Fire and Materials最新文献

In hygrothermal conditions, structural safety is a major concern because of the occurrence of explosive spalling when concrete structures are exposed to fire. To evaluate the fire damage of concrete accurately, the effect of moisture content and water-to-cement ratio on the thermal conductivity of concrete under elevated temperatures was studied experimentally and analytically in this paper. The experimental results showed that the temperature fields had a significant change among the cases with different water-to-cement ratios while the changes between dried and saturated cases were marginal. The temperature changes of dried samples were slightly swifter than those of saturated one. It indicates that compared with mixture proportions, concrete saturation degree has an insignificant influence on concrete heat transfer in the procedure of fire exposure. Based on the test and analytical results, an analytical model for heat transfer analysis of fire-damaged concrete under hot and humid environments was proposed and showed good agreement with the test results.

This paper presents the results of experimental studies investigating the effects of recoating on fire protection properties of composite layers of intumescent coatings for steel elements. Intumescent coatings, both with and without topcoats, were applied to steel plates. The samples were subjected to different cycles of hydrothermal aging before recoating. The composite layers of the existing and new coatings were then tested under fire. Comparisons of the morphological structures of the carbonaceous char revealed that the existing coating had little effect on the expansion properties of the new coating. However, the new coating reduced the expansion ratio of the existing coating. The thermal resistance of the existing coating decreased with the increasing thickness of the new coating. For specimens with a new coating 1.0 mm thick, the thermal resistance of the existing coating, after even moderate environmental exposure, was < 20% of the total and can be ignored. Contributions from the existing coating may be considered when specifying the thickness of the new coating if the new coating thickness is small and the existing coating is subjected to moderate environmental aging. Recoating with a different type of intumescent coating from the existing one appeared to provide better fire protection performance than using the same type.

In this work, green synthesised TiO₂ nanoparticles' coating was used to improve the fire safety and antibacterial property of 100% cotton fabric. In the first stage, Aloe vera extract was prepared, and subsequently used in the synthesis of TiO₂ nanoparticles. The average size of these as-synthesised TiO₂ nanoparticles was confirmed to be 16 nm using DLS (dynamic light scattering). Further, XRD (X-ray diffraction) patterns confirmed the successful synthesis of nanoparticles. The vibrational photon of TiO₂ was represented by peaks in the FTIR (Fourier transform infrared spectroscopy) spectrum between 450 and 800 cm⁻¹. Subsequently, in an attempt to establish the flame retardant/crease proof/microbial resistant properties of the as-synthesised TiO₂ nanoparticles, the TiO₂ NPs coated cotton fabric was used for the investigations. Based on the investigations, the bending length (measure of fabric stiffness) value of the coated fabric (%) increased from 2.4 cm (uncoated fabric) to 3.71 cm (at 20% TiO₂ coating). Also, the crease recovery angle value increased from 71.8 (uncoated fabric) to 98.6 (20% TiO₂ coating), respectively. A vertical flammability test revealed that the burning time decreased from 13.31 s (0%) to 10.84 s (20%), confirming a fire-retardant trait of green synthesised TiO₂ nanoparticle coated fabric. Additionally, the disc diffusion method confirmed that the treated coated fabrics exhibit antibacterial properties against both gram-positive and gram-negative bacterial cultures: Escherichia coli and Staphylococcus aureus. This study provides an environmentally benign route for producing versatile cotton fabric blended with bioinspired TiO₂ NPs possessing improved flame resistance as well as antibacterial attributes.

The occurrence of wildfire disasters can easily trigger tripping in overhead transmission-line, thereby posing a significant threat to the safe and stable operation of the power system. In order to enhance the wildfire prevention and control capability of overhead transmission-line, a wildfire risk assessment method based on the improved analytic hierarchy process (AHP) is proposed. First, the main factors of wildfire occurrence are explored, and the wildfire risk indicator system for overhead transmission-line is constructed. We propose a novel runaway coefficient of fire for assessing the impact of fire sources on wildfire disaster. Secondly, the mutual information method is used to avoid the subjective arbitrariness of AHP to improve the reliability of each index weight. The results show that about 82.14% of new fire events of 2023 in Fujian (China) are located in medium-, high-, and very-high-risk areas, demonstrating the effectiveness of the proposed method. This methodology offers a foundation for the power system to mitigate the risk of wildfire.

Given the seriousness of fire safety issues in high-altitude traffic tunnels, it is essential to investigate the spatial temperature characteristics under the coupling of multiple factors and their correlation with fire safety elements. This study systematically conducted full-scale simulation analyses of highway tunnels to reveal the distribution of transverse and longitudinal spatial temperature as well as the longitudinal smoke diffusion patterns. Based on the simulation data, an integrated approach utilizing orthogonal test analysis, deviation analysis, and sensitivity analysis was employed to explore the impacts of various factors, including altitude, the transverse position of the fire source, fire scale, and wind speed, on tunnel fire safety. The results indicate that the influence of altitude on the longitudinal temperature along the arch and the position of spatial cross-section characteristic points varies. Longitudinal ventilation speed is a relatively key factor affecting tunnel fire safety, particularly in terms of arch temperature and smoke backflow length, where its impact is significant. Additionally, fire scale has a notable impact on evacuation safety, with its overall influence ranking just below that of wind speed. In contrast, altitude and fire source position have relatively minor effects on tunnel fire safety. Inadequate longitudinal ventilation hinders the escape of personnel during tunnel fires, indicating that the design and operation of ventilation systems should be prioritized in fire prevention and control strategies. The findings of this study have significant practical implications for optimizing fire prevention and response capabilities in high-altitude tunnels.

To optimize the performance of inorganic solidified foam and apply it effectively in forest fire fighting, three different ionic surfactants were combined with four viscosity-increasing foam stabilizers. Then, the ratio of inorganic solidified foam was changed to investigate the effects of four factors, namely, water–binder ratio, quick-setting agent dosing, fly ash dosing, and foam dosing, on the foaming multiple and stability of the inorganic solidified foam. Finally, the fluidity and adhesion ability of the inorganic solidified foam were tested with different quick-setting agent dosages and foam dosages, and the optimal working condition range of the inorganic solidified foam was determined based on the test results. The results showed that when SDS:APG = 7:1, the foaming multiples of the foam were higher and it could reach 52.5 times when the surfactant content in the solution was 1.2 wt%; among the four viscosity-increasing stabilizers, the stabilizing effect of xanthan gum was the best. The inorganic solidified foam exhibits an extended foaming time when utilizing a water–binder ratio of 0.45 and a fly ash dosage of 0.5. To ensure optimal mobility and a specific adhesion thickness, it is recommended to maintain a foam dosage of 6 V or higher, with mobility falling within the 11–13 range. The preferred ratio for creating inorganic solidified foam involves a water–binder ratio of 0.45, a 0.6 wt% dosage of accelerating agent, a 0.5 fly ash content, and a foam mixing of 7 V.

As wildfire risks increase, it is essential to retrofit the existing housing stock in wildfire-prone areas to reduce community wildfire risk. Yet there are significant questions regarding the costs and most effective strategies to retrofit homes for improved wildfire resistance. This article identifies the costs for retrofitting homes to meet the requirements specified by Chapter 7A (Materials and Construction Methods for Exterior Wildfire Exposure) in the California Building Code. Guidance from recent research related to ignition-resistant construction was also utilized. Construction costs were calculated as a per-unit value and were explicit to the exterior components of the home. Detailed estimates are offered for upgrading a home's exterior walls, roof, deck, windows and doors, under-eave areas, gutters, and near-home landscaping. Analysis demonstrates that some of the most effective strategies to reduce structure vulnerability to wildfire can be done affordably. This analysis suggested that for a typical 2000-square-foot home in California, retrofitting costs can be as low as $2000 for minimal retrofits to $100,000 for the highest level of protection.

This article presents a comprehensive study of the insulation materials used for lithium-ion battery fire blanket coatings. First, a novel testing method is introduced to quantify the impact of insulating agents on the softness and wraparound capabilities of the blanket. Second, to guarantee the explosion resistance as well as other functions of the blanket, insulation materials are introduced, and the insulation effectiveness of various insulating agents is assessed using a 1200°C flame, with findings indicating that a 10% addition of 20 nm silica aerogel yields the best insulation effect. Further analysis of the influence of insulating agents on the release of pyrolysis particles and smoke reveals that both concentrations are elevated compared to the bare silicon dioxide cloth, thereby enabling fire detectors to trigger alarms at the earliest possible stage. Finally, low-temperature tests are conducted to verify the enhanced insulation properties of the coating in non-fire scenarios. The outcomes confirm that a 10% addition of 20 nm silica aerogel provides the best insulation. The research results demonstrate that this innovative coating exhibits outstanding insulation performance across a broad temperature range and offers significant fire detection and protection functionalities.