As this is a relatively new field much of the emphasis of this study was on a literature review to help develop a theoretical platform to work from. It was found that the colour of wood appears in the literature in two ways. It appears qualitatively in marketing and value-added research, and it appears quantitatively in colour matching and quality control research. The present research study is the first known occurrence of the quantitative comparison of measured colour with measured consumer preference.
There has been considerable research into character marks in wood. This research has largely been based around traditional hardwoods as the result of increasing scarcity of high grades of lumber. However, more fundamental characteristics such a grain profile, rings per inch, and the presence of visual features such as rays and vessels have not been considered with respect to visual preferences.
Consumer preference data used for this study originated from the study “Consumer visual evaluation of underutilized Canadian wood species” (Fell, 2002). This was chosen as it has a great variety of species to analyze. However, in the survey consumers evaluated the species for overall appearance and not for specific end-uses. Therefore results of the current study are general to wood used in the home and do not apply to specific end-uses.
In order to provide bridge designers with better information, International Forest Products Limited (Interfor) asked the Forest Engineering Resarach Institute of Canada (FERIC) to evaluate the bending strength and stiffness of log stringers used for constructing bridges on forest roads in coastal British Columbia. Given the lack of definitive standards for testing this material, FERIC developed a field-based test procedure and designed a test facility for destructive testing of full-size, whole-log stringers obtained from second-growth stands. Sixteen coastal Douglas-fir and twelve western hemlock logs were tested in 2003. This report describes the test procedure and methods of analysis, presents the log bending strength and stiffness results, and makes recommendations regarding future testing.
Oriented strand board (OSB) is widely used in house construction in North America. In Canada, OSB panels are commonly made of aspen strands and are susceptible to mould and decay when they get wet. Building envelope failures due to mould, decay or poor construction practices can negatively impact the image of wood. This can lead to product substitution that in turn can affect the wood industry’s overall competitiveness. To ensure durability of OSB panels, the most important consideration is the use of mould- and decay-resistant panels to prevent fungal attack. Using low environmental impact technology to improve the durability of OSB products could have market-related advantages over using chemical protection products. This project aimed to develop technologies for protecting OSB raw materials from biodegradation and to explore biological pre- or post-treatments to increase the durability of panels so they would better resist mould, stain and decay.
The project was divided into three parts. Part one involved developing a biological technology to protect OSB raw materials from biodegradation. In this part, aspen, red maple and yellow birch trees, which are commonly used to make OSB in Canada, were felled in May and cut into 4-foot logs. These logs were then equally divided into two groups (16 logs each) with one group keeping its bark and the other having it removed. These debarked and “bark-on” logs were further divided into two groups, each containing 8 logs. One group of logs was treated with a bioprotectant and another group served as a control. The treated and untreated logs were stored separately in Forintek’s yard. Two inspections were conducted, one at the end of the growth season (in October after a 5-month storage period) and the other after one year. During each inspection, four logs from each test group were examined for fungal degradation (mould, stain and decay), and then cut into strands to be used for manufacturing panels. The panels’ physical and mechanical properties and mould resistance were evaluated.
The second part involved developing a biological pre- or post-treatment technology by using naturally resistant wood species to increase the durability of panels so they would better resist mould, stain and decay. In this part, a series of tests were conducted using various wood species. These tests included a) determining the antifungal properties of bark from various wood species; b) using white cedar to improve panel durability; c) optimizing manufacturing conditions for producing durable panels with white cedar; d) using other wood species to produce mould-resistant panels; and e) post-treating panels with extracts of durable wood species.
The third part consists of developing a biological pre- or post-treatment technology by using fungal antagonists to increase the durability of panels against mould, stain and decay. This part will be conducted in the 2004-2005 fiscal year, and results will be included in next year’s report.
The results of the first part on the protection of raw materials showed that all untreated logs, with or without bark, were seriously degraded by moulds, stain and decay fungi after a summer storage period of five months. The logs with bark were more degraded than the debarked logs, and the log ends were more degraded than the middle sections. After summer storage, 55% to 83% of the wood was degraded in untreated logs. The biological treatment was effective, only 4% to 16% of the wood in treated logs was affected by various fungi after a five-month storage period. Furthermore, the biological treatment was more effective on logs without bark than logs with bark, and more effective on yellow birch and aspen than on red maple. After one year in storage, the total infection rates of untreated logs ranged from 68% to 91%, whereas the rate for biologically treated logs ranged from 27% to 49%. Among these treated logs, the logs ends were degraded from 31% to 62%, whereas the middle sections were degraded from 7% to 26%. Strands cut from untreated logs contained 50% to 75% of grey or blue stained strands, whereas those cut from biologically treated logs contained 10% to 25% of such strands. Panels made using biologically treated logs had the lowest TS and WA values compared with panels made using fresh-cut logs and untreated stored logs. The other physical and mechanical properties of the various panels made for this test were comparable.
The antifungal properties of bark from six wood species (aspen, red maple, yellow birch, balsam fir, white spruce and white cedar) were investigated in the second part of this research project. Based on the colony growth rate of moulds, stain and decay fungi on bark-extract-agar media, white spruce bark was the best at inhibiting growth of these fungi, followed by red maple bark. White cedar and balsam fir bark somewhat inhibited certain fungi tested. Aspen and yellow birch bark did little or nothing at all to inhibit fungal growth. The research also showed that the white cedar heartwood-extract-agar medium not only inhibited decay fungi growth, but also inhibited the growth of moulds and staining fungi. The bark-extract-agar medium of this wood species was less effective in inhibiting fungal growth than the heartwood was.
Three-layer panels made using white cedar heartwood strands in the face layers and aspen strands in the core layer at a ratio of 25:0:25 were mould and decay resistant, but the panels “blew” easily during manufacturing and their mechanical properties were not satisfying. The overall mould infection rate on white cedar heartwood-faced panels was 0.8, which indicated that the panel was mould resistant. White spruce heartwood-faced panels were highly mould resistant and moderately decay resistant. The overall mould infection rate on white spruce heartwood-faced panels was only 0.2 after 8 weeks of exposure to high humidity environmental conditions. In addition to being mould resistant, white spruce heartwood-faced aspen panels also had better IB, MOR and MOE properties, compared with aspen panels. The panels with black spruce in surface layer had mechanical and mould-resistance properties that were similar to those with white spruce in surface. The panels with surface layer of Eastern larch heartwood were non-resistant to moulds and slightly resistant to decay, but they had better IB, TS and WA properties compared with the other types of panels. The overall mould infection rate on the panel with surface layer of Eastern larch heartwood was 3.7, which was similar to the rate for aspen control panels. Aspen panels (serving as control panels) were seriously affected by moulds with overall mould infection rates ranging from 3.8 to 4.9.
Aspen panels with surface layer from whole-wood strands (using both sapwood and heartwood) from white cedar, in a ratio of 25:50:25 and pressed at 220°C for 150 seconds, were well bonded and had IB, TS, WA and MOE values that were similar to those of aspen control panel, but with a higher MOR. All the panels’ properties met the requirements of the standard. This type of panel also was the least infected by moulds, especially in the face layers which rated a 0.2. The panel sides were moderately infected, rating a 2.6, this occurring mostly in the middle layer of aspen strands. The overall rate of this type of panel was 1.0, which indicated that the panels were resistant to mould infection. This type of panel was also highly resistant to brown rot and moderately resistant to white rot.
Panels made of steam-treated white cedar whole-wood strands and aspen strands at a ratio of 3:7 based on oven-dry weight also had low infection rates: the average face infection rate was 1.2; the side infection was 2.4 and the overall rate was 1.6. Compared with aspen panels, this type of panel also had high MOR and MOE values and low TS and WA values.
In the case of white cedar whole-wood strands faced aspen panels, when the pressing time was increased from 160 seconds to 180 seconds at 200°C, the panels’ IB strength and MOE increased whereas the panels’ TS, WA and MOR decreased. By increasing the pressing temperature from 200°C to 240°C and pressing for 160 seconds, the panels’ IB strength, MOR and MOE increased and the panels’ TS and WA decreased sharply. At a pressing temperature of 240°C and a pressing time of 180 seconds, the panels’ IB strength, MOR and MOE increased significantly and the panels’ TS and WA decreased significantly. These data showed that aspen panels with surface layer from white cedar whole strands at a ratio of 25:50:25 and pressed at 240°C for 180 seconds had the best mechanical and physical properties. All panel samples were slightly infected by moulds on the faces. A fair amount of mould occurred on the sides of panels pressed at 200°C for 160 seconds and 180 seconds and those pressed at 240°C for 180 seconds. The panels pressed at 240°C for 160 seconds were the least infected by mould (with an infection rate of 0.3). Panels pressed at 200°C had a white-yellowish colour, whereas those pressed at 240°C were yellow-brownish and darker than those pressed at 200°C. Panels pressed at 200°C for 160 or 180 seconds and those pressed at 240°C for 160 seconds were highly decay resistant, especially to brown rot. The decay resistance of panels pressed at 240°C for 180 seconds was lower compared with the other panels.
Compared with aspen panels, panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 7:3 based on oven-dry weight had higher TS, WA, MOR and MOE values and a similar IB value. Panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 4:6 based on oven-dry weight had the highest IB value. A reduction in mould and decay resistance corresponded to a reduction in the proportion of white cedar strands in the face layers. The overall mould growth rate was 1.27 on panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 4:6, 0.6 on panels with surface layer from steam-treated white cedar strands and aspen strands at a ratio of 7:3, and 0.4 on panels faced with 100% white cedar whole strands, respectively.
Panels made from 100% white cedar whole-wood strands or a mixture of whole-wood strands of white cedar and aspen (50:50) in the core layer were “blown” after pressing. Panels made from a mixture of white cedar and aspen strands at a ratio of 25:75 in the core layer and aspen strands in the face layers had superior IB, MOR and MOE values than other panels. However, their TS and WA values were also higher than those of white cedar-faced panels. Panels made from a mixture of white cedar and aspen strands at a ratio of 25:75 in the core layer and white cedar strands in the face layers had the worst physical and mechanical properties among all the panels made for this test. The tests results for mould showed that panels made with a mixture of white cedar and aspen strands at a ratio of 25:75 in the core layer and aspen strands in the face layers ware seriously attacked by moulds and had an overall mould growth rate of 4.2. No mould infection was found on panels made from 100% white cedar strands. Panels made from a strand mixture of white cedar (50%) and aspen (50%) in the core layer and white cedar strands in the face layers had little mould infection. The overall mould growth rate on this type of panel was 0.2.
Compared with the control aspen panels, aspen panels with surface layer from white cedar whole-wood strands at a ratio of 15:70:15 had similar IB and TS values, a lower WA value and higher MOR and MOE values. When the white cedar strand proportion in the face layer was increased from 15% to 25%, the panels’ IB strength and WA decreased, but their MOR and MOE values increased. Panels with surface layer from white cedar strands at a ratio of 15:70:15 had little infection from moulds on the face and bottom layers, but had an increased infection rate on all four sides. The average overall infection rate of this type of panel was 0.5. When the white cedar in the panels’ face layer was increased from 15% to 25%, the average infection rate on the panels’ faces was still 0.1, but the infection rate of the panels’ sides dropped from 1.2 to 1.0. The overall rate was 0.4. In terms of decay resistance, panels with surface layer from 25% white cedar strands performed better than those with surface layer from 15% white cedar.
This project aimed to develop technologies for protecting OSB raw materials from biodegradation and to explore biological pre- or post-treatments to increase the durability of panels so they would better resist mould, stain and decay. The project was conducted in five parts. Part one involved developing a biological technology to protect OSB raw materials from biodegradation. The results of this part of the work showed that all untreated logs, with or without bark, were seriously degraded by moulds, stain and decay fungi after a summer storage period of five months. The logs with bark were more degraded than the debarked logs, and the log ends were more degraded than the middle sections. After summer storage, 55% to 83% of the wood was degraded in untreated logs. The biological treatment was effective, only 4% to 16% of the wood in treated logs was infected by various fungi after a five-month storage period. Furthermore, the biological treatment was more effective on logs without bark than logs with bark, and more effective on yellow birch and aspen than on red maple. After one year in storage, the total infection rates of untreated logs ranged from 68% to 91%, whereas the rate for biologically treated logs ranged from 27% to 49%. Strands cut from untreated logs contained 50% to 75% of grey or blue stained strands, whereas those cut from biologically treated logs contained 10% to 25% of such strands. Panels made using biologically treated logs had the lowest thickness swelling (TS) and water absorption (WA) values compared with panels made using fresh-cut logs and untreated stored logs. The other physical and mechanical properties of the various panels made for this test were comparable. For the mould resistance, all panels made from fungal treated logs had better mould resistance than those made from freshly cut and untreated logs. Panels made of strands cut from fungal treated debarked logs had better mould resistance than the panels made from fungal treated bark-on logs.
The second part of the research consisted of investigating antifungal properties of barks from various wood species. In this part, antifungal properties of barks from 6 wood species: aspen, red maple, yellow birch, balsam fir, white spruce and white cedar were screened in a laboratory test against moulds, staining fungi, white-rot and brown-rot fungi. Based on the colony growth rate of moulds, stain and decay fungi on bark-extract-agar media, white spruce bark was the best at inhibiting growth of these fungi, followed by red maple bark. White cedar and balsam fir bark somewhat inhibited certain fungi tested. Aspen and yellow birch bark did little or nothing at all to inhibit fungal growth.
The third part involved developing a biological treatment technology by using naturally resistant wood species to increase the durability of panels so they would better resist mould, stain and decay. In this part, a series of tests were conducted using various wood species. These tests included a) using white cedar to improve panel durability; b) optimizing manufacturing conditions for producing durable panels with white cedar; and c) using other wood species to produce mould-resistant panels. The results showed that three-layer panels made using white cedar strands in the face layers and aspen strands in the core layer at different ratios were mould and decay resistant. White spruce heartwood-faced panels were highly mould resistant and moderately decay resistant. In addition to being mould resistant, white spruce heartwood-faced aspen panels also had better internal bond (IB), modulus of rupture (MOR) and modulus of elasticity (MOE) properties, compared with aspen panels. The panels with black spruce in surface layer had mechanical and mould-resistance properties that were similar to those with white spruce in surface. The panels with surface layer of Eastern larch heartwood were non-resistant to moulds and slightly resistant to decay, but they had better IB, TS and WA properties compared with the other types of panels.
The fourth part of the research consisted of developing a biological treatment technology by using fungal antagonists to increase the durability of panels against mould, stain and decay. In this part, two major tests were conducted using various fungal species. They were: a) treating wood strands with three antagonistic fungi, Gliocladium roseum, Phaeotheca dimorphospora and Ceratocystis resinifera, to increase OSB panel durability; and b) treating wood strands with a lignin-degrading fungus, Coriolus hirsutus, to reduce OSB resin usage. The results of this part of the work showed that all of the 4 fungal species used grew well on aspen strands in four weeks, and strands in all treatments had normal wood color after incubation. For IB property, panels made of fungal treated strands were better or similar to the control panels. Panels made of fungal treated strands had higher TS and WA values than untreated control panels. For mechanical properties, panels made of fungal treated strands had a slight lower dry MOR and higher wet MOR than control panels. For mould resistance, panels made of fungal treated strands were infected by moulds one week later than the untreated control panels, and reduction of mould infection rates was detected on fungal treated panels within 6 weeks. After 6 weeks, all panels, treated or untreated, were seriously infected by moulds. Reducing resin usage in fungal treated panels did not affect panel density. Compared with untreated control panels, the IB property of panels made of fungal treated strands was slightly increased by using normal dosage of resin or a reduced dosage by 15%, but slightly decreased with a resin reduction by 30%. There was a negative linear correlation of the panel TS and WA properties with resin reduction by using fungal treated strands. For the mechanical properties, panels made of fungal treated strands had lower dry MOR and MOE values, but higher wet MOR values (except for a resin reduction of 30%) than panels made of untreated strands.
The fifth part involved protecting OSB against mould and decay by post-treatment of panels with natural extracts from durable wood species and from fungal antagonists. In this part, three tests were conducted using extracts of white cedar heartwood and extracts of a fungal antagonist. These tests were: a) screening antifungal properties of natural extracts against mould and decay fungi; b) post-treating OSB panels with white cedar heartwood extracts and finishing coats; and c) post-treating OSB panels with fungal metabolites. The results of this part of the work showed that the mycelial growth of all fungi tested (moulds, staining fungi, white-rot and brown-rot fungi) was inhibited by the extracts of white cedar heartwood and extracts of the fungal antagonist, P. dimorphospora, on agar plates. Panel samples dipped with the cedar extracts got slight mould growth on the 2 faces and moderate mould growth on the 4 sides, whereas the panel samples dip-treated with the fungal extracts got the minimal mould infection among the panels tested. The results of the mould test on the post-treated panels with extracts of white cedar heartwood and three coating products showed that slight or no mould growth was detected on any sample dip-treated with the extracts and then brushed with finishing coats. The decay test showed that most post-treated samples had less weight losses than untreated control samples.
This study expands geographically on past work on material preferences for decks in Vancouver, Calgary, and Edmonton (Fell and Gaston, 2001). In the fall of 2003 over 1,300 consumers were interviewed at home shows in Toronto, San Diego, Atlanta, and West Springfield (MA). Preferences for deck materials, expected lifetimes, annual maintenance requirements, and price were evaluated using conjoint analysis which explores the tradeoffs consumers are willing to make to get the product that best suits them.
This study differs in other aspects than region from the Fell and Gaston (2001) study. Most importantly, three years have passed since the last study. Since then decking, specifically that treated with CCA, has become a prominent issue in the media. At the same time redwood harvests are down and western redcedar entering the US faces duties. Finally, awareness of wood plastic lumber and its availability have increased. For these reasons major differences from the 2001 study were expected.
It is interesting that after all the changes to the dynamics of the decking market since 2001, the basic desires of consumers remain the same. Consumers rate material type and expected lifetime of a deck to be the most important attributes. Price and maintenance requirements are secondary requirements. These results are almost identical to those seen in 2001. The practical implications of this result are that consumers appear willing to pay more and do more maintenance for a deck they expect to last longer.
Where the most profound differences are to be found is with respect to material. In 2001 (Western Canada) treated wood was of almost equal preference to naturally durable wood, with wood plastic composites being viewed very negatively. Three years later treated wood has a negative perception, and wood plastic is perceived positively in all but one of the study cities.
Naturally durable wood remains the material of choice overall. It was especially popular in Toronto. Toronto was the only city where wood plastic was had negative preference. In view of the 2001 results in Western Canada this may indicate that Canada as a country is less open to wood plastic composites than the US. Wood plastic was most positive in Massachusetts where it was preferred to naturally durable wood. Finally, treated wood was viewed least negatively in Atlanta and Toronto.
The goal of this project, carried out at Forintek’s Quebec MDF Pilot Plant, was to develop an enhanced fibreboard product for exterior applications. The experimental work consisted of three different phases. Phase I consisted of selecting a suitable resin system from among five types of resin exposed to the same process conditions. Panels produced with the MUPF resin (resin R03) had the best overall moisture resistance and dimensional stability properties. Phase II defined optimal refining and hot pressing process conditions. Based on the experiment results and statistical analysis, a numerical optimization was carried out using Design Expert® computer software. Phase III examined the chemical modification of wood fibre by acetylation. The following conclusions can be reached from this research project:
Among the five different resin systems, resin R03 (an MUPF resin) produced the best overall panel properties for moisture resistance and dimensional stability and was most cost effective.
For resins R03 and R04 (MUF), post-press heat treatment showed marginal improvements in panel bonding strength, moisture resistance, and dimensional stability.
Panels made with MDI resin were comparable to R03 panels in terms of dry IB, but resulted in lower water resistance (lower one-hour boiling IB).
With resin R03, panel series S7 had the best overall panel properties among the 8 different types of panels made under the different process conditions.
Resin content of R03 in the panel had the greatest effect on IB, water resistance, and dimensional stability.
Higher steam temperature in the preheater improved panel moisture resistance and dimensional stability.
All properties tested in S7 produced results higher than those typical of wood plastic.
The cost to produce S7 is about 40% of the cost of wood plastic panels for similar applications.
Acetylated wood fibre demonstrated a great improvement in water resistance and dimensional stability. However, further research is required in order to find better adhesives and application methods to optimize MDF panel processes with acetylated fibre.
Wood fibre-based panel can replace wood plastic for exterior applications at a significant cost advantage.
Further work is required to optimize the process and to fully evaluate panel properties under long term outdoor conditions.
Western redcedar (WRC) is renowned for its high durability, which is due at least in part to the presence of extractives that are toxic to decay fungi. Western redcedar's naturally low equilibrium moisture content (EMC) may also be a protective factor, since fungi typically require 30% moisture content to grow. Extractives are thought to contribute to the low EMC by blocking water adsorption sites on the wood. The present work compared the EMC of extracted and un-extracted WRC heartwood and sapwood. Extracted WRC heartwood had higher EMC than un-extracted WRC heartwood in samples not affected by fungi, and WRC sapwood had higher EMC than adjacent heartwood. The presence of extractives was identified as being associated with the low EMC of WRC heartwood in these samples.
Establishing the optimum panel densification for performance plywood/LVL products - new method developed to measure veneer quality and bondability. Final Report 2004/05
In this study, extensive veneer compression tests were conducted to examine the transverse compression behaviour of veneer at both ambient and controlled temperature and moisture content (MC) environments. Based on the results, a novel method was developed to characterize overall surface quality of veneer and other wood materials in terms of their bondability and compression behaviour.
The method would have significant implication in both theory and practice. In theory, the general wood compression theory would need to be modified. The revised wood compression theory would include four stages instead of commonly defined three. The first stage, which has long and so far been overlooked but is critically important, could be named as “non-linear conformation”. During this stage, the contact area increases nonlinearly with the load applied. It is this stage that directly reveals the interfacial bonding behaviour of wood materials such as veneer-to-veneer and strand-to-strand and their minimum compression required for achieving adequate contact (bonding). In practice, the method provides a fast and objective way of evaluating surface roughness/quality of veneer and other wood materials. The new method also establishes the maximum compression allowable for achieving the best panel performance in terms of bonding strength, stiffness and dimensional stability. Based on the concept of this method, it was further found that both minimum compression required and maximum compression allowable are independent of temperature and MC, which provides a direct benchmark to the material recovery during panel hot-pressing.
In a case study with Trembling aspen veneer, the variation of veneer surface roughness/quality and its effect on resulting material recovery were first revealed. Then, the optimum panel densification was identified for performance plywood and LVL products based on the frequency distribution of the minimum compression required and the maximum compression allowable. Finally, an overall veneer quality index was established to compare veneer overall quality for different species/thickness. The method shows good potential in practical applications for increased material recovery, reduced glue consumption and improved panel performance.
The seismic and wind design provisions for engineered wood structures in Canada have to be enhanced to be compatible with those already available for structures built according to other material standards. Such design provisions are of vital importance for ensuring the competitive position of timber structures relative to reinforced concrete and steel structures. This report provides information on the framework needed for development of such enhanced provisions for design of lateral load resisting systems in engineered wood buildings. Although the framework presented here is suggested for implementation in the Canadian wood design standard (CSAO86) in correlation with the National Building Code of Canada (NBCC - the Canadian model design code), the information provided can be used as a template for other national and international codes and standards.
In the beginning, a comprehensive review on the development of the seismic design procedures in Canada and the US is presented. This is followed by the information on seismic design principles and methods of seismic analysis throughout the world. In addition, a state-of-the-art survey is included on the development and current activities related to the performance based design procedures throughout the world. This is followed by the details that should form the new design section on lateral load resisting systems (LLRS) to be developed in CSAO86 during the next code cycle. It is suggested that in response to the changes already in place in the 2005 edition of the NBCC, besides systems such as shearwalls and diaphragms, the section should include subsections for braced frames and moment resisting frames. It is also suggested that a strong link should be made between the design section on connections and the new one on LLRS. Future editions of the CSAO86 should also be encouraged to use the reliability and performance based design provisions, as the codes in the area of seismic design worldwide are moving in that direction.
There are several ongoing research activities in the field of wood-based lateral load resisting systems and connections throughout Canada and the US. Cooperation between researchers, engineering community and regulatory representatives is vital for successful delivery of the design guidelines mentioned above.
