PSI - Issue 72

Muh. Linggar Adi Wardhana et al. / Procedia Structural Integrity 72 (2025) 418–426

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wood is essential to mitigate this risk, enhancing its fire safety. A recently developed flame retardant coating has been designed to protect wood from fire (Thomas et al., 2021; Chen et al., 2010; Singh et al., 2023; Mensah et al., 2023; Hansen et al., 2023). The test specimen was Douglas fir Glulam coated with a flame-retardant material. Two types of flame-retardant coatings were used in the test. The first coating consists of tellurium, borate salt, aerogel, and melamine, while the second coating consists of ammonium polyphosphate and borate salt. Both coatings are transparent materials, ensuring they do not significantly alter the wood's original appearance. Figure 5(a) shows the wood specimens undergoing the coating process. Testing was conducted using furnaces and temperatures based on ISO 834 standards, as shown in Figure 5(b) (ISO 834-14., 2019).

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Fig. 5. (a) Coated specimens before the test; (b) Setup for standard fire exposure (Zheng et al., 2024).

A delayed combustion ratio is utilized to assess the effectiveness of the transparent fire-resistant coating in slowing down the rate of wood combustion. This ratio is defined as the decrease in the charring rate of the wood material due to the application of the refractory coating compared to the uncoated wood. The experimental specimens were classified into six types based on coating type and member size. Uncoated large-size specimen (BR0), a coated small size specimen with Coating 1 (R1), a coated small-size specimen with Coating 2 (R2), a coated large-size specimen with Coating 1 (BR1), and a coated large-size specimen with Coating 2 (BR2). For coated small-size specimens (R1 and R2), three different coating quantities were chosen to study the effect of coating quantities on the charring behavior of Glulam. The average rations of delayed sharing (15-25 min) for Coating 1 and Coating 2 were 29.6 % and 30.7%. The corresponding ratios for the 40-50 min exposure time were 12.4% and 18.2%. Specifically, the ratio of delayed charring for the exposure time of 40-50 min was about 60% of that for the exposure time of 15-25 min. Test results show that the two transparent fireproof coatings can effectively delay the charring behavior of wood materials compared to uncoated specimens, as shown in Figures 6 and 7.

Fig. 6. Ratio of delayed charring over time for (a) small-size; (b) large-size specimens(Zheng et al., 2024).