RepositóriUM Universidade do Minho
O RepositóriUM é o repositório institucional da Universidade do Minho, constituído com o objectivo de armazenar, preservar, divulgar e dar acesso à produção intelectual da Universidade do Minho em formato digital. O RepositóriUM pretende reunir, num único sítio, o conjunto das publicações científicas da UM contribuindo desse modo para o aumento da sua visibilidade e impacto e garantindo a preservação da memória intelectual da Universidade do Minho.
DEC - CEC - MAT - Comunicações a Conferências Internacionais
Mostrando recursos 1 - 20 de 57
Do engineering students need sustainable development courses? - Torgal, Fernando Pacheco; Jalali, Said
Traditional Portuguese engineering curricula
suffers from a handicap which has already been noticed in other countries. It has been designed to ensure that engineering graduates possess a strong scientific based
knowledge. This leads to close minded engineers that are unaware of the world’s problems such as the major importance of environmental degradation, with all the
consequences for life on earth. This subject cannot be overcome by adding to traditional engineering curricula a course related to sustainable development, but instead by an integrated vision of engineering curricula, that can emphasize the importance of humanism above all. This paper provides some insights about the importance...
The Bologna process : what should and should not be done? - Torgal, Fernando Pacheco; Jalali, Said
The Bologna process aims to the construction
of a European higher education area, with a system of easily readable and comparable degrees, promoting teachers and student’s mobility in order to foster European citizen’s employability and the international
competitiveness of the European higher education system. It therefore presents an amazing opportunity to reshape academia curricula, particular in the case of
engineering curriculum. In a knowledge-based economy, changing in a dramatic pace, new skills are needed. Skills like creative thinking, ecology insights, entrepreneurship, foreign languages learning, or even literature matter more than traditional core engineering issues. Unfortunately, some signs indicate that the
Bologna process led only...
Advances in adhesion between polymers and concrete - Aguiar, J. L. Barroso de; Gemert, D. van
The adhesion between polymers and concrete is complex and needs to be studied with adequate methods. One problem is about the best test to determine adhesion strength. The use of traditional tests like direct tension, flexure or shear, normally does not enable the correct determination of the adhesion strength. If the adhesive is good and the substrate’s surfaces are well prepared, the failure is in the substrate. With this kind of faitures it is possible to say that adhesion strength is higher than the failure stress. It is not possible to give a numerical value of adhesion strength. A test...
Composite rods as a steel substitute in concrete reinforcement - Pereira, C. Gonilho; Fangueiro, Raúl; Jalali, Said; Araújo, Mário Duarte de; Marques, P.
The current work is concerning with the development of braided reinforced composites rods for concrete reinforcement, as a steel substitute. The research study aims to understand the mechanical behaviour of composite rods reinforced by a fibrous structure – core reinforced braided fabric. Several samples of braided reinforced composite rods were produced. Polyester fibres were used to produce the braided fabric; several types of fibres, and several combinations of fibres, were used as braided fabric core reinforcement; and polyester resin was used as polymeric matrix. The mechanical properties of braided reinforced composite rods have been evaluated under tensile. The objective was...
Using mine waste mud to produce environmentally friendly new binders - Torgal, Fernando Pacheco; Gomes, J. P. Castro; Jalali, Said
It is now accepted that new binders, such as alkali-activated binders, are needed to replace portland cement for enhanced environmental and durability performance. Alkali-activated binders have emerged as an alternative to (ordinary portland cement ) OPC binders, which seem to have superior durability and environmental impact.This paper reports results of a research project on the development of an alkali-activated binders using mineral waste mud from the Panasqueira tungsten mine in Portugal. Results show that with proper mix design, this new binder presents exceptionally high compressive strength even at early ages. Results also indicate, better abrasion and acid resistance compared with...
Eco-efficient mortars with enhanced mechanical, durability and bactericidal performance - Eires, R.; Camões, Aires; Jalali, Said
The cracking phenomena readily found in cement-based building structures not only paves the way for deleterious structural damage resulting from water penetration, but also degrades the aesthetic elements of the edifice. Lime-pozzolan mortars, however, demonstrate a promising alternative against the effects of weathering by accommodating expansion, contraction, temperature variability and moisture change. The present work identifies lime and metakaolin
amounts, curing time and temperature as key factors affecting both the mechanical and
durability properties of mortars using metakaolin-lime mixtures. In order to improve application-specific mortar performance along mechanical, durability and bactericidal lines, the present work employs a small percentage of activators that...
Eco-friendly construction materials using gypsum and industrial wastes - Eires, R.; Camões, Aires; Jalali, Said
The sustainable construction greatly depends on the use of alternative products, such as industrial wastes. This paper reports the development of new composite materials based on gypsum incorporating granulated cork, a by-product of cork industry, cellulose fibres from waste paper and recycled used tyre fibres. The composite material developed is intended to be used as boards for non structural elements of construction, such as dry walls and ceilings. This research work studied the characteristics of the gypsum binder commercially available and its properties, as well as composite boards. In order to enhance the water resistance and mechanical properties of the...
Evaluation of inorganic polymer as adhesive material for repair of reinforced concrete - Torgal, Fernando Pacheco; Gomes, J. P. Castro; Jalali, Said
A new development in the repair and strengthening of reinforced concrete systems is the use of carbon fiber reinforced polymers (CFRP) strips bonded to concrete substrate with epoxy resins. It has been reported that epoxy adhesive used are extremely sensitive to high temperatures. Some authors conclude that the epoxy temperature should not exceed 70 º C in order to safeguard the adhesiveness of the epoxy and, thus, the integrity and adequate functioning of CFRP. It is noted that frequently exposure to direct sunlight causes temperatures higher than 70 ºC. Inorganic polymers are often referred to as geopolymers or alkali-activated cements...
Improving durability through probabilistic design - Ferreira, Rui Miguel
In order to obtain a more controlled durability and long-term performance of concrete structures in chloride containing environment special care is needed in the design phase of reinforced concrete structures. The recent development of probability-based procedures has proven to give a more realistic basis for both durability design and condition assessment of reinforced concrete structures. Although there is still a lack of relevant data, this approach has been successfully applied to several new concrete structures, where requirements to a more controlled durability and service life have been specified.
Since parameters both for concrete durability and environmental exposure typically show a high...
Ativação alcalina de cinzas volantes utilizando solução combinada de NaOH e Ca(OH)2 - Vargas, Alexandre Silva de; Dal Molin, D. C. C.; Vilela, António C. F.; Jalali, Said; Gomes, J. P. Castro
Este trabalho teve como objetivo avaliar o comportamento da resistência à compressão, ao longo do tempo, em amostras de argamassas à base de cinzas volantes álcali-ativadas. Como ativador alcalino foi utilizada uma solução combinada de NaOH e Ca(OH)2. A cura das amostras foi realizada de duas formas distintas. Na
primeira, as amostras foram mantidas em estufa à 70°C/12 hs e à temperatura constante de 22°C em sala climatizada até a idade de ensaio. Apesar de serem obtidas resistências da ordem de 20 MPa nas primeiras 24 hs, houve decréscimo da
resistência a partir da idade de 7 dias. Verificado esse comportamento, um...
Systems for superficial protection of concretes - Moreira, Pedro M.; Aguiar, J. L. Barroso de; Camões, Aires
Nowadays, it is consensual that the biggest degradation of concrete happens from
outside to inside actions, due to the penetration of moisture, active gases and aggressive ions, by mechanical, physical and chemical causes that frequently act together. A low porosity, permeability and concrete penetration to moisture and gases are the first lines of defence against several deterioration mechanisms. The durability of concrete depends largely on how
hard or easy fluids (water, carbon dioxide, oxygen) in liquid or gas form can migrate through the concrete hardened mass. When selecting the paint coating for concrete protection, importance is given to the properties of diffusion...
Betões de elevado desempenho - Camões, Aires
Os betões de elevado desempenho (BED) são, actualmente, empregues apenas em
situações particulares, sobretudo em edifícios altos e em estruturas localizadas em ambientes particularmente agressivos. Assim, o conhecimento associado a este tipo de betões não se encontra generalizado e é importante contribuir para a sua disseminação e, também, para a sua desmistificação, uma vez que os BED podem ser considerados como uma evolução dos betões convencionais, mas com elevada durabilidade.
Com o objectivo de contribuir para a sustentabilidade da construção, urge reduzir a
produção e o consequente consumo de cimento. Assim, se a substituição de elevados volumes de cimento por subprodutos industriais, como...
Probability-based durability design of concrete structures in marine environment - Ferreira, Rui Miguel; Jalali, Said
In recent years, much research work has been carried out in order to obtain a more controlled
durability and long-term performance of concrete structures in chloride containing environments. In particular,
the development of new procedures for probability-based durability design has been shown to provide a more
realistic basis for the analysis. Although relevant data is still lacking, this approach has been successfully
applied to several new concrete structures, where requirements for a more controlled durability and service life
have been specified. A probability-based durability analysis has also become an important and integral part of
condition assessment of existing concrete structures in chloride containing environments. In order...
Optimization of braided reinforced composite rods - Pereira, Cristiana Gonilho; Fangueiro, Raúl; Jalali, Said; Araújo, Mário Duarte de
This work described the deveÌopment of braided reinforced composite rods for concrete reinforcement. The research study aims to analyse the influence of braided fabrics geometry on the core reinforced brajded fabrics mechanical behaviour. Moreover, this study intends to identify the influence of different fiber types used as core reinforcement and of testing conditions on the mechanical properties of braided fabric composite rods.
Mechanical properties of braided reinforced composites - Fangueiro, Raúl; Pereira, C. Gonilho; Jalali, Said; Araújo, Mário Duarte de
This work presents the study that is being done at University of Minho concerning the development of braided reinforced composites for civil engineering purposes. A research study has been undertaken to understand the mechanical behaviour of core reinforced braided fabrics. Various samples have been produced using polyester fibers, for the production of the braided fabric, and glass, carbon, polyethylene and sisal fibers, for the core reinforcement. The results of tensile and bending tests carried out in the correspondent core reinforced braided fabrics obtained are presented and discussed. Moreover, the influence of the testing conditions and the braiding angle is also...
The mechanical properties of braided reinforced composites for application in concrete structures - Fangueiro, Raúl; Pereira, C. Gonilho; Jalali, Said; Araújo, Mário Duarte de
The current work is concerned with the development of braided reinforced composites for civil engineering applications. The research study aims at understanding the mechanical behaviour of core reinforced braided fabrics. Various samples have been produced using polyester fibres, for the production of the braided fabrics, and glass, carbon, polyethylene and sisal fibres, for the core reinforcement. The results of the tensile tests carried out in the various samples of reinforced braided fabrics obtained are presented and discussed. Moreover, the influence of the testing conditions and of the braiding angle are also studied. In order to produce braided reinforced composite rods...
New eco-friendly hybrid composite materials for civil construction - Eires, R.; Nunes, J. P.; Fangueiro, Raúl; Jalali, Said; Camões, Aires
This paper concerns the development of new hybrid composite materials using granulated cork, a by-product of cork industry, cellulose pulp, from recycling of paper residues, and hemp fibres. The binder used is either cellulose pulp or lime-pozzolan mixture. Such materials may be used as composite
boards and mortars for non structural elements of construction, such as dry walls and ceiling or floor levelling and filling. The possibility of using these composites in conjugation with light structural supports has been studied. The paper will present the properties and the manufacturing methods used to produce the above mentioned promising eco-friendly composites that can...
Bond strength between concrete substance and repair materials : comparisons between tungsten mine waste geopolymeric binder versus current commercial repair products. - Torgal, Fernando Pacheco; Gomes, J. P. Castro; Jalali, Said
An experimental preliminary investigation was conducted to evaluate bond strength between Ordinary Portland Cement concrete substrate and three repair materials. Tungsten mine waste geopolymeric binder and two commercial repair products were used as repair materials. This study indicates that tungsten mine waste geopolymeric binders possess much higher bond strength than current commercial repair products. Results also shows that commercial repair products gain no bond whatsoever to sawn concrete specimens. Scanning electron micrographs reveal that tungsten mine waste geopolymeric binders chemically bond to the concrete substrate. Cost comparisons between tungsten mine waste geopolymeric binder and current commercial repair products are also...