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- Durability of the adhesion between bituminous coatings and self-protection mineral granules of waterproofing membranesPublication . Marques, J. A.; Lopes, Jorge; Correia, J. R.Flat roofs in current buildings include a waterproofing system, often made of bituminous membranes with a self-protection constituted by mineral granules. These granules constitute the barrier against the fundamental environmental agent of degradation, the UV radiation. Therefore it is of paramount importance to understand the long-term performance of the self-protection layer, namely its adhesion to the coatings of bituminous membranes. This paper presents an experimental study on the behaviour of the self-protection granule of bituminous membranes when subjected to environmental agents of degradation. Different types of atactic polypropylene (APP) and styrene–butadiene–styrene (SBS) modified bituminous membranes, comprising different finishing systems, were exposed to the effects of elevated temperature and water for up to 24 weeks and 4 weeks, respectively. Following accelerated ageing, specimens of the different types of membranes were subjected to brushing tests, carried out according to EN 12039, in order to evaluate the adhesion of the self-protection granules. The results obtained in this study, which are compared with performance limits recommended by UEAtc directives, show that the higher loss of self-protection granule of bituminous membranes occurs in membranes modified by APP polymers. In addition, it was concluded that the effect of water is much more severe than that of elevated temperature.
- The effect of wind suction on flat roofs: An experimental and analytical study of mechanically fastened waterproofing systemsPublication . Silva, R. R.; Lopes, Jorge; Correia, J. R.Presently, mechanically fastened waterproofing systems are widely used in large roofs, mostly in industrial and commercial buildings. This paper presents a study of this constructive system that included the analysis of the mechanisms of response to wind loads and the effects of the different components on the system’s wind resistance. Wind up lift tests were performed on mechanically fastened waterproofing systems, according to the guideline for European technical approval (ETAG 006), in order to evaluate the influence of both the thermal insulation thickness (from 40 mm to 100 mm) and the characteristics of the atactic polypropylene (APP) modified bitumen waterproofing membranes (different constitutions, single/double layer) on the resistance to wind up lift. All tested mock-ups failed due to peeling of the overlapping membranes. Within the range of analysed systems, the thickness of the thermal insulation and the characteristics of the waterproofing membranes did not present a noticeable effect on the resistance of the tested mock-ups. Results obtained in the experimental tests were compared to other results gathered from European technical approvals. Additionally, results were used to define the field of application of the tested systems to a National level, based on the wind loads defined in the Portuguese code and the design procedure presented in Eurocode 1 and ETAG 006.
- Mechanical performance of lap joints of flat roof waterproofing membranes subjected to artificial weatheringPublication . Gonçalves, M.; Lopes, Jorge; Brito, J. deThe flat roof of a building, here understood as the whole of every construction element from the ceiling to the surface exposed to climatic agents, is made of a set of horizontal or quasi-horizontal layers that satisfy its functional demands. The waterproofing layer is fundamental in most flat roofs and, of the various options, single-layer systems made of prefabricated membranes and mechanically fastened are one of the most frequently used in Portugal. This solution is also used to repair roofs’ waterproofing systems without having to remove the existing layers, thus reducing the cost. However, it is well known that the performance of these systems is strongly influenced by the efficiency of the membrane fastenings, which is directly related to the membranes’ nature and the design and execution of the lap joints. Many of the anomalies that occur are related to the deficient execution of the membranes’ lap joints1–3 and the consequent faulty performance when subjected to average environmental agents. Studies undertaken in Portugal on the behavior of lap joints in membranes made or commercialized in this country4,5 have corroborated other studies in this area and shown that certain membranes perform worse than others when used in single-layer systems. Three different solutions were tested: amyloid precursor protein (APP)- and Styrene-Butadiene-Styrene (SBS)-modified bituminous membranes and polyvinyl chloride (PVC) membranes. Of the bituminous membranes, the SBS ones produced and commercialized in Portugal presented, as expected, much more satisfactory mechanical characteristics than the APP ones, thus justifying a more thorough study of their suitability for use in mechanically fastened single-layer systems.
- Microstrip antenna array for multiband dedicated short range communications systemsPublication . Varum, Tiago; Matos, João; Pinho, Pedro; Abreu, Ricardo; Oliveira, Arnaldo; Lopes, JorgeDedicated Short Range Communications (DSRC) is the key enabling technology for the present and future vehicular communication for various applications, such as safety improvement and traffic jam mitigation. This paper describes the development of a microstrip antenna array for the roadside equipment of a DSRC system, whose characteristics are according with the vehicular communications standards. The proposed antenna, with circular polarization, has a wide bandwidth, enough to cover the current European DSRC 5.8 GHz band and the future 5.9 GHz band for next generation DSRC communications. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53: 2794-2796, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26394
- Dimensional stability of waterproofing bituminous sheets used in low slope roofsPublication . Lopes, Jorge; Correia, João R.; Machado, Miguel X. B.Lap joints between waterproofing bituminous sheets, applied in either single or multiple layers, are one of the most critical areas of roofs, especially when the waterproofing systems comprise only a single sheet. In fact, the way how lap joints are executed is highly associated with the occurrence of anomalies in such systems. With this regard, the dimensional stability of the sheets is one of their most important characteristics, as it that can strongly influence the performance of the lap joints and the details on roof upstands. In this context, with the aim of contributing to improve the understanding of this characteristic of bituminous sheets, the present paper presents results of an experimental study on the dimensional changes suffered by bituminous sheets when subjected to temperature variations. Different types of traditional and non-traditional sheets, with various types of bituminous mixtures (oxidised bitumen and atactic polypropylene (APP) and styrene–butadiene–styrene (SBS) modified bitumen) and reinforcements (polyester, glass fibre and polyethylene) were tested according to EN 1107-1 standard. For most of the sheets, the isolated reinforcements were also subjected to dimensional stability tests in order to evaluate their influence on the overall performance of the waterproofing layer. The results of these experimental investigations confirm that sheets with polyester reinforcement are much less stable than sheets reinforced with glass fibre. In addition, it was concluded that the influence of the type of polymer–bitumen is negligible when compared to the influence of the type of reinforcement – in general, the dimensional stability of the sheets is worse than that of the corresponding reinforcement. Finally, it is shown that the dimensional stability performance of similar products produced by different manufacturers is similar, both for the isolated reinforcements and for the waterproofing sheets.
- Mechanical performance of lap joints of flat roof waterproofing membranesPublication . Gonçalves, M.; Lopes, Jorge; Brito, J. de; Lopes, G. A.The roof is the building’s outer envelope element responsible for guaranteeing the upper tightness of the living space. Its function is complex and important since environmental agents act more directly and intensely in it than in any other envelope element. Rain, for example, has a direct impact on roofs and is capable, especially in flat roofs, of leading to dampness manifestations in buildings. Consequently, it can lead to anomalies capable of putting at risk total fulfillment of the most basic dwelling demands. Nevertheless, because flat roofs have functional and formal characteristics that in many cases recommend or even impose their choice, there is a recognizable need for discussing, clarifying, and disseminating design solutions, compositions, and construction detailing of waterproofing systems that, by using new materials and execution techniques, may lead to a good functional performance. Roofs waterproofing materials and the systems they constitute are diverse, and their classification can be established according to different criteria: functionality, raw materials nature, traditional or nontraditional character of the solution, execution technique, and bonding system to the substrate and composition.