Small-scale Fire Tests Research Articles

Preparation of fully physically crosslinked double-network gel and its fire prevention mechanism

It is important to gain an in-depth understanding of the structure of fire prevention and extinguishing materials during self-heating of coal. In this paper, an Al3+-CMC/PAM-MMT fire prevention and extinguishing gel with double-network was prepared using sodium carboxymethyl cellulose (CMC) and polyacrylamide (PAM) as raw materials, and aluminum citrate (AlCit) and sodium montmorillonite (Na-MMT) as auxiliary materials, by introducing the fully physically crosslinking effect. The optimal amounts of CMC, PAM, AlCit and MMT were determined to be 2 %, 3 %, 8 %, and 3 %, respectively, based on gelation time, stability, and resistance of the gel. The micromorphological image of the double-network gel exhibited a laminar structure of parallel-aligned fibrous networks, where the pores and channels exhibited more complex shapes and became smaller in size, highlighting the superiority of the double-network architecture. The rheological tests showed that the double-network gel had superior structural stability and viscosity under varying shear rates, making it more effective in covering the fire source, enhancing extinguishing efficiency. Additionally, its higher storage and loss moduli indicated stronger elasticity and mechanical properties compared to the single-network gel, emphasizing its advantages in energy storage and recovery. The characterization of active functional groups showed that there was an effective suppression of reactions involving hydroxyl, hydrocarbon, and carbonyl functional groups, during the spontaneous combustion process of coal, following treatment with the gel. Additionally, a proposed mechanism for the gel formation was presented. In the sealing performance test, the pressure-bearing capacity of the double-network gel was approximately twice that of the single-network gel. It indicated that the multi-level structure formed by the gel led to higher density of physical cross-linking points, which provided better sealing performance. Thermogravimetric analysis showed significant decrease in total calorific value and increase in activation energy of coal, after treatment with the gel, rendering it more difficult for spontaneous coal combustion. In the small-scale fire extinguishing performance test, the double network of Al3+-CMC/PAM-MMT gel demonstrated effective suppression of spontaneous combustion of coal and reduced the susceptibility to re-ignition. The fire prevention mechanism of the gel was further explored experimentally.

Enhancing the fire resistance of light gauge steel framed floor-ceiling systems through external insulation

Light Gauge Steel Framed (LSF) floor-ceiling systems, composed of thin-walled cold-formed steel (CFS) structural components, offer a high strength-to-weight ratio and cost-effectiveness, leading to their widespread adoption in modern construction. However, research on the fire behaviour of LSF floor-ceiling systems is limited. The industry-standard approach of using two 16 mm gypsum plasterboards for ceilings achieves a maximum Fire Resistance Level (FRL) of 90 min, mainly due to the significant fall-off associated with gypsum plasterboard. Traditional methods for increasing FRL involve adding more layers of gypsum plasterboard; however, the efficacy of achieving a 120-min FRL with three 16 mm gypsum plasterboards remains uncertain. This paper addresses these issues by developing innovative LSF floor-ceiling systems that incorporate external insulation (rigid stone wool) to mitigate the impact of critical ceiling fall-off behaviour and enhance FRL. The research includes dimensional stability tests of rigid stone wool, thermal and structural finite element modelling, and load-bearing small-scale fire tests. The new LSF floor-ceiling system has been shown to achieve an FRL of 130 min, approximately 45 % higher than conventional floor-ceiling systems, offering enhanced fire resistance and increased thermal comfort as a single, integrated solution.

Large- and small-scale fire test of a building integrated photovoltaic (BIPV) façade system

The number of installed photovoltaic (PV) modules has increased significantly over the last years, and using available building surfaces to generate electricity by integrating PV modules in the construction is an attractive option. Building integrated photovoltaics (BIPV) or other vented claddings can spread fires rapidly to large parts of a building if the fire is allowed to propagate. To investigate this hazard, a large-scale SP FIRE 105 façade fire test was conducted. A façade measuring 4000 mm × 6000 mm covered with BIPV modules was exposed to flames that represent the fire plume from a window in a room at flashover. The results from the test show that critical failures, like falling objects and vertical flame propagation, can be expected in such constructions. These results highlight the importance of details in mounting of BIPV-façades and to require proper documentation from relevant fire tests of such systems. Small-scale cone calorimeter tests were conducted on the studied BIPV module to provide material properties of the combustible parts of the installation. These aspects should be considered when planning new or when retrofitting façades, to prevent escalation of fires. The results presented are, however, only valid for the configuration that was tested. Other BIPV-façades should also be investigated to study how these constructions can be built safely in the future with regard to critical details.

Study on the performances of fire-resistive engineered cementitious composites (ECCs)

The high ductility of fire-resistive engineered cementitious composites (ECC) makes it possess better cohesive performance than the traditional cement-based fireproof material, and improves the cracking and delamination between the fireproof material and the substrate material. In this paper, the tensile and compression properties, dry density, heat insulation properties, and high temperature resistance of the prepared fire-resistive ECC materials were systematically studied, and the heat transfer behavior in the heating process was studied by means of small-scale fire resistance test. The results demonstrate that the prepared fire-resistive ECC materials possess both the favorable thermal insulation properties and adequate mechanical properties. Meanwhile, compared with traditional cementitious fireproof materials, better high temperature stability of prepared fire-resistive ECC avoids the failure due to the deterioration of mechanical properties during heating process. Then the reduction of temperature rising rate and equilibrium temperature shown in small-scale fire resistance experiments verifies that it can effectively improve the fire performance of the structure under actual fire. Finally, with the help of microscopic experiments the action mechanism of the porous fillers on the ductility and fire performance of fire-resistive ECC materials were explored.

Fire resistance evaluation of gypsum plasterboard walls using machine learning method

Gypsum plasterboard walls are commonly used in constructions and they provide the passive fire protection as separating elements. The fire resistance of the wall is largely dependent on the thermo-mechanical properties of the gypsum plasterboard. Numerical modelling of the fire behaviour of gypsum plasterboard cracking, fall-off and gypsum induced water transport is a great challenge. The fire resistance of the wall is assessed by performing expensive fire tests or conservative empirical calculations. This paper presents the evaluation of fire resistance of steel stud gypsum plasterboard lined walls by means of machine learning. A series of large, medium and small scale fire tests are performed or gathered on the gypsum plasterboard walls in order to create a data base. Various tracks are considered when using machine learning in order to predict the failure times and the temperature evolution on the unexposed side of these walls. The machine learning results are compared with test results, with the separating function method and finite element method results.

Experimental study on fire characteristics in cable compartment of utility tunnel with natural ventilation.

The fire characteristics under natural ventilation in the cable compartment of the utility tunnel are studied. A series of small-scale fire experimental tests are conducted to obtain the maximum temperature below the ceiling of different ignition vertical heights and cable types. In this paper, the ceiling temperature decay and heat release rate (HRR) are studied in the cable compartment of utility tunnel. Through experimental tests, the fire characteristics of placing the fire source on the near wall side 3.0 m away from the shaft of the utility tunnel cable compartment are studied. The results showed that under the action of natural ventilation, with the decrease of fuel quantity, the mass loss of cable decreases, and the maximum temperature below the ceiling of the cable compartment in the utility tunnel decreases. ZRYJV cables burn more sufficient combustion than RVVR cables. A new empirical association for total HRR is proposed. Those experimental test results are used as validation data for the newly proposed empirical correlation of total HRR. This paper hopes to provide some basic fire safety references for the utility tunnel planning of the urban underground cable compartment.

Effects of insulation materials and their location on the fire resistance of LSF walls

Lightweight walls incorporate insulation materials to compensate for their low thermal mass and to improve thermal performance. This helps in increasing the energy performance of the buildings. Since insulation materials are sensible heat storage materials, there is an increment in the room temperature. Phase Change Materials (PCMs) are used in lightweight walls due to their high thermal storage capacity and the resulting enhanced thermal comfort levels. However, the performance of the PCM incorporated building products/insulations in fire has not been investigated yet. This research has investigated the fire resistance of Light gauge steel framed (LSF) walls with PCM incorporated cellulose insulation through small-scale fire tests. It has also investigated the effects of using different insulation materials and their location on the fire resistance of LSF walls. Important results of this research are presented in this paper in the form of time-temperature profiles for cavity and externally insulated LSF wall configurations with and without PCM incorporated cellulose insulation. Findings reveal that externally insulated LSF walls have higher fire resistance levels than cavity insulated LSF walls based on insulation failure criterion. Importantly, adding PCM to cellulose insulation improves the fire resistance of both cavity and externally insulated LSF walls. PCM incorporated cellulose insulation can be used externally in LSF walls to enhance their fire and energy performance. However, the fire behaviour of Vacuum Insulation Panel (VIP) incorporated LSF wall is completely different to other wall systems.

Fire resistance of external light gauge steel framed walls clad with autoclaved aerated concrete panels

This paper presents an investigation into the fire resistance of external light gauge steel framed (LSF) walls clad with autoclaved aerated concrete (AAC) panels exposed to fire on the external side. Past research has been limited to the fire resistance of internal LSF walls clad with gypsum plasterboard on both sides. A series of experimental studies including thermal material property tests, a full-scale (3 m × 3 m) ambient capacity test of LSF wall and full-scale standard fire tests of non-load bearing and load bearing LSF walls were conducted to investigate the fire resistance of external LSF walls clad with AAC panels. Finally, a small-scale (1.2 m × 1.2 m) fire test of a wall made of AAC panels was also conducted to investigate the performance of joints between AAC panels. AAC panels with very low thermal conductivity performed exceptionally well by keeping the temperatures low for 160 min achieving a fire resistance level (FRL) of 204 min in load bearing conditions and 240 min in non-load bearing conditions. Hence, LSF walls clad with AAC panels can be used when higher FRLs are required. Experimental studies such as these on the whole system enable a good understanding of the overall fire performance of external wall systems in terms of structural adequacy and integrity instead of focusing only on the cladding.

Study of the fire and thermal behaviour of façade panels made of natural fibre-reinforced cement-based composites

The thermal and fire behaviour of calcium aluminate cement-based composites with a variable metakaolin content (from 0 to 40 wt% addition) reinforced with nonwoven flax fabrics has been examined. The fire behaviour was assessed using epiradiator and small-scale fire testing. The composites did not emit smoke or generate flames, nor did they produce spalling. Their integrity was maintained above 1000 °C. Samples having a higher metakaolin content revealed a delay in the temperature of the unexposed surface until reaching 760 °C. The effect of exposure to high temperatures (250 °C, 450 °C, and 950 °C) on bending behaviour was examined. The fibres were found to maintain their reinforcing capacity up to 250 °C, while the matrix maintained its performance up to 450 °C. The addition of metakaolin reduced conductivity and diffusivity. The results of the thermal and fire behaviour of the tested composites indicated that they may be suitable for façade panels for outdoor applications.

Multi-physics modeling of the ignition of polymer matrix composites exposed to fire

Advanced polymer matrix composites are widely used in modern aircraft and as such have to withstand fire to comply with safety regulations. The thermal degradation of these lightweight materials is a complex process involving chemical reactions in the solid and gas phases, potentially leading to flaming combustion. Here, we numerically investigate the heat feedback from the ignition of outgassing at the surface of a structural polymer matrix composite exposed to a pilot flame. Our model couples the thermal, physical and chemical processes in the solid phase to compute the composite degradation, as well as the production and movements of pyrolysates. A counterflow diffusion flame is used to model the ignition of the combustible effluent close to the sample surface, where the hot jet of the pilot flame impinges. The predictive capabilities of the method are demonstrated considering a carbon/epoxy composite subjected to a small-scale fire test. As input data for our model, material properties have been measured for virgin and partially burned samples via Differential Scanning Calorimetry, Xenon Flash Analysis and Thermogravimetric Analysis. The model is able to predict the backface temperature and time-to-ignition of the composite sample exposed to a flame with a good degree of accuracy.

Experimental Study on Thermosensitive Hydrogel Used to Extinguish Class A Fire.

Hydrogels are crosslinked polymers that become fully swollen when placed in aqueous environments. They are widely used in the field of firefighting because they can remarkably increase the viscosity and wettability of water. In this study, a thermosensitive hydrogel used to effectively suppress class A fire was synthesized by using methylcellulose, sodium polyacrylate, and magnesium chloride. The structure, surface activity and viscosity of the hydrogel were characterized. Fire extinguishing performance was evaluated based on small-scale and large-scale experiments. The results showed that a phase transition of the hydrogel occurred when the temperature rose from 50 °C to 80 °C. After the phase transition, the hydrogel showed a higher viscosity and lower surface tension, which was conducive to attach to the surface of the burning material and acting as an effective barrier to isolate oxygen. The small-scale fire extinguishing tests indicated that the concentration of the hydrogel solution has an eminent influence on fire extinguishing performance. The optimum concentration for extinguishing performance was around 6 wt%. The large-scale experiments demonstrated that the fire-extinguishing performance of this thermosensitive hydrogel was superior to the two other commercial water-based fire extinguishing agents, as it prevented re-ignition highly efficiently.

Alkyl sulfone bridged phosphorus flame-retardants for polypropylene

Three novel alkyl sulfone bridged phosphorus (P) compounds namely 6,6′-(sulfonylbis(ethane-2,1-diyl))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (SEDOPO), sulfonylbis(ethane-2,1-diyl))bis(diphenylphosphine oxide) (SEDPPO), and tetraphenyl (sulfonyl bis(ethane-2,1-diyl)) bis(phosphonate) (SEDPP) (i.e. phosphine oxide, phosphinate and phosphonate, respectively) were synthesized via a Michael addition reaction with good yields (≥ 85%) at a 200-g scale. They exhibited thermal stability above 250 °C, which allowed them to be melt-processed with polypropylene (PP) and formed into thin films (~ 0.6 mm). Rheological measurements of the PP blends exhibited a typical shear thinning behavior and provided evidence for the synthesized compound's thermo-oxidative stabilizing effect. This was also confirmed by thermal analysis showing that the thermo-oxidative stability of PP-SEDOPO and PP-SEDPPO blends was higher (~25 °C) than the blank PP; however, PP-SEDPP had a smaller impact. Small scale fire tests of the PP-FR blends confirmed the flame retardant efficacy of the new P-compounds. Cone calorimetry on PP-SEDOPO blends showed a reduction in the heat release rate (HRR) (~48%) compared to blank PP. Further thermal and evolved gas analysis of the PP blends confirmed that the new P-compounds are primarily active in the gas-phase.

Experimental study of fire resistant board configurations under standard fire conditions

Cold-formed Light gauge Steel Frame (LSF) floor-ceiling systems are commonly made with non-combustible fire protective membrane to protect the steel floor joists in fire. Thermal improvements to the fire protective membrane delay the heat transfer to structural elements and provide enhanced fire resistance level. Hence, this study addresses the thermal performance of different fire resistant board configurations under standard fire conditions to compare and propose improvements to conventional systems. Small-scale fire tests were conducted for a range of configurations of gypsum plasterboard, calcium silicate board and magnesium oxide board with the inclusion of thin steel sheathing. Fire test results showed that gypsum plasterboard and calcium silicate board performed very similar in regards to insulation criterion based failure times, while magnesium oxide board performed considerably worse. In all cases steel sheathing provided improved failure times. Improvements of 48%, 33% and 47% were obtained for gypsum plasterboard, calcium silicate board and magnesium oxide board when steel sheathing was used. This paper presents the details of the small-scale fire tests of different fire resistant board configurations and the results of time-temperature profiles. Based on these results, optimum fire resistant board configurations are recommended to achieve higher fire resistance levels for LSF floor-ceiling systems.

Theoretical and experimental studies on the fire-induced smoke flow in naturally ventilated tunnels with large cross-sectional vertical shafts

The study focuses on the fire-induced smoke flow in a naturally ventilated tunnel with large cross-sectional vertical shafts. For the shaft with large cross-section, the smoke is exhausted along four sides of the shaft, in which condition, the complete plug-holing occurs and the fresh air is entrained into the shaft strongly. In this work, studies on the longitudinal smoke temperature rise, smoke mass and heat exhausted as well as air entrainment from the shaft with large cross-section are performed theoretically. A method to predict the maximum smoke temperature rise downstream the shaft and the smoke back-layering length in naturally ventilated tunnel fires is proposed. Meanwhile, a series of small-scale fire tests was carried out by considering heat release rates (HRR) of the fires, shaft heights and adjacent shaft intervals. Experimental results indicate that the smoke back-layering length decreases with the increasing shaft heights, but it seems to be independent of the HRRs that are greater than 25.8 kW employed in the present work. Lastly, the validation of the proposed models is conducted by comparing with experimental results, which indicates that the models predict well the maximum smoke temperature rise on the downstream side of the shaft and the smoke back-layering length for small fires. The present study contributes to a guidance for smoke control in naturally ventilated tunnel fires with vertical shafts.

Michael addition in reactive extrusion: A facile sustainable route to developing phosphorus based flame retardant materials

This study addresses three very important aspects of sustainable development of new flame re-tardant material, i.e. in situ solvent free synthesis of flame retardant macromolecules during thermal processing of polymers, their leaching behavior from the polymer matrix and their preliminary toxicity assessment. Polyamide 6 (PA6) was functionalized by a novel reactive extrusion process. In situ synthesis of phosphine oxide based macromolecules was obtained via Michael addition reaction of divinyl phenyl phosphine oxide (DVPPO) and piperazine during the reactive extrusion process. The formation of phosphine oxide macromolecules (oligomers and low molecular weight polymers) were confirmed by NMR study of the modified PA6 polymer and UPLC-MS analysis of extracts from PA6 samples. Elemental analysis of the modified PA6 after the extraction with chloroform and water confirmed retention of majority of phosphorus species, confirming the beneficial effect of large macromolecular additives. This non-leaching behavior of modified PA6 is an important requirement for thin walled substrates like fibers and films where long-term durability is very important. The reactive extruded PA6 was successfully processed into textile fibers via melt spinning process in a laboratory spinning plant. The presence of phosphine oxide macromolecules in PA6 matrix had a lubricating effect, which has influence in the thermal processing and final properties of the fiber. The modified PA6 was evaluated for fire performance in small-scale fire tests where it showed improved fire performance. Moreover, the preliminary toxicity assessment of the relatively unknown DVPPO, via a well-established in vitro platform showed no adverse effects on cell viability.

Physical modeling of a fire with the use of the Froude number

Ever since the field of Fire Safety Engineering first came into existence, small-scale (model scale) fire tests were the source of much valuable information about the phenomena occurring during combustion. Over the years, several computational methods to determine the criteria for the similarity of fires on both a real and small geometric scale have been developed. The purpose of this article is to present a method of performing fire tests on a model scale using the Froude number. The basics of scaling, similarity conditions that must be preserved, ways of describing fire phenomena, as well as methods of calculating fire parameters from the real and model scale have been discussed. An example of physical tests with the use of reduced research models is also presented. What is particularly emphasized is how important these types of experiments are and what responsibility rests with the people who carry them ouvol. The motivation to conduct research is the safety of people who reside in buildings with fire protection based on model scale test.

Fire resistance of light gauge steel framed wall systems lined with PCM-plasterboards

Phase Change Material incorporated plasterboards (PCM-plasterboards) are used in buildings due to their high thermal storage capacity. However, their fire resistance has not been investigated yet. Hence, this research has investigated their fire resistance through thermal characterisation studies of wallboards and small-scale fire tests of wallboards and Light gauge steel-framed (LSF) walls. This paper presents the results on PCM-plasterboards in comparison with commonly used, fire-rated gypsum plasterboards. The elevated temperature thermal characteristics of PCM-plasterboard and gypsum plasterboard were determined first using thermal property tests whereas small-scale standard fire tests of both types of boards and non-load bearing LSF walls lined with both PCM-plasterboard and gypsum plasterboard were conducted to evaluate the fire resistance. Fire test results showed that the fire resistance levels (FRL) were reduced for PCM-plasterboards compared to gypsum plasterboards while importantly, PCM-plasterboards provided additional fuel to the fire. The LSF walls lined with a combination of PCM-plasterboard and gypsum plasterboard gave a lower FRL with higher stud hot flange temperatures, compared to those lined with gypsum plasterboards only. Fire resistance was greatly affected by the PCM-plasterboard after the fall-off of the first fire side plasterboard layer. Higher stud hot flange temperatures would reduce the FRL of load-bearing walls.

Fire performance of steel and plasterboard sheathed non-load bearing LSF walls

Light gauge steel-framed (LSF) walls are used as load bearing and non-load bearing building components in traditional concrete framed buildings and emerging all-steel structures. Recent building fire disasters around the world have highlighted the necessity for improved fire performance in such building components. While the fire performance of gypsum plasterboard, magnesium oxide board, calcium silicate board and oriented strand board (OSB) sheathed LSF walls has been assessed using fire tests and numerical analyses in the past, fire performance of steel sheathed walls remains unknown. Steel sheathing can improve the in-plane shear capacity of steel framed walls and is an accepted lateral load carrying system with widespread applications in the cold-formed steel construction industry. This paper presents the results of a series of small-scale fire tests conducted on steel and gypsum plasterboard sheathed composite panels and framed walls, and also an enthalpy based analytical study using the experimental results. Provision of steel sheathing either only internally, only externally or both internally and externally in combination was found to enhance the fire performance of plasterboard panels and plasterboard framed walls. The confinement of water within plasterboards for a prolonged duration with the provision of steel sheathing was found to be the prime cause of this improvement. Furthermore, the formation of thermal bridges across the stud in cavity insulated walls was found to reduce the fire performance significantly.

Application of the Kragten method in order to evaluate the uncertainty of the heat release rate determination using of the cone calorimeter

Assigning uncertainties to measurement results is primordial in a certification framework using fire benches as the cone calorimeter [1] developed by NIST [2]. Indeed, this process allows in the first place to validate the measurement method accuracy and in second place to provide proper results to compare obtained between different labs (reproducibility).However, even if numerous methods enable uncertainties determination, some can become complex when the data of interest is mathematical formulation powered by many measured parameters aimed to use in a model such as the Heat Release Rate (HRR).This article aims to propose an intermediate uncertainty calculation method whose difficulty of application is sized between the GUM method [3] and the Monte Carlo method [4]: the Kragten one [5]. In order to validate the opportunity of using such a method, the three approaches were used to assess the measurement uncertainty on the HRR parameter in the specific case of small scale fire tests using cone calorimeter.The results obtained show that the Kragten method allows to evaluate more easily and faster the HRR uncertainties measured at the Cone Calorimeter than the Monte Carlo method. Furthermore, the Kragten method is more reliable and reduces the risk of miscalculations than the GUM approach.

High-Throughput Fire Tests and Weathering-Induced Degradation Behaviour of Intumescent Coatings

In this work, the weathering-induced degradation of intumescent coatings was investigated by a systematic and comprehensive approach. A mechanism is revealed that is proposed to be responsible for the loss of function of intumescent coatings induced by weathering.First, the thermal decomposition of artificially weathered intumescent coatings was examined. To get a better understanding of the weathering and ageing phenomena, the degradation behaviour of the single ingredients during the weathering process was investigated, as well as their chemical and physical interactions. For the systematic approach, the materials that are essential for intumescence (ammonium polyphosphate, pentaerythritol, titanium dioxide, melamine and the binder) are treated with moisture, elevated temperature and UV radiation.Thermogravimetry (TG) and IR spectroscopy were used to compare the initial samples with their different grades of weathering. We demonstrate that ammonium polyphosphate, melamine and the binder are mainly responsible for the ageing process. Further, it was demonstrated that TG and IR spectroscopy are suitable measuring methods to detect the effects of weathering on intumescent coatings.Finally, a small-scale fire test procedure is introduced. Based on the reduction of the sample size, up to 50 samples can be tested in a single fire test. The results of this fire test have the same quality as the results from standard intermediate fire tests corresponding to DIN 4102-8.