Post-fire Impact Research Articles

Experimental Investigation of the Post-Fire Impact Resistance and Energy-Absorbing Characteristics of Polyethylene Cored Lightweight Metal Sandwich Panels

ABSTRACT To investigate the effect of different fire loading time and stitching methods on the post-fire impact resistance of the polyethylene cored sandwich panels, quasi-static perforation, and low-velocity impact tests were conducted after real fire tests. The temperature distribution, deformation, failure behavior, load-carrying capacity, and energy absorption capacity of the panels were explored and compared. The effects of key parameters such as the stitching method, fire time, and impact energy on the load versus displacement curves and energy absorption were discussed in detail. In addition, a theoretical model was developed to predict the plastic strain of sandwich panels under the low-velocity impact, and the results showed that when the height of the falling hammer is constant, the depression value of the upper surface center point ( δ 1 ) and the depression value of the lower surface center point ( δ 2 ) are both linearly related to 1 ( T m − T r ) n − T − T r n .

Effect of Activator Concentrations on the Postfire Impact Behavior of Alkali-Activated Slag Concrete

Changing concrete ingredients significantly affects its performance due to changing the type of hydration products formed. The stability of these hydration products will dominate concrete impact behavior before and after exposure to fire. Limited research had explored the role of activators, as the main ingredient of alkali-activated slag concrete (AASC), on impact performance. Hence, this study highlights the effects of activator characteristics on the impact behavior of AASC at an ambient condition (23°C) and after exposure to elevated temperatures (200°C, 400°C, and 600°C). Conventional ordinary portland cement (OPC) concrete was also tested for general performance comparison. Besides the drop weight impact test, compressive and indirect splitting tensile strength, shrinkage, ultrasonic pulse velocity and water absorption tests were conducted to evaluate AASC performance. In addition, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to confirm and analyze findings. Results confirmed the better impact performance of AASC compared to OPC concrete. Activator concentrations showed contrary effects on AASC performance at ambient and elevated temperatures. High activation levels improved strength and impact capacity at ambient temperature, showing lower internal defects and higher hydration product formation. Conversely, lowering the activation level at elevated temperatures was preferable and resulted in a higher residual strength and impact absorption capacity. This was ascribed to the high unreacted slag particle crystallization to akermanite at higher temperatures, leading to strength gain, fewer hydration products to decompose, and high microstructure ductility that accommodated the thermal incompatibility. Hence, designing AASC while focusing only on maximizing strength can be misleading based on the targeted performance and exposure conditions.

Efficacy of Fire Protection Techniques on Impact Resistance of Self-Compacting Concrete

The present research investigates the behaviour of sustainable Self-Compacting Concrete (SCC) when subjected to high temperatures, focusing on workability, post-fire impact resistance, and the effects of fire protection coatings. To develop environmentally friendly SCC mixes, Supplementary Cementitious Materials (SCM) such as Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBFS), and Expanded Perlite Aggregate (EPA) were used. Fifty-six cubes and ninety-six impact SCC specimens were cast and cured for testing. Fire-resistant Cement Perlite Plaster (CPP) coatings were applied to the protected specimens, a passive protection coating rarely studied. SCC (unprotected and protected) specimens, i.e., protected and unprotected samples, were heated following the ISO standard fire curve. An extensive comparative study has been conducted on utilising different SCMs for developing SCC. Workability behaviour, post-fire impact resistance, and the influence of fire protection coatings on sustainable SCC subjected to high temperatures are the significant parameters examined in the present research, including physical observations and failure patterns. The test results noted that after 30 min of exposure, the unprotected specimen exhibited a significant decrease in failure impact energy, ranging from 80% to 90%. Furthermore, as the heating duration increased, there was a gradual rise in the loss of failure impact energy. However, when considering the protected CPP specimens, it was observed that they effectively mitigated the loss of strength when subjected to elevated temperature. Therefore, the findings of this research may have practical implications for the construction industry and contribute to the development of sustainable and fire-resistant SCC materials.

Post-fire impact behaviour of rubberized alkali-activated slag concrete

Rubberized concrete is eco-friendly concrete with improved impact resistance. However, impact loads may also be combined with fire due to blasting, explosions, and earthquake. Hence, this study investigates the post-fire impact behaviour for rubberized alkali-activated slag (AAS) concrete. Static and dynamic properties of AAS mixtures, incorporating 5%, 10%, and 15% crumb rubber, were evaluated under ambient and after exposure to elevated temperatures (200, 400, and 600 °C). Results reveal that AAS properties' degradations were similar to ordinary Portland cement (OPC) at ambient temperature. At elevated temperatures, the differences in hydration products’ nature between AAS and OPC alternated the performance. The formed low Ca/Si ratio calcium silicate hydrated in the AAS exhibited higher stability at elevated temperatures. AAS with 10% rubber content showed an optimum impact performance. Above 400 °C, degradation of the binder microstructure and voids due to rubber particle decomposition adversely affected the impact performance of AAS. The addition of 0.5% steel tire wire showed a high potential sustainable solution to maintain adequate performance.

Fire reaction and post-fire impact properties of flax fibre reinforced composites containing intumescent flame retardants

The current research aims at investigating the fire reaction and post-fire impact characteristics of flax fibre reinforced composites based on different polymer matrices, such as epoxy resin and polypropylene (PP). The effects of stacking sequences of polymer sheets and flax fabrics within the composites are explored by a cone calorimeter. Heat release and smoke production results indicate that a top surface and number of flame-retardant polymer layers played significant roles in determining the fire reaction properties. Furthermore, post-fire impact properties of flax-epoxy and flax-PP composites depending on burning periods are analysed in this study at the first time. A fully instrumented drop-weight impact testing demonstrates that an increase in heat exposure time led a gradual decrease in impact properties of the composites due to fire-induced damages on fibres and polymers. However, pre-melting and re-consolidation of PP are beneficial to have higher impact energy and force of the flax-PP composite over those of the flax-epoxy counterpart. In addition, the char formation of composites due to intumescent flame retardant enhances the fire reaction properties of composites, whereas there is no significant influence on the post-fire impact characteristics due to highly brittle nature of carbonaceous char.

Operational Mapping and Post-Disaster Hazard Assessment by the Development of a Multiparametric Web App Using Geospatial Technologies and Data: Attica Region 2021 Wildfires (Greece)

The environmental effects of wildfires are a hot issue in current research. This study examines the effects of the 2021 wildfires in the Attica region in Greece based on Earth observation and GIS-based techniques for the development of a web app that includes the derived knowledge. The effects of wildfires were estimated with the use of Sentinel-2 satellite imagery concerning burned area extent and burn severity using a NBR-based method. In addition, the erosion risk was modeled on a pre-fire and post-fire basis with the RUSLE. This study highlights the importance of assessing the effects of wildfires with a holistic approach to produce useful knowledge tools in post-fire impact assessment and restoration.

Correction to: Post-fire impact behavior and durability of steel fiber-reinforced concrete containing blended cement–zeolite and recycled nylon granules as partial aggregate replacement

Correction to: Post-fire impact behavior and durability of steel fiber-reinforced concrete containing blended cement–zeolite and recycled nylon granules as partial aggregate replacement

Modelling effects of forest fire and post-fire management in a catchment prone to erosion: Impacts on sediment yield

The present paper contributes to bridging the gaps in modelling post-fire impact and mitigation measures on soil erosion. The specific aims were to predict the effects of forest fires and post-fire mitigation measures on runoff and specific sediment yield (SSY) in a river basin (Celone, S-E Italy). The Soil and Water Assessment Tool model, calibrated with field observations, was used to evaluate runoff and SSY for the current land use (baseline) and six post-fire scenarios. From 1990 to 2011, at the basin scale, the average annual SSY was 5.60 t ha- 1yr−1 (SD = 3.47 t ha-1yr−1). 20% of the total drainage area showed a critical value of SSY (>10 t ha−1 yr−1). The effects of different fire-severity levels were predicted for one year after the fire, acting on a limited area (2.3% of the total basin area). At the basin scale, the post-fire effect on surface runoff was negligible for all scenarios (<0.4%), and the impact on SSY increased from 5.86 t ha−1 yr−1 up to 12.05 t ha−1 yr−1. At the subbasin scale, the post-fire logging scenario showed the highest increase of soil loss (SSY increased from 9.48 t ha−1 yr−1 to 57.40 t ha−1 yr−1). Post-fire mitigation treatments like straw mulching and erosion barriers effectively reduced soil erosion in high- and moderate-severity fires (19.12 t ha-1yr−1 and 20.93 t ha−1 yr−1, respectively). At the hydrological response unit level, the SSY estimated for the forest in the baseline ranged from 1.18 t ha- 1yr−1 to 2.04 t ha−1 yr−1. SSY increased more than one order of magnitude for the high-severity fire scenarios and ranged from 4.33 to 6.74 t ha−1 yr−1 in the very low-severity fire scenario, underlining the scale effect from the HRU to the basin scale.

Post-fire impact behavior and durability of steel fiber-reinforced concrete containing blended cement–zeolite and recycled nylon granules as partial aggregate replacement

Post-fire impact behavior and durability of steel fiber-reinforced concrete containing blended cement–zeolite and recycled nylon granules as partial aggregate replacement

Corrigendum to: Interdependencies between flame length and fireline intensity in predicting crown fire initiation and crown scorch height

This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram's fireline intensity, flame length, stem-bark char height and crown scorch height. More specifically, the following topical areas are critically examined based on a comprehensive review of the pertinent literature: (i) estimating fireline intensity from flame length; (ii) substituting flame length for fireline intensity in Van Wagner's crown fire initiation model; (iii) the validity of linkages between the Rothermel surface fire behaviour and Van Wagner's crown scorch height models; (iv) estimating flame height from post-fire observations of stem-bark char height; and (v) estimating fireline intensity from post-fire observations of crown scorch height. There has been an overwhelming tendency within the wildland fire community to regard Byram's flame length–fireline intensity and Van Wagner's crown scorch height–fireline intensity models as universal in nature. However, research has subsequently shown that such linkages among fire behaviour and post-fire impact characteristics are in fact strongly influenced by fuelbed structure, thereby necessitating consideration of fuel complex specific-type models of such relationships.

Post-fire restoration of tree species in various soil conditions after surface fires zone

The study of forest regeneration in stands exposed to fire has both fundamental and applied relevance. The objects of the study were the exposed to surface fires forest plots of various soil and hydrological conditions in the north-east of the Leningrad Region in the landscape of the Tikhvin ridge of the north-eastern part of the Valdai Hills. To study the natural renewal of tree species, circular plots of 10 m2 were created along a transect traced over a diagonal of the area exposed to fire. Post-fire impact on soils with different particle size distribution causes the formation of stands with different shares of coniferous and broad-leaf species. After the exposure of tree communities to fire, regeneration processes can follow different directions in the formation of the future planting composition, and that depends on soil and hydrological conditions. Knowing the succession status of the post-fire plant community, further silvicultural measures can be planned for the management of stand composition.

Oil palm ‘slash-and-burn’ practice increases post-fire greenhouse gas emissions and nutrient concentrations in burnt regions of an agricultural tropical peatland

Fire is one of the major issues facing Southeast Asian peatlands causing socio-economic, human health and climate crises. Many of these fires in the region are associated with land clearing or management practices for oil palm plantations. Here we study the direct post-fire impacts of slash-and-burn oil palm agriculture on greenhouse gas emissions, peat physico-chemical properties and nutrient concentrations. Greenhouse gas (GHG) emissions were measured using Los Gatos ultraportable greenhouse gas analyser one month after a fire in dry season and five months after the fire event, in wet season. Surface soil samples were collected from each individual GHG measurement points, along with 50 cm cores from both burnt and non-burnt control areas for lab analyses. As an immediate post-fire impact, carbon dioxide (CO2) and methane (CH4) emissions, pH, electrical conductivity, and all macronutrient concentrations except nitrogen (N) were increased multi-fold, while the redox potential, carbon (C) and N content were greatly reduced in the burnt region. While some of the properties such as CO2 emissions, and electrical conductivity reverted to normal after five months, other properties such as CH4 emissions, pH and nutrient concentrations remained high in the burnt region. This study also found very high loss of surface peat C content in the burnt region post fire, which is irreversible. The results also show that surface peat layers up to 20 cm depth were affected the most by slash-and-burn activity in oil palm agriculture, however the intensity of fire can vary widely between different oil palm management and needs further research to fully understand the long term and regional impacts of such slash-and-burn activity in tropical peatlands.

Corrigendum to: Interdependencies between flame length and fireline intensity in predicting crown fire initiation and crown scorch height

This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram's fireline intensity, flame length, stem-bark char height and crown scorch height. More specifically, the following topical areas are critically examined based on a comprehensive review of the pertinent literature: (i) estimating fireline intensity from flame length; (ii) substituting flame length for fireline intensity in Van Wagner's crown fire initiation model; (iii) the validity of linkages between the Rothermel surface fire behaviour and Van Wagner's crown scorch height models; (iv) estimating flame height from post-fire observations of stem-bark char height; and (v) estimating fireline intensity from post-fire observations of crown scorch height. There has been an overwhelming tendency within the wildland fire community to regard Byram's flame length–fireline intensity and Van Wagner's crown scorch height–fireline intensity models as universal in nature. However, research has subsequently shown that such linkages among fire behaviour and post-fire impact characteristics are in fact strongly influenced by fuelbed structure, thereby necessitating consideration of fuel complex specific-type models of such relationships.

Interdependencies between flame length and fireline intensity in predicting crown fire initiation and crown scorch height

This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram’s fireline intensity, flame length, stem-bark char height and crown scorch height. More specifically, the following topical areas are critically examined based on a comprehensive review of the pertinent literature: (i) estimating fireline intensity from flame length; (ii) substituting flame length for fireline intensity in Van Wagner’s crown fire initiation model; (iii) the validity of linkages between the Rothermel surface fire behaviour and Van Wagner’s crown scorch height models; (iv) estimating flame height from post-fire observations of stem-bark char height; and (v) estimating fireline intensity from post-fire observations of crown scorch height. There has been an overwhelming tendency within the wildland fire community to regard Byram’s flame length–fireline intensity and Van Wagner’s crown scorch height–fireline intensity models as universal in nature. However, research has subsequently shown that such linkages among fire behaviour and post-fire impact characteristics are in fact strongly influenced by fuelbed structure, thereby necessitating consideration of fuel complex specific-type models of such relationships.

Burned area mapping and post-fire impact assessment in the Kassandra peninsula (Greece) using Landsat TM and Quickbird data

The purpose of this study was to assess the environmental impacts of forest fires on part of the Mediterranean basin. The study area is on the Kassandra peninsula, prefecture of Halkidiki, Greece. A maximum likelihood supervised classification was applied to a post-fire Landsat TM image for mapping the exact burned area. Land-cover types that had been affected by fire were identified with the aid of a CORINE land-cover type layer. Results showed an overall classification accuracy of 95%, and 83% of the total burned area was ‘forest areas’. A normalized difference vegetation index threshold technique was applied to a post-fire Quickbird image which had been recorded six years after the fire event to assess the vegetation recovery and to identify the vegetation species that were dominant in burned areas. Four classes were identified: ‘bare soil’, ‘sparse shrubs’, ‘dense shrubs’ and ‘tree and shrub communities’. Results showed that ‘shrublands’ is the main vegetation type which has prevailed (65%) and that vegetation recovery is homogeneous in burned areas.

Thermal shock and rain effects on soil surface characteristics: A laboratory approach

Abstract In addition to its direct impact on soil physical and chemical soil properties, fire produces a sudden change in plant cover. The post-fire impact of falling raindrops on unprotected soil surfaces is a major cause of detachment of aggregates, physical degradation and erosion of soils. The aim of this work was to analyse the effects of burning intensity and rain under factor-controlled conditions using unaltered soil samples. Assessed variables were soil organic carbon, aggregate stability and water repellency (0–1 cm mineral soil), as well as soil surface compaction and hydraulic conductivity. Unaltered topsoil cores were obtained in a mature Mediterranean gorse shrubland. We applied two successive treatments: burning (unburned, low and high burning levels) and rain (77 mm/h). The soil properties studied were scarcely affected by burning. However, soils showed high vulnerability to raindrop impact: a) aggregate stability and organic carbon were not significantly affected by burning; b) low intensity burning increased the frequency of samples with moderate water repellency, whereas unburned together with high burning showed more cases of low and extreme water repellency; c) the rain treatment produced a significant decrease in hydraulic conductivity although this response was independent of burning level; d) the highest reduction in hydraulic conductivity was observed in the samples with highest values prior to the rain treatment, and this was related to the highest organic carbon contents, and e) the reduction in hydraulic conductivity could be explained by the development of a thin and friable surface crust, although the cone penetrometer was not sensitive enough to detect this observed phenomenon.