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The effect of biodeterioration on the structural connection performance of timber for conventional framing and mass timber has been investigated recently, but there is a need for additional data as well as for the development of analytical models to utilize these data. An empirical material model (seismic analysis of wood frame shear walls) was fitted to cyclic connection test data of four species of cross-laminated timber at different levels of biodeterioration by two brown-rot fungi. These model inputs were then analyzed to account for trends between wood species and fungal species. Weak trends were most prominent for initial stiffness, intercept load, and displacement at peak force. Correlations were poor with postyield and postpeak stiffness modifiers. These relationships were consistent both as a function of time and as a function of mass loss, but additional data are needed to more accurately predict the effects. The limited relationships likely reflect the variations in fungal decay across the test members., One of the most used materials in the shift to mass timber construction has been cross-laminated timber (CLT). Substantial research has gone into structural characterization and design with CLT, ranging [...]

Cross laminated timber (CLT) is a mass timber product that is gaining popularity in construction within North America. CLT is made up of wood, a building material of biological origin. Therefore, these materials are at a risk of decay upon intrusion of moisture, a situation that could lead to loss of confidence in the material. Ensuring durability and optimum performance of building elements throughout their expected service life will require an understanding of the potential for decay and the possible consequences. This paper reviews the various possibilities of moisture intrusion in CLT, their potential effects on the physical and mechanical properties of CLT, and ultimately the associated biological decay risks. The paper concludes by enumerating variables that are critical and should be evaluated to completely understand decay in CLT panels, stemming from a thorough review of previous studies and methods used to evaluate decay in mass timber., Timber construction is one of humankind's earliest methods of building. Woods (2016) suggested that many homes built over 10,000 years ago were constructed with timber as the primary construction material. [...]

The effect of pretreatment with either boron or glycerol followed by thermal modification on the durability of Douglas-fir heartwood was evaluated in an American Wood Protection Association ground proximity test in Hilo, Hawaii. Non-thermally modified samples were generally more heavily decayed than any of the modified woods, but there was no consistent effect of different thermal modification conditions on decay resistance. Thermally modified woods tended to perform better than untreated timbers but not as well as copper azole-treated Douglas-fir heartwood lumber in test at the same site. The results are discussed in relation to how the extreme site conditions might have made it difficult for thermally modified materials to perform., Thernial modification is a long-established method for altering the resistance of timber to moisture uptake, thereby resulting in conditions that are presumably less conducive to fungal attack (Esteves and Pereira [...]

Rapid Ohia Death is a major concern for the viability of ohia (Metrosideros polymorpha) in Hawaii and has led to restrictions on log movement. The potential for using disodium octaborate tetrahydrate (DOT) and didecyl dimethyl ammonium chloride (DDAC) dip diffusion treatments to control the two causal fungi (Ceratocyslis lukuohia and Ceratocystis huliohia) was investigated. A 10 percent boric acid equivalent dip diffusion treatment killed the pathogens in 0.5-cm-thick disks obtained from 4.0- to 5.0-cm-diameter limbs of naturally colonized trees. DOT tended to diffuse more consistently in 50- to 60-cm-long bolts of small (4.0 to 9.0 cm) and large (9.1 to 17.0 cm) diameter healthy ohia compared with those bolts naturally infected by C. lukuohia. Diffusion periods longer than 6 weeks resulted in deeper penetration. Immersion (24 h) of logs (1.3 m long; 9 to 17 cm diameter) from C. lukuohia artificially inoculated trees in two forest locations in a 15 percent DOT/1 percent DDAC solution and storage for 10 weeks before evaluation resulted in incomplete elimination of the pathogen and lower boron concentrations in the inner sapwood than outer. Further investigations are needed to explore using either higher boron concentrations or longer diffusion periods to deliver fungicidal concentrations of boron deeper within the wood matrix., The Hawaiian keystone tree ohia (Metrosideros polymorpha Gaudich.) is under attack by two newly discovered fungal pathogens, Ceratocystis lukuohia I. Barnes, T.C. Harrin, and L.M. Keith and Ceratocystis huliohia I. [...]

Wooden crossarms play a major role in supporting electric distribution lines in North America, but relatively few data exist on their condition as they age. The residual capacity of Douglas-fir crossarms in service in western Oregon for 45 to 60 years was investigated. Arms were sampled for residual preservative retention, the presence of visible decay fungi, and residual flexural properties; these results were then compared with three nondestructive tools. A majority of the arms tested had preservative levels well below those required for new arms, but only one decay fungus was isolated, and only five arms removed and dissected had any evidence of visible internal decay. Moduli of rupture for the arms were generally below the minimum levels required by national standards, but most still retained at least 67 percent of this value. Nondestructive evaluation tools were generally poorly correlated with flexural properties, possibly because of the heavily weathered and checked exterior condition., Crossarms are widely used on electric utility poles in North America to support the wires and create separation between the electrical phases. Although a variety of materials can be used [...]

The performance of several wood surface treatments as well as a silica treatment claiming to provide protection against fungal decay and termite attack in aboveground applications were examined in termite, ground proximity, and sandwich tests at a subtropical site near Hilo, Hawaii. In general, the surface treatments performed similarly to untreated controls and provided little or no protection against fungal or insect attack. The silicate treatment provided some termite and decay protection, but fungal decay resulted in rapid declines in condition after 50 to 54 months of exposure. Copper azole--treated lumber provided the best performance against both termites and fungal attack, illustrating the benefits of pressure treatment over surface treatments in highdecay-hazard environments. These results also illustrate the importance of rigorous testing and standardization protocols for any product that makes durability claims before it enters the market to ensure that it will perform as expected., Wood exposed aboveground in exterior applications is invariably subjected to wetting that creates conditions conducive to fungal attack. Extending the useful life of timber requires either using naturally durable heartwood [...]

Copper remains one of the key biocides for protecting timber in soil contact. Historically, copper-based preservatives relied on solubilized copper. Over the past decade, micronized copper systems have largely replaced soluble copper systems in this application. While micronized copper chemistries have been shown to perform well over time with reduced copper leaching compared to solubilized copper, data are lacking on the effects of repeated leaching cycles on resistance of the timber to fungal attack. The potential effects of repeated leaching cycles of micronized copper azole--treated southern pine (Pinus spp.) blocks on both copper losses and resistance to fungal attack were explored over 20 leaching cycles using Gloeophyllum trabeum and Rhodonia placenta as test fungi. Copper losses during leaching were elevated for the first two cycles and steadily declined with additional cycling. There were no noticeable differences in fungal-associated weight losses in blocks exposed to G. trabeum. There was only a slight increase in average block weight losses with R. placenta, although blocks exposed to this fungus experienced higher weight losses with increased leaching cycles. The results suggest that repeated leaching exposures may produce some localized increases in susceptibility to fungal attack, but the overall effects were minor., Chopper remains among the most widely used components for wood preservatives employed in ground contact. Copper reacts slightly with the wood and has broad spectrum activity against fungi and insects [...]

The properties of several modified wood products were evaluated using North American standards to provide comparative data for architects seeking to use these materials. In general, modified wood products had lower moisture uptakes and less shrinkage than unmodified products. Acetylated materials were highly resistant to fungal decay, whereas thermally modified and furfurylated materials were classified as decay resistant. All materials were susceptible to mold, although the nonacetylated moisture-resistant medium-density fiberboard was most susceptible. Thermally modified and furfurylated materials were similar in mold susceptibility to untreated radiata pine sapwood, whereas acetylated materials appeared to be more mold resistant., wood is among the most durable natural cellulosic polymers, but it is susceptible to biological degradation under the proper temperature, moisture, and oxygen conditions (Zabel and Morrell 1992). The heartwood [...]

Internal decay is a common problem in poles or timbers of thin sapwood species. Several internal treatments have been developed to arrest this attack, and these systems are widely used in North America. Although these treatments have been evaluated in numerous independent field trials, there is no single test of all treatments. The objective of this study was to assess the chemical distribution and fungal colonization in Douglas-fir poles treated with each of 13 different internal remedial treatments over a 10-year period. Metam sodium treatments provided the shortest protective period, with little evidence of residual chemical 3 years after treatment. Methylisothiocyanate (MITC) in pure form provided a very high initial flush of active ingredient and a longer protective period extending from 5 to 8 years after treatment. Dazomet, which must decompose to produce MITC, took slightly longer to reach effective levels, but was still present at effective levels 10 years after treatment. Chloropicrin, which has strong interactions with wood, was associated with the highest chemical levels after 10 years. Borates took longer to reach effective levels in the poles and their protective zone was narrower than the fumigants, but boron was still present at effective levels 10 years after application. The results illustrate the different properties provided by each treatment, but also show that all tested remedial treatments were effective within certain limitations., Pressure treatment of large timbers and poles of thin sapwood species generally produces a shallow shell of protection surrounding the untreated heartwood core (Graham 1983). The treatment remains protective if [...]

The potential for using a low molecular weight polyethylene (PE) polymer to improve the properties of creosote-treated wood was evaluated on samples of six different wood species. Samples were impregnated with creosote alone or amended with the PE additive and then tested to failure in third-point loading to determine modulus of elasticity and modulus of rupture. Samples were then subjected to three soak--dry cycles to assess the impact of moisture uptake on fastener performance or water repellency. The presence of the PE was associated with lower preservative retentions, but had no significant effect on modulus of elasticity, modulus of rupture, water repellency, or fastener withdrawal resistance. The results suggest that the additive limited preservative uptake, but did not improve any of the wood properties evaluated., Creosote has a long history of successful use as a wood preservative (Hartford 1973). One of the primary uses for creosote is the treatment of wood for railroad applications. Creosote [...]

Chloropicrin remains one of the most effective fumigants for arresting internal decay in large timber structures, but it can be difficult to handle. The potential for encapsulating chloropicrin to improve application safety and control the release rate was investigated in Douglas-fir poles. A quick-release ampule resulted in chloropicrin levels that were similar to those found with a similar amount of liquid chloropicrin, whereas moderate- and slow-release ampules resulted in proportionally less chloropicrin in the wood over a 4-year period, but levels were still well above the protective threshold. The results suggest that encapsulated chloropicrin improved handling safety without reducing performance. Further monitoring is planned., The development of internal decay in utility poles can markedly shorten the expected service life of a pole (Graham 1973a, 1973b, 1983). Several treatments have been developed for arresting fungal [...]

Phytophthora ramorum is an increasingly important tree pathogen in northern California and southern Oregon. While it has the greatest effect on tanoak, it can infect a wide range of tree species, including Douglas-fir. Oregon has instituted a quarantine area to slow the spread of this pathogen, and there are concerns that further restrictions may be imposed on log movement, including those of Douglas-fir. The potential for using boron as a log treatment to limit P. ramorum was evaluated. While boron either alone or in a glycol solution was capable of moving into the bark, there was no evidence that it could move further into the sapwood. The results suggest that bark removal would be necessary for the use of boron as a mitigation agent for the spread of P. ramorum., The global movement of plant materials carries with it the risk of unintended transportation of potential plant pathogens (Morrell 1995; Pimentel et al. 2000; Food and Agriculture Organization of the [...]

Abstract The potential for limiting fungal attack on red alder (Alnus rubra Bong.) pallet stock was evaluated in a small-scale field test. Alder is extremely susceptible to biological attack, as [...]

Abstract Wood guardrail posts are the most common wood materials currently used in highway construction. Maintenance crews and engineers are often faced with the challenge of rapidly assessing the extent [...]

Abstract Most thermal modification studies have attempted to improve the durability of sapwood; however, it may be more fruitful to improve the durability of heartwood that already has some inherent [...]

Abstract The potential for using pretreatment with cinnamon leaf oil or juniper foliage oil to improve the durability of viscoelastic thermal compression (VTC)-treated hybrid poplar was explored in a field [...]

The performance of western hemlock, sugar pine, and western larch as alternatives to western redcedar (WRC) for roof shingles was investigated on outdoor roof racks with and without an initial brush or dip treatment with either pentachlorophenol (penta) or chromated copper arsenate (CCA). Untreated shingles of all species experienced degradation over a 32-year exposure in western Oregon, but WRC provided the best performance. Penta treatments improved performance to some extent, but the best protection was provided by a dip treatment in CCA prior to installation. The results illustrate the benefits of even shallow surface protection in aboveground exposures., Western redcedar (Thuja plicata Donn) has long been used for roof shingles and shakes because its heartwood has a well-known reputation for both durability and dimensional stability (Scheffer and Morrell [...]

Abstract Routine inspection of wood utility poles to detect internal decay involves drilling holes at or about the ground line. While these holes are useful for detecting internal decay, their [...]

Abstract Red oak, Douglas-fir, and ponderosa pine lumber was treated with a silicon/paraffinic system to assess the ability of the treatment to limit dimensional changes and moisture uptake during changes [...]

Abstract The Chinese market represents good opportunities for those interested in exporting building materials, including wood products. One growing building material sector is preservative-treated wood. Fewer than 70 treatment facilities [...]

Abstract A solid, crystalline fumigant (dazomet) with and without a supplemental copper compound was evaluated as an internal decay control treatment on Douglas-fir poles in two long-term field tests. Methylisothiocyanate [...]

Abstract The amounts of treated wood present at a wood recycling center in western Oregon were surveyed over a 10-year period. Treated wood was found at 106 of 112 inspections, [...]

Public awareness of resource scarcity and environmental protection has steadily increased during the past three decades. This awareness has been heightened by the public debate of issues such as global [...]

Abstract A survey was conducted to determine the use of antistain chemicals by western softwood lumber producers in 2006. Half of those surveyed responded, and 31 percent of the respondents [...]

Abstract The potential for migration of boron from wood pressure-treated with disodium octaborate tetrahydrate (DOT) during rainfall events was assessed using sawdust, small blocks, and sections of Douglas-fir boards. Boron [...]

Abstract The physical and chemical changes of wood-plastic composites (WPC) were examined after 10 years in field (stake and ground proximity) tests at a tropical site near Hilo, Hawaii. The [...]

Abstract Understanding how silvicultural treatments and changes in the forest resource will affect wood quality characteristics, including heartwood natural durability, is a critical need for forest managers. Because heartwood properties [...]

Abstract The rate of discoloration of Douglas-fir sapwood by two Ophiostoma species introduced through bark wounds was assessed in three separate trials over a 1-year period. Discoloration was most rapid [...]

Abstract Creosote has a long history of successful use as a wood preservative, but polycyclic aromatic hydrocarbons in this preservative have raised environmental concerns, particularly when creosote-treated wood is used [...]

Abstract The thresholds of boron and fluoride against selected decay fungi (Postia placenta, Gloeophyllum trabeum, and Trametes versicolor) were determined in Douglas-fir sapwood and heartwood in non-soil contact exposures. Even [...]

Abstract The ability to treat Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) with oilborne copper-8-quinolinolate or with waterborne chromated copper arsenate, ammoniacal copper zinc arsenate, or ammoniacal copper [...]

Abstract Molds are an increasingly important issue for all building materials, including wood. While washing with bleach is a commonly recommended method for removing molds, and the associated discolorations, there [...]

Supercritical carbon dioxide is ideally suited as a treatment fluid for porous solids. Supercritical fluids have a high diffusivity and low viscosity. As such, they have the right physiochemical properties for solvent use. The supercritical fluid chemical deposition technique used to create the solutes fernesyle acetate and 2-(thiocyanomethylthio)-benzothiazole is described.

Abstract The effects of rainfall exposure on panel integrity were investigated for oriented strandboard and plywood. Both panel materials experienced substantial increases in moisture content and thickness with limited rainfall [...]

Abstract The residual protective effect of sodium n-methyldithiocarbamate (NaMDC) fumigant was investigated in Douglas-fir timbers in a bridge in western Oregon using fungal colonization and levels of methylisothiocyanate (MITC; the [...]

Abstract Steam-distilled essential oils from western juniper (Juniperus occidentalis) foliage and twigs were tested for activity against subterranean termites and fungi. Foliage residues were pretreated with dilute sulfuric acid and [...]

Abstract The effect of metal end plates on reducing checking of pentachlorophenol-treated Douglas-fir crossarms was evaluated over 13 wet-dry cycles. Check development was variable over the first three to four [...]

Abstract Preservative treatments are required whenever glued laminated beams are exposed outdoors. Treatments can be either water-based systems applied to individual laminations prior to layup or organic solvent--borne systems applied [...]

Abstract The resistance of three naturally durable heartwood species and a stranded giant bamboo product to fungal and termite (Coptotermes formosanus) attack was evaluated at a test site located near [...]

Abstract The effect of copper naphthenate treatment on electrical resistance of Douglas-fir utility poles was compared with similar poles either left untreated or treated with pentachlorophenol (penta). Penta-treated and untreated [...]

Abstract Oriented strandboard (OSB) manufacturers have developed 'enhanced' OSB subfloor products that they claim have improved thickness swell properties. Examples of these enhanced OSB panels were found to have reduced [...]

Abstract A method for analyzing fluoride in wood by extraction in place of ashing was evaluated with Douglas-fir heartwood and ponderosa pine sapwood treated with various levels of fluoride. Although [...]

MATTHEW E. ANDERSON [* ] ROBERT J. LEICHTI [*] JEFFREY J. MORRELL [*] ABSTRACT The effects of three supercritical fluid (SCF) treatment parameters on the bending properties and development of [...]