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.

Características físicas e mecânicas de misturas de solo, cimento e casca de arroz

The main objective of this work is the study of the effect of rice husk addition on the physical and mechanical properties of soil-cement, in order to obtain an alternative construction material. The rice husk preparation consisted of grinding, sieving, and the pre-treatment with lime solution. The physical characteristics of the soil and of the rice husk were determined. Different amounts of soil, cement and rice husk were tested by compaction and unconfined compression. The specimens molded according to the treatments applied to the mixtures were subsequently submitted to compression testing and to tensile splitting cylinder testing at 7 and 28 days of age and to water absorption testing. After determining its physical and mechanical characteristics, the best results were obtained for the soil + 12% (cement + rice husk) mixture. The results showed a promising use as an alternative construction material.

Efeito da adição de cinza da casca de arroz em misturas cimento-casca de arroz

The rice husk and its ash are abundant and renewable and can be used to obtain alternative building materials. An increase in the consumption of such waste could help minimize the environmental problems from their improper disposal. This study aimed to evaluate the use of ashes as a cargo mineral (filler). However, the rice husk chemically interferes in the conduct of the based cement mixtures. Thus, different mixes cement-rice husk with and without the addition of ash were evaluated in order to highlight the influence of its components (husk; ash), which could otherwise be excluded or be underestimated. Cylindrical samples (test of simple compression and traction by diametrical compression) and samples extracted from manufactured pressed board (test of bending and parallel compression to the surface), were used to evaluate the behavior of different mixtures of components (rice hush; RHA - rice husk ahs). The results of the mechanical tests showed, in general, there is not a statistical difference between the mixtures, which are associated with the chemical suppressive effect of the rice husk ash. The mixture of rice husk of 10 mm, with an addition of 35% of the rice husk ash, is notable for allowing the highest consumption of rice husk and rice husk ash, to reduce 25% the consumption of cement and to allow the storage (without emissions to the atmosphere), around 1.9 ton of CO2 per ton of cement consumed, thus contributing to the reduction of CO2 emissions, which can stimulate rural constructions under an ecological point of view.

Variabilidade espacial de atributos físicos de um argissolo vermelho-amarelo sob pastagem e vegetação secundária em regeneração natural

This work was carried out with the objective of studying the spatial variability of the physical attributes of a Red-Yellow Ultisol under pasture and secondary vegetation in natural regeneration. Two areas were chosen in a hillside, with the soil sampling to the depth of 0-0.2 m, with the georeferenced points in a regular grid of 10x10 m, totalizing 64 points. In each point it was evaluated the total volume of porosity, macroporosity, microporosity, bulk density, soil penetration resistance and soil water content. The studied attributes in the pasture area present indicator of soil compaction for the animals' traffic, with moderate and strong structure of spatial dependence, except for the macroporosity and penetration resistance. In the area of secondary vegetation (VN) only the macroporosity does not present spatial dependence. The total volume of porosity and the bulk density present the same spatial standard in the area under pasture.

Caracterização física e mecânica de argamassas à base de cimento Portland e cinza de casca de arroz residual

Rice husk, employed as an energy source at milling industries in Brazil generates, after burning, a dark ash. This residue is not yet conveniently disposed, being currently dumped on large areas, causing environmental problems. This research intended to evaluate the applications of residual rice husk ashes (RHA) as a partial replacement of cement for mortar production. Rice husk ash was chemically characterized through X-ray fluorescence, determination of carbon content, X-ray diffraction, and laser granulometric analysis. Mortar specimens were submitted to two different exposure conditions: internal and external environments at a maximum period of five months. Physical-mechanical testing were compressive strength and ultrasonic pulse velocity (UPV). Although presenting good mechanical performance, the mortar based on ash (RHA) did not present pozolanicity but it can be employed in cement matrices as inert material (filler).

Atributos mecânicos e erosão por salpicamento em amostras de latossolo vermelho-amarelo sob efeito de vinhaça

The objective of this study was to quantify the effect of plonk on compressive behavior and mechanical attributes such as consistency, optimum moisture for compaction and maximum density of a Red-Yellow Latosol (Oxisol) to evaluate the effect of plonk and compaction state in splashed particles, from Lavras (MG) region. The plonk was obtained from an artisanal sugarcane brandy alembic. Undisturbed and disturbed soil samples were collected at 0 to 3 cm and 60 to 63 cm depths. Disturbed soil samples were used for soil characterization, determination of consistence limits and Normal Proctor essay after material incubation with plonk. Undisturbed soil samples were saturated with plonk or distilled water (control) during 48 hours for testing the compressibility and resistance to splash by using simulated rainfall. The plonk altered the consistence limits of studied layers. For the 0-3 cm layer, the plonk reduced the friable range, and for the 60-63 cm layer the effect was in the opposite direction. For both layers, the plonk increased Dmax and decreased Uoptimum. Regardless of the plonk treatment, both layers presented the same load support capacity. The compaction degree of samples influenced the splash erosion. The increase of the applied pressure over the samples resulted in increase of splash material quantity. At the 60-63 cm layer, the plonk treatment reduced the splash material quantity by increasing the applied pressure, mainly when the samples were at field capacity.