Marcelo de Souza Picanço

Behavior of cement mortar reinforced with Amazonian fibers subjected to compression

In recent years, there has been intense research worldwide for alternative materials to substitute asbestos fiber, a component of asbestos cement, which has been found to be hazardous to human and animal health and has been banned in many countries. Since 1979 the Non-conventional Materials Research Group of PUC-Rio has carried out research on the application of vegetable fibers, available in abundance in Brazil, for the fabrication of construction components, aiming mainly at the fabrication of popular housing. The Curaua fiber has been studied, as it is already of popular use in the manufacture of ropes, baskets and carpets in the region, known as Baixo Amazonas, in the state of Para, Brazil, where the first plantations have been organized on a commercial scale. In this work, mechanical properties of the Curaua fiber, as well as their application as a cementicious matrix reinforcement, have been studied. The performance of Curaua fiber and its composites was compared with other vegetable fibers, such as sisal and jute, as a substitute for asbestos fiber and its composites. The data on sisal fibres from previous works by the same research group at PUC-Rio was considered for comparison. The behavior of jute fiber, as well as cementicious composites, reinforced with jute and sisal fibers, has also been studied in this work. The results have shown that the Curaua fiber has appropriate physical and mechanical characteristics that make it suitable to be used as reinforcement of cementicious matrixes, with a high ductility and post-cracking resistance capacity.

Atividade pozolânica de arenito zeolítico da região Nordeste do Brasil

In northeastern Brazil, sedimentary zeolites occur associated with sandstones of the Corda Formation (Parnaiba Paleozoic Basin), discovered in the 2000s. These sandstones are composed of quartz, natural zeolites (estilbite) and clay minerals (smectite). Preliminary studies have shown that this sandstone can be used as a pozzolanic material in Portland-cement-based systems after the material has been sieved to remove the quartz and after thermal activation because the estilbite has low pozzolanic activity. The main objective of this study was to determine the best particle

Avaliação do módulo de elasticidade em concreto com metacaulim de alta reatividade, proveniente de rejeito industrial

As adicoes minerais sao empregadas no concreto com o objetivo de melhorar algumas de suas propriedades mecânicas, bem como a sua durabilidade. Atualmente, tem-se cada vez mais adotado o uso de pozolanas de alta reatividade como ferramenta para obtencao do concreto de alta resistencia (CAR). O metacaulim de alta reatividade (MCAR) e oriundo do processo de calcinacao em temperaturas entre 400oC e 950oC e posterior processo de moagem de argilas com altos teores de caulinita, como a argila caulinitica e o caulim. O objetivo principal deste trabalho foi avaliar o uso do (MCAR) no concreto, visando verificar a sua influencia no modulo de elasticidade do concreto. Para a obtencao desta adicao mineral adotou-se como materia-prima o rejeito proveniente da industria do papel, que apos um processo de calcinacao e moagem, transforma-se no MCAR. Para a realizacao deste trabalho variou-se os teores de substituicoes de MCAR, as relacoes agua/cimento e as idades de rompimento dos corpos-de-prova. A metodologia utilizada foi baseada em ensaios laboratoriais e no uso de ferramentas estatisticas para validacao dos resultados. O estudo indicou que o efeito isolado das variaveis controladas e algumas interacoes entre essas variaveis influenciam nesta propriedade. Dentre esses efeitos isolados, constatou-se que as variacoes das porcentagens de MCAR de 0 a 20% resultam em acrescimos de ate 9% no valor obtido no ensaio de modulo de elasticidade do concreto.

Avaliação preliminar do emprego de arenito zeolítico da região nordeste do Brasil como material pozolânico para cimento Portland

Natural zeolites usually exhibit pozzolanic activity without any additional treatment, e.g. thermal activation. They have been used for building since the ancient Roman Empire times in the production of hydraulic cements and concretes. Nowadays, there are many discussions involving the natural zeolites pozzolanic reactivity in the incorporation of the Portland cement composition. The appropriate use of pozzolans enables the production of special cements with lower manufacturing cost and with a greater durability in comparison with the corresponding cements without addition. In Brazil, zeolite consumption comes either from the importation of foreign countries or synthetic products. No zeolite mine is available in the country and only few geological occurrences were already described in the literature without any commercial interest. In northeast Brazil, the Geological Survey (CPRM) discovered zeolite-bearing sandstones related to Cretaceous sedimentary rocks of the Parnaiba Paleozoic Basin. The main purpose of this paper is to evaluate the possible use of such sandstones as pozzolan for using in Portland cements (CPI-S). A bulk sample of the zeolitic sandstone (AZ) was collected in the field. In the laboratory, preparation included drying, milling and sieving at the following grain-size fractions, in order to remove quartz and concentrate the zeolite: 100# (AZ-1), 200# (AZ-2) and 325# (AZ-3). After mineralogical evaluation, the AZ-2 fraction was selected for further analysis and assays. The experimental study was mainly based on mineralogical characterization, including: X-ray diffraction (XRD), chemical analysis and heat flow calorimetry, besides pozzolanic activity assay and compressive strength. The results show that the mineralogical composition of the zeolitic sandstone is mainly quartz, zeolite (stilbite) and smectite. Stilbite is the main pozzolanic phase, and the smectite can also play an important role. The hydration of the Portland cement was accelerated due to the very fine grained nature of the material. Meanwhile, the reactivity obtained was slightly below the standard requirements to be used in industrial scale. Additional studies should be carried out in order to evaluate if a further thermal treatment (between 300 °C and 500 °C) may increase the pozzolanic activity due to the stilbite destruction around this temperature. The same happens with kaolinite that needs thermal treatment above 550 o

Reinforced concrete ribbed slabs with wide-beam

Resumo Ribbed slabs have been widely used in buildings due to their many advantages, especially the decrease of concrete below the neutral line. This paper presents an experimental and computational study on ribbed slabs with wide-beam, two one-way slabs and two two-way slabs, with variable depths were tested to evaluate their resistance to punching and shear strength of slabs. Experimental and computational results showed that the wide-beam ribs connection is a critical point in the design of the slabs due to the difference in stiffness in the transition zone. Best results for the ultimate load estimates for ribs were provided by EC 2 (2004), while estimates of ACI 318 (2008) and NBR 6118 (2014) were respectively conservative and unsafe. Test results on slabs also revealed that the Brazilian alternative to analysis ribbed slabs as solid ones failed to give satisfactory results.

Resposta à flexão e análise de tenacidade de argamassas reforçadas com fibra de Curauá

The composites material produced from natural fibers development and commercialization are considered extremely important because these fibers will reduce the material produced with non-renewable resources dependence. Among these fibers, there is the Curaua fiber, its use in composites production improves the ensemble matrice fiber properties, then this article aims to study the composites reinforced with Curaua fibers mechanical properties, especially its bending resistance and toughness. For achieve those objectives, it was produced five mortar groups, one for reference, without the fiber utilization, and another four groups with fiber reinforcement varying the fiber length and its volume fraction. It was noted that Curaua fiber, when added to cement matrice, improves its mechanical properties compared to a composite without the fiber reinforcement, its deflection, bending resistance and toughness are improved.