The Effects of CCA Preservative Treatment and Redrying on the Bending Properties of 2 X 6 Southern Pine Lumber


  • J. E. Winandy
  • R. S. Boone


Mechanical properties, bending strength, CCA, treatments, preservatives, kiln-drying, redrying, lumber, southern pine, pith


Southern pine dimension lumber (commercially graded No. 2 loblolly pine 2 x 6s) was treated with chromated copper arsenate (CCA) preservative (0.4 or 0.6 pcf) and then air-dried or kiln-dried (160, 190, or 240 F). CCA treatment significantly reduced average bending strength, but no discernible differences were found between controls and CCA-treated groups in the extreme lower portions (< 10th percentile) of the bending-strength distributions. When these same specimens were then considered solely on the basis of strength-reducing characteristics, there were obvious differences in how the CCA treatments and subsequent redrying affected these various strength-ratio grades of 2 x 6 lumber; higher grades appeared to be less affected than lower grades. Similar to the trend shown when commercially graded, the middle and upper portion of each strength-ratio grade bending-strength distribution than did drying at 240 F affected a broader range of the bending-srength distribution than did drying at 160 F. The broadened range of significant effects noted after high-temperature redrying indicates that posttreatment kiln-drying temperatures higher than 190 F should be avoided.

The effects of CCA treatment and redrying were highly interactive with strength-ratio grade and the presence or absence of pith. CCA treatment reduced the strength of lumber containing pith and having a strength ratio of <0.65 to a greater extent than pith-free lumber of any strength-ratio grade. Lumber having a strength ratio of >0.65 and containing pith was not affected by CCA treatment. The magnitude of this pith-related interaction demands recognition.


American Society For Testing and Materials. 1984. The annual book of ASTM standards. Sec. 4, Vol. 4.09, ASTM D 198 and ASTM D 245. Philadelphia, PA.nAmerican Wood-Preservers' Association. 1986. AWPA book of standards. Standards P-5, C-2, C-15, and A-9. Stevensville, MD.nBarnes, H. M., and P. H. Mitchell. 1984. The effect of post-treatment redry schedule on the strength of CCA-treated southern pine dimension lumber. Forest Prod. J. 34(6):29-33.nBendtsen, B. A., L. R. Gjovik, and S. Verrill. 1983. The mechanical properties of salt-treated longleaf pine. USDA Forest Serv. Res. Pap. FPL 434, Forest Prod. Lab., Madison, WI.nDebonis, A. L., F. E. Woeste, and T. E. McLean. 1980. Rate of loading influence on southern pine 2 by 4's in bending. Forest Prod. J. 30(11):34-37.nKnuffel, W. E. 1985. The effect of CCA preservative treatment on the compression strength of South African pine structural timber. Holzforschung und Holzverwertung 37(5):96-99.nMitchell, P. H., and H. M. Barnes. 1986. Effect of drying temperature on the clear wood strength of southern pine treated with CCA-Type A. Forest Prod. J. 36(3):8-12.nNational Forest Products Association. 1986. National design specifications for stress-grade lumber and its fastenings. Washington, DC.nNicholas, D. D., and A. F. Preston 1984. Interaction of preservatives and wood. Pages 307-320 in R. M. Rowell, ed. The chemistry of solid wood. Advances in Chemistry Series No. 207. American Chemical Society, Washington, DC.nSAS Institute. 1982. Statistical Analysis Systems (SAS) User's Manual. Cary, NC.nSouthern Pine Inspection Bureau. 1977. Southern Pine Inspection Bureau (SPIB) Grading Rules. Pensacola, FL.nWinandy, J. E., B. A. Bendtsen, and R. S. Boone. 1983. The effects of delay between treatment and drying on the toughness of southern pine treated to two CCA retention levels. Forest Prod. J. 33(6):53-58.nWinandy, J. E., R. S. Boone, and B. A. Bendtsen. 1985. Interaction of CCA preservative treatment and redrying: Effects on mechanical properties of southern pine. Forest Prod. J. 35(10):62-68.n






Research Contributions