DECIV - Artigos publicados em periódicos

URI permanente para esta coleçãohttp://www.hml.repositorio.ufop.br/handle/123456789/497

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2019 - 20202

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Autor: search.filters.author.Peixoto, Ricardo André FiorottiAssunto: search.filters.subject.Air-entraining admixture

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    Performance of lightweight concrete with expansive and air-entraining admixtures in CFST columns.
    (2020) Natalli, Juliana Fadini; Andrade, Humberto Dias; Carvalho, José Maria Franco de; Silva, Keoma Defáveri do Carmo e; Mendes, Júlia Castro; Sarmanho, Arlene Maria Cunha; Peixoto, Ricardo André Fiorotti
    Adequate load transfer in concrete-filled steel tubes (CFSTs) requires a close interaction between the steel walls and the concrete core. The present work analyzes the adhesion and confinement effects in steel tubes promoted by three types of lightweight concrete: without any admixture (reference), with an expansive agent (EA), and with an air-entraining admixture (AEA). The following tests were performed: expanding the potential of the admixtures, characterization of the hardened concretes, shear tests, axial compression with load applied to the concrete core, and axial compression applied to the mixed section. The results indicated that the dimensional variation generated by the EA induces a confinement prestress, which improves interface adhesion and, thus, the performance of the CFST. The concrete with AEA presented a lower modulus of elasticity and superficial irregularities that contributed to the manifestation of mechanic adhesion, adhesion by friction, and a high degree of confinement. Although the AEA-CFSTs presented compressive strength 2% lower than the reference, they were 10% lighter. On the other hand, the EA-CFST presented a similar density and an 8% increase in the compressive strength. In conclusion, the use of both admixtures contributed to a suitable performance of the filling cores.
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    Macroporous mortars for laying and coating.
    (2019) Mendes, Júlia Castro; Pinto, Paloma Bárbara; Silva, Henrique Emanuel Américo da; Barreto, Rodrigo Rony; Moro, Taís Kuster; Peixoto, Ricardo André Fiorotti
    The envelope of a building is responsible for its physical protection against external agents, including humidity and temperature. Thus, the present work seeks to evaluate the effect of air entraining admixtures (AEA) in mortars for laying and coating to improve their physical and thermal performances. The AEA generates macropores, interrupting the system of canaliculi that allows the capillary absorption of water. The AEA used is based on biodegradable surfactant molecules of Linear Alkyl Benzene Sodium Sulfonate. Results compare physical tests (water absorption, capillary coefficient, specific gravity, and mechanical strength), and thermal evaluation (thermal conductivity and specific heat) from two mortars mixtures with varying levels of AEA. Scanning electron microscopy (SEM) of the pore system were also analysed. All mixtures studied presented higher workability and cohesion, reduced thermal conductivity, decreased specific heat, and a reduction in the effects of water absorption, capillary elevation and specific gravity (density). In this sense, the durability of mortars to humidity effect is potentially improved, along with several other properties. Therefore, this work seeks to contribute to the quality of built environments, as well as to promote the technological development of cement-based composites.