Railway ties

Creosote oils are by far the most widely used timber preservatives (see Wood). This use dates back to 1850. Eor the treatment of railway ties and marine pilings, the BetheU or fliU-ceU process is preferred. The timber to be treated is charged to a pressure cylinder, which is evacuated to extract the air from the wood ceUs. The cylinder is then filled with hot creosote and the pressure increased to 0.8—1 MPa (ca 8—10 atm) to force the oil into the ceUs. 

Located on the outskirts of big cities, coal gas factories produced enormous amounts of pollutants, particularly ammonia-rich water and coal tar. Some of the coal tar was used to make pitch to waterproof ships, roofs, and rope. Some was turned into creosote for preserving wooden railway ties, used by the millions during the railroad boom of the 1840s. But Europe did not have enough roofs, ships, and railroads to absorb all the coal tar that was being produced, so most of it was dumped, often into rivers. Hofmann was eager to learn more about its composition and find uses for it. 

The wood industry is the major consumer of technical chloro-phenols. In the United States and in Canada it has been assumed that more than Q0% of pentachlorophenol (PCP) is used for wood perservation and wood protection (38,5jJ. PCP dissolved in various solvents (mineral spirits, fuel oil, kerosene and methylene chloride), is the major compound used for wood perservation. This procedure involves the use of pressure and vacuum cycles to obtain deep and optimum retention of the perservative. This process is used to produce a product which will have a long period of service such as railway ties, pilings and hydropoles. 

Up to 47 mg/kg of CP-transformation products such as o- and />-hydroxylated phenols (Knuutinen et al., 1990), as well as chloroanisoles such as 2,3,4,6-TeCA and PCA (Palm et al., 1991), have often been found in CP-contaminated soils. An additional route for contamination is the CP-treated utility poles and railway ties that contaminate nearby environments via runoff and leaching (Wan, 1992). 

Utility telecommunication and railway right-of-ways may be contaminated by leaching of CDDs associated with chlorophenol-treated railway ties and utility poles. A study in British Columbia showed that CDDs and CDFs were not detected in parkland ditch water (control area), but were detected in farmland, utility, and railway right-of-way ditch water (Wan and van Oostdam 1995). Total mean CDD concentrations (mainly OCDD and HpCDD) measured in farm ditch water, and railway ditch water, without and with utility poles were 2.22 g/L, 45 g/L, and 9,627 g/L respectively. Mean total concentrations of CDDs were much higher in ditch water adjacent to utility poles (13,142 ng/L) than in ditch water 4 meters downstream (4,880 ng/L) or 4 meters upstream of the utility poles (2.72 ng/L). 

The authors concluded that utility poles and railway ties are a potential constant source of CDD/CDF contamination to both water and sediment in aquatic environment through ditch runoff. 

A most effective way to extend the Nation s timber supply is to use wood so that its service life is increased. The service life of wood in hazardous use conditions can be increased severalfold by the proper use of wood preservatives. It is estimated that the preservative treatment of railway ties results in an annual savings of 2.4 billion board feet of lumber and that, if utility poles were not treated, an additional 20 million mature trees of pole-stock quality softwoods would be needed each year simply as replacements for those destroyed by decay and termites. 

In Canada, the main use of PCP is in the protection and preservation of wood, and secondarily as an herbicide and insecticide for agricultural purposes. A total of 50 wood preserving plants - mostly in British Columbia, Alberta, and Ontario - used about 2.7 million kg of PCP in 1978. Treatment with PCP significantly increased the life of timbers, constmc-tion lumber, telephone poles, and railway ties for example, jackpine poles treated with PCP lasted at least 35 years, compared to 7 years for untreated poles. 

Another EPIC report looked at the potential for use of plastics in railway ties. Plastic raihoad ties were reported to be superior in weather and abrasion resistance." ... 

Spot tests can be applied to investigate the nature of the chemicals used in the preservation of timber (telegraph poles, powerline towers, railway ties, etc.). The mineral salts most commonly used are mercuric chloride, copper sulfate, zinc chloride, sodium fluoride. 

Several cases of distress of concrete railway ties have been reported. Examination of cracks in such concretes has revealed that they were filled with secondary products. Ettringite was a prominent constituent, accompanied by CH, CaCOj, and alkali-silica gel. DTA data indicated the presence of a substantial amount of secondary ettringite in many samples but petrographic and XRD did not reveal any ettringite.t ] Thermograms were used to quantitatively estimate the amounts of ettringite formed in failed samples. 

Jack pine is one of the most important commercial tree species in Canada and the Lake States of USA. Its wood is moderately hard and heavy, and relative to other softwoods, of intermediate strength (Eyre and LeBarron, 1944 Hosie, 1979). It can produce merchantable stands on sites often too poor and infertile for other tree species to thrive (Cayford and McRae, 1983). It has a number of commercial applications, including pulpwood, general construction timber, railway ties, poles, pilings, mine timbers and fuel (Rudolf, 1958 Hosie, 1979 Cayford and McRae, 1983 Law and Valade, 1994). Other applications include the extraction of essential oils for aromatic agents in products such as perfumes, cosmetics and cleaners (Maries et al., 2000). 

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