Session 28: It’s not Just Rot: Towards Holistic Evaluation of Wood Product Durability Ground Contact Performance ofCreosote Amended with Chlorothalonil: Can we Reduce Retentions? H. M. Barnes, M. G. Sanders, G. B. Lindsey, and T. L. Amburgey Forest Products Laboratory
Background Creosote supply Reduction of impact (92-192 kg/m3) BMPs Chlorothalonil highly effective Ag crops, paints, mold & sapstain Broad spectrum, low mammalian toxicity Combined with insecticides, antioxidants Removed from AWPA BoS, 2004, lack of use
ObjectivesThis study asks: To what extent can creosote retentions be reduced by the addition of chlorothalonil?
Materials & Methods Wood All sap southern pine 19 x 19 x 1120 mm (r x t x l) Cut into matched halves Preservatives P2 Creosote Chlorothalonil Both met AWPA 2003 specs
Sample Treatment Treated full cell at room temperature 91 kPa vacuum for 30 min Introduction of preservative under vacuum Pressure increased to 1034 kPa in 5 minutes Held for 60 min Vent to atmospheric, drain, remove samples, wipe & weigh 102 mm retain cut from end
Sample Exposure & Evaluation Matched samples placed in Dorman (AWPA Hazard Dorman = silty clay loam Zone 4) & Saucier (AWPA Hazard Zone 5) test plots at depth of 230 mm Rows 0.75 m apartSaucier = loamy sand
Evaluated annually for decay and termite attack
AWPA (2003) visual grading scale for rating decay and termite attack Decay Rating TermitesSound; suspicion of decay 10 Sound; 1-2 small nibblespermitted permittedTrace decay to 3% of cross 9 Slight feeding to 3% of crosssection sectionDecay from 3-10% of cross 8 Attack from 3-10% of crosssection sectionDecay from 10-30% of cross 7 Attack from 10-30% of crosssection sectionDecay from 30-50% of cross 6 Attack from 30-50% of crosssection sectionDecay from 50-75% of cross 4 Attack from 50-75% of crosssection sectionFailure (>75% of cross section) 0 Failure (>75% of cross section)
Data Evaluation Approach 1:Dose response curves CTL after 6 years of exposure
Curves were fitted Time to score of 70 (t70) was calculated for comparison purposes
• Fitted curves constructed to give a dose-response curve over time
Organism Response Decay was more severe than termite attack in both test plots Decay was generally greater at the Dorman site than Saucier Termite attack was generally greater at the Saucier site compared to Dorman
What does the study show? At P2 retentions lower than the AWPA minimum (<92 kg/m3), the addition of CTL improves the performance even for the lowest CTL addition rates For P2 retentions >92 kg/m3, significant improvement is seen only for the highest CTL addition rate
So, can we reduce creosoteloadings and get equivalent orbetter performance by adding CTL? YES, . . . . . but, Will we?
Future research papers will report on Different species including: Red oak (Quercus rubra) Sweetgum (Liquidambar styraciflua)