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After fire in buildings investigators start research. The purpose of it is to find the reason of fire, but this thing can be reliably determined only if the fire origin is fixed. The instrumental fire prognosis for wooden structures is currently the most widely applied method in Lithuania. But the analysis of charring of natural wood specimens and...
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... According to NFPA 921: 2017 [18], the charring rate of wood under laboratory conditions and exposure to a heat source from one side is determined from 0.17 mm•min −1 to 4.23 mm•min −1 . Lipinskas and Mačiulaitis [51] investigated the charring of fir samples treated with various kinds of retardant using different test equipment. Using a heating chamber, they determined the charring rate of selected coniferous tree species, ranging from 0.6 to 1.1 mm•min −1 . ...
The paper assesses the influence of the heat flux on spruce wood (Picea abies L.) behavior. The heat flux was performed at 15, 20, 25, and 30 kW•m −2. The fire-technical properties, such as the mass burning rate, charring thickness, charring rate, as well as the chemical composition (contents of the extractives, lignin, cellulose, holocellulose), of wood were determined. The highest burning rate of spruce wood of 0.32 %•s −1 was reached at the heat flux of 30 kW•m −2. The charring rate ranged from 1.004 mm•min −1 (15 kW•m −2) to 2.016 mm.min −1 (30 kW•m −2). The proposed model of the charring process of spruce wood in time and appropriate thickness as a selected parameter is applicable in validation of the results of computer fire models in the design of fire protection of wooden buildings. The decrease in the holocellulose content mostly caused by the degradation of hemicelluloses was observed during thermal loading. The biggest decrease in hemicelluloses (24.94%) was recorded in samples loaded at 30 kW•m −2. The contents of cellulose increased due to the structural changes (carbonization and crosslinking), the content of lignin increased as well due to its higher thermal stability compared to saccharides, as well as the resulting lignin condensation.
... Le front de pyrolyse en surface en fonction du temps d'expositionà 30 kW aégalementété mesuré. Lipinskas et Mačiulaitis [135] ont réalisé des tests au SBI afin de comparer la vitesse de carbonisation de différentséchantillons de bois (feuillus et résineux, traités et non traités). Ils ont montré que cette vitesse pouvait passer de 0,5à 0,8 mm. ...
La construction de bâtiments à énergie positive et à faible empreinte carbone constitue une véritable réponse aux enjeux et défis environnementaux de ces prochaines décennies. Un point clé pour la réalisation de tels bâtiments est le comportement au feu de ces ouvrages. En effet, lorsque le bois est soumis à une sollicitation thermique, celui-ci va se dégrader, voire même s’enflammer et, lorsque les conditions le permettent, s’éteindre. Cependant, l’état de l’art actuel met en évidence la disparité des résultats expérimentaux sur un même matériau soumis à un essai donné comme le cône calorimètre par exemple. L’objectif de la thèse présentée ici est d’appréhender expérimentalement l’auto-inflammation, la dégradation et l’auto-extinction du matériau bois utilisé dans les bâtiments. Pour cela, de nombreux essais à différentes échelles ont été effectués afin d’étudier la capacité du matériau bois à s’enflammer ou à s’éteindre de lui-même selon des conditions prescrites. Au total, 600 tests ont été effectués en orientation verticale et permettent de conforter les résultats avec une approche statistique. Une métrologie dédiée a été mise en place et a été déployée sur chaque dispositif expérimental étudié : une caméra infrarouge permettant d’obtenir la température de surface des échantillons lorsqu’ils sont soumis à une sollicitation thermique, deux caméras rapides (visible et infrarouge) pour filmer la localisation et les mécanismes d’auto-inflammation et des thermocouples très fins encastrés dans le bois de façon à mesurer l’évolution de la température dans le matériau selon des conditions fixées. Les travaux menés ont montré que pour l’auto-inflammation, la notion de température d’inflammation du matériau pouvait être discutable lorsque l’inflammation se produit à des temps courts. En effet, l’apparition de la flamme se situe alors, dans la majeure partie des expériences, à une distance éloignée de la surface exposée à la sollicitation thermique. Les mécanismes d'apparition de la flamme ne dépendent alors pas de la température de surface mais des conditions de mélange gaz/air ainsi que de la température de ce mélange. La température de surface à l'auto-inflammation n’a donc de sens que pour des temps d'auto-inflammation longs, pour lesquels l’inflammation se produit à proximité de la surface. La dégradation des échantillons dépend de nombreux facteurs. L’effet de certains de ces paramètres a été considéré dans ce travail. Une attention particulière a été portée sur la mise en place d’une métrologie visant à obtenir des mesures précises et fiables. Des thermocouples très fins, noyés dans l’échantillon et orientés parallèlement aux isothermes permettent une meilleure estimation de la température et ont donc été utilisés. Enfin, un nouveau dispositif expérimental basé sur deux cônes calorimètres disposés sur un système de table coulissante a été mis en place et a permis de déterminer des critères simples d’auto-extinction du bois à petite l’échelle.
... In view of the very little research information available on the fire safety of bamcrete wall panels, present work is focused on the determination of the behavior of single mesh bamcrete wall panel at elevated temperature. It has been reported in various studies that wood/bamboo starts charring at a temperature of about 300°C [9,10]; hence, in this research, to study the behavior of bamcrete panel a maximum of 400°C temperature was considered. The weight-loss and mechanical strength of bamcrete wall panels at 100°C, 200°C, 300°C, and 400°C was analyzed for a fixed time duration. ...
With the development of technology, mud plaster has been replaced by cement plaster for supporting bamboo mesh in wall panels and known as ekra wall or bamcrete wall. Usually, low grade mortar is used in making the bamcrete wall, while the latest studies have used high strength mortar. Bamboo burns through pyrolysis process like wood when it is exposed to the fire condition. Fire safety is one of the major challenges for the construction industry to use the bamcrete wall panel. In the present study, performance of bamboo reinforced panels at elevated temperature is presented. Bamboo strips were inter-woven and protected by the cement mortar. The weight-loss and loss of mechanical strength of wall panel has been studied at 100 ℃, 200 ℃, 300 ℃, and 400 ℃ maintained for a fixed time period.
... The one-sided heating in the furnace properties of specimens was determined according to LST EN 1363-1: 2012. In order to determine the peculiarities of plastered wood at evaluated temperatures, a special one-sided heating chamber was used according to sources 19,20 . This equipment can simulate the one-sided heating of the test sample from 20 °C to 950 °C. ...
Currently, the production of green building materials grows up. Alkali-activated materials (AAMs) based plaster have better fire resistance properties compared to Portland cement-based concrete and plasters. Compared to Portland cement-based systems AAMs retain a significant level of structural stability after exposure to fire events. AAM based concrete doesn’t have at all or has an insignificant amount of calcium hydroxide in the binder structure which exposed to high-temperature changes to calcium oxide. This weakens Portland cement structural properties and allows cracks to appear under high-temperature conditions. This study shows that AAM based plaster that consisted of alkali-activated ground granulated blast furnace slag (slag) with the addition of Phosphogypsum (PG), sand and polypropylene fibre filling exposed to 1000 °C temperature shows up to 2% longitudinal dimension shrinkage. After exposure of elevated temperature these fibers melted leaving a network of channels that allow water vapour vaporize and inner pressure in the material decreased. The start of the wood surface charring process tch is 10 minutes after the start of heating. Using an AAM binder as fire-resistant plaster coating on a wooden structure delays the start of the char layer forming on the wood surface. This allows using AAMs base plaster for fire-resistant coatings on combustible materials as the barrier layer in order to increase the passive safety of wooden structures in heritage buildings.
... Lipinskas and Mačiulaitis [37] used a one-side heating equipment and the Single Burning Item (SBI) test to show how charring samples can be used for prediction of the onset of fire. Copyright Cedering [38,39] investigated the effects of density, moisture content, and oxygen concentration on the charring rate of Norway spruce. ...
... The density of wood drops to about 90% of its original value when the temperature exceeds 100 • C, and to about 20% of its original value when the wood is converted to char above 300 • C [3]. It is widely accepted by researchers that the charring rate decreases with increasing density; Schaffer [15], Hadvig [17], Mikkola [13], White and Nordheim [23], Buchanan [3], Kodur and Harmathy [45], Lipinskas and Mačiulaitis [37] and Yang et al. [42]. Because charring involves the thermal degradation of wood mass, the charring rate is slower when there is greater mass to degrade. Figure 4 from [15] shows the charring rate for Douglas fir as a function of density and moisture ratio when exposed to ASTM standard fire. ...
... Janssens [5] found a difference in the mass loss rate, heat release rate and heat of gasification for softwoods and hardwoods, and related it to the higher lignin content in softwoods. Lipinskas and Mačiulaitis [37] found a difference between the charring rate of softwood and hardwood, where softwood had a charring rate of 0.8-0.9 mm/min, and hardwood had a rate of 0.5-0.6 mm/min. ...
In fire design of timber structures the charring rate of the material is a very important property, but the charring rate varies with the conditions in the fire compartment and the characteristics of the wood. Many experiments have been carried out through the years, trying to determine the effect of various properties on the charring rate of wood. This paper gives a summary of the material properties and external factors found in the literature to have the largest influence on the charring rate of exposed wood, i.e. the density, moisture content, chemical composition, grain orientation, permeability, scale effect, thermal exposure, char contraction, char oxidation, oxygen concentration and opening factor, resulting from experiments found in the literature. It has not been possible to determine which properties or factors have the most significant influence on the charring rate of wood, due to large differences between the test conditions and methods, wood species and measurement methods. There is a great need for further testing to determine the relative effect of these properties and factors, and international test methods need to be developed to enable comparison of results from research all over the world. More information about the most important properties and factors can help standardise the calculation of charring of wood, and improve the input to computer models for fire safety design. This will result in more economic fire design of wooden structures, as the calculated residual cross sections will be closer to reality. Copyright © 2010 John Wiley & Sons, Ltd.
... Metodas gali būti naudojamas kaip palyginamasis, norint įvertinti priešgaisrinių elementų termoizoliacines savybes; nustatyti ir kontroliuoti priešgaisrinių termoizoliacinių medžiagų kūrimą, gamybą ir panaudojimą; nustatyti medžiagų termoizoliacinių savybių pokytį nuo senėjimo. Temperatūra krosnyje palaikoma ir pagal šią priklausomybę (Lipinskas 2005): ...
The problem of the resistance to fire of metal constructions is examined and different fire resistance furnaces are overviewed. Testing conditions and testing methods by which the elements were tested resistance to fire were performed and provided.
The article describes the behaviour of different fireproof materials during the tests and it analyzes the influence of different heating conditions to element’s fire resistance class. The tests’ results, findings, advices are also included.
Santrauka
Darbe nagrinėjama metalinių konstrukcijų atsparumo ugniai problema. Apžvelgta skirtinga atsparumo ugniai nustatymo įranga. Pateikiamos sąlygos, kuriomis buvo atliekami atsparumo ugniai bandymai su skirtingais elementais. Nagrinėjama skirtingų priešgaisrinių apsaugos medžiagų reakcija bandymo metu ir analizuojama, kaip skirtingos klimatobei aplinkos sąlygos gali lemti elementų atsparumo ugniai klasę. Pateikiami atliktų bandymų rezultatai, atlikta išsami rezultatų analizė, pateiktos išvados.
Raktiniai žodžiai: atsparumas ugniai, plieninė konstrukcija, temperatūros ir laiko kreivė, apsauginė medžiaga
... Since Lithuanian environmental control agencies have detected no emissions of industrial pollutants over the period under investigation, and since there are no potential pollution sources of this type near smaller rivers (like the Žeimena or the Merkys), possibility of industrial emissions is minimal. However, burning is also a potential source of heavy metals that can be released into the atmosphere through volatilization trapped in smoke particles or distributed as fly ash after combustion [26,27]. Agricultural emissions are unlikely because in July and August no use is made of fertilizers or other bilizes heavy metals until a change in redox or pH occurs [32,33]. ...
Comparison of long-term environmental monitoring data show that in August and September 2002 heavy metal (Cu, Pb and Zn) concentrations increased in Lithuanian rivers. Resent investigation has indicated that increase of heavy metals (Cu, Pb and Zn) by 60–81 % in all the rivers that are subject to the State River Monitoring and could be correlative with land fires. Fires of forests and peat bogs have outspread all over Lithuania in the summer and the first half of autumn of 2002. This paper attempts to prove an assumption that these fires could have caused a significant increase of heavy metal concentrations in the water of Lithuanian rivers in August 2002. It also means that land fires should be evaluated as an environmental risk factor with a serious impact on the state of aquatic environment and must be taken into account in calculations of environmental damage.
... Since Lithuanian environmental control agencies have detected no emissions of industrial pollutants over the period under investigation, and since there are no potential pollution sources of this type near smaller rivers (like the Žeimena or the Merkys), possibility of industrial emissions is minimal. However, burning is also a potential source of heavy metals that can be released into the atmosphere through volatilization trapped in smoke particles or distributed as fly ash after combustion [26,27]. Agricultural emissions are unlikely because in July and August no use is made of fertilizers or other bilizes heavy metals until a change in redox or pH occurs [32,33]. ...
Comparison of long‐term environmental monitoring data show that in August and September 2002 heavy metal (Cu, Pb and Zn) concentrations increased in Lithuanian rivers. Resent investigation has indicated that increase of heavy metals (Cu, Pb and Zn) by 60–81 % in all the rivers that are subject to the State River Monitoring and could be correlative with land fires. Fires of forests and peat bogs have outspread all over Lithuania in the summer and the first half of autumn of 2002. This paper attempts to prove an assumption that these fires could have caused a significant increase of heavy metal concentrations in the water of Lithuanian rivers in August 2002. It also means that land fires should be evaluated as an environmental risk factor with a serious impact on the state of aquatic environment and must be taken into account in calculations of environmental damage.
The aim of this work is to study and characterize the fire behavior of vertically oriented spruce wood panels using experiments conducted at the scales of cone calorimeter and single burning item tests. For this purpose, first incombustible panels were exposed to burner powers of 15, 20, 30, and 50 kW in the single burning item tests to obtain a mapping of the total heat fluxes received by the panel. Subsequently, wood panels were exposed to the same burner powers for exposure times of 15, 20, and 30 min. Very thin thermocouples were embedded inside the wood panel to measure accurately the in-depth temperatures while the lateral position of the char front on the exposed surface and the depth of the char layer were also measured for each test. The latter measurement permitted to establish a char depth map according to the burner power and exposure time. Correspondingly, it was observed that for a fixed exposure time, the degraded area on the surface grows linearly with the burner power. Moreover, the in-depth char front position deduced from the 300 °C isotherm was found to comply very well with that obtained from direct measurements. Finally, a comparison is made between the char front depths measured with the single burning item and those measured with the cone calorimeter for similar heat fluxes, showing that the corresponding charring rates from these two tests deviate from one another only at low heat fluxes.
Introduction. The article presents the results of a research on the two stages of thermal decomposition of timber. The first stage of thermal decomposition is flame combustion, which is followed by a transition to flameless combustion due to the formation of a char layer on the surface of wood. The flameless process is accompanied not only by heterogeneous combustion, but, at least, three reactions: pyrolysis, thermal oxidative destruction of wood and oxidation of resulting coke. Goals and objectives. The goal is to identify the criteria of charring and heat release under the influence of an external radiative heat flux on samples of coniferous and deciduous species of wood using a standard flowthrough calorimeter with a focus on flameless combustion. Methods. A standard OSU flow-through calorimeter, produced by Atlas (USA), was used to identify heat release characteristics under the influence of external radiative heat fluxes that had the density of 20, 35 and 52 kW/m ² . The lower limit of heat, released in the complete combustion of samples, that had a char layer, was identified using bomb calorimeter C-5000. Results. The co-authors analyzed the charring process and characteristics of heat release using samples of wood species that were 10 and 25 cm thick. Wood samples were exposed to combustion under the influence of an external radiative heat flux that had the density of 20, 35 and 52 kW/m ² subsequent to the results of tests, conducted using the OSU calorimeter. The co-authors evaluated the charring velocity and the coke layer thickness for the cases of flame and flameless combustion; efficient combustion heat release and the combustion completeness coefficient, as well as the sample shrinkage. The co-authors demonstrated that a transition from flame combustion to heterogeneous combustion occurs upon completion of the quasi-neutral burning of wood samples, which corresponds to the final point of heat release velocity curves and marks a transition from the behaviour of a thermally thick material to that of a thermally thin material. Conclusion. The obtained experimental data allow to forecast a change in the physical and heat engineering properties, characteristics of heat release in the processes of flame and flameless combustion of different wood species with account taken of the char layer formed on its surface under the influence of various heat fluxes.
