L. Aires-Barros’s research while affiliated with Instituto Superior de Contabilidade e Administração de Lisboa and other places

Salt weathering is one of the main processes affecting rock materials applied in the built environment. Scanning electron microscopy (SEM) studies can contribute to the understanding of the susceptibility of petrographic features of rocks to salt weathering. SEM studies were performed in limestones (grainstones with the commercial designations of Semi-rijo and Moca Creme and a travertine) submitted to salt weathering tests (EN 12370 using sodium sulphate solutions and cubic specimens) consisting of 15 cycles of immersion/drying followed by water washing after the 15th cycle. Fragments from small cubes of the grainstones subjected to salt weathering cycles without the final water cleaning were also studied. SEM observation before and after the tests allows the discussion of the petrographical characteristics of these rocks that contribute to erosive decay under salt weathering. In the case of the grainstones specimens the texture can be described in general as allochemical particles cemented by sparry calcite (Figure 1 a) and it is visible from the preparation of the polished surfaces the interface between the sparry cement and the allochemical components. After the salt weathering tests, SEM studies show (Figure 1 b) extensive fissuring in the sparry cement and separation between grains and sparry cement. Observations of disaggregation products showed an important amount of apparently intact grains. These results are similar to those observed by with the sparry cement being affect by salt crystallisation and lesser impact on the grains. Studies in the unwashed specimens showed the presence of sodium sulphate in the interface between allochemical grains and the sparry cement (Figure 1 c,d). Travertine specimens show heterogeneous patterns of erosion attributed to the heterogeneous texture of this rock, with more terrigenous (especially clay-rich) portions that favour a higher erosive susceptibility and the presence of clays has been frequently connected with salt weathering susceptibility in limestones. In Figure 1e can be observed the heterogeneity of a polished surface, with the more irregular portions showing a chemical spectra (Figure 1 f) indicative of the terrigenous component and the presence of sodium and sulphate (resulting from the solutions used in these weathering tests). The authors acknowledge the support of the Fundação para a Ciência e Tecnologia (POCTI/CTA/44940/2002; PEst-OE/CTE/UI0697/2011 and Pest-OE/CTE/UI0098/2011, funding by the European Union and national budget of the Portuguese Republic). Acknowledgments to Eng. Teresa Luís, Eng. Sónia Pereira and Enterprise Mármores Galrão for the rock blocks.

Exposed stone surfaces containing complex systems of pores, fractures and grain boundaries provide the surfaces where chemical, physical and biological deterioration processes take place. The pore space represents the preferred area for physical, chemical and biological weathering processes. It plays a significant role in the behaviour of porous materials. A full understanding of pore-channel network morphology, size and connectivity is important in stone decay assessment and conservation works. A contribution to the understanding of the role played by the pore system in controlling fluid-related properties and resistance to salt crystallization of limestones is presented. Optical microscopy, scanning electron microscopy (SEM) and mercury injection porosimetry (MIP) were used to characterize the pore structure of two Portuguese dimension stones ('Semi-rijo' and 'Moca-Creme') widely used for pavements and the cladding of buildings. Fluid migration physical tests (open and free porosity, capillary imbibition, and Hirschwald coefficient) were also performed, according to European (EN 1925:1999; EN 1936:1999) and French (N FB 10-504:1973) Standards. The resistance to salt crystallization was determined using European Standard EN 12370:1999. An integrated analysis facilitated comparison between durability results with stone pore network characteristics, fluid transport properties and petrographical features, suggesting the influence of available porosity and bedding.

A study of the different building campaigns, restoration works, pathologies and stones used through time in the Church of Santa Engracia (Portuguese National Pantheon) is presented. The changing fortunes of the monument make it a useful case study in terms of building stone use and decay. This bold baroque project, begun in the seventeenth century, remained without a roof until the 1960s. At that time the leader of the conservative regime of Estado Novo ('New State'), Antonio de Oliveira Salazar, decided to complete the building as a national pantheon to provide a memorial to some of the personalities of Portuguese history. A complementary approach between the geosciences and history of art identified the ancient and more recent quarries, and the main stone types, used during its different building campaigns and restoration/conservation works. The local stone variety 'lioz', extracted in the area around Lisbon, was the main type used. An overview of the current knowledge of the chemical, physical and mechanical characteristics of these stones is now available. Besides new data on the typology, causes and processes of the major weathering forms observed inside and outside the building, the building campaigns and restoration works are also presented.

The aim of this study was an evaluation of the harmful effects of aerosols used for graffiti upon cultural heritage made of stone. Two types of Portuguese calcareous stone were studied, a marble, Branco, and a limestone, Lioz. These are the most common materials used for statues in public areas in the city of Lisbon. Samples were collected from quarries at Estremoz and Pêro Pinheiro areas. Two sets of parallel studies were conducted, namely on sound and on artificially weathered samples. Graffiti were simulated using alkyd resin aerosols, with different colours. The harmfulness was assessed in relation to the variation of water vapour permeability, static contact angle, water microdrop absorption, chromatic changes and contact roughness. Scanning Electron Microscopy was used to study the degree of the aerosol’s penetration into the stone and the morphological surface changes. The results obtained showed that the alkyd aerosols introduced significant changes in water vapour permeability, water repellence and surface morphology, for both types of stone.

This paper presents a study of stone decay on the Basilica da Estrela, the most famous 18th century monument in the city of Lisbon, Portugal. It was built with Jurassic and Cretaceous limestones from the surroundings of Lisbon. Different approaches were used to establish the typology, causes and processes of the major weathering forms. Limestone samples from ancient quarries, salt efflorescences and disintegrated stone material from the interior of the church were characterized by chemical, mineralogical and petrographical analyses. Limestone physical properties related to fluid percolation were also determined. Detailed surveys of stone decay phenomena were carried out on the monument. Textures of grey-level images representative of the weathering forms were analysed by image analysis through covariance and granulometry operators. An HIDSPEC computational hydrogeochemical model, phase and graphical diagrams, and multivariate statistical analysis were used for water-rock interaction studies. Physical weathering forms prevail inside the church. The yellow Cretaceous limestone is the most deteriorated stone. This observation compares well with its intrinsic properties. The weathering is determined by the stone structures, such as stilolytes and fossils, and architectural features (geometry and surface finish). Soluble salts such as trona and thenardite were only found in a very small area inside the church.

The present article intends to gather the available information about consolidants and water repellents, which were applied in restoration campaigns in Portuguese monuments.The survey was based on documents from the ex-DGEMN (General Directorate for National Buildings and Monuments) and ex-IPPAR (Portuguese Institute for Architectonic Heritage) archives, concerning the period between 1952 and 2002. It was noticed that in 30% of the interventions the information about the used product was lacking and from the other cases, only in the most recent interventions rigorous documentation was found. Results also show a generalised used of alkoxysilanes. Owing to the importance of documentation past restoration interventions, a data-sheet for documenting the use of consolidants and water repellents is proposed.

Geochemical and isotopic studies have been undertaken to assess the origin of CO2-rich waters issuing in the northern part of Portugal. These solutions are hot (76°C) to cold (17°C) Na–HCO3 mineral waters. The δ2H and δ18O signatures of the mineral waters reflect the influence of altitude on meteoric recharge. The lack of an 18O-shift indicates there has been no high temperature water–rock interaction at depth, corroborating the results of several chemical geothermometers (reservoir temperature of about 120°C). The low 14C activity (up to 9.9 pmC) measured in some of the cold CO2-rich mineral waters (total dissolved inorganic carbon) is incompatible with the presence of 3H (from 1.7 to 4.1 TU) in those waters, which indicates relatively short subsurface circulation times. The δ13C values of CO2 gas and dissolved inorganic carbon range between −6‰ and −1‰ versus Vienna-Peedee Belemnite, indicating that the total carbon in the recharge waters is being diluted by larger quantities of CO2 (14C-free) introduced from deep-seated (upper mantle) sources, masking the 14C-dating values. The differences in the 87Sr/86Sr ratios of the studied thermal and mineral waters seem to be caused by water–rock interaction with different granitic rocks. Chlorine isotope signatures (−0.4‰ < δ37Cl < +0.4‰ versus standard mean ocean chloride) indicate that Cl in these waters could be derived from mixing of a small amount of igneous Cl from leaching of granitic rocks.

The fracture and failure of natural building stones has been for many years the concern of the engineering community and particularly the c- munity of scientists working for the restoration and conservation of stone monuments. The need to protect the authentic stone and the requirement for reversibility of the interventions rendered the in-depth knowledge of the mechanical behaviour of both the authentic material and its substitutes - dispensable. This book contains 36 papers presented at the Symposium on “Fracture and Failure of Natural Building Stones” which was organized in the frame of the “16th European Conference on Fracture (ECF16)”. The Conference took place in Alexandroupolis, Hellas on July 3-7, 2006. To the editor's best knowledge this is the first time that a special Symposium of a European Conference on Fracture is devoted exclusively to the study of the fracture and failure of building stones. The book consists of invited papers written by leading experts in the field. It contains original contributions concerning the latest developments in the fracture and failure of the natural building stones and their application in the restoration of ancient monuments. It covers a wide range of subjects, including purely mechanical aspects, physico-chemical approaches, applications and case studies. The papers are arranged in two parts with a total of nine chapters. Part I is devoted to purely mechanical and structural aspects and applications, while Part II is devoted to the physico-chemical and environmental aspects including thermal effects.