Viabilidade tecnica da producao de blocos silico-calcarios na regiao de Santa Maria, no Rio Grande do Sul

Este trabalho é camposto por dois estudos basicamente: um estudo teórico sobre os blocos sílico-calcários de areia-cal e um estudo prático sobre a viabilidade técnica de produção destes blocos em uma região determinada. A pesquisa teórica procurou elucidar o que vem a ser um bloco síilico-calcário, buscando a viabilidade da pesquisa prática e os pontos principais a serem abordados. Foram estudados, nesta parte, as matérias-primas e o processo produtivo empregado na confecção destes elementos, mostrando a importância de cada item para as características do produto final. Foi dada atenção ainda às características técnicas, aos fatores que determinam a produção e emprego e aos aspectos positivos e negativos dos elementos deste tipo produzido em outros locais. A pesquisa prática buscou a disponibilidade de matéria-prima conveniente para a produção de blocos sílicos-calcários, e o efeito das variações do processo produtivo sobre os produtos confeccionados com os materiais estudados. A matéria-prima empregada foi uma areia quartzosa da região de Santa Maria-RS, cal calcítica virgem de São Sepé-RS, e cinza volante da termoelétrica Presidente Médici, em Bagé-RS, fazendo-se variações nas percentagens destes componentes. As variações do processo produtivo foram efetuadas no tipo de moldagem dos corpos de prova, em que foi usada pressão, vibração e vibro-compressão, e na pressão de autoclavagem. Para todas as variações efetuadas foram obtidas as seguintes características: variações por autoclavagem, massa específica aparente, absorção d´água, resistência à compressão, resistência à tração e módulo de elasticidade à compressão, as quais foram relacionadas através de quadros e figuras às diversas variações.

Estudo e caracterização de matérias-primas para o desenvolvimento de blocos sílico-calcários

The types of products manufactured calcium silicate blocks are very diversified in its characteristics. They include accessory bricks, blocks, products in dense material, with or without reinforcements of hardware, great units in cellular material, and thermal insulating products. The elements calcium silicate are of great use in the prefabricated construction, being formed for dense masses and hardened by autoclaving. This work has for objective develop formulations that make possible the obtaining of calcium silicate blocks with characteristics that correspond the specifications technical, in the State of the Rio Grande of the North, in finality of obtaining technical viability for use in the civil construction. The work studied the availability raw materials from convenient for the production of calcium silicate blocks, and the effect of variations of the productive process on the developed products. The studied raw materials were: the quartz sand from the city of São Gonçalo do Amarante/RN, and two lime, a hydrated lime and a pure lime from the city of Governador Dix-Sept Rosado/RN. The raw materials collected were submitted a testes to particle size distribution, fluorescence of X rays, diffraction of X rays. Then were produced 8 formulations and made body-of-test by uniaxial pressing at 36 MPa, and cured for 7 hours at about 18 kgf/cm2 pressing and temperature of approximately 180 °C. The cure technological properties evaluated were: lineal shrinkage, apparent density, apparent porosity, water absorption, modulus of rupture flexural (3 points), resistance compression, phase analysis (XRD) and micromorphological analysis (SEM). From the results presented the technological properties, was possible say that utilization of hydrated lime becomes more viable its utilization in mass limestone silica, for manufacture of calcium silicate blocks

Aspects of the in vitro bioactivity of hydraulic calcium (alumino)silicate cement

In response to a burgeoning interest in the prospective clinical applications of hydraulic calcium (alumino)silicate cements, the in vitro bioactivity and dissolution characteristics of a white Portland cement have been investigated. The formation of an apatite layer within 6 h of contact with simulated body fluid was attributed to the rapid dissolution of calcium hydroxide from the cement matrix and to the abundance of pre-existing Si-OH nucleation sites presented by the calcium silicate hydrate phase. A simple kinetic model has been used to describe the rate of apatite formation and an apparent pseudo-second-order rate constant for the removal of HPO42- ions frorn solultion has been calculated (k(2) = 5.8 x 10(-4) g mg(-1)). Aspects of the chemistry of hydraulic cements are also discussed with respect to their potential use in the remedial treatment of living tissue. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 90A: 166-174, 2009

Effect of calcium and magnesium silicate on the growth of the castor oil plant subjected to salinity levels

Salt stress decreases the osmotic potential of soil solution causing water stress, causing toxic effects in the plants resulting in injuries on the metabolism and nutritional disorders, thus compromising the plant growth, resulting in lower production. The calcium silicate and magnesium can perform the same function as limestone, besides providing silicon to plants, may also contribute to the resistance of plants to salt stress. Thus, the objective of this study was to evaluate the effect of calcium and magnesium silicate on the growth of the castor oil plant BRS Energia cultivated under saline conditions. This study evaluated plant height, stem diameter, number of leaves, leaf area, dry weight of shoot and root, and soil chemical characteristics. There was no interaction between factors of salinity level and of silicate level regarding the evaluated variables. There was a direct relationship between salinity levels and plant growth in height and stem diameter. The K concentration in soil were affected by salinity levels.

In situ preparation and protein delivery of silicate/alginate composite microspheres with core-shell structure

It is predicted that with increased life expectancy in the developed world, there will be a greater demand for synthetic materials to repair or regenerate lost, injured or diseased bone (Hench & Thompson 2010). There are still few synthetic materials having true bone inductivity, which limits their application for bone regeneration, especially in large-size bone defects. To solve this problem, growth factors, such as bone morphogenetic proteins (BMPs), have been incorporated into synthetic materials in order to stimulate de novo bone formation in the center of large-size bone defects. The greatest obstacle with this approach is that the rapid diffusion of the protein from the carrier material, leading to a precipitous loss of bioactivity; the result is often insufficient local induction or failure of bone regeneration (Wei et al. 2007). It is critical that the protein is loaded in the carrier material in conditions which maintains its bioactivity (van de Manakker et al. 2009). For this reason, the efficient loading and controlled release of a protein from a synthetic material has remained a significant challenge. The use of microspheres as protein/drug carriers has received considerable attention in recent years (Lee et al. 2010; Pareta & Edirisinghe 2006; Wu & Zreiqat 2010). Compared to macroporous block scaffolds, the chief advantage of microspheres is their superior protein-delivery properties and ability to fill bone defects with irregular and complex shapes and sizes. Upon implantation, the microspheres are easily conformed to the irregular implant site, and the interstices between the particles provide space for both tissue and vascular ingrowth, which are important for effective and functional bone regeneration (Hsu et al. 1999). Alginates are natural polysaccharides and their production does not have the implicit risk of contamination with allo or xeno-proteins or viruses (Xie et al. 2010). Because alginate is generally cytocompatible, it has been used extensively in medicine, including cell therapy and tissue engineering applications (Tampieri et al. 2005; Xie et al. 2010; Xu et al. 2007). Calcium cross-linked alginate hydrogel is considered a promising material as a delivery matrix for drugs and proteins, since its gel microspheres form readily in aqueous solutions at room temperature, eliminating the need for harsh organic solvents, thereby maintaining the bioactivity of proteins in the process of loading into the microspheres (Jay & Saltzman 2009; Kikuchi et al. 1999). In addition, calcium cross-linked alginate hydrogel is degradable under physiological conditions (Kibat PG et al. 1990; Park K et al. 1993), which makes alginate stand out as an attractive candidate material for the protein carrier and bone regeneration (Hosoya et al. 2004; Matsuno et al. 2008; Turco et al. 2009). However, the major disadvantages of alginate microspheres is their low loading efficiency and also rapid release of proteins due to the mesh-like networks of the gel (Halder et al. 2005). Previous studies have shown that a core-shell structure in drug/protein carriers can overcome the issues of limited loading efficiencies and rapid release of drug or protein (Chang et al. 2010; Molvinger et al. 2004; Soppimath et al. 2007). We therefore hypothesized that introducing a core-shell structure into the alginate microspheres could solve the shortcomings of the pure alginate. Calcium silicate (CS) has been tested as a biodegradable biomaterial for bone tissue regeneration. CS is capable of inducing bone-like apatite formation in simulated body fluid (SBF) and its apatite-formation rate in SBF is faster than that of Bioglass® and A-W glass-ceramics (De Aza et al. 2000; Siriphannon et al. 2002). Titanium alloys plasma-spray coated with CS have excellent in vivo bioactivity (Xue et al. 2005) and porous CS scaffolds have enhanced in vivo bone formation ability compared to porous β-tricalcium phosphate ceramics (Xu et al. 2008). In light of the many advantages of this material, we decided to prepare CS/alginate composite microspheres by combining a CS shell with an alginate core to improve their protein delivery and mineralization for potential protein delivery and bone repair applications

A vibrational spectroscopic study of the silicate mineral pectolite – NaCa2Si3O8(OH)

The mineral pectolite NaCa2Si3O8(OH) is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and in other industrial applications. Raman bands at 974 and 1026 cm−1 are assigned to the SiO stretching vibrations of linked units of Si3O8 units. Raman bands at 974 and 998 cm−1 serve to identify Si3O8 units. The broad Raman band at around 936 cm−1 is attributed to hydroxyl deformation modes. Intense Raman band at 653 cm−1 is assigned to OSiO bending vibration. Intense Raman bands in the 2700–3000 cm−1 spectral range are assigned to OH stretching vibrations of the OH units in pectolite. Infrared spectra are in harmony with the Raman spectra. Raman spectroscopy with complimentary infrared spectroscopy enables the characterisation of the silicate mineral pectolite.

A vibrational spectroscopic study of the silicate mineral harmotome – (Ba,Na,K)1-2(Si,Al)8O16⋅6H2O – A natural zeolite

The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16⋅6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm−1 are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm−1 are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm−1 are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm−1 spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm−1 is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome.

A vibrational spectroscopic study of the silicate mineral normandite – NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2

We have studied the mineral normandite using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral normandite NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2 is a crystalline sodium calcium silicate which contains rare earth elements. Chemical analysis shows the mineral contains a range of elements including Na, Mn2+, Ca, Fe2+ and the rare earth element niobium. No Raman bands are observed above 1100 cm−1. The mineral is characterised by Raman bands observed at 724, 748, 782 and 813 cm−1. Infrared bands are broad; nevertheless bands may be resolved at 723, 860, 910, 958, 933, 1057 and 1073 cm−1. Intense Raman bands at 454, 477 and 513 cm−1 are attributed to OSiO bending modes. No Raman bands are observed in the hydroxyl stretching region, but low intensity infrared bands are observed at 3191 and 3450 cm−1. This observation brings into question the true formula of the mineral.

Characterization of carbonated tricalcium silicate and its sorption capacity for heavy metals: A micron-scale composite adsorbent of active silicate gel and calcite

Adsorption-based processes are widely used in the treatment of dilute metal-bearing wastewaters. The development of versatile, low-cost adsorbents is the subject of continuing interest. This paper examines the preparation, characterization and performance of a micro-scale composite adsorbent composed of silica gel (15.9 w/w%), calcium silicate hydrate gel (8.2 w/w%) and calcite (75.9 w/w%), produced by the accelerated carbonation of tricalcium silicate (C(3)S, Ca(3)SiO(5)). The Ca/Si ratio of calcium silicate hydrate gel (C-S-H) was determined at 0.12 (DTA/TG), 0.17 ((29)Si solid-state MAS/NMR) and 0.18 (SEM/EDS). The metals-retention capacity for selected Cu(II), Pb(II), Zn(II) and Cr(III) was determined by batch and column sorption experiments utilizing nitrate solutions. The effects of metal ion concentration, pH and contact time on binding ability was investigated by kinetic and equilibrium adsorption isotherm studies. The adsorption capacity for Pb(II), Cr(III), Zn(II) and Cu(II) was found to be 94.4 mg/g, 83.0 mg/g, 52.1 mg/g and 31.4 mg/g, respectively. It is concluded that the composite adsorbent has considerable potential for the treatment of industrial wastewater containing heavy metals.

Calagem e silicatagem superficiais e a disponibilidade de cátions hidrossolúveis em culturas anuais e braquiária

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influência de silicato e calcário na decomposição de resíduos culturais e disponibilidade de nutrientes ao feijoeiro

A disponibilidade do Si pelo silicato de Ca poderá aumentar a formação de polifenóis, os quais tornariam possível a maior persistência dos resíduos culturais em superfície. Com esse intuito, procurou-se avaliar a ação do silicato e do calcário na decomposição de diferentes resíduos culturais e a liberação de nutrientes para o desenvolvimento do feijoeiro. O delineamento experimental empregado foi o de blocos casualizados em esquema fatorial 3 x 5, com quatro repetições. Os tratamentos foram constituídos de três espécies de plantas de cobertura: milheto (Pennisetum americanum), braquiária (Brachiaria brizantha) e guandu-anão (Cajanus cajan L.) e cinco níveis proporcionais de silicato de cálcio: 0, 25, 50, 75 e 100 %, aplicado nas doses crescentes de 0, 2,31, 4,63, 6,96 e 9,27 g/vaso, respectivamente, balanceadas com carbonato de cálcio e carbonato de magnésio, de forma que as quantidades de Ca e Mg em cada tratamento fossem iguais, calculados para atingir uma saturação por bases no solo de 70 %. A aplicação de silicato de Ca não interferiu na decomposição do resíduo cultural de braquiária, guandu e milheto. O teor de Mg disponível no solo foi reduzido pela aplicação de silicato de Ca, o que induz menor absorção pelas plantas de cobertura e eventual disponibilização após sua decomposição. O crescimento do feijoeiro foi favorecido pela aplicação de silicato de Ca, sendo as doses de 2,31 e 6,95 g/vaso de silicato com o resíduo cultural de braquiária os tratamentos que apresentaram maior eficiência.

Efeito residual da escória de siderurgia como corretivo de acidez do solo na soqueira de cana-de-açúcar

A escória de siderurgia, como material corretivo e efeito residual prolongado, pode beneficiar culturas de ciclo longo, a exemplo da cana-de-açúcar, minimizando a queda de produção ao longo do ciclo produtivo. Este trabalho objetivou avaliar diferentes níveis de saturação por bases, utilizando, como corretivo do solo, a escória de siderurgia, comparando-a com calcário calcítico, nas alterações de alguns atributos químicos do solo, bem como na resposta da soqueira da cana-de-açúcar. Para isto, realizou-se um experimento com a variedade SP 80-1842, durante o terceiro e o quarto corte, nos anos agrícolas 2000/01 e 2001/02. Os tratamentos, dispostos em blocos casualizados, em esquema fatorial com quatro repetições, constaram de duas fontes de corretivos, calcário calcítico e escória de siderurgia, e quatro níveis de correção, estimados pelo método da saturação por bases (V %): testemunha (sem correção) e com correção para V % de 50; 75 e 100, tendo sido tais corretivos aplicados na época do plantio da cana-de-açúcar. O calcário calcítico e a escória de siderurgia promoveram efeito residual benéfico, após 48 meses da aplicação, na correção da acidez do solo e na elevação do valor da saturação por bases; a maior dose de calcário causou efeito depressivo no perfilhamento, no número de colmos industrializáveis e na produção da cana-de-açúcar, fato não observado com uso da escória de siderurgia; a aplicação da escória de siderurgia e do calcário, em pré-plantio, promoveu efeito residual positivo na produção da soqueira de cana-de-açúcar.

Aplicação de escória siderúrgica calcário e ureia em latossolo cultivado com arroz

A escória de siderurgia é um silicato de cálcio e fonte de silício, que tem ação corretiva da acidez do solo semelhante à do calcário. Apesar do seu grande potencial de uso como corretivo e fertilizante, existem poucas informações sobre seus efeitos nos atributos químicos do solo. O estudo foi realizado com a cultura do arroz, objetivando-se avaliar os efeitos da aplicação da escória de siderurgia, calcário e ureia nas alterações dos atributos químicos de um Latossolo Vermelho distrófico. Os tratamentos constaram da combinação de duas fontes de materiais corretivos (calcário e escória de siderurgia), em três doses (1,3 g dm-3 2,6 g dm-3 e 5,2 g dm-3; três doses de N (80 mg dm-3 160 mg dm-3e 320 mg dm-3, aplicadas na forma de ureia; e uma testemunha, dispostas em blocos casualizados, em esquema fatorial, com quatro repetições. Após o período de 90 dias de incubação do solo e 120 dias de cultivo da cultura do arroz, coletaram-se amostras do solo, para análise química. A escória de siderurgia foi viável como corretivo de acidez do solo e a adubação nitrogenada em arroz contribuiu para incrementos na acidez do solo, diminuindo a saturação por bases e o teor de Ca e Mg. A aplicação de escória de siderurgia favoreceu a disponibilidade de silício, entretanto, quando associada à adubação nitrogenada, não alterou o teor deste elemento no solo.

Avaliação agronômica da escória de siderurgia na cana-de-açúcar durante cinco ciclos de produção

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)