Navegando por Assunto "Pozolanas"

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Acesso aberto (Open Access)
Análise do potencial pozolânico da cinza de casca de arroz (CCA) através da técnica de refinamento de Rietveld
(2014-06) CORDEIRO, Luciana de Nazaré Pinheiro; MASUERO, Ângela Borges; DAL MOLIN, Denise Carpena Coitinho
Rice husk ash (RHA) is an agricultural by-product with well-known pozzolanic properties. However, the widespread commercial use of RHA is hindered by the lack of consistency between batches of this material and by the lack of quick and inexpensive quality control parameters. This study presents some basic principles for the quantification of the amorphous phases of RHA with the assumption that mineralogic characterization with X-ray diffraction can be a good quality control method for use residual or controlled ashes. The samples in this study were prepared with a lithium fluoride (LiF) standard and phase quantification was carried out using Rietveld's refinement method. The analysis of the phases was successfully conducted and results were satisfactory, with maximum relative standard deviation of 5%. These results show that quantitative analysis by Rietveld refinement can be used in the characterization of construction waste.
Acesso aberto (Open Access)
Arenito zeolítico com propriedades pozolânicas adicionadas ao cimento Portland
(Universidade Federal do Pará, 2011-08-29) PICANÇO, Marcelo de Souza; BARATA, Márcio Santos; http://lattes.cnpq.br/7450171369766897; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
The proper use of pozzolans enables the production of special cements with lower manufacturing cost and higher durability in comparison with cements without mineral additions. It also enables significant gains in productivity and extending equipments life in the fabric, limestone reserves, and also helping in the reduction of CO2 release into the atmosphere. Zeolites have been used as pozzolanic material in mixtures with Fuller’s Earth and water in buildings from the ancient Roman Empire. Nowadays, there are many discussions involving pozzolanic reactivity of natural zeolites in the incorporation of Portland cement. In the Northeastern region of Brazil, sedimentary zeolites related to sandstones of the Parnaiba Basin wer discovered by the Geological Survey of Brazil in the 2000s. These sandstones are mainly composed by quartz, natural zeolites (estilbity) and clay (smectite). Preliminary studies have pointed that this sandstone may be used as pozzolanic material in Portland cements. The material must be previously sieved to remove quartz and thermally activated, since stilbite is a zeolite with low pozzolanic activity. The main objective of this work is to advance the understanding of the factors that govern the quality and performance of Portland cement modified with this zeolitic sandstone. For this work the structure was divided into three main stages, related to three specific objectives, so that the results are presented in the form of three scientific papers, described as follow: - Evaluation of the natural pozzolanic activity of the zeolitic sandstone to be used as mineral addition in the Portland cement. - The determination of which particle size provides the highest zeolite and smectite concentration, besides the calcination temperature that leads to a higer pozzolanic activity. - The establishing of the best amount of thermally activated zeolitic sandstone to be incorporated as a mineral addition in the Portland cement. During all phases, different instrumental techniques were used for the chemical and mineralogical characterization of the starting materials and products (sandstone + lime mortar, mortar with Portland cement + sandstone + Portland cement pastes sandstone), including: spectroscopy x-ray fluorescence, x-ray diffraction, thermal analysis and scanning electron microscopy. Heat-flow calorimetru assays were carried out to evaluate the physical properties, besides mechanical testing of compressive strength of cement mortars Porltand. In the first stage of the experimental program, the zeolitic sandstone was sieved into different granulometric fractions in order to remove the inert phases (quartz and other minerals), and concentrate the zeolite for further pozzolanic assays. In the second stage, after the first characterization of the samples, we used the zeolitic sandstone that passed in the # 200 and # 325 sieves and calcined at temperatures of 150º C, 300° C and 500° C. Finally, in the third stage, # 200 fraction was calcined at 500 ° C and mixed in different proportions (10, 20 and 30%) in the mortar. The results of the first stage, which culminated in the first article showed that the zeolitic sandstone accelerated the hydration of Portland cement due to the extreme fineness of the material. The sandstone showed pozzolanic activity, and estilbite is the main responsible for this behavior. However, the reactivity was slightly lower than the minimum required to be employed as pozzolan on an industrial scale. Additional studies are needed to ascertain if the thermal treatment between 400° C and 300o C could increase the pozzolanic activity of the sandstone due to the destruction of the crystalline structure of both estilbite and smectite. For the second stage, the results showed that the # 200 fraction was the most suitable because of the higher estilbite concentration (15%) in comparison to the # 325 ssample (2%). The calcination temperature of 500º C has provided the highest pozzolanic activity due to more effective destruction of the crystalline structure of both estilbite and smectite. More moderate temperatures of 150° C and 300° C were not enough. Mortars with the 200 # sample calcined at 500 ° C reached values smaller as those required for a material to be considered as a pozzolane, in this case, 6 MPa for mortar of lime and 75% for the pozzolanic activity index (IAP). The results showed from the third stage showed that the AZ2-3 mixture (10% of zeolitic sandstone incorporated in Portland cement type CPI-S), showed the best result of compressive strength and mineralogical properties of the samples suitable for the production a commercial cement type CPII-Z. In general, one concludes that the zeolitic sandstone from northeastern Brazil has the potential feasibility of producing a CPII-Z cement, whose pozolan contents ranges from 6 to 14% in the Portland cement, according to the ABNT - NBR 11578. Although the strength of the mortar with 10% of AZ2- 3 has reached resistance values close to the reference mortar with 100% of CPI-S, further studies should be carried out in order to find better proportion of sandstone and to meet the requirements for future commercialization.
Acesso aberto (Open Access)
Atividade pozolânica de arenito zeolítico da região Nordeste do Brasil
(2012-06) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
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 size distribution that yields the highest smectite and zeolite concentration, besides the best temperature for higher pozzolanic activity. The experimental program employed the zeolitic sandstone passing through a #200 and #325 mesh sieve and calcination at the following temperatures: 150°C, 300°C and 500°C. Chemical analysis of the sieved samples was carried out by X-ray fluorescence spectroscopy and X-ray diffractometry, while mineralogical characterization was done by X-ray and thermogravimetric analysis and thermogravimetry..To assess reactivity, calorimetry driving and mechanical tests for pozzolanic activity in hydrated lime and cement Porltand were performed. The results showed that the sample sieved through at #200 mesh was the most suitable because it had a higher concentration of estilbite and a higher percentage of material seived compared to the sample sieved at #325 mesh, 15% and 2% respectively. The 500°C calcination temperature was accompanied by increased pozzolanic activity due to changes in estilbite and smectite cristalinity; the more moderate temperatures of 150°C and 300°C were not sufficient to achieve similar results. The mortars with sandstone sieved at #200 mesh and calcinated at 500°C reached the minimum limits required for a material to be considered as pozzolanic, i.e, 6 MPa for hydrated lime mortars and 75% for the pozzolanic index activity (PAI).
Acesso aberto (Open Access)
Atividade pozolânica dos resíduos cauliníticos das indústrias de mineração de caulim da Amazônia
(2011) BARATA, Márcio Santos; ANGÉLICA, Rômulo Simões
The Capim and Jari regions, northern Brazil, are the main Kaolin mining areas in the Amazon region. They encompass the biggest high-grade (high whiteness) kaolin reserves for the paper coating industry. During the beneficiation of this kaolin, different kinds of processed and non-processed wastes are generated. The main objective of this work was to evaluate the reactivity of pozolans produced after calcinations and milling of such residues, by the comparison of the mineralogical composition and the type of kaolinite from the two regions (different kinds of structural order/disorder). The heating temperature to produce the pozolans was evaluated in order to obtain the better reactivity with lower energy consumption. The results showed that the pozolans obtained from both residues exhibited high reactivity, also better than those commercially available. Those obtained from kaolinites with high structural defects needed lower temperatures in comparison with low-defects kaolinites. The use of the former kaolinites reduces the production costs to obtain pozolans without losing quality in terms of reactivity.
Acesso aberto (Open Access)
Avaliação preliminar do emprego de arenito zeolítico da região nordeste do Brasil como material pozolânico para cimento Portland
(2011-12) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
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 Parnaíba 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 ºC to convert to the amorphous phase metakaolin in order to be used as one of the most commons pozzolans in the cement industry. The main purpose was to contribute for the production of an alternative kind of cement which produces less pollution to the environment (CO2 decrease in the atmosphere) with cost saving. In addition, it is expected to contribute for the exploitation of the sedimentary zeolites occurrences which have been relatively well studied from a geological point, but are still not mined.
Acesso aberto (Open Access)
Caracterização dos resíduos cauliníticos das indústrias de mineração de caulim da Amazônia como matéria-prima para produção de pozolanas de alta reatividade
(2012-03) BARATA, Márcio Santos; ANGÉLICA, Rômulo Simões
Capim and Jari are the two most important kaolin mining districts of the Brazilian Amazon region. They encompass the major Brazilian reserves of high quality kaolin for the paper coating industry. The kaolin is mined and processed by three major companies responsible for about 500,000 ton of a residue mainly composed of kaolinite. The wastes come mainly from the centrifugation phase of the kaolin beneficiation process and their final destinations are huge sedimentation basins that occupy large areas. The main purpose of this work is to evaluate the physical, chemical and mineralogical characteristics of the kaolin wastes processed from the Capim and Jari region, in order to obtain metakaolinite, a high reactive pozzolan for the cement industry. When incorporated to ordinary Portland cement such pozzolans increases the concrete and mortars performance. All the residues studied in this work were characterized by means of: X-ray diffraction analysis, differential thermal analysis, infrared spectroscopy, scanning electron microscopy, X-ray fluorescence spectrometry and laser diffraction. Both residues are mainly constitutes by at least 92% of low granulometry kaolinite with specific surface area above 8 m2/g and mean diameter below 1 µm. Free silica (quartz) contents are below 3%. The high concentration of kaolinite in these residues dispenses rigid control parameters for removal of impurities usually employed in pozzolan production. The Jari kaolin exhibits high disordered kaolinite in comparison with the high ordered kaolinite of the Capim region and gives rise to higher desidroxilation degree at lower temperatures. It points to energy saving and reducing costs during the production of a pozzolan. The results are satisfactory and reveal that both kaolin wastes are excellent raw material for the production of high reactive metakaolin.
Acesso aberto (Open Access)
Cimentos Portland aditivados com arenito zeolítico com propriedades pozolânicas
(2014-06) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
The proper use of pozzolans enables the production of special cements with lower manufacturing cost and higher durability in comparison with cements without mineral additions. It also enables significant gains in productivity and in equipment service life in the factory as well as reduce the CO2 emission into the atmosphere. Zeolites have been used as pozzolanic material in mixtures with Fuller's Earth and water in buildings from the ancient Roman Empire. Nowadays, there are many discussions involving pozzolanic reactivity of natural zeolites in the incorporation to Portland cement. In the Northeastern region of Brazil, sedimentary zeolites related to sandstones of the Parnaiba Basin were discovered by the Geological Survey of Brazil in the 2000s. These sandstones are mainly composed by quartz, natural zeolites (estilbity) and clay (smectite). Preliminary studies have pointed that this sandstone may be used as pozzolanic material in Portland cements. The material must be previously grinded to remove quartz and thermally activated, since stilbite is a zeolite with low pozzolanic activity. The aim of this study was to evaluate the ideal amount of thermally activated zeolitic sandstone to be incorporated in the Portland cement in order to improve its mechanical and mineralogical properties. In the laboratory, the < # 200 fraction of the zeolitic sandstone was calcined at 500 º C. Chemical and miner-alogical analysis were carried out by X-ray fluorescence spectroscopy (XRF) and X-ray Diffractometry (XRD), respectively. The hydration behavior of the cements was evaluated using heat-flow calorimetry, besides thermal analysis and XRD. To evaluate the physical properties, mechanical testing of compressive strength in cement mortar Portland with different proportions of sandstone was carried out. The results showed that the AZ2-3 zeolitic sandstone with the proportion of 10% incorporated in Portland cement type CPI-S, showed the best result of compressive strength and mineralogical properties of the samples suitable for the production of CPII-Z type commercial cement.
Acesso aberto (Open Access)
Estudo de parâmetros físicoquímicos para a produção de argamassas utilizando resíduos industriais e da construção civil
(Universidade Federal do Pará, 2014-02-26) FERREIRA, Keylla Castro; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
The mortas can be considered as a mixture of the binders and aggregates with water, having capacity of the induration and adherence. Instead, it is suggested the production of mortas using civil construction waste, with plenty silicoaluminates, obtained in demolitions and reforms of build, and fly ash as material pozzolana, obtained of the combustion of mineral coal in fluidized bed boilers, in partial replacement of Portland cement. The civil construction wastes were benefited and characterized by X-ray spectrometry and X-ray diffraction. The fly ash was characterized by granulometric analyze and X-ray spectrometry. The mortars of the were prepared using the following compositions of RCC, 95, 90, 85, 80, 75 and 70%; CV of 0, 5, 10, 15, 20 and 25% e 5% of Portland CP II Z 32 cement. In all the compositions were put 0,8% of water and the rheological testing was used the same proportions residue (RCC e CV) with 35% water. The specimens were cured for 28 days and after were submitted physical trials of absorption, porosity and bulk density; mechanical trials of resistance to compression and analysis of X-ray diffraction and scanning electron microscopy. The results obtained show that the recycling of civil construction waste and the use of fly ash and RCC is a promising technique in production of mortas.