Elevated Temperature Exposure Research Articles

Mechanical Performance of Steel-PVA Hybrid Fiber Concrete After Elevated Temperature Exposure

Mechanical Performance of Steel-PVA Hybrid Fiber Concrete After Elevated Temperature Exposure

Influence of stream temperature and human disturbance on prespawn mortality of Chinook Salmon in the Willamette River basin

AbstractObjectivePremature mortality of adult female Chinook Salmon Oncorhynchus tshawytscha is a major barrier to population recovery. The Willamette River basin, Oregon, typifies the problems that are faced by fishery managers in the Pacific Northwest (USA). Adult salmon are trapped and transported upstream of dams to access historical spawning grounds, but annual rates of prespawn mortality (PSM) are high (often >40%) and may limit the recovery of natural populations. The purpose of this study was to identify potential factors related to PSM of female Chinook Salmon that are outplanted above dams and incorporate them into a modeling framework to facilitate adaptive management of outplanting operations.MethodsWe evaluated PSM in Fall Creek of the Willamette River basin prior to transport facility improvements in summer and fall of 2010–2017 and postimprovement during 2020–2021. We estimated PSM and conducted exploratory analyses to identify possible nontransport sources of stress that may contribute to the observed high PSM rates. Candidate factors included long‐term elevated temperature exposure, elevated temperature exposure below the trap, total number of outplanted fish, and monthly human disturbance of outplanted fish. We then developed and fit three models, each representing a hypothesis of a factor influencing PSM, incorporated them into a single alternative decision model, and conducted sensitivity analyses.ResultPrespawn mortality averaged 0.66 (ranging from 0.37 to 0.94) over the study period. According to the simulation results, the top two management actions were to exclude human activities—swimming and fishing—from Fall Creek in July and August.ConclusionExpected PSM rates were predicted to be 0.38 when human activity was excluded in July and 0.37 for August. Sensitivity analyses indicated that the most influential decision model component was the choice of the alternative model.

Impact of Elevated Temperature Exposure on Some Properties of Sustainable Mortar with Plastic Bag Waste

Impact of Elevated Temperature Exposure on Some Properties of Sustainable Mortar with Plastic Bag Waste

Microstructure evolution and mechanical properties of SiCf/BN/SiBCN composite after high temperature thermal exposure

The present study investigates the microstructure evolution and subsequent mechanical properties of SiCfiber/BN/SiBCNmatrix composites after high temperature exposure. These composites display a non-brittle failure response under three-point bending retaining 80% of the as-processed strength, even after elevated temperature exposure up to 1350oC for 10h. This is due to crack deflection accompanied by extensive fiber pull-out. In addition, both thermodynamic modelling and phase analysis by XRD show higher matrix degradation in vacuum than in N2 atmosphere due to the lower N2 partial pressure. After thermally exposed at 1500°C, carbothermal reaction in the matrix leads to the formation of a porous composite, and the composites retains a non-brittle failure behaviour. Meanwhile, SiBCN matrix degradation and SiC fiber strength degradation occurs, which results in significant composite strength decrement. Modest increases in the fiber/matrix interfacial shear strength occur upon exposure at temperatures up to 1350°C, and then significantly reduced after expsoure at 1500oC in N2.

Machine learning models for estimating the compressive strength of rubberized concrete subjected to elevated temperature: Optimization and hyper-tuning

The incorporation of rubber fibers (RFs) brings about significant divergence in the characteristics of rubberized concrete when contrasted with traditional varieties. Thus, raising concerns about performance under elevated temperature and prolonged exposure. This study effectively addresses the challenges of incorporating rubber fibers in concrete by using artificial neural network (ANN), gene expression programming (GEP), and bagging to examine the impact of input factors such as water-to-cement ratio (W/C), rubber fiber content (RF), elevated temperature (T), and exposure duration (t) on air-cooled compressive strength (CSA). The comprehensive literature review and advanced modeling techniques reveal that ANN excels in capturing complex relationships. In addition, GEP provides clear and accurate models through its unique approach, and Bagging enhances model stability and accuracy. These methods together offer a robust framework for estimating the CSA of rubberized concrete. Thus, contributing valuable insights for optimizing its use in construction. All three models exhibited strong performance, with the ANN emerging as the most effective choice among the evaluated models. Notably, ANN displayed the highest coefficient of determination (R2) value of 0.984, indicating its superior predictive accuracy compared to both GEP (0.982), and bagging (0.970). Moreover, ANN demonstrated the lowest mean absolute error (MAE) score of 0.621 and root mean square error (RMSE) of 0.867, underscoring its precision in forecasting the CSA of rubberized concrete with minimal deviation from experimental values. In addition, the SHapley Additive exPlaination (SHAP) method is employed to comprehend the model estimations. The ICE and PDP plots demonstrate an initial increase in CSA up to 150°C, followed by a significant decrease as temperature rises. Furthermore, CSA decreases with higher RF contents, and linearly declines with increasing W/C ratio. The SHAP analysis provides clear evidence of the strong negative correlation between T and CSA, along with a negative association with RF. A graphical user interface has been developed to estimate the CSA of rubberized concrete, enabling efficient and user-friendly model interaction without the need for physical experimentation.

Compressive mechanical performance and microscopic mechanism of basalt fiber-reinforced recycled aggregate concrete after elevated temperature exposure

To improve the mechanical properties of recycled aggregate concrete (RAC) after elevated temperature exposure, this study employed basalt fiber (BF) as reinforcing material incorporated into RAC. The replacement ratio of recycled coarse aggregate (RCA), the content of BF, and the temperature were utilized as the change parameters, and 27 groups of basalt fiber reinforced recycled aggregate concrete (BFRRC) specimens were designed to carry out the compressive strength test after elevated temperature. The heating rate was set at 2.5 °C/min to avoid any possible explosion of the cylindrical specimen during the heating process. The specimens were treated for 6h after reaching the desired temperature, and then the furnace door was opened for natural cooling to room temperature. After observing the physical properties of the specimens, the basic mechanical properties test was carried out, and the microscopic mechanism was analyzed in depth by electron microscopy. The results showed that the defects inherent in RCA and the continuous accumulation of elevated temperature damage gradually reduced the compressive mechanical performance of BFRRC but that the toughening and cracking-resistance action of BF effectively improved the compressive mechanical performance of BFRRC. BF enhanced the compressive mechanical performance of RAC through bridging and crack resistance action mechanisms, but the higher the temperature became, the smaller the enhancement was. The cube compressive strength and axial compressive strength of the specimens decreased with the increase of temperature. With the same replacement ratio and fiber dosage, increasing the temperature from 300 °C to 600 °C, the decrease in cube compressive strength and axial compressive strength was the most significant, which was between 36.4 %–48.1 % and 51.1 %–62.6 %, respectively.

Recycling of Waste Granodiorite Powder as a Partial Cement Replacement Material in Ordinary Concrete

Abstract In this study, the effect of using waste granodiorite powder (WGP) as a cement replacement material in percentages ranging from 1 to 9% on various physical and mechanical properties of ordinary concrete was investigated. The resistance of produced concretes with WGP to the high temperature effects on the 28 days compressive strength were studied as well. Granodiorite is one of the well-known igneous rocks that have been used in previous research as a replacement for coarse or fine aggregates due to the hardness of its grains. However, rare studies have investigated its powder as a partial cement replacement material. Results showed the ability of investigated WGP with high surface area to act as a supplementary cementitious material that contributed to enhance the results of mechanical and physical properties of concrete. At traditional room temperature, the optimal replacement percentage was 7%, where the 28 days compressive and tensile strengths were improved by 28.3% and 17.3%, respectively. The optimal replacement ratio varied between 7 and 9% in the case of high temperatures, according to exposure time and temperature degree. Statistical and sensitivity analysis was conducted on 66 available compressive strength value represents all variables before and after elevated temperature exposure. While the regression equation showed good R2 value of 85.3%, sensitivity analysis indicated that compressive strength value is most sensitive to temperature, followed by WGP ratio and exposure time, with importance values of 56, 26, and 18 %, respectively. Results showed also that the setting times and consistency was decreased with increasing the replacement ratio with WGP, while the workability was slightly improved up to 5% replacement ratio. Furthermore, microstructure analysis showed that WGP can help to densify the concrete matrix due to its small size and ability to fill the interstitial voids in the concrete matrix.

Machine learning enhanced modeling of steel‐concrete bond strength under elevated temperature exposure

AbstractThis study uses machine learning techniques to investigate the bond strength between steel and concrete under various elevated temperature scenarios. Five distinct machine learning algorithms, including Random Forest (RF), XGBoost, AdaBoost, Decision Tree, Linear Regression, and hyperparameteric optimisations, were used to predict changes in bond strength. The models underwent rigorous optimisation using GridSearchCV to achieve optimal performance. In this study, we evaluated several metrics such as Mean Squared Error, Root Mean Squared Error, Mean Absolute Error, and coefficient of determination (R2) Score to compare and assess the models' prediction capabilities. After optimisation, results indicate that the RF model exhibited exceptional performance in estimating bond strength across different temperature conditions, demonstrating minimal errors and a high R2 Score. Visual comparisons of actual and predicted values further confirmed the efficacy of the RF model in capturing complex fluctuations in bond strength. The findings of this study underscore the potential of machine learning models, particularly the optimized RF method, in accurately predicting bond strength under varying thermal conditions, with promising implications for engineering and construction practices.

Interface bonding characteristics of 3D printed ultra-high performance concrete after elevated temperatures

This study explored the influence of elevated-temperature exposure and interlayer time intervals on the interface bonding strength of hybrid-fibre 3D printed ultra-high-performance concrete (3DP-UHPC), and analysed the potential mechanisms driving these observed results. A relationship model for the bonding strength of hybrid fibre 3DP-UHPC in elevated-temperature environments was proposed. Results revealed that at 800 °C, localized damage occurred in 3DP-UHPC, but the addition of 0.5 % polypropylene fibres delayed the occurrence of spalling behaviour and enhanced its elevated-temperature resistance. Furthermore, as the time interval increased, the bonding strength of 3DP-UHPC gradually decreased, particularly at temperatures above 400 °C, where the melting and volatilization of polypropylene fibres negatively affected the bonding strength. The study suggested that polypropylene fibres inhibited spalling behaviour of 3DP-UHPC after elevated temperatures through moisture loss and thermal stability. However, they may also lead to interface weakening, resulting in a decrease in bonding strength. These findings provide important guidance for further development and design of 3DP-UHPC structures in elevated-temperature environments.

Effect of elevated temperature and hydrocortisone addition on the proliferation of fibroblasts

Hyperthermia along with hydrocortisone (HC) are proven teratogens that can negatively influence embryo development during early pregnancy. Proliferation of cells is one of the main developmental processes during the early embryogenesis. This study was focused on testing the effect of elevated temperature and HC addition on proliferation of cells in in vitro cultures. The V79-4 cell line was treated with HC and cultured in vitro at 37 °C or 39 °C, respectively. To reveal the effect of both factors, the proliferation of cells cultured under different conditions was evaluated using various approaches (colony formation assay, generation of growth curves, computation of doubling times, and mitotic index estimation). Our results indicate that a short-term exposure to elevated temperature slightly stimulates and a long-term exposure suppresses cell proliferation. However, HC (0.1 mg/ml) acts as a stimulator of cell proliferation. Interestingly, the interaction of HC and long-term elevated temperature (39 °C) exposure results in at least partial compensation of the negative impact of elevated temperature by HC addition and in higher proliferation if compared with cells cultured at 39 °C without addition of HC.

Application of metaheuristic algorithms for compressive strength prediction of steel fiber reinforced concrete exposed to high temperatures

The demand for steel fiber-reinforced concrete (SFRC) in construction has surged, particularly due to its enhanced fire resistance, leading to extensive research on its residual properties after elevated temperature exposure. However, conducting experimental tests can be a time-consuming process, demanding significant resources in terms of time, cost, and human resources. In contrast, machine learning (ML) models can rapidly simulate outcomes, enabling researchers to explore a wide range of scenarios efficiently. The previous literature studies used either ensemble or individual models; however, this study made a unique approach to utilize hybrid models, which are more precise compared to the other types of ML models. Accordingly, a data-rich framework containing 304 data samples was utilized in this study to develop an efficient and robust predictive model for the compressive strength (CS) of SFRC at higher temperatures. Support vector regression (SVR) in combination with three distinct optimization algorithms, specifically, particle swarm optimization (PSO), the firefly algorithm (FFA), and grey wolf optimization (GWO) were utilized to develop the hybrid models. In addition, typical ML techniques such as random forest (RF) and decision tree (DT) were used for comparative analysis. Among the five models, the SVR-FFA hybrid model showcased superior predictive accuracy, with the SVR-GWO model following closely. The correlation coefficients (R) for both models exceeded 0.99. The SVR-FFA model demonstrated relative root mean square error (RMSE) and mean absolute error (MAE) values of 0.0375 and 0.0248, respectively, while the SVR-GWO model exhibited corresponding values of 6.0560 and 5.1326. The SHapley Additive exPlanation (SHAP) technique revealed that the influence of temperature is more significant compared to the heating rate. Moreover, a considerable enhancement was observed in CS as the steel fiber volume fraction (Vf) reached 1.5%; on the other hand, no further improvement was noticed when Vf exceeded the 1.5% threshold. The proposed hybrid models are robust and accurate methods to estimate the CS of SFRC in field applications.

Effects of elevated temperature exposure on the mechanical properties of recycled fine aggregate concrete

ABSTRACT In this work, a compound waste material was made up of raw construction waste concrete, waste tiles, and waste bricks was mixed at a weight ratio of 6:3:1. They were ground into recycled fine aggregates (RFA). RFA substituted the local river sand in proportions of 0%, 30%, 50%, 70%, and 100% for preparing recycled fine aggregate concrete (RFAC) with varied water-to-cement ratios. It intended to explore concrete’s mechanical properties and ultrasonic pulse velocity changes before and after high temperatures (300–800°C). The loss on ignition (LOI) of concrete was simultaneously determined to compare the performance in resisting elevated temperature. Test results presented that the higher the replacement ratio of RFA, the gradually higher the reduction in the concrete splitting tensile, compressive, and residual compressive strengths and ultrasonic pulse velocity after elevated temperature exposure. A rapid reduction was especially found at the heated temperature of exceeding 440°C. Furthermore, the old cement paste adhered to the surface of the raw construction waste had a relatively higher LOI. This led to the consequence that the RFAC had an increased LOI with the increment of the RFA replacement ratio, while the LOI of RFAC dropped with the increment of the originally heated temperature.

Thermal stability and strength degradation of lithium slag geopolymer containing fly ash and silica fume

This paper investigates the thermal stability of lithium slag geopolymer (LSG) containing fly ash (FA) and silica fume (SF) exposed up to 900˚C. The effects of elevated temperatures on the microstructural evolution were investigated by thermogravimetric analysis (TGA), X-ray Diffraction (XRD), mineral analysis, surface porosity, and compressive strength of LSG modified by optimum incorporation of fly ash and silica fume. The results indicated that elevated temperature exposure significantly affects compressive strength, surface porosity, void size, weight loss, and phase transformation of fly ash incorporated lithium slag geopolymer (LSGFA) and silica fume incorporated geopolymer (LSGSF). The maximum loss in compressive strength of 44.07% was observed in LSGFA compared to 31.50% loss in LSGSF after exposure at 900˚C. The weight loss of LSGSF was higher than that of LSGFA between 500 and 800˚C and 800–1000˚C indicating a higher degree of dehydroxylation, crystal phase transformation, and viscous sintering observed in the former mix. A larger shrinkage cracking was observed in LSGSF by self-desiccation of the aluminosilicate paste matrix by dehydroxylation of mordenite molecules. Therefore, the degradation of compressive strength is governed by the combination of the crystallization of aluminosilicate gel and the formation of voids.

Thermal impact on superplasticizer-free metakaolin-nano-silica binary and ternary mortars

ABSTRACT Binary and ternary blended mortars were prepared by replacing ordinary Portland cement with varying percentages of MK (10%, 15%, 20%) and NS (1.5%, 3%, 4.5%) to study their performance under elevated temperatures. Superplasticisers were not used to ensure an unadulterated assessment of thermal performance. Heat resistance was evaluated based on the area under the relative residual compressive strength curve concerning temperature. After heat treatment, surface cracking, spalling frequency, and weight loss were assessed. Morphological changes due to elevated temperature exposure were observed through SEM analysis. The findings indicate that the ternary mortar mix with 10% MK and 1.5% NS exhibited the highest thermal resistance. Increased MK and NS proportions resulted in decreased thermal resistance. The mortars remained crack-free until 350°C, with spalling observed at 650°C. Mortar MK10NS3 displayed higher spalling frequency due to its denser pore structure, showcasing the potential of MK and NS in enhancing thermal resistance.

Epoxy-Printed Circuit Board Interfacial Fracture Reliability Under Three-Point and Four-Point Bend Loading After Sustained Elevated Temperature Exposure

Abstract The survivability and reliability of commercial electronic components under very high thermo-mechanical loads are improved using underfilling and potting methods. Potting protects from operating conditions such as moisture, water, or corrosive agents. Furthermore, potting offers damping against shock and vibrations, heat dissipation, and structural support. Being one of the most cost-efficient methods, potting greatly increases reliability and therefore reduces costs for replacements and repairs. It also addresses trapped hot air issues better than other restraint technologies. In potted electronic assemblies, interfacial delamination at the epoxy and printed circuit board (PCB) interface has been one of the major failure modes. Interfacial delamination happens at the epoxy/PCB interface under dynamic shock loads, which leads to failures at the solder interconnects of the electronic components. Sustained operation and storage at elevated temperatures change the interfacial characteristics at the epoxy/PCB interface. This research is focused on interfacial failure mechanics at epoxy/PCB interfaces with high-temperature isothermal aging. In the selection of the epoxy potting material and the reliability assessments of the supplemental restraint systems, fracture parameters such as steady-state strain energy release rate stress and fracture toughness are critical. Rectangular beam specimens of the epoxy/PCB interface are fabricated for different potting compounds, and the fracture behavior is studied under quasi-static monotonic three-point and four-point bend loads. One of the main differences between three-point and four-point bend loading is that the maximum bending stress occurs at the midpoint under the point of loading of the specimen in three-point bending, whereas the peak stress is distributed over the section of the specimen between the loading points in four-point bending. Four different potting compounds with diverse properties have been studied. The recommended curing schedule from the manufacturer has been chosen and followed for all the potting compounds. The epoxy/PCB interfacial samples are aged at a high temperature of 100 °C for 30–180 days. Damage has been assumed to happen at the epoxy/PCB interface under dynamic loads. The critical load of crack initiation for the epoxy/PCB interface has been determined from the experimental findings, and it is used in the computation of fracture toughness values. The fracture toughness values are compared for the various epoxy/PCB systems based on the number of days of thermal aging and the method of flexure testing. A cohesive zone model has been constructed for predominantly mode-I delamination with four-point bend stress to predict the interfacial delamination behavior at the epoxy/PCB interfaces. It has been assumed that the bulk material is linear elastic during the bending load. The cohesive zone has been modeled at the interface, where the interfacial fracture has been assumed to occur. The fracture behavior in the simulation is predicted based on the fracture parameters determined through the experiment. The computed cohesive zone parameters are unique to the interfaces, and they can be used across various applications with the same epoxy/PCB interface to predict interfacial delamination and to select a more suitable potting material.

Effect of elevated temperature exposure on the flexural behavior of steel–polypropylene hybrid fiber-reinforced concrete

Effect of elevated temperature exposure on the flexural behavior of steel–polypropylene hybrid fiber-reinforced concrete

Numerical analysis of dynamic compressive properties of basalt fiber engineered cementitious composites after elevated temperature

The basalt fiber engineered cementitious composites (BF-ECC) was a superior cementitous material when used for tension loading. And it can prevent the development of wide cracks. In this paper, the dynamic compressive mechanics of BF-ECC after elevated temperature exposure(100 °C, 200 °C, 400 °C and 600 °C) is investigated. Parameter analyses are conducted to investigate the effect of the temperature and strain rate. In addition, a dynamic constitutive model including the damage factor function and the temperature effect function is constructed. It is extended and applied to the rate-type constitutive relation of BF-ECC materials after elevated temperature, and the numerical analysis results are compared with the experimental results to verify the applicability of the model.

Indirect Tensile Properties of Basalt Fiber-reinforced Recycled Aggregate Concrete after Elevated Temperature Exposure

Indirect Tensile Properties of Basalt Fiber-reinforced Recycled Aggregate Concrete after Elevated Temperature Exposure

Effects of one-sided thermal shock and hold on alumina-based oxide/oxide ceramic matrix composites for temperatures in excess of 1200 °C

Nextel™720/alumina based ceramic matrix composite plates were subjected to one-sided thermal shock and 30-minute hold at 1100 °C, 1250 °C, 1400 °C and 1550 °C. Post exposure, the plates were evaluated for physical, structural, and microstructural changes using state-of-the art characterization techniques as well as standard mechanical testing procedures. Physically, no significant mass or dimensional changes were noted, while the surface roughness decreased on the exposed side for all the cases. Structurally, both the tensile and flexural strengths decreased for the 1550 °C case, but not for the other temperatures. In addition, short-beam strength tests showed no effect on interlaminar strength as a result of the elevated temperature exposures for the 30-minute duration considered. Microstructurally, SEM/EDS evaluations showed no significant change in the microstructure or element composition on the exposed and back sides. However, mercury intrusion porosity measurements did show a change in pore size distribution due to the combined effect of matrix shrinkage and further matrix microcracking. Combined results show that the operational limit of the composite can be pushed significantly beyond 1200 °C for shorter (in minutes) durations provided it is structurally viable for the application sought.

Mechanical properties and microstructure of nano-modified geopolymer concrete containing hybrid fibers after exposure to elevated temperature

Geopolymer concrete (GPC) has a promising future as an eco-friendly material for refractory engineering applications. It is significant to investigate the changes in mechanical properties of nano-modified geopolymer concrete containing hybrid fibers (NHF-GPC) after exposure to elevated temperature for construction fire-resistant design. In this study, the macro-mechanical property tests and micro tests were carried out on geopolymer concrete containing hybrid fibers with different nano-SiO2 (NS) contents (0–2 %) after exposure to different elevated temperatures (200–800 °C). The coupling relationships of compressive, tensile and flexural strengths of NHF-GPC with temperature and NS content were established separately. And the relative sound velocity and damage degree were selected as acoustic parameters to construct a relationship model with the compressive strength loss rate. The results indicated that the compressive, tensile and flexural strengths of NHF-GPC were enhanced at 200 °C, while higher temperatures significantly reduced the mechanical properties of NHF-GPC. At the same temperature, the compressive, tensile and flexural strengths of NHF-GPC all increased and then decreased with increasing NS content, and reached the peak at a NS content of 1.5 %. The matrix became denser at 200 °C, while at greater than 200 °C, the water evaporated, the number of microcracks increased abruptly, and the porosity enlarged. The mass loss of NHF-GPC after elevated temperature mainly occurred below 600 °C, when there was no new material phase generated inside the matrix. And the established model can be used for the identification on the strength damage degree after elevated temperature exposure of NHF-GPC, and it can offer a conceptual foundation for the assessment of elevated temperature damage and the life prediction of GPC in the practical applications.