Development of Eco-Friendly Deconstruction Technologies for Recycling Construction Waste

Transcription

1 Journal of Environmental Protetion, 214, 5, Published Online May 214 in SiRes. Development of Eo-Friendly Deonstrution Tehnologies for Reyling Constrution Waste Myungkwan Lim 1,2, Heesup Choi 1,2*, Hyeonggil Choi 3, Ryoma Kitagaki 3, Takahumi Noguhi 3 1 Department of Arhteture Engineering, Hankyong National University, Gyeonggi-do, Korea 2 Department of Civil Engineering, Kitami Institute of Tehnology, Hokkaido, Japan 3 Department of Arhiteture, The University of Tokyo, Tokyo, Japan * hoiheesup@gmail.om Reeived 25 Marh 214; revised 25 April 214; aepted 19 May 214 Copyright 214 by authors and Sientifi Researh Publishing In. This work is liensed under the Creative Commons Attribution International Liense (CC BY). Abstrat Reently, the intended use and required performane of buildings are rapidly hanging with advanes in sientifi tehnology and globalization. Furthermore, given the population growth in semi-developed and developing ountries, eonomi growth, inreasing waste, and inreasing amounts of energy onsumption, the industry requires the development of effiient methods to deonstrut old buildings by reduing waste and saving as muh energy as possible during periods of urban redevelopment and maintenane. In general, either an ordinary breaker or a hydrauli breaker is used to deonstrut reinfored onrete buildings. This deonstrution method has the ability to shorten the onstrution period ompared to the other methods, but it is diffiult to separate the debris that gets mixed when the deonstrution is ompleted, as it is a rough onstrution method that uses large equipment. This study develops a tehnology that an be used to seletively heat, separate, and deonstrut the steel reinforement inside reinfored onrete, treating the reinforement as a ondutive resistor and applying high-frequeny indution heating to the reinfored onrete struture. Speifially, this study verifies the temperature harateristis of deformed bars inside reinfored onrete, the ourrene of raks due to thermal frature of the deformed bars, and hemial and physial weakening of onrete by thermal ondution on the surfae of steel reinforement using the high-frequeny indution heating tehnology. Furthermore, this study onsiders the extent of onrete weakening in the heating range of appropriate energy and arries out a tehnial review of the stages that would be atually applied. This tehnology involves low noise and low pollution levels, and it inreases the olletion rate of steel reinforement inside separated reinfored onrete members and the reyling rate of onstrution wastes; thus, * Corresponding author. How to ite this paper: Lim, M., et al. (214) Development of Eo-Friendly Deonstrution Tehnologies for Reyling Constrution Waste. Journal of Environmental Protetion, 5,

2 its use is expeted to redue the energy onsumption by minimizing seondary proessing. Keywords Reyling, Deonstrution, Heat Indution, Ease to Srap, Weakening 1. Introdution Despite the annually inreasing number of buildings, there is little literature on deonstrution methods. Deonstrution is stritly onstrained by the surrounding environments, espeially in downtown areas, and environmental pollution and safety issues suh as the noise, vibration, and dust that our during the deonstrution proess also ause problems [1] [2]. The existing deonstrution methods rely largely on labor owing to the lak of deonstrution tehnology and experiene, whih auses waste of labor and loss of available materials as well as extended onstrution period [3]. The existing deonstrution methods do not onsider the reyling of debris that ours during the deonstrution proess [4]. The reason why the atual reyling rate is problemati despite ontinuous reyling of wasted onrete lies in the existing deonstrution methods [5], in whih various problems related to the reuse and reyling of wastes that our owing to indisriminate deonstrution have been pointed out [6] [7]. In the ase of a hydrauli breaker or large breaker, the representative method for the urrent separating dismantlement, it is neessary to separate onrete members and waste. In partiular, in the ase of reinfored onrete members dismantled using heavy equipment, various problems an our with regard to the reuse of steel reinforement and reyling of waste onrete [8]. It is neessary to onvert the urrent first dismantle and then separate method to a separate first and then dismantle method and develop tehnology to improve the reyling rate that onsiders the effiient ollet of demolished debris in the dismantlement stage. It is neessary to develop a partial-dismantlement tehnology that is effetive for remodeling and repair reinforement. Partial dismantlement, whih is on the rise with the inrease in remodeling and repair reinforement, requires various tehnial appliations and developments that are different from the existing dismantlement in terms of prevention of damage to the remaining struture or improvement in safety. It is neessary to propose a omprehensive management system that systemizes separating dismantlement and partial dismantlement to promote the development of the urrent dismantlement industry and of the entire arhitetural industry. This seures safety in dismantling onstrution, redution in environment-polluting fators, proper handling of generated waste, and improvement in the reyling rate. 2. Complete Deonstrution Tehnology for Reinfored Conrete Members Using High-Frequeny Indution Heating Method 2.1. Steel Reinforement Heating Mehanism Depending on High-Frequeny Indution Heating (Joule Heat) Indution heating is a method that is used to heat ondutive resistors suh as metals by eletrial energy that is onverted from a high-frequeny urrent-arrying ondutor known as an indution oil. If alternating urrent flows in the lead wire, a line of magneti fore with hanging diretion and intensity in the surroundings ours. If ondutive materials (usually metal) are plaed in the surroundings, as shown in Figure 1, an eddy urrent flows inside the metal, influened by this hanging line of magneti fore. As metal usually has an eletrial resistane, Joule heating [eletriity = urrent 2 ] ours, and the metal is heated if the urrent flows in the metal. This phenomenon is alled indution heating. Indution heating is less likely to be a risk, and the heat loss is also less, although the temperature rises in the non-heated areas, beause only the metal is heated [9] [1] Skin Effet and Depth of Penetration δ In general, most urrents are onentrated on the surfae of a ondutive resistor beause the urrent density drops at the enter of the ondutive resistor if alternating urrent flows through it. This phenomenon is alled the skin effet. When it gets loser to the enter of the ondutive resistor, the ross veloity of the magneti 648

3 φ i 1 Eddy 渦電流 Current i 1 i 2 Figure 1. High-frequeny indution heating mehanism. Magneti flux φ depending on alternating urrent i 1 ; Indued urrent (Eddy Current i 2 ). field speeds up. It an also be aused by the diffiult flow of alternating urrent when the indutane inreases. In Equation (1), δ [mm], the penetration depth of a high-frequeny urrent is determined by the material permeability μ [H/m], the ondutivity of the heated objet σ [Ʊ/m], and the frequeny [Hz]. Equation (1) shows the penetration depth inreases when the frequeny dereases or when the material permeability and ondutivity of the heated objet derease. As 9% of heating ours from the surfae to δ in terms of urrent and power distribution, it an be said that all eddy urrents are onentrated to the depth of penetration δ from the surfae of a ondutive resistor [11] [12] Thermal Model of Steel Reinforement Using High-Frequeny Indution Heating If high-frequeny alternating-urrent flows into the oil, an eddy urrent is indued and ats as soure of heat that depends on the resistane of metal; here, resistane auses heat in the metal. In the ase of high-frequeny indution heating, there is a large differene in heating effiieny depending on the magneti harateristis of the heated objet, but a larger eddy urrent is indued with a magneti substane, whih is signifiantly affeted by the magneti field, depending on the hanges in time [13]. As shown in Equation (2), the hysteresis onstant η varies depending on the magneti quality of a material; unlike the general transformer, it is easy to heat material with larger η in indution heating. However, as the heated objets are not usually made in a losed iruit like a transformer, the density of the magneti field veloity and the effetive permeability are small and η is also small, even if the heated objet is a magneti substane like ast iron. In addition, if the frequeny is over about 1 [khz], the hysteresis loss depending on the indution heating an be negleted beause the eddy urrent loss is overwhelmingly greater than the square of frequeny (as shown in Figure 2). In the ase of a magneti substane, the effiieny of the heating surfae inreases beause the depth of penetration dereases with inreasing relative permeability. For steel reinforement, with a relatively high permeability, loalized heating on the surfae is possible beause the indued urrent is onentrated on the areas faing the heating oil when the magneti field ourred from the oil is absorbed into the surfae of the metal. In addition, seletively loalized heating is possible beause the sope of the magneti field an be adjusted aording to the diameter of the heating oil. Figure 3 represents the heating model of steel reinforement, whih depends on the high-frequeny indution heating [13] [14]. (2) η: hysteresis onstant. V: entral volume of steel reinforement (m 3 ). The priniple of the magneti field generated by the oil is summarized in aordane with Maxwell s equations. As shown in Figure 3, oils are distributed within a partiular spae; if urrent ί(t) is flowing, the magneti vetor potential A ours at any point within the spae P(x, y, z). Equation (3) is the interation formula for both the urrent density J and the magneti vetor potential A. µ J A = dv 4π (3) V γ (1) 649

4 Figure 2. Hysteresis loop [15]. うず電流 ( 誘導電流 I 2 ) Eddy Current (Indued Current) Alternating 交流 ⅠI 11 Line of Magneti Fore 磁力線 Figure 3. Thermal Model of Steel Reinforement Depending on High-Frequeny Indution Heating. If urrent is alternating, the magneti vetor potential A is also alternating. Equation (4) is the relationship between the magneti vetor potential and the magneti flux density (magneti field veloity) B. B = A (4) If the magneti vetor potential A is alternating, the magneti flux density B is also alternating. Therefore, if a ondutive resistor is used, power failure E ours depending on Equation (5). From this urrent, an eddy urrent J ours. B E = (5) t J = σ E (6) σ: ondutivity of a ondutive resistor. The entire magneti field is determined mutually by the magneti field due to the urrent that flows in the oil and the magneti field due to the Fouault urrent. This auses an eletromotive fore in the oil. As shown in Equation (7), the eletromotive fore in the oil is the eletri field that ours when heating the oil. A V = E d = d (7) t Therefore, a magneti field in the enter of the steel reinforement, a ondutive resistor, ours that depends on the distribution of the eddy urrent, if oils are distributed losely to the steel reinforement [15]. 3. Temperature Charateristis of Single Steel Reinforement Depending on High-Frequeny Indution Heating 3.1. Experimental Overview This study arries out an experiment to analyze the temperature harateristis of a deformed bar, ommonly used as a ondutive resistor in high-frequeny indution heating, and the temperature distribution of steel reinforement aordingly. This study sets the onditions for the diameter and length of steel reinforement, espeially of the deformed bar widely used in the field, the temperature rise harateristis and temperature distribution depending on the distane from the heating oil to the surfae of steel reinforement, and the 65

5 quantity of output as experimental fators. This study identifies the temperature rise harateristis and temperature distribution at various onditions beause there are large differenes in heating effiieny depending on the differenes in heat transfer oeffiients by ross-setional area and distane of steel reinforement within the range of the magneti field in high-frequeny indution heating. In addition, the main purpose is to predit the temperature harateristis as basi information for various arrangements of steel reinforement. Furthermore, this study determines the optimal onditions for output and heating positions beause the depth of penetration varies with the frequeny Experimental Method Indution Heating Devie For indution heating, this study uses an experimental devie with a basi frequeny of 12 khz (operating frequeny of 6-12 khz) and a maximum high-frequeny output of 6 kw. The output stability is ±2%, and the output an be adjusted depending on the DC voltage [16]. High-frequeny indution heating is a harateristi of the hanged operating frequeny when hanging the oils, beause the heating oil and heated objet beome one omponent of the iruit, and the high-frequeny power is set by a resonant ondenser inside the mathing iruit, output lead, indutane, and indutane of heating oil. Resonant frequeny employs an automati traking method. The heating oil is a fan-ake type and uses a oil with dimension of φ 12, rev ount of 3, and oil thikness of φ Steel Reinforement Heating Experiment For the single steel reinforement heating experiment, this study uses 15-mm steel reinforement samples of D6, D1, D19, D25, and D32 in SD345 to identify the temperature distribution of steel reinforement depending on the optimum output and heating. The maximum output is either 5 kw or 6 kw, and the experiment is arried out by hanging the distane from the surfae of the steel reinforement to the lower bottom of the indution heating oil and measuring the temperature at the entral point on the surfae of steel reinforement. To form an arrangement similar to that of reinfored onrete speimens, this study arries out an experiment by utting every steel reinforement sample to 43 mm. This study measures the temperature at three positions using a heat-resistant amera: at the enter of the surfae of steel reinforement, at the part faing the oil diameter, and at the part 3 m away from the oil diameter. The heating experiment method for single steel reinforement is show in Figure Temperature Rise Charateristis of Single Steel Reinforement Depending on High-Frequeny Indution Heating The temperature rise harateristis of steel reinforement with indution heating (length: 15 mm) are presented in Figure 5 for output powers of 5 kw and 6 kw. As temperatures of 8 C or above are diffiult to measure, any temperature above this mark is regarded as being at 8 C. There are no large differenes between 5 kw and 6 kw. Over a ertain output, the depth of penetration with indution heating inreases depending on the quantity of output, but if the temperature is over the Curie temperature at the surfae of the steel reinforement, the relative permeability falls to 1 [17]. The output of the eletri field drops and loss ours beause the eletri field reahes the ritial temperature, even in the inside, without being further inreased. In the relationship between time and temperature, the targeted temperature (onrete-weakening temperature) reahed up to 3 C within 6 seonds when the distane from the heating oil to the surfae of steel reinforement was 1 mm, 2 mm, or 3 mm. As the distane dereased, the temperature rose rapidly, to 6 C or above. In addition, at distanes of 1 mm or 2 mm, there is a thermal equilibrium between 6 C - 8 C, and at a distane of 3 mm, there is a thermal equilibrium between 5 C - 7 C. At 5 mm, the temperature redues to 3 C in about 3 s. D6, D1, D19, and D25 showed a rapid temperature rise harateristi, but D32 showed redued temperature rise trend ompared to the other types of steel reinforement. This may our beause as the indution heating heats the surfae of steel reinforement rapidly, the steel reinforement with a thik diameter requires time to obtain a temperature differene by heating until the moleular motion an beome onstant depending on the heat within the steel reinforement. The results of heating the 43-mm-long steel reinforement using the high-frequeny indution heating 651

6 Heating 誘導コイル Indution Coil Steel Reinforement 誘導コイル絶縁体 Insulator 鉄筋 Steel Reinforement 鉄筋 12mm 12mm 15mm d 15mm Height Control 高さ調節 l 15 D6 D1 D19 D25 43 l D1 D19 D25 Temperature ( ) Figure 4. Experimental method of single steel reinforement heating using high-frequeny indution heating method Heating time (se) D6-6-1 D1-6-1 D D D Figure 5. Temperature rise harateristis of steel reinforement depending on high-frequeny indution heating (measured at 15 mm-enter). 5 kw-1 mm; 6 kw-3 mm. Note: D--: D (reinfored type)-output (kw)-heating distane (mm). method are shown in Figure 6. Heating with an output of 5 kw showed temperature rise harateristis similar to that of the 15-mm-long steel reinforement. This may be beause little heat ondution loss ours depending on the length of steel reinforement and beause seletive heating is possible depending on the heating loation Temperature Distribution Charateristis of Single Steel Reinforement Depending on High-Frequeny Indution Heating The steel reinforement heating proess using the indution heater an be problemati owing to unneessary heating, lak of heating, and onrete weakening depending on the temperature rise. This study analyzes the temperature distribution of steel reinforement at the indution heating onditions of 5 kw and 6 kw using infrared radiation temperature measurement at 1 mm, where the highest temperature rise ourred; the results Temperature ( ) D6-6-3 D D Heating time (se) 3 33 D1-6-3 D

7 Temperature( ) D1-5-1 D D D Temperature( ) D1-5-4 D D D Heating time(se) Heating time(se) Figure 6. Temperature rise harateristis of steel reinforement depending on high frequeny indution heating (measured at 45 mm-enter). 5 kw-1 mm; 5 kw-3 mm. are shown in Figure 7. The horizontal axis of the figure is 15 mm, i.e., the length of the speimen, but there are some errors in the range of temperatures owing to the radiant heat when measuring using the infrared ray temperature. The horizontal axis is 16 ± 5 mm on average, and the error of 1 ± 5 mm due to radiant heat does not have a large effet on the heating phenomenon at the enter or at the end. Most of the speimens demonstrated that heating was more onentrated at the entral part ompared to at the end. The 12-mm-diameter steel reinforement that was out of the heating oil showed a differene of 15 C - 45 C ompared to the entral part. As the diameter of the heating oil was 12 mm in the experiment wherein the 43-mm steel reinforement is heated at 5 kw, the point was measured with a distane of 3 mm from the enter of the oil diameter toward the longitudinal diretion of the steel reinforement; the result is shown in Figure 8. There was not a large differene in temperature within the oil diameter, but the inside of the oil showed a temperature differene of 1 C or more when the external oil diameter was 3 mm or above. Most of the steel reinforement showed a temperature rise by thermal ondutivity of steel reinforement outside of the magneti field with an external oil diameter of 6 mm or above, whih suggested that this was a loalized heating phenomenon. A high-temperature phenomenon on the surfae of the steel reinforement was identified at 4 C - 5 C in many ases. This high-temperature phenomenon was found only inside the heating oil, and the high-temperature phenomenon due to thermal ondution did not appear, whih suggested that there was a loalized heating phenomenon due to seletive heating. 4. Temperature Charateristis of Cross-Steel Reinforement Depending on High-Frequeny Indution Heating 4.1. Experimental Overview This study arries out an experiment to analyze the temperature rise harateristis and temperature distribution depending on high-frequeny indution heating using SD345 steel reinforement. This study identifies the temperature rise harateristis that an be found when using the single steel reinforement and the hanges in temperature distribution with ross-arrangement similar to that in an atual struture. If the steel reinforement rosses, there may be a differene in heat harateristis aused by heating and ondution aused by resistane depending on the harateristis of the magneti field. In addition, as the surfae faing the oil inreases and there is a large differene in heat transfer rate depending on the distane from the major steel reinforement arranged at the bottom and the resistane area, it is expeted that there will be a differene in temperature rising slope and the positioning of the heating oil. This study identifies temperature rise harateristis, temperature gradient, and temperature distribution depending on the arrangement of steel reinforement and distane heating alulated by thikness of overing Experimental Method To identify the appropriate quantity of output or temperature distribution of steel reinforement in the ross-steel reinforement heating experiment, this study uses steel reinforement of D1, D19, D25, and D32 in the ase of 653

8 Temperature ( ) s 6s 18s 3s 3s 12s 24s 36s Figure 7. Temperature distribution of steel reinforement depending on high frequeny indution heating (5 kw-15 mm). 5 kw-d19-1 mm; 5 kw-d25-1 mm. Temperature ( ) s 6s 18s 3s 3s 12s 24s 36s Temperature( ) Heating time(se) a b d e Temperature( ) Heating time(se) a b d e Figure 8. Temperature distribution of steel reinforement depending on high frequeny indution heating (5 kw-45 mm). 5 kw-d19-1 mm; 5 kw-d25-1 mm. Note: a: enter of steel reinforement, b,, d, e: toward the end from the enter of steel reinforement 3, 6, 9, 12 mm. SD345. To perform the experiment in the same onditions as those of the reinfored onrete members, this study uts the length to 355 mm before use. This study assumes the steel reinforement of D19, D25, and D32 as major steel reinforements and arries out an experiment by ross-arranging the D1 steel reinforement at the bottom. As shown in Figure 9, this study plaes three steel reinforements at intervals of 6 mm from surfae to surfae before heating. To selet the optimal heating oil position, this study attempts a method to distribute the heating oil at the ross point of steel reinforement (enter heating) and also a method to distribute the heating oil between major steel reinforements (side heating); the temperature harateristis depending on type and distane of steel reinforement are then evaluated. The temperature is measured at five positions at a distane of 3 mm from the enter of the upper and lower steel reinforement using a heat-resistant amera, similar to the single steel reinforement heating experiment Temperature Rise Charateristis of Cross-Steel Reinforement Depending on High-Frequeny Indution Heating With a high-frequeny output of 5 kw, the initial temperature rise urve showed the same tendeny as that of the single steel reinforement, with a sharp slope. However, it reahed thermal equilibrium rapidly, showing the temperature redution of up to 1 C ompared to the single steel reinforement. If the distane to the heating soure was loser, there was no large temperature differene in the upper steel reinforement of D1, but the upper and lower steel reinforement showed a temperature differene between 8 C and 18 C when the heating distane was 4 mm or above. At the shortest distane, there ours a heating phenomenon wherein a magneti field is formed that reahes the lower steel reinforement; at larger distanes, a magneti field is formed around the upper steel reinforement before it reahes the lower steel reinforement and the lower steel reinforement is heated by ondution (as shown in Figure 1). 654

9 誘導コイル Heating 誘導コイル Indution Coil Heating Indution Coil 絶縁体 Insulator 鉄筋 Steel Reinforement 鉄筋 12mm 6mm 355mm d 6mm 355mm Height 高さ調節 Control e d b e d b Center 交差点 f a b a D1 D19 D25 D32 l Center 加熱 Heating Side 加熱 Heating Figure 9. Experimental method of heating the ross-steel reinforement using high-frequeny indution heating. Temperature( ) Heating time(se) a 5 b 4 3 d 2 e 1 f Temperature( ) Heating time(se) a b d e * Note: a: D--: D reinfored type type of lower steel reinforement heating distane (mm). Figure 1. Temperature rise harateristis of steel reinforement depending on high-frequeny indution heating (Center). Measurement of D mm from the upper side; Measurement of D mm from the lower side. The temperature distribution shows almost the same tendeny as the single steel reinforement, but if the diameter of the heating oil is 12 mm, the temperature differential between steel reinforement inside the diameter and steel reinforement outside the diameter shows a large temperature differential in the upper steel reinforement when the heating range is between 5 C and 2 C. This result an help identify the possibility of seletive heating depending on the area of the magneti field (as shown in Figure 11). When the heating oil was plaed between major steel reinforements, the temperature rise harateristis showed a maximum differene of 1 C. When the heating oil was plaed at the point of intersetion and heated, eah one of the upper and lower steel reinforements loated at the enter of the oil diameter showed the same heating tendeny. When the heating oil was plaed between the major steel reinforements, the heating effiieny dereased slightly, but the area of heating expanded when two upper steel reinforements and two lower steel reinforements in the range of the magneti field were heated at the same time, whih led to an inrease in the width of the heating range. This seems to be attributable to the impat of oupling effiieny on the steel reinforement and heating oil. As shown in Equation (8) and Equation (9), the heating oil is basially a 655

10 resistor (indutane) and thus produes heat depending on [material length diameter (area of surfae) with the urrent that flows in the oil * oil resistane]. In addition, the intensity of the magneti fore is inversely proportional to 2-3 square of distane and proportional to the urrent that ours in the oil and oil differential (relative hanges in two oils). Therefore, if the oupling effiieny of steel reinforement and oil is bad, a high urrent is required. There are ondensers and transformers within the onditioning unit (iruit), and they beome a resistane [18] [19]. mm 1 2 F = G (8) r = ; G m = mass; r = distane; F = output m kg s output ( intensity of magneti field ) = A( urrent) T ( oil differential) (9) In other words, as in Figure 12, whih shows the oupling of steel reinforement and oil, in, where the distane from the heating oil is the same as the distane between the oils to the surfae of the steel reinforement, two steel reinforements are inluded within similar magneti fields and thus resistane heat ours up to a temperature like (). Therefore, if the voltage is the same, loss within the iruit inreases and the temperature of the heated objet dereases with inreasing urrent (or raised voltage). 5. Deonstrution Assessment of Reinfored Conrete Using Hitting Method 5.1. Experimental Overview The purpose of this experiment is to evaluate the dynami dismantlement of reinfored onrete members weakened by high-frequeny indution heating. As there are no previous studies on the methods for evaluating the dismantlement of onrete members quantitatively, in most ases, qualitative evaluations suh as diffiult to dismantle are defined without evaluating the time or energy required for dismantling. Therefore, the data is not reliable as reprodutive data in reviewing the expenses for dismantling or environmental load [2]. This study measures the time and energy required for unit dismantlement and makes a quantitative evaluation of dynami dismantlement of reinfored onrete members weakened by high-frequeny indution heating Experimental Method The reinfored onrete members weakened by high-frequeny indution heating were separated to the extent that steel reinforement utting an be done in the field. By installing 3-axis aeleration sensors in the hammer, the dismantling tool, this study measures the dismantling loation and the time onsumed by eah experimental group. To alulate the time and energy taken for dismantling for single reinfored onrete speimens, the aeleration and diretion of dismantling were measured until the steel reinforement ould be exposed by hitting a heated speimen that was heated in the longitudinal diretion ontinuously. To alulate the time and energy taken for dismantling in the ase of ross-steel reinforement, the aeleration and diretion of dismantling were measured until the steel reinforement ould be exposed by hitting a heated speimen that was heated by indution heating of both the enter and side Deonstrution Assessment of Single Reinfored Conrete The separating experiment results that ompare the speimen with 3 mm steel reinforement overing depth (D19), whih requires the least eletriity for the separation, before and after heating, are represented in Figure 13 and Figure 14. In most of the speimens, the destrution power showed a reduing tendeny with inreasing diameter of steel reinforement, and the power required for destrution dereased with dereasing distane from the indution heating oil. In ase of the speimen using D1, with the least heating effiieny, the power depending on the indution heating was the smallest. However, it showed a tendeny that it redued more greatly at 3 mm a smaller heating distane than at 4 mm or 5 mm. When the heating distane was smaller, the temperature of 656

11 Temperature( ) Heating time(se) a b Figure 11. Temperature rise harateristis of steel reinforement depending on high-frequeny indution heating (Side). Pith () Pith Coil Reinforing Bar Eddy Current (d) (e) Figure 12. Improved oupling effiieny in steel reinforement and heating oil. steel reinforement rose rapidly; when the diameter of steel reinforement was small, thermal equilibrium was reahed immediately after heating and the heat ondution veloity for onrete inreased and then weakened immediately. This is why the breaking stress was smaller than it was for other speimens with relatively thiker overing depths. In ase of D19 and D25, with higher heating effiieny, a redution in destrution stress with heating distane was evident. In the ase of D19, the reduing rate at overing depths of 5 mm and 3 mm had about a 69% differene; for D25, there was about a 71% differene. For D32, with the smallest destrution stress, there was about an 83% reduing rate ompared to the standard speimen. There may be some errors in the destrution stress aused by the inreased overing thikness, but D19 showed about a 77% reduing rate, ompared to the standard speimen Deonstrution Assessment of Cross-Reinfored Conrete The speimen that was heated at the enter showed a dereased tendeny for destrution stress ompared to the speimen that was heated at the side. With a overing thikness of 3 mm, the enter-heated sample showed about a 39% reduing rate and the side-heated sample showed about a 31% reduing rate, whih suggested that there was an 8% differene. Compared to the enter heating, rak propagation showed a high effiieny when heating the side, but the enter heating showed a high heating effiieny in the rak width and internal temperature rise ratio. Therefore, enter heating may be influential on the stress required to separate steel reinforement from onrete (as shown in Figure 15 and Figure 16). The overall tendeny before and after high-frequeny indution heating inreased aording to the overing thikness. The rak width aused by the expansion pressure depending on heating is more influential to the steel reinforement than is hemial weakening, whih depends on thermal ondution. 6. Conlusions This study arries out an experiment to separate steel reinforement from onrete as ompletely as possible through indiret heating using high-frequeny indution heating, espeially of the steel reinforement inside the 657

12 aumulated unitenergy(j/kg) Ax(m/(se^2)) Ay(m/(se^2)) Az(m/(se^2)) aumulated unitenergy(j/kg) Ax(m/(se^2)) Ay(m/(se^2)) Az(m/(se^2)) time(se) time(se) D19-3-op D1-3 D1-4 D1-5 D19-3 D19-4 D19-5 D25-3 D25-4 The Stress for Demolition(N) D25-5 D32-3 D32-4 D32-5 () Figure 13. Experiment result of deonstrution of single reinfored onrete member after high frequeny indution heating. Speimen before heating (D19-3 mm); Speimen after heating (D19-3 mm); () Resolved stress of reinfored onrete member. Figure 14. Experiment result of omplete deonstrution of single reinfored onrete member after heating. reinfored onrete, and the findings are as follows: 1) The frequeny with the maximum output determines the depth of penetration in the indution heating. If the output inreases enough to heat the steel reinforement that is far from the heating oil, urrent density and intensity of magneti field inrease in general, but the depth of penetration dereases. Thus, it is neessary to take into aount the appropriate output at a ertain distane. As the appropriate output does not show any large differene in temperature rise with time at a distane of less than 4 mm, the output of 5 kw or above leads to heat loss at temperatures higher than the Curie point and there is a problem in power dissipation. 658

13 aumulated unitenergy(j/kg) 5 Ax(m/(se^2)) Ay(m/(se^2)) Az(m/(se^2)) time(se) aumulated unitenergy(j/kg) 1 Ax(m/(se^2)) 8 Ay(m/(se^2)) 6 Az(m/(se^2)) time(se) The stress for Demolition(N) D1-D19-3-C D1-D19-3-S D1-D19-4-C D1-D19-4-S D1-D19-5-C D1-D19-5-S D1-D19-3-op D1-D19-4-op D1-D19-5-op () Figure 15. Experiment result of destruting the ross-reinfored onrete member after high frequeny indution heating. Speimen before heating (D mm) the enter; Speimen after heating (D mm) the enter; () Resolved stress of reinfored onrete member. Figure 16. Experiment result of destruting the ross-reinfored onrete member after heating. 2) Using the high-frequeny indution heating method, the surfae of steel reinforement an be heated up to 3 C, at whih the onrete-weakening temperature is the most effetive. As the heating range is losely related to the diameter of the heating oil, seletive heating up to 3 mm in the horizontal diretion is possible based on the heating oil. With ross-arranged steel reinforement, a overing thikness of 4 mm is possible for an effetive heating, and a overing thikness of 5 mm or above is possible for an effetive heating by thermal ondution through the upper steel reinforement. 659

14 3) When high-frequeny indution heating is applied to the struture in the field, steel reinforement an be ut by exposing the steel reinforement using the hitting method after weakening the onrete by the ourrene of raks aused by the heated expansion pressure and thermal ondution. Thus, effetive work is possible owing to weakening aused by rapid heating of the exposed steel reinforement. The high-frequeny indution heating tehnology proposed in this study may be appliable to the field of dismantling existing high-rise buildings, fields where workers annot use heavy equipment, and fields that are sensitive to pollutants suh as noise and dust. Partiularly in the field of dismantling single strutures with loalized dismantling, for example, repair or reinforement, highly effiient dismantling is expeted to be possible. Aknowledgements This work was supported by the GRRC program of Gyeonggi provine. [(GRRC HANKYONG 211-B5), Carbon Neutral Wall and Floor Elements for Smart Distribution Center]. Referenes [1] World Eonomi Forum (214) The Global Energy Arhiteture Performane Index Report 214. Cologny. [2] Robert, W. and Messler, J.R. (24) Joining of Materials and Strutures: From Pragmati Proess to Enabling Tehnology. Elsevier In., Amsterdam. [3] Gatta, D. (23) Generation and Management of Constrution and Demolition Waste in Greee An Existing Challenge. Resoures, Conservation and Reyling, 4, [4] Mizutani, R. and Yoshikai, S. (211) A New Demolition Method for Tall Building. Kajima Cut & Take down Method. CTBUH Journal, 5. [5] Sealey, B.J., Phillips, P.S. and Hill, G.J. (211) Waste Management Issues for the UK Ready-Mixed Conrete Industry. Resoures. Conservation and Reyling, 32, [6] Uttam, K. and Balfors, B. (214) 9 Green Publi Prourement (GPP) of Constrution and Building Materials. Eo- Effiient Constrution and Building Materials, Life Cyle Assessment (LCA), Eo-Labelling and Case Studies, [7] Sthiannopkao, S. and Wong, M.H. (213) Handling E-Waste in Developed and Developing Countries: Initiatives, Praties, and Consequenes. Siene of The Total Environment, , [8] Lin, F. (212) The Development Path of Japanese Green Arhiteture under Energy Poliy Taking Misawa Home as an Example. Energy Proedia, 14, [9] Li, C.E., Burke, N., Gerdes, K. and Patel, J. (213) The Undiluted, Non-Catalyti Partial Oxidation of Methane in a Flow Tube Reator An Experimental Study Using Indiret Indution Heating. Fuel, 19, [1] Panão, M.R.O., Correia, A.M. and Moreira, A.L.N. (212) High-Power Eletronis Thermal Management with Intermittent Multijet Sprays. Applied Thermal Engineering, 37, [11] Wrzuszzak, M. and Wrzuszzak, J. (25) Eddy Current Flaw Detetion with Neural Network Appliations. Measurement, 38, [12] Myrhaug, D. and Holmedal, L.E. (214) Wave-Indued Current for Long-Crested and Short-Crested Random Waves. Oean Engineering, 81, [13] Xiao, C.-L. and Huang, H.-X. (214) Optimal Design of Heating System for Rapid Thermal Cyling Mold Using Partile Swarm Optimization and Finite Element Method. Applied Thermal Engineering, 64, [14] Postahini, M. and Brohini, M. (214) A Wave-by-Wave Analysis for the Evaluation of the Breaking-Wave Celerity. Applied Oean Researh, 46, [15] [16] Hukushima, Y. (29) Experimental High Frequeny Indution Heating Collision Instrution Manual (IMC-ADH-52). Imes Corporation, Japan. [17] Sadeghipour, K., Dopkin, J.A. and Li, K. (1996) A Computer-Aided Finite Element/Experimental Analysis of Indution Heating Proess of Steel. Computers in Industry, 28, [18] Lee, K.S. and Hwang, B. (214) An Approah to Triangular Indution Heating in Final Preision Forming of Thik 66

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