Long-term durability of CCA and ACA : how is 0.4 doing?

Abstract

For decades the phrase “point 4” was synonymous with wood treated for use in contact with the ground. In this paper we review how and why the 0.4 lb/ft³ (6.4 kg/m³) retention became such an accepted standard, and then evaluate how well this retention has performed in long term stake testing. Data from plots near Saucier, Mississippi that contained southern pine 2 by 4 nominal (38 by 89 mm) stakes pressure treated with either ACA, CCA-A, CCA-B or CCA-C were evaluated. The plots ranged in age from 20 to 61 years. The data indicate that the 0.4 lb/ft³ (6.4 kg/m³) retention has provided good, but not unlimited, protection of wood placed in ground contact. Durability was notably diminished at retentions below 0.4 lb/ft³ (6.4 kg/m³) and durability was greater for retentions above 0.4 lb/ft³ (6.4 kg/m³). The 0.4 lb/ft³ (6.4 kg/m³) retention appears to be near the minimum for long-term ground contact, and the selection of 0.4 lb/ft³ (6.4 kg/m³) for general ground contact applications and 0.6 lb/ft³ (9.6 kg/m³) for critical applications appears to have been a wise choice. The data also indicates that the 0.4 lb/ft³ (6.4 kg/m³) CCA retention is not excessive, and is an appropriate choice for comparison to test formulations intended for use in ground contact applications.

Citation

Lebow, Stan T.; Hatfield, Cherilyn A.; Woodward, Bessie. 2010. Long-term durability of CCA and ACA: How is 0.4 doing? In: Proceedings, one hundred sixth annual meeting of the American Wood Protection Association. Savannah, GA, 2010 May 23-25: vol. 106. Birmingham, AL: American Wood Protection Association, c2010: 174-183.