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Evaluation of new creosote formulations after extended exposures in fungal cellar tests and field plot tests
2000 - IRG/WP 00-30228
Although creosote, or coal tar creosote, has been the choice of preservative treatment for the railroad industry since the 1920s, exuding or "bleeding" on the surface of creosote-treated products has been one incentive for further enhancements in creosote production and utility (Crawford et al., 2000). To minimize this exuding problem, laboratories such as Koppers Industries Inc., USA, and Commonwealth Scientific and Industrial Research Organization (CSIRO), Division of Chemical and Wood Technology, Melbourne, Australia, have developed changes in processing of coal tar that produce distillates with fewer contaminants. This "clean distillate" is then used to formulate "clean creosote" as a preservative. These new, unique creosote formulations are being investigated as part of a program to enhance the use of regionally important wood species in the United States. Four retention levels of each of two new creosote formulations creosote, one pigment-emulsified creosote (PEC) and one creosote formulation that meets the AWPA Standard C2-95 for P1/P13 creosote (AWPA, 1995a), were applied to two softwood species and two hardwood species. Two laboratory procedures, the soil-block and fungal cellar tests (accelerated field simulator), were used to evaluate the four creosote formulations. These procedures characterized the effectiveness of the wood preservatives. The soil-block tests were used to determine the minimum threshold level of the preservative necessary to inhibit decay by pure cultures of decay fungi. In general, the soil block tests showed there was little difference in the ability of the four creosote formulations to prevent decay at the three highest retention levels as summarized in a previous report by Crawford and DeGroot (1996). The soil-block tests will not be discussed in this report. Fungal cellar tests expose treated wood to mixtures of soil-borne fungi that promote accelerated attack. Crawford and DeGroot (1996) discussed the evaluation of the creosote formulations after 17 months of exposure in the USDA Forest Service, Forest Products Laboratory (FPL), fungal cellar. At that point in time data from the fungal cellar tests showed that softwoods are protected better than hardwoods for all four formulations of creosote tested. This report will discuss exposure of the fungal cellar stakes upto 36 months. In addition, field stake tests are being used to verify service life of the new creosote formulations in vivo. Results from accelerated tests are indicative of field performance, but the correlation between laboratory and field results is still being investigated. Field stake tests are regarded as critical, long-term evaluations that provide results most directly related to the performance of treated products in service. In this study, we report on the performance of the creosote formulations after five years of exposure in field tests.
D M Crawford, P K Lebow, R C De Groot

Developments in wood preservation
1978 - IRG/WP 3121
The purpose of this paper is to comment very briefly upon recent developments and trends in wood preservation so that members of this Working Group have a basic knowledge of activities in other countries. The last paper was prepared in September 1977 and the present paper refers to developments since that time.
B A Richardson

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

Prevention of creosote bleeding from treated Scots pine poles
1970 - IRG/WP III 3B
Creosote, the most widely used preservative for pressure treatment of Electricity Board and GPO transmission poles in the United Kingdom has, when correctly applied, given good performance over a long period of time. Perhaps its only disadvantage as a preservative in the above fields is its tendency to exude or 'bleed' from a proportion of treated poles upon exposure to solar heat. This causes the poles to become oily making them difficult to handle during erection and maintenance and occasionally it causes annoyance to the general public who can soil clothes by brushing against such poles.

Temperature and pressure inside wood during creosote impregnation
1991 - IRG/WP 3649
Creosote gives the best protection against decay for sleepers and poles. However, it has a major drawback - bleeding. Modified impregnation processes to reduce bleeding have been tried. For developing such processes it is important to know the actual temperature and pressure inside the wood. This paper describes measurement of temperature and pressure inside wood during creosote impregnation. The experiments have been performed at a research plant using poles of Scots pine (Pinus sylvestris L.). Boiling under vacuum before impregnation increased the temperature inside the sapwood to 80-90°C within 1½ hours. The pre-pressure of the Rueping process applied in the vessel raised the pressure inside the sapwood immediately to the same level as in the vessel. When the oil-pressure was applied the pressure inside the wood rose more slowly and generally did not reach the level in the vessel. During the final vacuum there was still pressure above atmospheric inside the wood in most of the experiment charges.
Ö Bergman

Influence of different treatment parameters on penetration, retention and bleeding of creosote
2003 - IRG/WP 03-40255
Creosote is an extensively used preservative for transmission poles and sleepers. The purpose of this research was to investigate the treatment parameters necessary to achieve full sapwood penetration and minimum required retention and to avoid bleeding of creosote. It was carried out as a part of the European research project WOODPOLE. Transmission poles of Scots pine (Pinus sylvestris L.) previously air-dried under a roof, were creosote treated in a research plant. Before treatment each pole was cut into three pieces (logs). Each pole made a charge. The creosotes WEI type B and type C were used. A number of treatment processes were carried out using five poles per process. Different levels of pre-pressure and oil pressure were used as well as different duration of oil pressure. Heating of the logs in creosote before pre-pressure and after oil pressure was carried out for one or three hours. Retention was measured by weighing before and after treatment and by analysis. Processes with no or only a short period of heating before pre-pressure and after oil pressure showed most bleeding. Poles and stakes with different levels of retention were produced for field trials.
Ö Bergman

The influence of different creosote process parameters on penetration, retention and bleeding on glulam
2007 - IRG/WP 07-40368
Different process parameters were used to treat Scots Pine glulam beams with creosote. Parameters like pre-heating, pre-pressure time, pressure and pressure time were changed. Most treatments gave a full or almost full penetration of creosote into the sapwood, but the uptake of creosote in the sapwood varies. All samples, except the one with poor penetration, showed heavily bleeding of creosote for about a year before the creosote hardened. To get a good protection of the glulam without bleeding, it has to be double-treated. The lamellae have to be copper impregnated before gluing and the beam must then be treated with a creosote process as C (short pressure time) in part 1. The inner sapwood that will be untreated with creosote will then be protected by the Cu-preservative.
F G Evans

Development of methodologies to evaluate tanning blocking coatings
2016 - IRG/WP 16-40760
In Europe an increased interest in using home-grown hardwoods as sustainable and renewable construction materials started a few years ago. Amongst these species oak and chestnut are two interesting candidates as their heartwood contain a significant amount of tannins which contribute to their natural durability. To avoid wood greying and dimensional variations, oak and chestnut must be protected by coatings. The European VOC Directive has been the driving force behind the change from solvent borne to waterborne coatings. Therefore bleeding of water- soluble tannins can be observed during the coating application. This phenomenon may also occur during service life due to humidity and rainfall, leading to some ungraceful aesthetic aspect for the construction. Manufacturers have therefore developed specific coatings to control tannin-staining. Moreover due to the specific anatomy of oak and chestnut (large vessels), coatings need also to be flexible enough to cover the irregular surface of these woods. In Europe a standardized test method to assess the performance of these coatings is not yet available. Each manufacturer has developed anti-bleeding coatings using its own tests. It is then difficult to compare objectively the performance of the different products available on the market and to advise the manufacturers for possible improvement of their coatings. This paper describes the advantages and drawbacks of some methods used to qualify different coatings available on the market. Permeability to liquid water and immersion tests are suitable and easy methods to provide evidence of the performance of anti-tanning staining coatings. These methods give information regarding the barrier properties to tannin bleeding and the capability of the coating not to be discoloured.
C Reynaud, L Podgorski

Review on protection of timber bridges in Norway and other countries
2017 - IRG/WP 17-40809
Wood plays a major role in design and construction of modern bridges in Norway. Typical elements of those bridges are double impregnated glued laminated members, stress laminated timber decks, slotted-in steel plates, metal cladding of the surfaces of loadbearing members, and cross girders made of steel. Selected examples of timber bridges in Norway are presented. This review paper gives an overview of the importance of timber bridges in Norway, Sweden, Finland, Germany, Switzerland and the USA. The literature in the fields of protection by design, preservative treatment, monitoring and inspection of timber bridges is summarized. In the light of the potential ban of creosote as wood preservative, protection by design is crucial for modern timber bridges in Europe. The basic principles of protection by design are outlined, and an overview of approaches to find alternatives for creosote and the application of modified wood as material for timber bridges is given. Monitoring and inspection are essential to investigate the performance of a timber bridge and to gather data for life cycle estimation. The importance of monitoring the moisture content in bridge structures is pointed out, and an overview of techniques and tools for destructive and non-destructive inspection of timber bridges is presented.
K-C Mahnert, U Hundhausen