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Ultra-structural observations on the degradation of wood surfaces during weathering
1987 - IRG/WP 2280
Radiata pine (Pinus radiata D. Don) sapwood was converted into blocks with a transverse face about 5 mm square and measuring 8 mm longitudinally. Transverse (T.S.), Radial (R.L.S.) and Tangential (T.L.S.) surfaces were prepared and specimens exposed to the weather inclined at 45° facing equatorially for periods of between 20-60 days. After 30 days exposure erosion of the middle lamella was observed followed after 40 days exposure by extensive separation of individual fibres at the interface of the middle lamella and secondary wall. Degradation of the S2 layer of the cell wall revealed corrugations orientated parallel to the fibre axis suggesting preferential removal of cell wall components. Further degradation proceeded by progressive delamination and checking of the S2 and erosion of the S3 cell wall layer. In addition to the above changes preferential degradation of the rays was observed in radial (R.L.S.) and tangential (T.L.S.) longitudinal surfaces.
P D Evans, S Thein


Long-term performance of a "wax" type additive for use with water-borne pressure preservative treatments
2000 - IRG/WP 00-40159
Field performance results are updated for matched CCA treated decking boards with and without an emulsion water repellent additive incorporated with the initial pressure treatment. Decks have been exposured for over 9 years in Harrisburg, NC. Boards were evaluated for in-service and laboratory performance for water repellent efficacy, as well as additive loadings in the boards after this exposure. All results support that these additives can provide long-term protection against many of the physical defects that develop in pressure treated wood during exposure.
A R Zahora


Performance results of wood treated with CCA-PEG
1986 - IRG/WP 3363
The addition of polyethylene glycol (PEG) to the CCA system has been shown to reduce the surface hardness of poles and ease spur penetration during climbing. This paper addresses the results of tests dealing with preservative retention and penetration, permanence of CCA and PEG, strength, drying rate, and checking characteristics.
W P Trumble, E E Messina


Inspection method of surface checking of Sugi posts
2003 - IRG/WP 03-20272
In order to establish the method for evaluating the checking of Sugi posts, checks on exposed posts were examined. Checks on Sugi posts exposed for 18 months were superficially inspected, that is, the length, width, and depth of the checks were measured from the outside with a ruler and 0.1 mm thick feeler gauge. Then, each post was cut into cross sections of the 30 mm width, and the check depth was measured accurately on each section. As visualizing check depths of a series of cross sections by graphic expression, the shapes of many checks were trapezoidal rather than triangular. The correlation between superficial inspection results and sectional inspection result were discussed, and it is considered that the gauge feeling is an accurate non-destructive method to measure the maximum of check depth, and the width and length can be applied to practical indexes to estimate the depth and inner area of check in Sugi posts.
H Kurisaki, H Nakatani, K Mizumoto


Report of the meeting of the refractory timbers sub-group, Lappeenranta, Finland on 25 May 1989
1989 - IRG/WP 3561
The first meeting of this sub-group took place on Thursday 25 May and considered the following agenda: 1) Papers presented to the meeting "Performance of treated spruce in Canadian field test sites" by J.P.Hösli and E.E.Doyle, IRG/WP/3506 and "Performance of CCA treated spruce and pine in unsterilized soil" by A.J.Nurmi. 2) Future work areas for the sub-group 3) Membership of the sub-group 4) Circulation of information
R J Murphy


The performance of glue laminated railway ties after 40 years of service in the main line track
1989 - IRG/WP 2325
Two series of horizontally glue laminated ties made of a softwood body and topped with a hardwood lamination were creosoted and installed in 1947 in a tangent and a curved main line track. The tests are now 40 years old and the excellent condition of the ties of these two series suggest that a service life of 50-60 years can be expected.
J P Hösli, E E Doyle, C P Bird, T Lee


Checking of sodium pentachlorophenate fixation in wood
1990 - IRG/WP 3620
In order to estimate the volatilization of sodium pentachlorophenate from treated wood, wood samples treated with pentachlorophenate were analysed after various durations of an EN 73 weathering The results giving no clear evidence of volatilization, treated wood samples were put in a test chamber with precise climatic conditions, the air used in the experiment being analysed. The pentachlorophenate content in air was quantified: 1.8 µg/m³
M Lamour, H Sageot


Glulaminated poles - Progress report after 7 years' testing
1987 - IRG/WP 3444
In 1979 a number of glulaminated poles with various preservative treatments were placed in a greenhouse at Uppsala, at the Simlångsdalen test field in southern Sweden and under a power line just south of the Arctic circle in order to study their resistance against biological degradation. The tests have shown that the comparatively best performance will be obtained if each lamination is treated with a water-borne preservative (only CCA was used in this test) whereafter the laminated pole is treated with creosote.
J Jermer, Ö Bergman


The suitability of high pressure sap-displacement for the retention of UK grown spruce and pine
1990 - IRG/WP 3595
The concentration and radial distribution of copper, chrome, arsenic (CCA), and the moisture content and depth of radial checking in UK grown, field exposed spruce and pine poles treated by high pressure sap-displacement are examined. The concentration of CCA elements in samples obtained from increment cores is similar in Norway spruce, Scots pine and Corsican pine but is significantly lower in Sitka spruce. The concentration of chromium in all species, arsenic in Sitka spruce, Norway spruce and Corsican pine and copper in Sitka spruce are at a maximum in the outer sapwood and decrease centripetally with increasing core depth. In contrast, arsenic in Scots pine and Norway spruce at groundline and copper in Norway spruce, Scots pine and Corsican pine are at a maximum in the inner sapwood. The slopes of metal concentration against radial core depth are similar in Norway spruce and Scots pine but are significantly larger (steeper) and smaller (less steep) respectively in Sitka spruce and Corsican pine. Checking is more severe in Sitka spruce than in the other species and appears to be associated with steep moisture gradients. In Sitka spruce, checks penetrate the preservative treated annulus thus greatly facilitating decay since micro-organisms have access to untreated non durable wood. The results suggest that high pressure sap-displacement is suitable for the treatment and long term protection of Norway spruce, Scots pine, and Corsican pine but is inadequate for the protection of Sitka spruce. Modifications to the high pressure sap-displacement process that could improve the treatment of Sitka spruce are discussed.
P D Evans, S D Hainey, A Bruce, G M Smith, B King


The natural durability assessments of secondary timber species - field trials
1998 - IRG/WP 98-10297
Secondary or 'alternative' hardwood timber species can replace traditional hardwoods and contribute significantly to satisfying the overall demand for hardwoods in the UK timber market. A selection of these 'alternative' hardwoods is currently being tested at BRE-WTC for natural durability both in ground contact (to EN252) at two field sites, and out of ground contact (as L-joints to EN330) at one site. The objective is to provide an assessment of the suitability of each species for future commercial application. Moisture movement has been monitored in the L-joint tenons showing in less durable timbers, such as rubberwood (Hevea brasiliensis), rapid in-depth wetting during rain. Other monitored features of timber failure in out-of-ground exposure, including surface mould, cracking, discoloration and rot, indicate to date clear species-based differences. Comparison of the test timbers, based upon responsiveness to moisture and degree of timber failure, classify calophyllum (Calophyllum spp.), Ghanaian teak (Tectona grandis) and niové (Staudtia stipitata) as most durable and least reactive to moisture. The results to date of the ground contact trials, when compared with archived durability data show that the archive records of ground contact natural durability remain valid, although some modern plantation-grown timbers, such as teak (Tectona grandis), appear less durable than material from virgin forest. The likely value and commercial application of some of the secondary hardwood timbers examined is summarised.
E D Suttie, R J Orsler


Structural defects in CCA treated timber fence posts: A case study.
1997 - IRG/WP 97-40084
Since 1983 an environmental improvement programme has been in progress in the city of Dundee. This programme included the erection of rail and pale timber fencing throughout the city. The timbers had been pressure treated with CCA prior to painting with 2 coats of an exterior wood stain finish. However, the larger dimension timber fence posts (100 x 125 x 1500 mm3) regularly developed severe checks/shakes in service. These defects raised questions regarding the continued use of timber as a fencing material by the municipal authoritiy due to concerns relating to the long term efficacy of preservative treatment and timber durability. Statistical models generated from visual and physical measurements of aged post timbers recovered from field sites in the city indicated that a reduction in the development of structural defects was associated with lower heartwood:sapwood ratios. The sites from which posts were recovered also influenced defect development indicating inconsistent timber quality specifications and/or pronounced variation in environmental conditions at each site. This paper highlights the problem of many municipal authorities who, through lack of available information, fail to implement specifications for treated timber components tailored to their specific requirements.
S Muhsin, D C R Sinclair, A Bruce, H J Staines


Kerfing reduces checking in ACA-treated western white spruce poles
1988 - IRG/WP 3477
Western white spruce poles, pressure treated with pentachlorophenol and ammoniacal copper arsenate (ACA) were installed in the Westham Island test site. The pentachlorophenol treated poles were unkerfed, while both unkerfed and kerfed ACA poles were placed in test. The checking and kerf width and depth were recorded at the time of installation. After ten years of weathering the checking characteristics of the poles was evaluated. The check depth and width in the kerfed poles was significantly less than that in the unkerfed material. The average depth of the deepest check in the kerfed poles was ca. 43 mm while that in the unkerfed ACA poles was 92 mm. Kerfing also reduced the degree of secondary checking in the poles.
J N R Ruddick


Comparative field performance of CCA and CCA-water repellent treated Southern pine lumber
1995 - IRG/WP 95-30089
This paper describes the field performance of end-matched southern pine boards treated with either CCA type C or CCA type C containing an emulsion water repellent (WR) additive. Boards were either kiln or air-dried after treatment, constructed into decks, and exposed for over 3 years at Harrisburg, NC. During this exposure, matched boards were monitored for internal moisture content, cupping at midpoint, checking, and degree of nail pull. The CCA-only treated boards display rapid changes in moisture content, check width, and degree of cupping that was directly influenced by rainfall. Although boards treated with CCA and the water repellent additive are starting to lose the characteristic of surface water beading, the boards continue to show greatly improved in-service dimensional stability compared with matched CCA-only treated boards. The effectiveness of the water repellent additive in reducing physical degrade during service exposure is manifested in greatly reduced check development and nail pull when compared to the CCA-only treated boards.
A R Zahora


Kerfing and center-boring reduce checking in CCA-treated slash pine posts
1997 - IRG/WP 97-40082
Single and double kerfing, center-boring and incising were applied to green, peeled, slash pine posts. Posts were air dried for ten weeks and assessed for the number of surface drying checks greater than 1.0 mm in width. Posts were then pressure treated with a chromated-copper-arsenate (CCA-C) preservative and exposed outdoors in a horizontal position. The number of surface weathering checks in the treated posts was assessed after six weeks and one years exterior exposure. The length, width, depth and volume of such checks was also quantified after 1 year. Single and double kerfing and center-boring were highly effective in reducing the number of checks after air drying and there were significant correlations between the green mass or growth ring eccentricity of posts and the number of drying checks that developed. Both kerfing and center-boring reduced the number of checks in treated posts after six weeks weathering and the size of checks after one years weathering. The kerfing treatments were the only ones which reduced the number of checks after one years weathering. Incising was ineffective in reducing checking after air drying or weathering and kiln drying of unmodified controls after CCA treatment also failed to reduce checking.
P D Evans, R Wingate-Hill, R B Cunningham


Development of software to automate the quantification of checking occurring in preservative treated wood exposed to weathering
2001 - IRG/WP 01-20228
Surface checking often disfigures the appearance of wood treated with water-borne preservatives and treatments designed to reduce such checking have been receiving increasing attention. Progress in this area has however been slowed by the lack of a method of rapidly and accurately quantifying checking at treated wood surfaces. A software package has therefore been developed which identifies, measures and records the dimensions and numbers of surface checks in scanned images of preservative treated wood specimens. The program uses grey-scale 600 dpi TIFF images of wood specimens and operates within the data acquisition, analysis and presentation software IgorPro (Wavemetrics). Procedures within the program analyse images sequentially pixel by pixel and one row at a time searching for brightness minima (dark areas) which satisfy criteria that are characteristic of checks. A black and white (b/w) image is then produced in which probable checks are shown black on a white background. Further procedures reduce noise in the b/w image eliminating artifacts (specks of dirt) and small checks that cannot be discerned by the naked eye. The final stage of the analysis rasters through the cleaned b/w image establishing which black pixels connect to each other and identifying and labeling checks and quantifying check positions, sizes and shape. These data are then presented in a spreadsheet. Using this package it has been possible to successfully quantify checking in a range of preservative treated wood specimens that have been subjected to natural weathering. This paper describes the principal features of the software package and presents preliminary data from analysis of treated and weathered specimens. The advantages of the system for quantifying checking in preservative treated wood as well as its limitations are discussed.
A G Christy, P D Evans


Surface characteristics of wood treated with various AAC, ACQ and CCA formulations after weathering
1991 - IRG/WP 2369
Wood samples treated with various alkylammonium compounds (AACs) as well as ammoniacal copper quat (ACQ) and chromated copper arsenate (CCA) have been studied in accelerated weathering experiments. Microscopic examination of the surfaces of these samples after exposure in a weatherometer revealed several different changes. Samples treated with didecyldimethyl ammonium chloride (DDAC) show considerable latewood defibration and severe earlywood erosion, while ACQ and CCA treated samples are far less prone to surface weathering than AAC treatments as well as the untreated controls. FTIR spectral data of surface material removed from these samples correlated well with the observed surface defibration. It appears that lignin components are most affected by the weathering process. The AAC counterion and chain length of dialkyl quaternaries in AAC treatments appear to influence the weathering effect.
L Jin, K J Archer, A F Preston


Surface checking of CCA-treated radiata pine decking timber exposed to natural weathering
2000 - IRG/WP 00-40165
A field trial was established at four locations in Australia to assess the effect of CCA and CCA-wax treatment on the checking (cracking) of radiata pine decking timber exposed to natural weathering. Untreated decking timber and timber that had been pressure treated with water acted as controls. After 1 year's exposure the number and sizes of checks occurring in treated timber and controls were assessed. Timber treated with CCA-wax had fewer checks, which were significantly smaller in size than those in CCA treated timber and the untreated controls (except for check length in untreated timber). Checking in CCA treated decking timber resembled that occurring in water treated controls in that checks tended to be larger (longer and wider) and fewer in number than those found in untreated (exposed) boards. This finding tends to suggest that the pressure treatment process may have influenced the susceptibility of wood to check during exterior exposure. The difference in check number and size between CCA treated and untreated controls was, however, statistically insignificant. The effect of the different treatments on checking was consistent across the four exposure sites. The implications of these findings for the development of preservative formulations that reduce the checking of wood during exterior exposure are discussed.
P D Evans, P J Beutel, C F Donnelly, R B Cunningham


Preliminary observations of the effect of growth ring orientation on the surface checking of flat sawn Southern pine decking
2005 - IRG/WP 05-20313
Checking in decking timber is a serious defect and methods of reducing its severity are required to ensure that wood can compete with alternative decking materials. The first aim of this research was to test the hypothesis that flat sawn Southern pine decking boards with growth rings oriented concave to the exposed surface will develop less severe checking when exposed outdoors than similarly exposed boards whose growth rings are oriented convex to the surface. A second aim was to examine the effects of wood type and three different types of fasteners on checking of boards. Five small decks were constructed each containing Southern pine decking boards with different growth ring orientations and manufactured from wood cut from close to the bark or nearer the centre of logs. Each decking board was fixed to the underlying sub-frame using 3 different types of fasteners, two of which were designed to permit flexural movement of the boards. The decks were exposed outdoors and after 6 months exposure the number and sizes of checks in the boards were assessed. Checks were significantly fewer in number and smaller in boards whose growth ring orientation was concave to the exposed upper surface than in boards whose growth rings were convex to the surface. There was no significant effect of wood type (inner or outer wood) and fastener type on the checking of boards. Orientation of flat sawn boards with growth rings concave to the exposed surface is a simple method of reducing checking of Southern pine decking boards. Further research is required to confirm these preliminary findings using preservative treated timber decking boards exposed for longer periods of time.
K Urban, P D Evans


Preliminary Observations of the Effect of Kerfing on the Surface Checking and Warping of Flat Sawn Southern Pine Decking
2007 - IRG/WP 07-20360
Checking and warping of decking timber are serious defects and methods of reducing their severity are required to ensure that wooden decking can compete with alternative decking materials. Kerfing is effective at reducing the checking and distortion of square cross-section lumber, and the checking of roundwood. In the past it has also been applied to preservative treated decking boards, however, there is no information on whether kerfing reduces the surface checking or warping of treated boards. In this study one, two or three kerfs were sawn to depths of 10, 13, or 20 mm into the underside of 140 mm (width) x 40 mm (thick) southern pine decking boards. Kerfed boards and matched unkerfed controls were exposed to natural weathering for 1 year and the surface checking and distortion of boards was measured. The aim was to determine whether sub-surface kerfing of decking boards could reduce the surface checking and distortion of boards, and the kerfing treatment (kerf number by depth) that was most effective at reducing both the checking and distortion of boards. Kerfing reduced the cupping of boards exposed to the weather, but had no significant effect on twist, or bow. Both the single and triple kerfs were effective at reducing the cupping, whereas the double kerfs were ineffective. There was a positive correlation between kerf depth and reduction in cupping, and the kerf sawn to a depth of 20 mm was particularly effective at reducing cupping. Kerfing had no statistically significant effect (p>0.05) on the surface checking of boards, although in most cases checking of boards containing kerfs was greater than that occurring in the unkerfed controls. Further research is needed to confirm these preliminary findings.
R Ratu, J Weizenegger, P Evans


The Effect of Solar Radiation on the Surface Checking of Wood
2007 - IRG/WP 07-40356
The aim of this research was to investigate whether exposure to solar radiation increases the checking of wood exposed to the weather, and examine the causes and spectral dependency of such an effect. Lodgepole pine samples were exposed outdoors under filters which transmitted selected regions of the solar spectrum while allowing other weathering factors to act on samples. Surface checking in samples was quantified after 12, 24 and 36 weeks, and the structural changes occurring at weathered wood surfaces were examined. Check numbers and dimensions were greater in samples exposed to the full solar spectrum than in samples exposed under filters that blocked the transmission of UV, visible or infra-red radiation. Samples that were shielded from more energetic wavelengths developed less checking. Checks developed in the rays and propagated at the interface between adjacent tracheids, close to the middle lamella. We conclude that exposure to UV and visible light increases the tendency of wood to check during exterior exposure. Our findings suggest that water-repellent treatments designed to prevent wood exposed outdoors from checking should contain additives that restrict the surface photodegradation of wood.
P Evans, K Urban


Development of a Weatherometer to Accelerate the Surface Checking of Wood
2008 - IRG/WP 08-20388
There is significant interest in developing preservatives that are better at preventing wood from checking. Currently, however, there is no accepted test methodology for accelerating the development of checks in wood samples so information on the effectiveness of treatments at restricting checking can be obtained more quickly. This paper describes the development of a new type of weatherometer (Accelerated Check Tester) and associated weathering cycles to accelerate the surface checking of wood. The device permits the testing of realistic-sized decking board samples that are oriented horizontally and restrained by fixings. It uses computer-controlled water spray and infra-red heating systems to expose samples over a 5 day period to wetting and drying cycles. Desiccated air is also blown across the surface of samples to further increase the effectiveness of the drying cycle. The Accelerated Check Tester operated continuously and trouble-free for 24 weeks during an experiment, which examined the effect of different weathering cycles on the checking of southern pine and western red cedar decking samples. Samples exposed in the Accelerated Check Tester developed large numbers of checks, some of which were quite big, particularly those in southern pine samples. Weathering cycles that increased the severity of drying by increasing drying time or temperature did not significantly increase checking. Similarly, the inclusion of a freezing step in the weathering cycle had little effect on checking. In contrast, samples subjected to a cycle that included exposure to ultraviolet light developed significantly more and larger checks than samples subjected to any of the other cycles. Checking was much more pronounced in southern pine samples than in western red cedar samples. The Accelerated Check Tester should be a very useful tool for obtaining information on factors that affect the checking of wood. Furthermore, it could also allow companies developing wood preservatives and associated water repellent additives to rapidly obtain information on the ability of treatments to restrict checking and so shorten the development time for new wood protection systems.
R Ratu, P D Evans


Finite Element Modelling of the Checking of Wood Exposed to Accelerated Weathering
2010 - IRG/WP 10-20459
The surface checking that develops when wood is exposed to the weather reduces the visual appeal of treated wood products and can reduce the effectiveness of preservative treatments. There is strong interest in developing solutions to this problem and also a growing realization that such solutions may evolve from a deeper understanding of the mechanisms responsible for surface checking. In this paper we describe a two-dimensional finite element model that couples moisture diffusion, dimensional change and the development of strains in wooden decking boards exposed to accelerated weathering. The model successfully predicts the strains that cause checks to form in decking boards exposed to accelerated weathering. High tension strains develop at the surface of boards, as expected, but we also observe high strains in the rays and in the core of boards. Such strains explain how checks propagate radially and why internal checks can develop in decking boards. These internal checks may create large cracks when they coalesce with surface checks. In summary, the model we have developed has provided useful insights into the mechanisms responsible for the checking of wood. Further development of the model could provide additional insights and allow it to be used as a tool to optimize the weathering cycles of devices designed to accelerate the checking of wood, or to virtually screen chemical or physical treatments designed to reduce the checking of wooden decking boards.
S G Ribarits, P D Evans


The Effectiveness of Machined Profiles at Reducing the Checking of Wooden Decking
2011 - IRG/WP 11-40541
This study tests the hypothesis that ‘the ability of surface profiling to reduce checking of deck boards exposed to weathering will vary with wood species and profile type’. Southern pine (Pinus sp.) and Pacific silver fir (Abies amabilis) deck boards were machined to produce three different types of surface profiles: flat (control), ribbed (V-shaped grooves), and rippled (U-shaped grooves). Boards were exposed to accelerated weathering for 5 days, and the number and sizes of checks that developed in boards were quantified. Surface profiling reduced the total number and total width of checks in both Pacific silver fir and southern pine deck board specimens, but it had a greater effect at reducing checking in Pacific silver fir than in southern pine. The ribbed profile, in particular, was much more effective at reducing checking of Pacific silver fir than it was at reducing the checking of southern pine. Therefore, we conclude that the effectiveness of surface profiling at reducing checking of deck boards depends on wood species and the type of profile machined into wood surfaces. Checks developed in the grooves between the ribs of profiled boards and appeared to be constrained from becoming wider to a greater extent than becoming longer. Therefore, we conclude that the beneficial effect of profiling on the appearance of boards arises because checks are much narrower than those on flat boards and are located in the grooves, where they are difficult to see.
P Evans, I Cullis, P Morris


Use of Variable Pressure Scanning Electron Microscopy for in situ Observation of Degradation of Wood Surfaces during Artificial Weathering
2012 - IRG/WP 12-20489
Variable pressure scanning electron microscopy (VPSEM) is capable of observing electrically non-conductive materials like wood without the need to render the surface conductive by applying a coating of gold, platinum or carbon. Hence, there is the possibility that VPSEM could be used to non-destructively follow the structural changes occurring at wood surfaces during weathering, because specimens can be observed initially (before weathering), and then re-examined after exposure to the weather. This study uses VPSEM to examine the time-dependent micro-structural changes occurring at untreated and treated wood surfaces exposed to artificial weathering. Cryptomeria japonica (sugi) sapwood was treated by grafting a UV absorber (UVA) to the wood. We compared the micro-checking of bordered and half-bordered pits at treated (grafted) and untreated wood surfaces exposed to weathering. We hypothesised that the grafting treatment would restrict micro-checking of pits. VPSEM revealed significant micro-checking of pits at untreated surfaces exposed to artificial weathering for only 30 h. The dimensions of pit micro-checks increased when untreated samples were exposed to weathering for an additional 30 h. Pit micro-checking occurred more slowly in sugi sapwood treated with a UV absorber. We conclude that pit micro-checking at wood surfaces exposed to artificial weathering is restricted by grafting a UVA to the wood. We further conclude that VPSEM is a valuable tool to follow the time-dependent micro-structural changes occurring at wood surfaces exposed to weathering.
F Hatae, Y Kataoka, M Kiguchi, H Matsunaga, J Matsumura


Study of weathering Characteristics in Profiled and Treated Deck Boards
2014 - IRG/WP 14-40680
Wood exposed outdoors to repeated wetting and drying develops surface checks. Excessive checking of wooden deck boards has been a major source of dissatisfaction to consumers. In this study, Southern pine (Pinus sp.) deck boards were machined to flat (control) and ribbed surface profiles. The specimens were treated with aqueous formulations of 4,5-dichloro-2-N-octyl-4-isothiazolin-3-one (EL2) and amine copper azole (CA-C) using a vacuum/pressure method. Boards were exposed to accelerated weathering for 576 h (24 days). The number, length and width of checks that developed in boards and average amount of cupping, twist and bowing in each test board were quantified after weathering. The results of statistical analysis showed all of the preservative-treated ribbed decking samples had a lower average number of checks compared to end matched flat samples. Checks were also shorter and narrower in the profiled deck boards than in the unprofiled specimens. Furthermore, the lowest amount of checking, cupping, twist and bowing was observed for specimens profiled and treated with the EL2.
M Akhtari, D Nicholas, L Sites


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