Showing papers by "Said Jalali published in 2007"

Quantification of construction waste amount

Abstract: This article outlines the importance of the quantification of wastes for a sound and adequate management of waste in the construction of buildings. It is noted that such quantifications provide a necessary tool for evaluating the true size of the wastes and hence making the adequate decisions for their minimization and sustainable management. This information also provides the essential information for a better pricing of construction bids and hence the user would be more competitive on the market. Furthermore, the quantification of wastes enables a more adequate planning of the construction site and the related logistics in terms of containers and their management. This will provide the necessary information not only on the amount but also on the type and time of waste generations. Environmental and economic gains are thus incentives for contractors to opt for this prior quantification and planning. Two approaches for quantification of wastes are outlined. The Component Index (CI) enables quantification of wastes for each constructive component in the overall project. As for the Global Index (GI), this provides the necessary indicators for a given type of building, which can then be used for similar future buildings and hence facilitates the overall estimation of the wastes. The usefulness of preparing such data files, as well as the necessity for their updating and refining progressively is indicated. As the basis for the quantification of wastes, examples of CI and GI are presented. Data for these data files have been gathered empirically on construction sites and are good indicators for a first approach to the quantification of wastes. The waste managers are encouraged to update and refine these files to their own specific conditions and circumstances.

Cinzas volantes álcali-ativadas com solução combinada de NaOH e Ca(OH)2

Abstract: The main objective of this work was to evaluate over time the development of the compressive strength of alkali-activated fly ash mortars. A combined solution of NaOH and Ca(OH)2 was used as alkaline activator. The curing of the samples was carried out in two distinct ways. In the first one, samples were kept at 70°C during the first 12 hours after mixing and at 22°C afterwards, until the age of testing. Although compressive strengths of about 20 MPa were achieved during the first 24 hours, the strength started to decrease after 7 days. Considering this behaviour, a second method of curing was adopted. The mix proportions were the same as before, however the mortar samples were kept in an oven at 70°C until the age of testing. In this case, the compressive strength values decreased more significantly and in a shorter period of time, as compared to the results obtained for samples cured using the first method. Complementary studies were performed in order to better understand the observed reduction in compressive strength. Microstructural analyses of the fly ash, before and after the alkali-activation, have been carried out using Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS). It was possible to identify three different morphologies in the alkali-activated pastes: one composed by regions with dense aspect; other showing partially solubilised particles of fly ash; and a third showing the formation of products with a needle-like shape. The information provided by the SEM/EDS experiments was not enough to enable the complete understanding of the mechanism of the deleterious reaction that took place among the alkaline activators and the fly ash. Therefore, future studies should address this question by using additional analysis tools in order to clarify this deleterious mechanism.

Life cycle assessment of steel and reinforced concrete structure: a new analysis tool

Abstract: In this paper is discussed the life cycle of steel and reinforced concrete structures using a simplified life cycle analysis. The developed methodology consisted in quantification of a series of parameters both economic and environmental that characterize both reinforced concrete and metallic structures. The parameters obtained are a result of an ongoing investigation in civil engineering companies in Portugal. Based in the life cycle analysis, five parameters were selected in order to make the assessment, in witch: energy consumption, water, CO2, SO2, NOx. A database was developed into a software program that can perform life cycle analysis of these types of structures giving their physical properties. Furthermore, the software was developed in a way that can be used with other types of materials and can be upgradeable in the future in order to expand the number of parameters in analysis. As a result the software outputs the total amount of emissions caused by the production of a given structural element as well as determines the structural costs giving in the end a global project analysis. In the international scenario, the responsible entities have been present. Between them we have the International Organization of Standardization, in which the ISO 14000 norm as become one of the most relevant tools in the environmental managing. The application models of Life Cycle Assessment (LCA) for selection of construction materials constitutes, at present, a more complete methodology, bounding the materials selection with a global environmental performance (e.g. environmental impacts). The Life Cycle Assessment follows four basic steps, in which step can consist in one or two phases as can be seen in fig.1. Figure 1 – Scheme of the Life Cycle Assessment phases. Currently there are no software tools available to help decision makers assess in direct manner energy consumption, water, CO2, SO2 and NOx values regarding the construction of a building. The need for such tools has resulted in the environmental deterioration and the need of quantification of such parameters. The application of this tool will enable decision makers to better manage the LCA of a building by developing appropriate control measures to minimise these risks by, for example, prioritising their operational maintenance strategies. In this study we’ve focused on the environmental impacts caused by the manufacturing and transport of necessary materials to build a reinforced concrete or a steel structure. The final results allowed us to decide which structure is more sustainable financially and environmentally. To do so, a software program was developed that allows a Life Cycle Assessment of the parameters earlier referred of any kind of structure. All collected data was inserted in the database program regarding Portuguese parameters in order to create a more accurate simulation.

Argamassas antigas: reacção pozolânica ou activação alcalina?

Abstract: Resumo: No presente artigo procede-se a uma análise das explicações clássicas relativas à durabilidade das argamassas antigas. A grande maioria das descrições sobre as argamassas antigas, nomeadamente sobre o período referente à civilização romana, refere-se à importância da adição de pozolanas naturais ou artificiais na obtenção de argamassas de elevada resistência mecânica e à acção da água, são contudo omissas no que respeita aos mecanismos de reacção que expliquem essa resistência, sendo também omissas relativamente à explicações para a presença zeólitos na composição daquelas argamassas. Neste artigo são avançadas explicações para o fenómeno da durabilidade das argamassas antigas, com base na teoria da activação alcalina. Palavras–chave: argamassas antigas, pozolanas, durabilidade, activação alcalina.

Eco-friendly construction materials using gypsum and industrial wastes

Abstract: 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 composites several mineral additions were evaluated. Physical and mechanical properties of the developed boards were studied. Finally, fibre reinforced composites using waste materials were produced and analysed. Conditions and procedures of production were also studied using a pressure curing method in order to improve further the performance of the boards. has 220 factories that produce gypsum products and employ, direct or indirectly, more than 400 000 persons. In Portugal it have been produced about 500 000 ton of gypsum for each ear since 2000 (www.wastebook.org, 2007). The building sector consumes about 95% of total gypsum produced. It is calculated that about 80 to 90% of finishing interior work and partition walls in buildings are made of gypsum products, such as plaster and card gypsum. According to those thermal and acoustical properties, these products contribute significantly for the comfort of millions of persons. Having an extraordinary resistance to fire, the gypsum products contribute for the buildings security, particularly in public buildings. One of the biggest deficiencies of gypsum as construction material is the low resistance to water. Although, actually, this aspect can be partially solved by adding to the gypsum some compounds based on silicones or other polymers, namely in gypsum card boards. This way, gypsum can be submitted to humid conditions, but even so do not permit utilization in external environments because of its low resistance to long direct contact with water. The main purpose of this research work was to develop gypsum boards with enhanced mechanical and water resistance. To these boards were also incorporated wastes to turn them more lightweight and sustainable. It was intended to show that the manufactory of these boards for not structural construction elements is possible, for example, for internal and external coverings, dry walls and ceiling. For this, it was carried out the characterization and improvement of gypsum as construction material, turning it more resistant to water action. After, applications of this enhanced gypsum based material were studied focused on the mixture preparation, methods of casting and its corresponding physical performance.

Composite rods as a steel substitute in concrete reinforcement

Abstract: 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 to identify the type of fibre, or combination of fibres, to be used as braided fabric core reinforcement, in order to produce composite rods with mechanical properties similar to those of steel rebars.

Do engineering students need sustainable development courses

Abstract: 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 of addressing sustainable development subjects in a holistic manner.

Eco-efficient mortars with enhanced mechanical, durability and bactericidal performance

Abstract: 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 bring about effects in terms of bactericidity, strength gain enhancement and strength improvement at long curing time. Furthermore, this new mixture is especially suited for replacing cement-based mortars due to its specific characteristics of flexibility, water vapour permeability and environmentally sound, composition consisting of a lower measure of both embodied energy and manufacturing-related CO2 emissions. Much like fly ash or fume silica, metakaolin is ideal as a partial substitute for cement in concrete and mortar compositions thereby substantially reducing the amount of cement consumption. This specific application of metakaolin, moreover, covers structural concrete, lightweight concrete, pre-cast concrete, mortars and plasters while improving compressive and flexural strength, reducing permeability and efflorescence, offering better protection against chemical attack, , reducing fissures and improving the finishing, colour and appearance. The metakaolin used in the current study was extracted from aggregate mining wastes that underwent heat-treatment. This process, moreover, led to the obtaining of an amorphous, alumino-silicate material that readily reacts with calcium hydroxide which, in turn, gave rise to cementitious materials. The utilized metakaolin resulted from the transformation of kaolin at 600oC in an industrial oven (referred to in this work as Mk600). This material is rich in silica (SiO2) and alumina (Al2O3), has a pink coloration that is lighter than those found in red ceramics and has a density of 2564 kg/m 3 . Particle size analysis indicated it to be 20% coarser than 0,212mm and 80% coarser than 0,106mm, with a maximum particle size of 0,425mm. Lime mortars exhibit a very low rate of strength gain, are structurally vulnerable at early curing time, gain strength sufficient for most uses after a long curing period and are not water resistant. It is in light of the abovementioned reasons, therefore, that pozzolans are added to lime mixtures. The main benefits associated with the use of this type of lime-metakaolin mixture are not only functional and environmentally sound, but also much more cost efficient.. In functional terms, metakaolin improves workability and can, in some cases, reduce water content; increase mechanical properties boost permeability and enhance durability against chemical attacks. Furthermore, it substantially decreases the presence of cracks due to the low hydration heat and slow strength gain. From an economic standpoint, , pozzolans are less expensive than ordinary Portland cement, and have the added advantage of consuming less energy than OPC during the production phase. Furthermore, industrial by-products were used in this study in order to enhance environmental efficacy while lowering costs. When used as a cement substitute, pozzolans decrease energy consumption levels and lower CO2 (Malhotra & Kumar, 2000) emissions. Hydrated lime was used in this study with less than 1% water content, a maximum particle size of 0,2 mm and a bulk density at roughly 500 kg/m 3 . The activators consisted of calcium and sodium chlorides, sodium hydroxide, borax (tetraborate of hexahydrated sodium) and gypsum with a selection criteria consisting of their possible positive effects on mechanical strength, as well as on either the acceleration or retardation of mortar strength gain with respect to curing time. The amounts of activator used were 1 to 2% of the binder mass. 3 METHODOLOGY AND RESULTS 3.1 Manufacture of Test Specimens Metakaolin-lime mixtures were prepared with 75% metakaolin and 25% lime with a water to binder ratio of 0,6 due to high water absorption of the components and wet earth consistency. A homogeneous mixture of dry metakaolin and lime was prepared in a laboratory mixer, to which water was then added to achieve a workable mixture. The mineral activators were dissolved in water and later added to the mixture. Cylindrical test specimens were molded by static compaction (see figure 1). The specimens were 3cm in diameter and 3.7cm in height. The equipment allowed for the production of test specimens with constant mass. The manufactured specimens had a wet mass density of 40g (see figures 2 and 3) and a dry mass of 25g, corresponding approximately to an apparent dry density of 956kg/m 3 . The specimens were stored in a hermetically sealed conventional plastic box, with a small container of water and absorbent paper in order to maintain a relative humidity close to 100% without the specimen coming into direct contact with either water or air. By invoking this method, it was possible to uphold the necessary conditions for the curing process with a minimal interference of CO2, and a consistently high level of relative humidity. The obtained compressive strengths consisted of average test values for three specimens at each age. Figures 1 and 2 – Hydraulic press and packing of specimens for tests 3.2 The Effect of Lime Percentage in Metakaolin-Lime Mixtures In order to evaluate the effect of lime percentages on mixture performance (See the table 1), two distinct compositions of metakaolin-lime were analysed while holding the water to binder ratio constant and equal to 0,6. . Table 1 – Mix Design of metakaolin-lime mixtures Mixture Materials Quantities MK600 75% Lime 25% M1 Water/Binder 0,6 MK600 50% Lime 50% M2 Water/Binder 0,6 The specimens were prepared by the static compaction method while keeping the specimen dry density constant.(See manufacture of test specimens in 3.1). The specimen showed a smooth surface with a light pink metakaolin coloration, satisfactory cohesion and rigidity for handling and a characteristic ceramic-like sound when tapped. Figures 3, 4 and 5 – Specimens of metakaolin-lime mixtures: before and after the tests Compressive strength tests showed fragile conic ruptures that are indicative of satisfactory cohesion (see figures 3-5). Results of compressive strength tests until the age of 90 days are presented in figure 6. From this, it may be seen that the M2 mixture, with 50% lime content, shows higher strength at the first two weeks. At 14 days the two mixtures, have approximately the same strength. From this age onwards, the M1 mixture presents a slightly superior strength.

Tungsten mine waste geopolymeric binder versus ordinary portland cement based concrete: abrasion and acid resistance

Abstract: This paper reports results of a research project related to the development of geopolymeric binder using mineral waste mud from the Portuguese tungsten mine Panasqueira. Abrasion and acid resistance of two ordinary Portland cement (OPC) strength class concrete mixtures (C20/25 and C30/37) and several tungsten mine waste mud (TMWM) geopolymeric binder mixtures was evaluated. Acid resistance was performed by submitting samples to solutions of sulphuric acid, nitric acid and chloridric acid, results of weight loss are reported. Abrasion resistance was assessed by the mass loss of cubic specimens when submitted to 1000 rotations with the Los Angeles apparatus test machine. This study indicates that TMWM geopolymeric binders possess higher acid and abrasion resistance than OPC based concrete mixtures.

Estudos sobre a composição de argamassas obtidas através da activação alcalina de lamas residuais de minas

Abstract: Resumo: Este artigo apresenta resultados de um trabalho de investigação sobre o desenvolvimento de argamassas activadas alcalinamente, a partir de lamas residuais de minas (AALRM). Neste trabalho analisou-se a influência da concentração de hidróxido de sódio e da percentagem de substituição de lamas por hidróxido de cálcio, na resistência de argamassa. Os resultados obtidos mostram a utilização de composições com uma razão mássica silicato de sódio/hidróxido de sódio de 2,5:1 e uma percentagem de hidróxido de cálcio de 10%, conduzem aos melhores resultados em termos de resistência à compressão das argamassas. Os trabalhos desenvolvidos permitem também afirmar que a razão atómica H2O/ Na2O condiciona de forma significativa a resistência à compressão. Palavras–chave: lamas residuais, activação alcalina, composição, resistência.

Utilização de ligantes obtidos por activação alcalina de lamas de minas para reparação de estruturas de betão

Abstract: Resumo Neste artigo apresentam-se resultados de uma investigacao sobre o desenvolvimento de um novo material ligante sintetizado a partir de lamas de minas. O desempenho mecânico do novo ligante e comparado com o desempenho de dois produtos comerciais de reparacao de estruturas de betao. Os resultados obtidos indicam que o novo ligante apresenta um desempenho mecânico superior aos produtos comerciais, com um custo inferior e com vantagens ambientais acrescidas. Sao tambem apresentados resultados da microestrutura da ligacao betao/novo ligante comprovando a existencia de uma ligacao de natureza quimica.

Braided reinforced frp rods

Abstract: The current work is concerning the development of braided reinforced composite rods for civil engineering applications, namely for concrete internal reinforcement. The research study aims to understand the mechanical behaviour of braided reinforced composite rods produced from an innovative technique. Seven types of braided reinforced composite rods were produced, varying the type of fibres used as a core reinforcement of a polyester braided fabric. E-glass, carbon, HT polyethylene fibres were used in different combinations. The mechanical properties of the braided reinforced composite rods were evaluated under tensile in order to identify the type(s) of fibre(s) to be used as core reinforcement. Results are compared to those of conventional materials used for concrete reinforcement, such as steel. Results show that braided reinforced composite rods with lower amount of E-glass fibre present the best tensile performance. Moreover, rods with highest percentage of HT polyethylene present highest tensile performance when rods with the same quantity of E-glass and carbon fibres are considered. The type of reinforcing fibre used presents higher influence than the fibre volume fraction on the tensile performance of the FRP rods. Even though, the tensile strength of FRP rods is higher than that of steel rebars, however their modulus of elasticity is lower.

The Bologna Process: What Should And Should Not Be Done

Abstract: 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 to a change in the length of the graduation cycles, which may become a lost opportunity to change our future into a sustainable and better one.