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The effect of extent and location of decay on strength loss in constructional timber
1994 - IRG/WP 94-30039
Radiata pine heartwood billets, 50 x 100 x 1000 mm³ were end-sealed and treated with copper-chrome-arsenate preservative (NZ Type I) to a range of retentions and penetration patterns. Cross-sections, 10 mm thick, were cut from the centre of each billet and used for determination of preservative distribution, for preservative analysis and for decay tests. The decay test consisted of laying samples on the surface of soil beds in the FRI Fungus Cellar to induce decay of untreated and sub-threshold treated regions of samples. Location and extent of decayed areas in each sample were measured and their effect on residual strength properties were calculated using a computer programme orginally developed to determine the effect of cross-sectional defects on strength properties of laminated beams. Results showed that depending on the location of the decayed area, up to 14% of the cross-section could be lost through decay without significant loss of strength and over 30% could be lost while retaining 80% residual strength and stiffness. Relationships were also established between extent of decay, preservative retention and preservative distribution to demonstrate that compliance with local timber treatment specifications did not necessarily guarantee the timber's immunity from decay.
M E Hedley, H Bier

Scientific development for prolonging the service life of timbers by impregnating with creosote or organic solvent type preservatives in which additive has been incorporated
1977 - IRG/WP 382
Chemically impregnated wood has played a prominent part in the Telephone and Electricity Distribution Industry during the past century and there is no doubt that it will play an equally prominent part in the future. The reasons why wood poles and wooden, structures predominate, are that when adequately chemically impregnated with a recognised timber preservative to ensure the expected service life for the purpose envisaged, the timber is then fully protected against the ravages of wood destructive organisms. Furthermore, wood is endowed with many natural characteristics that make it a favourite pole and structural material. Its high strength, light weight, ability to absorb impact or shock from loads suddenly applied and ability to resist overloading for brief periods plus its well-known insulating qualities - all are important basic reasons for its predominance in pole line structure. The use of chemically impregnated timber often makes it possible to carry out a given construction programme at less cost, or to erect more structures for a given sum of money, than when more expensive construction materials are employed.
P R B D De Bruin

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

Depletion of wood preservatives after four years' marine exposure in Mt. Maunganui harbour, NZ
1994 - IRG/WP 94-50036
This paper reports on chemical analysis of marine test samples exposed in Mt. Maunganui harbour, New Zealand from 1977 to 1981. Depletion data for a Class II CCA, a CCA-A formulation, acid copper chromate and ammoniacal copper arsenate are presented. The results suggest differences in the rate of loss of individual preservative components among the four formulations and redistribution of individual preservative components within the wood.
K J Archer, A F Preston, C M Chittenden, D R Page

Comparison of the effect of different soil sources on the type and rate of decay of CCA-treated pine exposed in a soil-bed
1984 - IRG/WP 2213
The types of decay observed in CCA-treated pine posts in horticultural situations in New Zealand can be reproduced using a soil-bed exposure. Radiata pine stakelets, untreated or treated to 1.4, 2.7, or 5.4 kg/m³ with Tanalith NCA, were exposed to six different soil sources. The local nursery soil used for all standard laboratory tests was found to represent the greatest decay hazard to untreated pine. Poverty Bay horticultural soils were more hazardous than the local field test site soil to CCA-treated pine. Soil collected from adjacent to a 'decaying' post could decay treated wood faster than soil collected from around a 'sound' post. Brownrot, softrot, and bacterial degrade was observed. All failures of untreated pine and early failures of CCA-treated pine were caused by brownrot.
J A Drysdale

The performance of water repellants on radiata pine exposed to the weather
1989 - IRG/WP 3553
The effectiveness and resistance to weathering of four water repellent treatments, a commercial timber stain, and an oil-based clear finish, was assessed using 20x20x6 mm³ samples of untreated, copper-chrome-arsenic (CCA)-treated, and tributyltin oxide (TBTO)-treated radiata pine exposed to the weather over a four month period. The water repellency of each preservative/water repellent combination was measured by retrieving samples from an exposure rack on a monthly basis and recording weight increase on water immersion. The results were analysed with regard to the water repellency of each water repellent/preservative combination as a function of time. Significant increases in water absorption were noticed in most sample sets three to four months after initial exposure. The relative effectiveness of the different water repellent treatments varied according to the nature of any preservative treatment of the samples.
D V Plackett, F M Cameron

Soft rot decay of Eucalyptus maculata Hook. in different soils from Queensland, Australia
1980 - IRG/WP 1113
In the present work, different Queensland soils were chosen and their gross effects on the decay of treated and untreated Eucalyptus maculata examined. The soils were also amended with various levels of phosphate to study the response of the wood decay mycota to an increasing supply of this nutrient. Phosphate amendment was chosen because of the wide-scale use of superphosphate on Queensland soils and the importance of inorganic phosphate in the carbohydrate metabolism of microorganisms.
L E Leightley, I W Russell

A comparative study of CCA type C and B treated poles in service
1993 - IRG/WP 93-50001-05
CCA K33 type B and C treated utility poles, 9 pieces of each treatment type, were analyzed for preservative retention after 11 years in use. Borings were taking 1 m above and 0.3 m below the ground line. Also total amount of copper, chromium and arsenic was determined in soil surrounding the poles. The solubility of these active components in soil was monitored by using different leaching procedures. Remarkable losses of Cu, Cr and As were found in both type of poles, particulary As from type B poles. Exact figures could not be given because of missing original preservation data. In comparison to the natural background high As and Cu contents were found in soil. CCA type B poles emitted As up to 760 mg/kg (oven dried soil) which is least 760 times higher than the natural background (0.4-1.0 mg/kg). The average value of As emitted by C type poles was 92 mg/kg. The amount of copper varied from 10 to 50 fold to the background but no essential differenceswere noticed among the two groups. Type C poles emitted more Cr but the average figures were lower than that with As and Cu. The solubility of As, Cu and Cr, as a very important factor, was investigated by preparing series of leaching tests. Only slight differences were found between EPA (US Environmental Protection Agency) and water leaching tests. In both leaching tests As was the most soluble element and 1.2-1.1 mg/l of As in the soil connected to B type poles was in soluble form. The figures were much lower with the case of C type poles and were 0.16-0.26 g/l respectively. Additional tests also proved that lower pH values decreased the solubilily of As. The effect was even stronger with adding ferrous sulphate. On the contrary increases pH resulted higher solubility.
A J Nurmi

The possible significance of the lignin content and lignin type on the performance of CCA-treated timber in ground contact
1988 - IRG/WP 1357
The lignin in wood samples of Alstonia scholaris, Octomeles sumatrana and a Simaruba species have been analysed. These timbers are characterised by a high lignin content and low syringyl:guaiacyl ratios. Decay tests with two soft rot fungi showed that the timbers were less susceptible than timbers with a low lignin content and higher syringyl:guaiacyl ratios. Numerous data for field performance of Alstonia and limited information on treated Octomeles and Simaruba suggest that timbers with a high lignin content and low syringyl:guaiacyl ratios will perform well in ground contact when treated with CCA.
T Nilsson, J R Obst, G F Daniel

A study of decay type variability in variously treated Fagus sylvatica and Pinus radiata field test stakes exposed at a vineyard for 30 - 45 months
1998 - IRG/WP 98-10271
Pinus radiata test stakes were treated with 10 kg/m3 of CCA plus 4 lower retentions in a geometric series of 1.5. Fagus sylvatica was treated with 15 kg/m3 and 2 lower retentions. Both timber species were also treated with equivalent retentions of various new generation preservatives (P. radiata was also treated with creosote). Whilst these stakes were exposed at 11 sites in New Zealand (NZ) and 2 in Queensland Australia, this paper reports only data from a single NZ site where preservative and timber species effects on decay type were particularly pronounced. Of particular interest was the finding that copper-azole and copper-quat. treated pine was less susceptible to soft rot attack but more susceptible to attack from tunnelling bacteria, compared to CCA treated wood. Beech was not attacked by tunnelling bacteria but was attacked by an unusual type of fungal cavitation/erosion. These, and other preservative and timber species effects on decay type are discussed.
R N Wakeling, A P Singh

A study of the decay type potential of seven soils
1992 - IRG/WP 92-1539
The aim of this experiment was to determine the significance of the fungal inoculum potential and physico-chemical properties of five field trial test site soils, a garden compost known to cause white rot in copper treated fence palings, and soil from a zone between 2 and 15 centimetres from a CCA treated post with brown rot, in causing differential decay type in Pinus radiata and Poplus deltoides sapwood blocks. Two blocks of each species were buried in non-sterile soil in jars with the upper transverse face level with the soil surface. A block of the same species was placed, with the transverse face upwards, on the top of each buried block. Six replicate jars per soil type were used. A second set of jars containing 90% sterile potting compost and 10% non-sterile soil, for each of the seven types, was set up as described above. Soil moisture content was adjusted to, and maintained at, 30% of the dry weight. Decay type and weight loss was determined for each block after twenty weeks incubation at 25°C. Considerable differences of decay type and weight loss edited between the 100% and 10% soil regimes, soil type, and timber species. These differences and their significance are discussed.
R N Wakeling

Applications of the shower test. Part A: Results from CCA type C treated wood: influence of fixation process
1993 - IRG/WP 93-50009
This report outlines the results of shower tests conducted on CCA type C treated wood. The results indicate the inherent good fixation of CCA type C, as judged by the leaching limits within the Environmental Regulations. The shower test has proven to be a useful quality control and research test. It determines reasonably accurately the leaching under simulated conditions and, admittedly from a limited number of tests, it can determine differences between various fixation cycles. Natural fixation, controlled climate room fixation and steam fixation were compared. Overall the steam fixation process gave the lowest leaching figures although the selection of an appropriate fixation facility is a question for individual companies, taking into account capital, customer base, throughput etc.
W J Homan, H Militz, D A Lewis

Effect of test site, preservative and wood species on decay type Glenbervie pastoral and radiata pine forest sites
2000 - IRG/WP 00-30248
Pinus radiata stakes were treated with 0.8, 1.2, 1.8, 2.7 and 4.1 kg/m3 of CCA and Fagus sylvatica with 2.7, 4.1 and 6.1 kg/m3 of CCA. Both wood species were also treated with equivalent retentions of a copper plus triazole preservative (CT) (0.89, 1.3, 2 and 3 kg/m3 of copper for pine & 2.5 and 4 for beech) and chlorothalonil plus chlorpyriphos in oil (CC) (1.4, 2.1, 3.2 and 4.8 kg/m3 of chlorothalonil for pine and 3.2 and 7.2 for beech). Furthermore, P. radiata was treated with ammoniacal copper plus a quaternary ammmonium compound (ACQ) (0.8, 1.1, 1.7 and 2.6 kg/m3 copper) and a 60/40 mixture of high temperature creosote plus oil (C) (18, 27, 41 and 61 kg/m3). Treated and untreated stakes were exposed in the ground at 13 sites in New Zealand and Australia for between 4 and 6 years. This paper reports the significance of site, timber species, preservative and its concentration and time of exposure, on extent and type of decay, at two sites in Northland, New Zealand. The two sites were adjacent (200 metres), appeared to have essentially similar clay loam soil and climate but one was pastoral and the other was situated within a radiata pine forest. Most types of decay reported in the literature, were observed in this study but other undescribed or only partially characterised types were also found. The decay types found differed between test sites, preservative and timber species. The significance of tunnelling hyphae, which often caused severe decay of wood treated with the higher retentions of various preservatives, appears much greater than the prior literature would suggest. For pine the highest retentions of CC, CT and ACQ gave at least equivalent performance to the reference standards creosote and CCA, after approximately 5 years, at both test sites. For beech CC and CT both gave superior protection to CCA, at both sites. All the preservatives tested exhibited some weaknesses in terms of resistance to the various decay types observed.
R N Wakeling

Laboratory studies of CCA-C-leaching: influence of wood and soil properties on extent of arsenic and copper depletion
2002 - IRG/WP 02-50186
The extent which a wood preservative leaches is important for efficacy studies and environmental concerns. However, little information exists on the effect soil properties have on leaching. This study investigated leaching of stakelets which had been cut from five different southern yellow pine (SYP) sapwood boards then treated with CCA-C to a target retention of 6.4 kgm-3 (0.4 pcf). All stakelets were leached for 12 weeks by a common laboratory method in five different soils or water, with five replicate stakelets per board/soil. The physical and chemical properties of the five different soils were determined and the average leaching of the individual components of CCA was correlated with the various soil properties. Unfortunately, migration of a soil component (likely iron) into the stakelets from at least one of the five soils interfered with Cr determination by X-ray fluorescence; consequently, Cr depletion was not studied. Stakelets cut from one board tended to have lower Cu and As losses than the average of the other four boards for all five soils and water, and stakelets from another board tended to have higher Cu losses. Stakelets from all five boards had similar initial Cu and As levels, suggesting that the board effect was not due to differences in initial retentions. Cu loss was approximately equal to or greater than As loss for stakelets exposed to all five soils, but for wood leached in water the As loss was about twice the Cu loss. The soil property which was most statistically correlated to Cu loss was % Base Saturation (r2 of 77%), with Soil Acidity (pH) also important as a single predictor, and the Cr and Cu Soil Contents important as secondary predictors. The relationship between % Base Saturation (or Soil Acidity) and % Cu leached was not linear, however. A negative correlation was observed between Soil Cu Content and the metal leached from wood. The best factor to predict As loss was the Soil Cu Content, with Exchangeable K and % Silt also contributing to give an overall r2 of 72.3%. The % Organic Matter and the Soil As Content were also important as secondary predictors. We conclude that depletion of CCA is extremely complex and that Cu and As depletion appears to be influenced differently by the soil properties. Furthermore, extent of leaching can vary between different wood samples of the same species and even samples cut from the same board; thus, leaching data are not precise. Recommendations are given for a standard laboratory method for ground-contact leaching.
D Crawford, R F Fox, D P Kamden, S T Lebow, D D Nicholas, D Pettry, T Schultz, L Sites, R J Ziobro

Evaluation of the efficiency of industrial kiln type CCA fixation chambers
1996 - IRG/WP 96-40063
Six commercial CCA treating plants in Canada were assessed for the fixation efficiency of their hot air fixation chambers. The wood temperature was measured with thermocouples over the fixation period at different locations in the chamber and at the end of the fixation cycle, the degree of chromium fixation was determined by a boring leaching procedure. There was a great variation in the effectiveness of the chambers, related to the heat transfer efficiency of the kilns. Both an adequate steam supply and efficient air circulation are essential to ensure quality fixation in a reasonable time frame. In plants without this, the wood deep in the lumber piles is still in a mainly unfixed state when removed from the fixation chamber. In contrast, for CCA treated wood allowed to fix under ambient temperature conditions, the interior of bulk piled lumber fixes faster than the outer wood or stickered wood. This results from the cooling effect of water evaporation from the exposed lumber as it dries.
A Taylor, P A Cooper

The relationship between preservative type and surface degrade in Pinus radiata
1980 - IRG/WP 3158
Samples of Pinus radiata D. Don were impregnated with one of two preservative types, a copper chrome arsenic salt and a light organic solvent preservative. The panels were exposed to the weather for 4-5 years at a site near Sydney, Australia. Macroscopic and microscopic examinations showed different rates and patterns of weathering between the samples treated with each preservative and an untreated control. The sample treated with copper chrome arsenic salt indicated reduced lignin and cellulose degradation when compared to the untreated wood and the lignin and cellulose breakdown was greatest in the wood impregnated with light organic solvent preservative. Adsorption of copper and chromium onto lignin and cellulose appears to have stabilised the wood treated with copper chrome arsenic salt and the organic solvent preservative appears to have solubilised the lignin and facilitated weathering.
R S Johnstone, R K Bamber

CCA type C depletion of Southern yellow pine utility poles
1995 - IRG/WP 95-50049
Depletion and redistribution of preservative components were evaluated on five CCA-C treated poles in service for over six years in Conley, Georgia. A statistical approach was taken in which retentions below ground were compared to retentions above ground due to a lack of initial data on individual poles. It was hypothesized that the below ground retentions should be lower than the corresponding above ground retentions based on the premiss that wood in ground contact is subject to a higher leach potential than wood above ground contact. There were no significant differences between above ground and below ground CCA-C retentions in any of the six 12.5 mm zones. Linear regression performed on the retentions across zones showed no significant difference between the slopes of the gradient curves on either exposure for any of the components indicating there has been no redistribution of chemicals among zones.
P D Osborne, R F Fox

Is Field Test Data from 20 x 20mm Stakes Reliable? Effects of Decay Hazard, Decay Type and Preservative Depletion Hazard
2006 - IRG/WP 06-20327
Effects of decay hazard, decay type and preservative depletion hazard on the performance of variously preservative treated 20 x 20 x 500 mm Radiata pine and Fagus sylvatica test stakes across 13 field test sites in New Zealand and Queensland Australia were determined. Radiata pine treated with an ammoniacal copper quaternary preservative (ACQ) (1.56% m/m a.i.) and copper chrome arsenate (CCA) (0.72% m/m a.i.) was susceptible to sudden failure at some of the sites that had a high brown rot hazard whereas pine treated with copper-azole (CuAz) (0.59% m/m a.i.) was not affected, suggesting that CuAz was particularly effective against brown rots. At the most severe brown rot sites ACQ treated pine was more susceptible than CCA and its performance in service may be compromised as a result, as previously occurred for pine treated with acid copper chromate (ACC). Based on overall performance across all sites pine treated with chlorothalonil plus chlorpyriphos (1.07% m/m a.i.) (11% mean soundness reduction (MSR)), creosote/oil treated pine (37% m/m a.i.) (14% MSR) and CuAz (15%MSR) all gave significantly better protection (5% P) than pine treated with CCA (19% MSR) and ACQ (19% MSR). The decay hazards encountered, as determined by mean soundness reduction after 6.5 years, were more severe than encountered in previous studies at some of the same sites and this was linked to differences of intra-site decay type between test plots and associated decay hazard differences. Greater decay rates encountered in this study were, in part attributed to high preservative depletion. At very wet sites, particularly those likely to have a high soil organic acid content, 20 x 20 x 500 mm stakes are probably too small for accurate interpretation of long-term durability of preservative treated wood. Knowledge of the distribution of different decay types across sites tested, coupled with associated decay hazards and preservative depletion hazard, suggested that 4 test sites of clearly defined features would enable comprehensive field testing of preservative treated wood. Selection of sites is not straightforward and requires a rudimentary knowledge of soil type, geology, vegetation and climate, or comprehensive knowledge of the decay types present. In view of the cost of maintaining test facilities, adequate multi-site testing of new wood preservatives may be achievable through cooperation between research establishments. Possibly, current test site selection criteria fall short of ensuring adequate test site parameters are incorporated and maximum cost effectiveness of testing may not always be achieved through duplication of test site parameters between sites of similar but unrecognised properties. Scope for artificial creation of intra-site decay hazard differences is discussed.
R Wakeling

A comparison of soft rot, white rot and brown rot in CCA, CCP, CCF, CCB, TCMTB and benzalkonium chloride treated Pinus radiata IUFRO stakes, after 9-15 years exposure at five test sites in New Zealand
1991 - IRG/WP 1485
The aim of this study was to determine if decay type varies significantly between five field trial test sites of different soil type, aspect and climate in 9-15 year old, replicate CCA, CCF, CCP. CCB, TCMTB and AAC treated IUFRO stakes. A visual on-site assessment of decay type on every test stake was made and observations confirmed by microscopical examination. Regression analyses were used to determine significant differences of percentage frequency of occurrence of each rot type between sites and preservatives. Large differences in percentage frequency of occurrence of rot type were evident between sites. One site was dominated by brown rot (85%) and two were dominated by soft rot (99 and 91%). The fourth site had intermediate proportions of brown rot (40%) and soft rot (71%) but had the second highest occurrence of white rot (32%) (highest = 37%; lowest = 11%). The fifth site was distinct in that a large proportion of stakes (69%) had both well established brown rot and soft rot. Stakes at the other four sites tended to have only one rot type. Some highly significant preservative effects were also found. Possible causes of these differences are discussed in terms of inter-site soil type, climate and other differences.
R N Wakeling

IRG/COIPM INTERNATIONAL MARINE TEST - to determine the effect of timber substrate on the effectiveness of water-borne salt preservatives in sea-water. Progress Report 2: Report of treatment and installation in Australia
1978 - IRG/WP 440
The purpose of this test and the procedures to be followed have been fully set out in documents distributed by the International Research Group on Wood Preservation and numbered IRG/WP/414 and IRG/WP/420. The prescriptions set out in these two documents have been closely followed.
J Beesley

Marine testing of selected waterborne preservatives
1987 - IRG/WP 4137
In 1978 a marine test was established at West Vancouver, B C. to determine the performance of selected waterborne preservatives. The preservatives in test were chromated-copper-arsenate (CCA-C), ammoniacal copper arsenate (ACA), a modified formulation of ACA which contained a higher copper content (modified ACA), ammoniacal copper zinc arsenate (ACZA) and ammoniacal zinc arsenate (AZA). The wood species used for the test was red pine. After eight years in test the CCA is providing excellent performance at all retentions, while the modified ACA is showing significant deterioration only at the lowest level. The ACA is performing quite well although it shows signs of surface deterioration at all retention levels. The performance of the ACZA is rated as unsatisfactory at retentions below 32 kg/m³ while AZA was considered to be unsuitable for use in the marine environment.
J N R Ruddick

Manual of a mini treating plant for waterborne preservative treatment of timber and bamboo
1999 - IRG/WP 99-40130
This contributional article includes machinaries and equipments necessary for a small wood treating plant for the pressure treatment of tim bers with waterborne preservatives along with the cost and design. The preservative treatment limitations, treatment schedules and specifications for different products have been described. The cost of a mini treating plant will be 6,00,000 Tk. (13,000 US$), suitable for preserving timber and bamboo products for indoor and outdoor uses and will out last teak wood. The additional durability of timber and bamboo will create economically and environmentally safe conditions.
A K Lahiry

Fire resistance of preservative treated fence posts
1994 - IRG/WP 94-30033
Pine fence posts were pressure treated separately with CCA-C, CCA-wax, CCA-oil and creosote. Treated posts and untreated controls were planted in the ground in a randomised block design, weathered for six months and then subjected to a controlled burning test using two fuel loads. Creosote treatment increased the time that posts were alight whereas CCA treatment had no such effect. However, CCA treated posts smouldered until destruction of the majority of the posts occurred. Posts treated with CCA-oil took longer for destruction to occur than posts treated with CCA-C or CCA-wax. Creosote treated posts and untreated controls did not show prolonged smouldering and consequently were not destroyed by the burning test, although their strength was reduced. A high fuel load increased the time that posts were alight and smouldering, and for CCA treated posts decreased their time to destruction.
P D Evans, P J Beutel, C F Donnelly, R B Cunningham

Strength loss associated with steam conditioning and boron treatment of radiata pine framing
1987 - IRG/WP 3438
The combined effect of included defects and wood moisture content on the strength loss of second rotation radiata pine framing following conventional steam conditioning is investigated. The green Modulus of Elasticity (MOE) is reduced by approximately 13% after steaming. When dried after steaming, however, neither the MOE nor MOR is significantly different from unsteamed dried controls.
M J Collins, P Vinden

Collaborative soft rot tests: PRL tests of Cu/Cr/As preservative using method of Document No: IRG/WP/208
1973 - IRG/WP 223
These tests were undertaken as a preliminary to the next series of collaborative soft rot tests. An interim report has already been presented at Berlin in 1972 as Document No: IRG/WP/211
J K Carey, J G Savory

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