The Ministry of Forests, Lands, Natural Resource Operations and Rural Development (FLNRORD) has asked FPInnovations to investigate current information and knowledge for bridge fire impact mitigation opportunities and strategies.
The extent of the investigation includes reaching out to domestic and international contacts to find directly applicable information and literature on strategies to mitigate fire impacts to bridge structures. This will include review of academic journals and reports, products and methods, to find
Mould growth in buildings is becoming an increasing concern for building owners because of health and aesthetic problems. Mould usually appears as black or greenish-brown patches on surfaces in humid environments and is common in houses. In fact, mould growth is caused by moisture problems. To avoid moisture problems, the most important consideration in ensuring the durability of wood-frame houses is to utilise design features, construction tools and practices that keep wood as dry as possible and promote drying if the wood gets wet. One critical factor in these designs is the accurate estimate of the effects of various temperature and moisture conditions on the rates of fungal attack. The absence of definitive data forces engineers to make extremely conservative estimates of mould growth that may not accurately reflect the risk. This report provides valuable data on mould growth on various wood and fibre products used for the construction of homes in North America.
Sapwood and heartwood of jack pine, white spruce and aspen and heartwood of white cedar, commercial aspen OSB bonded with PF resin, softwood plywood, low-density fibreboard, gypsum board, and fibreglass insulation materials were tested by a modified method of ASTM D 3273-94 standard for mould growth test. Test materials were cut into wafers of 5 cm x 12 cm x 1 cm sample size and were placed in specifically designed incubation containers for 8 weeks. Temperatures were targeted at 20°C and 30°C, and relative humidities (RH) were targeted between 65 and 100% by means of saturated salt solutions. Test samples were inspected weekly for mould growth for 8 weeks. A RCS Biotest air sampler monitored mould spore densities inside containers. Moisture contents (MC) of wood wafers were determined by oven-dry method (105°C) at the beginning and at the end of the test. Volatile organic compounds (VOC) were collected from clear and mouldy samples at the beginning and the end of the test and were analyzed according to the ASTM D5116-97 and EPA TO-17 methods. Thermal Desorption/Gas Chromatograph/Mass Spectrometer (TDU/GC/MS) analytical equipment was used to desorb, characterize and quantify the VOC collected on the sorbent tube. The compounds were identified with the NBS/NIH Mass Spectra database and quantified by extrapolating the chromatogram peak area of each compound with the calibration curve of alpha-Pinene, which was the selected chemical for VOC measurement.
Results showed that the targeted temperatures were measured as 20°C and 28°C and the targeted relative humidities were measured as 63% to 95%. At 20ºC and 95% RH, mould growth was found as the following: on the sapwood of jack pine and aspen and on fibreboard in the second week of incubation, on the sapwood of white spruce and OSB in the third week, on plywood and gypsum board in the fourth week, and on the heartwood of jack pine and aspen in the fifth week. No mould growth was detected on the heartwood of white spruce and cedar and on fibreglass isolation materials at the end of the test in eight weeks. Slight mould growth was found on sapwood of white spruce, jack pine and aspen and on 4 types of composite boards after 3 to 8 weeks at 20ºC and 85% RH. Moulds were unable to attack wafer samples at 76% and 73% RH. At 28ºC, a similar mould growth pattern was observed as those tested at 20ºC. No mould growth was detected on any of test materials at 63% and 71% RH. Mould growth was detected on the sapwood of white spruce and aspen, and on plywood and fibreboard at 84% RH for this temperature. At 93% RH, moulds appeared on plywood and fibreboard in the second week of the test. Fungi at the end of the test did not affect the heartwood of white cedar and white spruce and fibreglass insulation material. For all materials tested, low-density fibreboard was most susceptible to mould growth, followed by OSB, plywood, gypsum board and the sapwood of all solid wood species. Heartwood of jack pine and aspen was less infested by moulds. Heartwood of white cedar and white spruce and fibreglass insulation material were resistant to mould growth. On most materials, rapid mould growth was found in 4 to 6 weeks of incubation in the favourable environmental conditions.
Spore densities in incubation containers increased correspondingly with incubation time. More spores were collected from containers maintained above 88% RH than other containers. There was no significant difference of spore density among containers maintained at less than 85% RH. Majority of moulds presented in sampling media were identified as Penicillium citrinum, P. vermiculatum and Aspergillus niger.
For all wood materials tested, low-density fibreboard was most prone to absorb water from air, while cedar heartwood was the least. At 20ºC and 95% RH, fibreboard increased its MC from 4% MC at the beginning of the test to 33% MC at the end of the 8-week test, while cedar heartwood increased its MC from 11% at the beginning to 21.6% at the end. The other wood materials gained their MC from 17.7% to 22% in the same environmental condition.
The VOC profile analysis showed that several compounds were not detected from clean reference samples but only detected from the mouldy samples, which are called microbial VOC. Compounds detected from mouldy OSB samples were different from those detected from mouldy fibreboard samples. From mouldy OSB samples, the predominant detected VOC were 2-, or 3-pentanone and 2-petanol. From mouldy fibreboard, they were identified as borneol, camphor, 3-cyclohexen-1-ol (4-methyl), pyrazine-methyl and 1-octen-3-ol. These compounds have potential to be used as mould growth indicators on wall materials.
In the next edition of the CSA O80 wood preservation standards, retention by assay rather than by gauge will be specified for chromated copper arsenate (CCA), ammoniacal copper arsenate and creosote. Based, in part, on the 14-year data from Forintek's field trials, these assay retentions will be lower than the old gauge retentions and lower than the assay retentions which had been specified in the AWPA standards (the AWPA independently introduced lower retentions for northerly waters in 1995). Continued testing is needed to confirm that the lower retentions will still provide the service life required from marine structures. The marine tests covered in this report were set up in 1978 in West Vancouver and in 1984 at two sites in New Brunswick. Red pine sapwood coupons (6 x 50 x 200 mm) were pressure treated with a range of retentions of preservatives which were listed in the standards at the time. They were suspended in the water column on metal racks and inspected once a year. Due to the poor state of repairs of the dock at Shediac the samples at this site could not be inspected at this time. At the West Vancouver test site coupons treated to the proposed assay retention with CCA (24 kg/m3) were in excellent condition after 17 years exposure. ACA treated coupons at the proposed assay retention of 30 kg/m3 had suffered from surface degradation by bacteria and fungi. While significant on a thin test coupon, such degradation on a marine pile or timber would have very little effect on the strength of the structure. Wrapping the ACA treated coupons for a period after treatment to simulate the drying rate of large dimension commodities did not improve its performance. Untreated coupons failed in less than a year at West Vancouver and between two and three years at Whitehead Island. At Whitehead Island, coupons treated to the proposed assay retentions with CCA and ACA were still performing well after 11 and 8 years exposure respectively (higher retention ACA added 3 years after experiment set up). Interestingly the pressure treated wood has performed better than the test racks. The racks at West Vancouver, made from 3.5mm thick carbon steel, had moderate corrosion after 10 years and had to be replaced after only 15 years.
In the most recent edition of the CSA O80 wood preservation standards, retention by assay rather than by gauge was specified for chromated copper arsenate (CCA), ammoniacal copper arsenate, and creosote. Based, in part, on the 14-year data from Forintek's field trials, these assay retentions are lower than the old gauge retentions, and lower than the assay retentions which had been specified in the AWPA standards. The AWPA independently introduced lower retentions for northerly waters in 1995. Continued testing is needed to confirm that the lower retentions will still provide the service life required from marine structures.
The marine tests covered in this report were set up in 1978 in West Vancouver, BC and in 1984 at two sites in New Brunswick. Red pine sapwood coupons were pressure-treated with a range of retentions of preservatives which were listed in the standards at the time. They were suspended in the water column on metal racks and inspected once a year until 2000 at West Vancouver and 1997 at the New Brunswick sites.
At the West Vancouver test site, coupons treated to the recommended assay retention with CCA-C (24 kg/m3) were in excellent condition after 22 years’ exposure. ACA-treated coupons at the recommended assay retention of 30 kg/m3 had failed due to surface degradation by bacteria and fungi. While significant on a thin test coupon, such degradation on a marine pile or timber would have less effect on the strength of the structure. Wrapping the ACA-treated coupons for a period after treatment to simulate the drying rate of large dimension commodities did not improve its performance, nor did using an alternative formulation with a higher proportion of copper. The performance of creosote at above the recommended retention was superior to ACA but significantly inferior to CCA.
Untreated coupons failed in less than a year at West Vancouver and between two and three years at the New Brunswick sites, Shediac Bridge and Whitehead Island. At Whitehead Island, coupons treated to the recommended assay retentions with CCA and ACA were still performing well after 13 and 10 years’ exposure respectively (higher retentions of ACA were added three years after the experiment was set up). However, at Shediac, while CCA-treated samples treated to 24 kg/m3 remained sound, coupons treated to 30 kg/m3 ACA had deteriorated badly after 10 years in test. In contrast, samples treated to close to the recommended retention with creosote performed better at Whitehead Island than at Shediac Bridge.
Interestingly the pressure-treated wood has performed better than the test racks. The racks at West Vancouver, made from 3.5mm thick carbon steel, had moderate corrosion after 10 years and had to be replaced after only 15 years of service.
