Browsing by Author "Andrade, Humberto Dias"

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    Carbonatação em concreto de escória de aciaria.
    (2018) Andrade, Humberto Dias; Peixoto, Ricardo André Fiorotti; Peixoto, Ricardo André Fiorotti; Silva, Guilherme Jorge Brigolini; Bezerra, Augusto Cesar da Silva
    A utilização de materiais alternativos na produção de matrizes cimentícias se tornou uma necessidade, visto que, por um lado, há uma grande demanda do setor de construção por materiais naturais, e por outro, a necessidade de se promover destinação adequada de uma gama de resíduos industriais, cuja geração é crescente. No entanto, as matrizes alternativas devem apresentar desempenho similar às convencionais, dessa forma, vários testes devem ser realizados, afim de se atestar a qualidade desses materiais. Na presente pesquisa, concretos estruturais produzidos com substituição total dos agregados convencionais por agregados de escória de aciaria foram avaliados, sendo que o desempenho mecânico e de durabilidade desses produtos foram verificados. A carbonatação do concreto exposto a atmosferas naturais, é um processo lento, mas os resultados para décadas de utilização precisam ser estimados em tempo viável e com boa confiabilidade. Dessa forma, testes acelerados utilizando atmosferas com alta concentração de CO2 vêm sendo propostos. Este trabalho vem contribuir para o entendimento da carbonatação de concretos produzidos com 100% de substituição de escória de aciaria, por meio da realização de ensaios acelerados. Adicionalmente, a velocidade de pulso ultrassônico e a resistência mecânica desses concretos foram avaliadas, e a relação desses parâmetros com o grau de carbonatação inferida.
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    Mechanical and durability performance of concretes produced with steel slag aggregate and mineral admixtures.
    (2022) Costa, Laís Cristina Barbosa; Nogueira, Marcela Aguiar; Andrade, Humberto Dias; Carvalho, José Maria Franco de; Elói, Fernanda Pereira da Fonseca; Brigolini, Guilherme Jorge; Peixoto, Ricardo André Fiorotti
    The steel slag is a residue for the steel industry that is already applied in many cement-based composites, although there is a lack of studies on the durability of this material in aggressive environments. This work evaluated the durability against chloride attack of concrete produced using steel slag as aggregate and mineral admixture, called steel slag powder. For comparison purposes, reference concretes using conventional aggregates and commercial mineral admixtures (silica fume and metakaolin) were produced. The concretes produced with steel slag aggregates and steel slag powder had lower chloride penetration depths compared to conventional ones. The steel slag powder presented an ability similar to silica fume of forming Friedel salt. The concrete produced with steel slag aggregates also presented a smaller water absorption and a higher compressive/tensile strength compared to the reference one. In general, this research observed that steel slag concretes are techni- cally feasible options for the construction sector.
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    Mechanical performance and resistance to carbonation of steel slag reinforced concrete.
    (2021) Andrade, Humberto Dias; Carvalho, José Maria Franco de; Costa, Laís Cristina Barbosa; Elói, Fernanda Pereira da Fonseca; Silva, Keoma Defáveri do Carmo e; Peixoto, Ricardo André Fiorotti
    The use of residues as alternative materials in the production of cement-based composites is significantly growing since it embraces the circular economy concepts. This alternative reduces the demand for nat- ural resources by the construction sector and provides a proper destination for a range of industrial resi- dues. However, the alternative materials must perform properly for safe applications. In this way, the steel slag, a residue of the steel industry, stands out. The steel slag is already applied in some cement- based composites showing enhancement in the mechanical performance, although its durability is barely evaluated. So, this research produced eco-friendly structural concretes of three compressive strength classes and for similar application parameters. The evaluations were performed in concretes with total replacement of conventional aggregates by steel slag aggregates, containing no chemical admixtures and in the presence of a PCE-based superplasticizer. The mechanical performance and resistance to car- bonation of these products were evaluated. An accelerated carbonation test was proposed and adopted to better understand the carbonation phenomenon within the research timeframe. The steel slag concretes presented higher compressive strengths and reductions in carbonation depths up to 60% compared to conventional ones. These results corroborate the technical feasibility of applying steel slag as aggregates in cement-based composites.
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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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    Reuse of iron ore tailings from tailings dams as pigment for sustainable paints.
    (2018) Galvão, José Lucas Barros; Andrade, Humberto Dias; Brigolini, Guilherme Jorge; Peixoto, Ricardo André Fiorotti; Mendes, Júlia Castro
    In order to minimise the environmental, social and economic impacts caused by the mining activity, this work proposes the use of iron ore tailings from tailings dams (IOT) as pigment in the production of a paint for buildings e the Sustainable Paint. The waste originates from the mining activity in the state of Minas Gerais. For this work, it was used in its raw state, subjected only to drying and lump breaking. In addition to IOT and water, four types of binders were tested: polyvinyl acetate (PVA) resin (in the form of ordinary white glue), acrylic resin, hydrated lime for painting and high early strength Portland cement. Binder contents ranged from 0% to 50% over the mass of IOT. For the evaluation of the mixtures, four main parameters were used: cost, colour homogeneity, abrasion resistance, and durability to external exposure, using the colour difference methodology DE (Delta-E). The results of binder evaluations were compared among themselves and with conventional paints from a brand recognised by the Brazilian Association of Paint Manufacturers. The Sustainable Paint presented reddish colour; suitable opacity; satisfactory results regarding durability at a significantly lower cost. In general, the blends with IOT, especially those using PVA as binder, have proved to be promising alternatives for paintings prepared in situ. It is noticeable the wide potential of use of this pigment by communities affected by iron ore tailings dams throughout Brazil and worldwide.
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    Steel slags in cement-based composites : an ultimate review on characterization, applications and performance.
    (2021) Martins, Ana Carolina Pereira; Carvalho, José Maria Franco de; Costa, Laís Cristina Barbosa; Andrade, Humberto Dias; Melo, Tainá Varela de; Ribeiro, José Carlos Lopes; Pedroti, Leonardo Gonçalves; Peixoto, Ricardo André Fiorotti
    Steel slags are by-products generated in high volumes in the steel industry. Their main constituents are calcium, silicon, ferric, aluminum, and magnesium oxides. Larnite, alite, brownmillerite, and ferrite are also found. The presence of expansive compounds cause concern when used in cement-based compos- ites; however, mitigating routes have been proposed. Activation techniques improve the binding proper- ties of steel slag powder, potentiating its use as a supplementary cementitious material (SCM). As an aggregate, steel slag presents good morphological and mechanical properties. Promising mechanical and durability performances in cement-based composites encourage further research to promote the use of steel slag.