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Factors relevant to degradation are important in every wood application. For wood used in ground and water contact; well documented abiotic factors (or agents) include exposure to temperature and m...

An IML-Resi PD-400 drilling tool with two types of spade drill bits (IML System GmbH, Wiesloch, Germany) was used to study the influence of the drilling direction in relation to wood grain orientat...

Wood is by far the best structural material in terms of environmental impact. This superiority can be improved if the longevity of the commodity is extended by reducing the decay susceptibility of ...

The structural integrity of wood–polymer composites (WPC) has not been fully investigated, which can be attributed to a lack of applicable test procedures. In this study, wood–polypropylene composites were assessed by High-Energy Multiple Impact (HEMI) testing. The acquired composites were based on wood particles from various sources and different wood fibre contents, respectively. With respect to wood fibre content, a clear relationship between resistance to impact milling (RIM) and unnotched impact bending strength (acU) was obtained. The lower the fibre content of the WPC the more structural integrity was retained. In return, various wood sources had no effect on acU, but a major impact on RIM values. RIM is suggested to be predominantly affected by structural features, such as fibre/particle content and characteristics, particle agglomerations, and spatial void distribution.

The field performance of wood modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) is reported after outdoor exposure above ground (UC3), in ground (UC4) and in the marine enviro...

IML-Resi PD-400 drilling tools (IML System GmbH, Wiesloch, Germany) were used to study the influence of the feed rate and the rotational frequency of the drill bit on the drilling resistanc...

The durability of wood depends on its in-use environmental conditions. The aim of this study was to estimate the effects associated with macro climate and detail design as well as their interdepend...

An IML-RESI PD 400 drilling tool and a standard spade drill bit (IML System GmbH, Wiesloch, Germany) were used to study the combined effect of wood moisture content (MC), drill bit rotational speed...

Thermally modified wood is becoming an increasingly popular material for different applications in buildings. Laboratory tests indicated a positive effect of thermal modification on durability, dim ...

Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades. In order to enable even more extensive and reliable use of wood...

Dual-treatment technology combining diffusible preservatives with oil-borne preservatives, widely used for crossties in the USA, has now also been commercialized with bridge ties/timbers. In order to understand the implications of these changes, the historic service life of creosote-treated bridge timbers in northern and southeastern USA were considered as well as field-test data for both creosote and copper naphthenate. These were used to estimate potential future service life. Estimates on life expectancy with added borates were also made from published data on performance. Cost–benefit analysis based on creosote and copper naphthenate costs as well as assumptions made from field-test efficacy data suggest cost savings of up to $20 per timber per year of additional service. Service life extension and the resulting cost savings could be achieved in a number of ways: change preservative from creosote to copper naphthenate; increase active ingredient retention; and/or add dual-treatment protection....

The overall aim of this study was to provide comprehensive durability characteristics of wood species underutilized but frequently occurring in Central and Northern Europe: Common juniper (Juniperus communis L.), Black cherry (Prunus serotina Ehrh.), English yew (Taxus baccata L.), and Rowan (Sorbus aucuparia L.). Decay resistance was tested against white and brown rot causing basidiomycetes and soft rot causing micro-fungi in terrestrial microcosms. Their wetting ability was determined in terms of capillary water uptake at the end-grain, the liquid water uptake during submersion, the water vapor uptake at high humidity, and the water release during drying. All tests were performed with unleached and leached specimens. Durability classes were assigned based on results from the different tests. Juniper and Yew were classified very durable (Durability class DC 1); Black cherry and Rowan were found to be less durable (DC 3–5). Leaching did not affect the durability classification significantly. Durab...

The long-term outdoor performance of thermally modified timber (TMT) from four different industrial heat treatment processes was investigated. Graveyard tests (in-ground exposure, use class (UC) 4) and horizontal double layer tests (above ground, UC 3.2) with and without artificial shading were performed. Results from field tests after 14 years of exposure are compared with results from short-term laboratory tests with pure cultures of wood-destroying basidiomycetes and terrestrial microcosms (TMC). The thermally modified material used in the study was: Plato wood (Norway spruce, Picea abies, NL), Thermowood (Scots pine, Pinus sylvestris, FI), New Option Wood (NOW, Maritime pine, Pinus maritima, F), and oil-heat treated (OHT) wood (Scots pine, DE). In addition, Scots pine sapwood and heartwood, Douglas fir (Pseudotsuga menziesii), Sessile oak (Quercus petraea), and CCB treated Scots pine sapwood (0.7 and 2.8% CCB) were examined as control and reference materials. Based on results from laboratory standard ...

Traditionally, many elements of our infrastructure, such as electric power grits, railway networks, guardrails, ports, piles, and bridges – are made of wood. Wood often wins over competitive materi...

The majority of timber products in outdoor use are exposed above ground, e.g. facades, terrace decking, playground equipment, garden furniture, windows, balconies or carports. In contrast, the durability of wood and wood products is most often determined in laboratory against Basidiomycete monocultures or in-ground field tests, where wood samples are submitted to permanent wetting. Worldwide, only a few above ground field test methods evaluating durability against fungal decay have been standardized. Wood used in above ground situations can be exposed to a wide range of moisture loads reflecting different design details such as varying shelter, distance to ground, ventilation and water trapping, whereas temperature and rainfall variations are overall influences on service life performance. The aim of this review was to gather information about standardized and non-standardized above ground field test methods used to determine the durability of wood and wood-based products. In total, more than 60 m...

One key issue in wood construction is durability. Constant wetting and suitable temperatures for fungal growth promote the risk of decay and thus a decrease in structural stability and performance. Hence, performance-based prediction models seem to be reasonable to predict the in-service performance of wooden structures in different outdoor exposure situations. Within this study continuous wood moisture content (MC) and temperature measurements were conducted on five different test objects. Four test set-ups were installed at a test site in Hannover, Germany. A fifth set-up was exposed in As, Norway. Data-sets were applied to a dose–response performance model considering wood MC and temperature as key factors for fungal decay. The expected service life (SL) was calculated for different materials and constructions. In addition, the depth and distribution of decay was assessed using a pick test and compared with the calculated SL. Differences regarding the risk of fungal decay for various constructi...

The paper describes refinements of rapid laboratory assessment of the mechanical performance of timbers used in the marine environment as regards their resistance to indentation, impact abrasion from smooth and sharp abrasives and to dynamic impact loads when wet. Ten tropical and home-grown hardwoods, five softwoods and a wood–polymer compound were examined. Brinell hardness, dynamic hardness, abrasion resistance, and the structural integrity in high-energy multiple impact tests were determined comparatively on dry and wet specimens. A trend was shown where softwoods show a decrease in abrasion resistance with wetting, whilst hardwoods did not. In dry conditions, impact abrasion using steel balls was higher than when using sharp grit. It is suggested that when wet, water in the cells has a hydraulic energy absorbing effect.

Timber exposed in the ground faces most severe conditions in terms of exposure to wetting and fungal decay in the terrestrial environment, therefore wood durability tests are often conducted in test fields preferably ensuring the occurrence of all relevant decay organisms. One can also expect differences in decay within an individual field test site due to localised distribution of certain organisms. Therefore, relevant decay parameters were examined on the newly prepared in-ground test field in Herrenhausen, Hannover: Scots pine sapwood and European beech were exposed to record distribution of decay types, decay intensity and soil parameters. Soft and white rot were found to be dominating. Significant differences of the intrasite variability of decay intensity were observed between wood species and over time. In contrast, differences in decay intensity by different rot types were small. It was concluded that spatial differences in decay intensity were due to localised established fungal flora.

Heat treatment of wood is an effective method by which to improve the dimensional stability and biological durability, but the mechanical strength is decreased at the same time. Besides chemical modification of cell-wall constituents, physical weakening of the microstructure owing to heat-induced defects may also contribute to strength loss. Therefore, anatomical properties of heat-treated beech (Fagus sylvatica L.) and spruce (Picea abies Karst.), studied by light microscopic and scanning electron microscopic analysis, and their interrelation with strength properties and structural integrity were investigated. For determination of structural integrity, the high-energy–multiple-impact (HEMI) test was applied. Microscopic analyses showed frequent formation of radial cracks in heat-treated beech close to the rays as well as tangential cracks in the latewood of spruce. In addition, the modulus of rupture was more affected by the heat treatments than the resistance to impact milling (RIM) determined ...

Climate changes were discussed in many disciplines during recent years. The discussion mainly focused on three aspects: the significance of climate changes, anthropogenic sources for climate changes and finally potential consequences on ecological and economical patterns. This study concentrates on potential impacts of global warming and corresponding moistening on the durability of wooden building components. From experimental test set-ups in the field, climatic data, wood temperature and wood moisture content were used for mathematic modelling of decay. On that basis, a first attempt is made to quantify the influence of climate changes on wood decay rates for various scenarios. It became obvious that warming and humidification will lead to significantly reduced service lives of wooden building components. The quantity of climate induced changes strongly depends on the geographical position and the present climate. Differences between climatically divergent places are shown exemplarily for the si...

The impact of heat-treatment temperature (180, 200, 210, 220 and 240°C) and various heat-treatment durations on selected biological, mechanical, optical and physical properties of thermally modified timber (TMT) was determined. The suitability of different measures for prediction of the treatment intensity was also investigated. Resistance to impact milling (RIM), lightness L*, equilibrium moisture content (EMC), and antiswelling efficiency (ASE) were correlated with corresponding fungal resistance achieved by heat treatments. The results show that the decrease in mass by heat treatments is a suitable measurand to describe the treatment intensity, which is a product of treatment temperature and duration, where the impact of temperature is dominant over the impact of time. The properties examined showed a strong reciprocally proportional relationship with the decrease in mass. Different correlations were found for the various treatment temperatures: the higher the temperature applied, the lower th...

The durability of wood in ground contact is affected by numerous influences, such as substrate quality, climate and microflora of the soil, which need to be considered for the prediction of service life of wooden components to be used in the ground. In this study the influence of different soil substrates on the service life of Scots pine sapwood (Pinus sylvestris L.) and oak heartwood (Quercus petraea Liebl.) was investigated. Mini-stakes were exposed in six different soils at the test site of the Federal Research Centre for Forestry and Forest Products (BFH) in Hamburg, Germany. The effect of partly embedding the test samples in concrete or polyethylene films was also examined. After 3 years of exposure the decay rates for both wood species differed significantly between the soil substrates. Compost soil and fertilized test field soil induced the highest decay activity, whereas in pure sand the lowest decay rates were observed. Surprisingly, exposure in gravel also led to higher decay ratings t...

The need for a reliable database and a corresponding methodology to predict service life of wood and wood-based products emanates from the European Construction Products Directive, as well as from a strong interest by the building industry. A literature review on decay-influencing factors and on previous approaches to implement methods and tools for service life estimations was the basis for a concept for service life prediction of wooden components. The effect of various indirect decay factors was found to be reducible to a few direct decay factors, with material resistance, as well as wood moisture content, wood temperature and their dynamics among the key factors for fungal decay. Approaches that consider only indirect factors, e.g. climate indices, suffer from poor correlation with service life or decay rates. Therefore, the overall consideration of all possible influences, reduced on the key direct decay factors in first instance, is recommended. To fill a theoretical model with a reliable d...