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A new model for wetting and drying of wood end-grain – with implications for durability and service-life
2011 - IRG/WP 11-20477
New experimental data for wetting and drying of wood end-grain, Sandberg (2009), imply that traditional models for moisture transport are not at all applicable. A new model is developed to consider the phenomenological behaviour of water transport in and out of end-grain, using the pore water pressure and sorption scanning properties. Modelling results are compared to experimental results and the consequences for durability are discussed.
L-O Nilsson, K Sandberg

Butt-end incising to improve penetration and retention of creosote in Eucalyptus saligna power transmission poles in Kenya. Preliminary results
2002 - IRG/WP 02-40249
Incising as a possible technique to improve penetration and retention of creosote in the butt end of Eucalyptus saligna power transmission poles in Kenya was investigated. Debarked, butt-end samples from whole poles were seasoned (15% MC), incised using four patterns of incisions, sealed at the top or small diameter end, and pressure treated with a mixture of creosote-furnace oil (60/40 mix) at a commercial plant using a full cell process. They were then conditioned in the open for 3 months to allow evaporation, migration, and bleeding. The samples were subsequently leached in running tap water for 21 days, air-dried for 8 weeks under cover and retentions calculated on a weight-gain basis and compared. Discs were removed from the middle (450mm) of the samples, and radial penetration assessed visually and measured. Compared to un-incised samples, both penetration and retention were substantially improved in samples with closer incisions of 20 mm x 20 mm, by 58.6% or 89.8 mm and 87.0% or 146.4 Kg/m3 respectively. Wider incisions 0f 40 mm x 40 mm achieved lower improvements, 17.3% or 66.4 mm for penetration and 19.8% or 93.8 Kg/M3 for retention. The 4 incising patterns achieved consistently higher penetration and retention of creosote compared to un-incised control samples, which achieved lower average penetrations (56.6mm) and retentions (78.3Kg/M3). Butt-end, or incising the ground-contact sections of transmission poles may be a feasible technique for improving both penetration and retention in the more vulnerable portions of poles, and thus substantially increase service lives of eucalyptus poles in the country. Further investigations are necessary to establish patterns of incision and appropriate treatment schedules.
R Venkatasamy

Butt-end incising to improve penetration and retention of CCA in Eucalyptus saligna telegraph poles in Kenya: Preliminary results
2002 - IRG/WP 02-40243
Incising to improve penetration and retention of Copper Chrome Arsenate (CCA) in the butt end of Eucalyptus saligna telegraph poles was investigated. Debarked, seasoned (15% MC) butt-end samples from full size telegraph poles were incised using four patterns of incisions, sealed at the top or small diameter end, and pressure treated, together with un-incised samples, with CCA-C (3.0% oxide type) at a commercial pole treatment plant, using a full cell process. After conditioning under cover for 6 weeks to allow fixation and air-drying to 15% MC, samples were leached in running tap water for 12 days, re-dried to 15% MC, retentions calculated on a weight gain basis and compared. Discs were removed from the middle 50mm sections of samples, sprayed with Chrome-azurol S, and average radial penetration computed. In comparison to un-incised samples, both penetration and retention were substantially improved in samples with closer incisions of 20 mm x 20 mm, by 59.9 %, or 79.3 mm and 59.0%, or 28.3 Kg/m3 respectively. For the wider incisions of 40 mm x 40 mm, improvements were lower, 13.1%, or 56.1 mm for penetration and 19.7%, or 21.3 Kg/m3 for retention. Un-incised samples achieved consistently lower average penetrations of 49.6 mm and retentions of 17.8 Kg/M3. Butt-end incising maybe a feasible technique for improving the otherwise unacceptable short service lives of eucalyptus telegraph poles in the country. Intensity, depth, and method of incising, together with appropriate treatment schedules, need to be investigated further.
R Venkatasamy

Long service life or cascading? The environmental impact of maintenance of wood-based materials for building envelope and their recycling options
2018 - IRG/WP 18-50336
A major restraint in choosing bio-based materials (i.e. wood-based) for external use, is the lack of confidence that architects, designers and customers have toward these materials. In particular, the limit state of bio-based materials, which defines the frequency of maintenance operations, might be reached earlier for wood than for other materials (i.e. concrete). On the other hand, resource and energy scarcity together with increasing concern for climate change consequences are raising the demand for competitive bio-based materials in the built environment as substitutes for other energy-intensive materials. Therefore, novel and traditional protective treatments are used to improve the performance of woody materials for outdoor use. Nonetheless, the environmental and economic burden of such treatments is often unknown. The number of LCA (life cycle assessment) studies on the topic is low, with geographically sparse data and non-uniform assessment protocols. This study provides a novel approach to assess the in-service performance, maintenance requirements and end-of-service-life options for over one hundred bio-based materials for façades. The protection techniques of the materials under examination include: chemical modification, thermal treatment, impregnation, hybrid treatments, and surface treatments (bio-film, coating and nanocoating). Natural, untreated wood and composite materials such as wood-plastic composites are included as well. The in-service environmental performance is analysed by considering the amount of material, energy, water and waste that are used and/or produced to maintain one square meter of façade. The options for end-of-service-life include: panel manufacturing, pelletizing, animal bedding, liquefaction, insect conversion, fungal conversion, combustion, incineration, gasification and pyrolysis, anaerobic digestion, fermentation, composting and landfilling. For each material group, the possibility for cascading use is assessed. The overall goal is to increase the confidence in bio-based building materials by tackling environmental issues related to wood modification processes.
M Petrillo, J Sandak, P Grossi, A Kutnar, A

How to Document the Performance of Super-Critical Treated Wood in above Ground Situations?
2005 - IRG/WP 05-20316
The paper presents practical experiences from the preparation of a new preservative treated wood product for introduction to the market. The product in question is Superwood™, which is treated with organic biocides using CO2 in a supercritical state as a solvent. The question is how to evaluate the performance of a new product such as Superwood™ in order to get an acceptance on the market and fulfil the formal requirements. In the European Union countries, the EN 599-1 is the standard that needs to be complied when approving a new product for the market, but it only focuses on the toxic limit against representative decay fungi according to EN 113. However, decay test, above ground and other forms of field tests are optional, this is not in line with the traditional test philosophy in the Scandinavian countries. The open question is to which extent treatment to the level of the toxic threshold value also ensures a long service life and expected performance of the treated commodity. Superwood™ is evaluated using a strategy, in which basic laboratory tests are done to get the toxic value (according to EN 599-1) and in addition a number of field tests are done including accelerated testing in the tropics. These tests are focussed on the evaluation of the performance criteria such as durability and service life and maintenance requirements. These questions must be answered by the producer without having a full record of performance test for their new products. A short status on the test performed on super-critical treated wood (Superwood™) is presented. Based on a comparison between field test in Scandinavia and in the tropical Malaysia a service life of more than 25 years for a specific supercritical treated product is estimated. It is stated that the existing European standardisation system is insufficient when it comes to service life prediction. A number of important questions need to be addressed by the European standardisation system as soon as possible because the market and the public opinion change quickly due to environmental concern.
N Morsing, A H H Wong, F Imsgard, O Henriksen

Inspection results of preservative treated stakes, maximum 33 years in field
1992 - IRG/WP 92-3690
Since in 1958, we have undertaken field experiments in Japan. For these field experiments, we used sapwoods of Japanese cedar called Sugi (Cryptomeria japonica) because of majority of plantation forest soft wood species in Japan. For some preservatives, we added sapwood of Japanese beech called Buna (Fagus crenata), a main Japanese hard wood species. Dimensions of these specimens were 30 x 30 x 600 mm³ (T x R x L). About 30 preservatives mainly water born but 20% of oil born preservatives included, were examined for this test. We checked the damage rating every year by the observation. The service life of the preservative treated stakes were estimated at the period when the average damage rating of stakes were reached beyond 2.5 . Creosote oil, creosote oil mixed heavy oil (75:25 and 50:50) and creosote oil mixed coal tar (75:25 and 50:50) are still sound conditions for 33 years. CCA (JIS K 1554 Type 1) 2% and Tancas C 2% are still sound conditions for 28 years. Because of soft rot, the treated Buna specimens were shorten as ones of treated Sugi.
K Suzuki, K Yamamoto, M Inoue, S Matsuoka

Extending the useful life of creosoted electricity distribution poles in service
1993 - IRG/WP 93-50001-16
Creosoted transmission poles have provided good service over many decades in a whole range of environments. The use of save biocides for secondary treatments has the potential to extend the life of such poles. These techniques, together with a full understanding of the modes of failure, make it possible to establish new strategies to further improve the environmental benefits of treated wooden poles.
D J Dickinson, B Calver

Effect of a penta emulsion on the service life of Douglas fir, heartwood posts
1978 - IRG/WP 3112
C S Walters

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

Reliability-based service life prediction methodology for assessment of water protection efficiency for coatings on wood
2003 - IRG/WP 03-20268
Assessment of water protection efficiency according to EN 927-5 has been shown to give significant differences in water absorption values for different types of coatings on wood. It is shown that the combination of EN 927-5 and an artificial weathering procedure gives more information regarding expected durability and long-term performance than a single measurement of water absorption on fresh, unweathered wood. A combination of water absorption measurement and artificial weathering could become a useful tool in product development as well as in benchmarking. Together with statistical tools, such as reliability-based service life prediction methodologies for prediction of the service life of coating systems a reduction in testing time may be achieved. The predicted service life can then be the input to integrated life cycle assessment of products for wood protection.
J Ekstedt

An approach to testing the preventive effectiveness of preservative treatments for wooden joinery
1981 - IRG/WP 2156
The ecological sequence established in field trial samples exposed out of ground contact has shown the need for outdoor exposure in testing potential joinery preservative pretreatments. A system of exposure of L-joint units is proposed. Data obtained by examining samples destructively show promise as the basis for predicting service life after relatively short exposure periods (within 2 years).
J K Carey, A F Bravery, J G Savory

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

Estimation of service life of durable timber species by accelerated decay test and fungal cellar test
2002 - IRG/WP 02-20249
Many kinds of durable wood species for outdoor uses has been imported from all over the world to Japan. However information on the natural durability of these species is not sufficient to estimate the service life of them in the climate of Japan. Highly durable species such as Jarrh, Teak, Ipe, Ekki, Selangan batu, Red wood, Western red cedar showed no significant percent mass losses by accelerated decay test according to the JIS Z2101, but some of them are degraded during fungal cellar test for 4 years . The decay rating (0:sound to 5:totally decayed) of them after 4 years exposure was 1.0, 2.0, 0.0, 1.0, 0.0, 2.3, 5.0 respectively. This results indicated that the conventional accelerated decay test could not evaluate the natural durability of these highly durable species at all. Solid wood specimens treated with boiling water at 120? for one hour are subjected to the same JIS test, and the obtained percent mass losses of these species are 1.2, 2.9, 1.9, 3.8, 4.7, 17.5, 0.0 % by a brown rot fungus, Fomitopsis palustris, and 17.5, 14.3, 3.3, 8.2, 4.2, 0.0, 18.3 % by a white rot fungus, Trametes versicolor respectively. Pre-treatment of solid wood specimens for removal of heartwood extractives before a accelerated decay test would be an effective way to evaluate the natural durability of highly durable species in a laboratory.
K Yamamoto, I Momohara

Thirty-four year test of on-site preservative treatments to control decay in wood above ground
1993 - IRG/WP 93-30015
This research was initiated in 1958 to investigate efficacy of various preservatives and treating methods for new lumber going into exterior structures of buildings. Post-rail units (2x4 inches) constructed of Southern Pine sapwood, Douglas-fir heartwood, and mill run western hemlock were dip- or brush-treated before or after assembly. Units were trested with pentachlorophenol in various petroleum solvents or with copper napthenate in mineral spirits. Both painted and unpainted units were exposed on a test fence in Madison, WI. Most of the painted untreated pine units (controls) failed by 34 years. Surprisingly, painting completely protected the untreated Douglas-fir units from decay and afforded substantial protection to untreated hemlock. Significant decay in painted units was present only in lightly treated pine units (2-second dip after assembly or brush treated). Copper napthenate (1% copper) was markedly less effective than the penta treatments on unpainted pine and hemlock units. There was no evidence that type of oil carrier or incorporation of a water repellent improved effectiveness of treatment. Three or 15-minute dips in penta were equally effective. Penta-grease applied to unit ends only was effective.
T L Highley, T C Scheffer

The effect of service life and preservative treatment on the hardness of wooden poles
1989 - IRG/WP 3537
The surface hardness of utility poles is an important parameter which effects the acceptability of the pole as being safe to climb during line maintenance. The current investigation was designed to evaluate how the surface hardness of preservative treated utility poles is effected by the type of preservative, and the age of the poles. Chromated-copper-arsenate (CCA) treated red pine and jack pine poles which had been in place for up to forty years were located in Bell Canada's system in Ontario, and screened for use in the project. A survey of poles in three locations was made, and data collected on surface hardness using a 6-Joule Pilodyn. Other information recorded included the wood species identified by the brand, and the moisture content (using a resistance type moisture meter). Core samples were removed from each pole for subsequent measurement of preservative retention. The CCA retentions were determined using an X-ray analysis.
E B Jonsson, E M A Nilsson, J N R Ruddick

Test Methods – Performance Based Requirements
2004 - IRG/WP 04-20297
In this paper is briefly described the present approach to service life prediction as an essential part of the architectural engineering process. The system of testing the durability of wood is described more in detail including laboratory tests as well as field trials. It is concluded that the system has a lot of weaknesses which makes it less well suited for practical building applications. A leading theme in the criticism is that the test and classification systems are based on the requirements of the wood and preservation industry rather than those of the end-user. Finally a proposal is given for a working group to deal with this issue.
M-L Edlund, F Englund, J Jermer, T Nilsson, M Westin, K Ödeen

HCB - a new preservative combination for wood pole maintenance
1996 - IRG/WP 96-30122
New combination of heavy creosoted boron (HCB) applied on hardwood and softwood logs at different moisture content revealed successful diffusion of boron in all sapwoods within 7 days and in all sapwoods plus hardwoods within 15 days. The new cost effective paste sterilizes wood through diffusion and suitable for pole maintenance at groundline and above groundline e.g. cut ends, drilled holes, woodpecker's holes etc.
A K Lahiry

Preservative performance of copper naphthenate (SANPRESER-OGR) in brush treatment of timber
1991 - IRG/WP 3663
Preservative efficacy of copper naphthenate (SANPRESER-OGR) was evaluated in the laboartory and field trials when timber was treated by brushing. Results of field trial indicated that service life of the brush-treated timber could be approximately 10 years or longer under ground contact conditions, although life span was slightly varied with timber species and test sites. After four years' exposure in the field, the treated stakes remained resistant against termite attacks. These results strongly susgested the potential of copper naphthenate as a wood preservative for brush treatment of timber.
Y Sugai, K Hamada, M Kitada, K Tomoi

An engineering model for the decay of timber in ground contact
2003 - IRG/WP 03-20260
To predict the residual strength of an engineered structure, it is first necessary to predict the effect of decay. A model was developed in which the effective area of structural decay in large section timbers was defined as that area that could be picked out with a pen-knife. Some limited studies indicated that for practical purposes the remaining wood could be assumed to have its full residual strength. Thus once the extent of the decay has been computed, the residual load capacity of a structure can be evaluated through the use of conventional engineering mechanics. A preliminary model was developed by analysing data obtained from 5000 in-ground stakes placed around Australia. These stakes were located on 5 sites and were studied over a period of 30 years. Some more widely dispersed short term tests were also undertaken. The tests comprised untreated timber of 77 species (both hardwoods and softwoods) and timber of 2 species treated with CCA and creosote. The preliminary model was then calibrated and modified by examination of full sized structures comprising round poles and rectangular house stumps from a limited number of sites. These included the effects of maintenance activities, such as the effects of diffusion paste bandages. Using the completed model, it is now possible to compute the deterioration over the years of the load capacity of structural elements constructed with timber in ground contact. The model is directly applicable to about 80 species of timber, CCA and creosote treatments to various levels and a variety of maintenance procedures. Through use of a climate index (based on rainfall and temperature parameters) the procedure is applicable to all locations in Australia, from temperate to hot tropical regions and from rainforest to desert areas. With slight modifications, it should be possible to apply this model to any structure, fabricated from any species and located anywhere in the world.
R H Leicester, C-H Wang, M N Nguyen, J D Thornton, G Johnson, D Gardner, G C Foliente, C MacKenzie

Serviceability modeling-Predicting and extending the useful service life of FRT-plywood roof sheathing
2000 - IRG/WP 00-20210
One of the most, if not the most, efficient methods of extending our existing forest resource is to prolong the service life of wood currently in-service by using those existing structures to meet our future needs (Hamilton and Winandy 1998). It is currently estimated that over 7 x 109 m3 (3 trillion bd. ft) of wood is currently in service within the United States of America (PATH 1999). Research programs throughout North America are increasingly focusing on understanding and defining the salient issues of wood durability and by maintaining and extending the serviceability of these existing wood structures. This report presents the findings and implications of a major 10-year research program carried on at the U.S. Forest Products Laboratory. This research program developed serviceability models for fire-retardant (FR)-treated plywood roof sheathing exposed to elevated in-service temperatures and experiencing thermal degrade. FR-treated plywood roof sheathing is often required by U.S. Building Codes in roof systems for multifamily dwellings having common property walls. This 10-year research program found many important facts. Qualitatively, the mechanism of thermal degrade in FR-treated plywood was acid-hydrolysis. The magnitude of strength loss could be cumulatively related to FR chemistry, thermal exposure during pre-treatment, treatment, and post-treatment processing and in-service exposure. The effects of FR chemistry could be mitigated by use of pH buffers. The strength effects were similar for many levels of plywood quality. Quantitatively, a kinetics-based approach could be used to predict strength loss based on its time-temperature history. This research program then developed models with which to assess current condition, predict future hazard based on past service life, and then predict residual serviceability of untreated and FR-treated plywood used as structural roof sheathing. Each of these findings is briefly described in this report. There are many opportunities for extending the useful service life of wood by better maintenance, remedial treatment, or enhanced serviceability assessment to predict both residual strength and residual utility. Results of research programs such as this can be used to extend service-life by providing the engineer with a estimate of residual serviceability and thereby avoiding premature removal. Many of the concepts employed in the development of these FR-plywood serviceability models are directly applicable to the development of predictive durability models for wood as affected by decay. When such a durability-based service-life model is developed, that serviceability model will aid building code officials, regulators, contractors, and engineers in determining replacement time schedules for wood undergoing biological attack.
J E Winandy

Fungus cellar testing as an evaluation method for performance of treated timber in ground contact
2001 - IRG/WP 01-20227
A fungus cellar method for the accelerated evaluation of performance of treated wood in ground contact is described. The test soil comprised of sandy loam, vermiculite and Japanese horticulture soil "Kanumatsuchi" in a ratio of 6:2:2 by volume. The soil was inoculated with the dominant test fungus isolated with selective medium from decayed wood samples. Pairs of treated and untreated wood specimens Japanese cedar in contact with each other were buried vertically for two thirds their length. Assessment of the specimens was carried out periodically using the FFPRI graveyard damage index six- grade scale. Important factors for accelerating decay were the moisture control of the mixed soil, temperature and relative humidity, and the maintenance of fungus activity. The fungus used for inoculation favored a soil water holding capacity (WHC) of 50-80%. Under these conditions the untreated control specimens had a damage index in six months equivalent to three years FFPRI graveyard test service life, the decay accelerating rate by the fungus cellar to the graveyard test was 6 times. Under higher soil moisture conditions (WHC>80%) in the fungus cellar, soft rot was dominant and the decay rate was slower. DDAC treated specimens (8.4kg/m3) had a damage index of 2.6 in three years and 3.0 in four years. DDAC treated specimens (8.2kg/m3) in the graveyard test have been shown to be durable for 12 years (damage index of 2.3 in ten years and 2.6 after 12 years). This fungus cellar method has been shown to accelerate decay in DDAC treated specimens 3 times or more in comparison to the FFPRI graveyard test. On the other hand specimens treated with Copper-azole (6.0kg/m3 as retention of actives) had a damage index of 0 after eight years. The average service life in the FFPRI graveyard test is not decided as the Copper-azole treated specimens are in sound condition so it is not yet possible to evaluate the accelerating rate for the Copper-azole by the fungus cellar method. The fungus cellar method will be an useful method for the accelerated evaluation of performance of treated wood in ground contact provided the test conditions can be controlled.
Y Nagano

Service life of pressure treated deckings of spruce in direct contact with the ground
1988 - IRG/WP 3463
For decking outdoors in Sweden, pressure treated Scots pine (Pinus sylvestris L.) is used, on account of its treatability. The feasibility of using instead the refractory Norway spruce (Picea abies Karst.) is tested in a field trial. The spruce decks were treated together with pine decks with an ordinary Bethell process. As yet, after more than four years of exposure, neither in the battens nor in the slats of the treated spruce decks any visible sign of decay has been observed. The status of the deckings is followed up with observations of the moisture content and with Pilodyn measurements of the depth of penetration of the striker pin. The pressure treated spruce material has a consistently lower moisture content and mostly also a lower penetration depth of the Pilodyn striker pin than other untreated material.
J B Boutelje, T Sebring

A serial exposure technique for estimating probable service life of treated timber
1978 - IRG/WP 2111
This paper briefly describes part of our preliminary work aimed at developing a test procedure that culd be adopted as a standard method. A detailed version of the work has been submitted for formal publication. In both papers, the aim is to promote interest in extended laboratory testing of wood preservatives. It is believed that this work may provide the basis of a laboratory test procedure from which predictions of field performance could be made. The results of the experiment showed that (a) decay of treated blocks increased with successive soil-jar exposure, and (b) the progressive increase in decay was greatest in blocks to the lower retention of CCA.
J A Butcher

Alternatives to CCA for ground contact protection of timber: a perspective from UK on performance and service life expectations
2002 - IRG/WP 02-30289
The proposed amendment to the European Union's Marketing and Use Directive (1976/769/EEC) in respect of arsenic in CCA wood preservatives seeks to restrict the use of CCA across the European Union. CCA is an extremely important wood preservative in the UK from the manufacturing of the product to the extent of use of CCA-treated timber. Based on our experience and judgement on the use of CCA and on published literature, there do not appear to be any wholly equivalent alternatives to CCA in terms of cost and effectiveness of performance, particularly under the high hazard conditions of ground contact. This is because, although industry can offer alternative products which are approved for use on the basis of laboratory and indicative field tests, these alternatives are often more costly, behave somewhat differently and do not have the same robust track record of in-service experience. This paper presents a perspective from the UK on arsenic-free alternatives and, using examples of selected results from across the world, estimates the service life performance that the end user might expect. The evidence available indicates that about 2 or 3 times as much CC or CCB is required to give equivalent performance to CCA, 1.5 times as much copper azole and 3 times as much ammoniacal copper quaternary compounds (ACQ). It appears that users cannot expect comparable robustness of performance from the treated wood products and must pay a cost penalty for what is not universally accepted as unequivocal health and environmental gains.
E D Suttie, A F Bravery, T B Dearling

Natural durability, density and extractive contents of 42 wood species of Bangladesh.
2003 - IRG/WP 03-10490
Natural durability, density and major extractive contents of 42 lesser used or unused wood species of Bangladesh have been studied. Correlation analysis between these properties has been performed. It has been shown that natural durability of these species neither explained by water soluble nor by alcohol benzene extractive contents. Density has a weak but significant positive correlation with durability which indicates that density might have some influence on durability of these wood species.
S Akhter, K Akhter, S C Das

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