ANALYSIS OF CO 2 EMISSIONS DEPENDING ON THE USE OF HIGH-STRENGTH RE-BAR IN BUILDINGS

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 9, September 2018, pp , Article ID: IJCIET_09_09_138 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed ANALYSIS OF CO 2 EMISSIONS DEPENDING ON THE USE OF HIGH-STRENGTH RE-BAR IN BUILDINGS Jongsik Lee Professor, Department of Architectural Engineering, Songwon University, Gwangju, 61756, Republic of Korea ABSTRACT High-strength re-bars have been developed and used due to the large size of highrise buildings. It is known that the use of high-strength re-bars can reduce the amount of CO2 emissions as well as secure economic efficiency by reducing the amount of rebars. However, there is a lack of research to obtain objective data on the reduction of high-strength re-bars and the reduction of CO2 emissions. In this study, the threestrength re-bars of SD400, SD500 and SD600 were designed in a residential complex building, and the quantity of re-bars and CO2 emissions were compared and analyzed. The total quantity of re-bars in study model 1 with SD400 was tons and the CO2 emission was 11,531,624.9 kg-co2 / ton. The total quantity of re-bars in study model 2 with SD500 was tons and the CO2 emission was 10,712,351.7 kg-co2 / ton. The total quantity of re-bars in study model 3 with SD600 was tons and the CO2 emission was 10,050,362.0 kg-co2 / ton. Based on study model 1, the rate of increase in the quantity of re-bars of D16~D32 with a small CO2 emission per unit weight was analyzed as % for study model 2 and % for study model 3. Therefore, the increase in the use of D16~D32, which has a small CO2 emission, has been analyzed as a main factor in reducing CO2 emissions. However, in study models 2 and 3, D10, which has the highest CO2 emission per ton, was used more than study model 1. Therefore, in order to increase CO2 reduction effect by using high-strength re-bar, it is necessary to reduce the amount of D10 with high CO2 emissions per unit weight and to increase the amount of D16~D32 with low CO2 emissions per unit weight. Key words: Building, High Strength Bar, High-strength Re-bar Quantity, Carbon Dioxide Cite this Article: Jongsik Lee, Analysis of CO 2 Emissions Depending on the Use of High-Strength Re-Bar in Buildings. International Journal of Civil Engineering and Technology, 9(9), 2018, pp editor@iaeme.com

2 Jongsik Lee 1. INTRODUCTION In Korea, structural materials of high quality, high performance and high strength are required due to the large size of high-rise reinforced concrete buildings. Accordingly, there is an increasing demand for high-strength re-bars that serve as the framework for reinforced concrete buildings. In Korea, high strength materials with a specified concrete strength of 100 MPa or more are used for concrete and re-bars with a yield strength of 400 MPa or less are conventionally used. However, as the relevant law was revised in 2012, a high strength bar with a yield strength of 550~600 MPa is used (Lee, J.L., 2013) [1]. The strength of SD600 is improved by 50% compared to SD400 and the quantity of re-bars per 3.3m2 is also known to be reduced by 20% compared to SD400 when using SD600. This is expected to save 840,000 won per unit of apartment houses, saving 50.4 billion won per year on the basis of 60,000 units. In addition, the carbon dioxide (hereinafter, CO 2 ) generated in the production of 1 ton of reinforcing steel is 0.4 ton and if the existing SD400 is changed to SD500 or SD600, the CO 2 reduction effect of 32,000 tons can be expected when constructing 400,000 units a year (Korea Ministry of Trade, Industry & Energy (2015) [2]). However, the high-strength re-bars have recently been introduced in Korea and there is insufficient data to analyze the decrease in re-bars and the decrease in CO 2 emissions when using SD500 and SD600. This study compared the quantity of re-bars and CO 2 emissions by applying the SD400, SD500 and SD600 re-bars to residential complex buildings in order to analyze the reduction of CO 2 emissions when using high-strength re-bars. The objective of this study is to provide objective data that can be used for decision making in regards to economic and environmental aspects when high-strength re-bars are applied. 2. SCOPE AND METHOD OF STUDY This study analyzed the quantity of re-bars and the CO 2 emissions from the residential complex building when applying re-bars with three different strength levels; SD400, SD500 and SD600. The quantity of re-bars included development and splice reinforcement. Since the purpose of this study is to analyze the quantity of re-bars and CO 2 emissions as the strength of the re-bar changes, the premium proportion of the re-bar was not considered. This study was conducted by the following methods and procedures. 1) The concept and application of the high-strength re-bars were examined. 2) The previous study related to high-strength re-bars was considered and the difference of this study was suggested. 3) An outline of the analyzed building and a study model for each analysis condition were presented. 4) The quantity of re-bars and CO 2 emissions for each study model were calculated and compared. 5) The results of the study are summarized and future work is presented. 3. LITERATURE REVIEW Studies related to high-strength re-bars have been conducted since the mid-1990s. Lee, J. H. (1994) [3] set the quantity of re-bars to a variable in the beam which was designed with the concrete compressive strength of 28MPa, 35MPa and 42MPa, and the yield strength of 300MPa, 400MPa and 500MPa. Then, he compared the values calculated using the ductility index. Kwon, S. B. and Yoon, Y. S. (2002) [4] presented optimal strength combinations of beams by setting compressive strength of concrete and tensile strength of re-bars to a variable. Megget, L. M. et al. (2003) [5] demonstrated through a series of experiments that highstrength re-bars can cause premature failure of beam-column connections due to earthquakes editor@iaeme.com

3 Analysis of CO 2 Emissions Depending on the Use of High-Strength Re-Bar in Buildings Oh, B. H. et al. (2005) [6] proved through various experiments that it is possible to secure the necessary seismic performance even if the re-bar usage is reduced because when the highstrength re-bar is applied, the displacement ductility decreases but the limitation displacement is the same Kim, J. Y., Kim, G. H. (2008) [7] constructed a model for economic evaluation of SD500 re-bars and conducted case studies with a way of inputting the most used conditions in the field. The effectiveness of the study model was verified through case studies and the economic feasibility of the splice method was analyzed. Jang, I. Y. et al. (2008) [8] analyzed compressive strength, tension reinforcement ratio, quantity of web reinforcement and shear span-depth ratio aimed at concrete beams with compressive strengths of 40MPa, 60MPa and 70MPa. Arslan, G. and Cihanli, E. (2010) [9] presented a prediction formula of the ductility index depending on the compressive strength of concrete, the yield strength of re-bar and the tension reinforcement ratio by analyzing the ductility index flexural members in the beam with the compressive strengths of 50~110MPa and the yield strengths of 220MPa, 420MPa and 530MPa. Bai, Z. Z. and Au, F. T. K. (2011) [10] analyzed the effect of compressive strength and tension reinforcement ratio of concrete on the ductility index through an analytical study of reinforced concrete beams with compressive strength of 30~90MPa. Thus, various studies have been conducted focusing on the physical properties of high-strength rebars. There is a lack of research into the changes in CO 2 emissions depending on the use of high-strength re-bars. However, it is known that the use of high-strength re-bars reduces the quantity of re-bars and reduces costs. This study is different in that it is an empirical analysis of changes in the quantity of re-bars and changes in CO 2 emissions when using re-bars with three strength and re-bars with eight kinds of diameter. 4. SETTING ANALYSIS CONDITIONS 4.1. Outline of Study Subjects The analysis target is a residential complex building with 4 floors underground and 39 floors above ground. Composition by usage is studio 41.1%, apartment 49.2% and neighborhood living facility 9.7%. The strength of concrete was designed to be 30~40MPa for vertical members and 27~30MPa for horizontal members Composition of Study Model The study model was composed by designing the same structures as the re-bars of SD400, SD500 and SD600, respectively, as shown in Table 1. Then, the strength of re-bars, the quantity of re-bars on the diameter and the amount of CO 2 emissions was calculated. The quantity of re-bars was calculated by summing pure re-bar length, development length and splice length. Development length and splice length were estimated based on the concrete structure design standard in Korea (2012). Also, since the compressive strength of the concrete was more than 27Mpa, the regulations to increase the lap splice of the compressive reinforcement by one-third was not applied in structures less than 21MPa editor@iaeme.com

4 Jongsik Lee Figure 1. Structure plan of a typical floor Table 1 Study Model D10 D13 D16 D19 D22 D25 D29 D32 Study Model I SD400 SD400 SD400 SD400 SD400 SD400 SD400 SD400 Study Model 2 SD500 SD500 SD500 SD500 SD500 SD500 SD500 SD500 Study Model 3 SD600 SD600 SD600 SD600 SD600 SD600 SD600 SD600 There are two methods for obtaining CO 2 emissions data for re-bars: a process based on LCA and an input-output based on LCA. The process based LCA is a method to directly obtain CO 2 emissions from the production process through direct investigation and measurement of the production process of re-bars (Bilec et al. 2006) [11]. Process based LCA requires detailed data from government agencies or producers. Therefore, there is a limit to securing CO 2 emissions data for various re-bars (Bilec et al. 2006, Sharrard et al. 2007) [11, 12]. Input-output LCA is based on an industry association table showing interrelationships among industries. Input-output LCA is an analytical method to quantitatively identify inputs or outputs in the process of producing goods or services (Chris et al. 1998) [13]. Input-output LCA is a very effective way to quantify the CO2 emissions information of re-bars (Lee, K. H. and Yang, J. H. 2009) [14]. Emphasis has been placed on the need for detailed levels of CO 2 emissions data for building materials to assess accurate CO 2 emissions for buildings. CO 2 emissions data for re-bar and H-beam were presented in detail by strength and specification using the input-output LCA. As a representative study, Hong, T.H. et al. (2012) [15] presented different amounts of CO 2 emissions according to the strength and specification of the re-bars as shown in Table 2. The purpose of this study is to analyze CO 2 emissions by re editor@iaeme.com

5 Analysis of CO 2 Emissions Depending on the Use of High-Strength Re-Bar in Buildings bar strength. Thus, partial data of energy consumption and CO 2 emissions of re-bars (Table 3) Hong, T.H. et al. (2012) [15] presented was used to calculate CO 2 emissions. Table 2 Partial data of energy consumption and CO2 emissions of re-bars Strength Specification Energy consumption per ton of rebar CO 2 emissions per ton of re- (Diameter) (toe/ton) bar (kg-co 2 /ton) SD400 D D D16~ SD500 D D D16~ SD600 D D D16~ (Hong, T.H. et al. 2012) 5. DATA ANALYSIS 5.1. Quantity of Re-bars Analysis by Study Model Study Model 1 Quantity of re-bars by element of the study model 1 using SD400 was analyzed. The quantity of re-bars by element is 1,239.1 tons for columns, tons for foundations, tons for walls, tons for girders and 2,087.0 tons for slabs. The quantity of re-bars by diameter is D10: tons, D13: 1,382.4 tons, D16: tons, D19: tons, D22: 51.1 tons, D25: tons, D29: 1,220.4 tons and D32: tons. The total quantity of re-bars in study model 1 was 4,747.3 tons Study Model 2 When SD500 was applied, it was observed that it takes a total of tons, with tons for columns, tons for foundations, tons for walls, tons for girders and tons for slabs. The quantity of re-bars by diameter was D10: tons, D13: tons, D16: tons, D19: tons, D22: tons, D25: tons, D29: tons and D32: 13.2 tons. The total quantity of re-bars in study model 2 was tons. The rate of change in the quantity of re-bars in study model 1 was -11.6% Study Model 3 When the SD600 was applied, it was observed that it takes a total of tons, with tons for columns, tons for foundations, tons for walls, tons for girders and tons for slabs. The quantity of re-bars by diameter was D10: tons, D13: tons, D16: tons, D19: tons, D22: tons, D25: tons, D29: 64.5 tons and D32: 14.6 tons. The total quantity of re-bars in study model 3 was tons. The rate of change in quantity of re-bars was -19.8% when compared to study model 1 and -9.2% when compared to study model 2. Table 3 Quantity of re-bars by diameter for study models 1, 2 and 3 (ton) Study Model 1 Study Model 2 Study Model 3 D D13 1, , ,124.7 D D D editor@iaeme.com

6 Jongsik Lee D , D29 1, D Total Analysis of CO 2 Emissions by Study Model CO 2 emissions by study model were calculated using the quantity of re-bars by study model, the strengths of re-bars in Table 2 and CO 2 emissions by the diameter of re-bars Study Model 1 The quantity of re-bars by diameter of study model 1 using SD400 re-bars was D10: tons, D13: 1,382.4 tons, D16: tons, D19: tons, D22: 51.1 tons, D25: tons, D29: 1,220.4 tons and D32: tons. This was multiplied by the CO 2 emissions per ton of SD400 re-bars in Table 3 to calculate CO 2 emissions by diameter. As shown in Table 4, CO 2 emissions by diameter of re-bars were D10: 887,337.0 kg-co 2, D13: 2,975,487.4 kg-co 2, D16: 2,063,006.3 kg-co 2, D19: 461,755.0 kg-co 2, D22: 249,401.0 kg-co 2, D25: 2,848,982.6 kg-co 2, D29: 667,571.4 kg-co 2 and D32: 31,962.1 kg-co 2. The total CO 2 emission of study model 1 was 10,185,502.9 kg-co 2. Strength SD400 Table 4 CO 2 Emissions of study model 1 Specification Quantity of re-bars CO 2 emissions per ton of Total CO 2 emission (Diameter) (ton) re-bar (kg-co 2 /ton) (kg-co 2 /ton) D ,797.3 D13 1, ,364,673.9 D ,372,941.5 D ,075.6 D ,732.0 D ,461.6 D29 1, ,955,038.6 D ,904.4 Total 4, ,531, Study Model 2 The quantity of re-bars by diameter for study model 2 using SD500 re-bars was D10: tons, D13: tons, D16: tons, D19: tons, D22: tons, D25: tons, D29: tons and D32: 13.2 tons. This is multiplied by the CO 2 emissions per ton of SD500 re-bars in Table 3 to calculate CO 2 emissions by diameter. As shown in Table 5, CO 2 emissions by diameter of re-bars are D10: 932,379.5 kg-co 2, D13: 3,129,127.1 kg-co 2, D16: 2,170,082.7 kg-co 2, D19: 485,721.6 kg-co 2, D22: 262,345.7 kg-co 2, D25: 2,996,853.7 kg- CO 2, D29: 702,220.4 kg-co 2 and D32: 33,621.0 kg-co 2. The total CO 2 emission of study model 2 was 10,712,351.7 kg-co 2. The rate of change in CO 2 emissions was -7.1% compared to study model 1. Strength SD500 Table 5 CO 2 Emissions of study model 2 Specification (Diameter) Quantity of re-bars (ton) CO 2 emissions per ton of re-bar (kg-co 2 /ton) Total CO 2 emission (kg-co 2 /ton) D , ,379.5 D , ,129,127.1 D , ,170,082.7 D , ,721.6 D , , editor@iaeme.com

7 Analysis of CO 2 Emissions Depending on the Use of High-Strength Re-Bar in Buildings D , ,996,853.7 D , ,220.4 D , ,621.0 Total ,712, Study Model 3 The quantity of re-bars by diameter of study model 3 using SD600 rebars was D10: tons, D13: tons, D16: tons, D19: tons, D22: tons, D25 : tons, D29: 64.5 tons and D32: 14.6 tons. This is multiplied by the CO2 emissions per ton of SD600 re-bar in Table 3 to calculate CO 2 emissions by diameter. As shown in Table 6, CO 2 emissions by diameter of re-bars were D10: 966,704.3 kg-co 2, D13: 2,973,029.2 kg-co 2, D16: 2,016,531.1 kg-co 2, D19: 416,986.5 kg-co 2, D22: 2,401,947.7 kg-co 2, D25: 1,067,064.6 kg-co 2, D29: 169,688.5 kg-co 2 and D32: 38,410.1 kg-co 2. The total CO 2 emissions for study model 3 were 10,050,362.0 kg-co 2. The rate of change in CO 2 emissions was -12.7% compared to study model 1 and -6.86% compared to study model 2. Table 7 shows CO 2 emissions by diameter of re-bars of study models 1, 2 and 3. Strength SD600 Table 6 CO 2 Emissions for study model 3 Specification (Diameter) Quantity of re-bars (ton) CO 2 emissions per ton of re-bar (kg-co2/ton) Total CO 2 emission (kg-co 2 /ton) D , ,704.3 D , ,973,029.2 D , ,016,531.1 D , ,986.5 D , ,401,947.7 D , ,067,064.6 D , ,688.5 D , ,410.1 Total ,050,362.0 Table 7 CO 2 Emissions by diameter of re-bars in study models 1, 2 and 3 (kg-co 2 / ton) Study Model 1 Study Model 2 Study Model 3 D10 865, , ,704.3 D13 3,364, ,129, ,973,029.2 D16 2,372, ,170, ,016,531.1 D19 498, , ,986.5 D22 123, , ,401,947.7 D25 632, ,996, ,067,064.6 D29 2,955, , ,688.5 D32 718, , ,410.1 Total 11,531, ,712, ,050, CONCLUSIONS This study analyzed the changes in CO 2 emissions due to changes in the strength of re-bars. The three-strength re-bars of SD400, SD500 and SD600 were designed in a residential complex building, and the quantity of re-bars and CO 2 emissions were compared and analyzed. The rage of change in the quantity of re-bars of D16 ~ D32 with small CO 2 emissions per unit weight was analyzed as % for study model 2 and % for study model 3. The increase in the quantity of re-bars of D16 ~ D32 with small CO 2 emissions was analyzed as the main cause of CO 2 reduction. However, as shown in Table 9, in study models 2 and 3, D10, which has the largest CO 2 emission per ton, was used more than study model editor@iaeme.com

8 Jongsik Lee Table 8 Rate change data of quantity of re-bars and CO 2 emission by diameter Study Model 1 Rate of change of Study Rate of change of Study Model 2 (%) Model 3 (%) Reference value Quantity of CO 2 Quantity of CO 2 re-bars emissions re-bars emissions D D D D D D D D As shown in Table 3, CO 2 emissions per ton of re-bars increased as diameter of re-bars decreased, and increased as re-bar strength increased. Therefore, reducing the amount of D10 with a large amount of CO 2 emissions per unit weight and increasing the amount of D16~D32 with a small amount of CO 2 emissions per unit weight was considered to be a way to reduce CO 2 emissions. In order to reduce CO 2 emissions, efforts should be made to reduce the quantities of re-bars of D10 and D13, which have large amounts of CO 2 emissions per unit weight in SD400, SD500 and SD600. ACKNOWLEDGEMENTS This study was supported by research fund from Songwon University REFERENCES [1] Lee, J. L., Evaluation on Moment-Curvature Relations and Curvature Ductility Factor of Reinforced Concrete Beams with High Strength Materials, Journal of the Korea Concrete Institute, 25(3), 2013, pp [2] Ministry of Trade, Industry & Energy, 99&file_seq_n=1, [3] Lee, J. H., Analytical Study on Ductility Index of Reinforced Concrete Flexural Members, Journal of The Korean Society of Civil Engineers, 14(3), 1994, pp [4] Kwon, S. B. and Yoon, Y.S., Flexural behavior of RC beams using High-strength reinforcement for ductility assesment, Journal of Korean Society of Hazard Mitigation, 2(1), 2002, pp [5] Megget, L. M., Fenwick, R. C. and Amso, N., Seismic performance of internal beamcolumn joints with 500 grade reinforcement, Pacific Conference on Earthquake Engineering, Paper No. 100, 2003, pp [6] Oh, B. H., Cho, K. H. and Park, D. K., An Experimental Study on the Seismic Behavior of Solid RC Piers Using High Strength Concrete and High Strength Re-bars, Journal of the Korea Concrete Institute, 17(1), 2005, pp editor@iaeme.com

9 Analysis of CO 2 Emissions Depending on the Use of High-Strength Re-Bar in Buildings [7] Kim, J. Y. and Kim, G. H., A Study on Economic Evaluation Method of Coupler Splice for High Strength(SD500) Reinforcement, Korean Journal of Construction Engineering and Management, 8(2), 2008, pp [8] Jang, I. Y., Park, H. G., Kim, S. S., Kim, J. H. and Kim, Y. G., On the Ductility of High- Strength Concrete Beams, International Journal of Concrete Structures and Materials, 2(2), 2008, pp [9] Arslan, G. and Cihanli, E., Curvature Ductility Prediction of Reinforced High-Strength Concrete Beam Sections, Journal of Civil Engineering and Management, 16(4), 2010, pp [10] Bai, Z. Z. and Au, F. T. K., Flexural Ductility Design of High-Strength Concrete Beams, The Structural Design of Tall Special Buildings, 2011, pp [11] Bilec, M. M., Ries, R., Matthews, H. S. and Sharrard, A. L., Example of a Hybrid Life- Cycle Assessment of Construction Processes, Journal of Infrastructure Systems, 12(4), 2006, pp [12] Sharrard, A. L., Matthews, S. H. and Ries, R. J., Estimating Construction Project Environmental Effects Using an Input-Output-Based Hybrid Life-Cycle Assessment Model, Journal of Infrastructure Systems, 14(4), 2008, pp [13] Chris T. H., Arpad H., Satish J. and Lester B. L., Economic Input-Output Models for Environmental Life Cycle Assessment, Environmental Science & Technology, 32(7), 1998, pp [14] Lee, K. H. and Yang, J. H., A Study on the Functional Unit Estimation of Energy Consumption and Carbon Dioxide Emission in the Construction Materials, Journal of the Architectural Institute of Korea Structure & Construction, 25(6), 2009, pp [15] Hong, T. H., Ji, C.Y. and Jang, M. H., An analysis on CO 2 emission of structural steel materials by strength using input-output analysis. Korean Journal of Construction Engineering and Management, 13(4), 2012, pp editor@iaeme.com