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Percorrer por autor "Cavaco, Eduardo"

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  • Admixture tuning for high‐performance concrete for the production of novel precast pre‐stressed long‐span girders for highway overpasses
    Publication . Fernandes, Paulo; Pala, Helena; Cavaco, Eduardo; Tiago, Paulo; Júlio, Eduardo
    The improvements observed in concrete technology in the last decades, namely the production of Portland cement CEM I 52.5 R, the development of third generation super-plasticizers, and the commercialization of additions with high pozzolanic properties, turned possible the development of new concrete products using high performance concrete (HPC). Nevertheless, their implementation in the production process of the conservative precast concrete industry is not yet a reality. In this paper, the development and characterization of a HPC exhibiting high workability in the fresh state and high compressive strength in hardened state is presented. This HPC aims at producing, on a competitive basis, precast pre-stressed long-span girders for highway overpasses. For this reason, the main goal was to maximize the abovementioned properties but using the constituents available at the concrete precast company supporting the research. A set of different commercial admixtures was gathered and their influence on both compressive strength and workability of concrete was experimentally investigated. Results show that the compatibility between the admixture and the cementitious material is of paramount importance. By selecting the best type of the considered super-plasticizers and by optimizing its dosage, it was possible to increase the workability from class S1 to S5 and, simultaneously, increase the compressive strength in circa 50%, up to 120 MPa, at 28 days of age.
    2020-03-02Artigo científico Acesso aberto Ver mais
  • Flexural behavior of slender long‐span precast prestressed high‐strength concrete girders
    Publication . Fernandes, Paulo; Cavaco, Eduardo; Maranha, Paulo; Júlio, Eduardo
    The flexural behavior of slender (1/40) long-span precast high-strength concrete girders was experimentally investigated as a competing solution to steel alternatives for highway overpasses. Half-scale specimens were produced using an economical and high-strength (120 MPa) concrete mixture, non-fiber reinforced, designed only with conventional raw materials, currently available at Portuguese precast companies. Two girder specimens were subjected to quasi-static short-term loading up to structural failure in bending. Results have shown the typical behavior of conventional reinforced concrete members in bending, despite the brittle behavior of non-fiber-reinforced high strength concretes. Results also showed acceptable ductility (2.6) and the ability of the girder specimens to experience large deformation without significant softening. An analytical approach, based on plane sections and short-term stress–strain constitutive model recommended by the Eurocode 2 for concrete up to the C90/105 strength class, showed to predict accurately the behavior of girders in bending, both to ultimate and serviceability limit states, including cracking, yielding, maximum loads, and ultimate deflections.
    2021-06-30Artigo científico Acesso aberto Ver mais