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Subfossil oak (SO) wood material, originating from three different buried trunks discovered in recent years by excavations in riverbanks on Romanian territory, was analysed in this research. Aged oak recovered from constructions (AO_C) and recent/new oak wood material (NO) were also investigated to provide comparative data for the SO. The oven-dry density and the basic density, the total volumetric and linear swelling and shrinkage coefficients and the compression strength parallel to the grain were the selected physical and mechanical properties considered. The experimental results showed a lower density of SO compared to NO and AO_C tested by up to about 19–20%, alongside a trend of increased dimensional instability, with variability among the tested assortments. The compression strength parallel to the grain was reduced by 19–31% compared to NO. The properties of AO-C were closer to those of NO, but differences between wood materials from different sources and of different ages were registered. A positive linear correlation was found between compression strength parallel to grain and the basic density for all types of material and assortments tested. These comparative results have to be considered by designers and engineers in the valorisation of SO in furniture design and other applications. [ABSTRACT FROM AUTHOR]

Abstract Historic wooden buildings located outdoors are exposed to natural weathering conditions for extended periods of time, causing deterioration of wood properties by sunlight, oxygen, and other environmental factors. Current diagnostic procedures are limited to macroscopic inspection. In this interdisciplinary study, several aged samples from Yingxian Wooden Pagoda (ca. 1056 AD) were analyzed. Their micro-morphology and changes in chemical composition were investigated using less invasive multi-chemical techniques. The aim is to elucidate the oxidative degradation and its deterioration mechanism of the wood, which is essential in identifying the key factors responsible for natural weathering and devising strategies to counteract the surface deterioration. All aged wood samples had varying degrees of decay and lignin content was decreased in most of them. The high ratio of oxygen/carbon elements evidenced the occurrence of chemical reactions. In particular, the increasing ratio of oxygenated carbon/unoxygenated carbon indicates potential oxidation reactions. Overall, for the aged wood of historic wood building under warm-dry natural conditions, their deterioration occurred through the oxidative degradation of lignin. These unique results are useful in developing effective repair and restoration measures to conserve wooden components in historic buildings.

Historic wooden buildings located outdoors are exposed to natural weathering conditions for extended periods of time, causing deterioration of wood properties by sunlight, oxygen, and other environmental factors. Current diagnostic procedures are limited to macroscopic inspection. In this interdisciplinary study, several aged samples from Yingxian Wooden Pagoda (ca. 1056 AD) were analyzed. Their micro-morphology and changes in chemical composition were investigated using less invasive multi-chemical techniques. The aim is to elucidate the oxidative degradation and its deterioration mechanism of the wood, which is essential in identifying the key factors responsible for natural weathering and devising strategies to counteract the surface deterioration. All aged wood samples had varying degrees of decay and lignin content was decreased in most of them. The high ratio of oxygen/carbon elements evidenced the occurrence of chemical reactions. In particular, the increasing ratio of oxygenated carbon/unoxygenated carbon indicates potential oxidation reactions. Overall, for the aged wood of historic wood building under warm-dry natural conditions, their deterioration occurred through the oxidative degradation of lignin. These unique results are useful in developing effective repair and restoration measures to conserve wooden components in historic buildings. [ABSTRACT FROM AUTHOR]

Subfossil oak (SO) wood material, originating from three different buried trunks discovered in recent years by excavations in riverbanks on Romanian territory, was analysed in this research. Aged oak recovered from constructions (AO_C) and recent/new oak wood material (NO) were also investigated to provide comparative data for the SO. The oven-dry density and the basic density, the total volumetric and linear swelling and shrinkage coefficients and the compression strength parallel to the grain were the selected physical and mechanical properties considered. The experimental results showed a lower density of SO compared to NO and AO_C tested by up to about 19–20%, alongside a trend of increased dimensional instability, with variability among the tested assortments. The compression strength parallel to the grain was reduced by 19–31% compared to NO. The properties of AO-C were closer to those of NO, but differences between wood materials from different sources and of different ages were registered. A positive linear correlation was found between compression strength parallel to grain and the basic density for all types of material and assortments tested. These comparative results have to be considered by designers and engineers in the valorisation of SO in furniture design and other applications.

The purpose of this study is to examine the effect of wood aging on the mechanical behavior at the cell-wall level. Synchrotron X-ray diffraction (XRD) measurements were performed to investigate the mechanical behavior of cellulose in the S2 layer of aged wood from a 250-year-old attic cabin beam. XRD measurements under uniaxial loading were performed on the cellulose (004) plane; the results were compared with those of recent wood. The cellulose in aged wood exhibited a delayed response to both tensile and compressive loading compared with recent wood. Under compressive loading, cellulose showed an increase in maximum strain and a significant increase in the variation of cellulose orientation angle, indicating that it may exhibit buckling-like meandering behavior. These results could be explained based on the decrease in hemicellulose content in the cell wall due to wood aging. In other words, the results suggested that an amorphous material in the cell wall affected the mechanical behavior of wood at the cell-wall level. [ABSTRACT FROM AUTHOR]

A greater understanding of moisture sorption behaviour of aged wooden structural components, which has a close relationship with dimensional stability, is required to effectively evaluate and preserve historical artefacts. This study focused on the effects of aging on Baotou beam samples from a Chinese historical wooden building. An analysis of the sorption isotherms and hysteresis loops of a naturally aged, decayed sample (AOS), an aged sound sample (AIS), and a reference sample (RS), using classical sorption isotherm models revealed that the moisture sorption behaviour of samples from the same growth ring in a Baotou beam can differ significantly. AOS showed higher hygroscopicity than AIS, and both these samples were more hygroscopic than RS. Furthermore, the mono/multilayer moisture contents of AOS were always higher than those of AIS and RS. In addition, Fourier transform infrared, second-derivative infrared, and two-dimensional correlation infrared spectroscopy were used to investigate chemical changes in the samples. The relative hemicellulose and lignin contents of the samples changed significantly with wood aging. Furthermore, AOS exhibited the highest calcium oxalate content, which may be associated with fungal infections. Overall, these results provide valuable insights into the effects of aging on wood samples and the dimensional stability of timber structures, which could inform future research on methods for the preservation or restoration of aging timber structures. [ABSTRACT FROM AUTHOR]

In this study, it is aimed to consider whether the strain energy could evaluate the mechanical durability of wood. To investigate the aging effects on the mechanical properties of bulk wood and cellulose microfibrils in the cell walls of wood, XRD measurements were taken under tensile loading. Specimens were recent wood and wood used for 250 years (aged wood). Thermal modifications were further applied for additionally aging treatment of both specimens. The standardized strain energy of the bulk wood and cellulose microfibrils was exponentially reduced with increasing mass loss of specimens. The reduction degree of aged wood was smaller than that of recent wood. Using this phenomenon, it was proposed that the aging effect can be quantitatively evaluated. [ABSTRACT FROM AUTHOR]

The chemical composition of a number of naturally aged construction wood samples of spruce, fir and oak was investigated. The content of lignin, polysaccharide, and extractives was determined using wet chemical and chromatographic methods. Differences to non-aged wood samples were found particularly found on oak wood samples with regard to lignin and polysaccharide content as well as to cellulose crystallinity. The composition of wood extractives of aged and non-aged wood samples revealed degradation processes due to oxidation and slight hydrolysis. The investigation showed that the relative content of the structural wood constituents depends on the sample age as well as the conditions they were aged under. The different degradation rates of those structural components may lead to contradictory results regarding their contents at certain degrees of aging. Cellulose crystallinity values are affected by extractives content. [ABSTRACT FROM AUTHOR]

Due to ecological and environmental factors, re-using aged wood is becoming more and more important, also in applications where mechanical strength plays a central role. The aim of this study was to examine specific mechanical parameters of naturally aged and dried wood and to better understand the influence of aging on the elastic behaviour of wood. To this aim, measurements on boards and on small, clear wood specimens were carried out. Ultrasound velocities of longitudinal and, in some cases, of transversal waves were measured to determine dynamic elastic moduli and shear moduli. The measurements were performed on structural timber of aged Norway spruce (aged wood) and compared with specimens of recently cut and kiln dried timber of the same species (recent wood) as a reference with comparable density properties and average annual ring width. The measurements revealed higher values of dynamic elastic modulus for aged wood in the longitudinal and radial directions, but no significant difference was found in the tangential direction or in the shear moduli. It is supposed that the difference is more likely a consequence of variability in densities and the structure parameters (annual ring structure, microfibril angle, growth conditions) rather than a consequence of the wood age. The relation between the dynamic elastic modulus in the longitudinal direction and wood density was nearly the same for aged and recent wood specimens, so with increased prudence, grading methods developed for recent wood can also be applied for aged wood. [ABSTRACT FROM AUTHOR]

The mechanical behaviour of non-aged (modern) and aged spruce [Picea abies (L.) Karst.] wood was investigated in the radial direction using a microtensile testing device. The size of the samples was 50 × 3 × 3 mm (radial × tangential × longitudinal). Elastic, creep, relaxation, rupture and mechanosorption tests were carried out under controlled temperature and relative humidity. Optical and electronic micrographs were produced in order to correlate the mechanical behaviour with the wood structure. Results indicate that the overall mechanical properties such as Young's modulus and the time-dependent behaviour of wood in the radial direction do not change significantly with age. However, the strength of aged wood shows a decrease of about 25% in the radial direction. This loss of strength in aged wood might be explained by localized damage at the microstructural level in the wood. [ABSTRACT FROM PUBLISHER]

Abstract: Wood is present in many cultural heritage objects in Japan thanks to its capacity to resist over a long period of time. However, the evolution of its properties in regular use remains insufficiently known. The present study on the effect of wood aging takes advantage of the Japanese context where building traditions have been maintained for centuries. 3-point bending tests were performed in longitudinal (L) and radial (R) directions on small clear wood specimens cut from 8 historical samples and one modern reference considered of high quality by craftsmen. Although aged wood appeared more rigid and stronger than recent wood, after density and humidity corrections were applied no significant variation of L and R rigidity or L strength was observed. The post-linear behaviour, however, was drastically influenced by wood age especially in R direction where the strength and rupture energy decreased markedly with the time elapsed since the wood was processed. Well preserved aged wood considered as safe as long as it is not loaded perpendicular to grain. To cite this article: M. Yokoyama et al., C. R. Physique 10 (2009). [Copyright &y& Elsevier]

Knowledge of properties of building materials affected by aging is of great importance to conserve cultural heritages or replace their biopolymer components. The objective of the study was to investigate the chemical characterization change in the biopolymer components and identify whether these changes are correlated with alterations in the nanomechanical properties of the wood cell wall bio-composites in relation to natural aging. The effects of natural aging on the elm (Ulmus) wood component (dated from 1642 to 1681) of Chenghuang Temple, an ancient timber construction in China were investigated to understand the chemical and mechanical changes in the wood cell wall. Especially, confocal Raman microscopy and nanoindentation (NI) were used to track changes in the chemical structure and nanomechanical properties. The results showed that the morphological, chemical and physical properties of cell walls changed with aging. After aging, the cell structure showed evidential alternations, and the wood components, especially hemicellulose and lignin, were degraded, leading to deterioration of mechanical properties of aged wood compared with normal wood. Morphology deterioration and micromechanical changes only occurred on the surface with the depth of about 3.6 mm of the aged element. This study would be helpful to provide practical guidance for protecting the apparent performance of ancient timber structures. [ABSTRACT FROM AUTHOR]