Boron distribution in green timbers pre-treated with boron rods followed by creosote: 130 week (2.5 year) report

Unseasoned (green) red and white oak bridge timbers and crossties were pre-treated with boron rods installed at equal distances along the length of the timbers. Moisture content and boron levels were examined at 15, 30, 50, 80, and 130 weeks after rod installation and subsequent treatment with creosote. Moisture content for both wood species remained high (above 50%) for the duration of the test period, well above the 30% moisture content needed for boron diffusion. Passive dual treatment with fused borate rods resulted in high boron loadings in both hardwood species, particularly in the longitudinal direction from rod installation points. Boron levels were lower in the outer tangential locations away from where rods were placed. Substantial longitudinal boron diffusion was observed for white oak, suggesting supplemental treatment of low permeability hardwoods may be possible using this preservative system.