Protecting the heartwood of wood infrastructure – improving performance with borate dual treatments

ABSTRACT

Wood is by far the best structural material in terms of environmental impact. This superiority can be improved if the longevity of the commodity is extended by reducing the decay susceptibility of the heartwood not typically treatable using pressure methods. Traditionally, heartwood decay has been managed by remedial treatments, or simply by accepting the short service life and the required product replacement costs. Dual treatment is defined here as combining two (dual) preservative systems, a water-diffusible system and an oil-borne pressure-impregnated system being applied to the same piece of wood. This is often done as separate treatments; in this case, it is essentially the same as using an oil-borne preservative with a remedial diffusible treatment (typically a sodium borate salt), but has the benefit of preventing decay before it happens. Adding borates to railroad crossties prior to seasoning and treatment has been shown to provide significant benefit to crossties and utility poles. Treatment of bridge timbers has now also been commercialized using a further modification of this approach, with even higher unit cost savings and commercial testing is now underway in utility poles. The global infrastructure industry is urged to review the opportunity offered with this now-proven technology.

KEYWORDS:

• Borate
• bridge
• diffusion
• dual treatment
• durability
• fungal decay
• impregnation
• Poles
• railway sleepers
• ties

Disclosure statement

No potential conflict of interest was reported by the author(s).