Antonio Ludovico Beraldo

Nano-scale hydrogen-bond network improves the durability of greener cements.

More than ever before, the worlds increasing need for new infrastructure demands the construction of efficient, sustainable and durable buildings, requiring minimal climate-changing gas-generation in their production. Maintenance-free “greener” building materials made from blended cements have advantages over ordinary Portland cements, as they are cheaper, generate less carbon dioxide and are more durable. The key for the improved performance of blends (which substitute fine amorphous silicates for cement) is related to their resistance to water penetration. The mechanism of this water resistance is of great environmental and economical impact but is not yet understood due to the complexity of the cements hydration reactions. Using neutron spectroscopy, we studied a blend where cement was replaced by ash from sugar cane residuals originating from agricultural waste. Our findings demonstrate that the development of a distinctive hydrogen bond network at the nano-scale is the key to the performance of these greener materials.

Physical and mechanical characterization on Portland cement mortar with rice husk ash addition

A casca de arroz, utilizada como fonte de energia em industrias de beneficiamento de arroz, converte-se, depois da queima, em uma cinza residual. Esse residuo, ainda sem um destino adequado, e muitas vezes depositado em grandes areas abertas e provoca elevado impacto ambiental. Este trabalho teve como objetivo avaliar a viabilidade de utilizacao da cinza de casca de arroz (CCA) residual na producao de argamassas, como substituta parcial do cimento. A caracterizacao da CCA foi realizada por meio da analise de fluorescencia de raios-X (composicao quimica), analise do teor de carbono e difracao de raios-X; tambem foi realizada analise granulometrica a laser. Os corpos de prova foram submetidos a dois tipos de exposicao: ambientes externo e interno, com duracao maxima de cinco meses. Foram realizados os ensaios de resistencia a compressao simples e nao destrutivo (velocidade do pulso ultrassonico - VPU). Embora as argamassas tenham apresentado bom desempenho mecânico, os ensaios de pozolanicidade indicaram que a cinza de casca de arroz residual utilizada nao e uma pozolana, mas pode ser utilizada em matrizes cimenticias como material inerte (filler).

Durabilidade de compósito biomassa vegetal-cimento modificado por polímero

The durability of the cellulose-cement composites is a decisive factor to introduce such material in the market. Polymers have been used in concrete and mortar production to increase its durability. The goal of this work was the physical and mechanical characterization of cellulose-cement composites modified by a polymer and the subsequent durability evaluation. The work also evaluated the dispersion of acrylic polymer in composites made of Pinus caribaea residues. The physical properties observed were water absorption by immersion and bulk density. Rupture modulus and toughness were determined by flexural test. The specimens were obtained from pads, produced by pressing and wet curing. Samples were subjected to accelerated aging tests by repeated wetting and drying cycles and hot-water bath and natural aging. The scanning electron microscopy (SEM) allowed verifying the fiber and composite characteristics along the time. For the composite range analyzed, it was observed the polymer improved the mechanical properties of composites besides a significant decreasing in water absorption. The use of polymer improved the performance of vegetable fiber-cement composites when compared to the conventional mortar, due to water absorption decreasing.

Young bamboo culm: Potential food as source of fiber and starch

With the objective of widening the use of bamboo in the food industry, the present work aimed to produce and characterize the young bamboo culm flours from varieties Dendrocalamus asper, Bambusa tuldoides and Bambusa vulgaris as potential sources of fiber and starch. The young culms were collected, cut in three sections (bottom, middle, top), processed into flour, and they were physically, chemically and technologically analyzed. The data were obtained in triplicate and evaluated by means of average differences, using analysis of variance (ANOVA) and Scott-Knott test (p<0.05). The young bamboo culms flours presented low values for moisture content (<10g/100g), protein, lipids and ash contents (<3g/100g). Regarding the carbohydrates profile, the flours were significantly different in their sugar, starch and total fiber contents. All flour samples presented a potential for fiber extraction (>60g/100g), and the varieties B. vulgaris and D. asper, presented an additional potential for starch extraction (16 and 10g/100g, respectively). Regarding technological characteristics, all flours presented bright yellow color, lightly acidic pH (>5.0), water solubility index (WSI) lower to 2.5%, excepting D. asper, which presented a WSI superior to 7.5%. In this way, the evaluated young bamboo culms present potential application in the food industry as flours and as source of fibers; in addition, the varieties D. asper and B. vulgaris can also be used for starch extraction.

Cinza de palha de cana-de-açúcar como adição mineral em fibrocimento

Brazil is the worlds largest producer of sugarcane, and its sugarcane industry generates a large amount of liquid and solid wastes, among them the sugarcane straw. Aiming to add value to this waste, sugarcane straw ash was produced by controlled burning at 700 °C and it was applied as mineral addition in cement composites. The ashes were characterized by the techniques of X ray fluorescence, X ray diffraction, laser particle size and specific surface area. The following composite properties were evaluated: water absorption, apparent porosity, bulk density, modulus of rupture, specific energy, elastic modulus and proportionality limit. The characterization of ash showed a high specific surface area and porosity and a halo of amorphicity was observed in the diffractograms. Composites produced with these ashes showed physical and mechanical characteristics similar to that of the control, allowing the partial replacement of Portland cement by this type of ashes.

Effects of thermal treatment on the physicochemical characteristics of giant bamboo

Despite countless use possibilities for bamboo, this material has two major disadvantages. One drawback is the low natural durability of most bamboo species due to presence of starch in their parenchyma cells. The other equally important drawback is the tendency bamboo has to present dimensional variations if subjected to environmental change conditions. In an attempt to minimize these inconveniences, strips (laths) of Dendrocalamus giganteus Munro were taken from different portions of the culm and subjected to several temperatures, namely 140 oC, 180 oC, 220 oC, 260 oC and 300 oC under laboratory conditions, at the ESALQ-USP college of agriculture. The thermal treatment process was conducted in noninert and inert atmospheres (with nitrogen), depending on temperature Specimens were then subjected to physicomechanical characterization tests in order to determine optimum thermal treatment conditions in which to preserve to the extent possible the original bamboo properties. Results revealed that there is an optimum temperature range, between 140 o and 220 oC, whereby thermally treated bamboo does not significantly lose its mechanical properties while at the same time showing greater dimensional stability in the presence of moisture.

Avaliação físico-mecânica de colmos de bambu tratados

Bamboo is a renewable raw material and is available in tropical and subtropical regions, where it is considered as an inexpensive material. Nevertheless, most bamboo species are highly susceptible to insect and fungi attacks. Basically, bamboo culm protection can be obtained by means of two types of treatment: natural protection and chemical protection. In this study the performance of a Boucherie Modified Method was evaluated, comparing treated bamboo samples (bamboo splits) with untreated samples (control). The effects of the sample position in the culm, chemical solution type and its concentration, treatment duration and the exposition period in two environments (protected and unprotected) were evaluated. Non destructive evaluation - NDE (visual, weight control and ultrasound) and flexure test were applied to the specimens over time. Results obtained showed that dilute solutions, mainly when combined with smaller treatment times, were not effective at protecting bamboo against decay. Results obtained by ultrasound and flexure tests were sensitive enough to detect the best combination of the effect of the evaluated parameters.

TÉCNICA DE MOIRÉ APLICADA AL ANÁLISIS DE ESFUERZOS DE COMPRESIÓN EN EL BAMBÚ GUADUA

Bamboo is considered an important raw material in developing countries because its physical characteristics associate lightness with high mechanical resistance. However its behavior obtained from mechanical tests is not yet well defined. This research work had the objective of evaluating bamboo (Guadua angustifolia) testing specimens under simple uniaxial compression loading. Shadow moire optical methods had been employed to generate deformation mapping as function of knots (0, 1 or 2). Obtained results indicate that the technique is well adequate in generating iso-deformation contour lines in bamboo specimens.

Avaliação térmica de placas de argamassa de cimento e casca de arroz aquecidas por resistência elétrica

An alternative proposal for floor heating system by means of electric resistance for both chick and piggy installation is presented in this work. Several formulations of rice husk and cement mortar boards were used. An electronic device controlled all board temperature. This system presented a good efficiency design. The conventional cement mortar mixed with rice husk showed a better performance.

RESISTÊNCIA DE DUAS ESPÉCIES DE BAMBU TRATADAS CONTRA FUNGOS XILÓFAGOS

This work aimed to evaluate the resistance of bamboo species Bambusa vulgaris and Dendrocalamus giganteus, after being exposed to three methods of chemical preservative treatments against the action of Postia placenta and Polyporus fumosus fungi. The treatment methods employed were transpiration (integral and ruptured diaphragm), long-term immersion and Boucherie modified. The bamboo stems were transformed into culms of 2.0 m long and treated in a solution of 1 or 3% active ingredient (a.i.) of a commercial product based on copper, chromium and boron (CCB). In the methods by transpiration and the long-term immersion, culms were exposed in solutions for periods of 5, 10 or 15 days, while in the modified Boucherie method there was no segregation of treatment between times of treatment. To assess the effectiveness of the treatments, Postia placenta and Polyporus fumosus fungi were employed. From the results obtained it was observed that, on average, for both species of bamboo and tested methods, the mass loss of samples of bamboo, after undergoing the fungal attack, was low, varying from 2.44 to 14.26%.O objetivo deste trabalho foi avaliar a resistencia de bambus das especies Bambusa vulgaris e Dendrocalamus giganteus apos serem expostos a tres metodos de tratamentos quimicos preservativos, contra a acao dos fungos Postia placenta e Polyporus fumosus. Os metodos de tratamento empregados foram o de transpiracao (diafragma integro e rompido), imersao prolongada e Boucherie modificado. As hastes de bambu foram transformadas em colmos de 2,0 m de comprimento e tratadas em solucao de 1 ou 3% de ingredientes ativos (i.a.) de um produto comercial a base de cobre, cromo e boro (CCB). Nos metodos por transpiracao e imersao prolongada, os colmos foram expostos nas solucoes por periodos de 5, 10 ou 15 dias, enquanto no metodo de Boucherie modificado nao houve segregacao do tratamento entre tempos de tratamento. Para avaliar a eficiencia dos tratamentos, foram empregados os fungos Postia placenta e Polyporus fumosus. A partir dos resultados, observou-se que, em media, em ambas as especies de bambu tratadas e metodos empregados, a perda de massa das amostras de bambu, depois de submetidas ao ataque dos fungos, foi baixa, tendo variado de 2,44 a 14,26%.