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1
Belaoura, Mebarek, Dalila Chiheb, Mohamed Nadjib Oudjit, and Abderrahim Bali. "Temperature Effect on the Mechanical Properties of Very High Performance Concrete." International Journal of Engineering Research in Africa 34 (January 2018): 29–39. http://dx.doi.org/10.4028/www.scientific.net/jera.34.29.
Повний текст джерелаАнотація:
This study aims at a better understanding of the behaviour of very high performance concretes (VHPC) subjected to high temperatures. The temperature increase within the concrete originating from the hydratation exothermic reaction of cement is emphasized by the mass effect of the structures and can lead to thermal variations of around 50°C between the heart and the structures walls. These thermal considerations are not without consequence on durability and the physical and mechanical properties of very high performance concrete, such as the compressive strength. This work is an experimental research that shows the effects of temperature on the mechanical properties of very high performance concrete (VHPC) and compares them with those of conventional concrete and HPC. Test specimens in usual concrete, HPC and VHPC are made, preserved till maturity of the concrete, and then subjected to a heating-cooling cycle from room temperature to 500°C at heating rate 0.1°C/min. Mechanical tests on the hot concrete and cooling (air and water) were realized. The results show that the mechanical characteristics of VHPC (density, compressive strength, tensile strength and elastic modulus) decrease with increasing temperature, but their strength remains higher than that of conventional concrete.
2
Zhang, Nan, Juan Liao, Tao Zhang, Wen Zhan Ji, Bao Hua Wang, and Dong Hua Zhang. "The Effect of Mineral Admixtures on Mechanical Properties of High Performance Concrete at very Low Temperature." Applied Mechanics and Materials 584-586 (July 2014): 1509–13. http://dx.doi.org/10.4028/www.scientific.net/amm.584-586.1509.
Повний текст джерелаАнотація:
The effect of very low temperature on high performance concrete (HPC) mechanical properties is studied by using a reasonable testing method. The results show that the compressive strengths of concrete are increasing with lower temperatures. Fly ash (FA), compared to ground granulated blast-furnace slag (GGBFS), is positive to the compressive strength increasing at low temperature. The splitting tensile strengths of concrete appear a maximum at-40°C~-80°C. The compound replacement by GGBFS and FA makes the splitting tensile strength present the extreme value at higher temperature. At very low temperature, the single or compound replacement by mineral admixtures can result in the difference of the relationship between compressive strength and splitting tensile strength, and the degradation of concrete subjected to cold-thermal shocks.
3
Yuan, Guang Lin, Jing Wei Zhang, Jian Wen Chen, and Dan Yu Zhu. "Deterioration of Mechanical Properties of High-Strength Pumpcrete after Exposure to High Temperatures." Advanced Materials Research 168-170 (December 2010): 564–69. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.564.
Повний текст джерелаАнотація:
This paper makes an experimental study of mechanical properties of high-strength pumpcrete under fire, and the effects of heating rate, heating temperature and cooling mode on the residual compressive strength(RCS) of high-strength pumpcrete are investigated. The results show that under air cooling, the strength deterioration speed of high-strength concrete after high temperature increases with the increase of concrete strength grade. Also, the higher heating temperature is, the lower residual compressive strength value is. At the same heating rate (10°C/min), the residual compressive strength of C45 concrete after water cooling is a little higher than that after air cooling; but the test results are just the opposite for C55 and C65 concrete. The strength deterioration speed of high-strength concrete after high temperature increases with the increase of heating rate, but not in proportion. And when the heating temperature rises up between 200°C and 500°C, heating rate has the most remarkable effect on the residual compressive strength of concrete. These test results provide scientific proofs for further evaluation and analysis of mechanical properties of reinforced-concrete after exposure to high temperatures.
4
Canbaz, Mehmet, and Erman Acay. "Effect of high temperature on SCC containing fly ash." Challenge Journal of Concrete Research Letters 12, no. 1 (March 12, 2021): 1. http://dx.doi.org/10.20528/cjcrl.2021.01.001.
Повний текст джерелаАнотація:
The effect of high temperature on self-compacting concrete, which contains different amounts of fly ash, has been investigated. By considering the effect of concrete age and increased temperatures, the optimum fly ash-cement ratio for the optimum concrete strength is determined using experimental studies. Self-compacting concrete specimens are produced, with fly ash/cement ratios of 0%, 20% and 40%. Specimens were cured for 28, 56 and 90 days. After curing was completed, the specimens were subjected to temperatures of 20°C, 100°C, 400°C, 700°C and 900°C for three hours. After the cooling process, tests were performed to determine the unit weight, ultrasonic pulse velocity and compressive strength of the specimens. According to the experiment results, an increase in fly ash ratio causes a decrease in the compressive strength of self-compacting concrete. However, it positively contributes to self-compaction and strength loss at high temperatures. The utilization of fly ash in concrete significantly contributes to the environment and the economy. For this reason, the addition of 20% fly ash to concrete is considered to be effective.
5
Amin, Mohamed, and Khaled Abu el-hassan. "Effect of different fiber types on the mechanical properties of normal and high strength concrete at elevated temperatures." Challenge Journal of Concrete Research Letters 12, no. 1 (March 12, 2021): 30. http://dx.doi.org/10.20528/cjcrl.2021.01.004.
Повний текст джерелаАнотація:
The effects of the types of fibers on mechanical properties of normal and high strength concrete under high temperature, up to 700 °C, was investigated. Three different- type fiber; "Steel Fiber (SF), Glass Fiber (GF) and Polypropylene Fiber (PPF)" are added into the concretes in five different ratios (0, 0.50, 1.00, 1.50 and 2.0%)of the volume under the following temperatures; 22, 100, 400 and 700°C. The results indicate that all the different types of fibers researched contribute to both the compressive and flexural strengths of concrete under high temperature, however, it is also found that this contribution decreases with an increase in temperature. The flexural strengths and compressive strengths for NSC and HSC mixes at 28 days under high temperature decreases as the temperature increases especially up to 400°C. Also, the best compressive and flexural strengths performance under high temperature was also those of SF. The compressive strength of the concrete incorporating SF was reduced under high temperature only, while the mixes containing PPF and GF were reduced under high temperature or with fiber addition. The optimum fiber addition ratios of the mixes containing PPF and GF are between 0.5-1.0 percent by volume. And for SF, it is 1.5% by the volume.
6
VefaAkpınar, Muhammet. "EFFECT OF GLASS BEAD AND ZEOLITE IN CONCRETE UNDER HIGH TEMPERATURE." International Journal of Research -GRANTHAALAYAH 4, no. 12 (December 31, 2016): 65–71. http://dx.doi.org/10.29121/granthaalayah.v4.i12.2016.2393.
Повний текст джерелаАнотація:
The paper presents the impact of high temperature on concrete with glass bead and zeolite in its mixture. It is desired to reduce the concrete surface temperature when it is exposed to high temperature. In this study, different range of proportions of glass beads (%10, %20, %30) and zeolite (%10, %30) were added into the C30/37 strength class concrete as a fine aggregate and Portland cement, respectively. Surface temperatures of concrete samples were measured when concrete was under about 3000°C flame for a short time. It was determined that, using glass bead and zeolite together in concrete reduces surface temperature significantly under high temperature. The study presented herein provides important results on regulating concrete mixture if there is any risk to be exposed to high temperature.
The study presented herein provides important results on regulating concrete mixture if there is any risk to be exposed to high temperature. The main research question is “Is it possible to reduce surface temperature of concrete when it is exposed to very high temperature by using glass bead and zeolite in concrete mixture”.
10 different types of concrete mixtures were designed to study the effects of concrete and zeolite on compressive strength and surface temperatures of concrete.
It was determined that using glass bead as a fine aggregate and zeolite, significantly affects concrete surface temperature and temperature differences of both sides when concrete is exposed to very high temperature.
Using glass bead and zeolite in concrete for fire resistance hasn’t been searched before. In this study it was determined that it is possible to get lower surface temperatures by using glass bead and zeolite in concrete mixture. The ideal proportion was %20 for glass bead and %30 for zeolite in the mixture to obtain lowest surface temperatures and meet the compressive strength requirements. These types of mixtures can also be examined for concrete pavements to get lower temperature gradients in summer and obtain less thermal cracking on concrete road.
7
Liu, Chuan Xiong, Yu Long Li, Bing Hou, Wei Guo Guo, and Jin Long Zou. "Dynamic Compressive Behavior of Concrete at High Temperatures." Advanced Materials Research 217-218 (March 2011): 1811–16. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.1811.
Повний текст джерелаАнотація:
For investigating the effect of temperature on the dynamic properties of concrete material, tests for cylindrical concrete specimens at 23°C ~ 800°C were carried out by using Split Hopkinson Pressure Bar (SHPB) apparatus, and the strain rates ranged from 30/s to 220/s. Effects of temperature and strain-rate on the dynamic behavior of concrete were analyzed. The results show that: above 4000C, the dynamic compressive strength of concrete decreases with increasing temperature, and the enhancements of strain-rates on the compressive strength of concrete depend significantly on temperatures. Moreover, both strain-rate and temperature can enhance the peak strain of concrete.
8
Zhao, Jun, Kang Wang, Shuaibin Wang, Zike Wang, Zhaohui Yang, Eskinder Desta Shumuye, and Xinglong Gong. "Effect of Elevated Temperature on Mechanical Properties of High-Volume Fly Ash-Based Geopolymer Concrete, Mortar and Paste Cured at Room Temperature." Polymers 13, no. 9 (May 2, 2021): 1473. http://dx.doi.org/10.3390/polym13091473.
Повний текст джерелаАнотація:
This paper presents results from experimental work on mechanical properties of geopolymer concrete, mortar and paste prepared using fly ash and blended slag. Compressive strength, splitting tensile strength and flexural strength tests were conducted on large sets of geopolymer and ordinary concrete, mortar and paste after exposure to elevated temperatures. From Thermogravimetric analyzer (TGA), X-ray diffraction (XRD), Scanning electron microscope (SEM) test results, the geopolymer exhibits excellent resistance to elevated temperature. Compressive strengths of C30, C40 and C50 geopolymer concrete, mortar and paste show incremental improvement then followed by a gradual reduction, and finally reach a relatively consistent value with an increase in exposure temperature. The higher slag content in the geopolymer reduces residual strength and the lower exposure temperature corresponding to peak residual strength. Resistance to elevated temperature of C40 geopolymer concrete, mortar and paste is better than that of ordinary concrete, mortar and paste at the same grade. XRD, TGA and SEM analysis suggests that the heat resistance of C–S–H produced using slag is lower than that of sulphoaluminate gel (quartz and mullite, etc.) produced using fly ash. This facilitates degradation of C30, C40 and C50 geopolymer after exposure to elevated temperatures.
9
Sophia, M., and N. Soundarya. "Temperature Effect On Reactive Powder Concrete Using Sillimanite As Fine Aggregate." Journal of Physics: Conference Series 2332, no. 1 (September 1, 2022): 012014. http://dx.doi.org/10.1088/1742-6596/2332/1/012014.
Повний текст джерелаАнотація:
Abstract This study examines the use of sillimanite as a fine aggregate in the production of temperature-resistant reactive powder concrete. The impact of high temperatures on the mechanical strength of reactive powder concrete with High Alumina cement is investigated. The effectiveness of utilizing glass powder and sillimanite on the mechanical properties of RPC at high temperatures is investigated in this research. The samples were heated in the muffle furnace to the desired temperatures and then tested for their residual compressive strength, flexural strength and split tensile strength. The residual values of compressive strength, flexural strength and split tensile strength were measured at the temperature of 270C to 800°C. The weight loss of the specimens after exposure to the elevated temperatures was measured and the values showed enhanced resistance to the high temperature effects. The results demonstrate the greater contribution of glass powder and sillimanite towards the significant improvement of high temperature strength of reactive powder concrete than those made with normal quartz sand as fine aggregate.
10
Peng, G.-F., Y.-C. Jiang, B.-H. Li, J. Zhang, and Y.-X. Shi. "Effect of high temperature on normal-strength high-performance concrete." Materials Research Innovations 18, sup2 (May 2014): S2–290—S2–293. http://dx.doi.org/10.1179/1432891714z.000000000414.
Повний текст джерела
11
Choi, Yeol, Joo-Won Kang, Tae-Yeon Hwang, and Chang-Geun Cho. "Evaluation of residual strength with ultrasonic pulse velocity relationship for concrete exposed to high temperatures." Advances in Mechanical Engineering 13, no. 9 (September 2021): 168781402110349. http://dx.doi.org/10.1177/16878140211034992.
Повний текст джерелаАнотація:
This paper presents the results of an experimental investigation on the relationship between strength and ultrasonic pulse velocity (UPV) of concrete exposed to high temperature, especially for a decision of building remodeling of concrete structures. The experiments were conducted at three different initial compressive strength levels for temperature up to 800°C. UPV, Compressive, and splitting tensile tests and UPV measurements were performed for unheated and heated concrete specimens. The measured UPV values in the present work were correlated with compressive and tensile strengths to estimate the strength of concrete. Based on the results, two linear equations for predicting compressive and tensile strength of concrete at elevated temperatures using UPV have been proposed. It is found that the difference of initial compressive strength of concrete does not have a significant effect on the strength reduction ratio after exposed to high temperatures. In addition, the reduction factors of compressive and tensile strengths in the present work do not well comply with the values of suggested by EN 1992-1-2.
12
Wedatalla, Afaf M. O., Yanmin Jia, and Abubaker A. M. Ahmed. "Curing Effects on High-Strength Concrete Properties." Advances in Civil Engineering 2019 (March 6, 2019): 1–14. http://dx.doi.org/10.1155/2019/1683292.
Повний текст джерелаАнотація:
This study was conducted to investigate the impact of hot and dry environments under different curing conditions on the properties of high-strength concrete. The concrete samples were prepared at a room temperature of 20°C and cured under different curing conditions. Some specimens underwent standard curing from 24 h after casting until the day of testing. Some specimens underwent steam curing in a dry oven at 30°C and 50°C after casting until the day of testing. Other specimens were cured for 3, 7, 21, and 28 days in water and then placed in a dry oven at 30°C and 50°C and tested at the age of 28 days, except for the specimens that were cured for 28 days, which were tested at the age of 31 days, to study the effect of curing period on the strength of concrete exposed to dry and hot environments after moist curing. The effects of hot and dry environments on high-strength concrete with different water/binder ratios (0.30, 0.35, and 0.40), using (30%) fly ash for all mixes, and (0%, 5%, and 10%) silica fume with the binder (450, 480, and 520 kg), respectively, were separately investigated, and the effects of curing under different conditions were evaluated by measuring the compressive strength, flexural strength, microhardness, and chloride diffusion and by assessing the concretes’ microstructure. The relationships between these properties were presented. A good agreement was noted between the concrete compressive strength and concrete properties at different temperatures, curing periods, and curing methods.
13
Křížová, Klára, Jan Bubeník, and Martin Sedlmajer. "Use of Lightweight Sintered Fly Ash Aggregates in Concrete at High Temperatures." Buildings 12, no. 12 (November 29, 2022): 2090. http://dx.doi.org/10.3390/buildings12122090.
Повний текст джерелаАнотація:
This study addresses the issue of the resistance to high temperatures of lightweight concrete lightweighted with sintered fly ash aggregate. Lightweight concretes with different amounts of lightweighting and their properties after loading temperatures of 600, 800 and 1000 °C were investigated. In particular, the effect of high temperature on the mechanical properties of the concrete was determined on the test specimens, and the effect on the microstructure was investigated by X-ray diffraction analysis and scanning electron microscopy. It was found that there is an increase in compressive strength between 0 and 21% up to 800 °C, where the increase in strength decreases with increasing degree of lightening. At 1000 °C, the internal structure of the lightweight concrete destabilized, and the compressive strength decreased in the range of 51–65%. After loading at 1000 °C, the scanning electron microscope showed the formation of spherical-shaped neoplasms, which significantly reduced the internal integrity of the cement matrix in the lightweight concrete due to the increase in their volume. It was found that the lightweight concretes with higher lightweighting showed significantly less degradation due to higher temperature.
14
Benjeddou, Omrane, Herda Yati Katman, Malek Jedidi, and Nuha Mashaan. "Experimental Investigation of the High Temperatures Effects on Self-Compacting Concrete Properties." Buildings 12, no. 6 (May 27, 2022): 729. http://dx.doi.org/10.3390/buildings12060729.
Повний текст джерелаАнотація:
Self-compacting concrete (SCC), which appeared in the 1980s in Japan, is a concrete that differs from others by its high fluidity. The constituents of SCC can be quite different from those of ordinary concretes. They can differ both in their proportions and in their choice. Given the method of installation of SCCs, particular attention is paid to the study of their physical and mechanical characteristics. In this context, experimental tests were conducted to assess the effect of high temperatures on the behavior of SCC. For this purpose, a SCC and ordinary concrete (OC) were tested at temperatures of 20, 150, 300, 450, and 600 ∘C. Prismatic specimens of dimensions 100 × 100 × 400 mm3, cylindrical specimens of dimensions 160 × 320 mm, and parallelepiped specimens of dimensions 270 × 270 × 40 mm3 were prepared for physical (thermal conductivity) and mechanical (compressive strength, elastic modulus, flexural strength, and ultrasonic pulse velocity) tests. The results showed an increase in the compressive strength for SCC between 150 and 300 ∘C following an additional hydration of the cementitious matrix. The residual flexural strength of the concretes decreases progressively with the increase in temperature. This reduction is about 90% from 450 ∘C to 600 ∘C. The results also showed that the thermal conductivity of concrete decreases as the temperature increases and can reach a value of 1.2 W/mK for the heating temperature of 600 ∘C.
15
Lv, Nao, Hai-bo Wang, Qi Zong, Meng-xiang Wang, and Bing Cheng. "Dynamic Tensile Properties and Energy Dissipation of High-Strength Concrete after Exposure to Elevated Temperatures." Materials 13, no. 23 (November 24, 2020): 5313. http://dx.doi.org/10.3390/ma13235313.
Повний текст джерелаАнотація:
In view of the devastating outcomes of fires and explosions, it is imperative to research the dynamic responses of concrete structures at high temperatures. For this purpose, the effects of the strain rate and high temperatures on the dynamic tension behavior and energy characteristics of high-strength concrete were investigated in this paper. Dynamic tests were conducted on high-strength concrete after exposure to the temperatures of 200, 400, and 600 °C by utilizing a 74 mm diameter split Hopkinson pressure bar (SHPB) apparatus. We found that the quasi-static and dynamic tensile strength of high-strength concrete gradually decreased and that the damage degree rose sharply with the rise of temperature. The dynamic tensile strength and specific energy absorption of high-strength concrete had a significant strain rate effect. The crack propagation law gradually changed from directly passing through the coarse aggregate to extending along the bonding surface between the coarse aggregate and the mortar matrix with the elevation of temperature. When designing the material ratio, materials with high-temperature resistance and high tensile strength should be added to strengthen the bond between the mortar and the aggregate and to change the failure mode of the structure to resist the softening effect of temperature.
16
Yan, H. Q., and Q. Y. Wang. "Effect of Elevated Temperature on the Mechanical Behavior of Natural Aggregate Concrete." Key Engineering Materials 452-453 (November 2010): 841–44. http://dx.doi.org/10.4028/www.scientific.net/kem.452-453.841.
Повний текст джерелаАнотація:
Reinforced concrete construction is very common these days and extensively used both in industrial and commercial buildings. With the gradual rise in occurrences of fire accidents in recent years, a more thorough and quantitative understanding of the damage phenomenon in natural aggregate concrete structures is required. However, little research has been done to study natural aggregate concrete behavior under high temperatures. The mechanical behavior of concrete could actually be more complex under high temperature conditions than at room temperature, for instance. Restoration and reinforcement of the structures exposed to fire may have to be based on residual strength analysis and therefore require a correlation between temperature and mechanical properties. Thus, in order to meet the modern challenges of rapid engineering advances and societal development, further research on the concrete material and its structural behavior at high temperatures becomes extremely important. The present paper deals with investigations on the effect of high temperature exposure on the compressive strength of natural aggregate concrete. Experiments were conducted to study the compressive strength variations with increasing temperatures, up to 700 °C, and the subsequent cooling modes such as natural and spray cooling. Results show that the compressive strength gradually decreases with increasing temperatures.
17
Wang, Huailiang, Min Wei, Yuhui Wu, Jianling Huang, Huihua Chen, and Baoquan Cheng. "Mechanical Behavior of Steel Fiber-Reinforced Lightweight Concrete Exposed to High Temperatures." Applied Sciences 11, no. 1 (December 24, 2020): 116. http://dx.doi.org/10.3390/app11010116.
Повний текст джерелаАнотація:
The mechanical characteristics of steel fiber-reinforced lightweight concrete (SFLWC) under high temperatures are studied in this paper. Different concrete matrices, including all-lightweight concrete (ALWC) and semi-lightweight concrete (SLWC), and different steel fibers with hooked ends and crimped shapes are considered as objects. In addition, normal-weight limestone aggregates concrete (NWC), no-fiber ALWC, and SLWC were tested after high-temperature treatment as a control group. The temperature effects on the splitting tensile strength, ultrasonic pulse velocity, compressive stress–strain curve, elastic module, peak strain, and axial compressive strength of the SFLWC were investigated. The results showed that, with increasing exposure temperature, both the axial compressive strength and the elastic modulus decreased, while the axial peak strain has a certain increase, and hence the stress–strain curves were gradually flattened. The toughness of all the concretes increased first and then reduced with increasing temperature, while the specific toughness of all the concretes increased with the increase in temperature. Compared with NWC and SLWC, ALWC had a better capacity to resist high temperatures, especially temperatures > 400 °C. Adding steel fibers can improve the capacity of energy absorption, specific toughness, and residual splitting tensile strength of lightweight concrete (LWC) before and after it is exposed to high temperatures. Based on a regression analysis, a segmented constitutive equation for LWC and SFLWC under uniaxial compression was derived from fitting the experimental findings, and the fitting curve agrees well with the test results.
18
Zavalis, Robertas, and Arnoldas Šneideris. "THE EFFECT OF HIGH TEMPERATURE ON REINFORCED CONCRETE STRUCTURES." Engineering Structures and Technologies 2, no. 1 (March 31, 2010): 12–21. http://dx.doi.org/10.3846/skt.2010.02.
Повний текст джерелаАнотація:
The article represents the behaviour of reinforced concrete and its components (concrete and reinforcement) under high temperature. The comparing analysis of the experimentally and theoretically obtained results has been performed. The carried out experiment has disclosed that the mechanical properties of concrete alters differently in cases of temperature rise and theoretical reference. The most visible difference has been noticed at a temperature of 100 °C (Fig 4, Fig 5). The main fire resistance calculation basics are discussed. The temperature fields of the reinforced concrete element cross-section are calculated according to the standard fire curve using the program COSMOS/M of the finite element method. Concrete thermal properties, thermal conductivity and specific heat capacity dependence on temperature are taken into account in the model (Fig 10, Fig 11). By means of this model, the corresponding algorithm (Table 2) was made and can be used for obtaining temperature distribution for the reinforced concrete element of different cross-sections. According to the received temperature fields and applying the zone method, the influence of differences in theoretical and experimental results on element load bearing capacity is determined. The residual strength of the element considering the theoretical reduction curve of concrete strength is 5% larger than the results obtained in cases of 30 and 60 minutes heating. 90 and 120 minutes heating indicates that element strength is only 2% larger than the results calculated experimentally. The reduced zone dimension determined due to a decrease in the reduction coefficient at a temperature of 100 °C has affected residual element strength.
19
Peng, Gai Fei, Xiao Li Wang, and Lin Wang. "Influences of Glassified Micro-Bubble on Mechanical Properties of Ultra-High-Strength Concrete after Exposure to High Temperature." Key Engineering Materials 629-630 (October 2014): 259–64. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.259.
Повний текст джерелаАнотація:
An experimental investigation was conducted to study residual mechanical properties of Ultra-High-Strength concrete with different dosages of glassified micro-bubble after exposure to high temperature. After exposure to different target temperatures (room temperature, 200 °C, 400 °C, 600 °C,800 °C), residual mechanical properties (residual compressive strength, residual tensile splitting strength, residual fracture energy) of Ultra-High-Strength concrete under different conditions including 1 water-binder ratios (0.18), 3 different contents of glassified micro-bubble (0%, 40%, 60%) were all investigated. The effect of different dosage of glassified micro-bubble was studied on residual mechanical properties of Ultra-High-Strength concrete after exposure to high temperature. The results indicate that the variations of different kinds of Ultra-High-Strength concrete with different dosage of glassified micro-bubble are basically the same. With the increase of temperature, the residual mechanical properties increase at first, then decrease. The residual mechanical properties decrease after exposure to high temperature of 800 °C.
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Kim, Seungwon, Topendra Oli, and Cheolwoo Park. "Effect of Exposure to High Temperature on the Mechanical Properties of SIFRCCs." Applied Sciences 10, no. 6 (March 21, 2020): 2142. http://dx.doi.org/10.3390/app10062142.
Повний текст джерелаАнотація:
Many researchers have studied explosion prevention and fire resistance of high-strength concrete mixed with organic fiber and steel fibers. The fire resistance of high-performance fiber reinforced cement composites is desirable in terms of physical and mechanical properties. However, the use of a polymer as an alternative to organic fiber has not been clearly studied. In this study, a slurry infiltration method was used to obtain slurry-infiltrated fiber-reinforced cementitious composites (SIFRCCs) specimens. Powder polymer was used instead of organic fibers during mixing of the slurry. The compressive and flexural strengths of the specimens after 1 hr of high temperature exposure according to the KS F 2257 (ISO 834) standard fire-temperature curve were measured. The addition of the polymer before and after high temperature (about 945 °C) exposure affected the strength of the SIFRCCs. The compressive and flexural strengths were decreased after exposure to high temperature in comparison with SIFRCCs without polymer because polymer create capillary pores due to melting and burning when exposure to high temperature. This minimizes the vapor pressure inside the concrete model and reduces the failure of the concrete model. The experimental results showed that the flexural strength at a high temperature for 1.0 % polymer content was the highest at 53.8 MPa. The flexural strength was reduced by 40~50% when compared to the flexural strength before high temperature exposure and comparing to SIFRCCs without polymer, the compressive strength in 1.5% polymer is lower, owing to voids that are created in the SIFRCCs after exposure to a high temperature.
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Slavcheva, G. S., and A. T. Bekker. "Temperature and Humidity Dependence on Strength of High Performance Concrete." Solid State Phenomena 265 (September 2017): 524–28. http://dx.doi.org/10.4028/www.scientific.net/ssp.265.524.
Повний текст джерелаАнотація:
The paper presents the results of investigation humidity and temperature influence on concrete of strength grades from B50 to B90. Dry and wet HPC specimens were exposed to different temperatures –60, -40,-20, 0,+20,+40,+60°C. The system parameters of the concrete structure were also examined: volume, surface area and extra finite difference energy of the solid phase, pore size. The results show that the effect of reduction of strength (Rebinder’s effect) of HPC depends on these parameters of the concrete structure. The maximum reduction in strength is fixed for concrete of В80—В90 grades, whose structure is notable for more developed interface between grain and phase boundaries and prevalence of nanopores in its structure.
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Shang, Huai-Shuai, and Ting-Hua Yi. "Behavior of HPC with Fly Ash after Elevated Temperature." Advances in Materials Science and Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/478421.
Повний текст джерелаАнотація:
For use in fire resistance calculations, the relevant thermal properties of high-performance concrete (HPC) with fly ash were determined through an experimental study. These properties included compressive strength, cubic compressive strength, cleavage strength, flexural strength, and the ultrasonic velocity at various temperatures (20, 100, 200, 300, 400 and 500∘C) for high-performance concrete. The effect of temperature on compressive strength, cubic compressive strength, cleavage strength, flexural strength, and the ultrasonic velocity of the high-performance concrete with fly ash was discussed according to the experimental results. The change of surface characteristics with the temperature was observed. It can serve as a reference for the maintenance, design, and the life prediction of high-performance concrete engineering, such as high-rise building, subjected to elevated temperatures.
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Kaprielov, S. S., A. V. Sheynfeld, Al-Omais Dzhalal, A. S. Zaitsev, and R. A. Amirov. "A technology of erecting high-rise building frame structures using B60-B100 classes high-strength concretes." Bulletin of Science and Research Center of Construction 33, no. 2 (July 10, 2022): 106–21. http://dx.doi.org/10.37538/2224-9494-2022-2(33)-106-121.
Повний текст джерелаАнотація:
Introduction. The article presents a technology of erecting of high-rise building's frame structures made of B60-B100 classes high-strength concretes. This technology includes a complex of processes and considers a number of special features, the most significant of which are connected with the specific character of high-strength concretes and concreting climatic conditions.Aim. To determine the main requirements for the technology of concreting and parameters of curing the monolithic structures of high-rise buildings made of B60-B100 classes high-strength concretes, including at winter periods, at the various stages of their erection.Methods and materials. Studies were carried out on the effect of hardening temperature variations from +5 to +50 °С on the hardening kinetics of B60, B80, and B100 classes concretes. Based on the 15-year experience of the “Moscow-City” construction, the mix proportions of high-strength concretes were optimized, as well as the main technological parameters of concreting and curing the frame structures located at an altitude of up to 370 m were analyzed and summarized.Results. The mix proportions of B60-B100 classes concretes of high-workability and self-compacting mixtures with a cement consumption of 350–480 kg/m3 was optimized using standard materials and MB-type organomineral modifiers. The performed study revealed a regularity between the strength and the temperature-temporal parameter of concrete curing, which is applicable for a preliminary assessment of strength characteristics in high-strength concrete structures on the basis of their temperature measurement results. A systematic approach to concrete curing and the maintenance of building structures as a whole with the vertical division of a high-rise building into four temperature zones led to a reducing the probability of thermal cracks appearance.Conclusions. According to the results of the study, the proposed complex of technological solutions concerning compositions and properties of concrete mixtures and concretes, the technology of concreting, as well as the methods of heating and curing the concrete of structures at the various stages of their erection ensures thermal resistance to cracks at the early stage of concrete hardening, as well as the high quality and assigned rates of construction.
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DRZYMAŁA, Tomasz, Wioletta JACKIEWICZ-REK, Jerzy GAŁAJ, and Ritoldas ŠUKYS. "ASSESSMENT OF MECHANICAL PROPERTIES OF HIGH STRENGTH CONCRETE (HSC) AFTER EXPOSURE TO HIGH TEMPERATURE." Journal of Civil Engineering and Management 24, no. 2 (April 25, 2018): 138–44. http://dx.doi.org/10.3846/jcem.2018.457.
Повний текст джерелаАнотація:
There has been a tendency to design ever slender building construction using high strength concrete in recent years. Application of HSC is also growing in tunnel construction. One of the most important challenges is to control explosive spalling of concrete and the method recommended by Eurocode 2 (EN 1992-1-2:2008/NA:2010P) is addition of polypropylene fibres to the mix. The purpose of the research described in this paper was to evaluate the changes of mechanical properties of HSC exposed to the effect of high temperature. The tests were carried out on three types of high strength concrete: air-entrained concrete, polypropylene fibre-reinforced concrete and reference concrete having constant water/cement ratio. The properties of hardened concrete including compressive strength, tensile splitting strength, flexural strength and E-modulus were studied. The latter tests were carried out on both on concrete cured at 20 °C and concrete subjected to high-temperature conditions at 300 °C, 450 °C and 600 °C. The results enabled us to evaluate the effect of high-temperature conditions on the properties of high-performance concrete and compare the effectiveness of the two methods designed to improve the high-temperature performance of the concrete: addition of polypropylene fibres and entrainment of air.
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Sonal Thakkar, Urmil Dave, and Jay Patel. "Experimental investigation of high temperature effect on Slag based alkali activated concrete and ordinary concrete." Electronic Journal of Structural Engineering 20 (June 1, 2020): 22–29. http://dx.doi.org/10.56748/ejse.20242.
Повний текст джерелаАнотація:
Effect of elevated temperature on residual mechanical properties of slag based alkali activated concrete (SAC) was compared with Ordinary Portland cement concrete (OPC) when subjected to temperature up to 900 ° C. SAC was prepared using sodium hydroxide and sodium silicate activators. Residual compres-sive strength, tensile strength, flexural strength, modulus of elasticity and bond strength was studied at differ-ent temperature ranges to evaluate effect of high temperature on both concrete. It was observed that compres-sive strength for OPC decreased from 32 MPa to 19 MPa while in SAC variation was decrease was found to be from 32 MPa to 25 MPa. Similarly in SAC variation in residual split tensile, residual flexural strength, re-sidual Modulus of Elasticity and residual bond test was much less compared to OPC concrete. Physical changes were much noticeable in case of OPC at high temperature compared to SAC. This indicates that SAC performed better at high temperature as compared to that OPC.
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Varona, Francisco B., Francisco Baeza-Brotons, Antonio J. Tenza-Abril, F. Javier Baeza, and Luis Bañón. "Residual Compressive Strength of Recycled Aggregate Concretes after High Temperature Exposure." Materials 13, no. 8 (April 23, 2020): 1981. http://dx.doi.org/10.3390/ma13081981.
Повний текст джерелаАнотація:
Sustainability requirements are gaining importance in the construction industry, which needs to take specific measures in the design and construction of concrete structures. The use of recycled aggregates in concrete may be of special interest. Recycling a construction waste will close the life cycle of the original materials (e.g., concrete). Thus, environmental benefits would come from the lower waste generation, and from a lower necessity of raw materials for new structures. The current Spanish code for structural concrete considers the use of recycled aggregates in replacement rates up to 20% by aggregate mass, assimilating their properties with those of concretes without aggregate replacement. Higher substitution percentages would require further testing. In this work, substitution of coarse aggregate for recycled aggregates (with replacement percentages of 25%, 50% and 100%) has been studied, and the concrete’s residual properties after exposure to high temperatures (between 350 °C and 850 °C) have been assessed. Compressive strength and capillary water absorption tests were made after heating, and the experiments showed higher residual strength in concretes with the greatest content of recycled aggregates. However, a statistical analysis made with additional data available in the literature seemed to predict otherwise, and the recycled aggregate replacement would have a negative effect on the residual strength.
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Patel, Vikas, Brijesh Singh, P. N. Ojha, and B. N. Mohapatra. "Effect on mechanical properties and stress strain characteristics of normal and high strength concrete at elevated temperature." Journal of Building Materials and Structures 7, no. 2 (October 12, 2020): 199–209. http://dx.doi.org/10.34118/jbms.v7i2.767.
Повний текст джерелаАнотація:
High strength concrete (HSC) has some disadvantages such as brittleness and poor resistance to fire. Fire exposure affects the concrete in way that the disintegration of concrete starts and a severe surface spalling occurs at very high temperatures. Therefore, the structural behaviour or response to the load will change after fire exposure and the structural members may not behave as they were designed. Further, the basics of flexural design depend on the stress- strain response of the concrete which is also affected upon fire exposure. Hence, this study is carried out to provide useful input to aid the provision of a fire resistance for structural behaviour of concrete by investigating the effects on mechanical properties of concrete after exposure to high temperatures up to 600°C and establishing a stress-strain relationship. The concrete cylinders of size 100 mm x 200 mm were exposed to the temperature of 2000C, 4000C and 6000C after which the residual compressive strength, split tensile strength and flexural strength were recorded. For stress strain characteristics, 100 × 200 mm cylinders with polypropylene fiber content of 0.5% by volume of concrete were subjected to temperature exposure of 6000C for durations of 1 hour. Curves for reduction factors of strength and stress strain characteristics after fire/elevated temperature exposure has been established. Just consideration of reduced strength for assessment after fire exposure will not serve the purpose as the change in load response and increased deformation capacity also needs to be addressed properly.
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A.M. Mhamoud, Hassan, and Jia Yanmin. "Effect of different additives on high temperatures of concrete." Journal of Structural Fire Engineering 9, no. 2 (June 11, 2018): 161–70. http://dx.doi.org/10.1108/jsfe-01-2017-0021.
Повний текст джерелаАнотація:
Purpose This study aims to investigate the effectiveness of different additives (individual effects) in improving the strength of concrete to resist temperatures of up to 60ºC. Design/methodology/approach In all, 13 different mixtures with a constant water/binder ratio of 0.36 and grade M40 were prepared by using ordinary Portland concrete alone, or with partial replacement by fly ash (FA), blast-furnace slag, silica fume (SF) and a combination of all three. After 7 and 28 days under water, their strength and residual strength were measured. Findings The results of testing revealed that the addition of 10 per cent SF was found to result in the greatest increase in compressive strength and flexural strength along with decreased the residual strengths. The addition of FA increased the compressive strength and enhanced the residual compressive strength. However, it also decreased the residual flexural strength. Originality/value The addition of slag achieved better flexural strength and the best residual compressive strength. The combination of additives also enhanced the compressive strength but was not found to be better than using SF alone.
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Yao, Xinglong, Zhiyang Pei, Haoyuan Zheng, Qizhou Guan, Fupeng Wang, Shuo Wang, and Yongcheng Ji. "Review of Mechanical and Temperature Properties of Fiber Reinforced Recycled Aggregate Concrete." Buildings 12, no. 8 (August 12, 2022): 1224. http://dx.doi.org/10.3390/buildings12081224.
Повний текст джерелаАнотація:
Recycled aggregate concrete has received increasing attention owing to its broad development prospects in recent years. This study discusses the enhancement mechanism of various fibers on the mechanical properties, high-temperature resistance, and freeze–thaw cycle resistance of recycled aggregate concrete. It reviews the effects of fiber types and content on the strength, failure state, and resistance to recycled aggregate concrete’s high and low temperatures. The results indicate that fibers can significantly improve the flexural strength and tensile strength of recycled aggregate concrete in the bridging effect but have little effect on compressive strength. Regarding high-temperature resistance, fibers with a lower melting point can form channels in the concrete, reducing the internal pressure of water vapor. Fibers with higher melting points can act as bridges, inhibiting the generation and propagation of cracks in recycled aggregate concrete. Therefore, fiber-reinforced recycled aggregate concrete can perform better at higher temperatures than ordinary recycled aggregate concrete. Due to the high water absorption rate in recycled aggregate concrete, which is approximately 7–10 times that of natural aggregate concrete, it is easier to reach the critical water saturation of freeze–thaw damage. Results show that 0.2 kg/m3 polypropylene fiber and 1.2 kg/m3 basalt fiber show excellent performance in improving the frost resistance of recycled aggregate concrete.
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Kaleta-Jurowska, Alina, and Krystian Jurowski. "The Influence of Ambient Temperature on High Performance Concrete Properties." Materials 13, no. 20 (October 18, 2020): 4646. http://dx.doi.org/10.3390/ma13204646.
Повний текст джерелаАнотація:
This paper presents the results of tests on high performance concrete (HPC) prepared and cured at various ambient temperatures, ranging from 12 °C to 30 °C (the compressive strength and concrete mix density were also tested at 40 °C). Special attention was paid to maintaining the assumed temperature of the mixture components during its preparation and maintaining the assumed curing temperature. The properties of a fresh concrete mixture (consistency, air content, density) and properties of hardened concrete (density, water absorption, depth of water penetration under pressure, compressive strength, and freeze–thaw durability of hardened concrete) were studied. It has been shown that increased temperature (30 °C) has a significant effect on loss of workability. The studies used the concrete slump test, the flow table test, and the Vebe test. A decrease in the slump and flow diameter and an increase in the Vebe time were observed. It has been shown that an increase in concrete curing temperature causes an increase in early compressive strength. After 3 days of curing, compared with concrete curing at 20 °C, an 18% increase in compressive strength was observed at 40 °C, while concrete curing at 12 °C had a compressive strength which was 11% lower. An increase in temperature lowers the compressive strength after a period longer than 28 days. After two years of curing, concrete curing at 12 °C achieved a compressive strength 13% higher than that of concrete curing at 40 °C. Freeze–thaw performance tests of HPC in the presence of NaCl demonstrated that this concrete showed high freeze–thaw resistance and de-icing materials (surface scaling of this concrete is minimal) regardless of the temperature of the curing process, from 12 °C to 30 °C.
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Yang, Keun-Hyeok, Jae-Sung Mun, and Myung-Sug Cho. "Effect of Curing Temperature Histories on the Compressive Strength Development of High-Strength Concrete." Advances in Materials Science and Engineering 2015 (2015): 1–12. http://dx.doi.org/10.1155/2015/965471.
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This study examined the relative strength-maturity relationship of high-strength concrete (HSC) specifically developed for nuclear facility structures while considering the economic efficiency and durability of the concrete. Two types of mixture proportions with water-to-binder ratios of 0.4 and 0.28 were tested under different temperature histories including (1) isothermal curing conditions of 5°C, 20°C, and 40°C and (2) terraced temperature histories of 20°C for an initial age of individual 1, 3, or 7 days and a constant temperature of 5°C for the subsequent ages. On the basis of the test results, the traditional maturity function of an equivalent age was modified to consider the offset maturity and the insignificance of subsequent curing temperature after an age of 3 days on later strength of concrete. To determine the key parameters in the maturity function, the setting behavior, apparent activation energy, and rate constant of the prepared mixtures were also measured. This study reveals that the compressive strength development of HSC cured at the reference temperature for an early age of 3 days is insignificantly affected by the subsequent curing temperature histories. The proposed maturity approach with the modified equivalent age accurately predicts the strength development of HSC.
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Kumar, Virendra. "Effect of temperature on stress–strain behaviour of pre-damaged confined concrete." Journal of Structural Fire Engineering 11, no. 1 (July 22, 2019): 67–99. http://dx.doi.org/10.1108/jsfe-03-2019-0019.
Повний текст джерелаАнотація:
Purpose This paper aims to study the residual test results under uni-axial compression of tie confined pre-damaged normal strength concrete short columns subjected to elevated temperatures. Design/methodology/approach The test variables included temperature of exposure, spacing of transverse confining reinforcement and pre-damage level. An experimental program was designed and carried out involving testing of hoop confined concrete cylindrical specimens exposed to elevated temperatures ranging from room temperature to 900 °C. Findings The test results indicate that the residual strength, strain corresponding to the peak stress and the post-peak strains of confined concrete are not affected significantly up to an exposure temperature of 300 °C. However, the peak confined stress falls and the corresponding strain increase considerably in the temperature range of 600 to 900 °C. It is shown that an increase in the degree of confinement reinforcement results in an increased residual strength and deformability of pre-damaged confined concrete. Research limitations/implications It is applicable in finding the residual strength and strain of the pre-damaged confined concrete in uni-axial compression after exposure to elevated temperature. Practical implications The practical implications is that the test result is applicable in finding the residual strengths of pre-damaged confined concrete under uni-axial compression after exposure to elevated temperature. Social implications The main aim of the present investigation is to provide experimental data on the residual behaviour of pre-damaged confined concrete subjected to high temperatures. Originality/value The results of this study may be useful for developing the guidelines for designing the confinement reinforcement of reinforced concrete columns against the combined actions of earthquake and fire, as well as for designing the retrofitting schemes after these sequential disasters.
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Ab Kadir, Mariyana Aida, Mohammad Iqbal Khiyon, Abdul Rahman Mohd. Sam, Ahmad Beng Hong Kueh, Nor Hasanah Abdul Shukor Lim, Muhammad Najmi Mohamad Ali Mastor, Nurizaty Zuhan, and Roslli Noor Mohamed. "Performance of spent garnet as a sand replacement in high-strength concrete exposed to high temperature." Journal of Structural Fire Engineering 10, no. 4 (December 9, 2019): 468–81. http://dx.doi.org/10.1108/jsfe-10-2018-0025.
Повний текст джерелаАнотація:
Purpose The purpose of this paper is to examine the mechanical properties, material composition of spent garnet as a sand replacement in high-strength concrete at room and elevated temperatures. Bonding of the concrete containing spent garnet and reinforcing rebar is investigated. Moreover, the optimum thickness of concrete cover subjected to elevated temperatures is investigated. Design/methodology/approach First, the plain spent garnet was physically, chemically and thermally studied. Then, a series of concrete specimens with 0, 20, 40, 60, 80 and 100 per cent of spent garnet were prepared to determine the optimum percentage of spent garnet. Finally, the physical and mechanical behaviours of concrete specimens and effects of cover thickness on steel rebar when subjected to elevated temperature of 200°C, 400°C, 600°C and 800°C for 1 h were studied. It was observed that spent garnet was thermally stable compared to river sand. Findings Mechanical properties were found to be optimal for concrete with 40% spent garnet replacement. Physically, spent garnet concrete changed colour to brown at 400°C, and to whitish grey at 600°C. The residual compressive strength of spent garnet concrete was also found slightly higher than that for control specimens. At various high temperatures, the reduction in ultimate tensile stress for steel bar inside concrete cover of 30 mm was the lowest compared to that of 20 mm. Research limitations/implications Spalling effect it not considered in this study. Practical implications The optimum concrete cover is important issues in reinforced concrete design. This can be used as a guideline by structural designers when using a different type of concrete material in the construction. Social implications Utilization of the waste spent garnet reduces usage of natural aggregates in concrete production and enhances its performance at elevated temperatures. Natural aggregates are normally taken from sand and rock. The new innovation in concrete perhaps can produce light concrete, reduce the cost of concrete production and at the same time also mitigates environmental problems affect from waste material such as minimizing disposal area. Originality/value Utilization of spent garnet in ordinary Portland cement (OPC) concrete at high temperature is a new innovation. It shows that the concrete cover of the concrete element reduced as compared to the OPC concrete. Reduce in weight concrete however the strength of concrete is similar to conventional concrete. This study at elevated temperature has never been performed by any previous researcher.
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Kodur, V. K. R., and M. A. Sultan. "Effect of Temperature on Thermal Properties of High-Strength Concrete." Journal of Materials in Civil Engineering 15, no. 2 (April 2003): 101–7. http://dx.doi.org/10.1061/(asce)0899-1561(2003)15:2(101).
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Gupta, Vivek, and Gokulnath Venkadachalam. "A Review on Effect of Elevate Temperature on Properties of Self-Compacting Concrete Containing Steel Fiber, Glass Fiber and Polypropylene Fiber." International Journal of Research in Engineering, Science and Management 3, no. 10 (October 10, 2020): 9–15. http://dx.doi.org/10.47607/ijresm.2020.326.
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This paper presents an investigation into the efficiency of temperature-sensitive self-compacting concrete. Reviewing on self-compacted concrete, steel fibre, glass fibre, Polypropylene fibre. To this end, adding fibres (steel fibre, glass fibre, Polypropylene) content 1.2% for mixture of concrete material. When the cube samples were 28 days old. They have been heated to high temperatures. Each samples were heated to different temperatures for each concrete mixture (0ºC,100C, 200ºC). Then, Tests for weight loss and compressive strength were performed. The Observations of surface cracks were made after exposure to high temperatures. A significant loss of strength up to 30-40% for all concretes after 300ºC was observed, especially for concrete containing Polypropylene fibre, glass fibre, steel fibre. The fibres reduced the risk of explosive spalling and prevented it. Based on the results of the study, the output of fine aggregate concrete can be inferred.
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Wilson, H. S. "Performance of ilmenite concrete at sustained elevated temperatures." Canadian Journal of Civil Engineering 15, no. 5 (October 1, 1988): 776–83. http://dx.doi.org/10.1139/l88-102.
Повний текст джерелаАнотація:
Two similar mixes were made with cement contents of about 350 kg/m3 and a water–cement ratio of 0.50. The concrete specimens, moist cured for 7 days, were cured in air for 28 and 120 days, respectively, prior to heating. The exposure temperatures were 75, 150, 300, and 450 °C. The periods of exposure at each temperature were 2, 30, and 120 days.The compressive strengths, before heating, of the specimens cured for 35 and 120 days were 41.0 and 46.2 MPa, respectively, and the flexural strengths were 4.9 and 5.8 MPa. Compared with those strengths, the strengths of the specimens heated for 30 days or more increased at 75 °C but decreased at higher temperatures. The losses increased with increase in temperature, reaching about 30% at 450 °C.The flexural strength of the concrete cured in air for 28 days was more adversely affected than was the compressive strength. The flexural and compressive strengths of the concrete cured in air for 120 days were affected to about the same degree. The longer curing period had little effect on the relative losses in compressive strength, but the longer curing period reduced the loss in flexural strength. In most applications, the loss in strength could be compensated by proportioning the mix to overdesign for strength. Key words: high-density concrete, ilmenite, aggregates, high temperature, mechanical properties, nondestructive tests.
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Ho, Chung Ming, and Wei Tsung Tsai. "Effect of Elevated Temperature on the Strength and Ultrasonic Pulse Velocity of Glass Fiber and Nano-Clay Concrete." Advanced Materials Research 163-167 (December 2010): 1532–39. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.1532.
Повний текст джерелаАнотація:
The objectives of this paper are to find the strength and ultrasonic pulse velocity (UPV) of concrete adding admixtures by glass fiber and nano-clay. Residual strength and residual UPV of concrete specimens subjected to elevated temperatures are investigated. Experiment results showed that adding glass fiber and nano-clay would be beneficial for the later-age compressive strength of concrete. Adding nano-clay could considerably increase the flexural and split strength and the toughness of concrete. It is revealed that adding nano-clay could significantly maintain residual compressive and split strength of specimens after high temperature exposure. Regression analysis results revealed that the residual strength and residual UPV of concrete specimens had a high relevance after elevated temperatures exposure.
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SHEYNFELD, Andrey V., Semyon S. KAPRIELOV, and Igor A. CHILIN. "TEMPERATURE EFFECT ON STRUCTURE PARAMETERS AND PROPERTIES OF CEMENT SYSTEMS WITH ORGANO-MINERAL MODIFIERS." Urban construction and architecture 7, no. 1 (March 15, 2017): 58–63. http://dx.doi.org/10.17673/vestnik.2017.01.10.
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The article views changes in strength, phase composition of new growths and diff erential porosity of ultra-high-strength cement systems with organo-mineral modifi er under three temperature modes: under normal conditions at the temperature of 20 °C, after steam treatment at 80 °C and after heat treatment at 200°C. It is shown that the heat treatment at 200 °C signifi cantly modifi es the phase composition and pore structure of cement systems and allows to increase the strength of fi ne grain concrete by 42% and bring it to 188 MPa, what makes possible to refer it to ultra-high-strength concretes, defi ned as «Reactive Powder Concrete».
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Chang, Chuan Peng, Shi Wu Huang, Xue Feng Li, Bo Tian, and Zi Yi Hou. "A Study of the Capability for Fire Resistance of Polypropylene Fibre Concrete." Advanced Materials Research 857 (December 2013): 116–23. http://dx.doi.org/10.4028/www.scientific.net/amr.857.116.
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The purpose of this paper is to examine the effect of various polypropylene fibre additions (length and content) to concrete on compressive strength and explosive spalling when subjected to high temperatures, which simulate the building or tunnel fires. The experimental results show that the compressive strength of polypropylene fiber concrete (PFC) and plain concrete decreases with increasing temperature. Fibre content in a certain range has a small effect on the compressive strength of the concrete, therefore the polypropylene (PP) fibers has a great influence on the anti-spalling behavior of concrete under fire loading to ensure the integrity of the structure. Keywords: concrete, polypropylene fibre, high temperature, compressive strength, spalling
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Yuhanata, Cierio, Dwi Nurtanto, and Nanin Meyfa Utami. "Effect of Temperature Variations on Elevated Temperature Curing Method Towards Modulus of Elasticity and Compressive Strength of Normal Concrete With Additional Accelerator." BERKALA SAINSTEK 10, no. 3 (October 4, 2022): 117. http://dx.doi.org/10.19184/bst.v10i3.29078.
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Developments in modern times have grown rapidly, this can be seen from the rapid development. Along with the increasing scale of development in the world of construction, more and more concrete is needed effectively, practically, and in the future. The strength of concrete is strongly influenced by the quality of the materials, admixtures, the working process, and the curing of the concrete. Concrete with the addition of an accelerator has higher compressive strength, this is due to the accelerator reaction which can accelerate the binding process and the development of the initial compressive strength of the concrete. Concrete with direct immersion treatment has large compressive strength. There are several methods of treating concrete, including watering and high temperature. This study used a fixed accelerator proportion of 3 % of the weight of cement with a test time of 7 and 28 days. The treatment method used is open space, immersion, high temperature at temperatures of 25 ºC, 30 ºC, 35 ºC, 40 ºC and 45 ºC. From the results of the research, there are differences in characteristics between normal concrete and concrete with the addition of an accelerator. Concrete with a high-temperature treatment method at a temperature of 45 ºC produces the highest strong pressure. This is caused by the higher the treatment temperature, the higher the rate of hydration process that affects the compressive strength of the concrete.
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Lee, Taegyu, Keesin Jeong, and Hyeonggil Choi. "Effect of Thermal Properties of Aggregates on the Mechanical Properties of High Strength Concrete under Loading and High Temperature Conditions." Materials 14, no. 20 (October 15, 2021): 6093. http://dx.doi.org/10.3390/ma14206093.
Повний текст джерелаАнотація:
The effect of the thermal properties of aggregates on the mechanical properties of high-strength concrete was evaluated under loading and high-temperature conditions. For the concrete, granite was selected as a natural aggregate, and ash-clay and clay as lightweight aggregates. The mechanical properties of the concrete (stress–strain, compressive strength, elastic modulus, thermal strain, and transient creep) were evaluated experimentally under uniform heating from 20 to 700 °C while maintaining the load at 0, 20, and 40% of the compressive strength at room temperature. Experimental results showed that the concrete containing lightweight aggregates had better mechanical properties, such as compressive strength and elastic modulus, than that of the concrete with a granite aggregate at high temperature. In particular, the concrete containing lightweight aggregates exhibited high compressive strength (60–80% of that at room temperature) even at 700 °C. Moreover, the concrete containing granite exhibited a higher thermal strain than that containing lightweight aggregates. The influence of the binding force under loaded conditions, however, was found to be larger for the latter type. The transient creep caused by the loading was constant regardless of the aggregate type below 500 °C but increased more rapidly when the coefficient of the thermal expansion of the aggregate was above 500 °C.
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Zhang, Feng Chen, De Jian Shen, Ji Kai Zhou, and Zhong Hua Li. "Effect of Thermal Environment at Early Age on Hydration Phases Composition and Strength Development of Concrete Containing Fly Ash." Advanced Materials Research 168-170 (December 2010): 582–88. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.582.
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Cement hydration at early age is sometimes in a certain thermal environment probably caused by hydration heat of mass concrete as well as cement productions curing at high temperature. And phases composition and strength development in thermal environment are commonly different from those in normal curing conditions. Phases composition and strength development of concrete containing different fly ash content curing in different thermal environment are studied in this paper. Experimental results show that compressive strengths of concrete with 0.3 water to binder ratio increase with the increase of curing temperature. Splitting tensile strength of concrete not containing any fly ash curing at about 50 is the highest among those curing at temperature between 40 and 80 . For concrete with different fly ash content, splitting tensile strengths increase approximately with the increse of curing temperature. Dehydration of ettringite and formation of monosulfate solid solution and AFm at higher temperature perhaps relate to the development of concrete splitting tensile strength along with different curing temperature. Adding fly ash to binder, curing temperature at which hydration phases change occurs is raised, which helps to explain that splitting tensile strengths of concrete with different fly ash content decrease little with the increase of curing temperature between 60 and 80 .
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Jonaitis, Bronius, and Vytautas Papinigis. "EFFECT OF LONG‐TERM LOADING AND FIRE TEMPERATURES ON MECHANICAL PROPERTIES OF CONCRETE." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 11, no. 4 (December 31, 2005): 283–88. http://dx.doi.org/10.3846/13923730.2005.9636359.
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During a fire, reinforced concrete structures are exposed to high temperatures and subjected to long‐term action of variable and permanent loads. This paper deals with analysis of influence of fire temperatures and long‐term action of loads on compression strength and deformability of normal weight concrete. Results of experimental investigations of compression strength and deformability of normal‐weight concrete subjected to long‐term load and exposed to high temperature are presented. Specimens in the shape of prisms of normal‐weight concrete were subjected to long‐term compression of intensity η(t) = σc/fc (τ) = 0,3. The long‐term compression was sustained for 400 days. Some of the specimens were heated (at 250 °C and 450 °C) before application of long‐term load; other specimens were heated after application of long‐term load. The paper presents coefficient of service conditions for concrete subjected to long‐term load and exposed to high temperature that gives opportunity to evaluate compression strength and deformation properties of concrete.
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Berestianskaya, Svitlana, Evgeniy Galagurya, Olena Opanasenko, Anastasiia Berestianskaya, and Ihor Bychenok. "Experimental Studies of Fiber-Reinforced Concrete Prisms Exposed to High Temperatures." Key Engineering Materials 864 (September 2020): 3–8. http://dx.doi.org/10.4028/www.scientific.net/kem.864.3.
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Fiber-reinforced concretes are varieties of composite materials. Such materials are commonly used nowadays. Concrete is fiber-reinforced using various fibrous materials, or fibers, which are evenly distributed over the volume of the concrete matrix and simultaneously provide its 3D reinforcement. Fiber-reinforced concrete has better stress-related strength characteristics than ordinary concrete. Since building structures must meet both the strength, rigidity and stability requirements, and the fire safety requirements, then for the extensive use of fiber-reinforced concrete structures, not only the external load design, but also temperature effect design should be conducted in the design phase. The strength and strain characteristics of fiber concrete exposed to high temperatures must be known for this purpose. In view of this, three series of prisms were manufactured and tested: the first series contained no fiber at all (control prisms), the second series contained basalt fiber, and the third series contained steel fiber. The test results showed that adding fibers improves the mechanical characteristics of fiber-reinforced concrete samples under specified conditions.
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Hameed, Ali. "THE EFFECT OF CURING CONDITION ON COMPRESSIVE STRENGTH IN HIGH STRENGTH CONCRETE." Diyala Journal of Engineering Sciences 2, no. 1 (June 1, 2009): 35–48. http://dx.doi.org/10.24237/djes.2009.01103.
Повний текст джерелаАнотація:
The paper shows the effect of curing condition on compressive strength in high strength concrete in three cases (Group A(moist curing in water for 7 days followed by air curing ) ,Group B(curing until the age test in water) and Group C(curing at high temperature 60ºC±2ºC for six days ) and two types of specimen of cubes (150 x150 and 100 x 100) used in the test age (7,28and 90 day) respectively in four mix proportion (Mix No.1(40 Mpa ,Mix No. 2(fcu 60 Mpa) ,Mix No. 3 (fcu 70 Mpa) and Mix No. 4 (fcu 80 Mpa) ). Results demonstrate that, in general, concrete specimens moist cured until testing ages (Group B) give compressive strength greater than specimens moist cured for 7 days in water then followed by air – drying (Group A). The percentage of increase in strength is (5 and12%) for mix No.3 and 6% for mix No.4, as compared with 3% for mix No.1 and (2 and4%) for mix No.2. When the curing temperature (group C ) increases, the compressive strength increases at different ratios ,the percentage of increase in compressive strength at 7,28 and 90 days for mix No.1 , mixes No.2 and 3 are (20,15 and 14% ), ( 7,11 and 5% ) and (13,12 and 5% ) respectively, while mix No4. shows an increase of 4 and 10% in compressive strength at 7 and 28 days where there is a reduction in the strength at 90 days by about 2%. Generally, as the size of specimen decreases, the effect of temperature curing (group C)on the compressive strength increases.
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Jia, Bin, Zheng Liang Li, Lu Cheng, and Hua Chuan Yao. "Experimental Study on Dynamic Mechanical Behaviour of Concrete with High Temperature." Advanced Materials Research 194-196 (February 2011): 1109–13. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.1109.
Повний текст джерелаАнотація:
An experimental system of high-temperature split Hopkinson pressure bar (SHPB) was developed by combination of the split Hopkinson pressure bar (SHPB) and microwave heating system, then tests of concrete whose temperature changed from room temperature to 650°С and impact velocity from 5m/s to 12m/s were completed. Based on the test results, the dynamic strength of concrete increases with increasing impact velocity whether with high temperature or room temperature, meanwhile the dynamic strength of concrete with high temperature has the strain rate effect, but the effect keeps decreasing with temperature increasing, even at temperature above 500°С , compressive strength will not have strain rate sensitive effect any longer when strain rate surpasses a certain value. In the meantime, the strain rate hardening effect is coupled with high temperature weakening effect, but the latter has greater influence.
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Zaidi, Kaleem A., Umesh K. Sharma, N. M. Bhandari, and P. Bhargava. "Postheated Model of Confined High Strength Fibrous Concrete." Advances in Civil Engineering 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/5659817.
Повний текст джерелаАнотація:
HSC normally suffers from low stiffness and poor strain capacity after exposure to high temperature. High strength confined fibrous concrete (HSCFC) is being used in industrial structures and other high rise buildings that may be subjected to high temperature during operation or in case of an accidental fire. The proper understanding of the effect of elevated temperature on the stress-strain relationship of HSCFC is necessary for the assessment of structural safety. Further stress-strain model of HSCFC after exposure to high temperature is scarce in literature. Experimental results are used to generate the complete stress-strain curves of HSCFC after exposure to high temperature in compression. The variation in concrete mixes was achieved by varying the types of fibre, volume fraction of fibres, and temperature of exposure from ambient to 800°C. The degree of confinement was kept constant in all the specimens. A comparative assessment of different models on the high strength confined concrete was also conducted at different temperature for the accuracy of proposed model. The proposed empirical stress-strain equations are suitable for both high strength confined concrete and HSCFC after exposure to high temperature in compression. The predictions were found to be in good agreement and well fit with experimental results.
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Akca, Abdullah Huzeyfe, and Nilüfer Özyurt. "Mechanical Behavior and Recovery of FRC after High Temperature Exposure." Key Engineering Materials 711 (September 2016): 457–64. http://dx.doi.org/10.4028/www.scientific.net/kem.711.457.
Повний текст джерелаАнотація:
During fire, one or two faces of structural members experience higher temperatures than other faces and the deterioration on these faces may continue after fire. High temperature exposure above 400 °C causes deterioration in strength, modulus of elasticity and durability of concrete. Inclusion of fibers and air entraining agents in concrete mixes may reduce the destructive effects of high temperatures on concrete. Therefore, 8 groups of 0.45 w/c ratio of concrete were designed by using polypropylene fibers as low melting point fibers and hooked end steel fibers as high melting point fibers and air entraining admixture as a chemical additive. 15 cm cubic concrete specimens were produced and the five sides of the cubes were insulated with gypsum boards to maintain one face heating. An electrical furnace was used to heat concrete to 1000 °C and K-type thermocouples were placed in specimens to monitor temperature distribution in concrete. Moreover, two different re-curing methods, air and water, were applied after heating to see the change in mechanical properties and crack occurrences on the heated surface of concrete specimens. SEM and XRD investigations were conducted on the samples taken from the heated surfaces and the inner parts of the concrete in order to understand the morphological changes due to heating and re-curing. Results showed that deterioration on the surfaces due to high temperature exposure continued during air re-curing process and compressive strength and modulus of elasticity values of these specimens also diminished. On the other hand, compressive strength of water re-cured concrete stayed constant after heating and partial recovery of modulus of elasticity were obtained and the positive effect of water re-curing were observed on polypropylene fiber reinforced concrete prominently.
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Al-Ameri, Raad A., Sallal R. Abid, G. Murali, Sajjad H. Ali, and Mustafa Özakça. "Residual Repeated Impact Strength of Concrete Exposed to Elevated Temperatures." Crystals 11, no. 8 (August 12, 2021): 941. http://dx.doi.org/10.3390/cryst11080941.
Повний текст джерелаАнотація:
Portland cement concrete is known to have good fire resistance; however, its strength would be degraded after exposure to the temperatures of fire. Repeated low-velocity impacts are a type of probable accidental load in many types of structures. Although there is a rich body of literature on the residual mechanical properties of concrete after high temperature exposure, the residual repeated impact performance of concrete has still not been well explored. For this purpose, an experimental study was conducted in this work to evaluate the effect of high temperatures on the repeated impact strength of normal strength concrete. Seven identical concrete patches with six disc specimens each were cast and tested using the ACI 544-2R repeated impact setup at ambient temperature and after exposure to 100, 200, 300, 400, 500 and 500 °C. Similarly, six cubes and six prisms from each patch were used to evaluate the residual compressive and flexural strengths at the same conditions. Additionally, the scattering of the impact strength results was examined using three methods of the Weibull distribution, and the results are presented in terms of reliability. The test results show that the cracking and failure impact numbers of specimens heated to 100 °C reduced slightly by only 2.4 and 3.5%, respectively, while heating to higher temperatures deteriorated the impact resistance much faster than the compressive and flexural strengths. The percentage reduction in impact resistance at 600 °C was generally higher than 96%. It was also found that the deduction trend of the impact strength with temperature is more related to that of the flexural strength than the compressive strength. The test results also show that, within the limits of the adopted concrete type and conducted tests, the strength reduction after high temperature exposure is related to the percentage weight loss.
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Lin, Xi, Xi Xian Ji, Xin Bo Yin, and Heng Chun Zhang. "Research on the Effect of Superfine Powder Micro Bead on the Properties of High-Strength Concrete." Advanced Materials Research 785-786 (September 2013): 235–38. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.235.
Повний текст джерелаАнотація:
A sub-micron spherical powder material-micro bead, which has good water reduction, filling and enhancement effect, could be used as active mineral admixture in high-strength concrete. The affection of micro bead on the hydration temperature rise, mechanical properties, and shrinkage properties of high-strength concrete were studied, and the results showed that: micro bead could reduce the highest temperature peak of concrete, and at the low water-cement ratio, its small dosage could develop the compressive strength of concrete, and after instead of silica fume with suitable dosage, it could reduce the shrinkage of high-strength concrete.