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Article

A Comparative Study of the Fire Properties of Chinese Traditional Timber Structural Components under Different Surface Treatments

by
Yupeng Li
1,
Sokyee Yeo
1,* and
Shibing Dai
2,3,*
1
School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710061, China
2
Key Laboratory of Ecology and Energy Saving Study of Dense Habitat, Ministry of Education, Shanghai 200092, China
3
College of Architecture and Urban Planning, Tongji University, Shanghai 200092, China
*
Authors to whom correspondence should be addressed.
Buildings 2024, 14(8), 2439; https://doi.org/10.3390/buildings14082439
Submission received: 5 July 2024 / Revised: 26 July 2024 / Accepted: 6 August 2024 / Published: 7 August 2024
(This article belongs to the Section Building Energy, Physics, Environment, and Systems)
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Versions Notes

Abstract

:
Fire is generally recognized as a major threat to the protection of historic timber architecture. Thus, there is an urgent need to study the fire properties of historic timber structures so as to better protect them in the future. Two types of commonly used wood species (pine and poplar) were selected as test specimens and three types of surface treatments (Chinese traditional coating, modern flame retardant, and a combination of the two methods) were applied. The specimens were subjected to a semi-full-scale fire test. The charring rate and the surface heating curve were calculated during the fire test to assess the flammability of various woods under different treatments. Results showed that the fire properties of traditional-coated wood were better than the modern type, but large amounts of smoke were released during combustion. The combination of traditional and modern methods did not significantly improve the overall fire properties and was even worse than the traditional treatment alone. At the same time, the fire properties of the modern method are highly correlated with the type of wood species used. The above results can provide informative advice on the selection of suitable surface treatments for the subsequent restoration of ancient buildings.

1. Introduction

As a renewable and readily available material, timber is commonly used in structural and non-structural parts of traditional Chinese buildings for load bearing, decorative, partitioning, and other functions [1,2,3,4]. Recent statistics reported that 356 cases of fire happened in traditional timber buildings between 2000 and 2008 in China, which included several national-level monument sites [5,6]. Due to its lower fire properties compared to other modern building materials, the high flammability of timber has become its biggest disadvantage as a building material. This is because when a timber-frame building catches fire, it spreads very rapidly, making fire-fighting very difficult. For the past few decades, limited studies have been conducted on the fire properties of traditional timber buildings. Therefore, there is an urgent need to conduct more research on the fire performance of ancient timber-frame buildings so as to better protect these precious heritage sites in the future.
When a traditional timber building catches fire, the primary burning source to fuel the continual burning is the timber structural components and its interior movable items such as wooden furniture and fiber products [7]. Therefore, understanding the fire properties of timber components is crucial to the fire protection of ancient buildings and is an important element to be considered during the conservation phase of historic buildings. In ancient practice, Chinese timber structural components were usually coated with “Yi-ma-wu-hui”, a form of multi-layer hemp plaster used as a traditional flame-retardant treatment [8,9]. Although the initial purpose of this treatment was to protect the timber components from fungal and insect attacks, recent studies revealed that this traditional method also possessed a certain level of fire properties [10,11]. Apart from the traditional method, the current modern approach mainly uses various types of flame-retardant coatings to improve the general fire properties of wood, such as epoxy, disodium octa-borate tetrahydrate, and ammonium polyphosphate [12,13,14]. In recent years, various studies on fire protection methods and strategies for both modern and ancient timber structures have been discussed [14,15,16,17,18,19,20,21,22,23]; however, limited studies can be found on the fire performance effect of combining modern flame-retardant coatings with traditional methods onto timber members. Current research on the fire properties of ancient Chinese timber-frame buildings revealed that most of the fire tests conducted mainly focused on a single type of timber species; the inclusion of more timber species in the tests was rarely considered. For example, Xu et al. performed a three-sided fire test to investigate the mechanical properties of southern pine treated with traditional treatment [11]. Zhang et al. used Douglas fir to investigate the residual bearing capacity of timber columns after firing on one side and two adjacent sides [24]. It is also noted that conventional fire dynamics simulation software (Version 6.8.0) commonly assigns uniform parameters for tests relating to wood combustion properties. However, timber species used in existing ancient Chinese timber-frame buildings are often diverse, comprising mainly softwoods (deciduous timber) and hardwoods (broadleaf timber). Due to their difference in fiber structure and cellulose content, the density and fire properties of softwood and hardwood timber species differ significantly. It is therefore important to investigate the effect of the same surface treatment on the fire properties of different wood species.
Adhering to the Chinese cultural heritage conservation guidelines, most of the domestic studies relating to the fire properties of Chinese ancient buildings’ timber elements mainly focused on traditional surface coating treatments, such as traditional hemp plaster and lime plastering treatments [10,24]. Whilst, from the modern approach, fire retardants capable of becoming colorless and odorless when dried after application have been widely used in actual restoration projects of ancient Chinese buildings. Jiang and Li et al. compared the heat release rate, peak heat release rate, total heat release, effective heat of combustion, total smoke release, CO and CO2 yield, and other smoke generation properties of rubber wood treated with different flame retardants to evaluate their flame-retardant effects [19]. Fire tests for the flame-retardant effect of modern flame retardants are often conducted using synthetic materials such as plywood or powdered wood [24,25,26,27,28,29]. By cross-referencing the thermogravimetry analysis (TGA) and derivative thermogravimetry (DTG) curves of archaeological wood and healthy wood at 15 °C/min, Yuan et al. noted that archaeological wood, due to hemicellulose degradation and relatively higher lignin content, resulted in a lower starting temperature of the pyrolysis stage, and showed a lower rate of weight loss than modern healthy wood [24]. From the above literature, it is clear that studies relating to the application effects of modern and traditional flame retardants on ancient timber buildings are limited and inconclusive. Hence, there is an urgent need to clarify the above issues so as to better safeguard precious timber-frame monuments from any unnecessary fire damage.
Using three types of wood species commonly found in northern Chinese timber-frame buildings, the main goal of this study is to assess and compare the fire properties of Chinese timber structural members when subjected to different surface treatments. A series of semi-full-scale single-sided fire tests was conducted to trace the burning process of different treatments. Test results were then further analyzed to obtain the charring rate and surface heating curves and the flammability of different wood species under different surface treatments was evaluated.

2. Materials and Methods

A preliminary study on the fire-spreading trend of ancient timber architecture was carried out using Fire Dynamics Simulator (FDS) software (Version 6.8.0) to determine which part of the timber-frame structure is most vulnerable when subjected to fire. Trial simulations revealed that although smoke usually starts from the fire source and spreads upward to the roof and then diffuses in all directions, the interior top space, specifically the roof rafter region, tends to build up the highest temperature compared with other parts of the building [30]. Hence, in this study, the rafter component was selected as the area of focus as it is found to be more prone to fire.

2.1. Specimen Making

2.1.1. Choice of Wood Type and Specimen Size

From our previous field investigation, two wood species, Pinus sylvestris var. mongolica Litv. (pine) and Populus L. (poplar) were found to be used commonly in northern China. Pine is often used as an alternative for the repair of ancient timber structures while poplar was a common material for rafters in ancient times [30]. Hence, pine and poplar were selected for this study (Figure 1).
Previous fire tests noted that the crushing load under fire is related to the slenderness of the timber column and that without considering the length, the smaller the section area of the timber column, the more fragile it is when subjected to fire [30]. With reference to the past literature review conducted on the Tang and Song period ancient timber architecture in China, the rafter diameter ranges between 100 mm and 160 mm. Since section area has a greater impact on flammability than the length of the rafter component, in this study, the smallest diameter of 100 mm was chosen and the final dimension of the test specimen was designed to be ∅100 × 400 mm.

2.1.2. Choice of Surface Treatments

Traditional Treatment—“Yi-ma-wu-hui”: based on the ancient Chinese construction manual that was published in the Song dynasty, entitled Ying Zao Fa Shi, “Yi-ma-wu-hui” is a traditional Chinese architectural coating method commonly used to protect timber structures. The multi-layer hemp plaster method is often used to treat the timber surface against insect infestation and is also used as a base coat for traditional painting. An overview of the traditional coating treatment is summarized in Figure 2.
Modern Treatment—Flame Retardant: Remmers Adolit BSS 1, purchased from Remmers’ distributor in China, Desaibao Group (Shanghai, China), was selected as the modern treatment approach, which is widely used in cultural relic protection and historical building repair in China. It is a boron-free and water-based flame retardant for timber that is colorless and odorless after drying. Only specimens with a moisture content of less than 18% and a smooth surface can be coated. During the application process, the specimens were placed outside at around 28 °C and the flame retardant was applied with brushes every four hours, three times in total, using the reference dosage of 0.3 kg/m2.
The surface color change in the wood was also documented during the application of the flame retardant. The untreated and treated wood samples were photographed under the same lighting conditions and the average RGB values of the photographs were obtained using the Python algorithm. The above-described data are presented in Table 1 and Figure 3. A slight darkening of the surface color of the wood is evident in both wood species, with the yellowing of poplar being more pronounced.
Combined Treatment—Traditional and Flame Retardant: The specimen was first coated with the same modern flame retardant (Remmers Adolit BSS 1) followed by the traditional method, of which the same application procedures for both treatments as mentioned above were used. Light polishing was carried out on the dried modern coating layer to create a rough interface so as to allow an effective binding of the traditional coating with the modern coating surface.
Subject to the four types of treatment scenarios, a total of 24 specimens were fabricated for the single-sided fire test. Basic information about the test specimens is summarized in Table 2 and the details of the single-side fire test are covered in Section 2.2. The specimens used in this study were classified and numbered in the order of “Species—Surface treatment—Serial number”, where “Pi” and “Po” refer to pine and poplar, and “N”, “R”, “T”, and “RT” refer to no treatment (control), modern treatment (Remmers), traditional treatment, and combined treatment, respectively (Table 2).
Prior to the execution of the single-sided fire tests, the moisture content of the specimens was measured before and after the coating treatment. It was found that the flame-retardant coating increased the moisture content of the wood by at least 6% [31,32] and that the increase in moisture content trend was similar for both types of wood (Table 3).

2.2. Single-Sided Fire Test

A semi-full-scale single-sided fire test was chosen for this study [33,34]. Prior to the test, the initial mass (m0) and moisture content (MC) of all the wood test specimens were measured. For the two wood species, three identical specimens were tested for each treatment (Table 2), where the first two specimens were subjected to a 5 min fire test while the last one was subjected to a 10 min test to obtain the ultimate burning trend of the test component. A commercially available butane fuel cartridge with a blow torch lighter was selected as the main fire source for the fire test. For each test, a fresh can of the butane fuel cartridge was used to maintain a consistent burning power throughout the test. The butane fuel cartridge was positioned 15 cm from the test specimen, ignited to full power at the start of the test, and the burning process was timed and traced via video recording.
A total of four cameras with video recording functions were set up at the front, back, and left side of the specimen to record the burning trend of the wood during the test, while an infrared thermographic camera (Guide Sensmart’s PS610 with 640 × 480 IR resolution, GUIDE INFRARED GROUP, Huzhou, China) was placed on the right side to record the temperature changes in the specimens throughout the test. The initial burning temperature of each fuel cartridge was also monitored using the infrared thermographic camera to ensure proper working of the cartridge at the start of each test. Due to the difference in surface treatments and wood species, the lowest and highest temperatures measured ranged from 121.8 °C to 127.2 °C; hence, the average starting burning temperature was approximately 124 °C.
Apart from conducting a temperature analysis of the video footage at one frame per second, other parameters such as relative humidity and atmospheric temperature were also measured by the infrared thermographic camera to obtain a more accurate analysis. The schematic experimental layout is shown in Figure 4. At the end of the test, the remaining mass (m1) of the specimens was recorded. Then, the specimens were placed in the shade to dry and cool before being cut in half along the burning region for further study.

3. Results

3.1. Visual Observation

The burning trend and conditions of the pine and poplar specimens during the fire test, as recorded by video camera 3, were systematically intercepted at 10 s, 30 s, 60 s, 300 s, and 600 s, respectively (Table 4 and Table 5). Meanwhile, as the fire was found to continue burning on the surface of the wood after the fire source was removed, the total time duration (T) for the surface flames to completely extinguish was also recorded in Table 4 and Table 5.
In the early stages of fire on non-treated pine specimens (Pi-N), the wood rapidly turned black and spread outwards (Table 4). Flames then began to appear on the surface and the wood cracked and became visibly red. Later, the flame became smaller and the charred area of the wood slowly expanded. The charred part of the specimen then appeared greyish-white with severe depressions at the end of the fire. The flames on the surface lasted for 3.6 s after the fire source was removed. Modern treatment pine specimens (Pi-R) took a longer time to burn on the surface when subjected to fire and the flames were generally smaller than the non-treated ones. The flames on the surface were extinguished immediately after the fire source was removed, thus further damage to the wood was effectively stopped.
Poplar specimens, on the other hand, appeared to have much poorer fire properties than pine (Table 5). Untreated poplar generally caught fire much faster and produced larger charred areas and surface flames than those of pine. The surface flames of the untreated poplar specimens also took a longer time (up to 14 s) to extinguish after the fire source was removed. Similarly, modern treatment poplar specimens (Po-R) took a longer time to burn on the surface when subjected to fire and the flames were generally smaller than the non-treated ones. Upon removal of the fire source, the residual surface flame of the poplar specimens persisted longer than the pine specimens by around 8.5 s.
Although the traditional- and combined-treated specimens (T and RT groups) showed slightly different burning patterns, some general similarities can still be drawn. During the burning process, a cluster of flames was generally formed on the surface of the specimens, which first turned black and then gradually formed a white crust-like substance in the area that was subjected to the fire. Hence, the traditional- and combined-treated methods tend to delay the burning of the inner wood due to the insulation layer of the treated surface material. Another point to note is the fumes produced from the traditional- and combined-treated specimens. As the basic ingredients of the traditional method consist of certain insect-repellent chemicals that are essentially toxic, poisonous fumes, such as carbon monoxide, carbon dioxide, and lead oxide, are often produced during the burning, which in turn cause harm to humans in the long run.

3.2. Charring Characteristics

From the lateral view, video camera 2 recorded the distinctive depression development of the wood specimen after being subjected to fire (Figure 5a), and the cross-sections of the specimens subjected to fire are presented in Figure 5b. Using a burnt pine specimen as an example, interpretation of the cross-sectional illustration is presented in Figure 6, where the dashed line represents the initial outline of the specimen before burning, the black portion shows the remaining charred layer, and the grey part represents the unaffected part (cool part) after the fire test. All the cross-sections of 24 test specimens were traced and measured in this manner for the subsequent calculations and analysis. The cross-sections of the burnt test specimens are shown in Table 6.
The charring rate is calculated by the division of the maximum charring depth (measured from the cross-section of the burnt specimen) by the burning duration. Detailed test data are presented in Table 7. The charring data of the test specimens were averaged and analyzed, as shown in Figure 7. From Table 6, the average charring rate of untreated pine and poplar when subjected to the 5 min fire test was 2.7 mm/min and 3.6 mm/min, respectively, while the charring rate of untreated pine and poplar for the 10 min test was 2.2 mm/min and 3.0 mm/min, respectively (Table 7). It is evident that compared to poplar, pine generally has a lower charring rate when subjected to fire and thus better fire properties. This corresponds well with the observation of larger flames on the surface of poplar specimens during the fire tests, as shown in Table 5.
In the case of surface treatments, all three methods generally improve the fire properties for both types of wood by exhibiting a decreasing trend in charring depth and rate (Table 7 and Figure 7). The fire properties of pine are generally enhanced, particularly by the traditional method, while the combined method does not further enhance but reduces the fire properties of the wood. The combined method may result in an excessively thick coating, which affects the adhesion and stability of fire-retardant coatings. Excessively thick coatings may be more likely to crack or flake at high temperatures, resulting in exposure of the wood to flames, thus reducing fire resistance.

3.3. Surface Temperature Variations

The surface temperature variations in the specimens were recorded by a thermographic camera. The average temperature was collected and recorded frame by frame (one frame per second) for the area of the specimen affected during the fire test by “Thermotools V4.0”, as shown in Figure 8, where red areas indicate high temperatures and blue areas indicate low temperatures. Figure 9 shows the surface temperature change curve of the specimens. To see the temperature trend more clearly, the curve was smoothed by Origin® 2019 software, using the LOWESS smoothing method with the bandwidth set as 0.21. The shaded area is the standard deviation of the original data from the smoothed data, indicating the range of fluctuations.
For pine specimens, the surface temperature initially rises first and later stabilizes around 680 °C at about 300 s, after which, the surface temperatures for the three treatments were generally lower than the untreated specimen (Pi-N). The reduced temperature for the traditional method (Pi-T) appeared to be the most distinct from the other two treatments, where the final temperature of 490 °C was recorded at the end of the test (600 s). This lowered temperature trend could be due to the thick traditional coating on the external surface that helps to insulate the heat from entering the interior. The modern method is effective in slowing down the initial stage of temperature rise as the temperature peak arrives later at around 400 s but ends around 650 °C, thus implying that the effectiveness of the chemical barrier might have worn off after reaching the threshold of around 400 s. The combined method, on the other hand, showed little effect on reducing the surface temperature of the wood; hence, the combined treatment does not apply in the pine case.
The surface temperature of untreated poplar is generally higher than that of pine, reaching a peak temperature of 770 °C. In the case of the modern method, the effectiveness of the modern chemical barrier is fairly consistent with the pine specimens, with a slightly lower surface temperature measured than the pine specimens during the stabilized stage. Similarly, the reduced temperature effect as observed for the traditional method after 300 s is very distinct, while the combined method is essentially similar to the untreated specimen.

4. Conclusions

This study investigates the fire properties of pine and poplar wood when subjected to three types of surface treatments. The charring rate and the surface temperature variation in the wood were recorded by means of the single-sided fire test to assess the vulnerability to fire and the effect on the surface temperatures, respectively. The aim is to provide a scientific basis for the selection of coatings for fire prevention in the future restoration of ancient buildings.
The results show that pine has better fire properties than poplar, so it is recommended to use pine for future restoration work under the comprehensive consideration of the structural resistance and moisture content. The Chinese traditional coating method shows good fire properties of wood and exhibits lower surface temperature, which effectively slows down the rise in the surface temperature during a fire. However, due to its insect-repellent toxic properties, an unpleasant and toxic smell was produced when exposed to fire. Another disadvantage of the Chinese traditional coating method is that it is a very complex and time-consuming process.
Although the modern flame-retardant method is generally less fire-resistant than the traditional method, it has the advantage of a shorter application period and generally has little effect on the color of the existing wood upon application. Thus, it is an effective alternative, especially for historic timber buildings that are not restricted by conservation protection status and do not require the application of the traditional coating.
In summary, historic timber buildings that were initially traditionally treated should be repaired by the original method, while buildings that previously did not have any treatment are recommended to be treated with the colorless modern treatment, especially on the surfaces of large timber elements. It is hoped that the results obtained from this study could help to provide a more scientific basis for the selection of coatings for fire prevention in the future restoration of ancient Chinese timber buildings.

Author Contributions

Conceptualization, Y.L., S.D. and S.Y.; methodology, S.D. and S.Y.; validation and formal analysis, Y.L. and S.Y.; investigation, Y.L. and S.Y.; writing—original draft preparation, Y.L.; writing—review and editing, S.Y.; supervision, S.Y.; funding acquisition, S.D. and S.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Key Laboratory of Ecology and Energy Saving Study of Dense Habitat, Ministry of Education, grant number 20220105.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Photographs of the wood specimens.
Figure 1. Photographs of the wood specimens.
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Figure 2. Overview of the traditional coating treatment. (a) Filling the fine cracks with sawdust and lime plaster mix. (b) Second coating of plaster, followed by surface polishing. (c) Binding hemp using plaster, followed by surface polishing. (d) Continual press layering and polishing of the hemp plaster for a few more rounds.
Figure 2. Overview of the traditional coating treatment. (a) Filling the fine cracks with sawdust and lime plaster mix. (b) Second coating of plaster, followed by surface polishing. (c) Binding hemp using plaster, followed by surface polishing. (d) Continual press layering and polishing of the hemp plaster for a few more rounds.
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Figure 3. Photographic record and RGB value change in the specimens’ surfaces.
Figure 3. Photographic record and RGB value change in the specimens’ surfaces.
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Figure 4. The schematic layout of the single-sided fire test.
Figure 4. The schematic layout of the single-sided fire test.
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Figure 5. Depression of wood after burning.
Figure 5. Depression of wood after burning.
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Figure 6. Explanatory for a typical specimen’s cross-section after fire test.
Figure 6. Explanatory for a typical specimen’s cross-section after fire test.
Buildings 14 02439 g006
Buildings 14 02439 g007
Figure 7. Average charring rate of pine and poplar specimens under various treatments.
Figure 7. Average charring rate of pine and poplar specimens under various treatments.
Buildings 14 02439 g007
Buildings 14 02439 g008
Figure 8. Analysis of the infrared temperature.
Figure 8. Analysis of the infrared temperature.
Buildings 14 02439 g008
Buildings 14 02439 g009
Figure 9. Surface temperature curve of pine (left) and poplar (right) specimens under various treatments.
Figure 9. Surface temperature curve of pine (left) and poplar (right) specimens under various treatments.
Buildings 14 02439 g009
Table 1. RGB value of the specimens’ surfaces.
Table 1. RGB value of the specimens’ surfaces.
Wood SpeciesStageRGB Value
RGB
PineBefore164157151
After145135124
PoplarBefore157151137
After172163137
Table 2. Details of the test specimens.
Table 2. Details of the test specimens.
Wood SpeciesDimensionTypes of Surface TreatmentSpecimen Numbering
Pine∅100 × 400 mmNo treatment (control)Pi-N-1
Pi-N-2
Pi-N-3
ModernPi-R-1
Pi-R-2
Pi-R-3
TraditionalPi-T-1
Pi-T-2
Pi-T-3
CombinedPi-RT-1
Pi-RT-2
Pi-RT-3
Poplar∅100 × 400 mmNo treatment (control)Po-N-1
Po-N-2
Po-N-3
ModernPo-R-1
Po-R-2
Po-R-3
TraditionalPo-T-1
Po-T-2
Po-T-3
CombinedPo-RT-1
Po-RT-2
Po-RT-3
Table 3. Moisture content (MC) difference before and after treatment for the test specimens.
Table 3. Moisture content (MC) difference before and after treatment for the test specimens.
Wood
Species		Individual
MC without Treatment		Average
MC without Treatment		Treatment
Type		Individual
MC after Treatment		Average MC after TreatmentAverage MC
Difference
after Treatment
Pine12.1%10.2%Modern17.2%16.9%+6.7%
17.1%
16.4%
8.8%Traditional8.9%8.7%−1.5%
8.5%
8.7%
9.6%Combined8.8%8.7%−1.5%
8.5%
8.7%
Poplar7.4%8.2%Modern15.1%14.4%+6.2%
13.4%
14.8%
9.2%Traditional7.6%7.0%−1.2%
5.8%
7.6%
8.0%Combined7.1%7.4%−0.6%
7.2%
7.8%
Table 4. The burning process of the pine test specimens under various treatments.
Table 4. The burning process of the pine test specimens under various treatments.
TreatmentTime Recorded after Fire IgnitionT
10 s30 s60 s300 s600 s
Pi-N
(Control)		Buildings 14 02439 i0013.6 s
Pi-R
(Modern)		Buildings 14 02439 i0020.6 s
Pi-T
(Traditional)		Buildings 14 02439 i0032.3 s
Pi-RT
(Combined)		Buildings 14 02439 i0044.3 s
Note: T—total time duration for the surface flame to completely extinguish after the fire source was removed.
Table 5. The burning process of the Poplar test specimens under various treatments.
Table 5. The burning process of the Poplar test specimens under various treatments.
TreatmentTime Recorded after Fire IgnitionT
10 s30 s60 s300 s600 s
Po-N
(Control)		Buildings 14 02439 i00514.0 s
Po-R
(Modern)		Buildings 14 02439 i0069.1 s
Po-T
(Traditional)		Buildings 14 02439 i00716.0 s
Po-RT
(Combined)		Buildings 14 02439 i00827.0 s
Note: T—total time duration for the surface flame to completely extinguish after the fire source was removed.
Table 6. Cross-sectional illustrations of pine and poplar specimens after fire tests.
Table 6. Cross-sectional illustrations of pine and poplar specimens after fire tests.
Wood
Species		No TreatmentModern TreatmentTraditional TreatmentCombined Treatment
PineBuildings 14 02439 i009Buildings 14 02439 i010Buildings 14 02439 i011Buildings 14 02439 i012
Pi-N-1Pi-R-1Pi-T-1Pi-RT-1
Buildings 14 02439 i013Buildings 14 02439 i014Buildings 14 02439 i015Buildings 14 02439 i016
Pi-N-2Pi-R-2Pi-T-2Pi-RT-2
Buildings 14 02439 i017Buildings 14 02439 i018Buildings 14 02439 i019Buildings 14 02439 i020
Pi-N-3Pi-R-3Pi-T-3Pi-RT-3
PoplarBuildings 14 02439 i021Buildings 14 02439 i022Buildings 14 02439 i023Buildings 14 02439 i024
Po-N-1Po-R-1Po-T-1Po-RT-1
Buildings 14 02439 i025Buildings 14 02439 i026Buildings 14 02439 i027Buildings 14 02439 i028
Po-N-2Po-R-2Po-T-2Po-RT-2
Buildings 14 02439 i029Buildings 14 02439 i030Buildings 14 02439 i031Buildings 14 02439 i032
Po-N-3Po-R-3Po-T-3Po-RT-3
Table 7. Key data of the pine and poplar specimens after the fire tests.
Table 7. Key data of the pine and poplar specimens after the fire tests.
Specimen
Number		Average
MC after Treatment
(%)		Burning
Duration
(min)		Charring
Depth
(mm)		Charring
Rate
(mm/min)		Mass Before Test (m0)
(g)		Mass after Test (m1)
(g) 		Mass
Loss (∆m)
(g)
Pi-N-1 516.03.21015.2992.822.4
Pi-N-210.2510.52.11116.41106.310.1
Pi-N-3 1022.02.21126.71073.353.4
Pi-R-1 510.02.0870.2864.85.4
Pi-R-216.9510.02.0858.9853.95.0
Pi-R-3 1013.01.31133.71119.414.3
Pi-T-1 52.00.415981590.87.2
Pi-T-28.753.50.71213.61208.65.0
Pi-T-3 108.00.81439.51429.410.1
Pi-RT-1 58.51.71424.01410.413.6
Pi-RT-28.754.50.91192.01187.94.1
Pi-RT-3 108.00.81368.51345.722.8
Po-N-1 516.03.21010.0985.224.8
Po-N-28.2520.04.01015.5991.723.8
Po-N-3 1030.03.01013.3958.754.6
Po-R-1 513.52.71116.11105.910.2
Po-R-214.4512.02.41005.7993.712.0
Po-R-3 1020.02.01119.01102.916.1
Po-T-1 57.01.41522.71506.516.2
Po-T-27.059.01.81306.6129313.6
Po-T-3 1010.01.01592.61582.919.7
Po-RT-1 510.02.01376.01363.112.9
Po-RT-27.4511.02.21430.91419.811.1
Po-RT-3 1017.01.71372.51353.219.3
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Li, Y.; Yeo, S.; Dai, S. A Comparative Study of the Fire Properties of Chinese Traditional Timber Structural Components under Different Surface Treatments. Buildings 2024, 14, 2439. https://doi.org/10.3390/buildings14082439

AMA Style

Li Y, Yeo S, Dai S. A Comparative Study of the Fire Properties of Chinese Traditional Timber Structural Components under Different Surface Treatments. Buildings. 2024; 14(8):2439. https://doi.org/10.3390/buildings14082439

Chicago/Turabian Style

Li, Yupeng, Sokyee Yeo, and Shibing Dai. 2024. "A Comparative Study of the Fire Properties of Chinese Traditional Timber Structural Components under Different Surface Treatments" Buildings 14, no. 8: 2439. https://doi.org/10.3390/buildings14082439

APA Style

Li, Y., Yeo, S., & Dai, S. (2024). A Comparative Study of the Fire Properties of Chinese Traditional Timber Structural Components under Different Surface Treatments. Buildings, 14(8), 2439. https://doi.org/10.3390/buildings14082439

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