Advanced Technologies for Increasing the Durability of Timber and Extending Its Service Life

Wood is one of most used and appreciated material among humans, and is an irreplaceable choice for building furniture, utility poles, bridges, and more [...

Mechanical and physical properties of Cunninghamia lanceolata wood decayed by brown rot

CITATION: Li, S., et al. 2019. Mechanical and physical properties of Cunninghamia lanceolata wood decayed by brown rot. iForest: Biogeosciences and Forestry, 12(3):317-322, doi:10.3832/ifor2922-012.The original publication is available at http://iforest.sisef.orgENGLISH ABSTRACT: The relationship between the mechanical properties of Cunninghamia lanceolata (Chinese fir) wood and the development of fungal decay was investigated with the aim of implementing a statistical model useful as a non-destructive and a fast method for determining the state of conservation of in-service timber structures. Artificial decay due to brown rot fungi was induced on wood specimens and physical and mechanical test were performed periodically, as well as anatomical observation of wood, FT-IR spectroscopic and XRD diffraction analysis. As a result, Chinese fir was confirmed to have a good durability against fungi, showing a mass loss percentage of 7.21% on average after 14 weeks of exposure. On the contrary, the mechanical properties reduced dramatically during the decay test: a 19% decrease was observed for compression strength and 21% for tensile strength. The mechanism of decay was explored and the corresponding damage constitutive model was proposed.https://iforest.sisef.org/contents/?id=ifor2922-012Publisher's versio

Durability of tannin-boron-treated timber

Tannin-boron wood preservatives were investigated for their resistance against outdoor agents. This work focused on the analysis of the causes that affect the durability of the tannin-hexamine-treated samples. In particular, dimensional stability, resistance to leaching, and resistance to biological agents were investigated. The combined effect of deterioration agents was evaluated by subjecting the treated samples to simulated and natural weathering tests. The study of the appearance and of the color components (L*, a*, and b*) according to CIELAB space of the exposed samples was monitored to assess the efficacy of the tannin-boron formulations for outdoor applications. Significant resistance against the action of water (EN 84, ENV 1250-2) and insects (EN 47) has been demonstrated in specific tests. Conversely, the continuous stress due to artificial and natural weathering deteriorates the color and the visible features of the treated specimens. The combined effect of moisture modifications, solar exposition, and leaching cycles damages the structure of the tannin-based polymeric network and subsequently it negatively affects its preservation properties

Modeling the material resistance of wood—part 2:Validation and optimization of the meyer-veltrup model

Service life planning with timber requires reliable models for quantifying the effects of exposure-related parameters and the material-inherent resistance of wood against biotic agents. The Meyer-Veltrup model was the first attempt to account for inherent protective properties and the wetting ability of wood to quantify resistance of wood in a quantitative manner. Based on test data on brown, white, and soft rot as well as moisture dynamics, the decay rates of different untreated wood species were predicted relative to the reference species of Norway spruce (Picea abies). The present study aimed to validate and optimize the resistance model for a wider range of wood species including very durable species, thermally and chemically modified wood, and preservative treated wood. The general model structure was shown to also be suitable for highly durable materials, but previously defined maximum thresholds had to be adjusted (i.e., maximum values of factors accounting for wetting ability and inherent protective properties) to 18 instead of 5 compared to Norway spruce. As expected, both the enlarged span in durability and the use of numerous and partly very divergent data sources (i.e., test methods, test locations, and types of data presentation) led to a decrease in the predictive power of the model compared to the original. In addition to the need to enlarge the database quantity and improve its quality, in particular for treated wood, it might be advantageous to use separate models for untreated and treated wood as long as the effect of additional impact variables (e.g., treatment quality) can be accounted for. Nevertheless, the adapted Meyer-Veltrup model will serve as an instrument to quantify material resistance for a wide range of wood-based materials as an input for comprehensive service life prediction software

Modelling the Material Resistance of Wood—Part 3: Relative Resistance in above- and in-Ground Situations—Results of a Global Survey

Durability-based designs with timber require reliable information about the wood properties and how they affect its performance under variable exposure conditions. This study aimed at utilizing a material resistance model (Part 2 of this publication) based on a dose–response approach for predicting the relative decay rates in above-ground situations. Laboratory and field test data were, for the first time, surveyed globally and used to determine material-specific resistance dose values, which were correlated to decay rates. In addition, laboratory indicators were used to adapt the material resistance model to in-ground exposure. The relationship between decay rates in- and above-ground, the predictive power of laboratory indicators to predict such decay rates, and a method for implementing both in a service life prediction tool, were established based on 195 hardwoods, 29 softwoods, 19 modified timbers, and 41 preservative-treated timbers

Comprehensive Evaluation Method of Historical Timber Structural Building Taking Fujiu Zhou House as an Example

Physical and mechanical properties of timber components are the basis of developing the technical measures for the conservation and restoration of historical timber structural buildings. By means of integrating on-site investigation (such as a visual survey, moisture content test, micro-drilling resistance test, and material samples collection of historical timber components) and laboratory tests, this study proposed a series of methodologies for comprehensively evaluating the physical and mechanical properties of timber. This method can be quickly mastered by various non-professionals and can help the cross-learning of various disciplines engaged in the research of architectural heritage protection. As a trial, the methodologies were applied to survey and assess a typical historical Chinese timber structural building named the Fujiu Zhou house (the house is located in No. 19, Qinglian lane, Yangzhou city, Jiangsu province, China). The paper studies the 224 components of the main structure of the building, including 128 columns and 96 beams. With the help of the components’ defects and damage status, GB/T13942.2-1992 and the National Lumber Grades Authority (NLGA), the grade of timber components was distinguished. The modulus of elasticity (MOE), modulus of rupture (MOR), and other related material properties parameters of timber components were also obtained. The trial results verify that the proposed methodologies are reasonable, and they can be helpful for the conservation of a historical timber structural building