Carbon-based preservatives have demonstrated reasonable long-term field performance in above ground testing. This study examines the performance of a carbon-based preservative formulation containing quaternary ammonium compounds and tebuconazole as a treatment for three softwood species exposed in ground contact at two sites in Canada. The treatment was associated with improved decay resistance and greater durability than the naturally durable reference species, western red cedar. The treatment was also associated with improved termite resistance, though progressive termite attack was observed when the material was installed near an active colony. A dose effect and a species effect were observed with higher concentrations and better penetration associated with greater resistance to biodegradation. While durability was improved by this carbon-based preservative treatment, it did not match the field performance found in previous or concurrent studies of standardized copper-based systems.

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