
António Santos SilvaNational Laboratory for Civil Engineering | LNEC · Department of Materials
António Santos Silva
PhD in Civil Engineering / Degree in Technological Chemistry
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265
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Introduction
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January 1992 - present
Publications
Publications (265)
In the last decades, a significant number of large concrete infrastructures with deterioration problems related to alkali-silica reaction and delayed ettringite formation have been identified worldwide. Currently, due to phenomenological and assessment complexities, it is still difficult to provide recommendations for preventing ASR damage in new s...
In order to revitalize and preserve the Paimogo Fort, a Portuguese coastline military fortification built in 1674 and classified as of public interest since 1957, several lime-based repair rendering mortars were developed, considering the compatibility requirements with the original ones. In this investigation, the different lime-based mortar compo...
Earth plasters have several advantages. Nevertheless, they are vulnerable when in contact with liquid water. For that reason, they have low durability when applied as an outdoor coating or in indoor areas with potential contact with water. In this study, the influence of six different surface treatments (traditional and innovative, based on raw mat...
The cement industry significantly contributes to global CO2 emissions, posing several challenges for a future low-carbon economy. In order to achieve the target established by the European Sustainable Development Goals of reaching carbon neutrality by 2050, the European Cement Association (Cembureau) has devised a comprehensive roadmap based on fiv...
In order to revitalize and preserve the Paimogo Fort, a Portuguese coastline military fortification built in 1674 and classified of public interest since 1957, several lime-based repair rendering mortars were developed, considering the compatibility requirements with the pre-existing ones. In this investigation the different lime-based mortars comp...
Mortars are among the most important materials in building construction. They are generally obtained by mixing aggregates with an inorganic binder. The identification of mortar constituents , particularly the binder type in historic buildings, is one of the essential aspects of building conservation, considering that the new conservation materials...
IMPROVE Project (2012-2015) is aimed at studying the alkali-reactivity of Portuguese aggregates, including innocuous, slowly-reactive and normally-reactive aggregates collected all over the country. The granitic samples were the most numerous, considering the fact that several important concrete structures have been constructed with these aggregate...
Cementitious materials can capture CO2 through carbonation reaction during their service life and post-demolition. Indeed, construction and demolition waste (CDW) still have some potential for carbonation as they contain concrete and cement-based mortars. This research consists of an experimental programme to evaluate the CO2 capture of recycling a...
Cow dung (CD) is a material that has been used for millennia by humanity as a stabilizer in earth building techniques in vernacular architecture. However, this stabilization has been little addressed scientifically. In this study, the effect of CD additions was assessed on earth mortars produced with one type of earth from Brazil and two other type...
The use of thermal insulation materials in the opaque walls is one of the best strategies toward the improvement of the thermal performance of the building envelope, thereby contributing to increase the energy efficiency of the built environment. In this context, an increasing number of studies are focusing on the development of mortars with enhanc...
The most common standards ruling the assessment of the potential reactivity of aggregates consider that the petrographic analysis should be followed, in the first step, by accelerated mortar-bar tests and, in case of a positive result, by concrete-prism tests.
However, experience has shown that these different approaches often provide contradictor...
This work presents a methodology, involving a highly interdisciplinary team, for documenting, assessing, and monitoring the azulejo heritage with a special focus on its degradation. The azulejos of the façade of LNEC Congress Centre are used to exemplify some results of the proposed methodology. METODOLOGY FOR AZULEJO DECAY CONTROL Azulejos are one...
Cementitious materials have a considerable global warming footprint. This is due mainly to
the cement incorporated. For a tonne of cement produced other 800 kg of CO2 [1] are released
into the atmosphere.
According to the European Sustainable Development Goals, cement industry should become
carbon neutral by 2050. To meet this goal, the European...
This paper addresses the study of renders and plasters’ physical and mechanical characteristics from selected buildings awarded during the 20th century with a renowned architectural prize in Lisbon, Portugal. The characterisation was done to understand mortars’ physical and mechanical properties and their evolution during the 20th century. These ch...
This paper reports on the study of renders and plasters from 20th-century award-winning buildings in Lisbon (Portugal) with the Valmor Prize for Architecture. The mortars have been investigated through XRD, optical and electronic microscopy (SEM-EDS), thermal analysis (TGA/DTA), wet chemical analyses and AAS. The results reveal that the use of air...
The Mirante da Quinta da Azeda, in Setúbal (Portugal), is a peculiar observation tower built in the early 20th century, and one of the first examples in which reinforced concrete was applied in Portugal. It has an unusual architectural configuration, displaying elements of great slenderness. In the scope of the CemRestore research project - Mortars...
Earth mortars and gypsum mortars present ecological advantages compared to mortars made with other common binders. When applied as plasters, they are also referred as having advantages in improving comfort and indoor air quality. For earth plasters, this improvement is associated with the hygroscopic capacity of the clay minerals, which promotes hi...
The growing interest in preserving the built heritage is a driving force towards the search for new rehabilitation solutions compatible with the original construction techniques of ancient buildings. For the design of an adequate reinforcement solution, it is necessary to know in detail the building to be rehabilitated, as well as its original cons...
Along the Portuguese coastline, several military fortifications were built with the intention to protect the territory from the constant military threat from the sea. These constructions have been subjected, during centuries, to a very aggressive environment; the renders, whose main function is the protection of walls, are particularly exposed to s...
The popularity of natural cement (Roman cement) in buildings from the late 19th and the beginning of the 20th century and the high diversity of characteristics of natural cement demand research of mortar and binders used in the buildings of this period in Portugal. Understanding the type of binder used in the historic buildings will help the projec...
DB-HERITAGE provides open and free sharing of wide-ranging technical data on hundreds of samples of building materials from diverse periods, extracted from Portuguese built heritage all over the world. It has been developed to improve know-how for historic building materials and as a basis for developing best practices for built heritage conservati...
As part of the Norwegian R&D project “ASR - Reliable concept for performance testing (KPN-ASR)” and of the RILEM TC 258-AAA activities, a study was launched in 2015 with the aim of correlating the results of field and laboratory investigations for selecting appropriate preventive measures against deleterious alkali-silica reaction (ASR) in concrete...
The use of concrete materials in Portugal, namely reinforced concrete, began in the 19th century. However, during the 20th century, the increase in the application of this composite material, alongside the use of hydraulic binders, led to a disruption of traditional construction techniques and enhanced generalized application in concrete structures...
One of the proposed actions to promote sustainable construction is the use of recycled aggregates (RA) as a construction material. The alkali reactivity level of RA raises the alkali-silica reaction (ASR) issue. Due to RA’s composition, well-known changes on concrete properties occur but there are some doubts about its behaviour regarding ASR.
In...
The potential alkali-silica reactivity (ASR) of volcanic aggregates, especially basalts, remains a source of debate in the scientific community. When evaluating the potentially deleterious character of this type of aggregate, different laboratory testing methods may produce contradictory data; this is particularly evident when using the accelerated...
To create an international recommendation concerning the release of alkalis, test method AAR-8 was developed within the scope of RILEM TC 258-AAA activities. The first round robin test was performed using five aggregate types, and further investigation was conducted as RRT2, leading to the final version of the AAR-8 recommendation. Five aggregates...
Um arquivo de materiais de construção com interesse histórico Recolher, registar e sistematizar os dados sobre materiais de construção de interesse histórico e arqueológico revela-se muito importante para a preservação desse património. Estes repositórios atendem às necessidades de conhecimento por parte dos investigadores, mas também permitem obte...
The São João das Areias and Criz II bridges, located in the reservoir of Aguieira Dam, in the centre of Portugal, were affected by internal swelling reactions of concrete, which particularly affected their piers and foundations. Laboratory tests diagnosed both Alkali-Aggregate Reaction and Delayed Ettringite Formation as the causes of those expansi...
The detection of concrete structures affected by Alkali-Silica Reaction (ASR) has increased dramatically over the past couple of decades in Portugal. Due to the complexity and multiplicity of factors involved in ASR together with the variability of the materials used, no International or European standards exist for assessing the aggregates potenti...
This paper aims to provide information on rammed earth and masonry mortars of the Fernandina defensive Wall of Lisbon, Portugal, which was built in the second half of the 14th century. No previous information exists concerning the materials and construction techniques used in this defensive structure, which is essential to increase knowledge and to...
DOSSIER TEMÁTICO
MATERIAIS DE INTERESSE HISTÓRICO QUE CONSTROEM O PATRIMÓNIO EDIFICADO: CORRELAÇÕES, USOS, PAISAGENS - VOL. II
O azulejo e a pedra, entre outros materiais de construção históricos que densificam os lugares, modelando a luz, a cor e a temperatura; projeto como criação da construção, sendo os elementos escritos relatores do seu fio condutor; a evolução do edificado com o gosto e a técnica, ligada aos recursos locais e a apropriação social que é feita do patri...
The test method AAR-8 is intended to be used for assessing the potential amount of alkalis released by aggregates in field concrete in the long-term. This is done by measuring the amounts of sodium and potassium ions released from the fine graded (< 4 mm) aggregate immersed in (0.7 M) KOH and NaOH solutions, respectively, at elevated temperature wh...
Os revestimentos de imitação de pedra em stucco-marmo constituem uma das técnicas decorativas mais representativas do período Barroco na Europa. Em Portugal, entre meados do século XVIII e meados do século XX, a sua utilização foi bastante mais frequente do que se pensava. A falta de informação relativa a estes revestimentos tem posto em perigo a s...
Construction and demolition wastes (CDW) are generated at a large scale and have a diversified potential in the construction sector. The replacement of natural aggregates (NA) with CDW recycled aggregates (RA) in construction materials, such as mortars, has several environmental benefits, such as the reduction in the natural resources used in these...
Alkali-silica reaction (ASR) is considered one of the most concrete degrading agents causing expansion due to a gel formation that swells in contact with water. In this regard, this study investigates ASR through an expansion test of mortars produced with recycled aggregates (RA). The RA were prepared by crushing source concrete (SC) mixes that wer...
The use of secondary mining resources to replace conventional constituents in mortars production has proved the effectiveness to preserve the quality of mechanical, physical, and chemical properties. However, minimal research has been performed to quantify the environmental impacts of mortars with mining residues. In the present work, a life cycle...
Conservation, increasing the useful life period of existing significant buildings with minimum consumption of new materials, as much as possible of low-embodied energy, is an important step towards sustainable rehabilitation, while also contributing to the preservation of the cultural heritage. In the context of 20th-century buildings’ conservation...
European Commission standards for a circular economy are pushing the development of innovative techniques to remove and/or recover elements from environmental matrices. The conception of sustainable strategies should address toxicity issues and potential supplies of secondary materials. Electroremediation of secondary mining resources has been rese...
Selecção de comunicações apresentadas ao ENCORE 2020-4.º Encontro de Conservação e Reabilitação de Edifícios (Lisboa, Nov. 2020). Um convite à reflexão sobre a temática a partir de diferentes perspectivas, considerando o Património arqueológico, tradicional, monumental e contemporâneo. São abordadas metodologias, práticas, materiais, registos e fon...
Neste artigo são abordados materiais de construção cuja aplicação remete para diferentes tempos e usos no património edificado, e que são indissociáveis dos gostos e das influências culturais na arquitetura de cada local. Alguns dos materiais apresentados, como a cal e o gesso, têm um historial de longevidade e durabilidade que é um desafio constan...
O presente número trata do volume 1 de um Dossier temático que, inspirado nos materiais de interesse histórico que constroem o património edificado: correlações, usos, paisagens, apresenta artigos que refletem uma ampla, vasta e diversificada abordagem dos vários aspetos que influenciam a realidade patrimonial e investigativa em torno das nossas ci...
Os materiais constituintes dos edifícios, as suas texturas e cores, o modo como refletem a luz, fazem parte da imagem das cidades, ajudam a construir um ADN próprio. A forma como esses materiais são produzidos e aplicados
é representativa das técnicas e saberes dos seus habitantes, da sua arte e cultura, moldando a arquitetura e a paisagem urbana....
Neste artigo são abordados materiais de construção cuja aplicação remete para diferentes tempos e usos no património edificado, e que são indissociáveis dos gostos e das influências culturais na arquitetura de cada local. Alguns dos materiais apresentados, como a cal e o gesso, têm um historial de longevidade e durabilidade que é um desafio constan...
One of the biggest challenges currently faced by Society is climate change, leading to the need of mitigation of carbon dioxide (CO2) emissions, among other consequences. The construction sector is responsible for a large part of these emissions. In addition, this sector is also responsible for a significant part of all waste globally produced, abo...
Rendering mortars were prepared by replacing conventional sands, namely coarse sand (CS) and fine sand (FS), by different dosages of biomass dry bottom ash (BA) and fly ash (FA). Bottom ash was treated by sieving and washing and called treated bottom ash (TBA). All these ashes were characterized, and their effects on the physical and mechanical cha...
The combination of treatments may improve the extraction of toxic and critical elements from secondary resources, produce changes in materials’ physico-chemical properties and improvements on the sustainability of strategies. Mining residues were treated with an electrodialytic process alone or coupled with a thermal procedure, and reused in cement...
In this paper, the process of design and evaluation of compatible materials to partially or completely substitute damaged interior walls and ceilings coatings made of gypsum-based plasters is presented and the results obtained are discussed.
The methodology used comprised the definition of quantitative requirements to be accomplished by the new mat...
Conservar e Reabilitar monumentos, edifícios e espaços são oportunidades únicas para fomentar a sustentabilidade dos territórios, constituindo-se o ENCORE 2020 - 4º Encontro de Conservação e Reabilitação de Edifícios numa ocasião ímpar para discutir os desafios da transformação no espaço construído: otimizar recursos, reutilizar materiais, melhorar...
Coordenação de número temático sobre Conservação e Reabilitação de Edfícios, com artigos resultantes de comunicações apresentadas ao ENCORE 2020-4.º Encontro de Conservação e Reabilitação de Edifícios (Lisboa, Nov. 2020). Um convite à reflexão sobre a temática a partir de diferentes perspectivas, considerando o Património arqueológico, tradicional,...
The incorporation of recycled aggregate (RA) in structural concrete requires deep knowledge of this material’s potential and limitations by assessing its effect on the concrete properties. Alkali-silica reaction (ASR) is one of the most concerning degradation agents in concrete produced with natural aggregates, and more expectedly in recycled aggre...
It is important to ensure indoor comfort by passive methods, avoiding mechanical equipment that has energy costs. To assess plasters common efficiency but also its contribution as moisture buffers, five different plastering mortars, including unstabilized and stabilized earth-based plasters, gypsum and cement-based pre-mixed plasters, were analyzed...
Mining residues have been accumulated for centuries due to excavation and mining processes, causing environmental degradation worldwide. Their application in cementitious products is a feasible alternative to waste disposal. Electrodialytic technologies can promote a safer reuse of mining residues in the construction sector, coupling economic advan...
CALL FOR PAPERS
The call is now open for the proposal of new papers for the forthcoming number of the academic journal CADERNOS DO ARQUIVO MUNICIPAL. The aim of this journal is to disseminate and publicise the documentation housed at the Lisbon Municipal Archive.
Number 16
Thematic Dossier:
The materials of historical interest that build up the u...
Alkali-silica reaction (ASR) is one of the major degradation causes of concrete. This highly deleterious reaction has aroused the attention of researchers, in order to develop methodologies for its prevention and mitigation, but despite the efforts made, there is still no efficient cure to control its expansive consequences. The incorporation of re...
Exterior old glazed tiled facades have been a very important heritage testimony of Portuguese culture and traditions throughout the years. The adhesion of the mortars to the old tiles is a very important factor in the behavior of the tiled facades. This study performs a mechanical and water behavioral characterization of compatible air lime (AL) mo...
Earth-based plasters can be very eco-efficient both in terms of embodied energy and technical efficiency, although they are vulnerable to water when unstabilized. An experimental campaign was developed to assess the workability and the mechanical properties of formulated earth-based plastering mortars with a 1:3 (illitic clayish earth:aggregate) vo...
The presence of stucco marble in the Portuguese architecture is not surveyed and studies addressing the materials used to produce it are almost inexistent.
In this paper, the results of the multi-analytical characterisation using XRD, SEM-EDS, Py-GC/MS and the determination of capillary water absorption and dynamic modulus of elasticity of 15 sampl...
Resources efficiency regarding the decrease of residues generation and disposal are important steps towards a cleaner production in the construction and mining industry. Minning processes generate huge amounts of residues, and some deposits have accumulated them over hundreds of years, causing environmental and public health problems. However, mini...
Electroremediation and deep eutectic solvents are well-documented clean-up processes for metals extraction from solid matrices. Depending on the purpose, these treatments may generate a residue free of pollutants and critical raw materials. Several studies were conducted to re-insert treated secondary resources in building materials. However, there...
Knowing the aggregates' properties is fundamental for the correct design and performance prediction of concrete. The incorporation of coarse recycled aggregate (CRA) in concrete requires a deep understanding of CRA's capacity and limitations. CRA properties are mainly conditioned by the type of natural aggregates (NA), the interstitial transition z...
The purpose of this work is to assess the influence of the aggregates' properties on the hygric and mechanical behaviour of Portland cement mortars. This assessment allows the establishment of a close relationship between the mortars' performance and its pore size distribution, which is very sensitive to the aggregates' characteristics: It was foun...
This research intends to study and optimize successful preparative strategies of nano to sub-micro limes, and to improve their efficiency in the inhibition of the degradation process and in the consolidation of wall renders. In this article we report the synthesis and characterization of nanoparticles based on alkali-earth metal hydroxides, precise...
Earth-based mortars have been used all over the world since ancient times in an extensive range of building types from vernacular architecture to monuments. Plastering is one of the most common contemporary applications of earth-based mortars used for earthen-building conservation or modern architecture. Raw earth is a very diverse natural material...
Tungsten is a critical raw material for European and U.S. economies. Tungsten mine residues, usually considered an environmental burden due to e.g. arsenic content, are also secondary tungsten resources. The electrodialytic (ED) process and deep eutectic solvents (DES) have been successfully and independently applied for the extraction of metals fr...
O presente livro reúne os resumos das comunicações e respetivas apresentações realizadas no Workshop “Materiais históricos: entre tradição e inovação”, ocorrido em Lisboa, nas instalações do LNEC, no dia 4 de dezembro de 2019. Este Workshop (http://db-heritage.lnec.pt/workshop/index.html) visou proporcionar um campo de reflexão sobre os materiais d...