Permanence and Diffusion of Borax-Copper Hydroxide Remedial Preservative Applied to Unseasoned Pine Posts: 10 Year Update

摘要

In 1993, unseasoned pine posts were treated with groundline remedial treatment containing 3.1% copper hydroxide and 40% sodium tetraborate decahydrate (borax). The soundness of the posts was periodically evaluated using a push test. After 3.5, 6.5, and 10 years, sections were taken from two posts to determine retention of borax and copper hydroxide below ground to 36 cm (14 in.) above ground. By 3.5 years of exposure, all untreated control posts had failed. After 6.5 and 10 years, the remedially treated posts were generally sound at the groundline but most suffered top decay. Average borax retention was 24.2, 15.8, and 10.6 kg/m~3 (1.51, 0.99, and 0.66 lb/ft~3) after 3.5, 6.5, and 10 years, respectively. Average copper hydroxide retention was 3.7, 4.2, and 3.5 kg/m~3 (0.23, 0.26, and 0.22 lb/ft~3) after 3.5, 6.5, and 10 years, respectively. Although retentions varied among posts, in most cases the borax retentions were still above the threshold needed to prevent attack by decay fungi even 10 yearsafter treatment.