Navegando por Assunto "Cimento"

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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)
Argamassa autonivelante para contrapiso: efeito do tipo de cimento no comportamento físico-mecânico
(Universidade Federal do Pará, 2020-04-24) ALVES, Brenda Maiara Oliveira; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
Self-leveling mortar (SLM) is inserted in the construction market as an innovative product due to its special properties when compared to conventional mortars due to the filling of empty spaces and self-compacting only under the effect of gravity, the ability to flow and level without the occurrence of segregation. The use of CP V – ARI cement is common for its production, since its high fineness favors the fluidity of the material and for providing fast hardening, fundamental characteristics that must be considered in self-leveling mortars (SLM’s). However, the rare availability of this type of cement becomes a limiting factor for its applicability in the region. Therefore, the objective of this research is to develop the study of SLM dosage for screed, adapting it to local materials that favor its design and evaluating its influence on rheological and mechanical characteristics. For the production of these mortars, we used the adaptation by Lopes et al. (2018) of Tutikian's methodology (2004) for self-compacting concrete (CAA), using fines in partial replacement of cement, adopting as controllable factors the type of cement (CP I, CP II-E, CP IV and CP V-ARI) and the type of mineral addition (silica fume and metakaolin). For the characterization of SLM in the fresh state, the mini slump, mini V-funnel, flow retention, mass density and incorporated air content, determination of exudation and healing time tests were performed. In the hardened state, the mechanical resistance to compression and traction in flexion and the retraction of these materials were verified, since it is one of the main pathologies of SLM. Analyzing the results obtained, it was observed that the surface area of the tested cements was the factor that most influenced the performance of the produced mortars, where cements with larger surface areas needed more additive to achieve fresh properties and had the highest rates of retraction. Mineral additions contributed to the cohesion of mortars and reduced shrinkage in mixtures with contents of up to 25% metakaolin and 15% silica fume.
Acesso aberto (Open Access)
Captura de carbono em placas de concreto permeável
(Universidade Federal do Pará, 2020-06-12) SANTOS, Caio José Bastos Marques; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
The production of cement has an impact on the environment from the release of co2 where carbon dioxide acts directly on the phenomenon of "greenhouse effect". Although cement production generates high rates of carbon dioxide, cement hydration products have the ability to reabsorb carbon dioxide from a physical-chemical phenomenon called carbonation. This research related this physical-chemical phenomenon to a material considered sustainable, such as permeable concrete. This type of concrete can be used on non-reinforced floors. The research focuses on analyzing the ability to capture co2in permeable concrete slabs. As for carbonation, mixtures produced with two granulometric bands of pebble and CP II F agglomerate with a/c ratios of 0.33 and 0.37 were analyzed in protected and unprotected environments, and in an accelerated environment in a co2 chamber. A chemical phenolphthalein indicator was used to assess the occurrence of carbonation in five ages of reading and image analysis software to study the carbonated surfaces. The material showed satisfactory results in terms of mechanical, water and carbonation depth parameters, having reabsorbed the atmosphere gas from the cement paste that surrounds the aggregate grains of the material's granular skeleton.
Acesso aberto (Open Access)
Emprego de Resíduo de Silício Metálico como Material Pozolânico na Produção de Cimento Portland Composto
(Universidade Federal do Pará, 2022-12-19) CUNHA, Rodrigo Rodrigues da; MACEDO, Alcebíades Negrão; http://lattes.cnpq.br/8313864897400179
Civil construction, despite being an extremely important sector for the country's economic development, consumes a very significant amount of natural raw materials, in addition to being responsible for most of the consumption of cement produced in the world. The production of this material, in turn, causes many environmental impacts, resulting mainly from the sintering stage of clinker (main constituent of cement), which causes the emission of thousands of tons of CO2 into the atmosphere. In this sense, several studies have been carried out in order to point out an alternative material that can be used as a mineral addition to cement instead of clinker. Much of this research has sought to study the use of additions manufactured from the use of industrial waste. Given this context, the present work aims to analyze the behavior of a modified Portland cement of the CPIIZ-32 type, produced with partial replacement of clinker, by a residue from the pre-separator of the ferrosilicon - metallic silicon manufacturing process. - from an industry located in Breu Branco/PA. Therefore, at first, the physical and chemical characterization of the residue in natura and processed form was carried out, through the milling process, from the specific mass, FR-X, DR-X and activity index tests. pozzolanic with lime and cement. Then, 5 (five) blends of composite cement were formulated with different contents of ground silicon metal residue to analyze the mechanical behavior at 28 and 90 days of curing. Finally, a comparison was made of the physical-mechanical performance of the mortars produced with the use of modified cement and commercial cement of the CPIIZ-32 type. The results showed that the metallic silicon residue, after going through a pre-benefiting process (grinding for a period of 60 minutes) obtains properties consistent with the requirements stipulated by NBR 12653 (ABNT, 2014) to be considered as a pozzolanic addition. The use of this by-product for this purpose can generate enormous environmental benefits, reducing the impacts resulting from the clinker production stages, as well as being a viable alternative for the reverse logistics of this material, since the generating companies still do not have any form of reuse for this residue.
Acesso aberto (Open Access)
Estudo de aproveitamento do resíduo do beneficiamento de caulim como matéria prima na produção de pozolanas para cimentos compostos e pozolânicos
(Universidade Federal do Pará, 2004-01-16) LIMA, Jefferson Maia; CARNEIRO, Arnaldo Manoel Pereira; http://lattes.cnpq.br/9191655335324358
The use of residue in civil construction can to become a activity of extreme important and more frequent, mainly due to amount available with potential of recycling, possible reduction of environments impacts. The kaolin industries produces two type of residue. The residue contain clay mineral kaulinite show potentially of is to employ by pozzolanas at the construction civil industry. This research evaluates the technical viability to production of pozzolanas from mixtures in various percentagens of kaulinitic residue with limestone, wanting increase the reactivity. The contents of replacement of cement for pozzolanas is of 10%, 20%, 30%, 40%, 50% e 60% was studied. The cement employed was CP I S 32 and the pozolanas was made in the laboratory. The following tests in the experiment cements were carried out: specific gravity, specific surface area, water of normal consistency, setting time and compressive strength. Also, were carried out mineralogical tests in the pozolanas. The incorporation of pozzolanas allowed to mortar obtain compressive strengths more than it reference even though in high contents. Due to the pozzolanas show a considerable hydraulic characteristic this it occurred. It waits of residue burned becomes a higher pozzolana to employ at the civil construction, mainly along with cement, mortars and concretes in the substitution of burning clays from natural deposits despite necessity of adding tests for confirmation and complementation of effects was observed.
Acesso aberto (Open Access)
Preparation of refractory calcium aluminate cement using the sonochemical process
(2013-08) LOURENÇO, Rafaela Roberta; ANGÉLICA, Rômulo Simões; RODRIGUES, José de Anchieta
Calcium aluminate cements (CAC) were prepared using the sonochemical process, followed by heat treatment. A study was made of the action of ultrasonic waves and the influence of thermal treatment conditions on two initial molar compositions of 1:1 and 1:2 of calcia:alumina. The aqueous suspension containing the raw materials (A-50 alumina and CaO) was subjected to an ultrasonic bath, followed by drying and burning at 1000, 1200 and 1300 ºC. These cements were characterized by SEM, XRD and the mechanical strength was evaluated by splitting tensile tests, using commercial cement as a reference. Furthermore, the phases were semi-quantified using the Rietveld method. The results show that hydration and sonochemical action increased the reactivity of the raw materials during firing and that phase formation is dependent on the thermal treatment conditions. The CAC cements were obtained at temperatures at least 200 ºC lower than those used in conventional methods, indicating the potential of this route of synthesis.
Acesso aberto (Open Access)
Uso de resíduo caulins da amazônia para a produção de precursores geopoliméricos utilizados na indústria da construção civil
(Universidade Federal do Pará, 2024-04-25) BRITO, Woshington da Silva; BRAGA, Eduardo de Magalhães; http://lattes.cnpq.br/4783553888547500; https://orcid.org/0000-0003-0739-7592; SOUZA, Jose Antonio da Silva; http://lattes.cnpq.br/6157348947425968
The region of the Capim River (Northeast of the State of Pará), due to its large reserves of kaolin for covering paper, stands out nationally. The extraction of the ore occurs on average at a depth of 20 meters, covered by clayey-sandy sediments from the barrier formation, and from a level of hard kaolin, also known as flint or semi-flint kaolin(Ferruginous), considered stable depending on the content high iron content, which makes its application for roofing unfeasible. The research aims to address the development of geopolymers synthesized from waste containing aluminum silicate. Geopolymers are amorphous, threedimensional alkalis. Aluminosilicate binder materials synthesized from alkaline activation of clays, calcined clays, calcined kaolin, minerals, industrial waste, fly ash and other aluminosilicates. The fly ash generated in the Bayer process boilers under conditions of 900 °C and 120KPa was also used as a source of aluminosilicate in the geopolymerization reaction. To increase the reactivity of the reaction, the use of soft kaolin and flint and semi-flint(ferruginous) kaolin calcined at different temperatures(450,550,650, 700 and 800 °C) was evaluated. And, also at different calcination times(15,30,60 ,90 and 120 minutes). Sodium hydroxide (NaOH, 5-30 M) and sodium silicate (Na2SiO3, SiO2/Na2O = 3.2) as alkaline reaction medium. The residues were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). And, compressive strength tests were also carried out on the geopolymeric samples to evaluate the degree of polymerization, since the more polymerized the structure is, the greater the resistance. For the geopolymer based on (soft kaolin and fly ash), the best results were obtained for the SiO2/Al2O3 ratio of 2.65 and 3.4. For the geopolymer based on (flint kaolin and fly ash) the best result was for the SiO2/Al2O3 ratio of 2.95 and 3.57. The best results for the geopolymers based on (ferruginous metakaolin and fly ash) were obtained with a SiO2/Al2O3 ratio of 2.88 and 3.54. The geopolymeric ceramic plate obtained showed satisfactory performance in relation to mechanical resistance to compression and was also synthesized with raw material that contaminates the environment, as it is considered kaolin residue due to its high iron content.