Influence of High Temperatures on the Mechanical Properties of Wood Bio-Concretes

The use of wood wastes in the production of bio-concrete shows high potential for the development of sustainable civil construction, since this material, in addition to having low density, increases the energy efficiency of buildings in terms of thermal insulation. However, a concern arising from the production of bio-concretes with high amounts of plant biomass is how this material behaves when subjected to high temperatures. Therefore, this work aims to evaluate the influence of high temperatures on the mechanical properties of wood bio-concretes. The mixtures were produced with wood shavings volumetric fractions of 40, 50 and 60% and cementitious matrix composed of a combination of cement, fly ash and metakaolin. Uniaxial compression tests and scanning electron microscopy (SEM) were performed, with bio-concrete at age of 28 days, at room temperature (reference) and after exposure to temperatures of 100, 150, 200 and 250 °C. The density and compressive strength of the bio-concrete gradually decreased with increasing biomass content. Up to 200 °C, reductions in strength and densities less than 19% and 13%, respectively, were observed. At 250 °C, reductions of compressive strength reached 87%. Analysis performed by SEM showed an increase in the number of cracks in the wood-cementitious matrix interface and wood degradation by increasing the temperature.

Conservation of Waterlogged Wood—Past, Present and Future Perspectives

This paper reviews the degradation, preservation and conservation of waterlogged archaeological wood. Degradation due to bacteria in anoxic and soft-rot fungi and bacteria in oxic waterlogged conditions is discussed with consideration of the effect on the chemical composition of wood, as well as the deposition of sulphur and iron within the structure. The effects on physical properties are also considered. The paper then discusses the role of consolidants in preserving waterlogged archaeological wood after it is excavated as well as issues to be considered when reburial is used as a means of preservation. The use of alum and polyethylene glycol (PEG) as consolidants is presented along with various case studies with particular emphasis on marine artefacts. The properties of consolidated wood are examined, especially with respect to the degradation of the wood post-conservation. Different consolidants are reviewed along with their use and properties. The merits and risks of reburial and in situ preservation are considered as an alternative to conservation.

Comparative Study of Secreted Proteins, Enzymatic Activities of Wood Degradation and Stilbene Metabolization in Grapevine Botryosphaeria Dieback Fungi

Botryosphaeriaceae fungi are plant pathogens associated with Botryosphaeria dieback. To better understand the virulence factors of these fungi, we investigated the diversity of secreted proteins and extracellular enzyme activities involved in wood degradation and stilbene metabolization in Neofusicoccum parvum and Diplodia seriata, which are two major fungi associated with grapevine B. dieback. Regarding the analysis of proteins secreted by the two fungi, our study revealed that N. parvum, known to be more aggressive than D. seriata, was characterized by a higher quantity and diversity of secreted proteins, especially hydrolases and oxidoreductases that are likely involved in cell wall and lignin degradation. In addition, when fungi were grown with wood powder, the extracellular laccase and Mn peroxidase enzyme activities were significantly higher in D. seriata compared to N.parvum. Importantly, our work also showed that secreted Botryosphaeriaceae proteins produced after grapevine wood addition are able to rapidly metabolize the grapevine stilbenes. Overall, a higher diversity of resveratrol and piceatannol metabolization products was found with enzymes of N. parvum compared to D. seriata. This study emphasizes the diversity of secreted virulence factors found in B. dieback fungi and suggests that some resveratrol oligomers produced in grapevine wood after pathogen attack could be formed via pathogenic fungal oxidases.

The Phylogenetic Relationship Revealed Three New Wood-Inhabiting Fungal Species From Genus Trechispora

Wood-inhabiting fungi play a significant role in wood degradation and the cycle of matter in the ecological system. In the present study, three new wood-inhabiting fungal species, Trechispora bambusicola, Trechispora fimbriata, and Trechispora fissurata spp. nov., are nested in Trechispora, which are proposed based on a combination of morphological features and molecular evidence. Sequences of internal transcribed spacer (ITS) and large subunit (nLSU) regions of the studied samples were generated, and the phylogenetic analyses were performed with maximum likelihood, maximum parsimony, and Bayesian inference methods. The phylogenetic analyses inferred from ITS showed that T. bambusicola was sister to Trechispora stevensonii, T. fimbriata grouped with Trechispora nivea, and T. fissurata grouped with Trechispora echinospora. The phylogenetic tree based on ITS + nLSU sequences demonstrated that T. bambusicola formed a single lineage and then grouped with Trechispora rigida and T. stevensonii. T. fimbriata was sister to T. nivea. T. fissurata grouped with Trechispora thelephora.