Isabel Fernandes

University of Lisbon | UL · Departament of Geology

Groundwater flow on fractured rock mass is critical to understand the geotechnical behaviour. Water can influence the strength of the rock material and promote the washing of discontinuities’ filling. It also reduces the friction angle and shear resistance of the rock mass, creating additional pressure on the rock structure. This framework in rock...

Using geotechnical indexes and geomechanical classifications is crucial in estimating the quality and behaviour of fissured rock masses. These tools play a significant role in large-scale engineering works, particularly in underground projects where the rock mass and its response to excavation are critical for project safety and financial feasibili...

This work intends to summarise the principles of geotechnical mapping as one of the fundamental elements in diverse applications, emphasising its use in underground works. This activity is generally integrated into the construction and extractive industry projects and is often the starting point for dimensioning and layout design. Developed and app...

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...

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...

RESUMO A aldeia de Monsanto, no concelho de Idanha-a-Nova, distrito de Castelo Branco, encontra-se edificada sobre um maciço granítico caracterizado por encostas íngremes e por uma paisagem de caos de blocos. Neste tipo de cenário geotécnico, os movimentos de terreno mais frequentes são a queda de blocos e o deslizamento translacional ao longo das...

The alkali-silica reaction (ASR) is a chemical deterioration of concrete that involves reactive forms of silica. Volcanic glass is one of the potentially reactive forms of silica that can be present in volcanic rocks such as basalts. The aggregates used for concrete purposes from the Azores and Hawaiian Archipelagos are mainly of basic composition...

The mechanisms involved in alkali-aggregate reaction and the characteristics of reactivity of some aggregates are not completely understood, although tens of thousands of mortar and concrete prisms have been tested in the laboratory and field exposure sites have been installed in a number of countries. Aggregates are the least well understood compo...

The reactive forms of silica present in an aggregate depend on the origin and geological history of the rocks. The detection of specific reactive silica must be focused on characteristics such as the identification of polymorphs, the quantification of microcrystalline to cryptocrystalline quartz, and/or on the deformation manifestations for each ag...

The stability of slopes and hillsides involving rock or soil masses depends crucially on the occurring geological and geotechnical conditions. The village of Monsanto, municipality of Idanha-a-Nova, is located on a granitic inselberg. The tourist interest of the village lies largely in the fusion of the granitic rock mass with the man-made construc...

RESUMO A estabilidade de taludes e encostas envolvendo maciços rochosos ou terrosos depende de forma determinante das condições geológico-geotécnicas ocorrentes. A aldeia de Monsanto, concelho de Idanha-a-Nova, encontra-se implantada num inselberg granítico. O interesse turístico da aldeia reside em grande medida na fusão do maciço rochoso com as c...

CT156, Geotechnics and civil engineering , has been developing efforts to create standards with the generic designation EN ISO 17892, Geotechnical investigation and testing - Laboratory testing of soil . The recent publication of EN ISO 17892-part 6, Fall Cone Test which describes in detail the use of this test method to estimate the undrained shea...

Alkali-silica reaction (ASR) is a type of deterioration that has been causing serious expansion, cracking and durability/operational issues in concrete structures worldwide. The presence of sufficient moisture, high alkali content in the cement paste and reactive forms of silica in the aggregates are the required conditions for this reaction to occ...

Several concrete structures show signs of deterioration resulting from internal chemical reactions, such as the alkali-silica reaction (ASR). It is well known that these swelling reactions occur in the presence of moisture, between some silica mineral phases present in the aggregates and the alkalis of the concrete, leading to the degradation of co...

Several concrete structures had shown signs of degradation some years after construction due to internal expansive reactions. Among these reactions there are the alkali-aggregate reactions (AAR) that occur between the aggregates and the concrete interstitial fluids which can be divided in two types: the alkali-silica reaction (ASR) and alkali-carbo...

In the context of European Conformity (CE marking), an inventory on the aggregates used in road construction in Portugal, encompassing 145 producers (68%) and 228 production centres (79%) was carried out, aiming to support the normalisation of activity for aggregates. A broad and representative characterisation of the geometric, physical, mechanica...

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,...

At Serra do Vidual, Pampilhosa da Serra, Portugal, the Ordovician is mainly represented by quartzite rocks disposed in sub-vertical beds, which often alternate with quartz-mica schists. The unit has two main foliations, of which the dominant is close to N40ºW and dipping 60-70º NE, rarely vertical. In addition to the regional and local faults N40-5...

The alkali-aggregate reaction comprises the alkali-silica reaction (ASR) and the alkali-carbonate reaction (ACR). Reaction kinetics of the ASR depends on the grain size and crystalline structure of the reactive silicon dioxide. The reaction starts in the aggregates along the particle periphery and progresses inward. After cracking of the particle,...

The identification of alkali-reactive aggregates has been a challenge since alkali-aggregate reactions were first diagnosed. Standards, test methods and recommendations have been developed on a local and international basis. The Rilem recommendations regarding alkali-aggregate reactions are based on a methodology in which a series of laboratory tes...

Identifying which component of a rock is the cause of its reactivity is neither well understood nor evident for many types of rocks.

Sedimentary rocks form from deposition and consolidation of older rock and mineral materials near or at the Earth’s surface in atmosphere or underwater, normally deposited in horizontal layers. The composing materials may have different sources: (1) lithic or mineral detritus from natural breakdown of pre-existing rocks (igneous, sedimentary or met...

Metamorphic rocks form from prograde or retrograde recrystallization of igneous, sedimentary, or metamorphic precursor rocks, variously changing mineral content, structure, and texture/fabric. Metamorphic rocks may be formed from shallow depth near the Earth’s surface to great depth down in the mantle. Weathering and alteration at (near) surface co...

Features of ASR are presented in the following pages. All the images collected were obtained from the concrete thin sections studied. From the observation of the concrete thin sections, it was concluded that the manifestations of ASR are usually quite discrete in concrete prisms tested under laboratory conditions. In these, cracks are visible only...

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...

This RILEM AAR 1.2 Atlas is complementary to the petrographic method described in RILEM AAR 1.1. It is designed and intended to assist in the identification of alkali-reactive rock types in concrete aggregate by thin-section petrography. Additional issues include: • optical thin-section petrography conforming to RILEM AAR 1.1 is considered the pri...

Igneous rocks form from cooling and solidification of molten rock, either from magma within the Earth’s crust (plutonic rocks), or from lava extruded on to the Earth’s surface in the atmosphere or underwater (volcanic rocks).

Resumo Apresentam-se e discutem-se os resultados obtidos na caraterização de rochas xistosas de duas áreas: Estrada Nacional 17 (EN17), em Coimbra, e Vila Velha de Ródão. A caraterização foi adaptada ao tipo de amostras tendo sido realizados ensaios de propriedades índice e a determinação de propriedades mecânicas e de durabilidade. Os resultados m...

Alkali-silica reaction is a mechanism of deterioration of concrete structures which is associated with the composition of the rocks used as aggregates. The assessment of aggregates to evaluate their potential reactivity to alkalis is made both by visual methods and laboratory expansion tests. There are a number of national standards regarding the p...

In Portugal, volcanic rocks are commonly used as concrete aggregates for concrete in Madeira and Azores Islands and in a lesser extent in the Mainland. Nonetheless, the information about the potential alkali-silica reactivity of Portuguese volcanic rocks is rather scarce. In order to fulfill this lack of information and in the scope of a Portuguese...

The study of metasedimentary rocks using laboratory test methods is presented. Field work revealed a highly weathered yellowish metasedimentary quartz-pelitic rock characterized by very close discontinuities. The Schmidt hardness values obtained at an excavated slope were low. The rock mass was studied in depth for the excavation of a tunnel with t...

Aiming to know the characteristics of the aggregates produced in Portugal, the 200 producers who in October 2008 had completed the certification process of the CE conformity were contacted. A questionnaire was sent to all, requesting also the CE marking of documents, including certificates, declarations of conformity and technical data sheets, as w...

The deterioration of concrete can be caused by different processes. Alkali-aggregate reactions are some of the most widely known modes of chemical deterioration, usually involving reactive forms of silica in the aggregates. The reaction produces an alkali-silica gel, which expands and creates a framework of cracks in the concrete. Samples of mafic...

To evaluate whether the framework of European standards, regarding the grading requirements, is adjusted to be used in the compaction control of unbound limestone materials for base and sub-base layers of road pavements a laboratory test program was envisaged. According to the Portuguese practice, two distinct approaches are used. An approach takes...

Concrete swelling processes are one of the main degradation mechanisms of hydro concrete structures, such as dams. Included in this degradation phenomenon, the reactions that involve the aggregates when exposed to the alkali rich environment of the cement paste are probably the ones that deserve more concern worldwide. The alkali concentration of t...

The first case of alkali-silica reaction (ASR) in Portugal was reported in a dam in the 1990s, mainly associated to the presence of slowly reactive aggregates of granitic composition. In the following decades several other structures were diagnosed as being affected by ASR due to the use of alkali reactive aggregates. This situation led to develop...

Many geoscience fieldworks are not aligned with the curriculum contents reflecting the need to develop more research related to the outdoor learning environment. The purpose of the study was to verify if a fieldwork organized in accordance with Orion’s model (1993), could be assumed as an integral part of formal school science curricula. A fieldwor...

Problem-Based Learning, a methodology that builds on problems to develop students’ new knowledge, can also be useful in helping students to learn Nature of Science. Prospective science teachers’ conceptions regarding Nature of Science and its teaching through Problem-Based Learning were analyzed by applying a semi-structured interview. Nine respond...

The action of the geodynamic agents (external and/or internal), or even the human activities, can cause changes in the structure of a slope that may result in an imbalance between the internal and the external forces acting on the ground. The aim of this study is the analysis of the stability of a natural rock slope located along the Távora river,...

The results obtained in the characterization of schist rocks from two distant areas in Portugal are presented: black shales of the road EN17 in Coimbra and phyllites of Vila Velha de Ródão (VVR). At EN17 the shale is exposed on excavation slopes, while in VVR the phyllites belong to a rock mass where an underground excavation is planned. The charac...

Alkali-silica reactions have caused serious expansion and cracking in concrete structures worldwide. Volcanic rocks have been found to be potentially alkali-reactive in a number of countries such as Argentina, Iceland, Japan, New Zealand and Turkey. The Azorean rocks used as aggregates are mainly basalts and some trachytes. The characterization of...

In Portugal, the alkali-silica reaction (ASR) was recognized for the first time in concrete structures in the beginning of the 1990‘s. Since then, a lot of work has been carried out in order to study the concrete aggregates, to prevent the reactions and to monitor and repair the affected structures. The work presented in this paper summarizes the t...

The aim of this study is the analysis of the stability of a natural rock slope located along the Távora river, NW of the village of Távora. The geological mapping of the area and the use of the stereonet to determine the main sets of joints were the starting points for the performed analysis, followed by the kinematic analysis. It was complemented...

Concrete may deteriorate and the reasons for the deterioration can be diverse. Among them there are the alkaliaggregate reactions, which can occur between certain types of aggregates and the cement paste, and which may result in damage to concrete structures. The present work objective was to characterize the reactivity of aggregates of deformed ro...

The application of petrographic techniques to concrete started at the XIX century and it has been developed since then becoming an indispensable tool in the assessment of the potential reactivity of aggregates and in the detection of deterioration signs in concrete structures. The chemical reactions of internal origin, with expansive nature, partic...

Volcanic rocks have been found to be the cause of concrete deterioration in several countries (Argentina, Iceland, Japan, New Zealand and Turkey), due to the occurrence of alkali-silica reactions. Alkali-silica reaction (ASR) is a deterioration phenomenon that occurs between alkaline (Na+ and K+) and hydroxyl (OH-) ions in the cement and certain re...

Volcanic rocks have been found to be potentially alkali-reactive in a number of countries, including Japan, New Zealand, Iceland and Turkey. In order to characterize the potential reactivity of the volcanic rocks in Azores a project is being carried out, under the support of the Azores Government: the ReAVA Project – “Characterization of Potential...

Nas últimas décadas o número de infraestruturas em concreto afetadas por processos expansivos, nomeadamente por reações álcalis-agregado (RAA), tem motivado o desenvolvimento de estudos por todo o mundo. Em Portugal cerca de 30 pontes e grandes barragens encontram-se danificadas por RAA, o que tem obrigado a dispendiosas obras de reparação ou de su...

As rochas graníticas representam em Portugal cerca de 40% do volume total de agregados para concreto. Estas rochas são normalmente consideradas como sendo de reação lenta ou até como não reativas aos álcalis. Contudo, diversos casos de reação álacalis-agregado (RAA) têm sido diagnosticados em estruturas de concreto nas quais foram utilizadas rochas...

Resumo: O betão pode deteriorar-se e as razões para a deterioração podem ser diversas. De entre elas destacam-se as reações álcalis-agregado, que podem ocorrer entre certos tipos de agregados e a pasta de cimento e das quais podem resultar danos nas estruturas de betão. O presente trabalho teve como objetivo a caracterização da reatividade de agreg...

A concrete dam was built on the early 1970s in the Douro River about 70 km from the estuary in the Atlantic Ocean, at Porto city. According to other studies developed in Portugal and some reports in the literature, granitic aggregates can be potentially reactive in concrete. The study of the concrete was, therefore, focused on the assessment of the...

Modern day Portland-cement concrete was for decades considered to be a long lasting material, until in the 1940s it was recognised that concrete could deteriorate as the result of chemical reactions between Portland cement and some components of the aggregates. Research has been undertaken since then in order to find the best test methods for ident...

Alkali–silica reaction (ASR), a deleterious chemical reaction in concrete that involves certain mineral phases in the aggregates and the alkalis from the cement paste, is in the origin of the deterioration of many large structures such as dams, bridges and pavements, some of which have already been demolished. Many of these structures contain fast...

A monitoring system has been detecting progressive displacements in Fagilde dam, completed in 1984. Site inspection revealed the existence of random cracking, surface discoloration, and superficial dissolution of cement in the spillway surfaces and in the upstream face of the dam. The macroscopic signs of deterioration, which could be due to differ...

Concrete is one of the most widely used building materials since the nineteenth century. The manufacture of concrete includes the binder (cement), aggregates, water and possible additives. Although very versatile and durable, in the early 1900s, it was recognized that concrete can deteriorate and in consequence, compromise the durability and good f...

Recognizing the relevance that fieldwork and field trips have in the teaching of geosciences and related learning processes, this study presents two geological fieldwork studies that were established with Portuguese secondary school students. Both studies were focused on geoscience content knowledge, and attempted to increase environmental awarenes...

The alkali-aggregate reaction (AAR) in concrete is a group of chemical reactions that involves the reaction of certain minerals present in the aggregates with alkali and hydroxyl ions in the interstitial solution of cement paste in concrete. These reactions form an alkaline hygroscopic gel that absorbs water and expands causing internal stresses wi...

Petrography is used as a first step in assessing the potential AAR-susceptibility of concrete aggregates. When an aggregate is classified as innocuous further testing is usually not mandatory. Thus, it is important to be aware of the complex petrographic characteristics of reactive aggregates, without which there is a risk that deleterious aggregat...

Volcanic rocks have been found to be potentially alkali-reactive in a number of countries, including Japan, Iceland and Turkey. To characterize the potential reactivity of the volcanic rocks used as aggregates for concrete in the Azores islands, an experimental program is being carried out which includes petrographic examination, chemical analysis...

A large number of Portuguese concrete structures were built in the 1960-70’s with granitic aggregates, one of the main rock types used in the construction industry. Some of the structures have recently started to exhibit signs of deterioration due to alkali-silica reactions. It has been verified that the classification of granitic aggregates accord...

A sewage system, 300 km long, showed superficial deterioration of concrete just 2 years after construction. In order to re-habilitate the structure, it was necessary to identify the main mechanism of deterioration and to understand the heterogeneous distribution of the damage observed. The study was performed in a three stepped program: site invest...

Utilisation of potentially alkali–silica reactive aggregates requires reliable performance tests to evaluate the alkali–silica reactivity of various aggregate combinations, including their alkali threshold dependence on binder type. Several such performance tests have been used worldwide for more than 15 years, but none of the methods have proven t...

RESUMO – São vários os problemas geotécnicos que ocorrem após o encerramento de uma mina, entre os quais se destacam a instabilidade de taludes, a subsidência, a degradação de acessos mineiros e a instabilidade de estruturas de armazenamento de resíduos. Este último problema é o mais comum em Portugal, país onde existem cerca de 175 áreas mineiras...

Four concrete structures from Northern Portugal–three dams and one bridge–were studied. In the three dams concrete was produced with granitic aggregates. In the bridge, aggregates from an aluvial deposit were used. Pebbles show a wide range of lithologies, though dominantly siliceous. Petrographic techniques were applied in the study of these struc...