The fire resistance of cross-laminated timber (CLT) could be improved by treating the lamina with fire retardants. The major issues with this technology are the reduced bondability of the treated lamina with commercial adhesives. This study assessed several surface preparation methods that could improve the bondability and bond durability of fire-retardant treated wood with two commercial adhesives. Four surface preparation methods, including moisture/heat/pressure, surface planing, surface chemical treatment, and surface plasma treatment were assessed for their impact on the bondability and bond durability of lodgepole pine lamina. The block shear test results indicated that all surface preparation methods were somewhat effective in improving bond performance of fire-retardant treated wood compared to the untreated control wood samples, depending on the types of fire retardants and wood adhesives applied in the treatment process and bonding process. The selection of surface preparation, fire retardant, and wood adhesive should be considered interactively to obtain the best bond properties and fire performance. It may be possible to effectively bond the treated lamina with PUR adhesive without any additional surface preparation for the fire retardant used in the treatment at FPInnovations.
Current design standards incorporate the use of preservative treated and naturally durable wood where conditions are suitable for deterioration, but treatment options for mass timber products, particularly, cross laminated timber (CLT) remain to be addressed. Termiticide treatment is a necessity for CLT structures, especially in southeastern climates. Wood species currently used to fabricate CLT are non-durable, and current design standards do not properly address incorporation of preservative treatments into these systems. In this study, 12” x 14” x 4” Douglas-fir CLT pieces were installed in a ground proximity protected test at the Harrison Experimental Forest (HEF), (Saucier, MS). Test samples were placed in sets of two in 30” x 30” subplots on bricks approximately 3-4” above soil and covered with ventilated waterproof covers. A total of 20 test pairs (40 total samples) with four different treatments were installed. The treatments consisted of a soil termiticide treatment, a preventive borate spray treatment at initiation, a remedial treatment with the spray-on borate one year post initiation and untreated controls. Soil below five pairs of samples was treated the with a soil termiticide (Termidor® SC). For the preventive borate at initiation treatment, one sample per pair of five other sets was treated with a spray-on borate preventative treatment (Bora-Care®). The remaining ten pairs were left as untreated controls. Temperature and humidity inside some of the covered units is being monitored throughout the test. The ten control sets will be examined for termite attack 12 months after installation. Five of the attacked sets will be treated with spray-on borate as a remedial treatment for active termite attack.
Glulam and laminated veneer lumber protected by a combination of treatment with borate by two processes, and a film-forming coating, were exposed outdoors in an above-ground field test using a modified post and rail test design. After eight years’ exposure, early to moderate decay was found in untreated test units, while those which were borate-treated by either method were generally sound up to six years and showed greatly reduced decay at eight years.
Glulam manufactured from laminating stock of three species pre-treated with ACQ-D or CA was exposed outdoors in an above-ground field test using a modified post and rail test design. After six years’ exposure, early to moderate decay was found in untreated test units, while those which were preservative-treated were completely sound.
The objective of this research was to examine the LOSP treatment options available for H3 exposed glulam of Pinus radiata and P. elliottii. Test specimens were treated before or after gluing with azole LOSP, while some were treated with TBTN or CCA for comparison. They were then exposed at Innisfail or in an Accelerated Field Simulator (AFS) designed to give severe exposure and accelerated results. After 3.1–3.2 years, test specimens were given a performance rating from a scale of 8 (sound) to 0 (destroyed by decay).
The results suggest that treating glulam before gluing will generally give better performance than treatment after gluing.
Decay was more rapid in vertically exposed than horizontally exposed specimens, suggesting that glulam posts need special attention to prevent water penetration. End grain sealants based on copper naphthenate or zinc naphthenate gave improved decay resistance, but on their own were insufficient for post end protection. This suggests that a better approach would be to include barriers (caps) as well, or to use designs where the end is not exposed to rain or can drain away readily.