New Method for Pretreatment of Railroad Crossties

IRG/WP 14-40675

A S Ross, R W Clawson Jr

Creosote has been successfully utilized for nearly 150 years for the protection of railroad crossties (sleepers) in the USA and remains today as the most widely used wood preservative for this application. One of the few shortcomings of creosote as a preservative is its inability to penetrate many of the refractory hardwood species which make up the majority of crossties in the USA. Lack of full penetration often leaves the cores of these ties unprotected, making them vulnerable to attack by decay fungi and termites. As a result, service life can be significantly reduced, particularly in the Southeast and Gulf Coast regions of the USA. Twenty-Five years ago, Amburgey and Williams addressed this need through the development of a dual treatment for crossties consisting of an initial dip pretreatment with borates (e.g., DOT) followed by a period of diffusion, then another period of seasoning, and finally a conventional pressure treatment with creosote. The treatment resulted in a borate-treated core surrounded by a creosote-treated shell. It performed well, as evidenced by 20 years’ worth of field data showing a meaningful increase in service life of dual-treated ties over conventional creosote-treated ties. However, the inefficiencies of the Amburgey/Williams dual treatment process, encompassing long storage periods of ties during the diffusion and seasoning steps, have limited its commercial utilization. This paper describes a new method for pretreatment of crossties which greatly improves the efficiency of the original dual treatment process while achieving the same borate and creosote penetrations and retentions which were shown to perform well in 20 years of field data. The new process is a chemically-based technology which utilizes a Buffered Amine Oxide carrier to penetrate the cellular structure of wood and deposit and bind wood protection chemicals such as borates and carbon based insecticides deep into the core of substrates including refractory species. The new process was introduced commercially in 2010 and has since been used to treat over 10 million crossties for Class I railroads in the United States.

Keywords: buffered amine oxides, railroad ties, penetration

Conference: 14-05-11/15 St George, Utah, USA

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