Search Results (154)

The development of sustainable cementitious materials is crucial to reduce the environmental footprint of the construction industry. Alkali-activated materials (AAMs) have emerged as promising environmentally friendly alternatives; however, their compatibility with natural stone in heritage structures remains poorly understood, especially regarding salt migration and related damage to stones. This study presents a novel methodology for assessing salt movement in solid materials between two types of stones—Boñar and Silos—and two types of binders: blended Portland cement (BPC) and an AAM. The samples underwent capillarity and immersion tests to evaluate water absorption, salt transport, and efflorescence behavior. The capillarity of the Silos stone was 0.148 kg·m⁻²·t^−0.5, whereas this was 0.0166 kg·m⁻²·t^−0.5 for the Boñar stone, a ninefold difference. Conductivity mapping and XRD analysis revealed that AAM-based mortars exhibit a significantly higher release of salts, primarily sodium sulfate, which may pose a risk to adjacent porous stones. In contrast, BPC showed lower salt mobility and different salt compositions. These findings highlight the importance of evaluating the compatibility between alternative binders and heritage stones. The use of AAMs may pose significant risks due to their tendency to release soluble salts. Although, in the current experiments, no pore damage or mechanical degradation was observed, additional studies are required to confirm this. A thorough understanding of salt transport mechanisms is therefore essential to ensure that sustainable restoration materials do not inadvertently accelerate the deterioration of structures, a process more problematic when the deterioration affects heritage monuments. Full article

A temporal monitoring of monumental buildings in calcarenite, exposed outdoors in the considered Mediterranean environment of Southern Italy, was performed using XPS, the surface-specific technique. The methodology adopted to monitor the surfaces interacting with atmospheric agents and biotic/abiotic pollutants involved progressive sampling, extended to about five years, from the walls of a new building, specifically installed in the immediate vicinity of an ancient farmhouse in an advanced state of degradation. Taking the ancient building as the final temporal reference, the aim was to obtain adequate information on the degradation processes of calcarenitic stones, from the initial and evolving phases of the new building towards those representative of the old reference. A large set of XPS data was obtained by resolving, through curve-fitting, the acquired spectra into component peaks, identified as ‘indicator’ chemical groups, which trend as a function of time, supported by PCA, demonstrates a close compositional similarity between the samples of the new building analyzed after 52 months from its installation and those of the ancient building dating back to over a century ago. The results obtained can be considered in the diagnostic strategy of the ongoing PNRR programs dedicated to the care of historical monuments and ecosystem sustainability. Full article

The crystallization of soluble salts is one of the most significant agents of deterioration affecting porous building materials in historical architecture. This process not only compromises the physical integrity of the materials but also results in considerable aesthetic, structural, and economic consequences. Soluble salts involved in these processes may originate from geogenic sources—including soil leachate, marine aerosols, and the natural weathering of parent rocks—or from anthropogenic factors such as air pollution, wastewater infiltration, and the use of incompatible restoration materials. This study examines the role of capillary rise as a primary mechanism responsible for the vertical migration of saline solutions from the soil profile into historic masonry structures, especially those constructed with calcareous stones. It describes how water retained or sustained within the soil matrix ascends via capillarity, carrying dissolved salts that eventually crystallize within the pore network of the stone. This phenomenon leads to a variety of damage types, ranging from superficial staining and efflorescence to more severe forms such as subflorescence, microfracturing, and progressive mass loss. By adopting a multidisciplinary approach that integrates concepts and methods from soil physics, hydrology, petrophysics, and conservation science, this paper examines the mechanisms that govern saline water movement, salt precipitation patterns, and their cumulative effects on stone durability. It highlights the influence of key variables such as soil texture and structure, matric potential, hydraulic conductivity, climatic conditions, and stone porosity on the severity and progression of deterioration. This paper also addresses regional considerations by focusing on the context of Spain, which holds one of the highest concentrations of World Heritage Sites globally and where many monuments are constructed from vulnerable calcareous materials such as fossiliferous calcarenites and marly limestones. Special attention is given to the types of salts most commonly encountered in Spanish soils—particularly chlorides and sulfates—and their thermodynamic behavior under fluctuating environmental conditions. Ultimately, this study underscores the pressing need for integrated, preventive conservation strategies. These include the implementation of drainage systems, capillary barriers, and the use of compatible materials in restoration, as well as the application of non-destructive diagnostic techniques such as electrical resistivity tomography and hyperspectral imaging. Understanding the interplay between soil moisture dynamics, salt crystallization, and material degradation is essential for safeguarding the cultural and structural value of historic buildings in the face of ongoing environmental challenges and climate variability. Full article

The church of Saint Felix in Girona (Spain) is crowned by an octagonal bell tower with a stone pinnacle at each corner. It was built using dry-joint stone masonry, a technique that involves laying stones in a precise pattern to create a solid and durable structure. In order to strengthen the connection between the stone blocks of the pinnacles, a wooden bar was placed through a central hole carved in the stone structure. Today, the inner structure has completely disappeared. During maintenance and repair work, it was decided to restore the functionality of the disappeared reinforcement by installing a titanium bar in its place. Due to the uncertainty associated with the pinnacle’s behaviour and the lack of both, a proper numerical model of the monument, and an extensive characterization of the materials, a strategy based on multiple approaches was designed. The proposed strategy was based on combining numerical and experimental models, the final objective being to determine the length and mechanical properties of the metallic inclusion, considering the effects of gravity, wind, and seismic forces. A scale model of the pinnacle was evaluated in laboratory conditions. The results were used to calibrate a numerical model representing the scale specimen. After calibration, the results were extrapolated to a full-scale numerical model. The experimental and numerical results showed that the pinnacles needed to be reinforced along their entire height. The tensile stresses cause by wind and seismic forces at different levels, could not be compensated without the contribution of the titanium bar inserted into the pinnacle. Full article

For decades, in historical research, archeological vestiges have been linked with geomancy and cults of the mythical ancestors of a group of the population. This is particularly true in Eastern Asia and especially in China, Korea, and Japan. A fundamental problem of Japanese archeology is that few of the remnants were realized in stone. One of the most important parts of archeological sciences is the study of Necropolises or ancient interments. From the 1970s onwards, in the relatively “new” and promising land of Hokkaido, cemeteries were built with the concept of landscape in mind; this is also due to the lavish vegetation features of this northernmost island of Japan. In the case of the Takino cemetery on the plains of Sapporo, Hokkaido, whose construction began in 1982, solemnity and religiousness were incorporated by producing exact stone replicas of famous funerary landmarks from antiquity as such materials were inexistent in the Nipponese Isles. This trend to grant eternity included traditional Buddhist funereal monuments like the Stupa, Seokguram grotto, and Kamakura sites, but at a certain and exuberant point, under the influence of Isamu Noguchi, it reached Stonehenge in England and the Moai from Easter Island in Polynesia (being after all located in a remote isle of the Pacific Ocean). In this article we will outline such process of generation and overall conception, analyzing the inclusion and architectural assembly of the different compounds and the recent and extraordinary additions projected and built by the celebrity architect Tadao Ando. We expect, in this manner, to facilitate the comprehension of the significance of venerable landscape sublimated through archeology for the Nipponese modern civilization. Full article

Around the world, a large number of stone artifacts have been exposed to air for long periods of time, showing multiple types of deterioration that have attracted widespread attention. Among them, there is an often overlooked deterioration of stone artifacts, i.e., black stains on the surface of the calcareous stone, which are tightly bonded to the substrate as a result of the long-term deposition of air pollution. However, due to the current lack of a clear understanding of the black stains, people often tend to use the wrong cleaning and conservation methods, which is not conducive to sustainable conservation. Therefore, there is an urgent need to comprehensively recognize the black stains in terms of material properties and environmental sustainability to guide scientific sustainable conservation methods. To this end, in this paper, we take the black stains observed on marble buildings in the Xianling Tomb, China, as an example, and for the first time, we aim to create a comprehensive understanding of black deposition from the aspects of material properties and environmental characteristics. Multi-analytical approaches, including polarized light microscopy, X-ray fluorescence (XRF), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), were employed to discern the differences between the substrate and black stains. The results revealed that the formation of black stains was attributed to prolonged exposure to various air pollutants (PM, SO₂, NO₂, CO, and O₃). Subsequently, observational data from 2015 to 2023 were utilized to investigate the temporal evolution of local air pollutants and their coupled resonances. Multi-scale variations (annual, seasonal, monthly, weekly, and daily) of pollutant concentration sequences were identified, which helps us to have a clearer perception and to proactively control air pollutants in the region from different cycles. In addition, wavelet coherence (WTC) demonstrated significant time-scale dependency in correlation with air pollutants, which provides effective data support for the coordinated control of air pollutants. This study reveals the mechanism of black stain deterioration on stone artifact surfaces, provides data support for the control and prediction of air pollutants oriented to the sustainable conservation of stone artifacts, and provides a novel and comprehensive approach to the scientific knowledge and sustainable conservation of stone artifacts. Full article

This experimental study analyses the extent of chemo-mineralogical changes that occur when a building stone encounters a cycling isothermal treatment at 600 °C. Four carbonate and two silicate European building stones were analysed in their fresh quarried and thermally treated conditions by means of colour measurements, in situ X-ray diffraction (XRD), and optical microscopy. Furthermore, powdered samples were characterised by Fourier-transform infrared spectroscopy, simultaneous thermal analysis, and cycling thermogravimetry (TG). The in situ XRD spectra revealed a surface-limited phase transformation of solid calcite and dolomite under isothermal conditions during the first 10 min at 600 °C and 500 °C, respectively. The onset of thermal decomposition and extent of phase transformation were governed by the microstructure of the solid samples. Inter- and intragranular microcracks are induced to varying degrees, and their incidence depended on the stone’s microstructure. Discolouration indicated a transformation of minor elements across the entire analysed sample volumes. Kaolinite was preserved even after three hours of thermal treatment at its dehydroxylation temperature due to its sheltering in confined pore spaces. Mass loss was more pronounced when cyclic treatment was employed compared to a non-periodic treatment, as determined by a TG analysis performed at same time intervals. Examining the chemo-mineralogical and microstructural changes caused by heat treatment allows us to study how and if regaining mechanical strength and restoring physical properties are possible for purposes of heritage restoration after fire damage. Full article

Ancient stone masonry is a composite structure, mainly comprised of stone elements. During restoration, stone elements are sometimes found to present serious fragmentation, and their structural continuity must be re-established. In such cases, an adhesive material can be applied to reattach the detached fragment to its original position, with or without the use of pins or anchors, according to the size of the fragment and its position. However, many considerations must be taken into account regarding compatibility with the ancient material and the performance and longevity of the intervention. In the current study, a series of pastes are designed for the reattachment of stone fragments, with and without the concurrent use of titanium pins, aiming to re-establish the continuity of the porous stone elements of the Acropolis circuit wall. The designed pastes are examined in terms of physical and mechanical characteristics and assessed in relation to their compatibility with the original stone material, while their effectiveness as adhesive and/or anchoring materials is evaluated through a real-time and -scale pilot application on site at the Acropolis monument work site using fragments of the original ancient stone material. The natural lime–metakaolin paste presents the optimum results as an adhesive and anchoring material. Full article

The stone Ensemble from Corbii de Piatrǎ Romania arouses a continuous scientific interest, with the final goal being to obtain an exhaustive and multidisciplinary package of results that will become the support of an extensive restoration project. The cave painting stands out as the most important and most affected by the advanced degradation among the historical monuments in Romania. This article provides for the first time a radiocarbon dating of the first forms of painting by establishing the age of the mortar/plaster used as a pictorial support. Being a very complex context from the point of view of the type of datable material and the disappearance over time through degradation of other elements that would ensure a simpler and more reliable radiocarbon dating (such as the straws used to form the material), it was necessary to use a multidisciplinary approach for the selection of samples and for supporting the radiocarbon results. The set of analyses consisted of visualization techniques through microscopy and compositional analysis, providing information on the similarities/differences between the samples, the degradation mechanisms/impurities and the quality of the calcium carbonate dated by the Accelerator Mass Spectrometry (AMS) technique. The results supported each other, ensured the selection of reliable radiocarbon data and established the most probable moment of the early interventions, namely the two phases corresponding to the 14th century. Full article

In restoration practice, direct methods become necessary when indirect methods fail and when aesthetic, chemical, or physical biodeteriorative effects threaten the integrity and legibility of the artifact. More effective methods that prioritize the health of workers and the environment are essential for the outdoor stone monument’s conservation. Although several low-impact methods have been proposed, more case studies are needed to address different biopatina types, products, and lithic substrates. Within the COLLINE Project we focused on peperino, a dark volcanic stone widely used in central Italy since the 7th century BCE, because it has been poorly investigated in terms of diversity of biodeteriogens and low-impact methods for their removal. Direct observation, culture methods, and molecular identification have been applied for the identification of biodeteriogens with particular attention to black meristematic fungi. Three low-impact products, namely a dimethyl sulfoxide (DMSO)-based gel, BioTersus^® (essential oil-based), and Nasier (enzyme-based) were tested in ex situ (on a colonized slab) and in situ trials (on the pulpit of the S. Francesco alla Rocca Basilica, Viterbo, Italy). Three analytical methods, namely reflectance spectroradiometry, laser-induced fluorescence (LIF), and hypercolorimetric multispectral imaging (HMI) were used to test the cleaning efficacy. Results evidenced the strong influence of direct irradiation and water availability in the balance and distribution of phototrophs, fungi, and lichens. The low-impact cleaning methods, particularly the DMSO-based gel and BioTersus^®, effectively remove biodeteriogens from peperino stone while preserving its integrity, offering sustainable solutions for cultural heritage conservation. The instrumental analyses showed that reflectance spectroradiometry and LIF effectively validated the cleaning efficacy, albeit with different sensibility, while HMI, despite spatial constraints, confirmed the three tested cleaning methods do not interfere with peperino stone. Full article

The biodeterioration process involves the alteration of stone monuments by living organisms, such as bacteria, algae, fungi, lichens, mosses, ferns, and vascular plants, combined with abiotic factors, resulting in physical and chemical damage to historic buildings. This study aims to investigate the role of the vascular plants affecting four archaeological parks in Campania—Pompeii, Herculaneum, Paestum, and Velia—by analyzing correlations with building materials, exposure, and conservation status. To represent species associations and their coverage percentages at each site, transects of one square meter were employed. The hazard index (HI) was applied to evaluate the impact of the identified biodeteriogens. A total of 117 species were detected across 198 samples collected from the four study sites, with 59 taxa recorded in Pompeii, 56 in Paestum, 41 in Velia, and 36 in Herculaneum. Specifically, Pompeii hosts a predominance of cosmopolitan species (35%) and widely distributed taxa (15%) due to elevated anthropogenic disturbance. Conversely, mediterranean species dominate in Paestum (62%) and Herculaneum (52%), reflecting more stable ecological conditions. Substrate type significantly influences the hazard index, whereas exposure was found to have minimal impact on both the average coverage and the measured hazard index. Future work will focus on developing site-specific conservation strategies that consider substrate properties, vegetation impact, and anthropogenic disturbances to effectively mitigate the biodeterioration risks posed by vascular flora in Italian monumental sites. Full article

Condition surveys are an important part of the whole scientific research of torso buildings, which we understand to be buildings with usually missing roofs, wooden ceilings, doors, windows, and other envelope constructions along with damaged internal and external infrastructure and surfaces. The aim of the processed condition surveys is to gather basic data on the technical state of the buildings. Torso buildings are, in our environment, especially the ruins of castles and manor houses, but also some churches, the remains of industrial enterprises, or even others. The proposed condition surveys can be used at any of them, not only in our country, but also in any other country of the world. The processed system of condition surveys allows us to anticipate further damage to architectural heritage buildings caused by their aging. It can contribute in a major way to the identification of eventual construction risks and to anticipate them. Condition surveys are designed as a quick, cheap, and easy to handle way to gather the basic overview needed for undertaking a basic stabilization of the most endangered parts of the ruins. In the next step, further scientific research using instruments i.e., in laboratories, can be undertaken. It is also important to know which parts of the torso buildings are dangerous and can endanger not only visitors, but also scientists realizing research on site. The first goal of the project focused on bettering of the stability of the torso buildings, especially ruins of castles, which was granted by the Slovak Ministry of Culture to elaborate and prepare a system for the identification of the most endangered parts of the ruins, which are in danger of dilapidation soon. The second goal was focused on preparing source material for further scientific research of the torso architecture. Experts from the Faculty of Civil Engineering of the Slovak University of Technology, with the cooperation of experts from praxis and from the Architectural Heritage Protection Office prepared a system for judging the construction details of torso buildings from the point of view of their construction–technical state. The aim of this judging lies in identifying the parts of their constructions that are most endangered by decay. Based on the condition survey results, conservation activities can be organized to save valuable details of the torso buildings before destruction and to protect the visitors of such localities before injuries, maybe even tragic injuries. Full article

The deterioration of stone heritage in urban environments is mainly the product of sources of air pollution like vehicular traffic and domestic heating. The results of these phenomena usually manifest as acid rain and particulate patinas, acting on the surface of stone monuments to form the so-called “black crusts”, a typical stone degradation product, mainly composed of gypsum. The aims of this study were to investigate the extent of these phenomena on the decorative apparatus of the frontal façade of Gesù Nuovo Church, in the historical centre of Naples (Italy). Preliminary diagnostics consisted of XRD and FTIR to analyse the composition of stone materials and inquire about previous restorations. The chemical characterization of black crusts was performed, using a diverse array of techniques, to highlight how different compounds are distributed along a vertical gradient and considering the proximity of specific sources of pollution (vehicle engine ignition, incense combustion, domestic heating products). Finally, molecular biology techniques were employed to identify the organisms which typically dwell in this formation and speculate about their contribution to the degradation of stone. Full article

The colonization of historical buildings and monuments by fungi, algae, and bacteria is a common phenomenon. This often leads to deterioration processes that cause either visual or structural harm. The Batalha Monastery in Portugal, a UNESCO World Heritage Site, currently shows significant surface changes to the stone architectural elements within both the Founder’s Chapel and the church, including a widespread pink discoloration on the walls and columns. The main goal of this study was to analyze the biological colonization and assess the influence of bacterial communities on the biodeterioration of Ançã limestone, providing valuable insights to help conservators and restorers select the best preservation strategies for the monastery. The prokaryote population was characterized using both high-throughput DNA sequencing and culture-dependent methods and several orange-pink pigment-producing bacteria were identified, for example, Bacillus, Gordonia, Serratia and Methylobacterium, as well as Halalkalicoccus, an abundant archaeal genus. The pink discoloration observed could be due to biofilms created by bacteria that produce pigments, namely carotenoids. Biocolonization tests were performed using stone mock-ups, which were prepared and inoculated with the bacteria isolated in this study. These tests were designed to replicate the natural conditions of the monastery and monitor the colonization process to understand the discoloration phenomenon. Full article

Calcareous stones, such as marble and limestone, have been widely used in ancient architecture due to their durability, abundance, and ease of extraction and workability. However, their chemical nature renders them vulnerable to atmospheric pollutants. With industrialization and socio-economic growth, air pollution has severely impacted built heritage, including numerous historical buildings and monuments, particularly under changing climate and environmental conditions. Various forms of degradation, such as acid corrosion, mineral crystallization, and black crusts, are widespread and typically driven by atmospheric pollutants like sulfur dioxide (SO₂), nitrogen oxides (NO_X), ozone (O₃), and particulates (PM), which accelerate the deterioration of stone surfaces. To develop sustainable mitigation strategies, it is essential to gain an in-depth understanding of these deterioration mechanisms and current technological advancements. This paper first reviews the influencing factors and underlying mechanisms of atmospheric deterioration of calcareous stones. Subsequently, it discusses the advantages and limitations of traditional and advanced conservation and restoration techniques at the micro-level, as well as pollution management strategies that can be adopted. Finally, the challenges of research in this field are highlighted, and directions for the sustainable conservation of calcareous stones are proposed. Full article