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Sustainable construction is high on the agenda, especially regarding building materials. Using of by-products or waste materials from other economic sectors as cement replacement material in concrete production seems to be a more sustainable option than applying ordinary Portland cement concrete. The main aim of this work was to evaluate the performance of biomass fly ash (BFA) when used as cement replacement material and as an alkalinity reserve material in high-volume fly ash concrete (HVFAC). Therefore, several compositions of concrete including BFA were tested for compressive strength, water absorption, accelerated carbonation, and chloride penetration resistance. It was noted that when small amounts of BFA were used, HVFAC properties were improved, compared with a high-volume coal fly ash concrete. These new concrete mixtures showed a positive contribution to the quality, durability and sustainability of HVFAC., The authors wish to thank the Portuguese Foundation for Science and Technology (FCT) and the Eco-Construction and Rehabilitation Doctoral Program for supporting the PhD scholarship (reference PD/BD/ 52661/2014). This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/ 04029/2020.

Reinforced concrete is usually subjected to carbonation attack. Although it is a slow development pathology, the consequences can be high, precisely in the places with greater human, residential or industrial occupation. To make matters worse, carbon dioxide concentration in the atmosphere has been increasing due to the impact of climate changes and also to the growth of number of large cities. One of the ways to increase the resistance to carbonation attack may be through the application of concrete coatings. In fact, many current constructions have a protective skin on the concrete, often ignored in the durability design project. For these reasons, this research has looked into the efficiency of the coatings when applied on concrete. Priority was given to traditional unpainted coatings, with cementitious base, hydrated lime or both. A coating based on fly ash and a thin coating of cement were also tested. All of them were applied in an ordinary Portland cement concrete. Accelerated carbonation tests were performed and the results were excellent. It was observed that the performance of the coated concretes was, on average, about 65% better when compared to the uncoated concrete.

In this research 26 different compositions of an engineered cementitious composite with different percentages of Fly ash and Silica fume, as two pozzolanic industrial waste and by-product, were mixed. The effect of different percentage of the pozzolans on durability of ECC was studied. To evaluate the durability of the material, two tests, namely water absorption by immersion and water absorption by capillary, were performed. The results from both tests demonstrated the same trend regarding the influence of the wastes on durability. In other words, by increasing the amount of pozzolans, the water absorption after immersion and boiling, decreased more than 50% besides the significant reduction in the rate of absorption by capillary (sorptivity). The results also indicated that silica fume has a higher influence on the water-absorption reduction compared to fly ash however, in the case of absence of silica fume, fly ash plays a significant role on the improvement of durability of the material., info:eu-repo/semantics/publishedVersion

To ensure the durability of concrete structures it is necessary to understand its behaviour in the presence of aggressive agents. Carbonation and chloride action are the two leading causes of degradation in reinforced concrete structures.  Despite the combined action of these two mechanisms being a reality, there is little research on the effect of CO2 presence on the chloride behaviour in concrete. This work studies the total chlorides ingress into carbonated concrete. For this, samples with CEM I 42.5R were cast with 0.6 of water/binder ratio. After 90 days of the curing period, half of the samples were subjected to accelerated carbonation (20ºC, 55%Relative Humidity and 4%CO2) for 1 month. The other half was protected with a plastic film during the same period. Chloride immersion test, based on LNEC E390 (Portuguese specification), were performed with samples subjected to both experimental conditions. Afterwards, the depth of chlorides and CO2 penetration was evaluated. The results show that, for these conditions, the CO2 presence has a direct influence on chloride behaviour. The non-carbonated samples showed a profile with a higher amount of chloride than carbonated ones., Authors thank the foundation for science and technology (FCT) for supporting this research.

Durability of construction and building materials is a pivotal issue for any civil engineering project in the context of sustainable development. In this regard, developing any material with improved durability characteristics would be of great significance particularly for infrastructures encountered aggressive environments. Ultra-high performance concrete (UHPC) is one of this promising materials, as a high-tech self-compacting composite material, which shows advanced characteristics such as self-compactness, compressive strength higher than 150 MPa, and exceptional durability performances compared to other kinds of concrete. This material offers variety of sustainable applications. It enables designers to have slim sections with higher strength, ductility and durability for applications such as shell structures, interior and exterior architectural and structural elements in any shape and texture even in high-rise structures and aggressive environments. In this paper, the durability of a specific composition of UHPC was studied. The dense matrix of the designed UHPC exhibited ultra-high durability performance through long-term and intense carbonation and chloride-ion migration tests. As results demonstrated, even after 191 days, no carbonation depth was observed. No chloride depth was also detected after 14 days of being in the chloride solution with maximum voltage of 60 V.

Fair-faced concrete, a design option in public and private buildings, works of art, common structures like bridges and retaing walls, largely built in the twentieth century is susceptible to attacks by graffiti. Durability of concrete depends on the composition and characteristics of the surface, whereby it is essential to study the effects of anti-graffiti protection systems on concrete durability and to adopt the appropriate methodology in order to preserve the integrity and authenticity of this heritage. Concrete is a porous material sometimes deteriorated over the years. The interactions between the inks and the substrate as well as the removal methods sometimes may deteriorate or alter the concrete surface, especially if it is necessary to repeat the removal process. Anti-graffiti products form a protective barrier on the concrete surface, hindering the adhesion of paints or preventing its penetration into the pores of the concrete, which facilitates graffiti paint removal. Thus, an experimental program was developed to analyze changes in durability indicators and surface properties related to concrete deterioration. The following possibilities were studied: (i) concrete without protection before and after application of the spray paint, (ii) concrete with protection before and after application of the spray paint and (iii) after paint removal. The concrete durability indicators studied were water absorption by capillarity and immersion and penetration of CO2. Analysis by stereo binocular microscope, scanning electron microscope and energy dispersive x-ray spectroscopy were performed. The results obtained show that the applied graffiti, the graffiti protection and the graffiti removal affect surface characteristics.

At ancient times, in order to protect earth buildings from the action of rain and water absorption, different construction techniques were used. For instance, the meticulous construction detail with special design for foundations, plinths, roofs and eaves, corners, frames of doors and windows, connections between different materials and above all a special care in rooms subject to moisture, related to bathrooms or kitchens. In order to enhance durability performance various wall building systems were used, such as the employ of plasters or paints periodically renovated, acting as sacrifice layers, the coating with other building materials to protect the earth wall and the use of tiles, wood or stone. Soil stabilization was also a way of increasing the durability of earth buildings by increasing their mechanical strength and resistance against water action. Being so, since ancient times, different stabilizers and additives have been mixed with earth materials to perform earth walls and earth plasters. In this context, we will present lime stabilization techniques and also the use of additives (biopolymers and minerals) concerning durability improvement of compressed soil, using lime, mineral additives, various biopolymers and the addition of used cooking oil.

"Chapter 2: Materials and Residues", The cement industry is responsible for a large part of the global environmental problems: is the largest consumer of natural resources; the most responsible for the emission of greenhouse gases, including about 1.8 Gt of CO2; and requires huge amounts of energy, corresponding to between 12 and 15% of industrial energy use. The cement is also not used in the most appropriate manner, since 40% of the consumption of concrete is due to the renovation and repair of buildings, making concrete structures inefficient because its durability is relatively low. However, in the future, concrete can and should evolve in order to improve its eco-efficiency, with a smaller amount of cement in its composition, replacing it with high quantities of mineral additions, particularly fly ash. Nevertheless, current technology may not allow this type of concrete to be very efficient, because its long-term durability may be compromised. In fact, with increasing dosage of pozzolanic mineral additions, alkali paste components are consumed in the reaction leaving it vulnerable to concrete carbonation which may compromise the passivation layer needed for steel rebar protection against corrosion. This article explores a promising approach to mitigate this problem, which consists in the careful addition of hydrated lime in the concrete composition, highlighting the synergy of its components, significantly enhancing its carbonation resistance. It is proposed, therefore, to manufacture a concrete with high volume of fly ash, low cement content and high service life period: an efficient and sustainable concrete. In this context, an experimental campaign was developed with the aim of characterization of pastes behavior with high fly ash content, in particular with respect to its durability. The results will be presented and properly analyzed., (undefined)

One of the main weaknesses of earthen architecture is the scarce durability against water action, either by rain, flood or capillarity action, especially in countries with high rainfall index. However, the vernacular earthen architecture has demonstrated that it is possible to obtain durable constructions, although this knowledge seems to have been forgotten over the years. New technologies were developed to improve the durability of earthen architecture, however, the sustainability could be compromised either by excessive use of cement or extreme waterproof materials. In this paper, one intends to identify and evaluate vernacular strategies that allowhigher protection to water action on the earth material. This way, it will be possible to understand how many earth buildings were preserved during several centuries and has resisted to harsh weather conditions.

Self-compacting concrete (SCC) should present compatible quality and cost with conventional concrete (CC). Although SCC is advantageous its processability in hot climate regions is not well understood and is the main topic of this investigation. We used similar compositions of SCC and CC to study the fresh cement workability: Marsh Cone and Vicat test for different temperatures, and a Scanning Electronic Microscopy and other tests for durability study. According to the obtained results the workability is more sensitive to temperature variation which may be critical to transport and casting. The microstructure and results of durability tests were not much different from SCC and CC; it can be therefore concluded that the durability of SCC remains compatible with the CC. A real application of SCC for a large construction works was analyzed during this research. The results showed that it was feasible to apply SCC even in hot climate regions.

Quite a big part of the world’s heritage is still made by earth constructions. The durability of the existent heritage, as well as the new earth buildings is particularly conditioned by erosion caused by water action, especially in countries with high rainfall index. With this research one intends to value the ancient knowledge in order to allow higher durability. Analysing the old building techniques to protect the earth material from the water action it is possible to understand how earth buildings were preserved, during several centuries, resisting to harsh weather conditions. Among these techniques, one can observe the incorporation of biopolymers (such as oils or fats of animal or vegetable origin), the addition of some minerals and the stabilization with lime. However, this ancient knowledge seems to have been forgotten, probably due to the existing prejudice concerning earth building which is often associated with a poor construction. This research aims, also, the study of new methods of soil stabilization, with lime and biopolymers, adapting the ancient knowledge to improve the durability related to the water action. This way, alternative solutions were obtained in order to improve the performance of earth buildings in terms of resistance, especially when in contact with water, reducing the water permeability and keeping the vapour permeability of the material, one of the main advantages of earth construction.

The service life prediction of concrete rehabilitation works is nowadays more and more significant. The rehabilitation techniques appeared as a need to solve problems posed by the degradation of concrete structures. Some years ago the rehabilitation techniques were not widespread developed and it was important to find effective and economic solutions for the problems. Now, there is more preoccupation with the service life of concrete rehabilitation techniques, like external strengthening with FRP, increase of concrete sections or reinforcement of cracked sections. The service life increase started with the quality of the concrete rehabilitation works. This includes the quality of the design, the products and the execution. Some standards are now available and establish specifications for concrete rehabilitation works. This work presents the main questions related with this subject. The use of polymers in concrete rehabilitation imposes a different analysis related with durability., Die Vorhersage der Lebensdauer von Konkretsanierungswerken wird heute mehr und mehr an Bedeutung. Die Sanierung Techniken erschien als eine Notwendigkeit, um Probleme durch den Abbau von Betonkonstruktionen Griff zu bekommen. Vor einigen Jahren wurden die Sanierung Techniken nicht sehr weit verbreitet und entwickelt, deshalb war es wichtig, effektive und wirtschaftliche Lösungen für die Probleme zu finden. Jetzt gibt es mehr Beschäftigung mit der Lebensdauer der Betonsanierungstechniken, wie externe Verstärkung mit FRP, Erhöhung der Betonteile oder Verstärkung von geknackten Abschnitten. Die Erhöhung der Lebensdauer begann mit der Qualität des Betons Sanierungsarbeiten. Dazu gehören die Qualität des Designs, die Produkte und die Ausführung. Einige Standards sind nun verfügbar und schaffen Spezifikationen für Betonsanierungswerken. Diese Arbeit stellt die wichtigsten Fragen zu diesem Thema dar. Die Verwendung von Polymeren in Betonsanierung verhängt eine andere Analyse, die mit Langlebigkeit verbunden wird.

It is well known that the concrete industry has to contribute to the sustainability of construction. For this intent it is necessary to reduce the cement content without compromising the durability requirements of the concrete constructions. Therefore, large scale cement replacement in concrete by by products such as fly ash will be extremely beneficial from the overall ecological and environmental point of view. In this context, an experimental research work was carried out focused on the evaluation of the possibility of producing low portland cement content concrete with enhanced or even high performances, including local by products such as fly ash and common low cost aggregates without any previous treatment, i. e., as received. Three different concrete mixtures (incorporating large quantities of fly ash) were made and their mechanical, workability and durability properties were characterized. The total binder used (400 kg/m3, 500 kg/m3 and 600 kg/m3) was composed by 40% of portland cement and 60% of fly ash by mass of the total cementitious material. The overall results obtained show that the compressive strength requirements, in general, are fulfilled and that these concretes are highly durable. Thus, by using this type of concrete it is possible to build more durable structures and contribute as well to the construction sustainability.

Nowadays, there is a need in solving problems about the reinforcement of concrete structures. The external reinforcement of concrete with composite materials is a technique that has acquired more and more potential. The bond between reinforcement and support is usually made with epoxy adhesives. However, it is in this part that the integrity of the system can be affected, namely by exposure to high temperatures, amongst various other reasons. In order to study the behaviour of the external reinforcement with the increase of air temperature, several beams were prepared and strengthened with CFRP laminates. After cyclical thermal exposition of 25 days, with maximum temperatures of 20°C, 40°C, 60°C and 80°C, the beams were subjected to bending tests. The results demonstrated that the improvement achieved with the reinforcement, disappears with the increase of the environment's temperature. The thermal resistance of this strengthened system is not very high, thus special needs to be taken into account when applied in warm locations., (undefined)

Hoje em dia, há a necessidade de resolver problemas em estruturas de betão armado. O reforço por adição de armaduras exteriores à base de materiais compósitos é uma das técnicas que tem vindo a adquirir cada vez mais potencial. A união entre o reforço e o suporte, geralmente é realizada com colas de base epoxídica. Contudo, é nesta fracção do sistema que a integridade do reforço pode ser afectada. Entre várias razões, destaca-se a exposição a temperaturas elevadas. Para estudar a variação do comportamento do sistema de reforço perante o aumento da temperatura ambiente, foram produzidas várias vigas de betão armado onde foram colados laminados CFRP. Após exposições térmicas cíclicas de 25 dias com uma temperatura máxima de a 20ºC, 40ºC, 60ºC e 80ºC, as vigas foram ensaiadas à flexão. Os resultados demonstram que a melhoria conseguida com o reforço à temperatura ambiente, se torna menos expressiva com o aumento da temperatura ambiente. A resistência térmica deste sistema de reforço não é muito elevada, pelo que a sua aplicação em locais quentes, requer cuidados especiais., Nowadays, there is a need to solve problems of reinforced concrete structures. The external reinforcement of concrete with composite materials is a technique that has acquired more and more potential. The bond between the reinforcement and the support is usually accomplished with epoxy adhesives. However, it is in this part that the integrity of the system can be affected, namely by exposure to high temperatures, amongst various other reasons. In order to study the behaviour of the external reinforcement with the increase of air temperature, several beams were prepared and strengthened with bonded CFRP laminates. After cyclical thermal exposure of 25 days with maximum temperatures of 20ºC, 40ºC, 60ºC and 80ºC, the beams were subjected to bending tests. The results demonstrate that the improvement achieved with the reinforcement, at air temperature, have no significance with the increase of the environment’s temperature. The thermal resistance of this strengthened system is not very high, thus special needs are to be taken in to account when applied in warm locations., Sika Portugal, S.A. Socitrel (Soc. Ind. Trefilaria, S.A.). Secil (Companhia Geral de Cal e Cimento, S.A.).

High-performance concrete (HPC) is usually produced using high quality materials. These constituents drastically increase the initial cost of HPC, thus hindering its more widespread usage. This research work intends to investigate the possibility of producing low cost enhanced performance concrete or even low cost HPC, with 28 day strengths in the range of up to 60 MPa, using low-quality-as-received materials like fly ash and locally available crushed aggregates. In this way, a significant reduction in the use of Portland cement, as well as that of scarce natural resources, would be obtained. The effect of the amount of fly ash was evaluated using 0, 20%, 40% and 60% cement replacement in mixtures with different quantities of total binder (400 kg/m3, 500 kg/m3 and 600 kg/m3). Workability, mechanical and durability properties of the produced concretes were studied. The results obtained indicate that it is possible to produce HPC with up to 60 MPa by replacing up to 40% of cement by fly ash and using locally available crushed granite aggregates. Based on the results obtained, it is possible to conclude that the use of fly ash in concrete is beneficial in terms of the workability and durability properties but has some disadvantages because early strengths are reduced. The research work also indicates ways and means to improve the performance of concretes without having its costs increased.

High-performance concrete (HPC) is usually produced using high quality materials. These high quality constituents drastically increase the initial cost of HPC, hence hindering its more widespread use. Therefore, the main goal of this research project was to produce a low cost enhanced performance concrete or even a low cost HPC, using low quality fly ash and locally available crushed aggregates. In this way, a significant reduction in the use of Portland cement, as well as that of scarce natural resources, would be obtained. The effect of high percentages of fly ash and crushed aggregates on concrete performance was studied by comparing the mechanical and durability performances of such concretes with nominally similar types of concrete with no fly ash incorporated. The results obtained indicate that it is possible to produce concrete in the low range of HPC with up to 65 MPa at 56 days by replacing up to 40% of cement with as received fly ash using crushed granite aggregates. Furthermore, it was observed that workability and durability both increased significantly when fly ash partially replaced Portland cement.

Some of the most recent developments related to the production of concrete have focused on the addition of components which can improve the mechanical, wokability and durability properties of concrete and whenever possible, to solve environmental problems in a simple and economical way. This is research work fits in this field, trying to contribute to the clearing up of the advantages and disadvantages of concrete production with the addition of fly ash (FA). High-performance concrete (HPC) is usually produced using high quality materials. These constituents drastically increase the initial cost of HPC, thus hindering its more widespread usage. This research work intends to investigate the possibility of producing low cost enhanced performance concrete or even low cost HPC, with 90 day strengths in the range of up to 60 MPa, using low quality fly ash and locally available crushed aggregates. The effect of the amount of fly ash was evaluated using 0, 20%, 40% and 60% cement replacement with different quantities of total binder of 400 kg/m3, 500 kg/m3 and 600 kg/m3. Workability, mechanical and durability properties were also studied. The results obtained indicate that it is possible to, produce HPC with up to 60 MPa by replacing up to 40% of cement by fly ash and using local available crushed granite aggregates. Furthermore, it was observed that the workability and the durability, as measured by the chloride-ion diffusion coefficient, increased drastically when fly ash partially replaced Portland cement. Based on the results obtained, it is possible to conclude that the use of fly ash in concrete is beneficial in terms of the workability and durability properties but was some disadvantages because early strengths are reduced.

Dissertação de mestrado integrado em Engenharia Civil, O ambiente marítimo é um dos meios mais agressivos a que as infraestruturas podem estar expostas. Este tipo de exposição afeta de forma severa a durabilidade das mesmas caso não sejam tomadas as devidas precauções para atenuar as consequências decorrentes deste tipo de ambiente. Na execução de novas estruturas um dos fatores mais importantes para o Projetista e para o Cliente é o fator custo/durabilidade. Neste sentido pretende-se fazer um estudo de duas soluções estruturais bem como, uma análise dos respetivos ciclos de vida, para o viaduto do terminal de petroleiros do porto de Leixões, em Portugal, uma vez que a estrutura atual chegou ao fim do seu ciclo de vida após 50 anos. Será então dimensionada uma solução de vigas pré-fabricadas e pré-esforçadas em betão armado com uma laje em betão armado e uma outra solução em vigas metálicas com uma laje em betão armado. A nova estrutura será projetada seguindo o que está prescrito nos regulamentos atuais, de onde se espera atingir um tempo de vida útil de 100 anos. É esperado que deste estudo se consiga chegar a uma solução que seja economicamente viável para a substituição do viaduto e onde se consiga atingir o tempo de vida útil esperado de 100 anos com o menor custo possível., The maritime environment is one of the most aggressive for infrastructures. This type of exposure affects severely the durability of any infrastructure, if proper preventive measures are not taken into account. In the construction of new structures one of the most important factors to take into account is the ratio cost / durability. This way, it is intended to make a study of two different structural solutions, as well as an analysis of their life cycles, for the viaduct of the oil tanker terminal of port of Leixões, in Portugal, since the current structure has reached the end of its life cycle after 50 years. It will be then designed a solution of precast and prestressed reinforced concrete beams with a reinforced concrete slab, and another solution with steel beams with a reinforced concrete slab. The new structure will be designed according to current regulations, which are developed in a way that such structures should reach a service life of 100 years. It is expected that this study will be able to provide a solution that is economically viable for the replacement of the viaduct, and where it is possible to reach the expected life time of 100 years with the lowest possible cost.

Dissertação de mestrado integrado em Engenharia Civil, A sustentabilidade da construção é um assunto com grande influência e consequências na atualidade. Uma das medidas de modo a contribuir para a sustentabilidade é reduzir a produção e o consequente consumo de cimento que deriva da construção. A produção de cimento Portland origina a libertação de grandes quantidades de CO2 e consome grandes quantidades de energia. Como o betão é utilizado na construção em grandes quantidades, pode ser utilizado de maneira a nele serem incorporados resíduos e subprodutos industriais de forma segura e económica. Um exemplo é a incorporação de cinzas volantes de carvão provenientes de centrais termoelétricas. Betão com um elevado volume de cinzas volantes, possui uma reação pozolânica lenta e, portanto, a resistência mecânica inicial do betão é menor que o betão com cimento como único ligante. O destino de valorização mais comum dos resíduos florestais é a sua valorização térmica através da combustão. As cinzas volantes de biomassa têm características semelhantes às cinzas volantes de carvão, no entanto, são mais alcalinas (maior pH) e possuem um teor de cálcio maior. O principal objetivo deste trabalho consiste em avaliar a possibilidade de produzir betões de desempenho melhorado incorporando elevado volume de cinzas volantes de carvão, bem como utilizar pequenas quantidades de cinzas volantes de biomassa, de forma a mitigar alguns dos inconvenientes dos betões com elevado volume de cinzas volantes de carvão. Com base nos resultados obtidos, a durabilidade das composições com elevado volume de cinzas volantes, revelou-se, em geral, superior à da composição de referência, com exceção relativamente à resistência à carbonatação que, contudo, foi melhorada com a inclusão de uma reduzida quantidade de cinzas de biomassa. A cinza volante de carvão possuiu uma boa sinergia com quantidades reduzidas de cinza de biomassa que resultou numa boa atividade pozolânica., The sustainability of construction is a subject with great influence and consequences at the present time. One of the measures to contribute to sustainability is to reduce the production and consequent consumption of cement that comes from construction. The production of Portland cement gives rise to the release of large amounts of CO2 and consumes large amounts of energy. As concrete is used in large-scale construction, it can be used to incorporate industrial waste and by-products in a safe and economical way. An example is the incorporation of coal fly ash from thermoelectric power plants. Concrete with a high volume of fly ash has a slow pozzolanic reaction and, therefore, the initial mechanical strength of the concrete is lower than the concrete with cement as the sole binder. The most common destination for forest residues is their thermal recovery through combustion. Biomass fly ash has characteristics similar to coal fly ash, however, they are more alkaline (higher pH) and have a higher calcium content. The main objective of this work is to evaluate the possibility of producing improved performance concrete incorporating a high volume of coal fly ash, as well as to use small amounts of biomass fly ash to mitigate some of the drawbacks of concretes with high volume of coal fly ash. Based on the obtained results, the durability of the compositions with a high volume of fly ash has generally proved to be superior to that of the reference composition, except for the resistance to carbonation which has however been improved by the inclusion of a reduced amount of biomass ash. Coal fly ash had a good synergy with reduced amounts of biomass ash which resulted in good pozzolanic activity.

The incorporation of fly ash (FA) in cementitious matrices have been frequently used in order to make the matrix more resistant to the action of chlorides. On the other hand, it is known that Ca (OH)2 existing in the matrix is partially consumed by the pozzolanic reactions, which facilitates the advancement of carbonation. Given that the combined action between carbonation and chloride penetration is a fact little known, we speculate about the behaviour of the matrix in this context. This study investigates the influence of the presence of chlorides on the carbonation in mortars with FA. Samples with 0% and 40% replacement of cement CEM I 42.5 R for FA were molded with water/binder 0.56 and 0.52 respectively. After 90 days of curing the specimens were subjected to cycles of immersion/drying for 56 days. Half of the samples was subjected to the following cycle: two days in a solution containing NaCl (concentration equal to 3.5 %); 12 days in the carbonation chamber (4% of CO2). The other half was: two days in water; 12 days in the carbonation chamber. Then, the development of carbonation was evaluated. The results indicate that the presence of chlorides influences the carbonation. The specimens submitted to the exclusive action of CO2 showed a greater depth of carbonation compared to that presented by the specimens subjected to combined action. This may be related to changes in properties of the matrix which may lead to further refinement of the pores and related to the presence of the salt that can lead to partial filling of the pores and the increase in moisture content., Foundation for Science and Technology (FCT)

Dissertação de mestrado integrado em Engenharia Civil, Uma grande parte do património construído no século vinte é em betão aparente, sendo particularmente suscetível às agressões dos graffiti. Devido ao crescente reconhecimento do seu valor e da importância da sua preservação, surgiu a necessidade de adoção de medidas preventivas capazes de minimizar o impacto e deterioração provocados pelos graffiti, bem como pelas sucessivas ações de remoção, no substrato do betão. A aplicação de um novo tipo de tratamento de proteção na superfície de betão foi a solução encontrada para combater este problema. Surgiram assim, os revestimentos de proteção anti-graffiti, permanente e sacrificial, desenvolvidos para proteger as superfícies e dificultar a aderência das pinturas, impedindo a sua fixação profunda, facilitando a sua mesma remoção. Considerando que a durabilidade do betão depende principalmente da sua composição e das características da sua superfície, é importante avaliar quais os efeitos dos produtos de proteção aos graffiti no desempenho e durabilidade do betão aparente. Neste sentido, desenvolveu-se uma campanha experimental com o intuito de analisar as alterações ocorridas nas principais propriedades relacionadas com a durabilidade de dois tipos de betão, um convencional e outro de elevado desempenho, antes e após o tratamento da superfície com produtos de proteção anti-graffiti, com a proteção anti-graffiti e os graffiti, bem como após a remoção dos graffiti. A avaliação dos indicadores de durabilidade foi feita através da realização e análise dos resultados de cinco ensaios, designadamente o de absorção de água por capilaridade, absorção de água por imersão, penetração de CO2, migração de cloretos e resistividade elétrica. Os resultados obtidos mostraram que os sistemas de proteção contribuem para o aumento da durabilidade do betão, em particular a proteção sacrificial. No entanto, sucessivas ações de remoção e pintura não foram avaliadas e poderão ser prejudiciais para a estrutura porosa do betão., A largely heritage built in the twentieth century is of fair-faced concrete, which is particularly susceptible to the graffiti attacks. Due to the increasing recognition of its value and preservation importance, the need to adopt preventive measures arose to minimize the impact and damage caused by graffiti, as well by the successive removal actions on the concrete substrate. The application of a new type of treatment to protect the concrete surface was the way to combat this problem. Thus, the protective anti-graffiti coatings, a permanent and a sacrificial, were developed to protect the surfaces and to hinder the adhesion of paints, preventing their penetration into the pores of the concrete and to make the removal process easier. Considering that the durability of concrete depends on the composition and characteristics of the surface, it’s important to evaluate the effects of anti-graffiti protection products on the durability and on the performance of fair-faced concrete. In this respect, an experimental program was developed to analyze properties changes occurred in the two types of concrete, conventional and high performance, before and after the treatment with the anti-graffiti protection products, with anti-graffiti and after graffiti, as well as after graffiti removal. The evaluation of the durability indicators was made by analyzing five tests, such as: water absorption by capillary, immersion at atmospheric pressure, penetration of CO2, diffusion of chlorides and electrical resistivity. The obtained results showed that the protective systems contribute to increase the concrete durability, in particular the sacrificial protection. However, successive removal actions may be harmful to the porous structure of concrete.

Dissertação de mestrado integrado em Engenharia Civil (área de especialização em Perfil de Construções), A degradação de infraestruturas é atualmente um tema de grande importância quer pelos custos associados na sua futura reparação e reabilitação, quer também pelas gravosas consequências sociais e económicas devido à sua utilização condicionada aquando da execução das obras de reparação e reabilitação. As investigações sobre materiais que permitam minimizar estes problemas levaram ao estudo mais aprofundado de materiais com capacidade de auto-reparação, possibilitando a obtenção de estruturas mais sustentáveis, duráveis e a custos mais baixos. Este trabalho visa reunir investigações de vanguarda relativamente a materiais de construção autoreparadores, como forma de perspetivar um futuro mais sustentável para a indústria da construção. Serão aprofundadas quatro vertentes para a auto-reparação do betão, nomeadamente, a auto-reparação com recurso à utilização de cápsulas ou fibras ocas contendo agentes químicos, por hidratação posterior, betões com ductilidade ultraelevada e auto-reparação por recurso a bactérias. Também se terá em atenção o estudo destes materiais que favoreçam a durabilidade do betão e minimizem os efeitos prejudiciais para o ambiente durante a sua produção. Apesar das investigações promissoras na incorporação de cápsulas ou fibras ocas contendo agentes químicos para a auto-reparação de betões, existem controvérsias relativamente à sua utilização. O facto de ser necessário cápsulas ou fibras ocas bastante frágeis e de as mesmas aumentarem a porosidade do betão, são algumas das razões que impedem a sua aplicação imediata pela indústria de construção. A auto-reparação por hidratação posterior inclui a hidratação posterior de partículas de cimento não hidratadas e também a formação de carbonato de cálcio a partir do cálcio da pasta de cimento que reage com o dióxido de carbono dissolvido na água. Os betões de ductilidade ultraelevada reforçados com fibras usualmente designados na literatura científica pela abreviatura ECC são materiais com uma razão água/cimento reduzida e um volume de fibras inferior a 2%. Estes promissores materiais possuem uma elevada capacidade de auto-reparação (por hidratação posterior) pelo facto de conseguirem impedir que as fissuras não excedam 60 m mesmo no caso de elevadas deformações. O uso de bactérias para a auto-reparação do betão é um método natural e está associado com a precipitação mineral que ajuda a preencher os microporos e fissuras, reduzindo assim a sua permeabilidade. Contudo estes materiais ainda se encontram numa fase de investigação inicial longe da sua utilização efetiva pelo sector da construção., Infrastructures deterioration is currently a topic of great importance due to the associated costs in its future repair and rehabilitation and also of serious social and economic consequences related to its conditioned use upon the execution of repair and rehabilitation works. Investigations into materials that can minimize these problems led to the further study of materials capable of self-healing, allowing for sustainable structures, with higher durability at lower costs. This work aims to bring together cutting-edge research on self-healing building materials as a way of shaping a more sustainable future for the construction industry. Four particular areas are addressed in this work. The cases of self-healing of concrete, in particular with the use of capsules or hollow fibers containing chemical agents, self-healing by subsequent hydration, ultra high ductility concrete and self-healing using bacteria. Concerns related to self-healing towards enhanced concrete durability and lower environmental impacts are also addressed. Despite the promising investigations on incorporation of capsules or hollow fibers containing chemical agents for self-healing of concrete, there are still some controversies regarding its use. Capsules or hollow fibers are quite fragile and increases the porosity of the concrete, constituting some of the reasons that prevent their immediate application in the construction industry. The case of self-healing by further hydration focuses on the potential of the concrete to auto repair itself, it evolves the hydration of unreacted particles and formation of calcium carbonate, a result of reaction between calcium ions from the matrix of concrete and atmospheric carbon dioxide dissolved in water. Concrete based on engineered cementitious composites fibre reinforced usually know as ECC are materials with a low water/cement binder and a low fibre content (below 2%). These promising materials have a high selfhealing ability (by further hydration) because they can maintain microcrack width below 60 m even for high strain conditions. The use of bacteria for self-repair of concrete is a natural method and is associated with mineral precipitation which helps fill in the micro pores and cracks, thus reducing its permeability. However, these materials are still in an early investigation stages far from real applications by the construction sector.

Dissertação de mestrado integrado em Engenharia Civil, É do conhecimento geral que cada tonelada de cimento produzida é responsável pela emissão de uma tonelada de CO2 para a atmosfera e, considerando o gigantesco volume de cimento produzido mundialmente, qualquer redução significativa na sua produção e consumo, trará vantagens ecológicas significativas. De modo a contribuir para sustentabilidade da construção, a presente dissertação pretende dar um contributo para a redução do consumo de cimento, através da sua racionalização, substituindo elevados volumes de cimento no fabrico de betões por adições, nomeadamente subprodutos industriais, tais como as cinzas volantes. Contudo, betões com elevados volumes de cinzas volantes possuem alguns inconvenientes, os quais têm impedido a sua generalização, pelo que se tentou mitigar tais inconvenientes, através da incorporação de outras adições minerais (metacaulino e cal hidratada), que possam corrigir os principais inconvenientes associados a este tipo de betões. Ainda relacionado com a eco-eficiência deste material, procurou-se produzir um betão auto-compactável, evitando assim a necessidade de vibração e consequente poluição sonora, para além, de se evitar decréscimos na durabilidade das estruturas resultantes de uma deficiente compactação do betão. Para tal, desenvolveu-se um programa experimental capaz de caracterizar o desempenho, face à resistência e durabilidade, de misturas binárias, ternárias e quaternárias, produzidas com elevados volumes de cinzas volantes e pequenas percentagens de metacaulino e cal hidratada. Da análise dos resultados obtidos é possível evidenciar que a sinergia resultante destas misturas revelou desempenhos promissores, concluindo-se que é possível produzir betões auto-compactáveis com elevados volumes de cinzas volantes e, pequenas percentagens de metacaulino e cal hidratada, com desempenhos mecânicos e de durabilidade adequados à maioria das infra-estruturas correntes, a um custo bem mais reduzido que o preconizado actualmente pelo betão corrente, podendo-se traduzir numa solução viável para a obtenção de um betão eco-eficiente., It is common knowledge that every ton of cement produced is responsible for emitting a ton of CO2 into the atmosphere and considering the huge amount of cement produced worldwide, any significant reduction in its production and consumption, will bring significant environmental benefits. In order to contribute to sustainable construction, the present paper aims to contribute to the reduction in cement consumption through its rationalization, replacing large volumes of cement by additions, including industrial byproducts such as fly ashes. However, concrete with high volumes of fly ashes have some drawbacks which have prevented its widespread and it is attempted to mitigate these drawback by incorporating other mineral additions (metakaolin and hydrated lime) which can fix the main drawback associated to this type of concrete. Also related to the eco-efficiency of this material, we sought to produce a self-compacting concrete, avoiding the need for vibration and subsequent noise, as well, preventing a decrease in durability of the structures as a result of a poor compaction of the concrete. To this end, it was developed an experimental program able to characterize the performance, concerning to the strength and durability of binary, ternary and quaternary mixtures, with high volumes of fly ash and small percentages of metakaolin and hydrated lime. After the analysis of the results, the synergy resulting from the mixtures showed promising performances, concluding that it is possible to produce self-compacting concretes with high volumes fly ash and small percentages of metakaolin and hydrated lime, with mechanical and durability performances suitable for the most current infrastructure at a much lower cost than the traditional concrete, which could represent a viable solution to obtain an eco-efficient concrete.

Doctoral Thesis for PhD degree in Civil Engineering., Ultra-high performance concrete (UHPC) is a promising type of self-compacting steel fiber-reinforced concrete, which exhibits extraordinary performances in its fresh and hardened states. It not only demonstrates ultra-high strength in compression, but also exhibits ultra-high durability characteristics. Since sustainability-related issues have become major priorities in the world ahead in recent years, therefore, a special attention to any product and service, particularly those used with an increasing pace and embrace considerable carbon footprint and substantial economic impacts, such as UHPC with high content of cement and silica fume, would be of great significance. In this scope, this research aimed to develop an eco-efficient type of UHPC as an innovative and high-tech material through partially substitution of cement and silica fume by other pozzolanic industrial-waste materials. Response surface methodology (RSM), as a statistical mixture design tool, was applied in order to create a scientific basis for developing the optimum composition with higher environmental and economic efficiency. The performance of the optimum composition, nominated as eco-efficient UHPC (EEUHPC), was evaluated through standard test methods in its fresh and hardened states. Furthermore, an effective low-energy mixing procedure, with the aim of improved flowability, was introduced. Finally, the autogenic self-healing ability of the material was studied as an important issue regarding the life cycle of the material and its capacity for structural recovery. The tests were carried out in short and long-term life of the material. Effect of different crack widths on self-healing capacity of cracked specimens was investigated as well as influence of steel fibers on energy absorption of samples in post-cracking stage., O betão de ultra elevado desempenho (BUED) é um tipo de betão autocompactável reforçado com fibras bastante promissor e que é dotado de um desempenho extraordinário tanto no estado fresco como no estado endurecido. Este tipo de betão não só apresenta ultra elevada resistência à compressão como, também, é caracterizado por ultra elevada durabilidade. Nos últimos anos as questões relacionadas com a sustentabilidade passaram a ser consideradas prioritárias em todo o mundo. Portanto, passou a ser de importância acrescida garantir especial atenção a qualquer produto ou serviço, em particular os de utilização crescente compreendendo uma considerável da pegada de carbono e impacto económico substancial, tal como o BUED, fabricado geralmente com um teor de cimento e sílica de fumo elevados. Neste âmbito, este trabalho teve como objetivo desenvolver um material inovador e de alta tecnologia, um BUED eco-eficiente, produzido com recurso à substituição parcial de cimento e sílica de fumo por subprodutos industriais com características pozolânicas. A definição das composições foi efetuada recorrendo à metodologia de superfície de resposta (MSR), uma ferramenta estatística que permitiu determinar, com base científica, as composições ótimas, com maior eficiência ambiental e económica. O desempenho da composição ótima, designada BUED eco-eficiente (BUEDEE), foi avaliado por intermédio de ensaios laboratoriais, realizados tanto no estado fresco como no estado endurecido. Além disso, foi também desenvolvido um processo de mistura eficaz e de baixa energia, concebido com o objetivo de melhorar a fluidez. Finalmente, a capacidade de autorreparação autogénea do material foi estudada como uma questão importante relacionada com o ciclo de vida do material e com a sua capacidade de recuperação estrutural. Os testes foram realizados tanto em idades iniciais como a longo prazo. O efeito da abertura de fenda na capacidade de autorreparação dos provetes fendilhados foi avaliado, assim como a influência da presença das fibras metálicas na capacidade de absorção de energia de provetes em estado pós-fendilhado.

Tese de Doutoramento em Engenharia Civil, The environmental impact related with the use of several materials in construction sector is in the order of the day. It is well known that the production of Portland cement, one of the materials most used in the construction sector, has a significant contribution to the environmental impacts, mainly related with carbon dioxide emission. Therefore, the study and utilization of by-products or wastes usable as cement replacement in concrete can supply more sustainable options, but maintaining or improving the quality and durability properties of plain cement concrete. Worldwide, coal fly ash (CFA) is the most used supplementary cementitious material in concrete production, mainly because it presents several advantages such as: it is a by-product of coal combustion, is available in great quantities worldwide and is cheaper than Portland cement. Nowadays, coal fly ash is commonly used as cement replacement in concrete from 0 to 40%wt. Using high volumes of these materials has some drawbacks, one of them being the decrease of the pH of concrete thus leading to carbonation issues. In order to understand phenomena such as this, it is important to study the interaction between the mineral additions and hydration of cement and try to find new solutions for the issues related with this type of concrete. The utilization of biomass fly ash (BFA) as partial replacement of cement in concrete production has been studied by several authors and it was verified that this alkaline material can have benefits for concrete. However, its application in high volume fly ash concrete has not been so much studied and because of its characteristics, mainly chemical characteristics, can be a solution to, for example, the carbonation issue of these concretes. So, the main objective of this work was to assess the use of biomass fly ash as cement replacement material or at least as an alkalinity source in high volume fly ash concrete, with a focus on the effect of using biomass fly ash on the quality, durability and sustainable properties, such as: workability, mechanical resistance, resistance to carbonation, resistance to chlorides ions penetration, shrinkage, porosity, leaching of toxic compounds and environmental performance. The results of this study showed that biomass fly ash can improve the properties of high volume fly ash concrete when it is used in small amounts, being the best results verified for 0.5%wt and 1.3%wt of BFA blended with the equivalent proportion of coal fly ash to maintain 50%wt of cement replacement. The two fly ashes seem to have a good synergy in those situations. BFA blended with CFA seems to have a positive contribution on the quality, durability and sustainability of concrete when compared with concrete containing only coal fly ash as supplementary cementitious material or when compared to a plain cement concrete. Thus, with the utilization of BFA, at an industrial level of concrete production, some issues can be minimized, such as the decrease on energy and raw materials consumption related to cement production, and also issues related with the concrete properties and a more sustainable option on the ash management can be applied, than its landfill deposition., O impacte ambiental relacionado com o uso de diversos materiais no sector da construção está na ordem do dia. É bem sabido, que a produção do cimento Portland, um dos materiais mais usados na construção, tem uma contribuição significativa para os impactes ambientais, essencialmente relacionados com a emissão de dióxido de carbono para a atmosfera. Assim, o estudo e a utilização de subprodutos ou resíduos, usáveis como substitutos do cimento na produção de betão, podem oferecer opções mais sustentáveis, mas mantendo ou melhorando a qualidade e a durabilidade do betão convencional. Por todo o mundo, as cinzas volantes de carvão (CVC) são o material cimentício suplementar mais utilizado na produção de betão, principalmente por apresentarem diversas vantagens, tais como: ser um subproduto da combustão do carvão e estar disponíveis em grandes quantidades, e serem mais baratas do que o cimento Portland. Hoje em dia, as cinzas volantes de carvão são utilizadas em proporções de substituição do cimento de 0-40%m. A utilização de grandes volumes de cinzas tem alguns problemas e um deles é a diminuição do pH do betão que conduz a problemas de carbonatação. Para entender fenómenos como este, é importante estudar a interação entre as adições minerais e a hidratação do cimento e tentar encontrar novas soluções para os problemas relacionados com este tipo de betões. A utilização de cinzas volantes de biomassa (CVB) como um substituo parcial do cimento na produção de betão tem sido estudada por diversos autores e foi verificado que este material alcalino pode trazer benefícios para o betão. Contudo, a sua aplicabilidade em betões com elevado teor de cinzas volantes não foi ainda muito estudada e, devido às sua características, principalmente químicas, pode ser uma solução para o problema da carbonatação destes betões. Assim, o principal objetivo deste trabalho foi o de avaliar se é possível o uso de cinzas volantes de biomassa como substituto material do cimento ou como reservatório de alcalinidade nos betões com elevado teor de cinzas volantes, focando-se no efeito do uso das cinzas volantes de biomassa na qualidade, durabilidade e sustentabilidade, tais como: trabalhabilidade, resistências mecânicas, resistência à carbonatação e à penetração de iões cloretos, retração, porosidade, lixiviação de compostos tóxicos e o desempenho ambiental. Os resultados, obtidos neste estudo, mostraram que as cinzas volantes de biomassa podem melhorar as propriedades dos betões com elevado volume de cinzas volantes, quando utilizadas em pequenas quantidades, sendo os melhores resultados observados para valores de 0.5%m e 1.3%m de CVB misturada com a proporção equivalente de cinzas volantes de carvão, que correspondem a uma substituição de cimento de 50%m. As duas cinzas parecem apresentar uma boa sinergia nestas situações. A mistura das duas cinzas aparenta apresentar uma contribuição positiva na qualidade, durabilidade e sustentabilidade dos betões, quando comparada com betões só com CVC como material cimentício suplementar ou quando comparada com o betão de cimento, sem incorporação de adições minerais. Assim, a utilização das CVB num nível industrial de produção de betão pode resolver alguns problemas, nomeadamente conduzindo à diminuição de energia e matérias-primas consumidas na produção do cimento e, também problemas relacionados com as propriedades do betão, apresentando-se como uma opção mais sustentável para a gestão das cinzas do que a sua deposição em aterro., Fundo Social Europeu da União Europeia (EU/FSE) através da Fundação para a Ciência e Tecnologia (FCT) que me atribui uma Bolsa de Doutoramento PD/BD/52661/2014, no âmbito do Programa Doutoral ―Eco-Construction and Rehabilitation‖ e no âmbito dos fundos FEDER através do Programa Operacional Competitividade e Internacionalização (COMPETE) e através da Fundação para a Ciência e Tecnologia (FCT) através do projeto POCI-01- 0145-FEDER- 007633 e através do Programa Operacional Regional (CENTRO02020) através do projeto CENTRO-01- 0145-FEDER- 000006. Em especial agradeço ao Programa Doutoral EcoCore, na pessoa do seu Director Professor Jorge de Brito, o qual deu um grande suporte ao trabalho desenvolvido.