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  1. ํ•œ๊ตญ๊ฑด์„ค๊ธฐ์ˆ ์—ฐ๊ตฌ์› ๊ตฌ์กฐ์—ฐ๊ตฌ๋ณธ๋ถ€ ๋ฐ•์‚ฌํ›„์—ฐ๊ตฌ์› (Researcher, Department of Structural Engineering Research, Korea Institute of Civil Engineering and Building Technology, Goyang 10223, Rep. of Korea)
  2. ๊ตฐ์‚ฐ๋Œ€ํ•™๊ต ํ† ๋ชฉ๊ณตํ•™๊ณผ ๊ต์ˆ˜ (Professor, Department of Civil Engineering, Kunsan National University, Kunsan 54150, Rep. of Korea)



์—ด์—๋„ˆ์ง€ ์ €์žฅ, ์—ด์‚ฌ์ดํด, ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ, ์••์ถ•๊ฐ•๋„, ์—ด์ „๋„๋„
thermal energy storage, thermal cycle, ultra-high performance concrete, compressive strength, thermal conductivity

1. ์„œ ๋ก 

ํ™”์„์—ฐ๋ฃŒ๋ฅผ ์ด์šฉํ•œ ์—๋„ˆ์ง€ ์ƒ์‚ฐ ๋ฐ ๊ณต๊ธ‰์€ ์‚ฌํšŒ ์ „๋ฐ˜์— ๊ฑธ์ณ ๋ฐ€์ ‘ํ•˜๊ฒŒ ์˜ํ–ฅ๋ ฅ์„ ํ–‰์‚ฌํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ์ธ๋ฅ˜์˜ ํ•„์ˆ˜์ ์ธ ์š”์†Œ๋กœ ์ž‘์šฉํ•˜๊ณ  ์žˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ์‚ฌ์šฉ๋Ÿ‰์˜ ์ฆ๋Œ€๋กœ ์ธํ•ด ๋ฐœ์ƒํ•˜๋Š” ํ™˜๊ฒฝ์˜ค์—ผ, ํ˜ธํก๊ธฐ์งˆํ™˜ ๋ฐ ์ง€๊ตฌ์˜จ๋‚œํ™”์™€ ๊ฐ™์€ ์—ฌ๋Ÿฌ ๋ฌธ์ œ์ ์„ ์•ผ๊ธฐ์‹œํ‚ค๊ณ  ์žˆ์œผ๋ฉฐ ๋” ๋‚˜์•„๊ฐ€ ํ™”์„์—ฐ๋ฃŒ๋Š” ํ˜•์„ฑ๋˜๋Š” ๋ฐ ์ˆ˜๋ฐฑ๋งŒ ๋…„์ด ๊ฑธ๋ฆฌ๋Š” ๋น„์žฌ์ƒ ์—๋„ˆ์ง€๋กœ ์ ์ฐจ ๊ณ ๊ฐˆ๋˜์–ด ๊ฐ€๊ณ  ์žˆ๋Š” ์ถ”์„ธ์ด๋‹ค(KeleลŸ 2011; Martins et al. 2018). ์ด๋Ÿฌํ•œ ๋ฌธ์ œ์ ์„ ๊ทน๋ณตํ•˜๊ณ  ๋ฏธ๋ž˜์ง€ํ–ฅ์ ์ธ ํšจ์œจ์  ์—๋„ˆ์ง€์›์„ ๊ตฌ์ถ•ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋Œ€์ฒด์—๋„ˆ์ง€ ๋˜๋Š” ์‹ ์žฌ์ƒ์—๋„ˆ์ง€์˜ ๊ฐœ๋ฐœ ์—ฐ๊ตฌ๊ฐ€ ์ „ ์„ธ๊ณ„์˜ ๋‹ค์–‘ํ•œ ๋ถ„์•ผ์— ๊ฑธ์ณ ๊พธ์ค€ํžˆ ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค(Skinner et al. 2014; Xu et al. 2019).

์‹ ์žฌ์ƒ์—๋„ˆ์ง€๋Š” ํƒœ์–‘์—ด์—๋„ˆ์ง€, ๋ฐ”์ด์˜ค๋งค์Šค, ํ’๋ ฅ, ์†Œ์ˆ˜๋ ฅ ๋ฐ ํ•ด์–‘์—๋„ˆ์ง€ ๋“ฑ ์—ฌ๋Ÿฌ ํ˜•ํƒœ์™€ ๋ถ„์•ผ๋กœ ๊ฐœ๋ฐœ๋˜๊ณ  ์žˆ๋‹ค(Arutyunov and Lisichkin 2017). ํƒœ์–‘์—ด ์—๋„ˆ์ง€์˜ ๊ฒฝ์šฐ, ํƒœ์–‘์ด 1์‹œ๊ฐ„ ๋™์•ˆ ์ง€ํ‘œ๋ฉด์— ๊ณต๊ธ‰ํ•˜๋Š” ์—๋„ˆ์ง€์–‘์€ ์ „ ์ธ๋ฅ˜๊ฐ€ 1๋…„ ๋™์•ˆ ์†Œ๋น„ํ•˜๋Š” ์—๋„ˆ์ง€์–‘์„ ์ถฉ๋‹นํ•  ์ˆ˜ ์žˆ์„ ์ •๋„์˜ ์ž ์žฌ๋ ฅ์„ ๊ฐ–๋Š”๋‹ค(Tian and Zhao 2013). ๋˜ํ•œ, ํƒœ์–‘์ด ์—ด์„ ๋ฐฉ์‚ฌํ•˜๋Š” ์ˆ˜๋ช… ๋™์•ˆ ๋ฌดํ•œํ•œ ๊ณต๊ธ‰์ด ๊ฐ€๋Šฅํ•˜๋ฉฐ, ์œ ํ•ด๊ฐ€์Šค ๋ฐฐ์ถœ์ด ์—†๋Š” ๋ฌด๊ณตํ•ด ์ž์›์œผ๋กœ ์ฐจ์„ธ๋Œ€ ์ฃผ๋ ฅ ์—๋„ˆ์ง€์›์œผ๋กœ์จ ์šฐ์ˆ˜ํ•œ ํ™œ์šฉ ๊ฐ€์น˜๋ฅผ ์ง€๋‹ˆ๊ณ  ์žˆ๋‹ค(Laing et al. 2006; Palacios et al. 2020). ๊ทธ๋Ÿฌ๋‚˜, ํƒœ์–‘์—ด์—๋„ˆ์ง€๋ฅผ ํ™œ์šฉํ•˜๊ธฐ ์œ„ํ•œ ์„ค๋น„ ๊ตฌ์ถ•์˜ ๋น„์šฉ, ๋†’์€ ๋ฐœ์ „๋‹จ๊ฐ€, ๋‚ฎ์€ ์—๋„ˆ์ง€ ํšจ์œจ, ๋‚ฎ๊ณผ ๋ฐค์˜ ์ˆœํ™˜์œผ๋กœ ์ธํ•ด ์ง€์†์ ์ธ ์—๋„ˆ์ง€ ๊ณต๊ธ‰ ๋ถˆ๊ฐ€ ๋“ฑ์˜ ๋ฌธ์ œ์ ์ด ์žˆ๋‹ค. ๋”ฐ๋ผ์„œ, ์—๋„ˆ์ง€ ํšจ์œจ์„ ๋†’์ด๊ณ  ์ง€์†์ ์ธ ์—๋„ˆ์ง€ ๊ณต๊ธ‰์„ ์œ„ํ•œ ์ €์žฅ ๋งค์ฒด ๊ฐœ๋ฐœ ์—ฐ๊ตฌ๊ฐ€ ์„ ํ–‰๋˜์–ด์•ผ ํ•œ๋‹ค(Tamme et al. 2004; Steinmann and Buschle 2005).

ํƒœ์–‘์—ด ์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด๋Š” ์—ด์—๋„ˆ์ง€๋ฅผ ์ˆ˜์šฉํ•จ๊ณผ ๋™์‹œ์— ์ถฉ๋ถ„ํ•œ ์ €์žฅ์šฉ๋Ÿ‰์„ ๋‚˜ํƒ€๋‚ด์•ผ ํ•˜๋ฉฐ, ๊ฒฝ์ œ์„ฑ๊ณผ ๋‚ด๊ตฌ์„ฑ์ด ํ™•๋ณด๋˜์–ด์•ผ ์ €์žฅ ๋งค์ฒด๋กœ์„œ ๊ฐ€์น˜๋ฅผ ๊ฐ–๋Š”๋‹ค(Laing et al. 2009; Basecq et al. 2013). ๋‹ค์–‘ํ•œ ์ €์žฅ ๋งค์ฒด๊ฐ€ ๊ฐœ๋ฐœ ์ค‘์ด๋‚˜, ์—ด์— ๋Œ€ํ•œ ๋‚ด๊ตฌ์„ฑ์ด ์šฐ์ˆ˜ํ•˜๊ณ  ๊ฐ’์‹ผ ์žฌ๋ฃŒ๋น„๋กœ ์ธํ•ด ๊ฒฝ์ œ์„ฑ์ด ์ข‹๊ณ , ์—๋„ˆ์ง€ ์ €์žฅ์šฉ๋Ÿ‰์— ์ค‘์š”ํ•œ ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š” ๋‹จ์œ„์ค‘๋Ÿ‰์ด ์šฐ์ˆ˜ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์ €์žฅ ๋งค์ฒด๋กœ ์ ํ•ฉํ•œ ์žฌ๋ฃŒ์ด๋‹ค(Fernรกndez et al. 2010; John et al. 2013; Ling and Poon 2013).

Jian et al. (2015)์€ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ชจ๋“ˆ์„ ํ™œ์šฉํ•˜์—ฌ ์—ด์—๋„ˆ์ง€ ๊ณ ์ฒด ๋งค์ฒด์˜ ํ˜„์—ด ์ €์žฅ์‹œ์Šคํ…œ์˜ ์„ฑ๋Šฅ ๋ถ„์„์„ ์ˆ˜ํ–‰ํ•˜์—ฌ ๊ฒฝ์ œ์ ์ธ ์—๋„ˆ์ง€ ์šด์šฉ์ด ๊ฐ€๋Šฅํ•˜๋‹ค๋Š” ์—ฐ๊ตฌ ๊ฒฐ๋ก ์„ ๋„์ถœํ•˜์˜€์œผ๋ฉฐ, Salomoni et al. (2014)์€ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์†Œ์— ์ฝ˜ํฌ๋ฆฌํŠธ ์ €์žฅ ๋งค์ฒด ํ™œ์šฉ ์ถ•์—ด ์‹œ์Šคํ…œ ๊ตฌ์ถ•์„ ์œ„ํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ™”ํ•™์ , ๋ฌผ๋ฆฌ์  ๋ฐ ๋‚ด๊ตฌ์„ฑ์— ๋Œ€ํ•œ ๊ธฐ์ดˆ ์—ฐ๊ตฌ๋ฅผ ์ง„ํ–‰ํ•˜์˜€๋‹ค. ํ•œํŽธ, John et al. (2013)์€ ์ตœ๋Œ€ 600 ยฐC์˜ ์˜จ๋„๋ฅผ ๊ฒฌ๋””๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐœ๋ฐœ ์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•˜์—ฌ ์ถ•์—ด ์„ฑ๋Šฅ์„ ๋ถ„์„ํ•˜์˜€์œผ๋ฉฐ, Aydฤฑn et al. (2008)์€ ๊ณ ์˜จ ๋…ธ์ถœ๋œ ๋ณดํ†ต๊ฐ•๋„ ๋ชจ๋ฅดํƒ€๋ฅด์™€ ๊ฐ•์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋œ ๊ณ ๊ฐ•๋„ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์—ญํ•™์  ํŠน์„ฑ์„ ๋ถ„์„ํ•˜์˜€๋‹ค. ๋˜ํ•œ, Wang et al. (2018)์€ ์„œ๋กœ ๋‹ค๋ฅธ ๊ณจ์žฌ๋ฅผ ๋ณ€์ˆ˜๋กœ ๋‘์–ด ์ œ์ž‘๋œ 50 MPa ์ดํ•˜์˜ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋Œ€ํ•ด ์˜จ๋„๋ณ€ํ™” ํŠน์„ฑ์„ ๋ถ„์„ํ•˜์˜€๋‹ค. ์ด์ฒ˜๋Ÿผ ๋ณดํ†ต๊ฐ•๋„ ๋˜๋Š” ๊ณ ๊ฐ•๋„ ์ˆ˜์ค€์˜ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด๋กœ ํ™œ์šฉํ•˜๊ธฐ ์œ„ํ•œ ๋‹ค๊ฐ์  ์—ฐ๊ตฌ๊ฐ€ ํ™œ๋ฐœํžˆ ์ง„ํ–‰ ์ค‘์ด๋‚˜, 120 MPa ์ด์ƒ ์ˆ˜์ค€์˜ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๊ด€ํ•œ ์—ฐ๊ตฌ๋Š” ์‹ค์ƒ ๋ฏธ๋น„ํ•˜๋‹ค.

๋”ฐ๋ผ์„œ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์„ค๊ณ„๊ธฐ์ค€ ์••์ถ•๊ฐ•๋„ 120 MPa ๋ฐ 180 MPa ์ˆ˜์ค€์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ(ultra-high performance concrete, UHPC)๋ฅผ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด๋กœ ํ™œ์šฉํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์„ฑ๋Šฅ ๋ถ„์„ ์‹คํ—˜์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์‹ค์ฆ ์‚ฌ๋ก€์—์„œ ํƒœ์–‘์—ด์—๋„ˆ์ง€๋ฅผ ํ™œ์šฉํ•˜๊ธฐ ์œ„ํ•ด ์ง‘์—ดํ•˜๋Š” ๊ฒฝ์šฐ, ์•ฝ 400 ยฐC๋กœ ๋†’์€ ์ˆ˜์ค€์˜ ๊ณ ์˜จ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๋˜ํ•œ, ํšจ์œจ๊ณผ ์ƒ์‚ฐ์„ฑ์„ ๋†’์ด๊ธฐ ์œ„ํ•ด์„œ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด๋Š” ๊ณ ์˜จ ์ ์šฉ๊ณผ ๋ฐ˜๋ณต์ ์ธ ์‚ฌ์šฉ์— ๋Œ€ํ•œ ๋‚ด๊ตฌ์„ฑ ํ™•๋ณด ๋ฐ ์„ฑ๋Šฅ ๋ณ€ํ™”๊ฐ€ ๋‚ฎ์•„์•ผ ํ•œ๋‹ค. ์ด์— 400 ยฐC์˜ ๊ณ ์˜จ์— ๋…ธ์ถœ๋˜๊ธฐ ์ „๊ณผ 400 ยฐC์˜ ๊ณ ์˜จ์— ๋ฐ˜๋ณต์ ์œผ๋กœ ๋…ธ์ถœ๋œ ํ›„์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ์žฌ๋ฃŒํŠน์„ฑ์„ ํŒŒ์•…ํ•˜์—ฌ ๋‚ด๊ตฌ์„ฑ ๋ฐ ์„ฑ๋Šฅ ๋ณ€ํ™”๋ฅผ ํŒŒ์•…ํ•˜๊ณ ์ž ํ•˜์˜€๋‹ค. ๋‹จ์œ„์ค‘๋Ÿ‰ ์ธก์ •์„ ํ†ตํ•ด ๋ฐ˜๋ณต์ ์ธ ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด์—์„œ ๋ฌผ๋ฆฌ์  ์•ˆ์ •์„ฑ์— ๊ด€ํ•˜์—ฌ ํ‰๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ๊ณ ์˜จ์—์„œ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ํ›„์˜ ์••์ถ•๊ฐ•๋„, ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„, ์—ด์ „๋„๋„ ๋ฐ ๋น„์—ด ํŠน์„ฑ์„ ๋น„๊ต ๋ถ„์„ํ•˜์˜€๋‹ค. ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ํ›„์˜ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์˜ ๋ฏธ์„ธ๊ตฌ์กฐ๋ฅผ ์ฃผ์‚ฌ์ „์žํ˜„๋ฏธ๊ฒฝ์„ ํ†ตํ•ด ๋ถ„์„ํ•˜์˜€์œผ๋ฉฐ, ์—ด์ค‘๋Ÿ‰ ๋ถ„์„์„ ํ†ตํ•ด ์—ด์‚ฌ์ดํด์˜ ์˜ํ–ฅ์— ๋Œ€ํ•ด ๊ณ ์ฐฐํ•˜์˜€๋‹ค.

2. ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด์šฉ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ์ œ์กฐ

2.1 ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐฐํ•ฉ ๋ฐ ์ œ์ž‘

Table 1์— ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด์šฉ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„๋ฐฐํ•ฉํ‘œ๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์„ค๊ณ„๊ธฐ์ค€๊ฐ•๋„ 120 MPa ๋ฐ 180 MPa๋ฅผ ์„ค์ •ํ•˜์˜€์œผ๋ฉฐ, ๊ฐ๊ฐ์˜ ๋ฌผ-๋ฐ”์ธ๋” ๋น„๋Š” 0.22 ๋ฐ 0.18์ด๋‹ค. ๋‚ฎ์€ ๋ฌผ-๋ฐ”์ธ๋”๋น„๋ฅผ ํ†ตํ•ด ์ˆ˜๋Ÿ‰์„ ๊ฐ์†Œ์‹œ์ผœ ๊ณต๊ทน์˜ ๊ฐ์†Œ ๋ฐ ๋‚ด๊ตฌ์„ฑ ํ–ฅ์ƒ์„ ๋„๋ชจํ•˜์˜€๋‹ค. ๋˜ํ•œ, ๋‚ฎ์€ ๋ฌผ-๋ฐ”์ธ๋” ๋น„๋กœ ์ธํ•œ ์žฌ๋ฃŒ ๊ฐ„์˜ ๊ต๋ฐ˜ ๋ฐ ์ž‘์—…์„ฑ ํ™•๋ณด๋ฅผ ์œ„ํ•˜์—ฌ ๊ณ ์„ฑ๋Šฅ ๊ฐ์ˆ˜์ œ๋ฅผ ์ ์šฉํ•˜์˜€๋‹ค. ๊ธฐ๋ณธ ๋ฐ”์ธ๋”๋กœ์จ ๋ณดํ†ต ํฌํ‹€๋žœ๋“œ ์‹œ๋ฉ˜ํŠธ๋ฅผ ์„ค์ •ํ•˜์˜€์œผ๋ฉฐ, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฐ•๋„ ์ฆ์ง„์„ ์œ„ํ•œ ์น˜๋ฐ€ํ•œ ์กฐ์ง์ด ๋  ์ˆ˜ ์žˆ๋„๋ก ์ง€๋ฅด์ฝ”๋Š„๊ณผ ํ•„๋Ÿฌ๋ฅผ ํ˜ผ์ž…ํ•˜์—ฌ ๋ฐฐํ•ฉ์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

๋ณดํ†ต ๋ฐ ๊ณ ๊ฐ•๋„ ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ๋‹ฌ๋ฆฌ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ๋†’์€ ์—ญํ•™์  ํŠน์„ฑ ํ™•๋ณด๋ฅผ ์œ„ํ•ด ๊ฐ•์„ฌ์œ ๋ฅผ ํฌํ•จํ•œ๋‹ค. ๊ฐ•์„ฌ์œ ๋Š” ๋†’์€ ์—ด์ „๋„๋„๋ฅผ ๊ฐ€์ง€๋ฉฐ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ผ์„œ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด์šฉ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์—ด์  ์„ฑ๋Šฅ์„ ์ขŒ์šฐํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จํ•˜์˜€๋‹ค. ์ด์— 120 MPa ๋ฐ 180 MPa ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์—์„œ ๊ฐ•์„ฌ์œ ๋ฅผ ๋ถ€ํ”ผ๋น„ 1.0, 1.5 ๋ฐ 2.0 %์˜ ํ˜ผ์ž…๋ฅ ๋กœ ์„ค์ •ํ•˜์—ฌ ์ œ์ž‘์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์‚ฌ์šฉ๋œ ๊ฐ•์„ฌ์œ ๋Š” ๋ฐ€๋„ 7,500 kg/m3, ์ธ์žฅ๊ฐ•๋„ 2,500 MPa์ด๋ฉฐ, ์ง๊ฒฝ 0.2 mm, ๊ธธ์ด 19.5 mm์˜ ์ง์„  ํ˜•์ƒ์„ ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, ๊ทธ ํ˜•์ƒ์„ Fig. 1(a)์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

ํ•œํŽธ, ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ๋ณดํ†ต ์ฝ˜ํฌ๋ฆฌํŠธ๋ณด๋‹ค ์กฐ์ง์ด ์น˜๋ฐ€ํ•˜์—ฌ 400 ยฐC ์ด์ƒ์˜ ๊ณ ์˜จ์— ๋…ธ์ถœ๋˜์—ˆ์„ ์‹œ, ํญ๋ ฌ ํ˜„์ƒ(spalling failure)์„ ์ดˆ๋ž˜ํ•  ์ˆ˜ ์žˆ๋‹ค. ๋”ฐ๋ผ์„œ, ํญ๋ ฌ์„ ์ตœ์†Œํ™”ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ํด๋ฆฌํ”„๋กœํ•„๋ Œ ์„ฌ์œ (polypropylene fiber, PP fiber)๋ฅผ ์ฝ˜ํฌ๋ฆฌํŠธ์— ํ˜ผ์ž…ํ•˜์˜€๋‹ค. ์ด๋•Œ, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์„ฑ๋Šฅ ๋ณ€ํ™”๋ฅผ ์ตœ์†Œํ™”ํ•˜๋Š” ๋ฒ”์œ„์—์„œ ํญ๋ ฌ์„ ํšจ๊ณผ์ ์œผ๋กœ ๋ฐฉ์ง€ํ•  ์ˆ˜ ์žˆ๋„๋ก ๋‹จ์œ„๋ฐฐํ•ฉ๋‹น 2.0 kg/m3๋ฅผ ํ˜ผ์ž…ํ•˜์˜€๋‹ค(John et al. 2011). PP ์„ฌ์œ ๋Š” ์ง๊ฒฝ 21 ยตm, ๊ธธ์ด 12.7 mm, ์ธ์žฅ๊ฐ•๋„๋Š” 400 MPa์˜ ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ด๋Š” ๊ฒƒ์œผ๋กœ ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, ๊ทธ ํ˜•์ƒ์„ Fig. 1(b)์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

์žฌ๋ฃŒ์‹คํ—˜์„ ์œ„ํ•ด ์‹œํŽธ์€ ฮฆ100ร—200 mm์˜ ์›์ฃผํ˜• ๊ณต์‹œ์ฒด๋ฅผ ๊ฐ ๋ฐฐํ•ฉ๋ณ„๋กœ ์ œ์ž‘ํ•˜์˜€๋‹ค. ํƒ€์„ค ์‹œ์— ๊ณต์‹œ์ฒด ์ค‘์‹ฌ๋ถ€๋ฅผ ๊ธฐ์ค€์œผ๋กœ 100 mm์— ์˜จ๋„์„ผ์„œ(thermocouple)์˜ ์ธก์ ์ด ์œ„์น˜ํ•˜๋„๋ก ๋งค๋ฆฝํ•˜์—ฌ ๊ณ ์˜จ ๋…ธ์ถœ๋กœ ์ธํ•˜์—ฌ ๋ณ€ํ•˜๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์˜ ์˜จ๋„๋ฅผ ์‹ค์‹œ๊ฐ„์œผ๋กœ ์ธก์ •ํ•˜์˜€๋‹ค. ์žฌ๋ฃŒ ๋ฐฐํ•ฉ ํ›„, ํƒ€์„ค๋œ ๊ณต์‹œ์ฒด๋Š” 24์‹œ๊ฐ„ ์–‘์ƒ ์ดํ›„ ํƒˆํ˜• ํ•˜์˜€์œผ๋ฉฐ, ์ดํ›„, ๊ฑด์กฐ์ˆ˜์ถ• ๋ฐฉ์ง€์™€ ์ดˆ๊ธฐ๊ฐ•๋„ ๋ฐœํ˜„์„ ์œ„ํ•˜์—ฌ 72์‹œ๊ฐ„์— ๊ฑธ์ณ 90ยฑ5 ยฐC์—์„œ ์ฆ๊ธฐ์–‘์ƒ์„ ์‹ค์‹œํ•˜์˜€๋‹ค. ์ฆ๊ธฐ์–‘์ƒ์ด ์™„๋ฃŒ๋œ ์‹œํŽธ์€ ์žฌ๋ น 28์ผ๊นŒ์ง€ ๊ธฐ๊ฑด์–‘์ƒ์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์–‘์ƒ์ด ์™„๋ฃŒ๋œ ์‹œํŽธ์€ ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ํ›„๋กœ ๊ตฌ๋ถ„ํ•˜์—ฌ ์žฌ๋ฃŒ์‹คํ—˜์„ ์‹ค์‹œํ•˜์˜€์œผ๋ฉฐ, ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด๋กœ์จ ์„ฑ๋Šฅ ํ‰๊ฐ€๋ฅผ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

Fig. 1 Fiber appearance
../../Resources/KCI/JKCI.2023.35.4.421/fig1.png
Table 1 Mixing proportion

Mixture no.

fck

W/B

(%)

Unit weight (kg/m3)

Steel fiber content

(%)

PP fiber content

(kg/m3)

W

OPC

Zr

BFS

F.A

F

U120-S10

120

0.22

209

770

58

135

847

231

1.0

2.0

U120-S15

0.22

209

770

58

135

847

231

1.5

2.0

U120-S20

0.22

209

770

58

135

847

231

2.0

2.0

U180-S10

180

0.18

178

783

196

-

862

235

1.0

2.0

U180-S15

0.18

178

783

196

-

862

235

1.5

2.0

U180-S20

0.18

178

783

196

-

862

235

2.0

2.0

Notes: W: water; B: binder; OPC: ordinary portland cement; Zr: zirconium; BFS: blast furnace slag; F.A: fine aggregate; F: filler; PP: polypropylene

2.2 ์—ด์‚ฌ์ดํด ๋ฐ ์ฝ˜ํฌ๋ฆฌํŠธ ์˜จ๋„๋ณ€ํ™”

ํƒœ์–‘์—ด ์—๋„ˆ์ง€๋ฅผ ํ™œ์šฉํ•œ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๊ธฐ์ˆ  ๋ฉ”์ปค๋‹ˆ์ฆ˜์€ ๋‚ฎ ์‹œ๊ฐ„๋Œ€์—๋Š” ํƒœ์–‘์œผ๋กœ๋ถ€ํ„ฐ ์—ด์„ ์ง‘์—ดํ•˜์—ฌ ์—ด์ €์žฅ ๋งค์ฒด์— ์ €์žฅํ•˜๊ณ , ๋ฐค ์‹œ๊ฐ„๋Œ€์—๋Š” ์ €์žฅ๋œ ์—ด์ด ๋ฐฉ์—ด ๋˜์–ด ์—๋„ˆ์ง€๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ๊ตฌ์กฐ์ด๋‹ค. ์ด์— ์—ด์—๋„ˆ์ง€์˜ ์ „๋‹ฌ๋กœ ๋‚˜ํƒ€๋‚˜๋Š” ์˜จ๋„ ์ƒ์Šน ๋ฐ ๋ƒ‰๊ฐ์˜ ๋ฐ˜๋ณต์ ์ธ ๊ณผ์ •์„ ์žฌํ˜„ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์—ด์ฃผ๊ธฐ, ์ฆ‰, ์—ด์‚ฌ์ดํด์„ ๊ณ„ํšํ•˜์˜€๋‹ค. ์—ด์‚ฌ์ดํด ์ตœ๋Œ€๋ชฉํ‘œ ์˜จ๋„๋Š” 400 ยฐC๋กœ ์„ค์ •ํ•˜์˜€์œผ๋ฉฐ, ํƒœ์–‘์—ด ์—๋„ˆ์ง€๋ฅผ ์ง‘์—ดํ•˜์—ฌ ์‚ฌ์šฉ๋˜๋Š” 300~ 390 ยฐC์˜ ์˜จ๋„ ๋ฒ”์œ„๋ฅผ ๋งŒ์กฑํ•  ์ˆ˜ ์žˆ๋„๋ก ํ•˜์˜€๋‹ค(Laing et al. 2009). ์—ด์‚ฌ์ดํด์€ ์˜จ๋„๊ฐ€ ์ƒ์Šน๋˜๋Š” ๊ฐ€์—ด๋‹จ๊ณ„, ์˜จ๋„๊ฐ€ ์ผ์ •ํ•˜๊ฒŒ ์œ ์ง€๋˜๋Š” ์œ ์ง€๋‹จ๊ณ„, ์˜จ๋„๊ฐ€ ํ•˜๊ฐ•ํ•˜๋Š” ๋ƒ‰๊ฐ๋‹จ๊ณ„ ๋“ฑ 3๋‹จ๊ณ„๋กœ ๊ตฌ์„ฑ๋œ๋‹ค. ๊ฐ€์—ด๋‹จ๊ณ„์—์„œ๋Š” ์ตœ๋Œ€๋ชฉํ‘œ ์˜จ๋„์ธ 400 ยฐC๊นŒ์ง€ ์ฝ˜ํฌ๋ฆฌํŠธ ์‹œํŽธ์„ 2์‹œ๊ฐ„ ๋™์•ˆ ๊ฐ€์—ดํ•˜๊ณ , ์œ ์ง€๋‹จ๊ณ„์—์„œ๋Š” ์ตœ๋Œ€๋ชฉํ‘œ ์˜จ๋„์ธ 400 ยฐC์—์„œ 2์‹œ๊ฐ„ ๋™์•ˆ ์˜จ๋„๋ฅผ ์ผ์ •ํ•˜๊ฒŒ ์œ ์ง€ํ•˜๊ณ , ๋ƒ‰๊ฐ๋‹จ๊ณ„์—์„œ 400 ยฐC์—์„œ ์ƒ์˜จ๊นŒ์ง€ ์„œ์„œํžˆ ๋ƒ‰๊ฐ๋˜๋„๋ก ์„ค์ •ํ•˜์—ฌ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ด๋Ÿฌํ•œ ์—ด์‚ฌ์ดํด์„ ์†Œ์„ฑ๋กœ(furnace)์— ํ”„๋กœ๊ทธ๋žจํ•˜์—ฌ ์ด 6ํšŒ ์‹ค์‹œํ•˜์˜€์œผ๋ฉฐ, ์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์˜ ์˜จ๋„๋ณ€ํ™”๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค.

Fig. 2์—๋Š” ์„ค์ •ํ•œ ์—ด์‚ฌ์ดํด์„ ๋„์‹œํ™”ํ•œ ๊ทธ๋ž˜ํ”„(Fig. 2(a))์™€ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„ U120-S10 ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์˜ ์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ์˜จ๋„๋ณ€ํ™”๋ฅผ ์ธก์ •ํ•œ ๊ทธ๋ž˜ํ”„(Fig. 2(b))๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์†Œ์„ฑ๋กœ์—์„œ ๊ณ„ํš๋œ ์—ด์‚ฌ์ดํด์— ๋”ฐ๋ผ ์›์ฃผํ˜• ์ฝ˜ํฌ๋ฆฌํŠธ ์‹œํŽธ์„ ๊ฐ€์—ดํ•˜์˜€๋‹ค.

1ํšŒ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์‹œ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์˜จ๋„๋Š” ์ตœ๋Œ€๋ชฉํ‘œ ์˜จ๋„๊นŒ์ง€ ๋„๋‹ฌํ•˜์ง€ ๋ชปํ•˜๋ฉฐ, ์ตœ๋Œ€ 369.7 ยฐC๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์ด๋Š” ์†Œ์„ฑ๋กœ์—์„œ ๊ณต๊ธ‰ํ•˜๋Š” ์—ด์—๋„ˆ์ง€๊ฐ€ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€ ์ˆ˜๋ถ„ ์ฆ๋ฐœ์— ํ•„์š”ํ•œ ์—๋„ˆ์ง€๋กœ ์‚ฌ์šฉ๋˜์–ด ์ฝ˜ํฌ๋ฆฌํŠธ ์˜จ๋„ ์ƒ์Šน์„ ์–ต์ œํ•˜๋Š” ์˜ํ–ฅ์„ ๋ฏธ์นœ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋ฐ˜๋ฉด์— 2ํšŒ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ดํ›„๋ถ€ํ„ฐ๋Š” ์˜จ๋„ ์œ ์ง€ ๊ตฌ๊ฐ„์—์„œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์˜จ๋„๊ฐ€ ์•ฝ 220๋ถ„์—์„œ ์ตœ๋Œ€๋ชฉํ‘œ ์˜จ๋„์ธ 400 ยฐC์— ๋„๋‹ฌํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. 1ํšŒ ์—ด์‚ฌ์ดํด๋กœ ์ธํ•ด ๋Œ€๋ถ€๋ถ„์˜ ์ˆ˜๋ถ„์ด ์ฆ๋ฐœํ•˜์˜€๊ธฐ ๋•Œ๋ฌธ์— ์˜จ๋„ ์ƒ์Šน์„ ์–ต์ œํ•˜๋Š” ํšจ๊ณผ๊ฐ€ ๋ฏธ๋ฏธํ•˜์˜€์„ ๊ฒƒ์œผ๋กœ ์ถ”์ •๋˜๋ฉฐ, ๋ชฉํ‘œํ•˜๋Š” ์˜จ๋„๊นŒ์ง€ ๋„๋‹ฌํ•˜๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. 3ํšŒ~6ํšŒ ์—ด์‚ฌ์ดํด์„ ์ ์šฉํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ์˜จ๋„๋ณ€ํ™”๋Š” ์œ ์‚ฌํ•œ ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ํ›„์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ‘œ๋ฉด์— ๋Œ€ํ•œ ๊ท ์—ด ๋ฐ ๋ณ€์ƒ‰ ์ƒํƒœ์— ๊ด€ํ•˜์—ฌ Fig. 3์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋Œ€ํ‘œ์ ์œผ๋กœ U120-S10 ์‹œํŽธ์˜ ์‚ฌ์ง„์ด๋ฉฐ, ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „. ์–ด๋‘์šด ๊ณ„์—ด์˜ ํšŒ์ƒ‰์„ ๋ ๋˜ ํ‘œ๋ฉด์€ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์—๋Š” ๋ฐ์€ ๊ณ„์—ด์˜ ๋นจ๊ฐ„์ƒ‰์œผ๋กœ ๋ณ€์ƒ‰๋˜๋Š” ๊ฒƒ์„ ์ •์„ฑ์ ์œผ๋กœ ํ™•์ธํ•˜์˜€๋‹ค. ํ•œํŽธ, 400 ยฐC์˜ ์—ด์‚ฌ์ดํด์— ๋…ธ์ถœ๋˜์—ˆ์Œ์—๋„ ๋šœ๋ ทํ•œ ๊ท ์—ด ํ˜•์ƒ์€ ์œก์•ˆ์œผ๋กœ ๊ด€์ฐฐ๋˜์ง€ ์•Š๊ณ  ๋‹ค์ˆ˜์˜ ๊ณต๊ทน์ด ๊ด€์ฐฐ๋˜์—ˆ๋‹ค. ์ด ๊ณต๊ทน์€ PP ์„ฌ์œ ์˜ ์œตํ•ด๋กœ ํ˜•์„ฑ๋˜์–ด ๊ณ ์˜จ์œผ๋กœ ์ธํ•ด ์ƒ์Šน๋˜๋Š” ๋‚ด๋ถ€์••์„ ์™ธ๋ถ€๋กœ ๋ฐฐ์ถœ์‹œํ‚ค๋Š” ํ†ต๋กœ ์—ญํ• ์„ ํ•จ์œผ๋กœ์จ ํญ๋ ฌ์„ ์–ต์ œํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 2 Thermal cycling curve
../../Resources/KCI/JKCI.2023.35.4.421/fig2.png
Fig. 3 Visual inspection of surface
../../Resources/KCI/JKCI.2023.35.4.421/fig3.png

3. ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด์šฉ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์žฌ๋ฃŒ ํŠน์„ฑ

3.1 ๋‹จ์œ„์ค‘๋Ÿ‰

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์€ ์—ด์šฉ๋Ÿ‰์— ์ค‘์š”ํ•œ ์ธ์ž์ด๋ฉฐ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์ด ํด์ˆ˜๋ก ์—ด์—๋„ˆ์ง€ ์ €์žฅ ์„ฑ๋Šฅ์— ํšจ๊ณผ์ ์ด๋‹ค(Sarbu and Sebarchievici 2018). ๋”ฐ๋ผ์„œ, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ์„ฑ๋Šฅ์„ ํŒ์ •ํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์— ๊ด€ํ•œ ์ •๋ณด๊ฐ€ ํ•„์š”ํ•˜๋‹ค. ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ๋งคํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์„ ์ธก์ •ํ•˜์˜€์œผ๋ฉฐ, ์‹ ๋ขฐ๋„ ํ™•๋ณด๋ฅผ ์œ„ํ•ด 3ํšŒ ์ธก์ •์„ ์‹ค์‹œํ•˜์—ฌ ํ‰๊ท ๊ฐ’์„ ์ฑ„ํƒํ•œ ๊ฒฐ๊ณผ๋ฅผ Fig. 4์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

1ํšŒ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ดํ›„์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์€ ๊ธ‰๊ฒฉํ•œ ๊ฐ์†Œ๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋‹จ์œ„์ค‘๋Ÿ‰ ๊ฐ์†Œ์— ๊ฐ€์žฅ ํฐ ์˜ํ–ฅ์„ ์ฃผ๋Š” ์š”์†Œ๋Š” ์ž์œ ์ˆ˜์™€ ํก์ฐฉ์ˆ˜์˜ ์ฆ๋ฐœ์ด๋ฉฐ, 100~200 ยฐC์˜ ๋ฒ”์œ„์—์„œ ์ฆ๋ฐœํ•œ๋‹ค(Wakili et al. 2015). ๋ณธ ์—ฐ๊ตฌ์—์„œ ์ ์šฉํ•œ ์—ด์‚ฌ์ดํด์€ 100~200 ยฐC๋ฅผ ํ›จ์”ฌ ์ƒํšŒํ•˜๋Š” ์ˆ˜์ค€์œผ๋กœ ๋Œ€๋ถ€๋ถ„์˜ ์ž์œ ์ˆ˜์™€ ํก์ฐฉ์ˆ˜๋Š” 1ํšŒ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ์—์„œ ์ฆ๋ฐœํ•œ๋‹ค. ์ด๋กœ ์ธํ•ด ์ด 6ํšŒ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ๋‹จ๊ณ„ ์ค‘์—์„œ 1ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ๋‹จ์œ„์ค‘๋Ÿ‰ ๊ฐ์†Œ๊ฐ€ ๊ฐ€์žฅ ํฐ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

2ํšŒ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์— ๋‹จ์œ„์ค‘๋Ÿ‰์€ ๋ฏธ๋ฏธํ•˜๊ฒŒ ๊ฐ์†Œํ•˜๊ณ , 3ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„๋ถ€ํ„ฐ ์ฝ˜ํฌ๋ฆฌํŠธ ์‹œํŽธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์€ ๊ฑฐ์˜ ์ผ์ •ํ•˜๊ฒŒ ์œ ์ง€๋˜์—ˆ๋‹ค. ์ด๋Ÿฌํ•œ ์‹คํ—˜ ๊ฒฐ๊ณผ๋Š” ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ฐ˜๋ณต์ ์ธ ๊ณ ์˜จ ๋…ธ์ถœ์— ๋Œ€ํ•œ ๋ฌผ๋ฆฌ์  ์•ˆ์ •์„ฑ์— ๋„๋‹ฌํ–ˆ์Œ์„ ์˜๋ฏธํ•œ๋‹ค.

Fig. 5๋Š” ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์˜ ์ดˆ๊ธฐ ์ƒํƒœ์™€ 6ํšŒ ์ ์šฉ ํ›„, ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰ ์ธก์ • ๊ฒฐ๊ณผ๋ฅผ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0 %์—์„œ 2.0 %๋กœ ์ฆ๊ฐ€ํ• ์ˆ˜๋ก U120 ๋ฐ U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์€ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋ƒˆ์œผ๋ฉฐ, ์ด๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋งคํŠธ๋ฆญ์Šค์— ๋น„ํ•ด ๋” ํฐ ๋‹จ์œ„์ค‘๋Ÿ‰์„ ๊ฐ–๋Š” ๊ฐ•์„ฌ์œ ์˜ ์˜ํ–ฅ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

ํ•œํŽธ, U120 ์‹œ๋ฆฌ์ฆˆ์˜ ๊ฒฝ์šฐ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0, 1.5 ๋ฐ 2.0 % ์ผ ๋•Œ, ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์— ๋น„ํ•ด 6ํšŒ ์ ์šฉ ํ›„์— ๋‹จ์œ„์ค‘๋Ÿ‰์€ ๊ฐ๊ฐ 7.7, 7.3 ๋ฐ 7.2 % ๊ฐ์†Œํ•˜๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ์˜ ๊ฒฝ์šฐ, ๋‹จ์œ„์ค‘๋Ÿ‰์€ ๊ฐ๊ฐ 6.8, 6.7 ๋ฐ 6.5 % ๊ฐ์†Œํ•œ๋‹ค. ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „ ๋Œ€๋น„ ์ ์šฉ ํ›„์˜ ๋‹จ์œ„์ค‘๋Ÿ‰ ๊ฐ์†Œ์œจ์€ ๊ฐ์†Œํ•˜์˜€์œผ๋ฉฐ, ๊ฐ•์„ฌ์œ ๋Š” ์—ด์‚ฌ์ดํด์— ์˜ํ–ฅ์„ ๋ฐ›์•„๋„ ๋‹จ์œ„์ค‘๋Ÿ‰ ๋ณ€ํ™”์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์ด ์ ์€ ๊ฒƒ์„ ์˜๋ฏธํ•œ๋‹ค. ์ฆ‰, ์ž”๋ฅ˜ ํŠน์„ฑ์„ ๋”์šฑ ๋ณด์กดํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์—ด์—๋„ˆ์ง€๋ฅผ ์ €์žฅํ•˜๋Š” ๋ฐ ์œ ๋ฆฌํ•˜๊ฒŒ ์ž‘์šฉํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋˜ํ•œ, ๋™์ผํ•œ ํšŸ์ˆ˜์˜ ์—ด์‚ฌ์ดํด์„ ์ ์šฉํ•œ ์ƒํƒœ์—์„œ U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์ด U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰๋ณด๋‹ค ๋‹ค์†Œ ํฌ์ง€๋งŒ, ๊ทธ ์ฐจ์ด๋Š” ๋งค์šฐ ๊ทผ์†Œํ•˜๋‹ค.

Fig. 4 Unit weight results according to thermal cycles
../../Resources/KCI/JKCI.2023.35.4.421/fig4.png
Fig. 5 Unit weight result at various steel fiber contents
../../Resources/KCI/JKCI.2023.35.4.421/fig5.png

3.2 ์••์ถ•๊ฐ•๋„ ๋ฐ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„

๋‚ด๊ตฌ์„ฑ์— ์ „๋ฐ˜์ ์œผ๋กœ ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š” ๊ฐ•๋„ ํŠน์„ฑ์€ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด์šฉ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์—์„œ ํ•„์ˆ˜์ ์œผ๋กœ ๊ฒ€์ฆํ•ด์•ผ ํ•  ์ธ์ž์ด๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด์— ๋ฐ˜๋ณต์ ์œผ๋กœ ๋…ธ์ถœ๋  ๊ฒฝ์šฐ, ํ†ต์ƒ์ ์œผ๋กœ ๊ฐ•๋„ ์„ฑ๋Šฅ์ด ์ €ํ•˜๋˜์–ด ์›ํ™œํ•œ ์„ฑ๋Šฅ ๋ฐœํ˜„์„ ํ•  ์ˆ˜ ์—†๋‹ค(Husem 2006). ๊ทธ๋Ÿฌ๋‚˜, ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด ์—ญํ• ์„ ์ˆ˜ํ–‰ํ•˜๊ธฐ์— ์ถฉ๋ถ„ํ•œ ๊ฐ•๋„ ์ˆ˜์ค€์„ ๋‚˜ํƒ€๋‚ด๊ณ  ๋ฐ˜๋ณต์ ์ธ ๊ณ ์˜จ์— ๋Œ€ํ•ด ๋‚ด๊ตฌ์„ฑ์ด ํ™•๋ณด๋œ๋‹ค๋ฉด ํ™œ์šฉํ•  ๊ฐ€๋Šฅ์„ฑ์„ ์ œ์‹œํ•  ์ˆ˜ ์žˆ๋‹ค.

์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„, ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••์ถ•๊ฐ•๋„๋ฅผ ์ธก์ •ํ•˜์˜€์œผ๋ฉฐ, 3ํšŒ ์ธก์ •์„ ๋ฐ”ํƒ•์œผ๋กœ ํ‰๊ท ๊ฐ’์„ ์ฑ„ํƒํ•œ ๊ฒฐ๊ณผ๋ฅผ Fig. 6(a)์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ์••์ถ•๊ฐ•๋„๋Š” ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์— ๊ฐ๊ฐ 122.8, 138.7 ๋ฐ 145.3 MPa์ด๊ณ , 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์—๋Š” ๊ฐ๊ฐ 111.0, 126.5 ๋ฐ 133.4 MPa๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋˜ํ•œ, U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ์••์ถ•๊ฐ•๋„๋Š” ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์— ๊ฐ๊ฐ 221.7, 231.1 ๋ฐ 235.4 MPa, 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์—๋Š” ๊ฐ๊ฐ 187.3, 188.6 ๋ฐ 193.3 MPa์ด๋‹ค. ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์••์ถ•๊ฐ•๋„๋Š” ์ฆ๊ฐ€ํ•˜๋ฉฐ, ์ด๋Š” ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ๊ฐ•์„ฌ์œ ์™€ ๋งคํŠธ๋ฆญ์Šค ์‚ฌ์ด์˜ ์‘๋ ฅ์„ ๋ถ„์‚ฐ์‹œํ‚ค๋Š” ์—ญํ• ์„ ํ•˜์—ฌ ๊ท ์—ด ํ˜•์„ฑ ๋ฐ ์ „ํŒŒ๊ฐ€ ์ง€์—ฐ๋˜๋Š” ํšจ๊ณผ๋ฅผ ์ฃผ๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค(Ren et al. 2018). ๋”ฐ๋ผ์„œ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์˜ ์ฆ๊ฐ€๋Š” ์••์ถ•๊ฐ•๋„ ์ฆ์ง„์— ํšจ๊ณผ์ ์ธ ๊ฒƒ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

๋˜ํ•œ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0, 1.5 ๋ฐ 2.0 % ์ผ ๋•Œ, U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๋ณด๋‹ค 6ํšŒ ์ ์šฉ ํ›„์˜ ์••์ถ•๊ฐ•๋„ ๊ฐ์†Œ์œจ์€ ๊ฐ๊ฐ 9.6, 8.8 ๋ฐ 8.2 %์ด๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์••์ถ•๊ฐ•๋„ ๊ฐ์†Œ์œจ์€ ๊ฐ๊ฐ 15.5, 18.4 ๋ฐ 17.9 %์ด๋‹ค. U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์••์ถ•๊ฐ•๋„ ๊ฐ์†Œ์œจ์ด U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ๋ณด๋‹ค ์•ฝ 2๋ฐฐ ์ •๋„ ๋งŽ์ด ๊ฐ์†Œํ•œ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด ๋…ธ์ถœ ํ›„์— U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์••์ถ•๊ฐ•๋„๊ฐ€ U120 ์‹œ๋ฆฌ์ฆˆ์˜ ์••์ถ•๊ฐ•๋„๋ฅผ ์ƒํšŒํ•˜๋Š” ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด ๊ด€์ ์—์„œ ์—ด์‚ฌ์ดํด ๋…ธ์ถœ ํ›„์˜ ์••์ถ•๊ฐ•๋„ ๊ฐ์†Œ์œจ์ด U180 ์‹œ๋ฆฌ์ฆˆ๊ฐ€ ํด์ง€๋ผ๋„ ์‹ค์งˆ์ ์ธ ์••์ถ•๊ฐ•๋„๋Š” U120 ์‹œ๋ฆฌ์ฆˆ๋ณด๋‹ค ํฌ๋ฏ€๋กœ ์ €์žฅ ๋งค์ฒด๋กœ์จ ๋”์šฑ ํšจ๊ณผ์ ์ธ ์žฌ๋ฃŒ์ธ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ๊ณ ์˜จ์˜ ์—ด์„ ๋ฐ›๊ฒŒ ๋˜๋ฉด ๋‚ด๋ถ€์— ์—ด์‘๋ ฅ์ด ๋ฐœ์ƒํ•œ๋‹ค. ์—ด์‘๋ ฅ์€ ๋‚ด๋ถ€์™€ ์™ธ๋ถ€์˜ ์˜จ๋„ ์ฐจ์ด๋กœ ์ธํ•œ ๋ถ€๋“ฑ์˜ ์ฒด์ ๋ณ€ํ™”๋กœ ๋ฐœ์ƒ๋˜๋ฉฐ, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ธ์žฅ์‘๋ ฅ์„ ์œ ๋ฐœํ•œ๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ ์ง€์†ํ•ด์„œ ์—ด์‘๋ ฅ์„ ์ˆ˜์šฉํ•˜๊ฒŒ ๋˜์–ด ํ—ˆ์šฉ์ธ์žฅ์‘๋ ฅ์„ ์ดˆ๊ณผํ•˜๋ฉด ๊ท ์—ด, ๋ฐ•๋ฆฌ ๋ฐ ํƒˆ๋ฝ ๋“ฑ๊ณผ ๊ฐ™์€ ์†์ƒ์„ ๋ฐ›์„ ์ˆ˜ ์žˆ๋‹ค. ๋”ฐ๋ผ์„œ, ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด์šฉ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์—ด์ธ์žฅ์‘๋ ฅ์— ์ €ํ•ญํ•  ์ˆ˜ ์žˆ์–ด์•ผ ํ•œ๋‹ค. ์ด์— ๋”ฐ๋ผ ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ, 3ํšŒ ์ธก์ •์„ ๋ฐ”ํƒ•์œผ๋กœ ํ•œ ํ‰๊ท  ๊ฒฐ๊ณผ๋ฅผ Fig 6(b)์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ, ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„๋Š” U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์— ๊ฐ๊ฐ 9.8, 11.7 ๋ฐ 12.4 MPa, 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์—๋Š” ๊ฐ๊ฐ 8.9, 10.7 ๋ฐ 11.4 MPa์ด๋‹ค. U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์—์„œ๋Š” ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์— ๊ฐ๊ฐ 11.2, 14.7 ๋ฐ 17.4 MPa, 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์—๋Š” ๊ฐ๊ฐ 10.3, 12.8 ๋ฐ 13.8 MPa์ด๋‹ค. ๋˜ํ•œ, ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๋ณด๋‹ค 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„ ๊ฐ์†Œ์œจ์€ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์€ ๊ฐ๊ฐ 9.3, 8.1 ๋ฐ 8.1 %, U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์€ 8.0, 12.9 ๋ฐ 20.7 %์ด๋‹ค.

์••์ถ•๊ฐ•๋„ ๊ฒฝํ–ฅ๊ณผ ์œ ์‚ฌํ•˜๊ฒŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ํ›„์— ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„๋Š” ์ฆ์ง„๋˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋ƒˆ๋‹ค. ๊ฐ•์„ฌ์œ ๋Š” ์ทจ์„ฑ๊ฑฐ๋™์„ ํ•˜๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์ ์„ ๋ณด์™„ํ•˜๊ณ , ๋›ฐ์–ด๋‚œ ์ธ์„ฑ๊ณผ ์—ฐ์„ฑ, ์šฐ์ˆ˜ํ•œ ๊ท ์—ด์ œ์–ด ๋Šฅ๋ ฅ์„ ๋ณด์œ ํ•œ๋‹ค(Leutbecher and Fehling 2012). ์ด๋Ÿฌํ•œ ํŠน์„ฑ์˜ ์˜ํ–ฅ์œผ๋กœ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์˜ ์ฆ๊ฐ€๋Š” ๊ฐ€๊ตํ•˜๋Š” ๊ฐ•์„ฌ์œ  ๊ฐœ์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์„ ์˜๋ฏธํ•˜๋ฉฐ, ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„ ํ–ฅ์ƒ์— ์˜ํ–ฅ์„ ๋ฏธ์นœ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

ํ•œํŽธ, ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„ ๊ฐ์†Œ์œจ์—์„œ U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์ด ์ƒ๋Œ€์ ์œผ๋กœ U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ๋ณด๋‹ค ๋‚ฎ์€ ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋ƒˆ์œผ๋ฉฐ, ๋ฐ˜๋ณต์ ์ธ ๊ณ ์˜จ ๋…ธ์ถœ์— ๋Œ€ํ•œ ์˜ํ–ฅ์ด ์ƒ๋Œ€์ ์œผ๋กœ ์ ์€ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„๋Š” U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์—์„œ 10.3~13.8 MPa์ด๋ฉฐ, U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ 8.9~12.4 MPa์— ๋น„ํ•˜์—ฌ ๋†’์€ ์ˆ˜์ค€์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์ด๋Ÿฌํ•œ ์‹คํ—˜ ๊ฒฐ๊ณผ๋Š” ๋น„๋ก ๋ฐ˜๋ณต์ ์ธ ๊ณ ์˜จ ๋…ธ์ถœ ์กฐ๊ฑด์—์„œ U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„ ๊ฐ์†Œ์œจ์ด U120 ์‹œ๋ฆฌ์ฆˆ์˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„ ๊ฐ์†Œ์œจ๋ณด๋‹ค ํด์ง€๋ผ๋„, ๊ณ ์˜จ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์ž”๋ฅ˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„๊ฐ€ ํฌ๋ฏ€๋กœ ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด๋กœ์จ ์—ด์‘๋ ฅ์— ์˜ํ•œ ์˜ํ–ฅ์—์„œ ๋”์šฑ ์šฐ์ˆ˜ํ•œ ์„ฑ๋Šฅ์„ ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

Fig. 6 Strength test results
../../Resources/KCI/JKCI.2023.35.4.421/fig6.png

3.3 ์—ด์ „๋„๋„ ๋ฐ ๋น„์—ด

์—ด์ „๋„๋„๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ถ•์—ด ๋ฐ ๋ฐฉ์—ด์˜ ์—ด์ „๋‹ฌ ์„ฑ๋Šฅ์— ์ง์ ‘์ ์ธ ์˜ํ–ฅ์„ ์ฃผ๋Š” ๋งค์šฐ ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•œ๋‹ค(DemirboฤŸa 2007). ๋”ฐ๋ผ์„œ, ์—ด์ „๋„๋„๊ฐ€ ๋†’์„์ˆ˜๋ก ์—ด์ „๋‹ฌ ์„ฑ๋Šฅ์€ ํ–ฅ์ƒ๋  ๊ฒƒ์ด๋ฉฐ(Bentz et al. 2011), ์ตœ์ข…์ ์œผ๋กœ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ–ฅ์ƒ๋œ ์ถ•์—ด ์„ฑ๋Šฅ์„ ํ™•๋ณดํ•  ๊ฒƒ์œผ๋กœ ๊ธฐ๋Œ€๋œ๋‹ค.

Fig. 7์— ๋‚˜ํƒ€๋‚ธ ์—ด์ „๋„๋„ ์ธก์ • ์žฅ๋น„(TPS 1500, Hot Disk Ltd., Sweden)๋ฅผ ์ด์šฉํ•˜์—ฌ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ๋งคํšŒ ์—ด์‚ฌ์ดํด ์ดํ›„์˜ ์ฝ˜ํฌ๋ฆฌํŠธ ์—ด์ „๋„๋„๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค(Gustafsson 1991; Log and Gustafsson 1995). ์—ด์ „๋„๋„๋Š” ์žฌ๋ฃŒ ๋™์งˆ์„ฑ์„ ํ™•๋ณดํ•˜๊ธฐ ์œ„ํ•ด ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋กœ ์ œ์ž‘๋œ ์›์ฃผํ˜• ๊ณต์‹œ์ฒด์˜ ์ค‘์•™๋ฉด์„ ์ ˆ๋‹จํ•˜์—ฌ ๋‘ ๊ฐœ์˜ ์‹œํŽธ์„ ์„ค์ •ํ•˜๊ณ  ๋‘ ์‹œํŽธ์˜ ์ ‘์ด‰ํ•˜๋Š” ๋ฉด์˜ ํ‰ํƒ„์„ฑ์„ ํ™•๋ณดํ•œ ํ›„, ์‹œํŽธ ์‚ฌ์ด์— ์—ด์ธก์ • ์„ผ์„œ๋ฅผ ์‚ฝ์ž…ํ•˜์—ฌ ์ธก์ •ํ•˜์˜€๋‹ค. ์—ด์ธก์ • ์„ผ์„œ๋Š” ๋‹ˆ์ผˆ ์„ฑ๋ถ„์˜ ์ด์ค‘ ๋‚˜์„ ์œผ๋กœ ๊ตฌ์„ฑ๋˜๋ฉฐ, ์ด๋ฅผ ํ†ตํ•ด ์‹œํŽธ์— ์—ดํŒŒ(heating pulse)๋ฅผ ๊ณต๊ธ‰ํ•œ๋‹ค. ์ธก์ • ์กฐ๊ฑด์œผ๋กœ ์‹œํŽธ์„ ์‹คํ—˜์‹ค์˜ ์ƒ์˜จ ์กฐ๊ฑด์—์„œ ์•ฝ 90๋ถ„ ๋™์•ˆ ์—ดํ‰ํ˜•์„ ์œ ์ง€ํ•œ ํ›„, 0.3 W ์ „์›์œผ๋กœ ์—ดํŒŒ๋ฅผ ๊ณต๊ธ‰ํ•˜์—ฌ ์—ด์ „๋„๋„๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ๊ฐ ์‹œํŽธ์— ๋Œ€ํ•ด 3ํšŒ์˜ ์ธก์ •์„ ์ˆ˜ํ–‰ํ•˜์—ฌ ํ‰๊ท ๊ฐ’์„ ์‚ฐ์ •ํ•จ์œผ๋กœ์จ ์‹คํ—˜ ๊ฒฐ๊ณผ์˜ ์ •๋ฐ€๋„๋ฅผ ํ™•๋ณดํ•˜๊ณ ์ž ํ•˜์˜€๋‹ค.

Fig. 8(a)์— ๋‚˜ํƒ€๋‚ธ ๋ฐ”์™€ ๊ฐ™์ด 1ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์— ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์—ด์ „๋„๋„๋Š” ๊ธ‰๊ฒฉํ•œ ๊ฐ์†Œ๋ฅผ ๋‚˜ํƒ€๋ƒˆ๋‹ค. ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด์€ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์— ์กด์žฌํ•˜๋Š” ์ˆ˜๋ถ„์˜ ์ฆ๋ฐœ์„ ์ด‰์ง„์‹œํ‚จ๋‹ค. ์ด๋กœ ์ธํ•ด ํ˜•์„ฑ๋œ ๊ณต๊ทน์€ ๊ณต๊ธฐ์˜ ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๊ณต๊ธฐ๋Š” ๊ณ ์ฒด ์žฌ๋ฃŒ๋ณด๋‹ค ๋‚ฎ์€ ์—ด์ „๋„๋„ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด๋ฉฐ, ์—ด์‚ฌ์ดํด๋กœ ์ธํ•ด ๋‹ค๋Ÿ‰ ํ˜•์„ฑ๋œ ๊ณต๊ทน์€ ๊ฒฐ๊ตญ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „์ฒด์ ์ธ ์—ด์ „๋„๋„ ๊ฐ์†Œ๋ฅผ ์œ ๋ฐœํ•˜๋Š” ์š”์†Œ๋กœ ์ž‘์šฉ๋œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด ๊ฒฝํ–ฅ์€ U120 ๋ฐ U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ ๋ชจ๋‘ ๋™์ผํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ดํ›„, 3ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ๋ถ€ํ„ฐ ์—ด์‚ฌ์ดํด ํšŸ์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜์—ฌ๋„ ๋šœ๋ ทํ•œ ์ฆ๊ฐ์—†์ด ์ผ์ •ํ•˜๊ฒŒ ์œ ์ง€๋˜์—ˆ๋‹ค. ์ด๋Š” 1ํšŒ ๋ฐ 2ํšŒ ์—ด์‚ฌ์ดํด์—์„œ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด์— ์กด์žฌํ•˜๋Š” ๋Œ€๋ถ€๋ถ„์˜ ์ˆ˜๋ถ„์ด ์ฆ๋ฐœ๋˜์—ˆ์œผ๋ฉฐ, 3ํšŒ ์ดํ›„๋ถ€ํ„ฐ์˜ ์—ด์‚ฌ์ดํด์€ ์—ด์ „๋„๋„ ๊ฐ์†Œ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์ด ๋ฏธ๋ฏธํ•ด์ง€๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0 %์—์„œ 2.0 %๋กœ ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์—ด์ „๋„๋„๋Š” ์ฆ๊ฐ€ํ•œ๋‹ค(Fig. 8(b)). ๊ฐ•์„ฌ์œ ๊ฐ€ ๊ฐ–๋Š” ๋†’์€ ์—ด์ „๋„๋„ ์„ฑ๋Šฅ์€ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์—ด์ „๋„๋„ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ๋„๋ชจํ•˜๋Š” ์š”์†Œ๋กœ ์ž‘์šฉํ•œ๋‹ค. ๋˜ํ•œ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ, U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์˜ ์—ด์ „๋„๋„๋Š” ๊ฐ๊ฐ 2.010, 2.044 ๋ฐ 2.087 W/m๏ฝฅK์ด๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์ „๋„๋„๋Š” ๊ฐ๊ฐ 2,544. 2.578 ๋ฐ 2.682 W/m๏ฝฅK์ด๋‹ค. U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์ „๋„๋„๋Š” U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์— ๋น„ํ•ด ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ ๊ฐ๊ฐ 26.6, 26.1 ๋ฐ 28.5 % ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋ƒˆ๋‹ค. 6ํšŒ ์—ด์‚ฌ์ดํด์„ ์ ์šฉํ•œ ํ›„์˜ U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์ „๋„๋„๋Š” ๊ฐ๊ฐ 1.435, 1.512 ๋ฐ 1.495 W/m๏ฝฅK์ด๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์ „๋„๋„๋Š” ๊ฐ๊ฐ 2.034, 2.108 ๋ฐ 2.143 W/m๏ฝฅK๋กœ ์ธก์ •๋˜์—ˆ๋‹ค. ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์ „๋„๋„๋Š” U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์ „๋„๋„๋ณด๋‹ค ๊ฐ๊ฐ 41.7, 39.4 ๋ฐ 43.3 % ํ™•์—ฐํžˆ ์ฆ๊ฐ€ํ•˜์˜€๋‹ค.

๋”ฐ๋ผ์„œ, ๋™์ผํ•œ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์—์„œ U180 ์‹œ๋ฆฌ์ฆˆ๋Š” U120 ์‹œ๋ฆฌ์ฆˆ๋ณด๋‹ค ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ํ›„์— ๋†’์€ ์—ด์ „๋„๋„ ํŠน์„ฑ์„ ๋ณด์œ ํ•˜๋ฉฐ, ๋†’์€ ์ˆ˜์ค€์˜ ๊ฐ•๋„ ๋ฐœํ˜„์„ ์œ„ํ•ด ๋”์šฑ ์น˜๋ฐ€ํ•œ ๋งคํŠธ๋ฆญ์Šค ๊ตฌ์กฐ๋ฅผ ๊ฐ–๋Š” ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ํŠน์„ฑ์— ๊ธฐ์ธํ•œ๋‹ค. ํŠนํžˆ, U180 ์‹œ๋ฆฌ์ฆˆ๋Š” U120 ์‹œ๋ฆฌ์ฆˆ๋ณด๋‹ค ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ์—ด์ „๋„๋„ ์„ฑ๋Šฅ ํ™•๋ณด์— ๋งค์šฐ ์œ ๋ฆฌํ•œ ์กฐ๊ฑด์ธ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๋น„์—ด์€ ๊ฐ’์ด ํด์ˆ˜๋ก ์—ด์„ ํก์ˆ˜ํ•˜๋Š” ๋ณธ์งˆ์ ์ธ ๋Šฅ๋ ฅ, ์ฆ‰, ์—ด์šฉ๋Ÿ‰ ์„ฑ๋Šฅ ์ฆ์ง„๊ณผ ์ƒ์‘ํ•œ๋‹ค. 1ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์— U120 ๋ฐ U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๋น„์—ด์€ ๊ธ‰๊ฒฉํ•œ ๊ฐ์†Œ๋ฅผ ๋‚˜ํƒ€๋ƒˆ๋‹ค(Fig. 9(a)). ์—ด์‚ฌ์ดํด ์ ์šฉ์œผ๋กœ ์ธํ•ด ๊ฐ์†Œ๋˜๋Š” ๋น„์—ด์€ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด์— ์กด์žฌํ•˜๋Š” ์ˆ˜๋ถ„์˜ ์ฆ๋ฐœ๊ณผ ์—ฐ๊ด€๋œ๋‹ค. ์•ก์ฒด์ธ ๋ฌผ์€ ๋น„์—ด ์•ฝ 4,200 J/kg๏ฝฅK์˜ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด๋ฉฐ, ๊ธฐ์ฒด์ธ ๊ณต๊ธฐ์˜ ๋น„์—ด์€ ์•ฝ 1,000 J/kg๏ฝฅK์ด๋‹ค. ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด๋กœ ์ธํ•ด ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์— ์กด์žฌํ•˜๋Š” ์ˆ˜๋ถ„์€ ๊ธฐํ™”ํ•˜๋ฉฐ, ๊ฒฐ๊ณผ์ ์œผ๋กœ ๋น„์—ด ๊ฐ์†Œ์— ์˜ํ–ฅ์„ ์ฃผ๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ดํ›„, ์—ด์‚ฌ์ดํด 2ํšŒ ์ ์šฉ๋ถ€ํ„ฐ๋Š” ์—ด์‚ฌ์ดํด ํšŸ์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ๋šœ๋ ทํ•œ ์ฆ๊ฐ์—†์ด ๋Œ€์ฒด๋กœ ์ผ์ •ํ•œ ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์ด๋Š” 1ํšŒ ์—ด์‚ฌ์ดํด์—์„œ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด์— ์กด์žฌํ•˜๋Š” ๋Œ€๋ถ€๋ถ„์˜ ์ˆ˜๋ถ„์ด ์ฆ๋ฐœ๋˜์—ˆ์œผ๋ฉฐ, 2ํšŒ ์ดํ›„๋ถ€ํ„ฐ์˜ ์—ด์‚ฌ์ดํด์€ ๋น„์—ด ๊ฐ์†Œ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์ด ๋ฏธ๋ฏธํ•ด์ง€๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 9(b)์—์„œ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ, ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์˜ ๋น„์—ด์€ U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์—์„œ ๊ฐ๊ฐ 926, 883 ๋ฐ 838 J/kg๏ฝฅK์ด๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์—์„œ ๊ฐ๊ฐ 936, 940 ๋ฐ 865 J/kg๏ฝฅK์ด๋‹ค. ๋˜ํ•œ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ, 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๋น„์—ด์€ ๊ฐ๊ฐ 751, 690 ๋ฐ 658 J/kg๏ฝฅK์ด๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๋น„์—ด์€ ๊ฐ๊ฐ 699, 623 ๋ฐ 593 J/kg๏ฝฅK์ด๋‹ค. ์ด๋Ÿฌํ•œ ์‹คํ—˜ ๊ฒฐ๊ณผ๋Š” U120 ๋ฐ U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ชจ๋‘ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ๋น„์—ด์€ ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋ƒˆ๋‹ค.

Alva et al. (2017)์˜ ์—ฐ๊ตฌ ๊ฒฐ๊ณผ์— ๋”ฐ๋ฅด๋ฉด, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋น„์—ด์€ ์•ฝ 850 J/kg๏ฝฅK, ๊ฐ•์„ฌ์œ ์˜ ๋น„์—ด์€ ์•ฝ 500 J/kg๏ฝฅK์œผ๋กœ ์ œ์‹œํ•˜๊ณ  ์žˆ๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋น„ํ•ด ๊ฐ•์„ฌ์œ ์˜ ๋น„์—ด์ด ์ƒ๋Œ€์ ์œผ๋กœ ๋‚ฎ์€ ๊ฒƒ์— ๋”ฐ๋ผ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋น„์—ด์„ ๊ฐ์†Œ์‹œํ‚ฌ ์ˆ˜ ์žˆ์Œ์„ ์˜๋ฏธํ•œ๋‹ค.

๋˜ํ•œ, ๋™์ผํ•œ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์—์„œ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์˜ ๋น„์—ด์€ U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ U120 ์‹œ๋ฆฌ์ฆˆ์˜ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋ณด๋‹ค ๋†’์€ ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ๋น„์—ด์€ U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ U120 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋ณด๋‹ค ๋‚ฎ์€ ๊ฒฐ๊ณผ๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. ๋”ฐ๋ผ์„œ, U180 ์‹œ๋ฆฌ์ฆˆ๋Š” ๊ณ ์˜จ ๋…ธ์ถœ์—์„œ ๋น„์—ด ์„ฑ๋Šฅ์„ ํ™•๋ณดํ•˜๊ธฐ์— ๋‹ค์†Œ ์–ด๋ ค์›€์ด ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 7 Thermal conductivity measurement system
../../Resources/KCI/JKCI.2023.35.4.421/fig7.png
Fig. 8 Comparison of thermal conductivity results
../../Resources/KCI/JKCI.2023.35.4.421/fig8.png
Fig. 9 Comparison of specific heat results
../../Resources/KCI/JKCI.2023.35.4.421/fig9.png

4. ๊ณ ์˜จ์—์„œ์˜ ๋ฏธ์„ธ๊ตฌ์กฐ ๋ถ„์„

4.1 ์ฃผ์‚ฌ์ „์žํ˜„๋ฏธ๊ฒฝ ๋ถ„์„(SEM)

์—ด์‚ฌ์ดํด ์ ์šฉ ์—ฌ๋ถ€์— ๋”ฐ๋ฅธ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ฏธ์„ธ๊ตฌ์กฐ๋ฅผ ๋ถ„์„ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ฃผ์‚ฌ์ „์žํ˜„๋ฏธ๊ฒฝ(scanning electron microscope, SEM) ์ดฌ์˜์„ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ, U120 ์‹œ๋ฆฌ์ฆˆ์˜ ๊ฒฐ๊ณผ๋ฅผ Fig. 10์— ๋‚˜ํƒ€๋‚ด๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ์˜ ๊ฒฐ๊ณผ๋ฅผ Fig. 11์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„, U120 ๋ฐ U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ชจ๋‘ PP ์„ฌ์œ ๊ฐ€ ์œตํ•ด๋œ ๊ฒƒ์ด ๊ด€์ฐฐ๋˜์—ˆ์œผ๋ฉฐ, ์œตํ•ด๋œ ์œ„์น˜์—๋Š” PP ์„ฌ์œ  ์ž”์—ฌ๋ฌผ์ด ๋‚จ์•„์žˆ๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. PP ์„ฌ์œ ๊ฐ€ ์œ„์น˜ํ•˜๋Š” ๊ณณ์€ ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด ๋…ธ์ถœ๋กœ ์ธํ•ด ๊ธฐ๊ณต์œผ๋กœ ์ „ํ™˜๋˜๋ฉฐ, ๋‚ด๋ถ€์™€ ์™ธ๋ถ€๋ฅผ ์ž‡๋Š” ํ†ต๋กœ ์—ญํ• ๋กœ ์ง„์ „๋˜๊ฒŒ ๋œ๋‹ค. ์ด ํ†ต๋กœ๋Š” ์—ด๋ฆฐ ๊ธฐ๊ณต์ด ๋˜๋ฏ€๋กœ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด์— ์กด์žฌํ•˜๋Š” ์ˆ˜๋ถ„์ด ์ฆ๋ฐœํ•˜์—ฌ ์ด๋™ํ•  ์ˆ˜ ์žˆ๋Š” ์กฐ๊ฑด์„ ํ˜•์„ฑํ•˜๋ฉฐ, ๊ณ ์˜จ์œผ๋กœ ์ธํ•ด ์ƒ๋ณ€ํ™”ํ•˜์—ฌ ํŒฝ์ฐฝํ•˜๋Š” ์ˆ˜์ฆ๊ธฐ์˜ ๋‚ด๋ถ€์••์„ ์™„ํ™”์‹œํ‚จ๋‹ค. ๊ฒฐ๊ณผ์ ์œผ๋กœ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํญ๋ ฌ์„ ์–ต์ œํ•˜๋Š” ํšจ๊ณผ๋ฅผ ๋ถ€์—ฌํ•˜์ง€๋งŒ ๋™์‹œ์— ๊ณต๊ทน ๋ฐ ๊ท ์—ด ๊ฐœ์ˆ˜๋ฅผ ์ฆ๊ฐ€์‹œํ‚ด์œผ๋กœ์จ ์„ฑ๋Šฅ ์ €ํ•˜๋ฅผ ์œ ๋ฐœํ•˜๋Š” ์š”์ธ์œผ๋กœ๋„ ์ž‘์šฉํ•˜๊ฒŒ ๋œ๋‹ค.

ํ•œํŽธ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก SEM ์ด๋ฏธ์ง€์—์„œ ๊ด€์ฐฐ๋˜๋Š” ๊ฐ•์„ฌ์œ ์˜ ์ˆ˜๋Š” ๋šœ๋ ทํ•œ ์ฐจ์ด๋ฅผ ๋‚˜ํƒ€๋‚ด์ง€ ์•Š์•˜๋‹ค. SEM ์ด๋ฏธ์ง€ ์ดฌ์˜์„ ์œ„ํ•œ ์‹œํŽธ์˜ ํฌ๊ธฐ ํ•œ๊ณ„๋กœ ์ธํ•ด ๊ฐ•์„ฌ์œ ์˜ ๋ถ„ํฌ๋ฅผ ํŒŒ์•…ํ•˜๊ธฐ์—๋Š” ๋‹ค์†Œ ๋ฌด๋ฆฌ๊ฐ€ ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋˜ํ•œ, ๋™์ผํ•œ ๋ฐฐํ•ฉ์„ ๊ธฐ์ค€์œผ๋กœ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ๋งŒ์ด ๋ณ€์ˆ˜๋กœ ์‚ฌ์šฉ๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์— ์ˆ˜ํ™”๋ฌผ ์ƒํƒœ์—๋Š” ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 % ๊ฐ„์˜ ๋šœ๋ ทํ•œ ์ฐจ์ด๊ฐ€ ๋‚˜ํƒ€๋‚˜์ง€ ์•Š์•˜๋‹ค.

๋ณธ ์—ฐ๊ตฌ์—์„œ ์ ์šฉ๋œ ์—ด์‚ฌ์ดํด์€ 400 ยฐC์˜ ๊ณ ์˜จ์ด๋ฉฐ, ์ด ์˜จ๋„ ์˜์—ญ์€ ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์˜ ๋ถ„ํ•ด๋ฅผ ์œ ๋ฐœํ•  ์ˆ˜ ์žˆ๋‹ค(Zhai et al. 2014). ๋Œ€ํ‘œ์ ์œผ๋กœ ์ˆ˜์‚ฐํ™”์นผ์Š˜์˜ ๋ถ„ํ•ด๋กœ ์ธํ•œ ํ™”ํ•™์  ๊ฒฐํ•ฉ์ˆ˜์˜ ํƒˆ์ˆ˜์ด๋ฉฐ, ๊ณต๊ทน ๊ตฌ์กฐ์˜ ๋ณ€ํ™”๋ฅผ ์•ผ๊ธฐํ•œ๋‹ค. ๋”ฐ๋ผ์„œ, ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์—๋Š” U120 ๋ฐ U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์—์„œ ๊ณต๊ทน์˜ ์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์ด ์ •์„ฑ์ ์œผ๋กœ ๊ด€์ฐฐ๋˜์—ˆ๋‹ค.

Fig. 10 SEM image results of U120 series
../../Resources/KCI/JKCI.2023.35.4.421/fig10.png
Fig. 11 SEM image results of U180 series
../../Resources/KCI/JKCI.2023.35.4.421/fig11.png

4.2 ์—ด์ค‘๋Ÿ‰ ๋ถ„์„(TGA)

๊ณ ์˜จ์— ๋…ธ์ถœ๋œ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์˜ ๋ณ€ํ™”๋ฅผ ์•ผ๊ธฐ์‹œํ‚ค๋ฉฐ, ์—ญํ•™์  ๋ฐ ์—ด์  ํŠน์„ฑ์„ ์ €ํ•˜์‹œํ‚ค๋Š” ์š”์ธ์œผ๋กœ ์ž‘์šฉํ•œ๋‹ค. ์ด์— ๋ณธ ์—ฐ๊ตฌ์—์„œ ์„ค์ •ํ•œ ์—ด์‚ฌ์ดํด ์ ์šฉ์— ๋”ฐ๋ฅธ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ ๋ณ€ํ™” ํŠน์„ฑ์„ ํŒŒ์•…ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ตœ๋Œ€์˜จ๋„ 1,000 ยฐC, ์Šน์˜จ ์†๋„ 10 ยฐC/min์˜ ์กฐ๊ฑด์œผ๋กœ ์—ด์ค‘๋Ÿ‰ ๋ถ„์„(thermal gravity analysis, TGA) ๋ถ„์„์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ๋Œ€ํ‘œ์ ์œผ๋กœ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ 6ํšŒ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„, U120 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ TGA ์ธก์ • ๊ทธ๋ž˜ํ”„๋ฅผ Fig. 12 ๋ฐ Fig. 13์— ๋„์‹ํ™”ํ•˜์˜€์œผ๋ฉฐ, U120 ๋ฐ U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ TGA ์˜จ๋„ ๊ตฌ๊ฐ„๋ณ„ ์ค‘๋Ÿ‰ ๊ฐ์†Œ์™€ ์ด์ค‘๋Ÿ‰๊ฐ์†Œ ๊ฒฐ๊ณผ๋ฅผ Table 2์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์˜ ์‹คํ—˜๊ตฐ์€ 0~150 ยฐC ์˜จ๋„ ๊ตฌ๊ฐ„์—์„œ ๊ฐ๊ฐ 7.60, 7.01 ๋ฐ 6.53 %์˜ ๊ธ‰๊ฒฉํ•œ ์ค‘๋Ÿ‰ ๊ฐ์†Œ๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์ด๋Š” 0~150 ยฐC ์˜จ๋„ ๊ตฌ๊ฐ„์€ ํ‘œ๋ฉด์ˆ˜ ๋ฐ ๋ชจ์„ธ๊ด€์ˆ˜ ์ฆ๋ฐœ์— ์˜ํ•œ ์ค‘๋Ÿ‰ ๊ฐ์†Œ๊ฐ€ ์ฃผ๋œ ์ด์œ ์ด๋‹ค. ๋ฐ˜๋ฉด์— U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ์‹คํ—˜๊ตฐ์€ 0~150 ยฐC ์˜จ๋„ ๊ตฌ๊ฐ„์—์„œ ๊ฐ๊ฐ 1.13, 1.21 ๋ฐ 1.14 %๋กœ ์ธก์ •๋˜์—ˆ์œผ๋ฉฐ, ๋‹ค์†Œ ๋‚ฎ์€ ์ค‘๋Ÿ‰ ๊ฐ์†Œ๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด๋กœ ์ธํ•ด ์ˆ˜๋ถ„ ์ฆ๋ฐœ์ด ์„ ํ–‰๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์— ๋‚˜ํƒ€๋‚˜๋Š” ๊ฒฐ๊ณผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๋‹ค์Œ์˜ ์˜จ๋„ ๊ตฌ๊ฐ„์ธ 350~450 ยฐC์—์„œ๋Š” ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์ธ ์ˆ˜์‚ฐํ™”์นผ์Š˜์˜ ํƒˆ์ˆ˜๊ฐ€ ์ด๋ฃจ์–ด์ง€๋ฉฐ, U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์˜ ์‹คํ—˜๊ตฐ์€ ๊ฐ๊ฐ 1.21, 1.97 ๋ฐ 1.05 %, ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ์‹คํ—˜๊ตฐ์€ ๊ฐ๊ฐ 0.49, 0.48 ๋ฐ 0.43 %์˜ ์ค‘๋Ÿ‰ ๊ฐ์†Œ๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ค‘๋Ÿ‰ ๊ฐ์†Œ์œจ์ด ๋‚ฎ๋‹ค๋Š” ๊ฒƒ์€ ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด๋กœ ์ธํ•ด ์ˆ˜ํ™”๋ฌผ์ด ๋ถ„ํ•ด๋˜์–ด ์†Œ์‹ค๋œ ์–‘์ด ๋งŽ๋‹ค๋Š” ๊ฒƒ์„ ์˜๋ฏธํ•˜๋ฉฐ, 400 ยฐC์˜ ์—ด์‚ฌ์ดํด์„ ์ ์šฉํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์ด๋ฏธ ์ˆ˜ํ™”๋ฌผ์˜ ๋ถ„ํ•ด๊ฐ€ ์ผ๋ถ€ ์ง„ํ–‰๋˜์—ˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด๋กœ ์ธํ•ด ์—ด์‚ฌ์ดํด์„ ์ ์šฉํ•œ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰, ์••์ถ•๊ฐ•๋„ ๋ฐ ์—ด์ „๋„๋„์— ๋ถˆ๋ฆฌํ•œ ์˜ํ–ฅ์„ ์ค€ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

600~750 ยฐC ์˜จ๋„ ๊ตฌ๊ฐ„์€ ํƒ„์‚ฐ์นผ์Š˜์˜ ํƒˆํƒ„์‚ฐ์ด ๋‚˜ํƒ€๋‚˜๋Š” ๊ตฌ๊ฐ„์ด๋ฉฐ, U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์˜ ์‹คํ—˜๊ตฐ์€ ๊ฐ๊ฐ 7.11, 7.02 ๋ฐ 7.52 %, ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ์‹คํ—˜๊ตฐ์€ ๊ฐ๊ฐ 8.19, 7.44 ๋ฐ 7.45 %์˜ ์ค‘๋Ÿ‰ ๊ฐ์†Œ๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. 350~450 ยฐC ์˜จ๋„ ๊ตฌ๊ฐ„๋ณด๋‹ค ์ƒ๋Œ€์ ์œผ๋กœ ๋†’์€ ์ค‘๋Ÿ‰ ๊ฐ์†Œ์œจ์„ ๋‚˜ํƒ€๋ƒˆ์œผ๋ฉฐ, ์ ์šฉ ์—ด์‚ฌ์ดํด์˜ ์˜จ๋„์ธ 400 ยฐC ์กฐ๊ฑด์œผ๋กœ ์ธํ•ด 600~750 ยฐC์—์„œ ์ด๋ฃจ์–ด์ง€๋Š” ์ˆ˜ํ™”๋ฌผ ๋ถ„ํ•ด์— ์ค€ ์˜ํ–ฅ์€ ๋‹ค์†Œ ๋ฏธ๋น„ํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

์ด ์ค‘๋Ÿ‰ ๊ฐ์†Œ ๋น„๊ต์—์„œ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„, U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ๊ฒฝ์šฐ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ๊ฐ๊ฐ 9.81, 9.13 ๋ฐ 9.02 %, U180 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์—์„œ๋Š” ๊ฐ๊ฐ 2.27, 2.80 ๋ฐ 2.27 %๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ U120 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋ณด๋‹ค ํ‰๊ท  73.7 % ๋‚ฎ์€ ์ด ์ค‘๋Ÿ‰ ๊ฐ์†Œ๊ฐ€ ๋„์ถœ๋˜์—ˆ๋‹ค. ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด์„ ์ ์šฉํ•œ ํ›„์˜ ์ค‘๋Ÿ‰์˜ ๋ณ€ํ™”๊ฐ€ ๋‚ฎ๋‹ค๋Š” ๊ฒƒ์€ ๊ณ ์˜จ์— ์˜ํ•œ ์•…์˜ํ–ฅ์ด ์ ๋‹ค๋Š” ๊ฒƒ์„ ์˜๋ฏธํ•˜๋ฉฐ, ๊ณ ์˜จ ์•ˆ์ •์„ฑ ๋ฐ ๋‚ด๊ตฌ์„ฑ ํ™•๋ณด์— ๋งค์šฐ ์œ ๋ฆฌํ•œ ์กฐ๊ฑด์ž„์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

๋™์ผ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์—์„œ๋Š” U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ U120 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋ณด๋‹ค ์—ด์ค‘๋Ÿ‰ ์ด๊ฐ์†Œ๋Ÿ‰์ด ์ƒ๋Œ€์ ์œผ๋กœ ๋‚ฎ๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ฐ•๋„๊ฐ€ ๋†’์„์ˆ˜๋ก ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด์„ ์ˆ˜ํ–‰ํ•˜๋”๋ผ๋„ ์‹œํŽธ์— ์กด์žฌํ•˜๋Š” ์ˆ˜๋ถ„์˜ ์ฆ๋ฐœ ๋˜๋Š” ์ˆ˜ํ™”๋ฌผ์˜ ๋ถ„ํ•ด๋กœ ์ธํ•ด ๊ฐ์†Œํ•˜๋Š” ์–‘์ด ์ ์–ด ๋‚ด๊ตฌ์„ฑ ์ €ํ•˜์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์ด ์ƒ๋Œ€์ ์œผ๋กœ ๋‚ฎ๋‹ค๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 12 Thermogravimetric analysis results of U120 series (steel fiber content=1.0 %)
../../Resources/KCI/JKCI.2023.35.4.421/fig12.png
Fig. 13 Thermogravimetric analysis results of U120 series (steel fiber content=2.0 %)
../../Resources/KCI/JKCI.2023.35.4.421/fig13.png
Table 2 Thermogravimetric analysis test results

Specimen series

Steel fiber content

(%)

State

Temperature range (ยฐC)

Total loss

(%)

0~150

350~450

550~750

Weight loss rate (%)

U120

1.0

Initial state

7.60

1.21

7.11

15.92

1.5

7.01

1.97

7.02

16.00

2.0

6.53

1.05

7.52

15.10

1.0

After 6 thermal cycles

1.13

0.49

8.19

9.81

1.5

1.21

0.48

7.44

9.13

2.0

1.14

0.43

7.45

9.02

U180

1.0

Initial state

3.28

0.42

1.38

5.08

1.5

4.19

0.67

1.95

6.81

2.0

3.61

0.58

1.74

5.93

1.0

After 6 thermal cycles

0.79

0.17

1.31

2.27

1.5

0.89

0.16

1.75

2.80

2.0

0.72

0.20

1.35

2.27

5. ๊ฒฐ ๋ก 

๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ๊ณ ์˜จ์˜ ์—ด์—๋„ˆ์ง€ ์ €์žฅ๋งค์ฒด๋กœ ํ™œ์šฉํ•˜๊ธฐ ์œ„ํ•œ ์žฌ๋ฃŒํŠน์„ฑ์— ๊ด€ํ•œ ์‹คํ—˜์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ, ์ฃผ์š” ๊ฒฐ๋ก ์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

1) 3ํšŒ ์ด์ƒ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ๋ถ€ํ„ฐ๋Š” ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‹จ์œ„์ค‘๋Ÿ‰์˜ ๋ณ€ํ™”๋Š” ๊ฑฐ์˜ ์ผ์ •ํ•˜๋ฉฐ, ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ๋ฐ˜๋ณต์ ์ธ ๊ณ ์˜จ ๋…ธ์ถœ์— ๋Œ€ํ•œ ๋ฌผ๋ฆฌ์  ์•ˆ์ •์„ฑ์— ๋„๋‹ฌํ•˜๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋˜ํ•œ, U120 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋ณด๋‹ค U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์œ„์ค‘๋Ÿ‰์ด ๋‹ค์†Œ ํฌ์ง€๋งŒ, ๊ทธ ์ฐจ์ด๋Š” ๋งค์šฐ ๊ทผ์†Œํ•˜๋‹ค. ๋”ฐ๋ผ์„œ, ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ„์˜ ์—ด์šฉ๋Ÿ‰ ์„ฑ๋Šฅ์— ํฐ ์ฐจ์ด๊ฐ€ ์—†์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

2) ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „๊ณผ ํ›„์˜ ์••์ถ•๊ฐ•๋„ ๊ฐ์†Œ์œจ์€ U120 ์‹œ๋ฆฌ์ฆˆ๋ณด๋‹ค U180 ์‹œ๋ฆฌ์ฆˆ๊ฐ€ ์•ฝ 2๋ฐฐ ์ •๋„ ๋งŽ์ด ๊ฐ์†Œํ•œ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์‹ค์งˆ์ ์ธ ์••์ถ•๊ฐ•๋„๋Š” U120 ์‹œ๋ฆฌ์ฆˆ๋ณด๋‹ค ๋†’์œผ๋ฉฐ, ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ  1.0, 1.5 ๋ฐ 2.0 %์—์„œ ๊ฐ๊ฐ 187.3, 188.6 ๋ฐ 193.3 MPa๋กœ ์šฐ์ˆ˜ํ•œ ์••์ถ•๊ฐ•๋„ ์„ฑ๋Šฅ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

3) ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ, U120 ์‹œ๋ฆฌ์ฆˆ ์‹œํŽธ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„๋Š” ๊ฐ๊ฐ 8.9, 10.7 ๋ฐ 11.4 MPa์ด๊ณ , U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„๋Š” ๊ฐ๊ฐ 10.3, 12.8 ๋ฐ 13.8 MPa์ด๋‹ค. ๊ณ ์˜จ ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์ž”๋ฅ˜ ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„๋Š” ํŠน์„ฑ์€ ๋งค์šฐ ์šฐ์ˆ˜ํ•˜๋ฉฐ, ์—ด์‘๋ ฅ์— ์˜ํ•œ ์˜ํ–ฅ์—์„œ ๋”์šฑ ์šฐ์ˆ˜ํ•œ ์„ฑ๋Šฅ์„ ๋‚˜ํƒ€๋‚ด๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

4) ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด 1.0, 1.5 ๋ฐ 2.0 %์ผ ๋•Œ, U180 ์‹œ๋ฆฌ์ฆˆ์˜ ์—ด์ „๋„๋„๋Š” U120 ์‹œ๋ฆฌ์ฆˆ์˜ ์—ด์ „๋„๋„๋ณด๋‹ค ์—ด์‚ฌ์ดํด ์ ์šฉ ์ „์— ๊ฐ๊ฐ 26.6, 26.1 ๋ฐ 28.5 % ์ฆ๊ฐ€ํ•˜๊ณ , ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์— ๊ฐ๊ฐ 41.7, 39.4 ๋ฐ 43.3 % ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ๋”ฐ๋ผ์„œ, U180 ์‹œ๋ฆฌ์ฆˆ ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์น˜๋ฐ€ํ•œ ๋งคํŠธ๋ฆญ์Šค ๊ตฌ์กฐ๋กœ ์ธํ•ด ์—ด์ „๋„๋„ ์„ฑ๋Šฅ ํ™•๋ณด์— ๋งค์šฐ ์œ ๋ฆฌํ•˜๋‹ค.

5) ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์••์ถ•๊ฐ•๋„, ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„ ๋ฐ ์—ด์ „๋„๋„ ํŠน์„ฑ์€ ํ–ฅ์ƒ๋˜์ง€๋งŒ, ๋น„์—ด์€ ๊ฐ์†Œํ•œ๋‹ค. ๋น„์—ด์˜ ๊ฐ์†Œ๋Š” ์—ด์šฉ๋Ÿ‰ ๊ฐ์†Œ๋ฅผ ์œ ๋ฐœํ•˜์ง€๋งŒ, ์ดˆ๊ณ ์„ฑ๋Šฅ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ณ ์˜จ ๋…ธ์ถœ์—์„œ ๋†’์€ ๋‹จ์œ„์ค‘๋Ÿ‰, ์ชผ๊ฐฌ์ธ์žฅ๊ฐ•๋„์™€ ์—ด์ „๋„๋„ ํ™•๋ณด๋ฅผ ํ†ตํ•ด ์—ด์—๋„ˆ์ง€ ์ €์žฅ ๋งค์ฒด ์—ญํ• ์„ ๊ธฐ๋Œ€ํ•  ์ˆ˜ ์žˆ๋‹ค.

6) SEM ๋ถ„์„๊ฒฐ๊ณผ๋Š” ์—ด์‚ฌ์ดํด ์ ์šฉ ํ›„์˜ UHPC ๊ณต๊ทน์ด ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๋˜ํ•œ, TGA ๋ถ„์„์—์„œ ๋™์ผ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์ผ ๋•Œ, U180์˜ ์ด ์—ด์ค‘๋Ÿ‰ ๊ฐ์†Œ์œจ์ด U120๋ณด๋‹ค ์ƒ๋Œ€์ ์œผ๋กœ ๋‚ฎ๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋”ฐ๋ผ์„œ, ์—ญํ•™์  ํŠน์„ฑ์ด ๋†’์„์ˆ˜๋ก ๊ณ ์˜จ์˜ ์—ด์‚ฌ์ดํด ์ ์šฉ ์กฐ๊ฑด์—์„œ ์ˆ˜๋ถ„ ์ฆ๋ฐœ ๋ฐ ์ˆ˜ํ™”๋ฌผ ๋ถ„ํ•ด(dehydration) ์˜ํ–ฅ์ด ์ ์–ด์„œ ๋‚ด๊ตฌ์„ฑ ์ €ํ•˜์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์ด ๋‚ฎ์€ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

๋ณธ ์—ฐ๊ตฌ๋Š” ํ•œ๊ตญ๊ธฐ๊ณ„์—ฐ๊ตฌ์› ๊ธฐ๋ณธ์‚ฌ์—… โ€œํ™”์„์—ฐ๋ฃŒ ๋Œ€์ฒด๋ฅผ ์œ„ํ•œ 300 ยฐC๊ธ‰ ๊ณ ์˜จ ํžˆํŠธํŽŒํ”„ ์‹œ์Šคํ…œ ๊ฐœ๋ฐœโ€์˜ ์ง€์›์œผ๋กœ ์ˆ˜ํ–‰๋˜์—ˆ์Šต๋‹ˆ๋‹ค.

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