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Browsing by Author "Antunes, Maria de Lurdes"

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  • Asphalt rubber mixtures in Portugal: fatigue resistance
    Publication . Miranda, Henrique; Batista, Fátima; Neves, José; Antunes, Maria de Lurdes; Fonseca, Paulo
    This paper presents a study concerning the fatigue behaviour of asphalt mixtures with bitumen modified with high content of crumb rubber used in Portugal. For assessing the fatigue behaviour of this type of mixtures, four asphalt mixtures with high content of crumb rubber were used: two field bituminous mixtures – an open-graded and a gap-graded – both with granite aggregates; and two laboratory manufactured bituminous mixtures – an open-graded mixture with granite aggregates and a gap-graded mixture with crushed gravel aggregates. Since this type of mixtures are mainly applied in wearing courses, the effect of ageing in the fatigue behaviour of one of the studied asphalt rubber mixtures was also assessed through laboratory testing. The paper presents the main results achieved so far concerning the fatigue resistance and it could be concluded that all the materials have exhibited a good behaviour, in agreement with others previous studies. In the case of the aged gap-graded material, it was observed a slight reduction on the fatigue life comparatively to the un-aged one.
    2009-05Journal article Open access Show more
  • Influence of laboratory aggregate compaction method on the particle packing of stone mastic asphalt
    Publication . Borges Miranda, Henrique; Batista, Fátima Alexandra; Antunes, Maria de Lurdes; Neves, José
    The type of aggregates and their packing characteristics under compaction are key factors for the design of asphalt mixtures with improved performance, namely, with respect to resistance to permanent deformation. A good example is Stone Mastic Asphalt (SMA), known by its stone-on-stone structure. In the U. S.A., the aggregate particles packing characteristics in a SMA, specially the stone-on-stone effect, are normally assessed using the "manually dry-rodded" method. However, this method may not be representative of field aggregate particle packing conditions, which may compromise the SMA performance. This article presents new findings regarding aggregate laboratory compaction methods to optimise the coarse aggregate structure in a SMA. Particle breakage, bulk density, air voids (compacted & uncompacted skeleton) in the aggregate / coarse aggregate were assessed for existing methods as well as for new methods using existing compactors, but with different procedures and/or specific devices, e.g. Proctor hammer. The assessed methods were: (1) "non-compaction"; (2) "manually dry-rodded" method; (3) established Proctor compaction; (4) modified Proctor compaction (light and heavy compaction) and (5) steel roller compaction. The 2 latter "new methods" aimed at mechanically simulating the dry-rodded method and the effect of field compactors, respectively. The results highlight that the new laboratory compaction methods developed with Proctor and steel roller compactor, provide a particle packing that is more representative of the field conditions, comparatively to other aggregate compaction methods.
    2020-10-30Journal article Restricted access Show more
  • Influence of the aggregate skeleton matrix and volumetric composition on the resistance of stone mastic asphalt to permanent deformation
    Publication . Borges Miranda, Henrique; Batista, Fátima Alexandra; Neves, José; Antunes, Maria de Lurdes
    The influence of different aggregate skeleton matrices, as well volumetric composition and mixture stiffness, on the resistance of SMA to permanent deformation was assessed. Nine SMA withdifferent optimised aggregate skeleton matrices, studied elsewhere, were now evaluated to permanent deformation with wheel tracking. The results were statistically analysed concerning relationship withspecimens' volumetric characteristics, Marshall properties and mixture stiffness. Aggregate skeleton optimised with the dry rodded compaction tend to produce asphalt mixtures similar to SMA designedwith pre established grading envelopes. SMA with aggregate skeleton optimised with Proctor and steel roller compaction showed higher coarse aggregates and binder contents, and thus, it is expected abetter cracking resistance and durability for the same level of resistance to permanent deformation. Statistical analysis shows that the new proposed property (ratio between binder film thickness andporosity) and, ratio between Marshall stability and flow had the best correlations with permanent deformation properties.
    2020-06Journal article Restricted access Show more
  • A new SMA mix design approach for optimisation of stone-on-stone effect
    Publication . Henrique Manuel Borges Miranda; Batista, Fátima Alexandra; Antunes, Maria de Lurdes; Neves, José
    Traditionally Stone Mastic Asphalt (SMA) is empirically designed, which could not guaranty an adequate stone-on-stone effect. To overcome this drawback, a research study was carried out having in view to develop a new SMA mix design approach for the optimisation of the stone-on-stone effect, based on new findings. To this end, the study included not only the evaluation of volumetric characteristics of SMA test specimens, but also the characteristics of coarse aggregates (CA) test specimens, prepared using different aggregate compaction methods: (i) bulk particles' specimens (compaction not applied), (ii) dry-rodded compaction, (iii) Proctor compaction and (iv) steel roller compaction. Bituminous mixtures' specimens were prepared by impact compaction using the Marshall compactor. In this context, the following test specimens' characteristics were assessed: air void content of compacted coarse aggregates (VCA), void in the coarse aggregate of compacted SMA (VCA(MIX)), air void content (porosity, Vv), voids filled with bituminous binder (VFB) and workability of nine different SMA. Results showed that pre-established grading envelopes did not allow the design or optimisation of the stone-on-stone effect. On the other hand, the new analytical mix design approach, complemented by the coarse aggregate Proctor compaction (55 blows per each layer, in a total of 5 equal layers), provides an alternative to current SMA mix design methods, since it: (i) is easy and cheap to perform, (ii) is time less consuming, and (iii) allows to obtain an air void and particle breakage more similar to the field.
    2019-04-30Journal article Restricted access Show more
  • Recomendações para a aplicação de misturas Stone Mastic Asphalt em Portugal
    Publication . Miranda, Henrique Manuel Borges; Antunes, Maria de Lurdes; Batista, Fátima Alexandra; Neves, José
    As misturas Stone Mastic Asphalt (SMA) têm adquirido nos últimos anos uma particular aceitação de destaque em Portugal, pelo bom desempenho que apresentam. Contudo, a sua utilização na rede rodoviária nacional nem sempre tem sido acompanhada de um adequado enquadramento regulatório, nomeadamente, no que concerne não só à sua caracterização final, mas também aos materiais utilizados no seu fabrico. Neste estudo apresenta-se uma sumula do âmbito de aplicação das misturas SMA, das propriedades e respetivos limites habitualmente definidos internacionalmente, para os materiais constituintes e respetivas misturas SMA, bem como recomendações relativamente à respetiva escolha para utilização em Portugal.
    2019-05Conference object Open access Show more