Revistas Universidad del Bío-Bío
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Spruce chips stabilization in wood-cement materials: Effect of matrix composition
Get PDFThe problem of the presented research is stabilization of spruce chips in modified cement matrix of wood-cement composites and analysing the effect of the stabilisation on selected parameters of these composite materials. The matrix has an impact on the stabilization of the spruce wood content. Silicate ma- trix based on Portland and blended cement was modified by finely ground thermal power plant slag (TPPS) and limestone (LS). Four types of wood-cement composite were subjected to water immersion tests for 28 days. During water immersion, both swelling in thickness and mass changes were analysed. The amount of sugars and pH in leachate were determined after 7 day intervals. Mechanical properties and microstructures were analysed before and after water immersion. Different behaviour with regard to spruce chips stabilization was proved in dependence of wood-cement matrix modification. Differences in thickness, swelling and sugar leach indirectly indicate the influence of the wood-cement composites matrix composition on the stabiliza- tion of spruce chips contained in this matrix. Boards with the matrix modified with thermal power plant slag showed the highest thickness swelling (%) and sugar leaching (0,042 %). Therefore, in the presence of thermal power plant slag modified matrix, spruce chips are more susceptible to sugar leach. The results of strength characteristics confirmed that sugars leached during hydration and after longer contact of wood-cement composites with water have no negative influence in their final properties in the case of all materials tested (reference and modified)
Comportamiento mecánico de muros de corte de Eucalyptus grandis: Resultados experimentales versus el criterio de las normas europeas
Get PDFEn este artículo se presentan y discuten los resultados de un proyecto orientado a investigar el comportamiento mecánico de muros de corte típicos de construcciones de entramado ligero y construidos con bastidor de Eucalyptus grandis de la Mesopotamia Argentina. La investigación se llevó a cabo sobre 17 paneles, 15 de los cuales integraron 5 series con distintas configuraciones que cumplieron los requerimientos constructivos del Método A del Eurocódigo 5 (AENOR 2016a), y 2 con anomalías. Los ensayos se realizaron según la norma UNE-EN 594 (AENOR 2011). La resistencia al descuadre determinada experimentalmente superó a la obtenida según el Método A en todos los paneles que cumplieron los requerimientos constructivos, ubicando del lado de la seguridad al valor calculado según las reglas europeas. Los resultados experimentales probaron una mayor variabilidad de la rigidez que de la resistencia y mostraron que los paneles que fallaron bajo cargas elevadas no siempre desarrollaron la resistencia esperada para deformaciones admisibles bajo cargas de servicio, indicando la conveniencia de focalizar sobre este aspecto en futuras investigaciones sobre estos sistemas estructurales
Cross laminated timber bonding quality for different brazilian species and pressing levels
Get PDFThe proper choice of raw materials and manufacturing parameters for Cross Laminated Timber is essential to promote the proper bonding of the lamellas, aiming at their application in construction. However, few Brazilian species are currently used in the production of Cross Laminated Timber. The aim of this work was to characterize the bonding quality of four Brazilian reforestation species (Pinus elliottii, Eucalyptus grandis, Toona ciliata and Acrocarpus fraxinifolius) in the manufacture of Cross Laminated Timber with two-component polyurethane adhesive and five different pressure levels (from 0,1 MPa to 1,3 MPa). Bonding quality was evaluated through delamination and glue line shear tests based on the standard EN 14080 (2013). Delamination was affected by the wood species, and the best adhesion occurred for the Cross Laminated Timber manufactured with Pinus elliottii and Acrocarpus fraxinifolius at the bonding pressure of 0,7 MPa. Cross Laminated Timber bonding pressure did not affect the percentage of wood in the shear test fractured surface, whereas higher density Cross Laminated Timber showed higher percentages
Physical, mechanical, and thermal characteristics of alkaline copper quaternary impregnated oriental beech wood
Get PDFThe physical, mechanical, and thermal properties of Oriental beech (Fagus orientalis), which had been impregnated with the water-based, copper-containing Korasit KS material from the Alkaline Copper Quaternary group, were investigated in this study. According to ASTM 1413-07el (2007) standard, the wood samples used in the investigation were impregnated with 3 % and 6 % aqueous solutions of Korasit KS. The modulus of rupture, thermal, and water absorption tests were performed on samples of Oriental beech after they had been impregnated. Oriental beech's modulus of rupture values decreased as a result of Korasit KS impregnation. Additionally, Oriental beech had lower modulus of rupture values at greater concentrations of Korasit KS. In every water absorption period, the water absorption values of the Oriental beech impregnated with Korasit KS were higher than those of the control group. Our results showed that Korasit KS impregnation enhanced thermal properties of Oriental beech. Moreover, higher concentration levels of Oriental beech yielded better thermal characteristics of Oriental beech
Quality of Tectona grandis for sawn wood production
Get PDFForestry companies have invested in genetic improvement to increase wood production in a shorter amount of time. Thus, studies are needed to compare the properties of clonal and seminal wood materials. The objective of this study was to analyze physical and mechanical properties of Tectona grandis from clonal (C1 and C2) and seminal (S) origin and evaluate the yield and quality of sawn wood subjected to outdoor and oven drying. Genetic material was collected from six, 15-year-old trees. Clone C2 presented the lowest amount of bark, and 51 % heartwood up to half the commercial height, while the heartwood of C1 and S went up to 25 % of the height. The three materials did not differ statistically for maximum angular deviation, pith eccentricity, basic density, Janka hardness, anisotropy, commercial income of sawn wood and the presence of knots. After the drying processes, the bowing and crooking indexes were less than 5 mm.m-1, however, the seminal material showed a higher cracking incidence after outdoor and oven drying. In conclusion, the wood properties of the three materials are similar. In addition, the oven drying process is recommended
El tapanco en viviendas vernáculas de Querétaro, México. Uso y eficiencia higrotérmica
Get PDFToday, the climatic consequences caused by greenhouse gas (GHG) emissions are evident and are on track to see global warming of 2.7 °C by the end of the century. The energy dependence of buildings is one of the main causes, since they required 50% of global energy consumption in 2021 just for heating, making it necessary to implement passive bioclimatic air conditioning systems. This work documents the use in vernacular dwellings in Queretaro, Mexico, of an efficient attic-type passive system, called "tapanco", consisting of an inert air chamber that functions as a thermal buffer. A case was evaluated by applying measurement methodologies with thermo-hygrometers, complemented with thermography and thermo-wind simulation. The findings of adequate hygrometric indices, fostered by the system, make it a relevant alternative for a passive solution in future bioclimatic architectural design, to reduce adverse energy and climatic indices.Hoy día son evidentes las consecuencias climáticas provocadas por las emisiones de gases de efecto invernadero (GEI) que encaminan a alcanzar 2.7 °C de calentamiento global hacia 2100. La dependencia energética de las edificaciones es una de las causas principales, pues demandaron solo para calefacción el 50% del consumo de energía global en 2021, siendo necesario implementar sistemas bioclimáticos pasivos de climatización. Este trabajo documenta la utilización en viviendas vernáculas de Querétaro, México, de un eficiente sistema pasivo tipo ático, denominado "tapanco", consistente en una cámara de aire inerte que funciona como amortiguador térmico. Se evaluó un caso aplicando metodologías de medición con termo-higrómetros, complementando con termografía y simulación termo-eólica. Los hallazgos de índices higrométricos adecuados, propiciados por el sistema, lo convierten en alternativa relevante de solución pasiva en el diseño arquitectónico bioclimático futuro, para abatir los índices energéticos y climáticos adversos.Hoje, as consequências climáticas das emissões de gases de efeito estufa (GEE) são evidentes e estamos a caminho de atingir 2,7°C de aquecimento global até 2100. A dependência energética das edificações é uma das principais causas, pois elas representaram 50% do consumo global de energia apenas para aquecimento em 2021, tornando-se necessário implementar sistemas passivos bioclimáticos de climatização. Este trabalho documenta a utilização de um eficiente sistema passivo tipo sótão, chamado "tapanco", em moradias tradicionais de Querétaro, México. O sistema consiste em uma câmara de ar inerte que atua como amortecedor térmico. Foi avaliado um caso utilizando metodologias de medição com termo-higrômetros, complementadas por termografia e simulação termo-eólica. Os resultados dos índices higrométricos adequados proporcionados pelo sistema fazem dele uma solução passiva alternativa relevante como solução passiva no futuro projeto arquitetônico bioclimático, visando reduzir os índices energéticos e climáticos adversos
Characterisation of lignins isolated from bamboo organosolv and kraft black liquor
Get PDFBamboo biomass was pulped using organosolv methods: Acetic acid and formic acid; hydrogen peroxide and formic acid; ethanol and water and kraft process with varying concentrations of the cooking chemicals. The properties of the isolated lignin were influenced by the black liquor pH as well as the pulping method. Highest pH (12,8) was recorded for kraft at 70:30 liquor concentration while lowest pH of 2,5 was recorded for both Aceticformic (70:30) and Ethanol/water (70:30 and 60:40). There were obvious differences in the characteristic colours, shapes and sizes of the lignin samples. Bamboo kraft lignin samples formed large pieces much easier than that of Organosolv. Aceticformic (70:30) had the best filteration properties (FC) while Ethanol/water had the poorest. Generally, kraft recorded the highest lignin yield while all the organosolv processes recorded reduced yield. Highest yield (119,25 g/L) was gotten from kraft (50:50) while Peroxyformic (60:40) had the lowest yield of 8,20 g/L. The results showed that higher liquor pH favours total dissolved solid as well as lignin precipitation. As the pH increases, total dissolved solid, yield, Klason and low molecular weight (LMW) lignin content increases while FC decreases. The Klason and LMW lignin content increased with incresing lignin yield
Artificial intelligence to growth stresses predicting in Eucalyptus clones using dendrometric variables and wood density
Get PDFEucalyptus planted forests contribute to maximizing lumber production but problems such as longitudinal growth strain can negatively influence the quality of the products. Knowing dendrometric variables and wood properties can help in the prediction of longitudinal growth strain, mainly with the help of artificial intelligence. Thus, the aim of this research was to evaluate the use of artificial neural networks to predict longitudinal growth strain in Eucalyptus trees based on dendrometric variables, spacing between trees and wood density. The longitudinal growth strain was measured in trees of four Eucalyptus clones planted in three spacings. The diameter and height of each tree were measured. The basic wood density was determined. Artificial neural networks were used to estimate longitudinal growth strain as a function of dendrometric variables, tree spacing and wood density. The results showed that the artificial neural networks presented good results for training and validation, with most of them resulting in high correlation coefficient values. The trained artificial neural networks showed a correlation coefficient above 0,56. Artificial neural networks showed that the variables clone and basic wood density were the ones that most contributed to the prediction of longitudinal growth strain. On the other hand, the spacing between trees, the height of the tree and the diameter at breast height were not relevant to predict growth stresses
Research of computerized numerical control laser processıng qualıtıes of some wood specıes used ın the furnıture ındustry
Get PDFIn recent years, laser material processing technology has become quite widespread. The quality of laser processing of wood materials is very important in terms of not causing secondary processes in the production process. In this study, computerized numerical control laser cutting qualities of some wood species that are frequently used in industrial product manufacturing were investigated. In the study, 80 % irradiation and 10 mm/sec laser cutting speed were applied to the test samples in a computerized numerical control laser machine with a 130 W carbon dioxide gas cylinder. In the case of laser cutting of 5 different wood species in the direction vertical to and parallel to the fibers, the average of the upper and lower kerf width, the difference in the width of the upper and lower kerf, the average of the width of the heat-affected zone, the width of the heat-affected zone were evaluated. In line with the findings, the effects of wood species differences on laser cutting quality in terms of material consumption, precision machining, and smoothness of cutting geometry were investigated. As a result, the highest quality cutting values were obtained from the laser cutting of the bamboo massif in terms of wood species, in the direction vertical to the fibers of the wood materials