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Biological degradation resistance of pine wood treated with dimethylol compounds
1989 - IRG/WP 3528
The study reports the increase of dimensional stability and biological degradation resistance of pine wood (Pinus sylvestris L) after impregnation with dimethyloldibydroxyethyleneurea. Decay resistance was determined according to BS 838:961. Nearly complete protection against Coniophora puteana, (Schum.ex Fr. Karst) weight loss of 2-3% was shown when modification, expressed as weight gain, exceeded 15%. Resistance to biological attack of modified wood is speculated to be due to modification of the wood components and cross linking with dimethyloldihydroxyethyleneurea.
C L Videlov

Studies on the resistance of DMDHEU treated wood against white-rot and brown-rot fungi
2005 - IRG/WP 05-10566
Beech wood (Fagus sylvatica) modified with the textile finishing agent 1,3 dimethylol-4,5-dihydroxyethylen urea (DMDHEU) has shown to improve durability against the white-rot fungus Trametes versicolor. In a mini-block test, the weight loss over eight weeks of incubation decreased with increasing weight percent gain (WPG) of DMDHEU. At 25% WPG, no significant weight loss was observed, while untreated beech wood lost 37% of its initial weight under the same conditions. This increase in resistance was shown not to be caused by a biocidal effect of monomeric DMDHEU: the growth of T. versicolor and Coniophora puteana was not significantly reduced, when DMDHEU was added to sterile malt agar plates in concentrations of up to 10%. Poria placenta was not negatively affected up to a DMDHEU concentration of 5%. A solid state fermentation experiment was performed with T. versicolor on milled untreated and DMDHEU modified wood in order to determine the production of extra-cellular protein and the activity of wood-decaying enzymes. T. versicolor was not able to grow on wood treated to the highest WPG (14.9%). The activity of ligninolytic enzymes (laccase, manganese peroxidase) was highest at 7.9% WPG compared to the untreated control and 2.8% WPG. The overall production of hydrolytic enzymes was low in all cases and a clear distinction between untreated and modified wood was not possible.
P Verma, C Mai, A Krause, H Militz

Resistance of DMDHEU-treated pine wood against termite and fungi attack in field testing according to EN 252. Results after 30 months
2006 - IRG/WP 06-40354
The aim of this study was to determine the effectiveness against decay and termite attack of pine sapwood treated with pure and modified DMDHEU in a field test according to European Standard EN 252. Some of the treatments tested were able to increase, within the period of the test reported (30 months), the resistance of the wood both to micro-organisms and termites. The curing process seems to be the key factor for this increase as WPG (weight percent gain) of the modified wood alone was not sufficient for the prediction of the long-term performance.
S Schaffert, L Nunes, A Krause, H Militz

Termite resistance of DMDHEU-treated wood
2008 - IRG/WP 08-40401
Chemical wood modification with dimethyloldihydroxy-ethyleneurea (DMDHEU) or its derivatives are applicable to both solid lumber and wood-based composites. Advantages of DMDHEU-based modification are an increase of dimensional stability and high durability against white, brown and soft rot fungi. At higher chemical loadings, the hardness of the wood is considerably increased. Due to the durability improvement against fungi, in combination with the hardness improvement, a certain resistance against termite damage could be possible. Two field trials were conducted against Coptotermes acinaciformis (Froggatt) in south-east Queensland, Australia and one field trial against Mastotermes darwiniensis Froggatt in northern Queensland with DMDHEU-treated wood. Both subterranean termites are of major economic importance in Australia. Four timber species (Scots pine, beech, slash pine and spotted gum) and two levels of DMDHEU were used. The results indicated that feeding pressure by the termites was sufficient within all trials for a valid test. DMDHEU successfully prevented damage by C. acinaciformis, but not by M. darwiniensis: Scots pine heartwood was resistant to both species. Scots pine sapwood appeared slightly more treatable with DMDHEU than beech. Implications for further research are discussed.
H Militz, S Schaffert, B C Peters, C J Fitzgerald

Postia placenta cellulase gene expression in modified wood during incipient decay
2013 - IRG/WP 13-40626
In optimization of modified wood, it is important to understand the mode of action of the wood modification and how the fungi response to it. The aim of this study was to investigate the expression of cellulases during the first two weeks of Postia placenta exposure in acetylated, DMDHEU-treated and thermally modified as well as in untreated wood. Using real-time PCR, the gene expression patterns of the P. placenta endoglucanase Ppl103675 and β-glucosidase Ppl112501 during 56 days of decay was analyzed. Preliminary data indicate that both genes are expressed at higher values in untreated wood at 56 days of exposure (56% mass loss) than at 14 days. We also saw high values for both genes at ten days of exposure for both untreated (11% mass loss) and modified woods (all 0% mass loss). We conclude that the high values at 10 and 56 days in untreated wood may be due to that monosaccharides and by-products from the cellulose degradation process, known to induce cellulase expression, have been released from the wood cell wall. Furthermore, the high values at ten days in the modified woods may be the result of an unknown regulatory mechanism. In addition, we found that the expression patterns for the P. placenta endoglucanase Ppl103675 and β-glucosidase Ppl112501 are very similar in the three modified woods investigated, but different from the patterns in untreated wood. This might be an indication that all the herein studied wood modifications affect fungi in the same way, i.e. they have the same mode of action.
R Ringman, A Pilgård, K Richter

Possible targets of wood modification in brown rot degradation
2014 - IRG/WP 14-40676
Wood modification protects wood from fungal degradation in a non-toxic manner. However, the mechanisms behind the decay resistance in modified wood are currently unknown. The aim of this study was to discuss the i) colonisation, ii) nutrient recognition, iii) transcription, iv) depolymerisation and v) hydrolysis steps in the brown rot degradation progress and explore whether they are inhibited by wood modification, based on new and previously published data from our group. In previous studies, it has been shown that fungi were able to colonise modified wood, to recognise it as a source of nutrients and express genes associated with cellulose degradation while growing on modified wood. In this study, Fenton derived hydroxyl radicals (∙OH) and brown rot cellulases were able to degrade modified wood. We conclude that the five degradation steps discussed in this paper are unlikely targets for wood modification and that wood modification rather inhibits a step that in a schematic overview of the brown rot degradation process is downstream from transcription but upstream of depolymerisation and hydrolysis.
R Ringman, A Pilgård, G Alfredsen, B Goodell, K Richter

Long-term performance of DMDHEU-treated wood exposed in ground, above ground and in the marine environment
2018 - IRG/WP 18-40825
Chemical wood modification with N-methylol compounds such as 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU) has been studied intensively since the 1990s. Research of the past years focused on treatment of Scots pine (Pinus sylvestris L.) and European beech wood (Fagus sylvatica L.) and was shown to be applicable to improve specific material properties. A high resistance against wood-destroying fungi was proved in various laboratory trials with basidiomycete monocultures and in soil substrate, by means of mass losses (ML) corresponding to durability class (DC) 1-2 (‘durable to very durable’). This paper reports on the field performance of DMDHEU modified wood exposed above-ground (UC3, rail test, block test, deckings), in-ground (UC4) and in the marine environment (UC5). The aim of this study was to evaluate results from more than 7 years field testing with respect to the DMDHEU treatment level, wood species (Scots pine, European beech, Spotted Gum (Corymbia maculata K.D. Hill & L.A.S. Johnson), Slash pine (Pinus eliottii Engelm.)) and climate conditions at the different test sites. Field studies with different test procedures were started in 2003 (Moitas, Portugal), 2007 (Redlands and South Johnstone, Australia) and 2008 (Stamsmåla, Sweden; Goettingen, Germany). The same material was exposed in Australia and Sweden. Untreated, UC3 and UC4 (CCA) treated as well as modified wood indicated different severity at different locations. In general, DMDHEU was shown to significantly improve the biological durability of non-durable Scots pine sapwood. After exposure above-ground and in-ground under different climate conditions, DMDHEU treated Scots pine was classified as ‘durable to very durable’ (DC 1 - 2). Tests under UC5 conditions were started in 2008 in the North Sea (Wilhelmshaven, Germany) and the Baltic Sea (Hejlsminde, Denmark). After 9 years of exposure, Scots pine sapwood treated with DMDHEU was classified as ‘very durable’ (D) also under UC5 conditions with respect to attack by the shipworm Teredo navalis. However, DMDHEU modification seemed to be more efficient in pine wood so that higher chemical loadings are required for beech to reach similar resistance against wood-destroying fungi.
L Emmerich, H Militz, C Brischke

Durability classification of preservative treated and modified wood
2019 - IRG/WP 19-20659
EN 350 (2016) allows formally to determine durability classes (DC) for wood products and wood-based materials, which was previously only possible for untreated wood in the form of natural durability. In a first study, the University of Goettingen carried out the durability classification of chemically modified (modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea, DMDHEU) and preservative-treated specimens of various hardwoods and softwoods. The objectives of the work were the determination of mass losses caused by basidiomycetes (CEN/TS 15083-1, 2005) and soft rot fungi (CEN/TS 15083-2, 2005) and to classify durability according to EN 350 (2016). The results showed that a durability classification of chemically modified and preservative treated wood is possible. The tests CEN/TS 15083-1 (basidiomycetes) were carried out with the test fungi C. puteana and T. versicolor and showed that the durability classification is based predominantly on the mass losses caused by C. puteana. However, the distribution of the mass loss values is high, especially for DMDHEU modified collectives. Examinations in accordance with CEN/TS 15083-2 have in many cases led to similar classifications as the tests according to CEN/TS 15083 1. The methodology for evaluating the data proposed in EN 350 (2016) needs to be optimized.
S Bollmus, L Bachle, C Brischke, H Militz

Experience Experience from over 20 years of field trials of resin treated wood – Marine borer resistance of MMF and DMDHEU modified wood
2021 - IRG/WP 21-10976
In 1999 a field test of Scots pine treated with MMF (Methylated Melamine Formaldehyde) resin and acetylated Scots pine post treated with MMF resin was started. Six years later a commissioned full NWPC test for BASF of Belmadur® (DMDHEU resin treated wood) was started at the same site. The testing, according to European Standard EN 275, was done in a bay by Kristineberg Marine Research Station on the Swedish west coast. The marine borer (mainly Teredo navalis) activity at the test site is very high, always resulting in failure of control specimens within a year. The two sets of CCA-treated reference specimen at low retention level (approximately UC3 level) failed with an average service life of 3.6 and 3.8 years, respectively. The first set of CCA-treated reference specimens at the high retention level (UC5 level) failed with an average service life of 13.5 years. The two sets of MMF resin modified wood specimens at low and medium treatment level (WPG=11 and 23, respectively) have failed with 4.8 and 15.3 years’ service life, respectively. The set with high MMF treatment level (WPG=47) is only slightly attacked after 21 years. Acetylated wood post treated with MMF resin at low retention level (WPG=19+8) are severely attacked but performing better than CCA at high retention level. Acetylated wood specimens post treated with MMF resin at medium retention level (WPG=21+19) are rated sound after 21 years. All DMDHEU specimens at all treatment levels (WPG = 28, 35 and 42, respectively) are perfectly sound after 15 years of exposure. DMDHEU seems to provide excellent resistance to borer attack at the treatment levels included in this test.
M Westin, P Larsson Brelid, A O Rapp, J Habicht

Confocal laser scanning microscopy of a novel decay in preservative treated radiata pine in wet acidic soils
1997 - IRG/WP 97-10215
Light microscopy of radiata pine (Pinus radiata D. Don) field test stakes (20x20x500mm3) exposed in wet acidic (pH 3-4) soil for 12 - 24 months showed predominance of an unusual type of decay characte-rised by tunnelling attack of wood cell walls. After two years decay was moderate to severe in wood treated to ground contact CCA specifications and also equivalent retentions of creosote, and a number of new generation preservatives. Relative to other New Zealand temperate test sites and also an Australian tropical site, the New Zealand acidic soil test site was very aggressive. Correlative scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to elucidate the micromorphology of this attack. Tunnels of diameter 0.2-5 µm were present throughout all layers of the cell wall, and their orientation was not related to cellulose microfibril orientation. They also showed no preference for particular cell wall layers, indicating a lignin degrading capability. CLSM images showed that living, connecting fungal hyphae were present in the cell lumina and tunnels. This type of attack was predominant in wood that was highly saturated with water whereas wood that was less moist was predominantly attacked by classical white rot. Ongoing isolation and incubation studies in conjunction with further microscopy should enable identification of the fungal species involved.
R N Wakeling, Ying Xiao, A P Singh

Biological screening assays of wood samples treated with creosote plus chemical additives exposed to Limnoria tripunctata
1980 - IRG/WP 408
Laboratory methods for exposure of treated wood coupons to Limnoria tripunctata are described. Chemical additions to creosote were screened using this method. Three pesticides, Endrin, Kepone, and Malathion proved particularly effective. The addition of varying percentages of naphthalene to creosote using several treatment methods are currently being assayed. Results to date show that the coupons treated by the empty cell method have better performance than those prepared by the toluene dilution method. The naphthalene coupons treated by the full cell method show no attack after six months' exposure.
B R Richards, D A Webb

Analysis of tebuconazole in wood treated with Tanalith™ E
1999 - IRG/WP 99-20158
A simple gas chromatographic method for determining tebuconazole in Tanalith™ E treated wood is described. A two step sequential extraction procedure with methanol was used. Sample extracts were analysed without cleanup or concentration using capillary column GC with thermionic specific detection. The performance of the method was assessed using radiata pine (Pinus radiata) sapwood, radiata pine heartwood, and spotted gum (Corymbia citriodora) sapwood as substrates. Recoveries from fortified samples ranged from 97% to 103%. The precision of the method was assessed by analysing a number of actual treated wood samples over a range of retention levels, which produced relative standard deviations in the range of 3% to 8%.
D E Ferlazzo

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

Loss of preservatives from treated wood during service
1992 - IRG/WP 92-3734
During the 23rd IRG conference in Harrogate the matter of preservative losses from treated wood during service was raised. We were asked to collect information in this field and ask now for help from you. Many tests have been carried out at a laboratory scale to study fixation and leaching from wood treated with different preservatives. Very little, however, is reported on losses of preservatives during service. Since these values are of great relevance regarding environmental impact and the final disposal, reuse or recycling of treated wood, it is of great importance to get as much information as possible on the amount of active ingredients lost during service life. We are convinced there are quite a lot of analytical data and additional information available in many places all over the world. It appears to be rewarding to collect those data and put them together adequately to get an astimate of the losses of the different components based on a broad scale of in service situations. This work will be done as soon as information is available and it is intended to present the results on next IRG meeting.
M-L Edlund, D Rudolph

Electrodialytic remediation of creosote and CCA treated timber wastes
2002 - IRG/WP 02-50190
There is a growing concern about the environmental issue of impregnated timber waste management, since an increase in the amount of waste of treated wood is expected over the next decades. Presently, no well-documented treatment technique is yet available for this type of waste. Alternative options concerning the disposal of treated wood are becoming more attractive to study, especially the ones that may promote its re-use. Inside this approach, the electrodialytic process (ED) seems a promising technique for removal of preservative chemicals from treated wood waste. The method uses a direct electric current and its effects in the matrix as the “cleaning agent”, combining the electrokinetic movement (mainly due to electromigration, but also electro-osmosis and electrophoresis), with the principle of electrodialysis. This work reports results from the application of the electrodialytic process to an out-of-service Portuguese creosote and CCA-treated Pinus pinaster Ait. railway sleeper and pole. The behaviour of the process is described and the main results discussed. The average removal rate, estimated in accordance with prEN 12490, for creosote from treated timber waste was around 40 %.. For CCA treated timber waste, experimental conditions that could optimise the process efficiency (e.g. current density, time) were studied. The highest removal rates obtained until now, in our studies, were 93 % of Cu, 95 % of Cr and 99 % of As for sawdust using 2.5 % oxalic acid (w/w) as the assisting agent. For CCA treated wood waste in the form of chips, the best removal rates obtained until now were 84 % of Cu, 91 % of Cr and 97 % of As.
E P Mateus, A B Ribeiro, L Ottosen

Possible regulatory status of treated wood waste and implications
1998 - IRG/WP 98-50101-07
In relation to the European Community or the French regulations, treated wood waste can get two different regulatory status: <<recycled product or fuel>> or <<waste>>. Then, into the waste status, two categories are possible for these residues: <<domestic waste and assimilated>> or <<hazardous waste>>. These different status and categories are important for the environmental issue of treated wood waste management. But they also can have strong economical implications, linked to the waste management cost on one hand and on the materials image on the other hand. On the basis of the EC regulations, up to now, no treated wood waste is namely quoted as <<hazardous waste>>. However, through the classification criteria defined by different EC directives, creosote or heavy metals treated wood waste could be to considered that way. The technical arguments for such a classification and the practical implications are discussed.
G Deroubaix

Termite resistance of pine wood treated with chromated copper arsenates
1997 - IRG/WP 97-30128
Two four-week, no-choice laboratory tests were performed with CCA-treated southern yellow pine and radiata pine against Formosan subterranean termites, Coptotermes formosanus. CCA retentions as low as 0.05 kg/m3 (0.03 pcf) provided protection from all but light termite attack (rating of 9 on a 10-point visual scale). Similar and consistent light attack on wafers containing retentions as high as 6.4 kg/m3 (0.4 pcf), coupled with complete termite mortality, demonstrates that the mode of action of CCA treatments relies upon toxicity rather than having any repellent effects against termites.
J K Grace

Application of radio frequency heating to accelerate fixation of CCA in treated round-wood
1999 - IRG/WP 99-40133
The potential of radio frequency heating to accelerate the fixation of chromated copper arsenate (CCA) in treated round-wood was assessed. Pre-dried Douglas-fir and western red cedar round-wood sections were pressure treated with CCA in a pilot plant retort, after which they were placed individually in a pilot radio frequency (RF) chamber. Based upon the color reaction of chromotropic acid with hexavalent chromium and the quantitative assessment using diphenyl carbazide, fixation was achieved in less than 6 hours. During heating, the temperature at various locations inside the pole sections was monitored by fiber-optic thermocouples. The moisture profiles before, and after fixation, were also recorded. Further studies will examine other benefit of RF heating, including a) sterilization, and b) rapid drying of round-wood with minimum check formation.
Fang Fang, J N R Ruddick

Laboratory decay test of Burmese in and kanyin treated with three wood preservatives
1982 - IRG/WP 3210
Laboratory decay tests were performed on samples of In (Dipterocarpus tuberculatus Roxb.) and Kanyin (Dipterocarpus alatus Roxb. and Dipterocarpus turbinatus Gaertn f.) pressure treated with three wood preservatives - copper arsenic additive (CAA - a variation of ammoniacal copper arsenate), Arquad C-33 (a waterborne quaternary ammonium formulation), and tributyltin acetate (TBTA) dissolved in ethanol. Pressure treatments with each preservative involved a 0.5 - 1 hour vacuum followed by a 4 hour period of pressure. This resulted in a very variable treatment because of the inherent difficulty in treating these woods. The decay tests entailed a slightly modified form of the AWPA M10-77 standard soil-block test using three brown-rot and three white-rot fungi. The untreated In and Kanyin samples were moderately susceptible to decay though weight losses were very variable and some samples of Kanyin (usually the densest and least permeable) were naturally resistant. At the concentrations tested CAA was the most effective in reducing weight losses incurred in the soil-block tests. TBTA was successful in controlling decay caused by all but two of the test fungi. It is suggested that preservative retentions for TBTA conforming to those included in the Candadian standard for bis (tributyltin) oxide would exceed the toxic limit for all the fungi tested
J N R Ruddick, R S Smith, A Byrne

Studies on accelerated ageing procedures with TBTO-treated wood
1985 - IRG/WP 2244
The efficacy of various procedures for accelerated ageing of organotin based wood preservatives in treated wood has been investigated. It was found that leaching of the treated wood samples in water according to the European Standard EN 84 was not satisfactory for organotin based preservatives and is probably also unsuitable even for other types of organic solvent preservatives. Keeping tributyltin oxide (TBTO) treated samples in a heating cabinet at 70°C for five weeks, however, had a considerable effect on the breakdown of TBTO and the subsequent decay test. Therefore, an ageing procedure involving a heating period should be considered for all organic solvent wood preservatives. The investigation also confirmed that elevated temperatures accelerate the degradation of TBTO and that there is a strong correlation between the percentage of TBTO in the wood and its resistance against decay.
J Jermer, M-L Edlund, B Henningsson, W Hintze

Effect of water repellents on leaching from CCA treated wood
1995 - IRG/WP 95-50044
CCA treated fence boards brushed with a water repellent finish had consistently lower leaching losses of all CCA components compared to the rate for matched samples without the water repellent. These results are after 12 cycles of simulated rainfall in the laboratory (1800 mm rainfall total) and four months of natural rain exposure in Toronto.
P A Cooper, R MacVicar

Letter to the IRG meeting at Peebles, 1978
1978 - IRG/WP 181
J F Levy, R Cockcroft

Use of vermiculite as substrate in assays on phytotoxicity of treated wood
1989 - IRG/WP 3547
It is considered the possibility of using vermiculite instead of soil as substrate in assays on phytotoxicity of wood treated with preservatives for agricultural use. Three organic preservatives were used. It had been tested the behaviour of both, vermiculite and soil in case of preservative leaking due to a leach. So that, assays of germination with cucurbitaceous were carried out, mixing a dose of preservatives with both substrates.
M V Baonza Merino, D Franco

European standardization for wood preservation
1989 - IRG/WP 2335
G Castan

Effect of protective additives on leachability and efficacy of borate treated wood
2002 - IRG/WP 02-30290
Borate preservatives have been used extensively in many countries as an effective means for protecting wood against fungal and insect attack especially in interior environments. Under exterior conditions, borate compounds have a main disadvantage as they can be leached from treated wood as a result of their water solubility. In this study, we compared the potential of different additives for reducing the leachability of boron preservatives from treated wood. Scots pine sapwood (Pinus sylvestris) and poplar (Populus trichocarpa x deltoides) test samples were vacuum treated with 1 % BAE (Boric Acid Equivalent) disodium octaborate tetrahydrate (DOT) solutions containing various additives e.g. glycerol/glyoxal, polyvinylpyrrolidone (PVPY), a commercial resin compound and a commercial water repellent. The European Standard EN 84 was used as a leaching test for both coated and uncoated specimens. The results of chemical analysis of leachates taken at different periods showed that the use of protective additives reduces the boron leachability. The glycerol/glyoxal additive applied to treated pine sapwood showed the best performance. The percent of boron retained in uncoated pine sapwood was 26% while coated samples still retained 45% after 14 days of intense leaching. Similar tests on poplar revealed 19% and 34% for uncoated and coated samples, respectively.This represents a gain of 20 to 25% compared to pure DOT treated specimens of both wood species. Preliminary biological tests were carried out on malt agar using a miniblock technique for uncoated pine sapwood and beech, with Poria placenta and Coriolus versicolor, respectively. After six weeks of exposure to fungal attack all boron protective systems tested proved their effectiveness, as none of the test samples exhibited a mass loss exceeding 4%. The reference 1% BAE without protective additives showed an average mass loss of 15%. Finally, test data are reported of standard EN 113 testing in view of a further evaluation of the biological efficacy of combined DOT-additive treatments.
A Mohareb, J Van Acker, M Stevens

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