this scientific field. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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25 pages, 6994 KiB

Open AccessArticle

Contribution to the Understanding of the Colour Change in Bluish-Grey Limestones

by Teresa P. Silva, Daniel de Oliveira, João P. Veiga, Vitor Lisboa, Jorge Carvalho, M. Alexandra Barreiros, Mathilda L. Coutinho, Eduardo Salas-Colera and Rogério Vigário

Heritage 2022, 5(3), 1479-1503; https://doi.org/10.3390/heritage5030078 - 30 Jun 2022

Cited by 2 | Viewed by 2083

Abstract

Bluish-grey limestones have been extensively used as ornamental stones for decoration purposes in buildings, as well as in works of art, and accordingly, have been the target of intense exploration. In Portugal, the Jurassic limestone massif known as the Maciço Calcário Estremenho (MCE), [...] Read more.

Bluish-grey limestones have been extensively used as ornamental stones for decoration purposes in buildings, as well as in works of art, and accordingly, have been the target of intense exploration. In Portugal, the Jurassic limestone massif known as the Maciço Calcário Estremenho (MCE), has been the source of grey-coloured ornamental stones, namely the Azul Valverde (one of the most well-known bluish-grey limestones) and Atlantic Blue varieties, both of which may undergo colour changes in outdoor environments. In this sense, it is important to understand the sudden colour change from bluish-grey to yellow/beige in the same limestone block in a quarry, or even, what happens to the colour when polished limestone is placed outdoors. This study was undertaken using various techniques, namely XRF (X-ray fluorescence spectrometry), XRD (X-ray diffraction), SEM (scanning electron microscopy), DTA–TG (differential thermal analysis/thermogravimetry) and colourimetry. Synchrotron radiation was also used at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) where XANES (X-ray Absorption Near Edge Structure) spectra at Fe K-edge were collected to ascertain the speciation state of Fe in different coloured zones of the limestone, previously checked by EDXRF (energy dispersive X-ray fluorescence). The presence of Fe²⁺ and Fe³⁺ are responsible for the greyish and yellow/brown colour, respectively. On the other hand, the UV radiation from the sun causes a quickened and severe bleaching/fading on the dark blue/grey polished limestone. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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18 pages, 13196 KiB

Open AccessArticle

The Monumental UNESCO Site of Panamá Viejo: Investigation of the Masonry Mortars

by Chiara Ciantelli, Alessandro Sardella, Silvia Arroyo Duarte, Elena Pecchioni and Alessandra Bonazza

Heritage 2022, 5(2), 646-663; https://doi.org/10.3390/heritage5020036 - 27 Mar 2022

Cited by 1 | Viewed by 2646

Abstract

The presented study illustrates the characterisation of several artificial materials (bedding, joint mortars, and plasters) belonging to the masonries of the UNESCO site of Panamá Viejo, located in Panama City (Panama). This monumental site represents the first Spanish settlement on the Pacific Coast, [...] Read more.

The presented study illustrates the characterisation of several artificial materials (bedding, joint mortars, and plasters) belonging to the masonries of the UNESCO site of Panamá Viejo, located in Panama City (Panama). This monumental site represents the first Spanish settlement on the Pacific Coast, founded 500 years ago, in 1519. Through mineralogical and petrographic analyses of the collected samples, as stereomicroscope and polarized light microscopy (PLM) observations of bulk and thin sections, respectively, environmental scanning electron microscopy and micro-chemical investigations (ESEM-EDX) and X-Ray Powder diffraction (XRPD) analysis, it was possible to identify the composition of the materials utilized for the production of mortars and plasters, in addition to the determination of their state of conservation. Therefore, this work represents a substantial step for the preservation of the Panamá Viejo site, in order to support the selection of the most suitable restoration products, such as consolidants, protectives, etc., but also for choosing the most compatible materials for possible replacements/integrations in the masonries. Full article

(This article belongs to the Special Issue Decay and Conservation Studies of Building Mortars and Stones)

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