Purpose The purpose of this study is to address the issue that polyurethane (PU) rigid foam, used as building exterior wall insulation, is highly flammable and releases toxic smoke and gas. It aims to evaluate the fire safety performance of flame-retardant PU materials in a realistic dormitory building fire scenario. Design/methodology/approach Ordinary PU and flame-retardant PU materials were prepared. Combined with data obtained from a thermogravimetric analyzer and a cone calorimeter, the combustion parameters of these materials were defined in the fire dynamics simulator (FDS). This was used to numerically simulate a realistic dormitory fire scenario to analyze key fire characteristics, including smoke propagation trends and flame temperature dynamics. Findings When flame-retardant PU is utilized as external wall insulation, the temperature at the staircase entrance remains below 60? within the first 200 seconds of the fire. Concurrently, the carbon monoxide (CO) concentration is maintained within an acceptable range for human exposure. The material effectively isolates heat and oxygen, preventing significant smoke spread within the critical 200-second window, thereby providing crucial time for safe personnel evacuation. Originality/value This study addresses a gap in current research by numerically simulating the application of flame-retardant polyurethane in a realistic dormitory building fire. While many studies focus solely on material properties, this research integrates experimental data from a thermogravimetric analyzer and a cone calorimeter directly into the FDS. It demonstrates the practical value of a newly prepared flame-retardant material in significantly extending the available safe egress time (ASET) by delaying toxic smoke spread and extreme temperature rises, providing vital insights for building fire safety design.
Purpose The present investigation aims to examine the impacts of high temperature on the flexural strength and modulus of elasticity properties of concrete specimens produced by substituting waste foundry sand at 25%, 50%, 75% and 100% of the river sand. The modulus of elasticity and flexural strength of samples with 100% waste foundry sand (CFS-4) content decreases as the temperature increases. At 600°C temperature, the specimens with 100% waste foundry sand (CFS-4) shows lowest values of modulus of elasticity and flexural strength. Scanning electron microscopy images of specimens with 100% waste foundry sand (CFS-4) exhibits uniform distribution of pore structures owing to increased porosity due to increase in temperature. At high temperatures, the stress-strain curve changes its shape from that of unheated concrete, resulting in a flatter stress vs. strain curve. The projected outcomes from the suggested mathematical formulas based on experimental investigation confirm lesser variations when compared to literature models. It is recommended that the suggested mathematical formulas can be employed for predictions of modulus of elasticity at sustained elevated temperature. Design/methodology/approach After casting, concrete samples were allowable to cure for 28 days. The samples were removed from the curing tank after 28 days curing and dried for another 2 days in order to prevent explosive spalling during the heating process. The produced specimen is subjected to 100°C, 200°C, 300°C, 400°C, 500°C and 600°C temperatures for duration of two hours. The MOE, flexural strength test, and SEM analyses were carried out after the specimens had cooled to room temperature (RT). Findings The specimens with higher content of WFS exhibits decline in MOE and flexural strength at high temperatures. A flatter stress vs. strain curve progresses as the rise in temperature and there are changes in shape of the stress-strain curve from that of unheated concrete at high temperatures. From the experimental investigations, it is recommended to use the suggested mathematical formulas to assess the MOE of cylindrical samples after subjected to high temperatures. Originality/value The study is carried out to assess the post-thermal residual mechanical behavior of concrete after completely replacing the natural sand with WFS at the intervals of 25% up to 100%. The post-heat effect on mixes indicates that MOE and flexural strength show lower results than referral mixes. It is found that, higher temperatures have a stronger impact on the MOE of concrete samples with higher WFS contents when compared to compressive strengths.
Purpose In order to quantitatively evaluate the mechanical properties of high-strength Q460 steel at elevated temperatures and after fire exposure, tensile tests were conducted on Q460 high-strength steel at elevated temperatures and after fire exposure. Design/methodology/approach For the post-fire tensile tests, a constant tensile stress was applied during the heating and cooling stages of the specimen. The stress-strain curves for Q460 high-strength steel were recorded, from which the yield strength, ultimate strength and elastic modulus were obtained. Findings The results show that the strength decreases to 10% of its room-temperature value, while the elastic modulus remains at 40% at 800 °C. The post-fire residual strength of Q460 steel decreases sharply and the tensile stress has an approximately 10% adverse effect on the post-fire residual strength of high-strength Q460 steel when the exposure temperature is between 700 °C and 800 °C. Originality/value A series of constitutive models and predictive equations based on the test results are proposed to evaluate the mechanical properties of Q460 steel at high temperatures and after fire exposure.
Purpose Portland-limestone cement (PLC) is a low-carbon, green alternative binder that can substitute for ordinary Portland cement (OPC) to support the development of eco-friendly infrastructure solutions. The building's energy consumption and strength retention efficiency can be improved by effectively enhancing the cementitious matrix properties of the rendering materials. Design/methodology/approach In this study, the residual mechanical strengths and microstructure of OPC and PLC mortars before and after exposure to elevated temperatures of up to 800 °C were experimentally investigated. Tested specimens were prepared using 0%, 5%, 10% and 15 wt.% of limestone as a replacement for OPC. The fire-resistance performance of the prepared rendering mixtures was evaluated through their residual strengths, X-ray diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Findings Based on the results, the mechanical properties of all mortars improved at 250 °C, due to internal autoclaving and pore pressure effects. At 800 °C, the major phases observed in OPC and PLC mortars were calcium silicate and quartz. Large wollastonite and gehlenite crystalline phases were observed in PLC mortars; thus, the matrix structure was severely damaged, and this damage was more pronounced in PLC mortars. Originality/value Several studies have concentrated on this area, and numerous investigations into the fire-resistance performances of cement-based mortars have been reported. Nevertheless, limited investigations focused have focused on the residual strengths of rendering mortars made with PLC as a sustainable alternative to Portland cement; and therefore, have not been acknowledged to date.
Purpose In this experimental investigation, the high-yield strength-deformed-steel (HYSD) and glass-fibre-reinforced-polymer (GFRP) rebars were employed to assess the bond behaviour at RT, 1000ºC, 2000ºC and 3000ºC. Natural river sand has been completely replaced with manufactured sand (MS) in the production of concrete, wherein it was observed that, the residual compressive strength decreases as the temperature increases. Based on ultrasonic pulse velocity (UPV) test results, the quality of concrete can be categorised from “Excellent to Good”. The bond strength of HYSD bar specimens reveals higher values compared to specimens with GFRP bars at RT, 1000ºC, 2000ºC and 3000ºC. The specimens with HYSD bars show lower slippage when compared to specimens with GFRP bars at elevated temperatures and the pullout failures have been noticed for the specimens at elevated temperatures. Based on experimental investigation, the mathematical equations have been suggested for predicting the bond stress at high temperatures. Design/methodology/approach The mix design has been conducted in line with IS 10262:2019 following material characterization. The samples were cast in the prescribed mix ratios and cured for 28 days. After curing, the samples were then dried for 48 h to remove any moisture and prevent cubes from spalling during heating. The samples were placed in an electrical furnace of 10000ºC capacity and heated to the desired temperatures for 2 h. The specimens were cooled to room temperature (RT) in the furnace, and non-destructive testing such as UPV and rebound hammer tests were performed to evaluate the quality of the post-heated specimens. The compression and pullout tests were performed to evaluate the post-heat mechanical behaviour. The analysis and interpretation of results were performed to examine the behaviour of specimens exposed to sustained elevated temperatures, and conclusions were drawn at the end of the research. Findings The specimens with HYSD bars reveal greater bond strength than specimens with GFRP bars at each interval of temperatures. The maximum slippage was observed for the specimens with GFRP bars at 3000ºC. This indicates increase in slip with rise in temperatures. Originality/value The bond strength of HYSD bar samples is higher than that of GFRP bars at RT, 1000ºC, 2000ºC and 3000ºC. At higher temperatures, specimens with HYSD bars exhibit lesser slippage than specimens with GFRP bars, and pullout failures were observed. Based on experimental data, mathematical formulae for estimating bond stress at high temperatures have been proposed.
