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Wood preservation for preventing biodeterioration of Cross Laminated Timber (CLT) panels assembled in tropical locations
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Structural Integrity Procedia 00 (2018) 000–000 Available online www.sciencedirect.com Available online at at www.sciencedirect.com Structural Integrity Procedia 00 (2018) 000–000
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Procedia Structural Structural IntegrityIntegrity Procedia1100(2018) (2016)242–249 000–000
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XIV International Conference on Building Pathology and Constructions Repair – CINPAR 2018 XIV International Conference on Building Pathology and Constructions Repair – CINPAR 2018
Wood preservation for preventing biodeterioration of Cross Wood preservation for preventing biodeterioration of Cross Laminated Timber (CLT) panels assembled in tropical XV Portuguese Conference Fracture, PCF 2016, 10-12 February 2016, Paço locations de Arcos, Portugal Laminated Timber on (CLT) panels assembled in tropical locations a b c Gabriela Lotufo Oliveira *, Fabiana Lopes de Oliveira , Sérgio Brazolin Thermo-mechanical modeling of a high pressure turbine blade a b Gabriela Lotufo Oliveira *, Fabiana Lopes de Oliveira , Sérgio Brazolinc of an Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo, Rua do Lago, 876, São Paulo, Brazil airplane gas turbine engine Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo,Prado, Rua do532, Lago, SãoBrazil Paulo, Brazil Instituto de Pesquisas Tecnológicas (IPT), Av. Prof. Almeida São876, Paulo, a, b a, b
c c
Instituto de Pesquisas Tecnológicas (IPT), Av. Prof. Almeida Prado, 532, São Paulo, Brazil
P. Brandãoa, V. Infanteb, A.M. Deusc*
AbstractaDepartment of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal Abstract b Department Mechanical Técnico, Universidade Lisboa,panels. Av. Rovisco Pais, 1, 1049-001 Lisboa, CrossIDMEC, Laminated Timberof (CLT) is a Engineering, constructionInstituto systemSuperior based on pre-fabricated soliddewood As this system is produced Portugal Cross Timberits(CLT) is a construction system based pre-fabricated solid wood panels. As this system is processes produced with naturalDepartment material, implementation is associated theon adoption of preventive c a Laminated CeFEMA, of Mechanical Engineering, Institutowith Superior Técnico, Universidade de measures Lisboa, Av.against Roviscopathological Pais, 1, 1049-001 Lisboa, with a natural material, itsbiodeterioration. implementation is associated with the adoption of as preventive measures against pathological intrinsic to wood, such as This phenomenon can be defined undesirable changes in wood elements processes provoked Portugal intrinsic wood, such biodeterioration. This phenomenon can be such defined as undesirable changes provoked by livingtoorganisms thatasuse wood as food supply. Microorganisms, as fungi, and insects, such in as wood termiteelements and wood-boring by livingareorganisms that use wood asTheir food supply. Microorganisms, such as fungi, and insects, such as termite and wood-boring beetles among these organisms. developments occur under favorable moisture and temperature circumstances; thus, beetles are among are these organisms. Their occur under favorable moisture and temperature circumstances; thus, climate conditions important factors fordevelopments the wood structure durability. The use of CLT panels in tropical climates must be Abstract climate conditions arepreservation important factors fortotheavoid wood structure use of CLT tropical climates must be associated with wood methods decay of thedurability. structural The components. Thispanels paper in aims to discuss preservation associated with wood preservation methods to avoid components decay of thethe structural components. This paper aims towhere discuss preservation During applied their operation, modern aircraftlocations, engine are subjected to increasingly demanding operating conditions, treatment to CLT panels in tropical comparing standards adopted in different countries CLT buildings especially the high pressure turbine (HPT) blades. Hence, Such conditions cause these parts in to different undergo different types ofCLT time-dependent treatment applied to CLT panels in tropical locations, comparing the standards adopted countries whereand buildings are used. Additionally, a case study was conducted. samples of Pinus sp. from the south region of Brazil treated with degradation, one of which creep.solution) A model using the finite element method was developed, order toand be able to predict are used. Additionally, a case study was conducted. Hence, of Pinus sp.(FEM) from region of Brazil treated with CCB (copper, chromium andisboron were tested to samples identify the penetration andthe thesouth retention ofin the preservation product. thetests creep behaviour ofand HPT blades. Flight data records (FDR) for a 6232:2013. specificand aircraft, provided by preservation athat commercial aviation CCB (copper, chromium boron solution) were tested to identify the penetration the retention of the product. The followed the method suggested by Brazilian standard ABNT NBR The results showed it is necessary to company, werecontrol used to obtain thermal mechanical dataABNT forwood three different flight cycles. orderorganisms. tothat create the 3D model The tests quality followed the method suggested byand Brazilian NBR 6232:2013. The resultsInshowed it is necessary to establish to avoid CLT production withstandard no adequate protection against xylophagous neededquality for thecontrol FEM to analysis, a HPT blade scrap wasadequate scanned, andprotection its chemical composition and organisms. material properties were establish avoid CLT production with no wood against xylophagous obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D Copyright © 2018 Elsevier B.V. All rights reserved. Copyright © 2018 Elsevier B.V. All rights reserved. rectangular block shape, in order torights better establish the model, and then with the real 3D mesh obtained from the blade scrap. The Copyright ©under 2018 Elsevier B.V. All reserved. Peer-review responsibility of CINPAR the CINPAR 2018 organizers Peer-review under responsibility 2018 organizers overall expected behaviour of in the terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a Peer-review under responsibility of the CINPAR 2018 organizers model can be useful in the goal of predicting turbine blade life, given a set of FDR data. Keywords: Cross Laminated Timber (CLT); wood structures; biodeterioration; preservation treatment. Keywords: Cross Laminated Timber (CLT); wood structures; biodeterioration; preservation treatment.
© 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016.
Keywords: High Pressure Turbine Blade; Creep; Finite Element Method; 3D Model; Simulation.
* Corresponding author. Tel.: +55 11 30914539 * Corresponding Tel.: +55 11 30914539 E-mail address:author. [email protected] E-mail address: [email protected] 2452-3216 Copyright © 2018 Elsevier B.V. All rights reserved. 2452-3216 Copyright © 2018 Elsevier All rights Peer-review under responsibility of the B.V. CINPAR 2018 reserved. organizers. Peer-review under responsibility of the218419991. CINPAR 2018 organizers. * Corresponding author. Tel.: +351 E-mail address: [email protected] 2452-3216 © 2016 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the Scientific Committee of PCF 2016. 2452-3216 Copyright 2018 Elsevier B.V. All rights reserved. Peer-review under responsibility of the CINPAR 2018 organizers 10.1016/j.prostr.2018.11.032
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Gabriela Lotufo Oliveira et al. / Procedia Structural Integrity 11 (2018) 242–249 Gabriela Lotufo Oliveira, Fabiana Lopes de Oliveira, Sérgio Brazolin / Structural Integrity Procedia 00 (2018) 000–000
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1. Introduction According to ANSI/APA 320 (2018), Cross Laminated Timber (CLT) panels are a prefabricated engineered wood product, made of at least three orthogonal sawn lumber layers. The panels have been developed first in Austria during the 1990’s. Currently, the product is well established in Europe and, over the last years, its use has increased in other continents, such as North America and Oceania. In South America, the panel production started in Brazil in 2012. Some of the countries where CLT has recently been implemented have tropical climates, with high temperatures and humidity. Consequently, wood structural components located in those regions are more susceptible to building pathologies caused by biodeterioration, than they are in dry or cold climates (Scheffer, 1971). Wood is susceptible to both abiotic (chemicals, fire and sunlight damage, for example) and biotic deterioration agents (Morrell, 2006). Biotic agents are living organisms that use wood as food supply, provoking undesirable changes in wood elements. Microorganisms, as fungi and bacteria, insects, such as termite and wood-boring beetles, and marine borers are among these organisms. Nearly all decay biotic agents require oxygen. Another factor necessary for the phenomenon is adequate temperatures. Although organisms have a variety of temperature requirements, the perfect range temperature for their survival is from 5°C to 40°C (Morrell, 2006). Furthermore, for decay caused by microorganisms to occur, the wood moisture content must be higher than the fiber saturation point, which is around 30%. When this level is reached, free water present in wood enables the transportation of the enzymes produced by the microorganisms to the wood cell polymers, among other purposes. The enzymes are responsible for decomposing those polymers and the molecules resulting from this process are transported back to the microorganism through water (Oliveira et al, 1986). Consequently, most organisms are unable to cause damage once the wood moisture content drops below 30%. In a tropical country, the occurrence of termites and beetles in wood buildings and heritage is significant. The termites are the main problem with native and exotic species (Oliveira, et al, 1986). Milano and Fontes (2002) estimated losses at US$ 10,000 per year for treatments, repairs and replacements of deteriorated wood components. However, some wood species have natural resistance, since they produce chemicals that inhibit or are toxic to xylophagous organisms. As for the species that do not produce those extractives, and therefore have low natural resistance, one of the remaining strategies to protect them is the preservation treatment. Preservation treatments improve wood resistance, by means of impregnation of chemicals that are toxic to decay agents (Lelis et al, 2001). Those treatments strongly increase the useful life of a wood product by 20 to 40 times that of untreated wood (Morrell et al, 2006). Since CLT panels are mostly produced of softwoods, whose natural resistance to deterioration is low, their use in tropical locations, such as Brazil, Australia and some parts of the USA, must be associated to preservation methods to avoid the decay of the structural components. Therefore, this paper aims to discuss preservation treatment used in the mentioned countries, where CLT buildings have recently been assembled, by comparing the standards adopted in each one. Additionally, a case study was conducted. Hence, samples of pinewood from the south region of Brazil and treated with CCB (copper, chromium and boron solution) were tested to identify the penetration and retention of the preservative. 2. Potential wood decay in tropical climates Considering the influence of climate conditions on the wood biodeterioration process, Scheffer (1971) developed a climate index to estimate potential for decay in wood structures above ground, in order to evaluate the need for protective measures. The climate index value proposed by Scheffer is calculated from local weather data by the following equation: ���.
Climte index = �
���.
[(� − 2)(� − 3)] 16,7
(1)
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Gabriela Lotufo Oliveira et al. / Procedia Structural Integrity 11 (2018) 242–249 Gabriela Lotufo Oliveira, Fabiana Lopes de Oliveira, Sérgio Brazolin / Structural Integrity Procedia 00 (2018) 000–000
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Where: T is the average monthly temperature (°C) D is the average number of days in the month with 0,25 mm precipitation or more The author calculated the climate index value for the metropolitan areas of the USA, resulting in a climate index map of the country, divided in three index zones that represent three levels of above ground decay. Figure 1 shows the map of the USA reproduced in the Wood Handbook (Forest Products Laboratory, 1999, apud Carll, 2009, p.2) and based on the index proposed by Scheffer.
Fig. 1. Scheffer´s climate-index map of the USA.
According to Scheffer, in areas from the map with index values of less than 35, there are the least favorable conditions for decay; in those with values between 35 and 70, there are intermediately favorable conditions; in the ones with values greater than 70, there are the most conductive conditions to decay (Scheffer, 1971). Decay hazard maps based on Scheffer’s index have also been developed for Brazil and Australia, by Martins et al. (2003) and Carter et al. (1993, apud Foliente, 1999, p.1293), respectively, and are shown on Figure 2 and Figure 3.
Fig. 2. Brazilian´s climate-index map, based on Scheffer´s index.
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Fig. 3. Australian´s climate-index map, based on Scheffer´s index.
Comparing the three maps, it´s possible to see that in all studied countries, there are regions with climate conditions most favorable for decay to occur. However, as pointed by Martins et al. (2003), in all Brazilian regions, with just a few exceptions, there are the most conductive conditions to decay, since the index values are higher than 70 in most of the country area. Therefore, it can be concluded that from the three countries above, Brazil is the one with the highest potential for decay to occur. 3. Wood preservation The modern age of wood preservation started with the patenting of Creosote, as a wood preserver, and with advent of the full cell process for delivering that product into wood, back at the 1830s. Creosote was for a long time the most effective of all treatment systems available (Morrell, 2006). This oil-based preservative was mainly used for poles, crossties and posts, not recommended for buildings, considering its odor and oil exudation. In the 1930s, two important new systems were developed, Pentachlorophenol and CCA (Chromate Copper Arsenate). Pentachlorophenol was an oil-based material that emerged as a substitute to Creosote and CCA was a mixture of copper, chromium and arsenic - metals dissolved in water. Cooper is a highly effective fungicide and arsenic is an insecticide; chromium reacts with both promoting their fixation in the wood, avoiding their leaching to the environment. Until the 2000s, CCA was the most important chemical used to protect wood (Morrell, 2006). However, in the USA, around the beginning of the 2000s, there was a growing concern about the health effects associated with exposure to CCA preserved wood due to arsenate. The greatest concern was the risk of developing some types of cancer later in life (West, 2004). Therefore, on December 31, 2003, the Environmental Protection Agency (EPA) and the lumber industry of the United States decided to withdraw the registration of CCA for residential use (Morrell, 2006), such as playgrounds, decks and picnic tables, voluntary; thus, avoiding direct contact with people. Nevertheless, CCA-treated wood is still used for commercial and industrial purposes. In this scenario, other chemicals were developed to replace arsenate-based products. One of them is a mixture of copper, chromium and boron (CCB), diluted in water, which has been first commercialized in Germany at the beginning of the 1960s (Oliveira et al., 1986). In this chemical, boron is effective against insects, functioning as an arsenate substitute. In Brazil, CCB is frequently used for construction, although there is no governmental restriction to use CCA. To regulate the use of those chemicals, in most countries, there are wood treatment specifications. In the USA, the American Wood Protection Association (AWPA), founded in 1904, standardizes treatment processes and develops standards for wood preservatives and treatments for different degrees of risk of decay, which are divided in use categories (Morrell, 2006), considering the biological use conditions and the presence of xylophagous organisms (AWPA, 2017). As shown in Table 1, the first category (UC1) represents the lowest risk and the last category (UC5), the highest.
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Table 1. American Use Categories. Use Category
Service Conditions
Deterioration Agents
UC1
interior construction
insects only
above ground dry UC2
interior construction
decay fungi and insects
above ground damp UC3A
exterior construction
decay fungi and insects
above ground coated & rapid water runoff UC3B
exterior construction
decay fungi and insects
above ground uncoated or poor water runoff UC4A
ground contact or fresh water
decay fungi and insects
non-critical components UC4B
ground contact or fresh water critical components or difficult replacement
UC4C
ground contact or fresh water critical structural components
decay fungi and insects with increased potential for biodeterioration decay fungi and insects with extreme potential for biodeterioration
UC5A
salt or brackish water and adjacent mud zone which includes Long Island, NY and northward, north of San Francisco
salt water organisms
UC5B
salt or brackish water and adjacent mud zone south of Long Island, NY to the southern border of GA, south of San Francisco
salt water organisms including creosote tolerant Limnoria tripunctata
UC5C
salt or brackish water and adjacent mud zone South of GA, Gulf Coast Hawaii and Puerto Rico
salt water organisms including Martesia, Sphaeroma
In Australia, standard AS 1604– Specification for preservative treatment (AS, 2012) defines that any preservative treated product must be branded, indicating, among other characteristics, the Hazard Class this product can be exposed to, likewise the American Use Categories. The Australian Hazard Classes are six totally, as shown in Table 2.
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Table 2. Australian Use Categories. Use Category
Service Conditions
Deterioration Agents
H1
completely protected from the weather, well ventilated and protected from termites
borers
H2
protected from wetting, no leaching
borers and termites
H3
periodic moderate wetting and leaching
moderate decay, borers and termite
H4
severe wetting and leaching non-critical applications
severe decay, borers and termites
H5
extreme wetting and leaching, critical application
very severe decay, borers and termites
H6
prolonged immersion in sea water
marine wood borers
In Brazil, standard ABNT NBR 16143:2013 – Preservação de madeiras – Sistema de categorias de uso (ABNT, 2013c), presents six categories based on the exposure of the wood component, similarly to those from Australia. The main difference between the Brazilian and Australian Use Categories is that the first one considers three types of termites and three types of fungi. One of the types of termite is also a possible deterioration agent in the first Use Category. The bigger amount of decay agents considered in the Brazilian preservation standards indicates more favorable conditions for decay to occur in this country, as Scheffer’s climate index. However, just four preservatives are registered for pressure treatment of wood in Brazil (Creosote, CCA, CCB and CA-B (Copper Azole Type B)). In the USA, more than twenty preservatives are standardized by ASTM. Creosote, CCA-C, Alkaline Copper Quaternary Type A (ACQ-A), pentachlorophenol, CA-B, Ammoniacal Copper Zinc Arsenate (ACZA) and many others are among them. As for Australia, the registered preservatives are: CCA, ACQ, Copper Azole (CA), Creosote and Boron. One of the explanations for that occurrence is the minor use of wood as structural component in the Brazilian construction sector, mostly for cultural reasons. 4. Case study: CLT treated with CCB in Brazil The use of CLT, made of pinewood, has recently begun in Brazil, typically for high-standard residences. The Brazilian use category system standard (ABNT, 2013c) establishes the need of quality control, measuring two parameters for pressure treatment: retention, or the quantity of active ingredient introduced into the dry wood (below 30%), expressed as kg/m³, and penetration of the preservative in the permeable portion of wood. Therefore, as a case study, samples of Pinus sp., which could be used as raw material for CLT production, were submitted to testing to identify the penetration and the retention of the preservative. Thus, twenty-one pinewood boards were randomly selected from a timber establishment, and a sample with approximate dimensions of (15 x 15 x 2) cm was cut from each of them. According to the producer, the timber was from the south region of Brazil and was treated with CCB. Retention of the preservative was determined using an atomic absorption spectrophotometer and penetration, by means of a colorimetric test, as described in the ABNT NBR 6232:2013 (ABNT, 2013a) standard. To determine penetration, the blue color in the tested samples indicates the presence of the preservative, according to the following classification: NP – non-penetration of the preservative; IP - irregular penetration; TP - total penetration in the permeable portion of the wood. Table 1 shows the results of the tested parameters (penetration and retention) in the samples of Pinus sp. Figure 4 illustrates the penetration tests.
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Table 3. Results of the penetration and retention tests. Sample
Retention (kg/m³)
Penetration
1338
2,8
TP
1339
1,5
IP
1340
2,7
IP
1341
2,9
TP
1342
3,0
TP
1343
3,0
TP
1387
4,5
TP
1389
3,8
IP
1394
3,4
TP
1395
5,4
TP
1396
2,7
TP
1397
4,3
TP
1399
2,3
IP
1402
4,3
IP
1403
2,6
IP
1405
4,5
TP
1406
4,7
TP
1407
5,2
IP
1408
4,1
IP
1412
4,8
IP
1423
4,4
IP
Fig. 4. Example of samples with (a) total penetration of the preservative and (b) irregular penetration of the preservative.
The ABNT NBR 16143 (ABNT, 2013c) standard sets forth that minimum retention for wood used above ground, but exposed to wetting, must be 4 kg/m³. However, 12 (57%) out of the 21 tested samples achieved results bellow that value. Consequently, in case those boards were used for CLT production, the panels could have lower performance than the expected in the prevention of building pathologies originated from biodeterioration processes, thus not achieving the estimated project life. According to the Brazilian standard ABNT NBR 15575 (ABNT, 2013b), the life of building or structural components must be at least 50 years. As for the penetration results, 10 samples (47%) didn’t obtain total penetration. The analyzed standard (ABNT, 2013c) sets forth that the preservative must reach all permeable portion of wood. Pinewood is considered completely permeable, and therefore, able to be treated, since there is no heartwood, which is the portion of wood inaccessible to preservation treatments, even those under pressure. However, despite the irregular penetration of the preservative, in those 10 samples, there was a great amount of treated wood that could protect the structural components against decay. Therefore, the analysis of the tested parameters implies the importance of implementing a quality control system of the CCB-treated wood used for CLT production.
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5. Conclusions Cross Laminated Timber (CLT) panels assembled in tropical climates are more susceptible to building pathologies caused by fungi and xylophagous insects, since in those locations there are more aggressive environmental conditions, related to biodiversity, temperature and humidity, than cold and dry climates. Therefore, the adoption of strategies to protect structural components, such as preservation treatment, is essential to ensure adequate performance and durability of the construction system, which is expected to last for at least 50 years. Three countries with tropical climates and where CLT panels have been frequently used in the past years are the USA, Australia and Brazil. In this paper, their potential for decay was discussed, as well as the preservation treatments standards adopted in each of them. The bigger amount of decay agents considered in the Brazilian preservation standards and the country climate-index map, based on the Scheffer’s index, indicate that there are more favorable conditions for decay to occur in Brazil, than there are in Australia and the USA. Furthermore, a case study was conducted. Samples of CCB-treated pinewood, which could be used as raw material for CLT production in Brazil, were submitted to testing to identify the penetration and the retention of the preservative. The results show insufficient retention and penetration of the preservative in most of the samples. Hence, this case study indicates the importance of a quality control process of the CLT production. Considering that in Brazil the climate conditions are most conductive to decay, CCB-treated wood used in the Brazilian CLT manufacture must be especially verified during the quality control process, in order to certify the adequacy of the preservation treatment parameters according to the standards. Acknowledgements The authors wish to acknowledge CAPES/CNPq for the financial support and Instituto de Pesquisas Tecnológicas do Estado de São Paulo (IPT) for conducting the laboratory tests. References ANSI/APA – The Engineered Wood Association, 2018. Standard for Performance Rated Cross-Laminated Timber PGR 320-2012. Tacoma. Associação Brasileira De Normas Técnicas – ABNT, 2013a. NBR 6232 – Penetração e retenção de preservativos em madeira tratada sob pressão. Rio de Janeiro. Associação Brasileira de Normas Técnicas – ABNT, 2013b. NBR 15575 – Edificações Habitacionais — Desempenho. Rio de Janeiro. Associação Brasileira de Normas Técnicas – ABNT, 2013c. NBR 16143 – Preservação de madeiras – Sistema de categorias de uso. Rio de Janeiro. American Wood Protection Association - AWPA, 2017. Use Category System: User specifications for treated wood (U1-17). Australian Standard - AS, 2012. Specification for preservative treatment. Part 1: Sawn and round timber. Australian Standard AS 1604.1-2012. Standards Australia, Sydney, New South Wales. Carll, C. G. 2009. Decay hazard (Scheffer) index values calculated from 1971–2000 climate normal data. General Technical Report FPL-GTR-179. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, pp. 17. Foliente, G. C.; Leicester, R. H.; Cole, I.; Mackenzie, C., 1999. Development of a reliability-based durability design method for timber construction. In: Lacasse, M.A. and Vanier, D.J. (Ed.), Proc 8th International Conf. on Durability of Building Materials and Components. NRC Research Press, Ottawa, v. 2, 1289−1298. Lelis, A. T.; Brazolin, S.; Fernandes, J. L. G.; Lopez, G. A. C.; Monteiro, M. B. B.; Zenid, G. J., 2001. Biodeterioração de madeiras em edificações. Instituto de Pesquisas Tecnológicas do Estado de São Paulo - IPT, São Paulo. Martins, V. A.; Alves, M. V.; Silva, J. F. S.; Rebello, E. R. G.; Pinho, G. S. C. de, 2003. Umidade de equilíbrio e risco de apodrecimento da madeira em condições de serviço no Brasil. Brasil Florestal, v. 22, n. 76, 29-34. Milano, S; Fontes, L.C., 2002. Cupim e cidade: implicações ecológicas e controle. Conquista Artes Gráficas, São Paulo, pp. 141. Morrell, J. J., 2006. Chromate Copper Arsenate as a Wood Preservative. In: Environmental Impacts of Treated Wood, T.G. Townsend and H. SoloGabriele (Ed.). CRC Press, Boca Raton, 5-17. Oliveira, A. M. F.; Lelis, A. T. de; Lepage, E. S.; Lopez, G. A. C.; Oliveira, L. C. S. de; Cañedo, M. D.; Milano, S., 1986. Agentes destruidores da madeira. In: Lepage, E. S. (Coord.). Manual de preservação de madeiras. Instituto de Pesquisas Tecnológicas do Estado de São Paulo - IPT, São Paulo, v. 1, cap. 5, 99-278. Scheffer, T. C., 1971. A climate index for estimating potential for decay in wood structures above ground. Forest Products Journal, v. 21 n. 10. West, D. C., 2004. Health Effects of Preserved Wood: Relationship Between CCA-Treated Wood and Incidence of Cancer in the United States. Conference Paper from Environmental Impacts of Preservative -Treated Wood Conference, Orlando, Florida.
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Structural Integrity Procedia 00 (2018) 000–000 Available online www.sciencedirect.com Available online at at www.sciencedirect.com Structural Integrity Procedia 00 (2018) 000–000
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Procedia Structural Structural IntegrityIntegrity Procedia1100(2018) (2016)242–249 000–000
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XIV International Conference on Building Pathology and Constructions Repair – CINPAR 2018 XIV International Conference on Building Pathology and Constructions Repair – CINPAR 2018
Wood preservation for preventing biodeterioration of Cross Wood preservation for preventing biodeterioration of Cross Laminated Timber (CLT) panels assembled in tropical XV Portuguese Conference Fracture, PCF 2016, 10-12 February 2016, Paço locations de Arcos, Portugal Laminated Timber on (CLT) panels assembled in tropical locations a b c Gabriela Lotufo Oliveira *, Fabiana Lopes de Oliveira , Sérgio Brazolin Thermo-mechanical modeling of a high pressure turbine blade a b Gabriela Lotufo Oliveira *, Fabiana Lopes de Oliveira , Sérgio Brazolinc of an Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo, Rua do Lago, 876, São Paulo, Brazil airplane gas turbine engine Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo,Prado, Rua do532, Lago, SãoBrazil Paulo, Brazil Instituto de Pesquisas Tecnológicas (IPT), Av. Prof. Almeida São876, Paulo, a, b a, b
c c
Instituto de Pesquisas Tecnológicas (IPT), Av. Prof. Almeida Prado, 532, São Paulo, Brazil
P. Brandãoa, V. Infanteb, A.M. Deusc*
AbstractaDepartment of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal Abstract b Department Mechanical Técnico, Universidade Lisboa,panels. Av. Rovisco Pais, 1, 1049-001 Lisboa, CrossIDMEC, Laminated Timberof (CLT) is a Engineering, constructionInstituto systemSuperior based on pre-fabricated soliddewood As this system is produced Portugal Cross Timberits(CLT) is a construction system based pre-fabricated solid wood panels. As this system is processes produced with naturalDepartment material, implementation is associated theon adoption of preventive c a Laminated CeFEMA, of Mechanical Engineering, Institutowith Superior Técnico, Universidade de measures Lisboa, Av.against Roviscopathological Pais, 1, 1049-001 Lisboa, with a natural material, itsbiodeterioration. implementation is associated with the adoption of as preventive measures against pathological intrinsic to wood, such as This phenomenon can be defined undesirable changes in wood elements processes provoked Portugal intrinsic wood, such biodeterioration. This phenomenon can be such defined as undesirable changes provoked by livingtoorganisms thatasuse wood as food supply. Microorganisms, as fungi, and insects, such in as wood termiteelements and wood-boring by livingareorganisms that use wood asTheir food supply. Microorganisms, such as fungi, and insects, such as termite and wood-boring beetles among these organisms. developments occur under favorable moisture and temperature circumstances; thus, beetles are among are these organisms. Their occur under favorable moisture and temperature circumstances; thus, climate conditions important factors fordevelopments the wood structure durability. The use of CLT panels in tropical climates must be Abstract climate conditions arepreservation important factors fortotheavoid wood structure use of CLT tropical climates must be associated with wood methods decay of thedurability. structural The components. Thispanels paper in aims to discuss preservation associated with wood preservation methods to avoid components decay of thethe structural components. This paper aims towhere discuss preservation During applied their operation, modern aircraftlocations, engine are subjected to increasingly demanding operating conditions, treatment to CLT panels in tropical comparing standards adopted in different countries CLT buildings especially the high pressure turbine (HPT) blades. Hence, Such conditions cause these parts in to different undergo different types ofCLT time-dependent treatment applied to CLT panels in tropical locations, comparing the standards adopted countries whereand buildings are used. Additionally, a case study was conducted. samples of Pinus sp. from the south region of Brazil treated with degradation, one of which creep.solution) A model using the finite element method was developed, order toand be able to predict are used. Additionally, a case study was conducted. Hence, of Pinus sp.(FEM) from region of Brazil treated with CCB (copper, chromium andisboron were tested to samples identify the penetration andthe thesouth retention ofin the preservation product. thetests creep behaviour ofand HPT blades. Flight data records (FDR) for a 6232:2013. specificand aircraft, provided by preservation athat commercial aviation CCB (copper, chromium boron solution) were tested to identify the penetration the retention of the product. The followed the method suggested by Brazilian standard ABNT NBR The results showed it is necessary to company, werecontrol used to obtain thermal mechanical dataABNT forwood three different flight cycles. orderorganisms. tothat create the 3D model The tests quality followed the method suggested byand Brazilian NBR 6232:2013. The resultsInshowed it is necessary to establish to avoid CLT production withstandard no adequate protection against xylophagous neededquality for thecontrol FEM to analysis, a HPT blade scrap wasadequate scanned, andprotection its chemical composition and organisms. material properties were establish avoid CLT production with no wood against xylophagous obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D Copyright © 2018 Elsevier B.V. All rights reserved. Copyright © 2018 Elsevier B.V. All rights reserved. rectangular block shape, in order torights better establish the model, and then with the real 3D mesh obtained from the blade scrap. The Copyright ©under 2018 Elsevier B.V. All reserved. Peer-review responsibility of CINPAR the CINPAR 2018 organizers Peer-review under responsibility 2018 organizers overall expected behaviour of in the terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a Peer-review under responsibility of the CINPAR 2018 organizers model can be useful in the goal of predicting turbine blade life, given a set of FDR data. Keywords: Cross Laminated Timber (CLT); wood structures; biodeterioration; preservation treatment. Keywords: Cross Laminated Timber (CLT); wood structures; biodeterioration; preservation treatment.
© 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016.
Keywords: High Pressure Turbine Blade; Creep; Finite Element Method; 3D Model; Simulation.
* Corresponding author. Tel.: +55 11 30914539 * Corresponding Tel.: +55 11 30914539 E-mail address:author. [email protected] E-mail address: [email protected] 2452-3216 Copyright © 2018 Elsevier B.V. All rights reserved. 2452-3216 Copyright © 2018 Elsevier All rights Peer-review under responsibility of the B.V. CINPAR 2018 reserved. organizers. Peer-review under responsibility of the218419991. CINPAR 2018 organizers. * Corresponding author. Tel.: +351 E-mail address: [email protected] 2452-3216 © 2016 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the Scientific Committee of PCF 2016. 2452-3216 Copyright 2018 Elsevier B.V. All rights reserved. Peer-review under responsibility of the CINPAR 2018 organizers 10.1016/j.prostr.2018.11.032
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1. Introduction According to ANSI/APA 320 (2018), Cross Laminated Timber (CLT) panels are a prefabricated engineered wood product, made of at least three orthogonal sawn lumber layers. The panels have been developed first in Austria during the 1990’s. Currently, the product is well established in Europe and, over the last years, its use has increased in other continents, such as North America and Oceania. In South America, the panel production started in Brazil in 2012. Some of the countries where CLT has recently been implemented have tropical climates, with high temperatures and humidity. Consequently, wood structural components located in those regions are more susceptible to building pathologies caused by biodeterioration, than they are in dry or cold climates (Scheffer, 1971). Wood is susceptible to both abiotic (chemicals, fire and sunlight damage, for example) and biotic deterioration agents (Morrell, 2006). Biotic agents are living organisms that use wood as food supply, provoking undesirable changes in wood elements. Microorganisms, as fungi and bacteria, insects, such as termite and wood-boring beetles, and marine borers are among these organisms. Nearly all decay biotic agents require oxygen. Another factor necessary for the phenomenon is adequate temperatures. Although organisms have a variety of temperature requirements, the perfect range temperature for their survival is from 5°C to 40°C (Morrell, 2006). Furthermore, for decay caused by microorganisms to occur, the wood moisture content must be higher than the fiber saturation point, which is around 30%. When this level is reached, free water present in wood enables the transportation of the enzymes produced by the microorganisms to the wood cell polymers, among other purposes. The enzymes are responsible for decomposing those polymers and the molecules resulting from this process are transported back to the microorganism through water (Oliveira et al, 1986). Consequently, most organisms are unable to cause damage once the wood moisture content drops below 30%. In a tropical country, the occurrence of termites and beetles in wood buildings and heritage is significant. The termites are the main problem with native and exotic species (Oliveira, et al, 1986). Milano and Fontes (2002) estimated losses at US$ 10,000 per year for treatments, repairs and replacements of deteriorated wood components. However, some wood species have natural resistance, since they produce chemicals that inhibit or are toxic to xylophagous organisms. As for the species that do not produce those extractives, and therefore have low natural resistance, one of the remaining strategies to protect them is the preservation treatment. Preservation treatments improve wood resistance, by means of impregnation of chemicals that are toxic to decay agents (Lelis et al, 2001). Those treatments strongly increase the useful life of a wood product by 20 to 40 times that of untreated wood (Morrell et al, 2006). Since CLT panels are mostly produced of softwoods, whose natural resistance to deterioration is low, their use in tropical locations, such as Brazil, Australia and some parts of the USA, must be associated to preservation methods to avoid the decay of the structural components. Therefore, this paper aims to discuss preservation treatment used in the mentioned countries, where CLT buildings have recently been assembled, by comparing the standards adopted in each one. Additionally, a case study was conducted. Hence, samples of pinewood from the south region of Brazil and treated with CCB (copper, chromium and boron solution) were tested to identify the penetration and retention of the preservative. 2. Potential wood decay in tropical climates Considering the influence of climate conditions on the wood biodeterioration process, Scheffer (1971) developed a climate index to estimate potential for decay in wood structures above ground, in order to evaluate the need for protective measures. The climate index value proposed by Scheffer is calculated from local weather data by the following equation: ���.
Climte index = �
���.
[(� − 2)(� − 3)] 16,7
(1)
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Where: T is the average monthly temperature (°C) D is the average number of days in the month with 0,25 mm precipitation or more The author calculated the climate index value for the metropolitan areas of the USA, resulting in a climate index map of the country, divided in three index zones that represent three levels of above ground decay. Figure 1 shows the map of the USA reproduced in the Wood Handbook (Forest Products Laboratory, 1999, apud Carll, 2009, p.2) and based on the index proposed by Scheffer.
Fig. 1. Scheffer´s climate-index map of the USA.
According to Scheffer, in areas from the map with index values of less than 35, there are the least favorable conditions for decay; in those with values between 35 and 70, there are intermediately favorable conditions; in the ones with values greater than 70, there are the most conductive conditions to decay (Scheffer, 1971). Decay hazard maps based on Scheffer’s index have also been developed for Brazil and Australia, by Martins et al. (2003) and Carter et al. (1993, apud Foliente, 1999, p.1293), respectively, and are shown on Figure 2 and Figure 3.
Fig. 2. Brazilian´s climate-index map, based on Scheffer´s index.
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Fig. 3. Australian´s climate-index map, based on Scheffer´s index.
Comparing the three maps, it´s possible to see that in all studied countries, there are regions with climate conditions most favorable for decay to occur. However, as pointed by Martins et al. (2003), in all Brazilian regions, with just a few exceptions, there are the most conductive conditions to decay, since the index values are higher than 70 in most of the country area. Therefore, it can be concluded that from the three countries above, Brazil is the one with the highest potential for decay to occur. 3. Wood preservation The modern age of wood preservation started with the patenting of Creosote, as a wood preserver, and with advent of the full cell process for delivering that product into wood, back at the 1830s. Creosote was for a long time the most effective of all treatment systems available (Morrell, 2006). This oil-based preservative was mainly used for poles, crossties and posts, not recommended for buildings, considering its odor and oil exudation. In the 1930s, two important new systems were developed, Pentachlorophenol and CCA (Chromate Copper Arsenate). Pentachlorophenol was an oil-based material that emerged as a substitute to Creosote and CCA was a mixture of copper, chromium and arsenic - metals dissolved in water. Cooper is a highly effective fungicide and arsenic is an insecticide; chromium reacts with both promoting their fixation in the wood, avoiding their leaching to the environment. Until the 2000s, CCA was the most important chemical used to protect wood (Morrell, 2006). However, in the USA, around the beginning of the 2000s, there was a growing concern about the health effects associated with exposure to CCA preserved wood due to arsenate. The greatest concern was the risk of developing some types of cancer later in life (West, 2004). Therefore, on December 31, 2003, the Environmental Protection Agency (EPA) and the lumber industry of the United States decided to withdraw the registration of CCA for residential use (Morrell, 2006), such as playgrounds, decks and picnic tables, voluntary; thus, avoiding direct contact with people. Nevertheless, CCA-treated wood is still used for commercial and industrial purposes. In this scenario, other chemicals were developed to replace arsenate-based products. One of them is a mixture of copper, chromium and boron (CCB), diluted in water, which has been first commercialized in Germany at the beginning of the 1960s (Oliveira et al., 1986). In this chemical, boron is effective against insects, functioning as an arsenate substitute. In Brazil, CCB is frequently used for construction, although there is no governmental restriction to use CCA. To regulate the use of those chemicals, in most countries, there are wood treatment specifications. In the USA, the American Wood Protection Association (AWPA), founded in 1904, standardizes treatment processes and develops standards for wood preservatives and treatments for different degrees of risk of decay, which are divided in use categories (Morrell, 2006), considering the biological use conditions and the presence of xylophagous organisms (AWPA, 2017). As shown in Table 1, the first category (UC1) represents the lowest risk and the last category (UC5), the highest.
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Table 1. American Use Categories. Use Category
Service Conditions
Deterioration Agents
UC1
interior construction
insects only
above ground dry UC2
interior construction
decay fungi and insects
above ground damp UC3A
exterior construction
decay fungi and insects
above ground coated & rapid water runoff UC3B
exterior construction
decay fungi and insects
above ground uncoated or poor water runoff UC4A
ground contact or fresh water
decay fungi and insects
non-critical components UC4B
ground contact or fresh water critical components or difficult replacement
UC4C
ground contact or fresh water critical structural components
decay fungi and insects with increased potential for biodeterioration decay fungi and insects with extreme potential for biodeterioration
UC5A
salt or brackish water and adjacent mud zone which includes Long Island, NY and northward, north of San Francisco
salt water organisms
UC5B
salt or brackish water and adjacent mud zone south of Long Island, NY to the southern border of GA, south of San Francisco
salt water organisms including creosote tolerant Limnoria tripunctata
UC5C
salt or brackish water and adjacent mud zone South of GA, Gulf Coast Hawaii and Puerto Rico
salt water organisms including Martesia, Sphaeroma
In Australia, standard AS 1604– Specification for preservative treatment (AS, 2012) defines that any preservative treated product must be branded, indicating, among other characteristics, the Hazard Class this product can be exposed to, likewise the American Use Categories. The Australian Hazard Classes are six totally, as shown in Table 2.
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Table 2. Australian Use Categories. Use Category
Service Conditions
Deterioration Agents
H1
completely protected from the weather, well ventilated and protected from termites
borers
H2
protected from wetting, no leaching
borers and termites
H3
periodic moderate wetting and leaching
moderate decay, borers and termite
H4
severe wetting and leaching non-critical applications
severe decay, borers and termites
H5
extreme wetting and leaching, critical application
very severe decay, borers and termites
H6
prolonged immersion in sea water
marine wood borers
In Brazil, standard ABNT NBR 16143:2013 – Preservação de madeiras – Sistema de categorias de uso (ABNT, 2013c), presents six categories based on the exposure of the wood component, similarly to those from Australia. The main difference between the Brazilian and Australian Use Categories is that the first one considers three types of termites and three types of fungi. One of the types of termite is also a possible deterioration agent in the first Use Category. The bigger amount of decay agents considered in the Brazilian preservation standards indicates more favorable conditions for decay to occur in this country, as Scheffer’s climate index. However, just four preservatives are registered for pressure treatment of wood in Brazil (Creosote, CCA, CCB and CA-B (Copper Azole Type B)). In the USA, more than twenty preservatives are standardized by ASTM. Creosote, CCA-C, Alkaline Copper Quaternary Type A (ACQ-A), pentachlorophenol, CA-B, Ammoniacal Copper Zinc Arsenate (ACZA) and many others are among them. As for Australia, the registered preservatives are: CCA, ACQ, Copper Azole (CA), Creosote and Boron. One of the explanations for that occurrence is the minor use of wood as structural component in the Brazilian construction sector, mostly for cultural reasons. 4. Case study: CLT treated with CCB in Brazil The use of CLT, made of pinewood, has recently begun in Brazil, typically for high-standard residences. The Brazilian use category system standard (ABNT, 2013c) establishes the need of quality control, measuring two parameters for pressure treatment: retention, or the quantity of active ingredient introduced into the dry wood (below 30%), expressed as kg/m³, and penetration of the preservative in the permeable portion of wood. Therefore, as a case study, samples of Pinus sp., which could be used as raw material for CLT production, were submitted to testing to identify the penetration and the retention of the preservative. Thus, twenty-one pinewood boards were randomly selected from a timber establishment, and a sample with approximate dimensions of (15 x 15 x 2) cm was cut from each of them. According to the producer, the timber was from the south region of Brazil and was treated with CCB. Retention of the preservative was determined using an atomic absorption spectrophotometer and penetration, by means of a colorimetric test, as described in the ABNT NBR 6232:2013 (ABNT, 2013a) standard. To determine penetration, the blue color in the tested samples indicates the presence of the preservative, according to the following classification: NP – non-penetration of the preservative; IP - irregular penetration; TP - total penetration in the permeable portion of the wood. Table 1 shows the results of the tested parameters (penetration and retention) in the samples of Pinus sp. Figure 4 illustrates the penetration tests.
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Table 3. Results of the penetration and retention tests. Sample
Retention (kg/m³)
Penetration
1338
2,8
TP
1339
1,5
IP
1340
2,7
IP
1341
2,9
TP
1342
3,0
TP
1343
3,0
TP
1387
4,5
TP
1389
3,8
IP
1394
3,4
TP
1395
5,4
TP
1396
2,7
TP
1397
4,3
TP
1399
2,3
IP
1402
4,3
IP
1403
2,6
IP
1405
4,5
TP
1406
4,7
TP
1407
5,2
IP
1408
4,1
IP
1412
4,8
IP
1423
4,4
IP
Fig. 4. Example of samples with (a) total penetration of the preservative and (b) irregular penetration of the preservative.
The ABNT NBR 16143 (ABNT, 2013c) standard sets forth that minimum retention for wood used above ground, but exposed to wetting, must be 4 kg/m³. However, 12 (57%) out of the 21 tested samples achieved results bellow that value. Consequently, in case those boards were used for CLT production, the panels could have lower performance than the expected in the prevention of building pathologies originated from biodeterioration processes, thus not achieving the estimated project life. According to the Brazilian standard ABNT NBR 15575 (ABNT, 2013b), the life of building or structural components must be at least 50 years. As for the penetration results, 10 samples (47%) didn’t obtain total penetration. The analyzed standard (ABNT, 2013c) sets forth that the preservative must reach all permeable portion of wood. Pinewood is considered completely permeable, and therefore, able to be treated, since there is no heartwood, which is the portion of wood inaccessible to preservation treatments, even those under pressure. However, despite the irregular penetration of the preservative, in those 10 samples, there was a great amount of treated wood that could protect the structural components against decay. Therefore, the analysis of the tested parameters implies the importance of implementing a quality control system of the CCB-treated wood used for CLT production.
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5. Conclusions Cross Laminated Timber (CLT) panels assembled in tropical climates are more susceptible to building pathologies caused by fungi and xylophagous insects, since in those locations there are more aggressive environmental conditions, related to biodiversity, temperature and humidity, than cold and dry climates. Therefore, the adoption of strategies to protect structural components, such as preservation treatment, is essential to ensure adequate performance and durability of the construction system, which is expected to last for at least 50 years. Three countries with tropical climates and where CLT panels have been frequently used in the past years are the USA, Australia and Brazil. In this paper, their potential for decay was discussed, as well as the preservation treatments standards adopted in each of them. The bigger amount of decay agents considered in the Brazilian preservation standards and the country climate-index map, based on the Scheffer’s index, indicate that there are more favorable conditions for decay to occur in Brazil, than there are in Australia and the USA. Furthermore, a case study was conducted. Samples of CCB-treated pinewood, which could be used as raw material for CLT production in Brazil, were submitted to testing to identify the penetration and the retention of the preservative. The results show insufficient retention and penetration of the preservative in most of the samples. Hence, this case study indicates the importance of a quality control process of the CLT production. Considering that in Brazil the climate conditions are most conductive to decay, CCB-treated wood used in the Brazilian CLT manufacture must be especially verified during the quality control process, in order to certify the adequacy of the preservation treatment parameters according to the standards. Acknowledgements The authors wish to acknowledge CAPES/CNPq for the financial support and Instituto de Pesquisas Tecnológicas do Estado de São Paulo (IPT) for conducting the laboratory tests. References ANSI/APA – The Engineered Wood Association, 2018. Standard for Performance Rated Cross-Laminated Timber PGR 320-2012. Tacoma. Associação Brasileira De Normas Técnicas – ABNT, 2013a. NBR 6232 – Penetração e retenção de preservativos em madeira tratada sob pressão. Rio de Janeiro. Associação Brasileira de Normas Técnicas – ABNT, 2013b. NBR 15575 – Edificações Habitacionais — Desempenho. Rio de Janeiro. Associação Brasileira de Normas Técnicas – ABNT, 2013c. NBR 16143 – Preservação de madeiras – Sistema de categorias de uso. Rio de Janeiro. American Wood Protection Association - AWPA, 2017. Use Category System: User specifications for treated wood (U1-17). Australian Standard - AS, 2012. Specification for preservative treatment. Part 1: Sawn and round timber. Australian Standard AS 1604.1-2012. Standards Australia, Sydney, New South Wales. Carll, C. G. 2009. Decay hazard (Scheffer) index values calculated from 1971–2000 climate normal data. General Technical Report FPL-GTR-179. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, pp. 17. Foliente, G. C.; Leicester, R. H.; Cole, I.; Mackenzie, C., 1999. Development of a reliability-based durability design method for timber construction. In: Lacasse, M.A. and Vanier, D.J. (Ed.), Proc 8th International Conf. on Durability of Building Materials and Components. NRC Research Press, Ottawa, v. 2, 1289−1298. Lelis, A. T.; Brazolin, S.; Fernandes, J. L. G.; Lopez, G. A. C.; Monteiro, M. B. B.; Zenid, G. J., 2001. Biodeterioração de madeiras em edificações. Instituto de Pesquisas Tecnológicas do Estado de São Paulo - IPT, São Paulo. Martins, V. A.; Alves, M. V.; Silva, J. F. S.; Rebello, E. R. G.; Pinho, G. S. C. de, 2003. Umidade de equilíbrio e risco de apodrecimento da madeira em condições de serviço no Brasil. Brasil Florestal, v. 22, n. 76, 29-34. Milano, S; Fontes, L.C., 2002. Cupim e cidade: implicações ecológicas e controle. Conquista Artes Gráficas, São Paulo, pp. 141. Morrell, J. J., 2006. Chromate Copper Arsenate as a Wood Preservative. In: Environmental Impacts of Treated Wood, T.G. Townsend and H. SoloGabriele (Ed.). CRC Press, Boca Raton, 5-17. Oliveira, A. M. F.; Lelis, A. T. de; Lepage, E. S.; Lopez, G. A. C.; Oliveira, L. C. S. de; Cañedo, M. D.; Milano, S., 1986. Agentes destruidores da madeira. In: Lepage, E. S. (Coord.). Manual de preservação de madeiras. Instituto de Pesquisas Tecnológicas do Estado de São Paulo - IPT, São Paulo, v. 1, cap. 5, 99-278. Scheffer, T. C., 1971. A climate index for estimating potential for decay in wood structures above ground. Forest Products Journal, v. 21 n. 10. West, D. C., 2004. Health Effects of Preserved Wood: Relationship Between CCA-Treated Wood and Incidence of Cancer in the United States. Conference Paper from Environmental Impacts of Preservative -Treated Wood Conference, Orlando, Florida.