Papers by António Santos Silva
Revista IBRACON de Estruturas e Materiais, 2016
Several cases of alkali-silica reaction involving granitic aggregates have been diagnosed in dama... more Several cases of alkali-silica reaction involving granitic aggregates have been diagnosed in damaged concrete structures in Portugal. Nonetheless, this kind of rock is usually regarded as slow/late reactive or even non-reactive to alkalis. Granitic rocks are widely exploited in Northern and Central Portugal, representing almost half of the produced aggregates in this country. Project IMPROVE rose from the need to accurately diagnose the potential reactivity of granites to alkalis. The study involved about forty granites collected from different regions in Portugal, from which the results of eight samples are being presented in this paper. The tests carried out include the petrographic analyses of the aggregates and mortar and concrete expansion tests. It was concluded that the content of microcrystalline quartz correlates better with the results of AAR-4.1 than with the other expansion tests.
Cleaner Engineering and Technology
Revista Eletrônica em Gestão, Educação e Tecnologia Ambiental
The mixture of mortars with quartzite residues is a recycling technique that has been widely used... more The mixture of mortars with quartzite residues is a recycling technique that has been widely used to promote the adequate management of solid waste generated in the municipality of Várzea-PB, Brazil. However, there are no reports in the literature that prove the durability of the mortar mixed with these residues when subjected to environmental conditions over time. Thus, the present work has as objective to study the durability of mortars incorporated with quartzite residues when submitted to natural aging. The reference mortar and incorporated with quartzite were prepared according to NBR 13281 and submitted to natural aging for 28, 60, 120, 180 and 360 days. Then, they were characterized by x-ray diffraction, thermogravimetric analysis and simple compression strength and carbonation and pozzolanic measurements. The results showed that, despite the decrease in compressive strength of quartzite containing mortars, the durability was not compromised, since the values were maintained...
Construction and Building Materials
International Journal of Architectural Heritage
Construction and Building Materials
Journal of Materials in Civil Engineering
Journal of Cultural Heritage
Conservar Património
Arquitectónico, estudaram-se algumas argamassas do conjunto monumental do Castelo de Viana do Ale... more Arquitectónico, estudaram-se algumas argamassas do conjunto monumental do Castelo de Viana do Alentejo, com vista a servir de suporte técnico e científico nos trabalhos de conservação/recuperação em curso no monumento. Este estudo consistiu na caracterização microquímica e minero-petrográfica das argamassas recolhidas na Igreja da Misericórdia e na Igreja Matriz recorrendo às técnicas de difracção de raios X (XRD), análise termogravimétrica e térmica diferencial (TG-DTA), microscopia electrónica de varrimento acoplada a espectroscopia de raios X dispersiva de energia (SEM-EDS) e microscopia óptica. Os resultados permitiram verificar que as argamassas antigas existentes são de cal aérea e que na sua formulação foram utilizados dois tipos de agregados distintos. Por um lado, agregados de composição muito uniforme, idêntica à dos granodioritos da região e compostos essencialmente por feldspatos, quartzo e biotite e, por outro, agregados de composição heterogénea compostos por minerais de origem magmática (quartzo e feldspato) e rochas metamórficas (xistos e calcário), provavelmente provenientes de areia de rio. Não se detectou a existência de pozolanas. Pela análise dos resultados foi possível reconstituir o traço actual das argamassas existentes.
Construction and Building Materials
One of the most typical Portuguese facades' coatings is the glazed tile (azulejo) wall coating. A... more One of the most typical Portuguese facades' coatings is the glazed tile (azulejo) wall coating. Azulejos are in Portuguese history for six centuries, being considered a historical heritage and a mark of Portuguese culture. The setting mortar used in the azulejos application plays an important role for the correct functioning of the entire coating system. Therefore, for correct conservation its study and well detailed characterisation are fundamental. Within the scope of DB-HERITAGE project (Database of building materials with historical and heritage interest), a deep gathering of data from literature, concerning the characteristics of azulejos' setting mortars, from the 16th to the 20th centuries, was made. Adding to the existing data, a physical, mechanical, chemical and mineralogical characterisation of a set of azulejos´ setting mortars, from the 16 th to the 19 th century, from Lisbon and Coimbra cities, was carried out. The results obtained in the experimental study were analysed and compared with the ones gathered from literature leading to establish useful conclusions for the prescription of future conservation interventions for this type of coating.
Construction and Building Materials
Construction and Building Materials, 2017
Microscopy and Microanalysis, 2016
In this paper the characterization of a gypsum plaster sample from the end of the 19th century si... more In this paper the characterization of a gypsum plaster sample from the end of the 19th century simulating imperial red porphyry using a multi-analytical approach is presented and discussed. The results of X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TGA-DTA), physical and mechanical properties are summarized. In order to have further insight into the microstructure, polarized light microscopy (PLM), scanning electron microscopy coupled with energy dispersive X-ray spectrometer (SEM-EDS), and micro Raman spectroscopy analyzes were also made. They helped to clarify the main issues raised by the other complementary analytical techniques and allowed the establishment of interrelations between the different properties, providing important information about the materials, the skills, and the technological development involved in the art of imitating noble stones with gypsum pastes. This study also contributes to our knowledge concerning the preservation of...
Applied Physics A, 2016
The potentialities of nanomaterials for application in the field of conservation have been widely... more The potentialities of nanomaterials for application in the field of conservation have been widely investigated in the last two decades. Among nanomaterials, nanolimes, i.e., dispersions of lime nanoparticles in alcohols are promising consolidating products for calcareous materials. Nanolimes are effective in recovering the very superficial loss of cohesion of decayed materials, but they do not always provide sufficient mass consolidation. This limitation is mainly related to the deposition of the nanoparticles nearby the surface of the material. Experimental research has been set up with the aim of improving the in-depth deposition of lime nanoparticles. Previous research by the authors has shown that nanolime deposition within a substrate can be controlled by adapting the nanolimes properties (kinetic stability and evaporation rate) to the moisture transport behavior of the substrate. Nanolime properties can be modified by the use of different solvents. In this research, nanolime dispersions have been further optimized for application on Maastricht limestone, a coarse porous limestone. Firstly, nanolimes were synthesized and dispersed in ethanol and/or water, both pure and mixed in different percentages. Subsequently, based on the kinetic stability of the nanolime dispersions, the most promising solvent mixtures were selected and applied on the limestone. The deposition of lime nanoparticles within the limestone was studied by phenolphthalein test, optical microscopy and scanning electron microscopy. The results confirm that nanolime dispersed in a mixture of ethanol (95 %) and water (5 %) can guarantee a better nanoparticles in-depth deposition within coarse porous substrates, when compared to dispersions in pure ethanol.
Conservar Património, 2016
The Fundação Ricardo Espírito Santo Silva (FRESS) has the mission of defend, train, study, develo... more The Fundação Ricardo Espírito Santo Silva (FRESS) has the mission of defend, train, study, develop and implement Portuguese Fine Arts in Portugal. This paper reflects the process of Conservation-Restoration training, where students apply the most recent analytical techniques to the characterization of artwork towards enabling and supporting conservation intervention. In this study, the materials used to produce a 19th century sedan chair were characterised by optical microscopy, spectroscopic (SEM-EDS, μ-Raman and FTIR-imaging) and chromatographic (HPLC-DAD/MS) techniques. The use of natural and synthetic dyes was identified in textiles found inside the chair, including cochineal, brazilwood and fuchsine. Several paint layers with different colours and compounds, such as barite, calcium carbonate, lead white, hematite and Prussian blue, were identified in the external painted wood surface of the chair. The variety of identified materials, interspersed between layers of animal glue, reflects the different interventions that took place on the chair over time, supporting the intervention strategies reported/prescribed for the conservation-restoration procedure.
Cement and Concrete Research, 2016
Granite is one of the most commonly employed materials in the production of aggregates for concre... more Granite is one of the most commonly employed materials in the production of aggregates for concrete, and represents 40% of the total volume of aggregates produced in Portugal. This type of rock is traditionally considered as slowly/late reactive or even non-reactive to alkalis. However, a number of cases of damaged concrete structures in Portugal, due to alkali–silica reaction, have been related to granitic aggregates. A research program has been developed in order to define the best test method for evaluating the potential alkali-reactivity of granitic rocks. The present study involved thirteen granites collected from different quarries. The tests carried out included: petrographic examination of the aggregate, as well as mortar and concrete expansion tests. It was concluded that the content of microcrystalline quartz correlates better with the results of concrete prism expansion tests than with the mortar-bar expansion test.
Key Engineering Materials, 2016
Clayish earth-based mortars can be considered eco-efficient products for indoor plastering since ... more Clayish earth-based mortars can be considered eco-efficient products for indoor plastering since they can contribute to improve important aspects of building performance and sustainability. Apart from being products with low embodied energy when compared to other types of mortars used for interior plastering, mainly due to the use raw clay as natural binder, earth-based plasters may give a significant contribution for health and comfort of inhabitants. Due to high hygroscopicity of clay minerals, earth-based mortars present a high adsorption and desorption capacity, particularly when compared to other type of mortars for interior plastering. This capacity allows earth-based plasters to act as a moisture buffer, balancing the relative humidity of the indoor environment and, simultaneously, acting as a passive removal material, improving air quality. Therefore, earth-based plasters may also passively promote the energy efficiency of buildings, since they may contribute to decreasing t...
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, Jan 23, 2015
This paper intends to analyze the microstructure of concrete with recycled aggregates (RA) from c... more This paper intends to analyze the microstructure of concrete with recycled aggregates (RA) from construction and demolition waste from various Portuguese recycling plants. To that effect, several scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed. Various concrete mixes were evaluated in order to analyze the influence of the RA's collection point and consequently of their composition on the mixes' characteristics. Afterward all the mixes were subjected to the capillary water absorption test in order to quantitatively evaluate their porosity. Results from the SEM/EDS analysis were compared with those from capillary water absorption test. The SEM/EDS analysis showed that the bond capacity of aggregates to the new cement paste is greatly influenced by the RA's nature. On the other hand, there was an increase in porosity with the incorporation of RA.
Alkali-silica reaction (ASR) is one of the chemical degradation causes of concrete with mineral a... more Alkali-silica reaction (ASR) is one of the chemical degradation causes of concrete with mineral aggregates (CMA). These reactions are included among the internal expansive reactions and occur in the simultaneous presence of high amounts of alkalis, reactive aggregates and humidity. During the reaction a silica-alkaline gel is developed that expands in the presence of humidity leading to various phenomena within the concrete that condition and change its properties. Research in this area has tried mostly to understand the expansive mechanism and the methodologies for its prevention and mitigation. The incorporation of recycled aggregates (RA) in concrete, namely those from crushed concrete, as a complement to mineral aggregates (MA) leads to some questions related to its durability. In order to know the CRA in the same areas as the CMA it is necessary to study the possible causes of their degradation. The theme of the research work presented in this paper was triggered by the possible occurrence of ASR in CRA and its manifestation perhaps being a consequence of the potential reactivity of the RA from the original crushed concrete. An experimental campaign on ASR in CRA is presently being developed in order to un
Uploads
Papers by António Santos Silva