Biological Durability of Cross-Laminated Timber— The State of Things

Udele, Kenneth E.; Morrell, Jeffrey J.; Sinha, Arijit

doi:10.13073/fpj-d-20-00076

Cited by 14 publications

(9 citation statements)

References 48 publications

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“…The benefits of MT-based buildings would be their low carbon emission, short construction time, and cost-effectiveness. However, their durability could be of great concern [10][11][12][13][14]. Figure 1 shows schematics of different types of mass timber.…”

Section: Properties Of Wood and Timbermentioning

confidence: 99%

Imaging of Structural Timber Based on In Situ Radar and Ultrasonic Wave Measurements: A Review of the State-of-the-Art

Pahnabi,

Schumacher,

Sinha

2024

Sensors

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With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a detailed review of Ground Penetrating Radar (GPR) and Ultrasonic Testing (UST) is presented. These two techniques can be applied in situ and produce useful visual representations for quantitative assessments and damage detection. With its commercial availability and portability, GPR can help rapidly identify critical features such as moisture, voids, and metal connectors in wood structures. UST, which effectively detects deep cracks, delaminations, and variations in ultrasonic wave velocity related to moisture content, complements GPR’s capabilities. The non-destructive nature of both techniques preserves the structural integrity of timber, enabling thorough assessments without compromising integrity and durability. Techniques such as the Synthetic Aperture Focusing Technique (SAFT) and Total Focusing Method (TFM) allow for reconstructing images that an inspector can readily interpret for quantitative assessment. The development of new sensors, instruments, and analysis techniques has continued to improve the application of GPR and UST on wood. However, due to the hon-homogeneous anisotropic properties of this complex material, challenges remain to quantify defects and characterize inclusions reliably and accurately. By integrating advanced imaging algorithms that consider the material’s complex properties, combining measurements with simulations, and employing machine learning techniques, the implementation and application of GPR and UST imaging and damage detection for wood structures can be further advanced.

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Section: Properties Of Wood and Timbermentioning

confidence: 99%

Imaging of Structural Timber Based on In Situ Radar and Ultrasonic Wave Measurements: A Review of the State-of-the-Art

Pahnabi,

Schumacher,

Sinha

2024

Sensors

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“…CLT panels are a form of engineered wood products (EWP) developed by laminating sawn boards together, commonly by face lamination only (although it can also include edge bonding); the boards are arranged with each layer perpendicular to the previous. Sustained exposure to moisture during construction, in the event of heavy rainfall or plumbing leaks post-construction, can cause moisture gain and lead to possible decay [11][12][13]. A moisture content (MC) exceeding 20% provides an optimum condition for fungal decay in timber products [14,15].…”

Section: Introductionmentioning

confidence: 99%

“…Moisture management is one of the most important considerations when working with timber during construction and in service. Moisture management practises and protocols need to target minimising weathering, moisture gradient (MG) development and elevated MC, reducing the chance of dimensional instability, loss of airtightness, biodegradation and mould growth [13,[18][19][20][21]. Previous studies showed that the location of panels, type of elements (wall, roof, floor), and connection type can affect the moisture gain and drying requirements to return the panels to optimum MC levels [6,[22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Effect of Alternate Drying Techniques on Cross-Laminated Timber after Exposure to Free-Water Wetting

Shirmohammadi¹,

Faircloth²

2023

Forests

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Cross-laminated timber (CLT) panels are commonly used in mass-timber multistorey constructions due to their prefabrication, construction flexibility, environmental credentials and weight-to-strength ratio advantages compared to competing building materials. However, the long-term durability and service life of these mass timber panels require further understanding of their performance when exposed to free water. Wetting and drying trials were conducted by exposing Radiata pine (Pinus radiata) CLT sections to either free water (pooling on a single surface) or submerged water (all directions exposed) saturation, followed by either ambient or fan drying. The panels exposed to water pooling only reached MC above the FSP up to 40 mm of the panel depth. For submerged panels, the MC reached values above the fibre saturation point (FSP) at depths of 30 to 40 mm penetration on both panel faces. When comparing the ambient and fan-drying panel sections over the same time period, a less uniform MC profile was observed for the ambient drying, whereas the fan-dried panels fell below the FSP faster and with a more consistent MC profile. A complementary study was conducted on a standalone 3.0 × 3.0 m CLT room, where the room was wetted during a simulated pipe burst event. The moisture monitoring of wall and floor panels during fan drying of the room showed that an MC reduction from an excess of 40% to below 20% could be reached in less than 96 h for the panels’ surface; however, the middle sections of the panels dried slower than the surface sections. The CLT structure fan drying required a longer drying time than the CLT sections tested due to the closed sections (overlaps and connected faces) and a lower rate of airflow. The study of drying CLT sections highlighted the product reaching and maintaining MC higher than FSP points and the need for further drying applied to minimise long-term decay development. Further study is recommended to investigate the effects of closed sections (connected faces) and the duration of drying needed for semi-finished and finished buildings.

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“…However, currently most CLT are not treated with preservatives and the strategy for durability is restricted to keeping the wood dry. CLT treatment options are needed to address the inevitable need for supplemental protection (Wang et al 2018, Udele et al 2021.Research is underway on the efficacy of common wood preservatives when applied to CLT panels (Mankowski et al 2018(Mankowski et al , 2020(Mankowski et al , 2022. However, the best way to apply such preservatives requires investigation.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Borate Treatment of CLT Panels Using Vacuum: A Proof of Concept

Taylor¹,

Denavit²,

Lloyd³

et al. 2023

Forest Products Journal

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Cross-laminated timber (CLT) is an increasingly popular wood-based alternative for large building applications. CLT panels are typically not treated due in part to a perceived lack of efficient and effective methods for treating large panels and a lack of information on what effect treatment processes may have on the panels' mechanical properties. We propose that treating CLT panels with borate solution, applied under vacuum in flexible bags, could provide a practical and effective option for providing preservative protection for interior applications. Samples were cut from commercially produced CLT panels and treated with borate solution using vacuum. The samples were then evaluated for preservative retention, swelling, and degradation of mechanical properties. Initial treatments resulted in a wide range of preservative retentions and property effects among the products tested. In subsequent adjustments, the treatment parameters were changed to provide consistent and sufficient retention among the products. The vacuum treatment method effectively penetrated cracks in the lumber and the bond lines (adhesive joint between adjacent lamellae). Swelling and effects on mechanical properties were minimal in the adjusted samples. In addition to these samples that were treated in a rigid pressure vessel, a larger sample was successfully treated in a flexible plastic bag. Data from this study support the concept that vacuum treatment of CLT panels with borate can provide sufficient levels of preservative retention, can be adjusted to the material being treated, and has minimal effects on mechanical properties.

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Biological Durability of Cross-Laminated Timber— The State of Things

Cited by 14 publications

References 48 publications

Imaging of Structural Timber Based on In Situ Radar and Ultrasonic Wave Measurements: A Review of the State-of-the-Art

Imaging of Structural Timber Based on In Situ Radar and Ultrasonic Wave Measurements: A Review of the State-of-the-Art

Effect of Alternate Drying Techniques on Cross-Laminated Timber after Exposure to Free-Water Wetting

Borate Treatment of CLT Panels Using Vacuum: A Proof of Concept

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