Journal articles on the topic 'Fiber-reinforced concrete Effect of temperature on Testing'
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1
Mukhtar, Faisal M., and Olaniyi Arowojolu. "Recent developments in experimental and computational studies of hygrothermal effects on the bond between FRP and concrete." Journal of Reinforced Plastics and Composites 39, no. 11-12 (March 22, 2020): 422–42. http://dx.doi.org/10.1177/0731684420912332.
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The performance of fiber reinforced polymer externally bonded to concrete is greatly influenced by the environmental conditions to which it is exposed during service. Temperature and humidity are the two common environmental factors that alter the bond behavior of externally bonded fiber reinforced polymer. This paper reviews the experimental and computational approaches used to evaluate the hygrothermal effects—that is, the effect of temperature and humidity—on the durability of the fiber reinforced polymer–concrete bond, as well as on the bond’s performance under loading conditions. Some experimental testing conducted in the laboratory and in situ are critically reviewed and presented. Implemented approaches for improving bond performance under hygrothermal conditions and their modeling techniques are also presented. The paper concludes by discussing the review’s salient issues. The ongoing wide application of externally bonded fiber reinforced polymer creates opportunities for new research on improving and predicting the bond strength of fiber reinforced polymer concrete under hygrothermal conditions.
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Xiao, Kai Tao, Jia Zheng Li, and Hua Quan Yang. "Study of Crack Resistance Property of Polyvinyl Alcohol Fiber Reinforced Concrete." Advanced Materials Research 287-290 (July 2011): 178–82. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.178.
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The strength, ultimate tensile value, compressive elastic modulus and drying shrinkage of polyvinyl alcohol fiber reinforced concrete were studied by tests, and its crack resistance property was also studied by plate method and temperature stress testing machine. The test results showed that PVA fiber could improve the tensile strength and ultimate tensile value of concrete, lower its compressive elastic modulus and drying shrinkage, restrain its early plastic shrinkage and drying shrinkage cracks, reduce its cracking temperature and improve the crack resistance property of concrete, moreover, the effect of long PVA fiber was better.
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Song, Xian Hui, Li Xia Zheng, and Zhuo Qiu Li. "Temperature Compensation in Deformation Testing for Smart Concrete Structures." Key Engineering Materials 326-328 (December 2006): 1503–6. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1503.
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Carbon fiber reinforced concrete (CFRC) structures exhibit both strain sensibility and temperature sensibility, which are coupled with each other when used in traffic or health monitoring for concrete structures. This coupling property results in inaccurateness of measured deformation. In this paper Four-probe Difference Method is used to detach the above two effects according to loaded conditions of structures and different characteristics of the two effects. The theoretical and experimental results indicate that the method is feasible and effective.
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Elbadry, Mamdouh M., Hany Abdalla, and Amin Ghali. "Effects of temperature on the behaviour of fiber reinforced polymer reinforced concrete members: experimental studies." Canadian Journal of Civil Engineering 27, no. 5 (October 1, 2000): 993–1004. http://dx.doi.org/10.1139/l00-013.
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Thermal characteristics of fiber reinforced polymer (FRP) reinforcement can be substantially different from those of concrete and conventional steel reinforcement. The influence of this difference on the behaviour of FRP reinforced concrete members is studied in this paper. Concrete beams reinforced with different types of FRP rebars are tested under the effects of temperature gradient while the rotation at the two ends of the beam are restrained. The bending moments and cracking developed by the thermal gradient are monitored. The results are compared with those obtained from tests on beams of the same dimensions but reinforced with steel bars. The behaviour of thermally cracked members is also investigated under mechanical load effects at both service and ultimate load levels. The potential cracking of the concrete cover caused by the transverse thermal expansion of FRP bars is examined by testing concrete cylinders. The experiments show the difference in thermal behaviour of glass and carbon FRP and steel bars.Key words: bond, concrete, cracking (fracturing), fiber reinforced polymers, loads (forces), reinforcement, temperature, tensile strength, thermal expansion, thermal stresses.
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Niu, Xu Jing, Qing Xin Zhao, and Ying Nie. "Effect of Polypropylene Macro-Fiber on Properties of High-Strength Concrete at Elevated Temperatures." Key Engineering Materials 629-630 (October 2014): 284–90. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.284.
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After being subjected to different elevated temperatures, ranging between 200 °C and 800 °C, the flexural strength, matrix mass loss rate and water absorption of polypropylene (PP) macro-fiber reinforced high strength concrete (HSC) were investigated. Moreover, the internal damage of concrete was analyzed by the ultrasonic non-destructive testing technology. The results indicate that PP macro-fiber in HSC has an adverse effect on flexural strength, while the synergistic effect of hybrid fibers (PP micro-fiber plus PP macro-fiber) can minimize this effect. Compared with PP micro-fiber, PP macro-fiber is more effective in increasing the matrix mass loss rate and water absorption of HSC. However, if the dosage of PP macro-fiber is too high, the pressure relief channels formed by fibers melt will be too coarse, and the total porosity of HSC will be increased significantly. Finally, a mathematical model relating the damage degree to temperature was established based on the non-linear fitting of the experimental data.
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Halstead, J. Preston, Jerome S. O’Connor, Khuong Luu, Sreenivas Alampalli, and Amy Minser. "Fiber-Reinforced Polymer Wrapping of Deteriorated Concrete Columns." Transportation Research Record: Journal of the Transportation Research Board 1696, no. 1 (January 2000): 124–30. http://dx.doi.org/10.3141/1696-53.
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The New York State Department of Transportation initiated a fiber-reinforced polymer (FRP) Column Wrap Demonstration Project in March 1998. The purpose of this project is to investigate the effectiveness and efficiency of preserving deteriorated concrete with FRP, its possible detrimental effects, and its viability as an alternative for concrete column repair and rehabilitation without regard to seismic considerations. To the authors’ knowledge, this is the first FRP column wrap demonstration project of its kind to involve most of the FRP wrap suppliers in the United States. A 5-year condition-monitoring program was established to monitor the performance of FRP wrapping in preserving the concrete columns. A baseline condition of the piers was established through testing, including concrete cores for compressive strength, chlorides, pH, and freeze-thaw resistance; hammer soundings; and a tight-grid survey of electric potentials. Concrete spalls were repaired; however, delaminations were not. To monitor corrosion of the column reinforcing steel, corrosion probes using linear polarization technology were embedded in the concrete. Initial corrosion readings were collected before wrapping, enhancing the observed baseline condition data. In addition, concrete humidity and temperature probes were installed through the FRP wraps, and strain gauges were mounted on the FRP wraps. Data will be collected at 3-month intervals for 4 or 5 years. The wraps will be removed after monitoring, and a complete column testing program will be implemented at that time.
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Huang, Li, Zhuo Qiu Li, and Xian Hui Song. "A Nondestructive Testing Method for Crack in Carbon Fiber Reinforced Concrete with Infrared Thermography." Key Engineering Materials 297-300 (November 2005): 2128–33. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.2128.
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Based on the functional characteristics of carbon fiber reinforced concrete (CFRC), an improved infrared nondestructive testing method, to detect crack in CFRC by using infrared thermography, is presented in this paper. The principle is that when a CFRC specimen is applied a low voltage, crack existing in the specimen will result in non-homogeneous surface temperature distribution due to the electro-thermal effect of the material. Monitoring the temperature difference on the surface, the crack under the observed surface can be inspected by using infrared thermography. In theory, the mechanism causing the temperature difference comes down to an unsteady heat transfer problem with internal energy sources. In the case of the thermo-physical property of CFRC as given, the sensitivity of this method to the depth of the crack is analyzed by numerical computation.
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Ogrodowska, Karolina, Karolina Łuszcz, and Andrzej Garbacz. "The effect of temperature on the mechanical properties of hybrid FRP bars applicable for the reinforcing of concrete structures." MATEC Web of Conferences 322 (2020): 01029. http://dx.doi.org/10.1051/matecconf/202032201029.
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One of the most common causes of the deterioration of concrete structures is the corrosion of steel reinforcement. Reinforcement made from fiber reinforced polymers (FRP) is considered to be an attractive substitution for traditional reinforcement. The most popular FRP reinforcing bars are made of glass fibers. Basalt fiber reinforced polymer (BFRP) is a relatively new material for reinforcing bars. The main drawback of BFRP bars is their low modulus of elasticity. A new type of bar made from hybrid fiber reinforced polymer (HFRP) in which a proportion of the basalt fibers are replaced with carbon fibers can be considered as a solution to this issue; such a bar is presented in this work. The HFRP bars might be treated as a relatively simple modification to previously produced BFRP bars. A different technical characteristic of the fibre reinforced polymer makes the designing of structures with FRP reinforcement differ from conventional reinforced concrete design. Therefore, it is necessary to identify the differences and limitations of their use in concrete structures, taking into account their material and geometric features. Despite the predominance of FRP composites in such aspects as corrosion resistance, high tensile strength, and significant weight reductions of structures – it is necessary to consider the behavior of FRP composites at elevated temperatures. In this paper, the effect of temperature on the mechanical properties of FRP bars was investigated. Three types of FRP bar were tested: BFRP, HFRP in which 25% of basalt fibers were replaced with carbon fibers and nHFRP in which epoxy resin was additionally modified with a nanosilica admixture. The mechanical properties were determined using ASTM standard testing for transverse shear strength. The tests were performed at -20°C, +20°C, +80°C for three diameters of each types of bar.
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Protchenko, Kostiantyn, and Elżbieta Szmigiera. "Post-Fire Characteristics of Concrete Beams Reinforced with Hybrid FRP Bars." Materials 13, no. 5 (March 10, 2020): 1248. http://dx.doi.org/10.3390/ma13051248.
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One of the main concerns of experimental and numerical investigations regarding the behavior of fiber-reinforced polymer reinforced concrete (FRP-RC) members is their fire resistance to elevated temperatures and structural performance at and after fire exposure. However, the data currently available on the behavior of fiber-reinforced polymer (FRP) reinforced members related to elevated temperatures are scarce, specifically relating to the strength capacity of beams after being subjected to elevated temperatures. This paper investigates the residual strength capacity of beams strengthened internally with various (FRP) reinforcement types after being subjected to high temperatures, reflecting the conditions of a fire. The testing was made for concrete beams reinforced with three different types of FRP bars: (i) basalt-FRP (BFRP), (ii) hybrid FRP with carbon and basalt fibers (HFRP) and (iii) nano-hybrid FRP (nHFRP), with modification of the epoxy matrix of the rebar. Tested beams were first loaded at 50% of their ultimate strength capacity, then unloaded before being heated in a furnace and allowed to cool, and finally reloaded flexurally until failure. The results show an atypical behavior observed for HFRP bars and nHFRP bars reinforced beams, where after a certain temperature threshold the deflection began to decrease. The authors suggest that this phenomenon is connected with the thermal expansion coefficient of the carbon fibers present in HFRP and nHFRP bars and therefore creep can appear in those fibers, which causes an effect of “prestressing” of the beams.
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Protchenko, Kostiantyn. "Residual Fire Resistance Testing of Basalt- and Hybrid-FRP Reinforced Concrete Beams." Materials 15, no. 4 (February 17, 2022): 1509. http://dx.doi.org/10.3390/ma15041509.
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The fire resistance of fiber-reinforced polymer reinforced concrete (FRP-RC) elements depends on the temperature performance of the original concrete member, the fire scenario, and FRP reinforcement behavior. In this study, fire resistance tests are described, along with the characteristics obtained during and after applying elevated temperatures, simulating the effects of fire. The tested beams were reinforced with basalt (BFRP) bars and with a hybrid composite of carbon fibers and basalt fibers (HFRP) bars. Fire tests were performed on full-scale beams, in which the midsections of the beams were heated from below (tension zone) and from the sides for two hours, after which the beams were cooled and subjected to flexural testing. BFRP-RC beams failed before the heating time was completed; the best failure was associated with a BFRP reinforced beam that failed approximately 108 min after heating. Contrary to the BFRP-RC samples, HFRP-RC beams were capable of resisting exposure to elevated temperatures for two hours, but showed a 70% reduction in strength capacity when compared to non-heated reference beams. According to the author, the higher resistance of HFRP-RC beams was the result of the thermal expansion coefficient of carbon fibers employed in HFRP, which “prestresses” the beams and enables smaller deflections. The preliminary findings of this study can increase the feasibility of using FRP materials for engineering purposes.
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Xin, Jianda, Siqing Lin, Nannan Shi, Jianshu Ouyang, and Dahai Huang. "Effect of Reinforcement on Early-Age Concrete Temperature Stress: Preliminary Experimental Investigation and Analytical Simulation." Advances in Materials Science and Engineering 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/231973.
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For concrete under short-term loading, effect of reinforcement on concrete crack resistance capability is usually negligible; however, recent research results show that extension of this viewpoint to concrete under long-term loading (temperature variation) may be unsuitable. In order to investigate this phenomenon, this paper presents the experimental and analytical results of early-age reinforced concrete temperature stress development under uniaxial restraint. The experiments were carried out on a temperature stress testing machine (TSTM). Experimental results show that the coupling of reinforcement and concrete creep behavior influenced the concrete temperature stress development, and nearly 16% of concrete stress was reduced in the current research. Moreover, the cracking time of reinforced concrete was also delayed. Finally, based on the principle of superposition, analytical simulations of effect of reinforcement on concrete temperature stress have been performed.
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Manoj Kumar Rath. "Condition Assessment of a Reinforced Concrete Residential Building using Non-destructive Testing Methods - A Case Study." Electronic Journal of Structural Engineering 21 (November 30, 2021): 18–33. http://dx.doi.org/10.56748/ejse.21288.
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The present study deals with both experimental and numerical investigation on buckling effects of laminated composite plates subjected to varying temperature and moisture. A simple laminated plate model is developed for the buckling of composite plates subjected to adverse hygrothermal loading. A computer program based on FEM in MATLAB environment is developed to perform all necessary computations. The woven fiber Glass/Epoxy specimens were hygrothermally conditioned in a humidity cabinet where theconditions were maintained at temperatures of 300K-425K and relative humidity (RH) ranging from 0-1% for moisture concentrations. All the investigations are made with a symmetric cross-ply laminates. The present study deals with both experimental and numerical investigation on buckling behavior of laminated composite plates subjected to varying temperature and moisture concentration. Quantitative results are presented to show the effects of geometry, material and lamination parameters of woven fiber laminate onbuckling of composite plates for different temperature and moisture concentrations with simply supported boundary conditions with different aspect and side-to-thickness ratios. Experimental results show that there is reduction in buckling loads in KN with the increase in temperature and moisture concentration for laminates with clamped-free-clamped-free boundary conditions
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Caballero-Jorna, Marta, Marta Roig-Flores, and Pedro Serna. "A Study of the Flexural Behavior of Fiber-Reinforced Concretes Exposed to Moderate Temperatures." Materials 14, no. 13 (June 24, 2021): 3522. http://dx.doi.org/10.3390/ma14133522.
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The use of synthetic fibers in fiber-reinforced concretes (FRCs) is often avoided due to the mistrust of lower performance at changing temperatures. This work examines the effect of moderate temperatures on the flexural strengths of FRCs. Two types of polypropylene fibers were tested, and one steel fiber was employed as a reference. Three-point bending tests were carried out following an adapted methodology based on the standard EN 14651. This adapted procedure included an insulation system that allowed the assessment of FRC flexural behavior after being exposed for two months at temperatures of 5, 20, 35 and 50 °C. In addition, the interaction of temperature with a pre-cracked state was also analyzed. To do this, several specimens were pre-cracked to 0.5 mm after 28 days and conditioned in their respective temperature until testing. The findings suggest that this range of moderate temperatures did not degrade the behavior of FRCs to a great extent since the analysis of variances showed that temperature is not always a significant factor; however, it did have an influence on the pre-cracked specimens at 35 and 50 °C.
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Tang, Wei Le, Han-Seung Lee, Vanissorn Vimonsatit, Trevor Htut, Jitendra Kumar Singh, Wan Nur Firdaus Wan Hassan, Mohamed A. Ismail, Asiful H. Seikh, and Nabeel Alharthi. "Optimization of Micro and Nano Palm Oil Fuel Ash to Determine the Carbonation Resistance of the Concrete in Accelerated Condition." Materials 12, no. 1 (January 3, 2019): 130. http://dx.doi.org/10.3390/ma12010130.
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The carbonation rate of reinforced concrete is influenced by three parameters, namely temperature, relative humidity, and concentration of carbon dioxide (CO2) in the surroundings. As knowledge of the service lifespan of reinforced concrete is crucial in terms of corrosion, the carbonation process is important to study, and high-performance durable reinforced concretes can be produced to prolong the effects of corrosion. To examine carbonation resistance, accelerated carbonation testing was conducted in accordance with the standards of BS 1881-210:2013. In this study, 10–30% of micro palm oil fuel ash (mPOFA) and 0.5–1.5% of nano-POFA (nPOFA) were incorporated into concrete mixtures to determine the optimum amount for achieving the highest carbonation resistance after 28 days water curing and accelerated CO2 conditions up to 70 days of exposure. The effect of carbonation on concrete specimens with the inclusion of mPOFA and nPOFA was investigated. The carbonation depth was identified by phenolphthalein solution. The highest carbonation resistance of concrete was found after the inclusion of 10% mPOFA and 0.5% nPOFA, while the lowest carbonation resistance was found after the inclusion of 30% mPOFA and 1.5% nPOFA.
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Rashid, Muhammad Harunur, Md Maruf Molla, and Imam Muhammad Taki. "Effect of Elevated Temperature on Bond Strength of Concrete." Materials Science Forum 972 (October 2019): 26–33. http://dx.doi.org/10.4028/www.scientific.net/msf.972.26.
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In the case of exposure of reinforced concrete structure to accidental fire, an assessment of its residual capacity is needed. Bond strength of concrete was observed under elevated temperatures (150°, 250°, 350° and 500°C) in this study. Cylindrical specimens were prepared for pull-out tests to find out the bond behavior and to observe the mechanical properties of concrete. All the specimens were 100 mm diameter and 200 mm height. The pull-out specimens contain a 10 mm steel bar at its center. The specimens were tested at 52 days age following a 28 days water curing. Samples were preheated for 3 hours at 100°C temperature and then put into the furnace for 1 hour at the target temperature. Samples were tested before preheating as controlled specimens. In case of mechanical properties and the bond strength of concrete, there were no remarkable changes due to elevated temperature up to 150°C. However, the mechanical properties and bond strength were decreased gradually after 150°C temperature. Maximum reduction of bond strength observed was 52.13% and 49.8% at 500°C for testing within 1 hour and after 24 hours of heating respectively when compared to the controlled specimens. Bond strength was found to reduce at a greater rate than compressive strength due to the elevated temperature.
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Won, Moon. "Improvements of Testing Procedures for Concrete Coefficient of Thermal Expansion." Transportation Research Record: Journal of the Transportation Research Board 1919, no. 1 (January 2005): 23–28. http://dx.doi.org/10.1177/0361198105191900103.
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The coefficient of thermal expansion (CTE) of concrete has a significant effect on the performance of portland cement concrete pavement. Concrete with a higher CTE is more prone to cracking, additional warping, and spalling. To improve PCC pavement performance, several districts of the Texas Department of Transportation (TxDOT) currently limit the CTE of concrete. To support this policy, efforts have been made to improve the accuracy and repeatability of the testing procedures for CTE. The current AASHTO Test Method TP 60 has been evaluated, its shortcomings identified, and improvements made. The improvements include CTE determination from regression analysis of temperature and displacement measurements. The effects of a number of variables on concrete CTE were investigated. The effect of the rate of heating and cooling is negligible. Concrete age and specimen size also have a negligible effect. Coarse aggregate content in the concrete mix has an effect on the test results. This test procedure was used to evaluate coarse aggregates from 32 sources in Texas. The results show that coarse aggregate type has a significant effect on concrete CTE. The proposed testing procedure for concrete CTE provided more accurate results than the AASHTO TP 60. TxDOT plans to implement this test procedure and to develop appropriate steel design standards for continuously reinforced concrete pavement and other construction-related requirements such as different curing methods for concrete with varying CTEs. This implementation should result in better concrete pavement performance.
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Shi, Nannan, Jianshu Ouyang, Runxiao Zhang, and Dahai Huang. "Experimental Study on Early-Age Crack of Mass Concrete under the Controlled Temperature History." Advances in Materials Science and Engineering 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/671795.
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Thermal deformation under restrained conditions often leads to early-age cracking and durability problems in mass concrete structures. It is crucial to monitor accurately the evolution of temperature and thermal stresses. In this paper, experimental studies using temperature stress testing machine (TSTM) are carried out to monitor the generated thermal cracking in mass concrete. Firstly, components and working principle of TSTM were introduced. Cracking temperatures and stress reserves are selected as the main cracking evaluation indicators of TSTM. Furthermore, effects of temperature controlling measures on concrete cracking were quantitatively studied, which consider the concrete placing temperature (before cooling) and cooling rates (after cooling). Moreover, the influence of reinforcement on early-age cracking has been quantitatively analyzed using the TSTM. The experimental results indicate that the crack probability of reinforced concrete (RC) is overestimated. Theoretical calculations proved that the internal stress can transfer from concrete to reinforcement due to creep effect. Finally, the experimental results indicate that the reinforcement can improve the crack resistance of concrete by nearly 30% in the TSTM tests, and the ultimate tensile strain of RC is approximately 105% higher than that of plain concrete with the same mix proportions.
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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.
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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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Ali Salih, Yaseen, Mohammed Faeq Yass, Ahmed Shihab Ahmed, and Aziz I. Abdulla. "Effect of Adding Porcelain and Glass Powder Mixture on Epoxy Properties." International Journal of Engineering & Technology 7, no. 4.37 (December 13, 2018): 39. http://dx.doi.org/10.14419/ijet.v7i4.37.23612.
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In this research, porcelain powder and glass was added by 0.25% (0.15% porcelain powder and 0.1% glass powder) to the epoxy used in the concrete strengthening. The addition improved epoxy properties and reduced the cost. The results showed that the addition of porcelain and glass powder decrease the interaction temperature by 11.37%, epoxy flow by 10.41%, and increase the compressive strength by 7.61%. Upon testing the improved epoxy cubes under the effect of temperatures up to 200ᵒ C compression resistance decreased by 6.36%, while both modulus of rupture and modulus of elasticity improved by (1.03% and 4.11%) respectively. The epoxy was tested and used to strengthen reinforced concrete beams and tests showed good improvement in flexural properties.
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Wang, Zhenpeng, Minshui Huang, and Jianfeng Gu. "Temperature Effects on Vibration-Based Damage Detection of a Reinforced Concrete Slab." Applied Sciences 10, no. 8 (April 21, 2020): 2869. http://dx.doi.org/10.3390/app10082869.
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To study the variations in modal properties of a reinforced concrete (RC) slab (such as natural frequencies, mode shapes and damping ratios) under the influence of ambient temperature, a laboratory RC slab is monitored for over a year, the simple linear regression (LR) and autoregressive with exogenous input (ARX) models between temperature and frequencies are established and validated, and a damage identification based on particle swarm optimization (PSO) is utilized to detect the assumed damage considering temperature effects. Firstly, the vibration testing is performed for one year and the variations of natural frequencies, mode shapes and damping ratios under different ambient temperatures are analyzed. The obtained results show that the change of ambient temperature causes a major change of natural frequencies, which, on the contrary, has little effect on damping ratios and modal shapes. Secondly, based on a theoretical derivation analysis of natural frequency, the models are determined from experimental data on the healthy structure, and the functional relationship between temperature and elastic modulus is obtained. Based on the monitoring data, the LR model and ARX model between structural elastic modulus and ambient temperature are acquired, which can be used as the baseline of future damage identification. Finally, the established ARX model is validated based on a PSO algorithm and new data from the assumed 5% uniform damage and 10% uniform damage are compared with the models. If the eigenfrequency exceeds the certain confidence interval of the ARX model, there is probably another cause that drives the eigenfrequency variations, such as structural damage. Based on the constructed ARX model, the assumed damage is identified accurately.
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Choi, Pangil, Dong-Ho Kim, Bong-Hak Lee, and Moon C. Won. "Evaluation of structural responses of continuously reinforced concrete pavement (CRCP) using falling weight deflectometer." Canadian Journal of Civil Engineering 43, no. 1 (January 2016): 28–39. http://dx.doi.org/10.1139/cjce-2015-0263.
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The objective of this study is to suggest reasonable structural evaluation method of continuously reinforced concrete pavement (CRCP) using falling weight deflectometer (FWD). The effects of transverse crack spacing and temperature conditions were investigated in CRCP sections with various slab thicknesses and pavement ages. A total of 20 CRCP sections were selected throughout Texas and structural responses were evaluated from 2006 to 2013 for 8 testing years. Test results show that transverse crack spacing has little effect on deflection and load transfer efficiency (LTE). The LTE values were maintained at above 90%, regardless of crack spacing, temperature condition or pavement age. Temperature variations had small effects on deflections at cracks and the mid-slab, but almost no effects on LTE. Maximum deflections and back-calculated k-values appear to be better indicators of structural condition of CRCP than LTE. Load transfer efficiency is not the best indicator of structural condition of transverse cracks in CRCP. Deficiencies in slab support are the primary cause of full-depth distresses in Texas, and back-calculated k-values, which combine both a maximum deflection and the shape of deflection bowl from FWD testing, may be a better indicator of the structural condition of CRCP.
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Benmokrane, Brahim, Ehab El-Salakawy, Amr El-Ragaby, and Sherif El-Gamal. "Performance evaluation of innovative concrete bridge deck slabs reinforced with fibre-reinforced-polymer bars." Canadian Journal of Civil Engineering 34, no. 3 (March 1, 2007): 298–310. http://dx.doi.org/10.1139/l06-173.
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This paper presents the construction details, field testing, and analytical results of six innovative concrete bridges reinforced with fibre-reinforced-polymer (FRP) bars recently constructed in North America, namely Wotton, Magog, Cookshire-Eaton, Val-Alain, and Melbourne bridges in Quebec, Canada, and Morristown bridge in Vermont, USA. All six bridges are girder type, with main girders made of either steel or prestressed concrete. The main girders are supported over spans ranging from 26.2 to 50.0 m. The deck is a 200–230 mm thick concrete slab continuous over spans of 2.30–3.15 m. Different types of glass- and carbon-FRP reinforcing bars and conventional steel were used as reinforcement for the concrete deck slab. The six bridges are located on different highway categories, which means different traffic volume and environmental conditions. The bridges are well instrumented at critical locations for internal temperature and strain data collection using fibre optic sensors. These sensors are used to monitor the deck behaviour from the time of construction to several years after the completion of construction. The bridges were tested for service performance using calibrated truckloads. In parallel, a finite element analysis (FEA) was conducted and verified against the results of the field load tests. The FEA was then used to run parametric studies to investigate the effect of several important parameters such as FRP reinforcement type and ratio on the service and ultimate behaviour of these bridge decks. The analytical and field results under real service conditions, in terms of deflections, cracking, and strains in reinforcement and concrete, were comparable to those of concrete bridge deck slabs reinforced with steel.Key words: bridges deck slabs, fibre-reinforced-polymer (FRP) bars, field testing, finite element analysis.
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Abbas, Anwar Saad, and Mohammed Mansour Kadhum. "Impact of Fire on Mechanical Properties of Slurry Infiltrated Fiber Concrete (SIFCON)." Civil Engineering Journal 6 (September 30, 2020): 12–23. http://dx.doi.org/10.28991/cej-2020-sp(emce)-02.
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This research aims to shed light on the fire flame effect on some mechanical properties of SIFCON samples, such as compressive strength, flexural strength and modulus of elasticity and comparing the results with CEN design curve and CEB. Higher temperature resistance is one of the most important parameters affecting the durability and service life of the material. This study comprised of casting and testing SIFCON specimens with 6% fiber volume before and after exposure to elevated temperatures. Two fire exposure duration of 1 and2 hours were investigate. In addition to room temperature, Silica fume was used as a partial replacement (10%) by weight of cement. It was found from the results achieved that after exposure to high temperatures, compressive strength, flexural strength and elastic modulus decreased. The drastically reduction of compressive strength took place with increasing temperature. The residual compressive strength, flexural strength and elastic modulus at 1010 °C were in the range of (58.4 to 80.1%), (81.6 to 78.7%) and (30.4 to 32.8%) respectively. The compressive strength test results of this study together with results obtained by other investigators were compared with CEB strength-reduction curve and that of CEN. It was noticed that the test results agreed with CEN design curve rather than with that of CEB.
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Barabash, I. V., A. I. Vorokhaiev, and L. M. Ksonshkevуch. "HYDROPHOBIZATION OF BASALT FIBER AND ITS INFLUENCE ON THE MECHANICAL CHARACTERISTICS OF SAND CONCRETE." Bulletin of Odessa State Academy of Civil Engineering and Architecture, no. 81 (December 7, 2020): 114–20. http://dx.doi.org/10.31650/2415-377x-2020-81-114-120.
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Abstract. The materials of the proposed article are devoted to the study of mechanical properties of sand concrete with the addition of hydrophobized basalt fiber and polycarboxylate superplasticizer Relaxol-Super PC. Adding hydrophobic properties to the basalt fiber causes a decrease of water consumption of fine-grained concrete mixture, which leads to improved mechanical properties of concrete. The aim of the work was to increase the mechanical characteristics of sand concrete by introducing hydrophobized basalt fiber into its composition. The objective of the research is to study the effect of hydrophobized basalt fiber on the mechanical characteristics of sand concrete. The polycarboxylate superplasticizer Relaxol-Super PC (Budindustriya, Zaporozhye) was used to increase the mobility of the concrete mixture. Basalt fiber Bauson-basalt 12 mm long and 18 ± 2μm in diameter was used as a fibrous filler. Sand concrete mixture was prepared in a laboratory forced-action mixer. Dosing of Portland cement, quartz sand and basalt fiber was carried out by weight, water and water-reducing additive ‒ by volume, taking into account the density of the additive. The fiber was introduced into a dry cement-sand mixture. After mixing for 120 ... 150 seconds, water with a dosed amount of additive was introduced into the mixture. The hardening of samples concrete took place under normal conditions in a chamber with a temperature of 20 ± 20C and a relative humidity of at least 95%. The compressive strength of concrete was determined by testing the halves of the samples – beams 4×4×16 cm in size at 28 days of age. The abrasion of the investigated concrete was determined by testing cube specimens with an edge of 7.07 cm on an LKI-3 device in accordance with the procedure set forth in DSTU B.V.2.7-212: 2009 “Building materials. Concrete. Methods for determining abrasion “. The impact resistance of concrete was determined from the results of testing cubic specimens with an edge of 7.07 cm on a vertical dynamic laboratory test machine. Especially effective is manifested positive role hydrophobization basalt fiber in combination with the water-reducing additive Relaxol-Super PC. The introduction of hydrophobic fiber (2 kg/m3) and Relaxol – Super PC (1.2% by weight of cement) into the sand concrete mix provides an increase in the strength of sand concrete by 45 ... 48%, impact resistance by 45 ... 50%. The abrasion of concrete is reduced by 36 ... 48% compared to the control.
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Watanabe, Kazuo, Mugume Rodgers Bangi, and Takashi Horiguchi. "The effect of testing conditions (hot and residual) on fracture toughness of fiber reinforced high-strength concrete subjected to high temperatures." Cement and Concrete Research 51 (September 2013): 6–13. http://dx.doi.org/10.1016/j.cemconres.2013.04.003.
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Ali, Ahmed H., Hamdy M. Mohamed, Brahim Benmokrane, and Adel ElSafty. "Effect of applied sustained load and severe environments on durability performance of carbon-fiber composite cables." Journal of Composite Materials 53, no. 5 (July 25, 2018): 677–92. http://dx.doi.org/10.1177/0021998318789742.
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The research work reported in this paper involves investigation of the mechanical and durability performance of unstressed and stressed Tokyo Rope carbon-fiber composite cables for prestressing applications. This research is critical in order to establish the critical (allowable) stress and safety factors for the use of carbon-fiber composite cable tendons for prestressed precast-concrete members. The carbon-fiber composite cable specimens were exposed to simultaneous high alkali environment and sustained loading at different elevated exposure temperatures (22℃ and 60℃) for 3000, 5000, and 7000 h. The high alkali environment (12.8 pH) simulated the concrete pore solution and the elevated temperature was used to accelerate the aging process. The applied sustained stress on the carbon-fiber composite cable strands was equivalent to 40% and 65% of their guaranteed tensile strength. This was achieved through testing 171 carbon-fiber composite cable specimens subjected to stress levels of 0%, 40%, and 65% of their guaranteed strength, under tensile load. Also, 136 carbon-fiber composite cable specimens were tested to investigate the transverse shear strength. In addition, the durability characteristics of the constituent materials of the carbon-fiber composite cable strands were assessed to understand the long-term behavior of these materials. The results showed the effect of sustained stress on the degradation of carbon-fiber composite cable strands. Under sustained stress of 40% and 65%, the reductions in tensile strength were 10.6% and 12.3%, respectively. Scanning electron microscope results on epoxy resin indicated that no degradation is detected since the surface remains smooth without any pitting or loose material.
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Ibraheem, Muhammad, Faheem Butt, Rana Muhammad Waqas, Khadim Hussain, Rana Faisal Tufail, Naveed Ahmad, Ksenia Usanova, and Muhammad Ali Musarat. "Mechanical and Microstructural Characterization of Quarry Rock Dust Incorporated Steel Fiber Reinforced Geopolymer Concrete and Residual Properties after Exposure to Elevated Temperatures." Materials 14, no. 22 (November 15, 2021): 6890. http://dx.doi.org/10.3390/ma14226890.
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The purpose of this research is to study the effects of quarry rock dust (QRD) and steel fibers (SF) inclusion on the fresh, mechanical, and microstructural properties of fly ash (FA) and ground granulated blast furnace slag (SG)-based geopolymer concrete (GPC) exposed to elevated temperatures. Such types of ternary mixes were prepared by blending waste materials from different industries, including QRD, SG, and FA, with alkaline activator solutions. The multiphysical models show that the inclusion of steel fibers and binders can enhance the mechanical properties of GPC. In this study, a total of 18 different mix proportions were designed with different proportions of QRD (0%, 5%, 10%, 15%, and 20%) and steel fibers (0.75% and 1.5%). The slag was replaced by different proportions of QRD in fly ash, and SG-based GPC mixes to study the effect of QRD incorporation. The mechanical properties of specimens, i.e., compressive strength, splitting tensile strength, and flexural strength, were determined by testing cubes, cylinders, and prisms, respectively, at different ages (7, 28, and 56 days). The specimens were also heated up to 800 °C to evaluate the resistance of specimens to elevated temperature in terms of residual compressive strength and weight loss. The test results showed that the mechanical strength of GPC mixes (without steel fibers) increased by 6–11%, with an increase in QRD content up to 15% at the age of 28 days. In contrast, more than 15% of QRD contents resulted in decreasing the mechanical strength properties. Incorporating steel fibers in a fraction of 0.75% by volume increased the compressive, tensile, and flexural strength of GPC mixes by 15%, 23%, and 34%, respectively. However, further addition of steel fibers at 1.5% by volume lowered the mechanical strength properties. The optimal mixture of QRD incorporated FA-SG-based GPC (QFS-GPC) was observed with 15% QRD and 0.75% steel fibers contents considering the performance in workability and mechanical properties. The results also showed that under elevated temperatures up to 800 °C, the weight loss of QFS-GPC specimens persistently increased with a consistent decrease in the residual compressive strength for increasing QRD content and temperature. Furthermore, the microstructure characterization of QRD blended GPC mixes were also carried out by performing scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS).
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Zhurtov, Artur V., Tolya A. Khezhev, and Muhamed N. Kokoev. "An Investigation of the Stress-Strain State of Two-Layer Armocement Structures on the Power and Temperature Effects during a Fire." Materials Science Forum 931 (September 2018): 219–25. http://dx.doi.org/10.4028/www.scientific.net/msf.931.219.
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The effect of a fireproof vermiculite-concrete layer on the bearing capacity of the reinforced cement layer was tested by testing single-layer and two-layer armocement elements under pure bending under the conditions of a "standard fire". Temperature fields were obtained for single-layer and double-layer structures with one-sided heating by the Vanichev's method of thermal balances. It has been revealed that a fireproof layer made of vermiculite concrete with a thickness of 15 mm makes it possible to increase the load-bearing capacity of a thin-walled reinforcement cement structure in comparison with a single layer of the same thickness by 25% under the conditions of the "standard fire" temperature for one hour.
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Zhu, Yuefeng, Yanwei Li, Chundi Si, Xiaote Shi, Yaning Qiao, and Haoran Li. "Laboratory Evaluation on Performance of Fiber-Modified Asphalt Mixtures Containing High Percentage of RAP." Advances in Civil Engineering 2020 (January 29, 2020): 1–9. http://dx.doi.org/10.1155/2020/5713869.
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In recent years, the significant demand for sustainable paving materials has led to a rapid increase in the utilization of reclaimed asphalt pavement (RAP) materials. When RAP is mixed with virgin asphalt concrete, particularly when its percentage is high, performance of the binder and asphalt concrete can be adversely affected. For this reason, different types of additives need to be identified and evaluated beforehand to mitigate the adverse effects. In this study, different types of fiber materials were identified and selected as binder/mixture additives, including lignin fiber (LF), polyester fiber (PF), and basalt fiber (BF). Various samples of fiber-modified binders and asphalt mixtures with different RAP contents (0%, 20%, and 40%) were prepared and were evaluated using two sets of laboratory testing: (i) dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were performed to study the rheological properties of fiber-modified binders; (ii) the wheel tracking test, bending creep test, moisture susceptibility test, fatigue test, and self-healing fatigue test were conducted to characterize the laboratory properties of fiber-modified RAP mixtures. Test results for the modified binders show that the BF-modified binder has the greatest positive effect on the high-temperature performance of the asphalt binder, followed by PF- and LF-modified binders. However, the virgin asphalt shows the best low-temperature property than the fiber-modified asphalt binder. Test results for the whole RAP mixtures show that all fibers have a significant effect on the properties (including high- and low-temperature stability, moisture susceptibility, fatigue, and self-healing ability) of RAP mixtures. Among them, adding BF shows the greatest improvement in high-temperature stability, fatigue resistance, and self-healing ability of RAP mixtures. LF is found to significantly enhance low-temperature properties, and PF can greatly improve the resistance to moisture damage of RAP mixtures. For high percentage of RAP using on sites, adding multiple additives may further enhance its durability.
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Buller, Abdul Hafeez. "Effect of 6 Hour Fire on Flexural Strength of RC Beams made with 50% Coarse Aggregates from old concrete: Part 1: Normal mix." Quaid-e-Awam University Research Journal of Engineering, Science & Technology 19, no. 2 (December 27, 2021): 22–29. http://dx.doi.org/10.52584/qrj.1902.04.
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Shifting of people from villages/small cities to big cities poses a serious issue of accommodation and other associated infrastructure. For the solution of said issue, demolition of old structures to construct new high-rise buildings is opted. The demolishing waste is an additional problem for the project, particularly due to unavailability of the dumping space in many areas. A method of addressing the issue is by using it in new concrete. This research study presents an experimental investigation to check the effect of a 6-hour fire at 1000◦C on the bending resistance of reinforced concrete beams prepared by replacing 50% conventional coarse aggregate with coarse aggregate from demolished concrete. 24 RC beams of 0.9m × 0.15m × 0.15m size are cast using 1:2:4 mix and 0.54 water cement ratio. To reinforce the beams 2#4 bars in each tension and compression zones are used. Out of 24 beams, 12 are cast with all-natural coarse aggregates to compare the results. After 28-days standard curing, all beams are exposed to fire for 6 hours in purpose made oven. The beams are then left at room temperature for 24-hours followed by testing of all the beams in universal load testing machine with central point loading. Load and deflection are monitored at regular intervals. Comparison of the results with control specimen shows that the proposed beams observed 13.43% reduction in flexural strength which is quite smaller. The beams failed in shear which complies with the failure mode of normal concrete beams. Thus, the proposed material has good fire resistance when used in reinforced concrete beams.
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Naser, Mohannad, Rami Hawileh, and Hayder Rasheed. "Performance of RC T-Beams Externally Strengthened with CFRP Laminates under Elevated Temperatures." Journal of Structural Fire Engineering 5, no. 1 (March 1, 2014): 1–24. http://dx.doi.org/10.1260/2040-2317.5.1.1.
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This paper presents a numerical study that investigates the performance of reinforced concrete (RC) T-beams externally strengthened with carbon fibre reinforced polymer (CFRP) plates when subjected to fire loading. A finite element (FE) model is developed and a coupled thermal-stress analysis was performed on a RC beam externally strengthened with a CFRP plate tested by other investigators. The spread of temperature at the CFRP-concrete interface and reinforcing steel, as well as the mid-span deflection response is compared to the measured experimental data. Overall, good agreement between the measured and predicted data is observed. The validated model was then used in an extensive parametric study to further investigate the effect of several parameters on the performance of CFRP externally strengthened RC beams under elevated temperatures. The variables of the parametric study include applying different fire curves and scenarios, different applied live load combinations as well as the effect of using different insulation schemes with different types and thicknesses. Several observations and conclusions were drawn from the parametric investigation. It could be concluded that successful FE modeling of this structural member when exposed to thermal and mechanical loading would provide a valid economical and efficient alternative solution to the expensive and time consuming experimental testing.
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Loizos, Andreas, and Vasilis Papavasiliou. "Effect of Temperature Fluctuations on the Bearing Capacity of Cold In-Depth Recycled Pavements." Sustainability 14, no. 1 (December 31, 2021): 426. http://dx.doi.org/10.3390/su14010426.
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This study investigates the influence of the temperature fluctuations on the bearing capacity of cold in-depth recycled (CIR) pavements stabilized with foamed asphalt (FA). Aiming to achieve this goal, non-destructive testing was conducted during mild and high temperatures on a highway CIR pavement, utilizing mainly the FWD device. The back-calculated moduli values were utilized to estimate the strain values within the body of the pavement, while the strains induced using the FWD device were measured with a fiber optic sensors (FOS) system. Moreover, data from the fatigue behavior of the layer materials was also considered. The results of the related analysis indicate that for every 1 °C temperature increase within the body of the AC overlay, an approximately 5.7% increase of the critical tensile strain is expected. Moreover, for every 1 °C temperature increase within the body of the FA layer, an approximately 1.8% increase of the tensile strain at the bottom of the FA layer is expected. The new constructed layers, i.e., asphalt concrete (AC) and FA, sustain much more damage at high temperatures. This was more evident in the upper layer, i.e., the AC overlay.
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Gómez, Javier, Cristina Barris, Marta Baena, Ricardo Perera, and Lluís Torres. "Sustained Loading Bond Response and Post-Sustained Loading Behaviour of NSM CFRP-Concrete Elements under Different Service Temperatures." Applied Sciences 11, no. 18 (September 14, 2021): 8542. http://dx.doi.org/10.3390/app11188542.
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Nowadays, one of the foremost procedures for strengthening concrete structures is the Near-Surface Mounted (NSM) technique. This paper presents an experimental study on the effect sustained loading and different service temperatures (steady and cyclic) have on NSM Carbon Fibre-Reinforced Polymer (CFRP)-concrete bonded joints and their post-sustained loading load-slip behaviour. Four experimental campaigns using eight NSM CFRP-concrete specimens were performed by employing two different service load levels (15% and 30% of the ultimate load) and combining two groove thicknesses (7.5 and 10 mm) and two bonded lengths (150 and 225 mm). Two steady state temperatures (20 and 40 °C) and two cyclic service temperatures (ranging between 20 and 40 °C) were programmed. The slip obtained was proportional to the sustained load level. Furthermore, higher slips were registered for specimens under higher mean temperatures in the cycle. After 1000 h of sustained load testing, the specimens were tested under monotonic loading until failure (post-sustained loading tests). In general, the ratio between the post-sustained loading ultimate load and the instantaneous ultimate load was close to the unity, although some differences were perceived in series S2 (steady 37.7 °C) with a mean increase of 6.3%, and series S3-B (cyclic temperature ranging between 24.6 and 39.2 °C) with a mean reduction of 9%.
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Tępiński, Jarosław, Wojciech Klapsa, Krzysztof Cygańczuk, Piotr Lesiak, and Michał Lewak. "Testing of Large Scale Pool Fire of Technical Ethanol." Safety & Fire Technology 59, no. 1 (2022): 96–109. http://dx.doi.org/10.12845/sft.59.1.2022.5.
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Aim: The aim of this article is to determine the characteristics of a pool fire, including the temperatures and thermal radiation densities caused by it. Mappings of pool fires occurring in actual emergency events were conducted by performing large-scale polygon tests. Project and methods: Experimental study of pool fire of technical ethanol was carried out on a specially built test stand in the training area of the Training Centre in Pionki of the Regional Headquarters of the State Fire Service in Warsaw. The pool fire test stand consisted of a test tray, with a test chamber with the diameter of 300 cm, founded on a reinforced concrete slab. Using a developed measurement system with data acquisition that included measurement sensors mounted at defined locations relative to the fire, temperatures and thermal radiation densities were measured at various distances/locations relative to the fire. Metrological data such as air temperature, atmospheric pressure, humidity, wind direction and speed were monitored and recorded using the weather station. The height of the fire flame was measured by comparing it to racks set up nearby with marked scales of specific lengths. Results: A polygon stand that was built to study pool fires, equipped with a temperature and thermal radiation density measuring system with measuring sensors distributed in defined locations, is discussed. A study of a pool fire resulting from the combustion of dehydrated, fully contaminated ethanol was conducted. The study measured temperatures, thermal radiation densities, and flame heights. The average and maximum values of temperatures and thermal radiation densities during the steady-state combustion stage (i.e., phase II of the fire) were determined. Conclusions: Based on the presented results of temperature and thermal radiation density measurements at various distances/locations relative to the pool fire site, there was a significant effect of wind direction and speed on these values. Higher temperature and heat radiation density were recorded at the sensors on the leeward side than on the windward side. As the wind speed decreased, there was an increase in the temperature values recorded on the thermocouples located above the centre of the bottom of the tray test chamber due to the flame, which, when not blown away, was allowed to rise vertically upward and fully sweep the temperature sensors. Keywords: pool fire, field tests, technical ethanol, temperature, thermal radiation Type of article: original scientific article
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Al-Rousan, Rajai Z. "Influence of Macro Synthetic Fibers on the Flexural Behavior of Reinforced Concrete Slabs with Opening." Civil Engineering Journal 8, no. 9 (September 1, 2022): 2001–21. http://dx.doi.org/10.28991/cej-2022-08-09-016.
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In this study, the flexural behavior of one-way RC slabs after adding the macro discontinuous structural synthetic fiber (DSSF) under different opening sizes is investigated. Based on the previously conducted research, the 0.55 DSSF percentage was utilized since it was reported as the optimum value for enhancing the slab's performance. Moreover, further increases in the DSSF percentages proved to have the same improvement obtained by the 0.55%. Experimental testing was carried out on sixty-four one-way slabs under the effects of square opening existence (with or without), heat levels of 20, 200, 400, and 600 °C, and opening sizes of 100, 150, and 200 mm. The opening was created at the maximum bending moment region at the slab's center between the two loading points. For comparison purposes, the tested slabs were divided into main groups based on the DSSF existence. It was found that the resulted improvement by adding the DSSF material is affected by the size of the created opening. Furthermore, results revealed an increasing linear relationship between the applied load and the deflection and between the longitudinal concrete strain and the steel reinforcement. Besides, duplicating the opening size enhances the ductility index value by a maximum improvement percentage of 13% under an opening size ratio of less than 4.5%, while the improvement percentage becomes less under a further increase in the opening size ratio. Moreover, initial stiffness is more affected by increasing the temperature values twice those recorded for the yielding stiffness. Doi: 10.28991/CEJ-2022-08-09-016 Full Text: PDF
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Mashaan, Nuha Salim, Mohamed Rehan Karim, Mahrez Abdel Aziz, Mohd Rasdan Ibrahim, Herda Yati Katman, and Suhana Koting. "Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness." Scientific World Journal 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/968075.
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Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.
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Suleimenova, F. E., El Sayed Negim, R. H. Sharipov, and E. N. Suleimenov. "Investigation of the microstructure of the oil pipeline pipes destroyed as a result of corrosion." Kompleksnoe Ispolʹzovanie Mineralʹnogo syrʹâ/Complex Use of Mineral Resources/Mineraldik Shikisattardy Keshendi Paidalanu 323, no. 4 (May 23, 2022): 60–67. http://dx.doi.org/10.31643/2022/6445.41.
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It is shown that the complexity of Kazakhstan's oils requires specific ways to protect oil pipelines from damage caused by metal corrosion. Even the presence of only paraffin in oil can cause sedimentation effects in the volume of liquid (Dorn effect). And the complexity in the molecular composition of oil causes electrophoretic impacts that lead to increased corrosion rate. All this should be considered when developing corrosion protection. The physical and mathematical analysis of possible mechanisms of electrophoretic mobility of components with the participation of liquid systems was carried out. In such a system with ions content, the macroscopic object will move as a charged particle having the same charge sign as the skeleton. The triboelectric effects on the metal/organic liquids (oil, fuel oil, etc.) boundary have been analyzed to determine their influence on the corrosion of pipeline metals. There are many methods used for temperature-strength control of reinforced concrete structures globally. Their majority is associated with the significant challenges of being time-consuming, costly, and prone to errors. Therefore, this study investigated the potential applicability of the surface-strength approach of specimens using non-destructive testing methods to derive temperature-strength relationships as an alternative approach to the currently widely used methods.
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Sauca, Ana, Thomas Gernay, Fabienne Robert, Nicola Tondini, and Jean-Marc Franssen. "Hybrid fire testing." Journal of Structural Fire Engineering 9, no. 4 (December 10, 2018): 319–41. http://dx.doi.org/10.1108/jsfe-01-2017-0017.
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Purpose The purpose of this paper is to propose a method for hybrid fire testing (HFT) which is unconditionally stable, ensures equilibrium and compatibility at the interface and captures the global behavior of the analyzed structure. HFT is a technique that allows assessing experimentally the fire performance of a structural element under real boundary conditions that capture the effect of the surrounding structure. Design/methodology/approach The paper starts with the analysis of the method used in the few previous HFT. Based on the analytical study of a simple one degree-of-freedom elastic system, it is shown that this previous method is fundamentally unstable in certain configurations that cannot be easily predicted in advance. Therefore, a new method is introduced to overcome the stability problem. The method is applied in a virtual hybrid test on a 2D reinforced concrete beam part of a moment-resisting frame. Findings It is shown through analytical developments and applicative examples that the stability of the method used in previous HFT depends on the stiffness ratio between the two substructures. The method is unstable when implemented in force control on a physical substructure that is less stiff than the surrounding structure. Conversely, the method is unstable when implemented in displacement control on a physical substructure stiffer than the remainder. In multi-degrees-of-freedom tests where the temperature will affect the stiffness of the elements, it is generally not possible to ensure continuous stability throughout the test using this former method. Therefore, a new method is proposed where the stability is not dependent on the stiffness ratio between the two substructures. Application of the new method in a virtual HFT proved to be stable, to ensure compatibility and equilibrium at the interface and to reproduce accurately the global structural behavior. Originality/value The paper provides a method to perform hybrid fire tests which overcomes the stability problem lying in the former method. The efficiency of the new method is demonstrated in a virtual HFT with three degrees-of-freedom at the interface, the next step being its implementation in a real (laboratory) hybrid test.
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Jain, Amit, and Bora Gencturk. "Multiphysics and Multiscale Modeling of Coupled Transport of Chloride Ions in Concrete." Materials 14, no. 4 (February 13, 2021): 885. http://dx.doi.org/10.3390/ma14040885.
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Chloride ions (Cl−)-induced corrosion is one of the main degradation mechanisms in reinforced concrete (RC) structures. In most situations, the degradation initiates with the transport of Cl− from the surface of the concrete towards the reinforcing steel. The accumulation of Cl− at the steel-concrete interface could initiate reinforcement corrosion once a threshold Cl− concentration is achieved. An accurate numerical model of the Cl− transport in concrete is required to predict the corrosion initiation in RC structures. However, existing numerical models lack a representation of the heterogenous concrete microstructure resulting from the varying environmental conditions and the indirect effect of time dependent temperature and relative humidity (RH) on the water adsorption and Cl− binding isotherms. In this study, a numerical model is developed to study the coupled transport of Cl− with heat, RH and oxygen (O2) into the concrete. The modeling of the concrete microstructure is performed using the Virtual Cement and Concrete Testing Laboratory (VCCTL) code developed by the U.S. National Institute of Standards and Technology (NIST). The concept of equivalent maturation time is utilized to eliminate the limitation of simulating concrete microstructure using VCCTL in specific environmental conditions such as adiabatic. Thus, a time-dependent concrete microstructure, which depends on the hydration reactions coupled with the temperature and RH of the environment, is achieved to study the Cl− transport. Additionally, Cl− binding isotherms, which are a function of the pH of the concrete pore solution, Cl− concentration, and weight fraction of mono-sulfate aluminate (AFm) and calcium-silicate-hydrate (C-S-H), obtained from an experimental study by the same authors are utilized to account for the Cl− binding of cement hydration products. The temperature dependent RH diffusion was considered to account for the transport of Cl− with moisture transport. The temperature and RH diffusion in the concrete domain, composite theory, and Cl− binding and water adsorption isotherms are used in combination, to estimate the ensuing Cl− diffusion field within the concrete. The coupled transport process of heat, RH, Cl−, and O2 is implemented in the Multiphysics Object-Oriented Simulation Environment (MOOSE) developed by the U.S. Idaho National Laboratory (INL). The model was verified and validated using data from multiple experimental studies with different concrete mixture proportions, curing durations, and environmental conditions. Additionally, a sensitivity analysis was performed to identify that the water-to-cement (w/c) ratio, the exposure duration, the boundary conditions: temperature, RH, surface Cl− concentration, Cl− diffusion coefficient in the capillary water, and the critical RH are the important parameters that govern the Cl− transport in RC structures. In a case study, the capabilities of the developed numerical model are demonstrated by studying the complex 2D diffusion of Cl− in a RC beam located in two different climatic regions: warm and humid weather in Galveston, Texas, and cold and dry weather in North Minnesota, Minnesota, subjected to time varying temperature, RH, and surface Cl− concentrations.
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Bieranowski, Piotr, and Piotr Knyziak. "Non-invasive tests of precast cantilever balcony in OWT-67 system." MATEC Web of Conferences 196 (2018): 02023. http://dx.doi.org/10.1051/matecconf/201819602023.
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This article presents a non-invasive tests report of precast cantilever balcony support in OWT-67 large-panel system. During field testing, the balcony's reinforced concrete structure was subjected to radiometric analysis in the context of thermal energy distribution as well as from the point of view of mycology - to the possible presence of spores of domestic fungi. The temperature distribution tests carried out by means of the electromagnetic wave detection in the infrared spectrum clearly confirmed the significant losses of thermal energy caused by the effect of the thermal constructional bridge located in the balcony. Mycological diagnosis was carried out using the rapid test of the Mycometer bacterial meter, which allows fluorimetric evaluation of the presence of the enzyme presence in filamentous fungi. In the conducted study, no spores of the house mushroom were found on the inside surface of the Z-type balcony supporting beam as a place where condensation of water vapor may occur. The summary also presents a design solution that allows to eliminate this physical problem.
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Liu, Yong Jun, Qing Hong Zeng, Hong Ru Liu, and Shuo Xun Wang. "Experimental Study on Post Fire Tensile Properties of Reinforcing Rebars Connected by Grout-Filled Splice Sleeves." Key Engineering Materials 773 (July 2018): 305–10. http://dx.doi.org/10.4028/www.scientific.net/kem.773.305.
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This paper presents some experimental results of tensile properties of reinforcing bars spliced by grout-filled coupling sleeves after exposed to fires to identify the effect of temperature histories on tensile properties of spliced reinforcing bars, which provide a useful base for assessing structural behaviors of precast reinforced concrete buildings damaged by fires. A spliced rebar system investigated in this paper consists of two equal-diameter steel reinforcing bars with 25mm diameter and a straight coupling sleeve with 55mm outer and 42mm inner diameters. As a result, the thickness of grout between internal steel bars and outer sleeves are 8.5mm. Five test specimens are manufactured in identical technology and divided into three groups. First group is reference group consist of just one specimen which is not exposed to fire. Second and third groups consist of two specimens that are exposed to ISO 834 standard fire in furnace for 15 and 25 minutes respectively. The temperature-time curves of grout between rebars and sleeves are measured via thermocouples embedded in grout. Subsequently, a universal testing machine is used to test the ultimate load bearing capacities of five specimens. Test results demonstrate that ultimate load bearing capacities of steel rebars spliced by grout-filled sleeves are considerably reduced due to fire damaged grout.
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Gailitis, Rihards, Andina Sprince, Tomass Kozlovksis, Leonids Pakrastins, and Viktorija Volkova. "Impact of Polypropylene, Steel, and PVA Fibre Reinforcement on Geopolymer Composite Creep and Shrinkage Deformations." Journal of Physics: Conference Series 2423, no. 1 (January 1, 2023): 012030. http://dx.doi.org/10.1088/1742-6596/2423/1/012030.
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Abstract For the last 40 years, there has been increased interest in geopolymer composite development and its mechanical properties. In the last decades, there have been cases when geopolymer composites have been used for civil engineering purposes, such as buildings and infrastructure projects. The main benefit of geopolymer binder usage is that it has a smaller impact on the environment than the Portland cement binder. Emissions caused by geopolymer manufacturing are at least two times less than emissions caused by Portland cement manufacturing. As geopolymer polymerization requires elevated temperature, it also has a significant moisture evaporation effect that further increases shrinkage. It can lead to increased cracking and reduced service life of the structures. Due to this concern, for long-term strain reduction, such as plastic and drying shrinkage and creep, fibre reinforcement is added to constrain the development of stresses in the material. This research aims to determine how different fibre reinforcements would impact geopolymer composites creep and shrinkage strains. Specimens for long-term property testing purposes were prepared with 1% of steel fibres, 1% polypropylene fibres (PP), 0.5% steel and 0.5% polyvinyl alcohol fibres, 5% PP fibres, and without fibres (plain geopolymer). The lowest creep strains are 5% PP fibre specimens, followed by 1% PP fibre, plain, 0.5% steel fibre and 0.5% PVA fibre, and 1% steel fibre specimens. The lowest specific creep is to 5% PP fibre reinforced specimens closely followed by 1% PP fibre followed by 0.5% steel and 0.5% PVA fibre, plain and 1% steel fibre reinforced composites. Specimens with 0.5% steel and 0.5 PVA fibre showed the highest compressive strength, followed by 1% PP fibre specimens, plain specimens, 1% steel fibre, and 5% PP fibre reinforced specimens. Only specimens with 1% PP fibre and 0.5% steel, and a 0.5% PVA fibre inclusion showed improved mechanical properties. Geopolymer concrete mix with 1% PP fibre inclusion and 0.5% steel and 0.5% PVA fibre inclusion have a 4.7% and 11.3% higher compressive strength. All the other fibre inclusion into mixes showed significant decreases in mechanical properties.
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Zaidi, A., and R. Masmoudi. "Thermal effect on fiber reinforced polymer reinforced concrete slabs." Canadian Journal of Civil Engineering 35, no. 3 (March 2008): 312–20. http://dx.doi.org/10.1139/l07-110.
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The difference between the transverse coefficients of thermal expansion of fiber reinforced polymer (FRP) bars and concrete generates radial pressure at the FRP bar – concrete interface, which induces tensile stresses within the concrete under temperature increase and, eventually, failure of the concrete cover if the confining action of concrete is insufficient. This paper presents the results of an experimental study to investigate the thermal effect on the behaviour of FRP bars and concrete cover, using concrete slab specimens reinforced with glass FRP bars and subjected to thermal loading from –30 to +80 °C. The experimental results show that failure of concrete cover was produced at temperatures varying between +50 and +60 °C for slabs having a ratio of concrete cover thickness to FRP bar diameter (c/db) less than or equal to 1.4. A ratio of c/db greater than or equal to 1.6 seems to be sufficient to avoid splitting failure of concrete cover for concrete slabs subjected to high temperatures up to +80 °C. Also, the first cracks appear in concrete at the FRP bar – concrete interface at temperatures around +40 °C. Comparison between experimental and analytical results in terms of thermal loads and thermal strains is presented.
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Avubothu, Maheshwari, Saiteja Ponaganti, Ramya Sunkari, and Mounika Ganta. "Effect of high temperature on coconut fiber Reinforced concrete." Materials Today: Proceedings 52 (2022): 1197–200. http://dx.doi.org/10.1016/j.matpr.2021.11.036.
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Shi, Nan Nan, and Da Hai Huang. "Experimental Study on Early-Age Crack of RC Using TSTM." Advanced Materials Research 919-921 (April 2014): 119–22. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.119.
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Thermal stress is a major cause of early-age crack of massive concrete structures. In order to analyze the influencing factors of concrete crack under thermal loads, a series of tests were conducted using the improved Temperature Stress Testing Machine (TSTM). Effects of temperature on crack resistance of concrete were studied on different concrete placing temperatures and curing temperatures. Meanwhile, the roles of reinforcement on concrete crack resistance and crack-width limitation were quantitative analyzed, which compare cracks of plain concrete and reinforced concrete with the same mix proportion. The results indicate that reinforcement can improve the crack resistance of the structures by approximately twenty percents, which against the engineering experience. After concrete cracks, the cracks photos show that reinforcement can induce the smaller cracks formation, and the crack width of reinforced concrete is about 1/10 of the plain concrete crack width.
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Deng, Wen Qin, and Jing Zhao. "Structure Characteristics and Mechanical Properties of Fiber Reinforced Concrete." Advanced Materials Research 168-170 (December 2010): 1556–60. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.1556.
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Mechanical properties of fiber reinforced concrete with polypropylene fiber, alkali-resistant glass fiber and basalt fiber separately were studied in this paper. The internal structure of fiber reinforced concrete was researched by testing chloride ion diffusion coefficient and scanning electron microscope (SEM) analysis. The results show that adding a certain amount of three fibers separately into concrete have all increased splitting strength. Compared with referenced concrete, compressive strength of alkali-resistant glass fiber reinforced concrete and basalt fiber reinforced concrete are both improved. According to analysis, the effect of srengthening and toughening for basalt fiber is particularly significant. The order of chloride ion diffusion coefficient from lower to higher is alkali-resistant glass fiber reinforced concrete, referenced concrete, basalt fiber reinforced concrete, polypropylene fiber reinforced concrete. This result indicates that alkali-resistant glass fiber bonds cement paste best and makes internal structure densest by SEM analysis.
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Holovata, Zlata, Daria Kirichenko, Irina Korneeva, Stepan Neutov, and Marina Vyhnanets. "Experimental Studies of Fiber-Reinforced Concrete under Axial Tension." Materials Science Forum 1038 (July 13, 2021): 323–29. http://dx.doi.org/10.4028/www.scientific.net/msf.1038.323.
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The design of a stand for testing concrete and fiber-reinforced concrete specimens-"eight" in tension, which provides axial load application and minimizes the effect of stress concentration at the ends of the specimen. The design of the stand is such that the distance between the axis of load application and the central hinge is 108 cm, and between this hinge and the axis of the test specimen is 21 cm, as a result of which the load transferred to the specimen is 5.143 times greater than the applied one. At the first stage of testing, it was found that the optimal characteristics of the fiber-concrete mixture is a matrix with a large aggregate ≤ 10 mm with 1.0% fiber reinforcement. At the second stage, the ultimate strength of fiber-reinforced concrete for axial tension was determined - 1.28 MPa when reinforced with wave fiber and 1.37 MPa when reinforced with anchor fiber, which amounted to 4.1% and 4.4% of compressive strength, respectively. It was also found that concrete reinforced with anchor fiber has higher deformation properties than concrete reinforced with wave fiber.
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Dong, Liang Feng, and Shi Ping Zhang. "Effect of Steel Fiber on Comprehensive Performance of Concrete Materials." Applied Mechanics and Materials 723 (January 2015): 440–44. http://dx.doi.org/10.4028/www.scientific.net/amm.723.440.
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This paper presents the results on the influence of steel fiber on the performance of concrete materials. The performance of steel fiber reinforced concrete was studied through mechanical testing, frost resistance, carbonation and impermeability testing. Experimental results showed that steel fibers can improve compressive and flexural strengths, and especially can significantly improve flexural strength. Frost resistance can also be improved, and the higher the volume of steel fibers added, the more the freeze-thaw cycles that concrete could resist. Furthermore, steel fiber can not only slow down the carbonation rate indirectly, but also improve the impermeability of concrete, and impermeability enhanced with the increase of steel fiber.
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Bezerra, Augusto C. S., Priscila S. Maciel, Elaine C. S. Corrêa, Paulo R. R. Soares Junior, Maria T. P. Aguilar, and Paulo R. Cetlin. "Effect of High Temperature on the Mechanical Properties of Steel Fiber-Reinforced Concrete." Fibers 7, no. 12 (November 21, 2019): 100. http://dx.doi.org/10.3390/fib7120100.
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The effect of high temperature on the mechanical properties of concrete reinforced by steel fibers with various aspect ratios has been investigated in this study. Concrete specimens were fabricated from four different concrete mixtures and cured for 28 days. After curing and natural drying, the specimens were annealed at a temperature of 500 °C for 3 h in an electric furnace. The compressive and tensile strengths as well as the elastic moduli of the produced specimens were determined. It was found that the mechanical properties (especially flexural toughness) of steel fiber-reinforced concrete were less affected by high temperature as compared to those of control concrete specimens. The flexural tensile strength of fiber-reinforced concrete measured after high-temperature treatment was almost equal to the value obtained for the reference concrete specimen at room temperature. It should be noted that the addition of steel fibers to concrete preserves its mechanical properties after exposure to a temperature of 500 °C due to fire for a period of up to 3 h, and thus is able to improve its high-temperature structural stability. The test results of this study indicate that the use of steel fibers in concrete-based materials significantly enhances their fire and hear-resistant characteristics.
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Fořt, Jan, Jaroslav Pokorný, David Čítek, Jiří Kolísko, and Zbyšek Pavlík. "The Effect of Elevated Temperature on High Performance Fiber Reinforced Concrete." Materials Science Forum 824 (July 2015): 191–95. http://dx.doi.org/10.4028/www.scientific.net/msf.824.191.
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High performance fiber reinforced concrete (HPFRC) became very popular material due to its high strength, elastic modulus, corrosion and fire resistance. However, detail description of HPFRC behaviour is necessary for its application and an effective building design and development. Here, also the fire safety of buildings must be considered. Therefore, the effect of elevated temperature on HPFRC is studied in the paper. For the reference material, experimental assessment of basic physical and mechanical properties is done. Then, the HPFRC samples are exposed to the temperatures of 600 and 800 °C respectively, and the effect of a high temperature exposure on material structure is examined. It is found that the applied high temperature loading significantly increases material porosity due to the physical, chemical and combined damage of material inner structure, and negatively affects also the pore size distribution.