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- Influence of laboratory aggregate compaction method on the particle packing of stone mastic asphaltPublication . Borges Miranda, Henrique; Batista, Fátima Alexandra; Antunes, Maria de Lurdes; Neves, JoséThe 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.
- Recomendações para a aplicação de misturas Stone Mastic Asphalt em PortugalPublication . Miranda, Henrique Manuel Borges; Antunes, Maria de Lurdes; Batista, Fátima Alexandra; Neves, JoséAs 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.
- A new SMA mix design approach for optimisation of stone-on-stone effectPublication . Henrique Manuel Borges Miranda; Batista, Fátima Alexandra; Antunes, Maria de Lurdes; Neves, JoséTraditionally 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.
- A contribution for a sustainable, resilient road infrastructure management from Brisa, a Portuguese Road ConcessionairePublication . Vieira, Carina; Correia, Eugénia; Domingues, Daniela; Rato, Maria João; Caetano, Fernanda; Borges Miranda, Henrique; Carvalho, ManuelaNowadays, there are increasingly efforts to introduce an economy based on circularity principles, but there is still a gap between the intentions and the actual measures to achieve it. In Portugal, reclaimed asphalt is generally used as granular material for unbound road layers or reused mainly as asphalt mix in the municipal road network, instead of reusing this premium material in new asphalt mixes for medium/heavy traffic, mainly due to the lack of knowledge on how to use these materials without compromising the performance or durability of the pavement. The purpose of this study is therefore to evaluate the technological suitability of using two different rejuvenator additives (rejuvenator solid additive and terminal blend bitumen with rejuvenating additive) for use with highly aged reclaimed asphalt (RA) in the production of new asphalt mixtures for motorway surface courses. To achieve this objective, three gap graded asphalt mixtures (one of reference) for surface course were produced with 20% highly aged reclaimed asphalt milled from Brisa's motorway network. The results show that asphalt mixtures with reclaimed asphalt had better performance (water sensitivity, resistance to permanent deformation) and similar surface properties compared to reference asphalt mixture (without RA), regardless of the rejuvenator additive used. Further studies will consider pavement monitoring the asphalt mixtures studied as well as mixtures with other rejuvenator additives in order to expand the possibilities of using reclaimed asphalt in Portugal.
- Pavimentos sustentáveis com incorporação de plásticos recicladosPublication . Rato, Maria João; Domingues, Daniela; Borges Miranda, Henrique; Antunes, VítorOs resíduos de plástico apresentam-se como um desafio ambiental significativo e crescente, incluindo desde plásticos industriais, sacos de plástico, embalagens para alimentos, entre outros. Em resposta à crescente preocupação, tem havido um progressivo interesse na incorporação destes resíduos em outras aplicações, nomeadamente, a incorporação de resíduos de plástico reciclado em materiais de construção. Mas será a sua utilização viável na pavimentação rodoviária? Os resultados obtidos são encorajadores, permitindo constatar para diferentes tipos de aditivos de plásticos reciclados disponíveis no mercado uma melhoria do comportamento dos ligantes betuminosos e sua interligação com os agregados.
- Influence of the aggregate skeleton matrix and volumetric composition on the resistance of stone mastic asphalt to permanent deformationPublication . Borges Miranda, Henrique; Batista, Fátima Alexandra; Neves, José; Antunes, Maria de LurdesThe 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.
- Influence of recycled plastics on the mechanical behaviour of bituminous mistures for highway surface layersPublication . Borges Miranda, Henrique; Domingues, D.; Rato, M. J.Europe is one of the largest producers of plastics in the world, with an annual turnover of over 350 billion euros, making it a strategic industrial sector as the global consumption of plastics increases. However, plastic is nowadays considered a serious environmental problem as it represents a large share of the world’s waste generation, with Europe being one of the largest sources of plastic waste exports. Therefore, the transition to a circular economy for plastics must be driven by Europe in order not to jeopardize the economic and environmental future of the plastics sector on the continent. Thus, it is crucial to investigate the feasibility of using recycled plastics in different applications, especially in the three main end-use markets for plastics (packaging, construction and automotive). In the construction sector, the use of plastics in road and highway construction and rehabilitation is currently being investigated due to the high potential for high-value applications and high raw material consumption. However, more knowledge is needed to make recycled plastic a common solution for road surfacing. The current study was promoted by BRISA, which was ranked the most sustainable highway operator in Europe for the third time in 2021. It aims to contribute to European efforts to investigate the feasibility (ongoing study: mechanical, functional, and environmental laboratory and field evaluation) of using recycled plastic in the production of bituminous mixtures for highway pavements in Portugal, without limiting the recyclability of bituminous mixtures. The present work focuses on the influence of recycled plastics on the water sensitivity and deformation susceptibility of bituminous mixtures under load. To perform the experimental study, the following materials were used: two bituminous mixtures with different types of coarse and fine aggregates (granodiorites and granites); a bitumen (PMB 45/80-65); a filler (limestone); and five recycled plastic additives (mainly consisting of LDPE, HDPE, LLDPE and PP, which represent about 50% of the plastics produced in Europe). The results were statistically analysed together with results of other studies on the volumetric and Marshall properties of the specimens. The results show an overall improvement in resistance to permanent deformation, without a significant benefit in water resistance. However, efforts to validate performance regarding fatigue, ageing resistance, pollutant emissions during production, placement and in service pavements are ongoing. In the statistical analysis, the ratio between binder film thickness and porosity (BFT/Vv) showed a statistically significant strong correlation with the performance indicators for resistance to permanent deformation.