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Journal of the Korea Concrete Institute

J Korea Inst. Struct. Maint. Insp.
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  • Korea Citation Index (KCI)

  1. ์ •ํšŒ์›,๊ฑด์–‘๋Œ€ํ•™๊ต ๊ณต๊ณต์•ˆ์ „์—ฐ๊ตฌ์†Œ ์—ฐ๊ตฌ๊ต์ˆ˜
  2. ์ •ํšŒ์›,๊ฑด์–‘๋Œ€ํ•™๊ต ์žฌ๋‚œ์•ˆ์ „๊ณตํ•™๊ณผ ์„์‚ฌ๊ณผ์ •
  3. ์ •ํšŒ์›,๊ฑด์–‘๋Œ€ํ•™๊ต ์žฌ๋‚œ์•ˆ์ „๊ณตํ•™๊ณผ ์„์‚ฌ๊ณผ์ •
  4. ์ •ํšŒ์›,๊ฑด์–‘๋Œ€ํ•™๊ต ์žฌ๋‚œ์•ˆ์ „๊ณตํ•™๊ณผ ์„์‚ฌ๊ณผ์ •
  5. ์ •ํšŒ์›,๊ฑด์–‘๋Œ€ํ•™๊ต ํ•ด์™ธ๊ฑด์„คํ”Œ๋ž˜ํŠธํ•™๊ณผ ๊ต์ˆ˜



ํƒ„์†Œ์„ฌ์œ , ๊ฐ•์„ฌ์œ , ๋น„์ €ํ•ญ, ์นจํˆฌ ์ž„๊ณ„์ , SEM/EDS(์ฃผ์‚ฌ์ „์žํ˜„๋ฏธ๊ฒฝ/์—๋„ˆ์ง€ ๋ถ„์‚ฐํ˜• X-ray ๋ถ„๊ด‘๋ถ„์„๊ธฐ)
Carbon fiber, Steel fiber, Resistivity, Percolation threshold, SEM/EDS(scanning electron microscope/energy disperse X-ray spectrometer)

1. ์„œ ๋ก 

ํ˜„๋Œ€ ์žฌ๋ฃŒ๊ณผํ•™์˜ ๊ธฐ์ˆ ๋ฐœ๋‹ฌ๊ณผ ํ•จ๊ป˜ ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด๋Š” ๋‹ค์–‘ํ•œ ์‚ฌํšŒ์  ๊ธฐ๋Šฅ์„ ๋งŒ์กฑ์‹œํ‚ค๊ธฐ ์œ„ํ•˜์—ฌ ์ƒˆ๋กœ์šด ๊ธฐ๋Šฅ์„ ๋ถ€์—ฌํ•œ ๋งŽ์€ ๊ฑด์„ค์žฌ๋ฃŒ๊ฐ€ ๊ฐœ๋ฐœ๋˜์—ˆ๋‹ค. ๊ทธ๋ฆฌ๊ณ  ์˜ค๋Š˜๋‚  ์‹œ์žฅ์ด ์š”๊ตฌํ•˜๋Š” ๋‹ค๊ธฐ๋Šฅ์„ฑ ์„ฌ์œ ๋ณด๊ฐ• ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด(fiber-reinforced cement mortar, FRCM)์˜ ๊ฐœ๋ฐœ์„ ์œ„ํ•ด ์—ญํ•™์  ์„ฑ๋Šฅ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ์ „๊ธฐ์  ํŠน์„ฑ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ๋‹ค์–‘ํ•œ ์ธก๋ฉด์—์„œ ์ˆ˜ํ–‰๋˜๊ณ  ์žˆ๋‹ค.(ACI Committee 544, 2018; Balli et al., 2020; Brandt, 2008). ์ผ๋ฐ˜์ ์œผ๋กœ ์ „๊ธฐ๊ฐ€ ํ†ตํ•˜์ง€ ๋ชปํ•˜๊ฒŒ ๋˜๋Š” ๋ถ€๋„์ฒด์˜ ์ „๊ธฐ์  ํŠน์„ฑ์„ ๊ฐ–๊ณ  ์žˆ๋Š” ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์— ์ „๊ธฐ์ „๋„์„ฑ(์ดํ•˜, ์ „๋„์„ฑ์ด๋ผ ํ•จ)์„ ๋ถ€์—ฌํ•˜๊ฒŒ ๋˜๋ฉด FRCM์˜ ์‘์šฉ๋ถ„์•ผ๋ฅผ ๋‹ค๋ฐฉ๋ฉด์œผ๋กœ ํ™•๋Œ€ํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์ƒˆ๋กœ์šด ์ˆ˜์š”์˜ ์ฐฝ์ถœ๋„ ๊ฐ€๋Šฅํ•  ๊ฒƒ์œผ๋กœ ๊ธฐ๋Œ€๋œ๋‹ค.

์•„์šธ๋Ÿฌ, ์ „๊ธฐ์ €ํ•ญ ๋ฐฉ๋ฒ•์€ 1980๋…„๋Œ€ ํ›„๋ฐ˜๋ถ€ํ„ฐ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ํŠน์„ฑ ๊ฒ€ํ† ์— ์ ์šฉ๋˜๊ธฐ ์‹œ์ž‘ํ•˜์—ฌ, ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋ฏธ์„ธ๊ตฌ์กฐ ๋ถ„์„ ๋ฐ ์ „๊ธฐ์  ํŠน์„ฑ์— ๋Œ€ํ•ด ๋‹ค์–‘ํ•˜๊ฒŒ ์—ฐ๊ตฌ๊ฐ€ ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค(Lee and Lim, 2018; McCarter et al., 2000). ํŠนํžˆ ๋†’์€ ๊ธฐ๊ณ„์  ๋ฌผ์„ฑ, ์ „๋„์„ฑ, ๋‚ด์—ด์„ฑ, ๋ถˆ์—ฐ์„ฑ ๋ฐ ๋‚ด๋ถ€์‹์„ฑ ๋“ฑ์˜ ์šฐ์ˆ˜ํ•œ ํŠน์„ฑ์„ ๊ฐ–๋Š” ํƒ„์†Œ์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ์ „๊ธฐ์  ํŠน์„ฑ์„ ๋ถ€์—ฌํ•˜๊ฒŒ ๋˜๋ฉด, ์ „๊ธฐ์ €ํ•ญ์„ ์ผ์ • ์ˆ˜์ค€์œผ๋กœ ํฌ๊ฒŒ ๋‚ฎ์ถ”๋ฏ€๋กœ ์ž์ฒด๊ฐ์ง€(self-sensing) ๋ฐ ์ž์ฒด ๋ชจ๋‹ˆํ„ฐ๋ง(self-monitoring), ๊ตํ†ต ๋ชจ๋‹ˆํ„ฐ๋ง(traffic monitoring), ์ œ๋น™(deicing), ์ฒ ๊ทผ์˜ ๋ถ€์‹๋ฐฉ์ง€(corrosion protection of rebar), ์ ‘์ง€์ €ํ•ญ ์ €๊ฐ์žฌ(electrical grounding) ๋ฐ ์ „์žํŒŒ ์ฐจํ์žฌ๋ฃŒ(electro magnetic shielding) ๋“ฑ๊ณผ ๊ฐ™์€ ๋ฐœ์ „๋œ ๊ธฐ์ˆ ๊ฐœ๋ฐœ์ด ์ถ”์ง„๋˜๊ณ  ์žˆ๋‹ค(Chiarello and Zinno, 2005; Han et al., 2015; Yildirim et al., 2020).

๊ตญ๋‚ด์˜ ๊ฒฝ์šฐ ์ „๋„์„ฑ ์žฌ๋ฃŒ์ธ ํƒ„์†Œ์„ฌ์œ (carbon fiber, CF)์™€ ๊ฐ•์„ฌ์œ (steel fiber, SF)๊ฐ€ ํ•จ์œ ๋œ ํƒ„์†Œ์„ฌ์œ  ๋ณด๊ฐ•์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด(carbon fiber-reinforced cement mortar, CFRCM)์™€ ๊ฐ•์„ฌ์œ  ๋ณด๊ฐ•์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด(steel fiber-reinforced cement mortar, SFRCM)์— ๋Œ€ํ•œ ๋งŽ์€ ์—ฐ๊ตฌ๊ฐ€ ๋‹ค์ˆ˜ ์ง„ํ–‰๋˜์–ด ์™”์œผ๋ฉฐ, ๋Ÿฌ์‹œ์•„, ๋ถ๋ฏธ ๋ฐ ์ผ๋ณธ ๋“ฑ ์ผ๋ถ€ ์™ธ๊ตญ์—์„œ๋Š” ๊ฑด์„ค์šฉ ์ฒจ๋‹จ ์‹ ์†Œ์žฌ(ํƒ„์†Œ)๋กœ ์ ๊ทน์ ์ธ ๊ธฐ์ˆ ๊ฐœ๋ฐœ์„ ํ•จ์œผ๋กœ์จ ๊ทธ ํ™œ์šฉ์„ฑ์„ ์ œ๊ณ ์‹œํ‚ค๊ณ  ์žˆ๋‹ค. ํ•˜์ง€๋งŒ ์—ฌ๋Ÿฌ ๊ฐ€์ง€ ์ „๊ธฐ์ €ํ•ญ ์ธก์ •๋ฐฉ๋ฒ•์ด ๊ฐœ๋ฐœ๋˜์–ด ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์  ํŠน์„ฑ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๋Š” ํ™œ๋ฐœํ•˜๊ฒŒ ์ง„ํ–‰๋˜๊ณ  ์žˆ์œผ๋‚˜(Lim, 2018; Yoon, 2013) ์ „๊ธฐ์ €ํ•ญ์„ ํ™œ์šฉํ•œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๊ธฐ์ค€์ด๋‚˜ ํŠน์„ฑํ‰๊ฐ€์— ๋Œ€ํ•ด ์•„์ง ๋ฏธ๋น„ํ•œ ์ƒํ™ฉ์ด๋‹ค. ๋ณธ ์—ฐ๊ตฌ์˜ ์ฃผ์š” ๋ชฉ์ ์€ ์ „๋„์„ฑ ์„ฌ์œ ๊ฐ€ ํ•จ์œ ๋œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋ฏธ์„ธ๊ตฌ์กฐ ๋ฐ ์ „๊ธฐ์  ํŠน์„ฑ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ์กฐ์‚ฌํ•˜๊ธฐ ์œ„ํ•จ์ด๋‹ค.

๋”ฐ๋ผ์„œ ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ „๋„์„ฑ ์žฌ๋ฃŒ์ธ ํƒ„์†Œ์„ฌ์œ ์™€ ๊ฐ•์„ฌ์œ ๊ฐ€ ํ•จ์œ ๋œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋ฏธ์„ธ๊ตฌ์กฐ ๋ฐ ์ „๊ธฐ์  ํŠน์„ฑ, ์••์ถ•๊ฐ•๋„์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ์กฐ์‚ฌํ•˜๊ธฐ ์œ„ํ•ด ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์„ ๋‹ฌ๋ฆฌํ•˜์—ฌ ์‹œํŽธ์„ ์ œ์ž‘ํ•˜๊ณ , ๋‹ค์–‘ํ•œ ์–‘์ƒ์žฌ๋ น(3, 7, 14, 28, 56 ๋ฐ 90์ผ)์—์„œ ์ „๊ธฐ์ €ํ•ญ๊ณผ ์••์ถ•๊ฐ•๋„๋ฅผ ์ธก์ •ํ•˜์—ฌ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์™€ ๋น„๊ต, ๊ฒ€ํ† ์ฝ”์ž ํ•˜์˜€๋‹ค. ์•„์šธ๋Ÿฌ, ์ „๋„์„ฑ FRCM ํŒŒ๋‹จ๋ฉด์˜ ๋ฏธ์„ธ๊ตฌ์กฐ๋ฅผ ๊ด€์ฐฐํ•˜๊ธฐ ์œ„ํ•ด ์ฃผ์‚ฌ์ „์žํ˜„๋ฏธ๊ฒฝ(scanning electron microscope, SEM)๊ณผ ์—๋„ˆ์ง€ ๋ถ„์‚ฐ X์„  ๋ถ„๊ด‘๊ธฐ(energy-dispersive X-ray spectrometer, EDS)๋ฅผ ํ†ตํ•ด ๋ถ„์„์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

2. ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์  ํŠน์„ฑ ๋ฐ ์นจํˆฌ ์ž„๊ณ„์ 

2.1 ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์  ํŠน์„ฑ

์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด๋ž€ ์‹œ๋ฉ˜ํŠธ, ์ž”๊ณจ์žฌ, ๋ฌผ ๋ฐ ํ˜ผํ™”์žฌ๋ฃŒ ๋“ฑ์„ ์ผ์ •ํ•œ ๋ฐฐํ•ฉ๋น„๋กœ ํ˜ผํ•ฉํ•˜์—ฌ ๋งŒ๋“œ๋Š” ๊ฑด์„ค์žฌ๋ฃŒ์ด๋ฉฐ, ๋งค์šฐ ๋†’์€ ์ „๊ธฐ์ €ํ•ญ์„ ๊ฐ€์ง€๋ฏ€๋กœ ์ „๋„์„ฑ์ด ๋งค์šฐ ๋‚ฎ๋‹ค. ์ด๋Ÿฌํ•œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์— ์ „๋„์„ฑ ์žฌ๋ฃŒ๋ฅผ ํ˜ผ์ž…ํ•˜๋ฉด ์ „๋„์„ฑ์ด ๊ฐœ์„ ๋˜์–ด ์ „๊ธฐ์ €ํ•ญ์˜ ๊ฐ์†Œ๊ฐ€ ๋ฐœ์ƒํ•œ๋‹ค. ์ด๋ ‡๊ฒŒ ํ•˜์—ฌ ์ œ์กฐ๋œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์–‘๋‹จ์— ์ „๊ทน์„ ํ†ตํ•ด ์ „๋ฅ˜๋ฅผ ํ˜๋Ÿฌ์ฃผ๊ฒŒ ๋˜๋ฉด ์ด๋ฅธ๋ฐ” ์ „๊ธฐ๊ฐ€ ํ†ตํ•˜๋Š” ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด๊ฐ€ ๊ฐ€๋Šฅํ•˜๊ฒŒ ๋œ๋‹ค. Fig. 1์€ ๊ฐ์ข… ์žฌ๋ฃŒ์˜ ๋น„์ €ํ•ญ ๋ฒ”์œ„๋ฅผ ๋„์ฒด, ๋ฐ˜๋„์ฒด ๋ฐ ๋ถ€๋„์ฒด(์ ˆ์—ฐ์ฒด)๋กœ ๊ตฌ๋ถ„ํ•˜์—ฌ ๋น„์ €ํ•ญ ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ์ „๊ธฐ์  ๋ถ€๋„์ฒด์ธ ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด๋Š” ์•ฝ 106โˆผ10 โ„ฆยทm ๋ฒ”์œ„์˜ ๋น„์ €ํ•ญ ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ด๋Š” ๋ฐ˜๋ฉด, ์ „๊ธฐ์  ๋„์ฒด์ธ ๊ธˆ์†์žฌ๋ฃŒ๋‚˜ ๊ฒŒ๋ฅด๋งˆ๋Š„, ์‹ค๋ฆฌ์ฝ˜๊ณผ ๊ฐ™์€ ๋ฐ˜๋„์ฒด์˜ ๊ฒฝ์šฐ 1.59ร—10โˆ’8 โˆผ2.5ร—102 โ„ฆยทm ๋ฒ”์œ„์˜ ๋น„์ €ํ•ญ ํŠน์„ฑ์„ ๊ฐ–๊ณ  ์žˆ๋‹ค. ํ•˜์ง€๋งŒ ํƒ„์†Œ๊ณ„์˜ ์„ฌ์œ ๋Š” 10โˆ’1โˆผ10โˆ’2 โ„ฆยทm ๋ฒ”์œ„์˜ ๋น„์ €ํ•ญ ํŠน์„ฑ์„ ๊ฐ€์ง„๋‹ค๊ณ  ์•Œ๋ ค์ ธ ์žˆ๋‹ค(Kang, 1998; Chung, 2004). ๋”ฐ๋ผ์„œ ์—ฌ๋Ÿฌ ๊ฐ€์ง€ ์žฌ๋ฃŒ์˜ ๋น„์ €ํ•ญ์„ ๋น„๊ตํ•˜์˜€์„ ๋•Œ, ์ „๋„์„ฑ ์žฌ๋ฃŒ์ธ ํƒ„์†Œ์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•˜์—ฌ ์ œ์กฐํ•  ๊ฒฝ์šฐ ๊ธฐ๋ณธ์ ์œผ๋กœ ๋ถ€๋„์ฒด์ธ ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋น„์ €ํ•ญ์„ 101 โ„ฆยทm ์ˆ˜์ค€์œผ๋กœ ํฌ๊ฒŒ ๋‚ฎ์ถ”์–ด ์ „๋„์„ฑ์„ ๊ฐ–๋Š” ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋ณ€ํ™˜์ด ๊ฐ€๋Šฅํ•˜๋‹ค.

Fig. 1 Typical resistivity range for various materials
../../Resources/ksm/jksmi.2022.26.3.72/fig1.png

2.2 ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ €ํ•ญ ์ธก์ •

์ผ๋ฐ˜์ ์œผ๋กœ ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ €ํ•ญ ์ธก์ •๋ฐฉ๋ฒ•์€ 2-probe(two probe method)์™€ 4-probe(four probe method) ๋ฐฉ๋ฒ•์ด ์‚ฌ์šฉ๋˜๊ณ  ์žˆ๋‹ค. ๋น„๋ก 2-probe ๋ฐฉ๋ฒ•์˜ ํšŒ๋กœ๊ฐ€ ๋” ๊ฐ„๋‹จ ํ•˜์ง€๋งŒ ์‹œํŽธ๊ณผ ์ „๊ทน ์‚ฌ์ด์˜ ์ ‘์ด‰์ €ํ•ญ์„ ํฌํ•จํ•˜์ง€ ์•Š๊ธฐ ๋•Œ๋ฌธ์— 4-probe ๋ฐฉ๋ฒ•์ด ์„ ํ˜ธ๋˜๊ณ  ์žˆ๋‹ค(Han et al., 2007; Kang et al., 2018; Lee et al., 2019). 2-probe ๋ฐฉ๋ฒ•์€ ์ „๋ฅ˜๊ณ„์™€ ์ „์••๊ณ„์— ์—ฐ๊ฒฐํ•˜๋Š” ์ „๊ทน(extrode) 2๊ฐœ๋กœ ๊ตฌ์„ฑ๋˜์–ด ์žˆ์œผ๋ฉฐ, ์ „์••์„ ์ธก์ •ํ•˜๋Š” ์ „๋ฅ˜์—๋„ ์ „๋ฅ˜๊ฐ€ ํ๋ฅธ๋‹ค. 4-probe ๋ฐฉ๋ฒ•์€ ๋“ฑ ๊ฐ„๊ฒฉ์œผ๋กœ ์ผ๋ ฌ๋กœ ๋‚˜์—ดํ•œ 4๊ฐœ์˜ ์ „๊ทน์„ ์‚ฌ์šฉํ•˜๋ฉฐ, ๋ฐ”๊นฅ์ชฝ์— ํ•œ์Œ์˜ ์ „๊ทน๊ณผ ์•ˆ์ชฝ์— ํ•œ์Œ์˜ ์ „๊ทน, ์ฆ‰ ๋‘ ์Œ์˜ ์ „๊ทน์ด ์žˆ๋‹ค. ๋ฐ”๊นฅ์ชฝ ํ•œ์Œ์˜ ์ „๊ทน์„ ํ†ตํ•ด ์ผ์ •ํ•œ ์ „๋ฅ˜๋ฅผ ํ˜๋Ÿฌ์ฃผ๊ณ  ์•ˆ์ชฝ ํ•œ์Œ์˜ ์ „๊ทน์—์„œ ์ „๋ฅ˜๊ณต๊ธ‰์œผ๋กœ ์ธํ•ด ๋ฐœ์ƒํ•œ ์ „์••์˜ ์ฐจ์ด๋ฅผ ์ธก์ •ํ•œ๋‹ค. Fig. 2๋Š” ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์—์„œ 2-probe์™€ 4-probe์˜ ๊ธฐ๋ณธ์ ์ธ ์ „๊ธฐ์ €ํ•ญ ์ธก์ •๋ฐฉ๋ฒ•์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Fig. 2์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ 2-probe์™€ 4-probe ๋ฐฉ๋ฒ•์„ ํ™œ์šฉํ•˜์—ฌ ์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ €ํ•ญ(R)์€ ์ „์••(V)์™€ ์ „๋ฅ˜(I)๋ฅผ ์ธก์ •ํ•˜์—ฌ ์˜ด์˜ ๋ฒ•์น™์„ ์ด์šฉํ•˜์—ฌ ์‹ (1)์— ์˜ํ•˜์—ฌ ๊ฒฐ์ •๋œ๋‹ค.

(1)
R=VI=ฯLA

์—ฌ๊ธฐ์„œ, ฯ๋Š” ๊ณ ์œ ๋น„์ €ํ•ญ(โ„ฆยทใŽ)์ด๋ฉฐ, A๋Š” ์ „๊ทน์ด ์ ‘์ด‰ํ•œ ๋ถ€๋ถ„์˜ ๋ฉด์ (ใŽ )์ด๋ฉฐ, L์€ ์ „๊ทน๊ณผ ์ „๊ทน ์‚ฌ์ด์˜ ๊ฐ„๊ฒฉ(ใŽ)์ด๋‹ค.

Fig. 2 Sketch maps of 2-probe method and 4-probe method in cement composites
../../Resources/ksm/jksmi.2022.26.3.72/fig2.png

2.3 ์นจํˆฌ ์ž„๊ณ„์ 

์นจํˆฌ(percolation) ์ด๋ก ์€ ์‹œ์Šคํ…œ ๋‚ด๋ถ€์˜ ์ž„์˜์˜(random) ์š”์†Œ(element)๋“ค์˜ ์—ฐ๊ฒฐ์„ฑ(connectivity)์„ ๋ถ„์„ํ•˜๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ, ์ž„์˜์˜ ์‹œ์Šคํ…œ ๋‚ด๋ถ€์— ๋ถ„ํฌ๋œ ์š”์†Œ๋“ค์ด ์„œ๋กœ ์—ฐ๊ฒฐ๋˜์–ด ๋‚ด๋ถ€๋ฅผ ํ†ต๊ณผํ•  ์ˆ˜ ์žˆ๋Š” ํ†ต๋กœ๋ฅผ ๋งŒ๋“ค ์ˆ˜ ์žˆ๋Š” ๊ฑฐ๋Œ€ ์—ฐ๊ฒฐ์š”์†Œ๊ฐ€ ํ˜•์„ฑ๋˜๋Š” ๊ฒƒ์„ ์˜๋ฏธํ•œ๋‹ค. ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค ๋‚ด์— ์ „๋„์„ฑ ์„ฌ์œ ๋ฅผ ๋ถ„์‚ฐ์‹œํ‚ด์œผ๋กœ์จ, ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด ํ˜•์„ฑํ•˜๋Š” ๊ฒƒ์ด ๊ฐ€๋Šฅํ•˜๋‹ค. ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์„โ€œ0%โ€์—์„œ ์‹œ์ž‘ํ•˜์—ฌ ์ ์ฐจ ์ฆ๊ฐ€์‹œ์ผœ ๊ฐˆ ๋•Œ ์ผ์ • ๋ถ€ํ”ผ ๋ถ„์œจ ์ด์ƒ์ด ๋˜๋ฉด ์„ฌ์œ ๋“ค๋ผ๋ฆฌ์˜ ์—ฐ๊ฒฐ์ด ์™„์ „ํ•ด์ ธ์„œ ์ „์ž๋“ค์ด ์„ฌ์œ  ์‚ฌ์ด์˜ ๋ถ€๋„์ฒด ์˜์—ญ์„ Hopping ํ•˜๋ฉด์„œ ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค์— ์ „๋„์„ฑ์ด ์ƒ๊ธฐ๊ฒŒ ๋œ๋‹ค. ์ด๋ ‡๊ฒŒ ๋ถ€๋„์ฒด๊ฐ€ ๋„์ฒด๋กœ ๋ฐ”๋€Œ๋Š” ๊ฒƒ์„ ์นจํˆฌ๋ผํ•˜๋ฉฐ, ์นจํˆฌ๊ฐ€ ์‹œ์ž‘๋˜๋Š” ์‹œ์  ๋˜๋Š” ์ด ์‹œ์ ์—์„œ์˜ ์„ฌ์œ ์˜ ์ƒํƒœ๋Ÿ‰์„ ์นจํˆฌ ์ž„๊ณ„์ (percolation threshold)์ด๋ผ ํ•œ๋‹ค(Xie, et al., 1996). ์ฆ‰, ์นจํˆฌ ์ž„๊ณ„์ ์ด๋ž€ ๊ทผ์ ‘ํ•œ ์ „๋„์„ฑ ๋‚ด๋ถ€ ์„ฌ์œ ๋“ค ๋ผ๋ฆฌ์˜ ์ ‘์ด‰์œผ๋กœ ์—ฐ์†์ ์ธ ์ „๋„์„ฑ ๊ฒฝ๋กœ๊ฐ€ ํ™•๋ณด๋œ ์ƒํƒœ์˜ ํ˜ผ์ž…๋Ÿ‰์„ ๋งํ•œ๋‹ค. ์นจํˆฌ ์ž„๊ณ„์ ์˜ ์ƒํƒœ๋Ÿ‰ ์ค‘ ๊ฐ€์žฅ ์ค‘์š”ํ•œ ๊ฒƒ์€ ํ˜ผ์ž…์„ฌ์œ ์˜ ๋ถ€ํ”ผ ๋ถ„์œจ ์ด๋‹ค. Fig. 3์€ ์นจํˆฌ ์ž„๊ณ„์ ์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋ฉฐ, ์„ฌ์œ ์˜ ํ˜ผ์ž…๋Ÿ‰์ด ์นจํˆฌ ์ž„๊ณ„์  ์ดํ•˜์ธ ๊ฒฝ์šฐ์—๋Š” ์„ฌ์œ ์˜ ๋ถ„์‚ฐ์„ฑ์ด ๋†’์„์ˆ˜๋ก ์ „๋„์„ฑ์ด ๋†’์•„์ง„๋‹ค. ํ•˜์ง€๋งŒ ์„ฌ์œ ์˜ ํ˜ผ์ž…๋Ÿ‰์ด ์นจํˆฌ ์ž„๊ณ„์  ์ด์ƒ์ผ ๊ฒฝ์šฐ์—๋Š” ์ด๋ฏธ ์—ฐ์†์ ์ธ ์ „๊ธฐ ์ „๋„๊ฒฝ๋กœ๊ฐ€ ํ˜•์„ฑ๋˜์–ด ๋ถ„์‚ฐ์˜ ์ •๋„์— ๊ด€๊ณ„ ์—†์ด ๋†’์€ ์ „๋„์„ฑ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

Fig. 3 Variation of the resistivity according to the fiber contents
../../Resources/ksm/jksmi.2022.26.3.72/fig3.png

3. ์‹คํ—˜๊ณ„ํš ๋ฐ ๋ฐฉ๋ฒ•

3.1 ์‚ฌ์šฉ์žฌ๋ฃŒ

3.1.1 ์‹œ๋ฉ˜ํŠธ

์‹œ๋ฉ˜ํŠธ๋Š” S์‚ฌ ์ œํ’ˆ์˜ ๋ณดํ†ต ํฌํ‹€๋žœ๋“œ ์‹œ๋ฉ˜ํŠธ(ordinary Portland cement, OPC)๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ๋น„์ค‘์€ 3.13์ด๊ณ  ๋ถ„๋ง๋„๋Š” 3,860 ใŽ /g ์ด๋‹ค.

3.1.2 ์ž”๊ณจ์žฌ

์ž”๊ณจ์žฌ๋Š” ๊ท ์งˆํ•œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด๋ฅผ ๋งŒ๋“ค๊ธฐ ์œ„ํ•ด ๊ฐ•์›๋„ ๊ฐ•๋ฆ‰์‹œ ์ฃผ๋ฌธ์ง„์ ํ–ฅํ˜ธ๋ฆฌ์‚ฐ ํ‘œ์ค€์‚ฌ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ํ‘œ๋ฉด๊ฑด์กฐํฌํ™”์ƒํƒœ ์ž”๊ณจ์žฌ์˜ ๋น„์ค‘๊ณผ ํก์ˆ˜์œจ์€ ๊ฐ๊ฐ 2.65์™€ 0.1%์ด์—ˆ๋‹ค. ์ž”๊ณจ์žฌ์˜ ๋ฌผ๋ฆฌ์  ํŠน์„ฑ์€ Table 1๊ณผ ๊ฐ™๋‹ค.

Table 1 Physical properties of standard sand

Size

(mm)

Unit weight

(kg/ใŽฅ)

Density

(g/ใŽค)

Percentage water absorption

(%)

Fineness modulus

(FM)

2 โ‰ค

1,490

2.65

0.1

2.40

3.1.3 ํ˜ผํ™”์ œ

ํ˜ผํ™”์ œ๋Š” ๊ตญ๋‚ด D์‚ฌ ์ œํ’ˆ์˜ ํด๋ฆฌ์นด๋ฅด๋ณต์‹ค์‚ฐ๊ณ„๋กœ์จ, ์•ก์ƒ์ด๊ณ  ๋น„์ค‘์ด 1.04, pH 5.0ยฑ1.5์ธ ์—ฐํ™ฉ์ƒ‰์˜ ๊ณ ์„ฑ๋Šฅ ๊ฐ์ˆ˜์ œ(super plasticizer, SP)๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ํ˜ผํ™”์ œ์˜ ๋ฌผ๋ฆฌ์  ํŠน์„ฑ์€ Table 2์™€ ๊ฐ™๋‹ค.

Table 2 Physical properties of superplasticizer

Specific (g/ใŽค)

Type

Color

pH

Component

Brand

1.04

Liquid

Light original or light yellow

5.0 ยฑ 1.5

Polycarbo-xylate

Flow

mix 3000E

3.1.4 ํƒ„์†Œ์„ฌ์œ ์™€ ๊ฐ•์„ฌ์œ 

๋ณธ ์—ฐ๊ตฌ์—์„œ ์‚ฌ์šฉํ•œ ํƒ„์†Œ ๋‹จ์„ฌ์œ ๋Š” ์ผ๋ณธ T์‚ฌ์˜ ์ œํ’ˆ์œผ๋กœ ๊ธธ์ด 6 ใŽœ์— ์ง๊ฒฝ์ด 7 ใŽ›์ด๊ณ , ์ธ์žฅ๊ฐ•๋„์™€ ํƒ„์„ฑ๊ณ„์ˆ˜๋Š” ๊ฐ๊ฐ 4,900 MPa์™€ 230 GPa์ด๋‹ค. ํƒ„์†Œํ•จ๋Ÿ‰์ด 92% ์ด์ƒ์ด๊ณ , ๋น„์ €ํ•ญ์ด 1.6ร—10โˆ’3 โ„ฆยทใŽ์ธ ์•„ํฌ๋ฆด๊ณ„๋‚˜์ดํŠธ(polyacrylonnitrile, PAN)๊ธฐ๋ฐ˜ ํƒ„์†Œ์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๊ฐ•์„ฌ์œ ๋Š” ๊ธธ์ด 30 ใŽœ์— ์ง๊ฒฝ์ด 0.5 ใŽœ์ด๊ณ , ์ธ์žฅ๊ฐ•๋„๋Š” 1,100 MPa์ด๋‹ค. ๊ฐ•์„ฌ์œ ๋Š” ๊ตญ๋‚ด K์‚ฌ์˜ ์ œํ’ˆ์œผ๋กœ ์–‘๋‹จ์ด ๊ฐˆ๊ณ ๋ฆฌ ํ˜•ํƒœ์ธ ์–‘๋‹จ ํ›„ํฌํ˜•์„ ์‚ฌ์šฉํ•˜์˜€๊ณ , ์žฌ๋ฃŒํˆฌ์ž…์ด ์šฉ์ดํ•˜๋„๋ก ์—ฌ๋Ÿฌ ๊ฐ€๋‹ฅ์„ ์„œ๋กœ ๋ถ€์ฐฉํ•˜์—ฌ ๋งŒ๋“  ๋ฒˆ๋“ค ํƒ€์ž…(bundle type) ์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ํƒ„์†Œ์„ฌ์œ ์˜ ๊ฒฝ์šฐ ๊ฐ•์„ฌ์œ ์— ๋น„ํ•ด ์ธ์žฅ๊ฐ•๋„๊ฐ€ ์ƒ๋‹นํžˆ ๋†’๊ณ , ์„ฌ์œ ๊ธธ์ด๋Š” ์งง์ง€๋งŒ ๋†’์€ ํ˜•์ƒ๋น„(aspect ratio, ๐‘™f/df)๋ฅผ ๊ฐ–๊ณ  ์žˆ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์— ์‚ฌ์šฉ๋œ ์ „๋„์„ฑ ์žฌ๋ฃŒ์ธ ํƒ„์†Œ์„ฌ์œ ์™€ ๊ฐ•์„ฌ์œ ์˜ ํŠน์„ฑ์€ Table 3๊ณผ ๊ฐ™๋‹ค. ์•„์šธ๋Ÿฌ, Fig. 4๋Š” SEM ์ด๋ฏธ์ง€ ๋ถ„์„์„ ํ†ตํ•ด ๊ด€์ฐฐํ•œ ์ „๋„์„ฑ ํƒ„์†Œ์„ฌ์œ ์™€ ๊ฐ•์„ฌ์œ ์˜ ํ‘œ๋ฉดํ˜•์ƒ์„ ๋‚˜ํƒ€๋‚ธ ์‚ฌ์ง„์ด๋‹ค. Fig. 4(a)์™€ (b)๋Š” ํƒ„์†Œ์„ฌ์œ ์˜ ํ‘œ๋ฉดํ˜•์ƒ์„ ๊ฐ๊ฐ 500๋ฐฐ ๋ฐ 10,000๋ฐฐ์˜ ๋ฐฐ์œจ๋กœ์ดฌ์˜ํ•œ SEM ์‚ฌ์ง„์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋ฉฐ, ํƒ„์†Œ์„ฌ์œ ์˜ ์ง๊ฒฝ์ด ์•ฝ 7.05 ใŽ›๋กœ ํ‘œ๋ฉด์ด ์ƒ๋‹นํžˆ ๋ถ€์ฐฉ์ด ์ƒ๋‹นํžˆ ๋งค๋„๋Ÿฝ๊ฒŒ ๋‚˜ํƒ€๋‚ด, ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค์™€์˜ ๊ณ„๋ฉด์ ‘์ฐฉ์ด ๋งค์šฐ ๋ถˆ๋Ÿ‰ํ•œ ํ‘œ๋ฉด์กฐ์ง์ž„์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. ๋ฐ˜๋ฉด Fig. 4(c)์™€ (d)๋Š” ๊ฐ•์„ฌ์œ ์˜ ํ‘œ๋ฉดํ˜•์ƒ์„ ๊ฐ๊ฐ 30๋ฐฐ ๋ฐ 150๋ฐฐ์˜ ๋ฐฐ์œจ๋กœ ์ดฌ์˜ํ•œ SEM ์‚ฌ์ง„์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋ฉฐ, ๊ฐ•์„ฌ์œ ์˜ ์ง๊ฒฝ์ด ์•ฝ 500.99 ใŽ›๋กœ ํ‘œ๋ฉด์ด ์–ด๋Š ์ •๋„ ๊ฑฐ์น ์–ด ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค์— ๊ณ„๋ฉด์ ‘์ฐฉ์ด ์œ ๋ฆฌํ•œ ํ‘œ๋ฉด์กฐ์ง์„ ํ˜•์„ฑํ•˜๊ณ  ์žˆ๋‹ค๋Š” ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค.

Fig. 4 SEM observations of the conductive fibers
../../Resources/ksm/jksmi.2022.26.3.72/fig4.png
Table 3 Properties of CF and SF

Fibers

Average length, ๐‘™(ใŽœ)

Average diameters, d(ใŽœ)

Aspect ratio (๐‘™f/df)

Density

(kg/ใŽฅ)

Tensile strength (MPa)

Elastic modulus (GPa)

Resistivity

(โ„ฆยทใŽ)

Carbon

6

0.007

857

1,800

4,900

230

1.6ร—10-3

Steel

30

0.5

60

7,850

1,100

> 210

-

3.2 ๋ฐฐํ•ฉ์„ค๊ณ„ ๋ฐ ์‹œํŽธ์ œ์ž‘

์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด๋ฅผ ์ œ์กฐํ•˜๊ธฐ ์œ„ํ•œ ๋ฐฐํ•ฉ์„ค๊ณ„๋Š” Table 4์™€ ๊ฐ™๋‹ค. ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ €ํ•ญ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ๊ฒ€ํ† ํ•˜๊ธฐ ์œ„ํ•ด ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์˜ ๋ณ€ํ™”๋Š” ํƒ„์†Œ์„ฌ์œ ์˜ ๊ฒฝ์šฐ ๋ถ€ํ”ผ๋น„๋กœ 0.1, 0.2, 0.3, 0.4, 0.5 ๋ฐ 0.6%๋กœ ํ•˜์˜€์œผ๋ฉฐ, ๊ฐ•์„ฌ์œ ๋Š” 0.25, 0.5, 0.75, 1.0 ๋ฐ 1.25%๋กœ ์ด 11๊ฐ€์ง€ ์ˆ˜์ค€์œผ๋กœ ์„ค์ •ํ•˜์˜€๋‹ค. ์žฌ๋ฃŒ ๋ฐฐํ•ฉ์€ KS L 5109์˜ ์‹œํ—˜๊ทœ์ •์— ๋”ฐ๋ผ ์•ฝ 4.73 L ์šฉ๋Ÿ‰์˜ ์†Œํ˜• ํ˜ธ๋ฐ”ํŠธ(horbat)ํ˜• ๋ฏน์„œ๊ธฐ๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ์‹œ๋ฉ˜ํŠธ:ํ‘œ์ค€์‚ฌ:๋ฐฐํ•ฉ์ˆ˜=1:2:0.45์˜ ๋น„์œจ๋กœ ํ˜ผํ•ฉํ•˜์˜€๋‹ค. ์ด๋•Œ ๊ตต์€ ๊ณจ์žฌ๋Š” ์‚ฌ์šฉํ•˜์ง€ ์•Š์•˜๋‹ค. ํƒ„์†Œ์„ฌ์œ ์˜ ๋ถ„์‚ฐ์„ฑ ๋ฐ ์›Œ์ปค๋นŒ๋ฆฌํ‹ฐ๋ฅผ ์œ ์ง€ํ•˜๊ธฐ ์œ„ํ•ด ํ˜ผํ™”์ œ์˜ ์ฒจ๊ฐ€๋Ÿ‰์€ ์‹œ๋ฉ˜ํŠธ ์งˆ๋Ÿ‰์˜ 0.5%๋กœ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์™€ ์ „๋„์„ฑ SFRCM์˜ ๊ฒฝ์šฐ ๋ณ„๋„์˜ ํ˜ผํ™”์ œ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š์•˜๋‹ค. Fig. 5๋Š” ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ์‹œํŽธ์˜ ์ œ์ž‘๊ณผ์ •์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Fig. 5์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ๋จผ์ €, ํ˜ผํ•ฉ๊ธฐ์— ์„ฌ์œ ์™€ ํ‘œ์ค€์‚ฌ๋ฅผ ํˆฌ์ž…ํ•˜์—ฌ ์ €์†์œผ๋กœ 60์ดˆ ๋™์•ˆ ํ˜ผํ•ฉํ•œ ํ›„ ์™„์ „ํ•œ ์„ฌ์œ ์˜ ๋ถ„์‚ฐ์„ ์œ„ํ•ด ๊ฑด๋น„๋น”์œผ๋กœ 90์ดˆ ๋™์•ˆ ์ถ”๊ฐ€ ํ˜ผํ•ฉํ•˜์˜€๋‹ค. ๋‘ ๋ฒˆ์งธ๋กœ ์‹œ๋ฉ˜ํŠธ ํˆฌ์ž… ๋ฐ ๋ฐฐํ•ฉ์ˆ˜์™€ SP์ œ๋ฅผ ํ˜ผํ•ฉ ์šฉ๊ธฐ ์†์— ์ฒœ์ฒœํžˆ ์ฒจ๊ฐ€ํ•˜๊ณ  ์ค‘์†์œผ๋กœ 90์ดˆ ๋™์•ˆ ํ˜ผํ•ฉํ•˜์˜€๋‹ค. ๋‹ค์‹œ ํ˜ผํ•ฉ๊ธฐ๋ฅผ ๊ณ ์†์œผ๋กœ 60์ดˆ ๋™์•ˆ ํ˜ผํ•ฉํ•˜์—ฌ ์ตœ์ข… ๋ชจ๋ฅดํƒ€๋ฅด ํ˜ผํ•ฉ๋ฌผ์„ ์–ป์—ˆ๋‹ค. ์ด ํ˜ผํ•ฉ ์‹œ๊ฐ„์€ 5๋ถ„ ์ •๋„ ์†Œ์š”๋˜์—ˆ๋‹ค. ๋งˆ์ง€๋ง‰์œผ๋กœ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ํ˜ผํ•ฉ๋ฌผ์„ ๊ธˆํ˜• ๋ชฐ๋“œ์— ๋ถ€์–ด ๋„ฃ๊ณ , ๊ท ์ผํ•œ ๋ชจ๋ฅดํƒ€๋ฅด๋ฅผ ๋งŒ๋“ค๊ธฐ ์œ„ํ•ด ํ‘œ์ธต์„ ํ‰ํ‰ํ•˜๊ฒŒ ๊ณ ๋ฅด๊ณ  ๋‚œ ํ›„ ๋ชฐ๋“œ ์˜†๋ฉด์„ ๊ณ ๋ฌด๋ง์น˜๋ฅผ ์ด์šฉํ•˜์—ฌ ์•ฝ 25ํšŒ ์ •๋„ ํƒ€๊ฒฉํ•˜์—ฌ ํ‘œ๋ฉด์˜ ์š”์ฒ ์ด ์—†์ด ํ‰ํ‰ํ•˜๊ฒŒ ๋  ๋•Œ๊นŒ์ง€ ์ถฉ๋ถ„ํžˆ ๋‹ค์กŒ๋‹ค. ์•„์šธ๋Ÿฌ, ์‹œํŽธ ๋‚ด๋ถ€์˜ ๊ณต๊ทน์„ ์ตœ์†Œํ™”ํ•˜๊ธฐ ์œ„ํ•ด ์‹คํ—˜์‹ค ์ง„๋™ ํ…Œ์ด๋ธ”์„ ์‚ฌ์šฉํ•˜์—ฌ ์•ฝ 3๋ถ„ ๋™์•ˆ ์•ฝํ•˜๊ฒŒ ์‹œํŽธ์„ ์ง„๋™์‹œ์ผœ ๊ตฌ๋ฆฌ ๋งค์‰ฌ์™€ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ์‚ฌ์ด์˜ ๊ท ์ผํ•œ ์ ‘์ด‰์„ ์œ ์ง€ํ† ๋ก ์ง„๋™ ๋‹ค์ง์„ ์‹ค์‹œํ•˜์˜€๋‹ค. ๋ชจ๋“  ์‹œํŽธ์€ ์„ฑํ˜• ํ›„ 24์‹œ๊ฐ„ ๊ฒฝ๊ณผํ•˜์—ฌ ๋ชฐ๋“œ๋ฅผ ํƒˆํ˜•ํ•˜์˜€๋‹ค.

Fig. 5 Fabrication process of cement mortars
../../Resources/ksm/jksmi.2022.26.3.72/fig5.png
Table 4 Mix proportions of cement mortars

Mix ID

Fiber volume fractions, Vf (%)

W/C

C/S

Unit content (kg/ใŽฅ)

SP

(Cร—%)

CF

SF

Water

Cement

Sand

CF10

0.10

-

0.45

1:2

297

660

1,320

0.5

CF20

0.20

-

CF30

0.30

-

CF40

0.40

-

CF50

0.50

-

CF60

0.60

-

SF25

-

0.25

0.45

1:2

297

660

1,320

-

SF50

-

0.50

SF75

-

0.75

SF100

-

1.00

SF125

-

1.25

Plain mortar (PM)

-

-

0.45

1:2

297

660

1,320

-

* W/C = water to cement ratio, C/S = cement to fine aggregate ratio, and SP = superplasticizer.

Fig. 6์€ ์ „๊ธฐ์ €ํ•ญ์„ ์ธก์ •ํ•˜๊ธฐ ์œ„ํ•ด ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ์‹œํŽธ์— ๋งค์ž…๋œ ๊ตฌ๋ฆฌ๋งค์‰ฌ ์ „๊ทน์˜ ๊ตฌ์„ฑ์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Fig. 6์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด๋Š” 40 ร— 40 ร— 160 mm3 ํฌ๊ธฐ์˜ ๊ฐ์ฃผํ˜• ์‹œํŽธ์— ๋“ฑ ๊ฐ„๊ฒฉ์œผ๋กœ ์ผ๋ ฌ๋กœ ๋‚˜์—ดํ•œ 4๊ฐœ์˜ ๊ตฌ๋ฆฌ ๋งค์‰ฌ๋ฅผ ์ผ์ง ์„ ์ƒ์œผ๋กœ 40 mm ๊ฐ„๊ฒฉ์œผ๋กœ ์ „๊ทน์„ ๋งค์ž…ํ•˜์˜€๋‹ค. ๊ทธ๋ฆฌ๊ณ  ๊ตฌ๋ฆฌ์™€ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด๊ฐ€ ์ ‘ํ•˜๋Š” ๋ถ€๋ถ„์€ ์„œ๋กœ ๋‹ค๋ฅธ ๋ฌผ์งˆ ์‚ฌ์ด์˜ ๋ถˆ์—ฐ์†์„ฑ์„ ์ตœ์†Œํ™”ํ•˜๊ธฐ ์œ„ํ•ด ๊ตฌ๋ฆฌ๋งค์‰ฌ ์ „๊ทน์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด๋ฅผ ํƒ€์„คํ•œ ๋ชจ๋“  ์‹œํŽธ์€ ์„ฑํ˜• ํ›„ 24์‹œ๊ฐ„ ๊ฒฝ๊ณผํ•˜์—ฌ ๋ชฐ๋“œ๋ฅผ ํƒˆํ˜•ํ•˜์˜€์œผ๋ฉฐ, ์ „๊ธฐ์ €ํ•ญ ์ธก์ • ์‹œ ์–‘์ƒํ™˜๊ฒฝ์— ๋”ฐ๋ฅธ ์ „๋„์„ฑ ์˜ํ–ฅ์„ ์ตœ์†Œํ™”ํ•˜๊ธฐ ์œ„ํ•ด ์‹œํ—˜ ์ง์ „๊นŒ์ง€ ํ•ญ์˜จํ•ญ์Šต ์กฐ๊ฑด(์•ฝ ์˜จ๋„ 23โ„ƒ ๋ฐ ์ƒ๋Œ€์Šต๋„ 60ยฑ5%)์ฑ”๋ฒ„์— ๋ณด๊ด€ํ•˜์˜€๋‹ค. ์‹ ๋ขฐํ•  ์ˆ˜ ์žˆ๋Š” ์ „๊ธฐ์ €ํ•ญ ๋ฐ์ดํ„ฐ๋ฅผ ํš๋“ํ•˜๊ธฐ ์œ„ํ•ด ๋ชจ๋“  ๋ฐฐํ•ฉ์—์„œ ๋ณ€์ˆ˜๋ณ„๋กœ ๊ฐ 3๊ฐœ์”ฉ ์‹œํŽธ์„ ์ œ์ž‘ํ•˜์˜€๋‹ค.

Fig. 6 Configuration of copper mesh electrodes
../../Resources/ksm/jksmi.2022.26.3.72/fig6.png

3.3 ์‹คํ—˜๋ฐฉ๋ฒ•

3.3.1 ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ €ํ•ญ ์ธก์ •

Fig. 7์€ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ์‹œํŽธ์˜ ์ „๊ธฐ์ €ํ•ญ ์ธก์ • ๋ชจ์Šต์„ ์‚ฌ์ง„์œผ๋กœ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ๋ชจ๋“  ์‹œํŽธ์˜ ์ „๊ธฐ์ €ํ•ญ์€ ๋‹ค์–‘ํ•œ ์–‘์ƒ์žฌ๋ น(3, 7, 14, 28. 56 ๋ฐ 90์ผ)์—์„œ ์ธก์ •๋˜์—ˆ๋‹ค. ์ „๊ธฐ์ €ํ•ญ์„ ์ธก์ •ํ•˜๊ธฐ ์œ„ํ•ด ๋””์ง€ํ„ธ ๋ฉ€ํ‹ฐ๋ฏธํ„ฐ(precision current source, Keithley 6220)๋Š” 2๊ฐœ์˜ ๋ฐ”๊นฅ์ชฝ ์ „๊ทน์— DC(I)๋ฅผ ๊ณต๊ธ‰ํ•˜๊ณ , Keithley 2182A(nanovoltmeter)๋Š” 2๊ฐœ์˜ ์•ˆ์ชฝ ์ „๊ทน์€ ์ „์••(V) ์ธก์ •์— ์‚ฌ์šฉ๋˜์—ˆ๋‹ค. ์ธ๊ฐ€ ์ „๋ฅ˜๋Š” ยฑ100 fA์—์„œ ยฑ100 mA ๋ฒ”์œ„๊นŒ์ง€ ๊ฐ€๋Šฅํ•˜๊ณ , ์ „๊ธฐ์ €ํ•ญ ๊ฐ’์˜ ์ธก์ • ๋ฒ”์œ„๋Š” 10 nฮฉ์—์„œ 200 Mฮฉ ๋ฒ”์œ„๊นŒ์ง€ ๊ฐ€๋Šฅํ•˜๋‹ค. ์ผ๋ฐ˜์ ์œผ๋กœ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ €ํ•ญ ์ธก์ •๋ฐฉ๋ฒ•์€ 2-probe(two probe method)์™€ 4-probe(four probe method) ๋ฐฉ๋ฒ•์ด ์‚ฌ์šฉ๋˜๊ณ  ์žˆ๋‹ค. ๋น„๋ก 2-probe ๋ฐฉ๋ฒ•์˜ ํšŒ๋กœ๊ฐ€ ๋” ๊ฐ„๋‹จ ํ•˜์ง€๋งŒ ์‹œํŽธ๊ณผ ์ „๊ทน ์‚ฌ์ด์˜ ์ ‘์ด‰์ €ํ•ญ์„ ํฌํ•จํ•˜์ง€ ์•Š๊ธฐ ๋•Œ๋ฌธ์— 4-probe ๋ฐฉ๋ฒ•์ด ์„ ํ˜ธ๋˜๊ณ  ์žˆ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ์˜ ์ „๊ธฐ์ €ํ•ญ์€ 4-probe ๋ฐฉ๋ฒ•์„ ์‚ฌ์šฉํ•˜์—ฌ ์ธก์ •ํ•˜์˜€๋‹ค. ์ธก์ •๋œ ์ „๊ธฐ์ €ํ•ญ์„ ์žฌ๋ฃŒ์˜ ๊ณ ์œ  ํŠน์„ฑ์œผ๋กœ ๋‚˜ํƒ€๋‚ด๊ธฐ ์œ„ํ•ด์„œ๋Š” ๊ณ ์œ  ๋น„์ €ํ•ญ(resistivity) ๋˜๋Š” ์ „๊ธฐ์ „๋„๋„(conductivity)๋กœ ๋ณ€ํ™˜์ด ํ•„์š”ํ•˜๋‹ค. ๋”ฐ๋ผ์„œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋น„์ €ํ•ญ(electrical resistivity, ฯ)์€ ์ธก์ •๋œ ์ „๊ธฐ์ €ํ•ญ ๋ฐ ์ฃผ์–ด์ง„ ๊ธธ์ด์™€ ๋‹จ๋ฉด์ ์˜ ์‹œํŽธ ํ˜•์ƒ์— ๋”ฐ๋ผ ์‹ (2)์„ ์ด์šฉํ•˜์—ฌ ๊ตฌํ•˜์˜€์œผ๋ฉฐ, ์ด๋Š” ์ „๊ธฐ์ €ํ•ญ(R) ๋ฐ ๋‹จ๋ฉด์ (A)์—๋Š” ๋น„๋ก€ํ•˜๊ณ , ๊ธธ์ด(L)์—๋Š” ๋ฐ˜๋น„๋ก€ํ•œ๋‹ค.

(2)
ฯ=RAL=1ฯƒ

์—ฌ๊ธฐ์„œ, ฯ๋Š” ๊ณ ์œ  ๋น„์ €ํ•ญ(โ„ฆยทใŽ)์ด๋ฉฐ, A๋Š” ์ „๊ทน์ด ์ ‘์ด‰ํ•œ ๋ถ€๋ถ„์˜ ๋ฉด์ (16ใŽ )์ด๋ฉฐ, L์€ ์ „๊ทน๊ณผ ์ „๊ทน ์‚ฌ์ด์˜ ๊ฐ„๊ฒฉ(4ใŽ)์ด๋ฉฐ, R์€ ์ธก์ •๋œ ์ „๊ธฐ์ €ํ•ญ ๊ฐ’(โ„ฆ)์ด๋‹ค. ์ธก์ •๋œ ์ „๊ธฐ์ €ํ•ญ์€ ๋ฌผ์ฒด์˜ ๊ณ ์œ ํ•œ ๊ฐ’์ด๋ฉฐ, ์ „๊ธฐ์ „๋„๋„(electrical conductivity)์™€ ์—ญ์ˆ˜์˜ ๊ด€๊ณ„๋ฅผ ๊ฐ–๋Š”๋‹ค.

Fig. 7 The resistivity measurement of cement mortar specimen
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3.3.2 SEM/EDS ๊ด€์ฐฐ

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ „๋„์„ฑ FRCM ํŒŒ๋‹จ๋ฉด์˜ ํ‘œ๋ฉดํ˜•์ƒ์„ ๊ด€์ฐฐํ•˜๊ธฐ ์œ„ํ•ด SEM ์ด๋ฏธ์ง€ ์ดฌ์˜์„ ๊ณ„ํšํ•˜์˜€์œผ๋ฉฐ, ๋™์‹œ์— ์‚ฌ์šฉํ•˜๋Š” EDS์— ์˜ํ•ด ๊ตฌ์„ฑ์„ฑ๋ถ„์„ ๋ถ„์„ํ•˜์˜€๋‹ค. ๋ถ„์„ ์žฅ๋น„๋Š” TESCAN ์‚ฌ์˜ MIRA3-LMH ๊ณ ๋ถ„ํ•ด๋Šฅ FE-SEM ๋ชจ๋ธ๋ช…์„ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์˜ ์„ฑ๋ถ„๋ถ„์„์„ ์œ„ํ•ด Bruker์‚ฌ์˜ EDS ๋””ํ…ํ„ฐ๋กœ ์ถ”๊ฐ€ ์‹ค์‹œํ•˜์˜€๋‹ค. ๊ฐ•๋„ ์‹œํ—˜ ํ›„ ๊ฒฝํ™”๋œ ์‹œํŽธ์„ ๋ถ„์‡„ํ•˜์—ฌ ํš๋“ํ•œ ์„ฌ์œ ๋ฅผ ๊ฑด์กฐํ•˜์—ฌ ์ง„๊ณต์ƒํƒœ์—์„œ ๋ฐฑ๊ธˆ์œผ๋กœ ์ฝ”ํŒ…ํ•œ ํ›„ SEM/EDS์— ์˜ํ•ด ์ด๋ฏธ์ง€์™€ ์„ฑ๋ถ„๋ถ„์„์„ ์‹ค์‹œํ•˜์˜€๋‹ค.

3.3.3 ์••์ถ•๊ฐ•๋„ ์‹œํ—˜

์••์ถ•๊ฐ•๋„ ์‹œํ—˜์€ KSL ISO 679(KATS, 2016)์˜ ์‹œํ—˜๋ฐฉ๋ฒ•์— ๋”ฐ๋ผ ๊ฐ ๋ณ€์ˆ˜๋ณ„๋กœ 3๊ฐœ์”ฉ ๋ชฐ๋“œ๋ฅผ ์ œ์ž‘ํ•˜์—ฌ ์–‘์ƒ์žฌ๋ น 28์ผ์—์„œ ์••์ถ•๊ฐ•๋„๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ์–‘์ƒ์ด ์™„๋ฃŒ๋œ 40ร—40ร—160 mm ํฌ๊ธฐ์˜ ๊ฐ์ฃผํ˜• ์‹œํŽธ์€ 100-kN ์šฉ๋Ÿ‰์˜ ๋งŒ๋Šฅ์žฌ๋ฃŒ์‹œํ—˜๊ธฐ(MTDI Co., Ltd, Korea, UT-100F)๋ฅผ ์ด์šฉํ•˜์—ฌ ํ•˜์ค‘์ œ์–ด ๋ฐฉ์‹์œผ๋กœ ์••์ถ•๊ฐ•๋„๋ฅผ ์ธก์ •ํ•˜์˜€์œผ๋ฉฐ, ์žฌํ•˜์†๋„๋Š” 2400 N/s์˜ ์กฐ๊ฑด์—์„œ ์ผ์ •ํ•œ ์†๋„๋กœ ๊ฐ€๋ ฅํ•˜์˜€๋‹ค.

4. ์‹คํ—˜๊ฒฐ๊ณผ ๋ฐ ๊ณ ์ฐฐ

4.1 ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋น„์ €ํ•ญ ํŠน์„ฑ

4.1.1 ์–‘์ƒ์žฌ๋ น์— ๋”ฐ๋ฅธ ๋น„์ €ํ•ญ ํŠน์„ฑ

Fig. 8์€ ๊ฐ ์‹œํŽธ์˜ ์–‘์ƒ์žฌ๋ น์— ๋”ฐ๋ฅธ ์ „๋„์„ฑ FRCM์™€ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ํ‰๊ท  ๋น„์ €ํ•ญ ๋ณ€ํ™”๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Fig. 8์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ๋ชจ๋“  ์‹œํŽธ์—์„œ ์–‘์ƒ์žฌ๋ น์ด ๊ฒฝ๊ณผ๋จ์— ๋”ฐ๋ผ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์—์„œ ์ˆ˜ํ™”์ž‘์šฉ์ด ์„œ์„œํžˆ ์ง„ํ–‰๋˜๊ณ  ๋ฏธ์„ธ๊ตฌ์กฐ ํ˜•์„ฑ์ด ์ง€์†์ ์œผ๋กœ ๋ฐœ์ „๋˜๋ฉด์„œ ๋น„์ €ํ•ญ์ด ์ ์ฐจ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ์ด๋Ÿฌํ•œ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋Š” ์„ ํ–‰ ์—ฐ๊ตฌ์—์„œ๋„ ๋ณด๊ณ ๋˜์—ˆ๋‹ค(EL-Enein et al., 1995; Wang et al., 2017). ์ด๋Š” ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์— ์กด์žฌํ•˜๋Š” ์ž์œ ์ˆ˜๊ฐ€ ์ฆ๋ฐœํ•˜๊ณ  ์ˆ˜ํ™”์ž‘์šฉ์ด ์ง„ํ–‰๋จ์— ๋”ฐ๋ผ ์ž์œ ์ˆ˜๊ฐ€ ๊ฐ์†Œํ•˜๊ณ  ๋ฏธ์„ธ๊ตฌ์กฐ์˜ ์น˜๋ฐ€ํ™”๋กœ ๋ถˆ์—ฐ์†์ด ๋˜๋ฉด์„œ ์ „๋ฅ˜์˜ ํ๋ฆ„์„ ๋ฐฉํ•ดํ•˜๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค. ์ผ๋ฐ˜์ ์ธ ์–‘์ƒ์œผ๋กœ ์ž์œ ์ˆ˜์˜ ์–‘์ด ๋‚ฎ์„์ˆ˜๋ก ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ํ†ต์ „์„ฑ์ด ์ž‘์•„์ ธ์„œ ๋น„์ €ํ•ญ์ด ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ์•Œ๋ ค์ ธ ์žˆ๋‹ค. ์‹ค์ œ ์ดˆ๊ธฐ 3์ผ ์–‘์ƒ์žฌ๋ น์—์„œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๊ฒฝ์šฐ ๊ณต๊ทน์— ์กด์žฌํ•˜๋Š” ์ž์œ ์ˆ˜์— ์˜ํ•ด ์ „๋„์„ฑ์ด ํ–ฅ์ƒ๋œ๋‹ค๋Š” ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค.

Fig. 8 Resistivity change of the cement mortar with carbon fiber or steel fiber over curing age
../../Resources/ksm/jksmi.2022.26.3.72/fig8.png

4.1.2 ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ ๋น„์ €ํ•ญ ํŠน์„ฑ

Fig. 9๋Š” ๊ฐ ์‹œํŽธ์˜ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ ์ „๋„์„ฑ FRCM์™€ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ํ‰๊ท  ๋น„์ €ํ•ญ ๋ณ€ํ™”๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Fig. 9์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ๋‹ค์–‘ํ•œ ์žฌ๋ น์—์„œ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์—์„œ ์„ฌ์œ ์˜ ๋ธŒ๋ฆฌ์ง•(bridging)์„ ํ–ฅ์ƒ์‹œ์ผœ ๋น„์ €ํ•ญ์ด ์ ์ฐจ ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ์ด๋Ÿฌํ•œ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋Š” ์„ ํ–‰ ์—ฐ๊ตฌ์—์„œ๋„ ๋ณด๊ณ ๋˜์—ˆ๋‹ค(Wang et al., 2017). ์ด๋Š” ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์— ํ˜ผ์ž…๋œ ์ „๋„์„ฑ ์„ฌ์œ ๊ฐ€ ๋น„์ €ํ•ญ์ด ํ›จ์”ฌ ๋” ๊ฐ์†Œํ•˜์—ฌ ์ „๋ฅ˜๊ฐ€ ์‰ฝ๊ฒŒ ํ๋ฅผ ์ˆ˜ ์žˆ๋Š” ํ†ต๋กœ๊ฐ€ ํ˜•์„ฑ๋˜์–ด ์ „๋ฅ˜์˜ ํ๋ฆ„์ด ํ™œ๋ฐœํ•ด์ง€๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค. ํŠนํžˆ ํƒ„์†Œ์„ฌ์œ ๋Š” ๊ฐ•์„ฌ์œ ์— ๋น„ํ•ด ๋งค์šฐ ์ž‘์€ ์ง€๋ฆ„๊ณผ ๋†’์€ ํ˜•์ƒ๋น„(aspect ratio ใ€‰857)๋ฅผ ๊ฐ–๊ณ  ์žˆ์–ด, ํ˜ผ์ž… ๊ฐœ์ฒด์ˆ˜๊ฐ€ ๋งŽ๊ณ  ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์„ฌ์œ ๋“ค ๋ผ๋ฆฌ์˜ ์—ฐ๊ฒฐ์„ฑ์ด ์šฐ์ˆ˜ํ•˜์—ฌ ์ „๋„์„ฑ CFRCM์˜ ๋น„์ €ํ•ญ์ด ๊ฐ์†Œ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์•„์šธ๋Ÿฌ, ๋” ๋งŽ์€ ์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•จ์œผ๋กœ์จ ๋ฐ€์ ‘ํ•œ ์ ‘์ด‰์œผ๋กœ ์ „๋„์„ฑ ๊ฒฝ๋กœ๊ฐ€ ํ˜•์„ฑ๋˜์—ฌ ๋น„์ €ํ•ญ์ด ๋”์šฑ ๊ฐ์†Œํ•  ์ˆ˜ ์žˆ๊ฒŒ ๋œ๋‹ค๋Š” ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค.

Fig. 9 Resistivity change of the cement mortar containing carbon fiber or steel fiber with different fiber volume fraction
../../Resources/ksm/jksmi.2022.26.3.72/fig9.png

4.1.3 ์ „๋„์„ฑ FRCM์˜ ์ ์ • ์„ฌ์œ ํ•จ๋Ÿ‰ ์‚ฐ์ •๊ณผ ์นจํˆฌ์ž„๊ณ„์ 

์‹œ๋ฉ˜ํŠธ ๊ธฐ๋ฐ˜ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ „๋„๋Š” ์ „์ž์ „๋„(electronic conduction) ๋ฐ ์ด์˜จ์ „๋„(ionic conduction)์˜ ๋‘ ๊ฐ€์ง€ ๋ฐฉ์‹์— ์˜ํ•ด ์ผ์–ด๋‚œ๋‹ค. ์ „์ž์ „๋„๋Š” ์„ฌ์œ ๋ฅผ ํ†ตํ•œ ์ž์œ ์ „์ž ์ด๋™์— ์˜ํ•ด ์ „๋ฅ˜๊ฐ€ ํ๋ฅด๋Š” ๊ฒƒ์ด๋ฉฐ, ์ด์˜จ์ „๋„๋Š” ๋ฏธ์„ธ๊ตฌ์กฐ ๋‚ด ์ž์œ ์ˆ˜๋ฅผ ํ†ตํ•œ ์ด์˜จ์˜ ์ด๋™์— ์˜ํ•œ ์ „๊ธฐ์ „๋„์ด๋‹ค(Whittington, H. et al. 1981). Fig. 10์€ ์„ธ๋ฏธ-๋กœ๊ทธ ๊ทธ๋ž˜ํ”„ ๊ธฐ๋ฐ˜์œผ๋กœ ์ „๋„์„ฑ FRCM์˜ ๋‹ค์–‘ํ•œ ์–‘์ƒ์žฌ๋ น์—์„œ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ ๋น„์ €ํ•ญ ๋ณ€ํ™”๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Fig. 10(a)์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ์ „๋„์„ฑ SFRCM์˜ ๊ฒฝ์šฐ ๊ฐ•์„ฌ์œ ์˜ ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ๋น„์ €ํ•ญ์€ ๋ชจ๋‘ ๊ฐ์†Œํ•˜์˜€์œผ๋‚˜, ์ „๋ฐ˜์ ์œผ๋กœ 1.25%๊นŒ์ง€ ๊ฐ•์„ฌ์œ ๋ฅผ ์ถ”๊ฐ€ํ•˜๋”๋ผ๋„ ๋น„์ €ํ•ญ์„ ํฌ๊ฒŒ ๋‚ฎ์ถœ ์ˆ˜ ์—†๋‹ค. ์„ฌ์œ ๋“ค ์‚ฌ์ด์˜ ํšจ๊ณผ์ ์ธ ์ ‘์ด‰์ด ์ด๋ฃจ์–ด์ง€์ง€ ์•Š๊ธฐ ๋•Œ๋ฌธ์— ์ „๋„์„ฑ ๊ฒฝ๋กœ ํ˜•์„ฑ์ด ๋ถ€์กฑํ•จ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. ๋ฐ˜๋ฉด Fig. 10(b)์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ์ „๋„์„ฑ CFRCM์˜ ๊ฒฝ์šฐ ๋‚ฎ์€ ํ•จ๋Ÿ‰์—์„œ๋„ ์ „๋„์„ฑ ๊ฒฝ๋กœ ํ˜•์„ฑ์˜ ์‹œ์ž‘์„ ๋‚˜ํƒ€๋‚ด, ์ „๋„์„ฑ์„ ๋†’์ผ ์ˆ˜ ์žˆ๋‹ค. ํƒ„์†Œ์„ฌ์œ ๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์˜ ์นจํˆฌ ์ „์ด์˜์—ญ์€ 0.1โˆผ0.4% ์‚ฌ์ด์— ์กด์žฌํ•˜๋ฉฐ, ์นจํˆฌ ์ž„๊ณ„์ ์ธ 0.4%๋ฅผ ์ดˆ๊ณผํ•˜๋Š” ์ „๋„์„ฑ CFRCM์˜ ๊ฒฝ์šฐ ํƒ„์†Œ์„ฌ์œ ์˜ ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์„ฌ์œ ๋“ค๋ผ๋ฆฌ์˜ ์—ฐ๊ฒฐ์„ฑ์ด ์™„์ „ํ•ด์ ธ์„œ ์„ฌ์œ  ์‚ฌ์ด์˜ ์šฐ์ˆ˜ํ•œ ์—ฐ๊ฒฐ์„ฑ๊ณผ ์„ฌ์œ ์˜ ํ˜ผ์ž… ๊ฐœ์ฒด์ˆ˜ ์ฆ๊ฐ€๋กœ ์ธํ•ด ๋น„์ €ํ•ญ์ด ํ˜„์ €ํžˆ ๊ฐ์†Œ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ์นจํˆฌ ์ž„๊ณ„์ ์„ ์ดˆ๊ณผํ•˜๋Š” 0.5โˆผ0.6%์—์„œ๋Š” ์ „๋„์„ฑ ๊ฒฝ๋กœ๊ฐ€ ์ด๋ฏธ ํ˜•์„ฑ๋˜์–ด ์žˆ๊ธฐ ๋•Œ๋ฌธ์— ๋ˆˆ์— ๋„๋Š” ์ „๋„์„ฑ ๋ณ€ํ™”๋ฅผ ์ผ์œผํ‚ค์ง€ ๋ชปํ–ˆ๋‹ค. ์นจํˆฌ ์ž„๊ณ„์  ์ดํ›„์—์„œ ๋น„์ €ํ•ญ์ด ๊ฐ์†Œํ•˜๋Š” ์ด์œ ๋Š” ๋‹ค๋Ÿ‰์˜ ์„ฌ์œ  ํ˜ผ์ž…์œผ๋กœ ์ธํ•œ ๊ณต๊ทน์˜ ๋ฐœ์ƒ๊ณผ ์„ฌ์œ ์˜ ๋ญ‰์นจํ˜„์ƒ์œผ๋กœ ์ธํ•œ ์ž์œ ์ˆ˜์˜ ์–‘์„ ์ฆ๊ฐ€์‹œํ‚จ ๊ฒฐ๊ณผ๋ผ ํŒ๋‹จ๋œ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์— ์‚ฌ์šฉ๋œ ์ „๋„์„ฑ CFRCM์— ๋Œ€ํ•œ ๊ฐ์ง€๋œ ์นจํˆฌ ์ž„๊ณ„์ ์€ ๋น„์ €ํ•ญ์„ ๋‚ฎ์ถ”๋ฐ ์žˆ์–ด 0.4%๊ฐ€ ์ตœ์ ์˜ ํƒ„์†Œ์„ฌ์œ  ํ˜ผ์ž…๋Ÿ‰์„ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์นจํˆฌ ์ด๋ก ์€ FRCM์˜ ๋ฐฐํ•ฉ์„ค๊ณ„ ์‹œ ์„ฌ์œ ํ˜ผ์ž… ๋ถ€ํ”ผ๋น„์— ์˜ํ•œ ์นจํˆฌ ์ž„๊ณ„์ ์„ ๊ณ ๋ คํ•œ ์ตœ์ ์˜ ์„ฌ์œ ํ˜ผ์ž…๋Ÿ‰์„ ๊ฒฐ์ •ํ•˜๋Š”๋ฐ ๋งค์šฐ ํšจ๊ณผ์ ์ด๋ผ๊ณ  ํŒ๋‹จ๋œ๋‹ค.

Fig. 10 Variation of resistivity by fiber content in SFRCM and CFRCM
../../Resources/ksm/jksmi.2022.26.3.72/fig10.png

4.1.4 ์ „๋„์„ฑ FRCM์˜ ์„ฌ์œ ๋ถ„ํฌ ๊ด€์ฐฐ

์นจํˆฌ ์ด๋ก ์— ๋”ฐ๋ฅด๋ฉด ์„ฌ์œ ๊ฐ€ ์ผ์ • ๋ถ€ํ”ผ๋ถ„์œจ๋กœ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์— ํ˜ผ์ž…๋˜๋ฉด ์ „๊ธฐ์  ํด๋Ÿฌ์Šคํ„ฐ(cluster)๊ฐ€ ํ˜•์„ฑ๋˜๊ณ , ๋น„์ €ํ•ญ์ด ๊ธ‰๊ฒฉํžˆ ๊ฐ์†Œํ•œ๋‹ค. ์นจํˆฌ ์ž„๊ณ„์  ์ด์ƒ์˜ ์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•˜๋ฉด ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์—์„œ ์„ฌ์œ ์˜ ํ„ฐ๋„๋ง ํšจ๊ณผ(tunnelling effect)๋ฅผ ๋ฐœ์ƒ์‹œ์ผœ ์ „๊ธฐ๊ฐ€ ํ†ต๊ณผํ•˜๋„๋ก ํ†ต๋กœ๋ฅผ ํ˜•์„ฑํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด๋ ‡๊ฒŒ ์—ฐ๊ฒฐ๋œ ์„ฌ์œ ๋“ค์„ ํด๋Ÿฌ์Šคํ„ฐ๋ผ ํ•˜๋ฉฐ, ํ•œ ํด๋Ÿฌ์Šคํ„ฐ ๋‚ด์—๋Š” ํ•œ ๊ฐœ ์ด์ƒ์˜ ์„ฌ์œ ๋“ค์ด ํฌํ•จ๋  ๋•Œ ์ „๋„์„ฑ์„ ๊ฐ–๊ฒŒ ๋œ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ „๋„์„ฑ CFRCM ๋‚ด๋ถ€ ์„ฌ์œ ๋“ค์˜ ์นจํˆฌ ์ž„๊ณ„์ ์„ ์•Œ์•„๋ณด๊ธฐ ์œ„ํ•ด ์—ฐ๊ฒฐ๋œ ๋ถ€๋ถ„์ด ํ†ต๊ณผํ•˜๋Š” ํ†ต๋กœ๋ฅผ ํ˜•์„ฑํ•˜๋Š”์ง€๋ฅผ ํ™•์ธํ•˜์˜€๋‹ค. Fig. 11์€ SEM ์ด๋ฏธ์ง€๋ฅผ ํ†ตํ•ด ๊ด€์ฐฐํ•œ FRCM์˜ ์„ฌ์œ ๋ถ„ํฌ ์ƒํƒœ๋ฅผ ๋น„๊ตํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ์‚ฌ์ง„์ด๋‹ค. Fig. 11(a)์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ํƒ„์†Œ์„ฌ์œ ๊ฐ€ ์นจํˆฌ ์ž„๊ณ„์  ์ดํ•˜์ธ 0.1%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์˜ ๊ฒฝ์šฐ ์„ฌ์œ ๋“ค ์‚ฌ์ด์˜ ๊ฑฐ๋ฆฌ๊ฐ€ ๋ฉ€๋ฆฌ ๋–จ์–ด์ ธ ์žˆ์œผ๋ฉฐ, ์ „๋„์„ฑ ๊ฒฝ๋กœ ํ˜•์„ฑ์ด ๋งค์šฐ ๋ถ€์กฑํ•จ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. ๋ฐ˜๋ฉด, Fig. 11(b)์˜ ๊ฒฝ์šฐ 0.3%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์—์„œ ์„ฌ์œ ๋“ค ์‚ฌ์ด์˜ ๊ฑฐ๋ฆฌ๊ฐ€ ๋” ๊ฐ€๊น๊ฒŒ ์žˆ์œผ๋ฉฐ, ์„ฌ์œ ๋“ค์ด ์„œ๋กœ ์ ‘์ด‰ํ•˜๊ธฐ ์‹œ์ž‘ํ•˜์—ฌ ์ „๋„์„ฑ ๊ฒฝ๋กœ๋ฅผ ํ˜•์„ฑํ•˜๊ณ  ์žˆ๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ๋‚ฎ์€ ํ•จ๋Ÿ‰์˜ ํƒ„์†Œ์„ฌ์œ ๊ฐ€ ์ „๋„์„ฑ CFRCM ๋‚ด์— ๋ถ„์‚ฐ๋˜์–ด ์žˆ์ง€๋งŒ ๋Œ€๋ถ€๋ถ„ ํƒ„์†Œ์„ฌ์œ ๊ฐ€ ์ ‘์†๋œ ์ƒํƒœ๋กœ ์กด์žฌํ•˜๊ณ  ์žˆ์Œ์„ ์ž˜ ๋ณด์—ฌ์ฃผ๊ณ  ์žˆ๋‹ค. Fig. 11(c)๋Š” ์นจํˆฌ ์ž„๊ณ„์ ์ธ 0.4%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์—์„œ ํƒ„์†Œ์„ฌ์œ ๋Š” ์‹ญ์žํ˜• ๊ต์ฐจ๋‚˜ ํด๋Ÿฌ์Šคํ„ฐ๋ฅผ ํ˜•์„ฑํ•˜๊ธฐ ์œ„ํ•ด ๊ฒน์ณ์ ธ ์„ฌ์œ ๋“ค์ด ๋‚ด๋ถ€๋ฅผ ํ†ต๊ณผํ•˜๋Š” ์—ฐ๊ฒฐ๋œ ํ†ต๋กœ๋ฅผ ํ˜•์„ฑ๋˜์–ด ์žˆ๋Š” ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์œผ๋ฉฐ, ๋งค์šฐ ๋ฏผ๊ฐํ•œ ํ„ฐ๋„๋ง ํšจ๊ณผ์— ์˜ํ•ด ์ง€๋ฐฐ๋˜์—ˆ๋‹ค. ํ•˜์ง€๋งŒ, Fig. 11(d)๋Š” ํƒ„์†Œ์„ฌ์œ ์˜ ํ˜ผ์ž…๋ฅ ์ด 0.6%๊นŒ์ง€ ์ฆ๊ฐ€ํ•˜๋ฉด ์„ฌ์œ ๊ฐ€ ๋„ˆ๋ฌด ๋งŽ์ด ๊ฒน์น˜๊ณ , ๊ต์ฐจ ์—ฐ๊ฒฐ๋œ ํด๋Ÿฌ์Šคํ„ฐ๊ฐ€ ์ƒ์„ฑ๋˜์–ด ํƒ„์†Œ์„ฌ์œ ์˜ ํ•จ๋Ÿ‰์ด ์นจํˆฌ ์ž„๊ณ„์ ์ด ์ดˆ๊ณผํ•˜์—ฌ ์ „๋„์„ฑ CFRCM์˜ ์ „๋„์„ฑ ๋„คํŠธ์›Œํฌ์˜ ํ˜•์„ฑ์„ ๋ณด์—ฌ์ค€๋‹ค. ์ด ๊ฒฝ์šฐ ํ„ฐ๋„๋ง ํšจ๊ณผ์— ์—ฌ์ „ํžˆ ์ค‘์š”ํ•˜์ง€๋งŒ ์„ฌ์œ ์˜ ์ ‘์ด‰๋ฉด์  ๋ณ€ํ™”์—๋„ ์ „๊ธฐ์ „๋„๋„์— ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•œ๋‹ค. ๋‹ค๋Ÿ‰์˜ ํƒ„์†Œ์„ฌ์œ  ํ˜ผ์ž…์œผ๋กœ ์ธํ•ด ์„œ๋กœ ๋งค์šฐ ๊ทผ์ ‘ํ•˜์—ฌ ์„ฌ์œ ์˜ ํ˜ผ์žก์ด ๋ฐœ์ƒํ•˜์˜€๋‹ค. ์•„์šธ๋Ÿฌ, Fig. 11(e)์™€ (f)์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ๊ฐ•์„ฌ์œ ๊ฐ€ 0.25%์™€ 1.25%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ SFRCM์˜ ๊ฒฝ์šฐ ์„ฌ์œ ๋“ค ์‚ฌ์ด์˜ ๊ฑฐ๋ฆฌ๊ฐ€ ๋ฉ€๋ฆฌ ๋–จ์–ด์ ธ ์žˆ์œผ๋ฉฐ, ์ „๋„์„ฑ ๊ฒฝ๋กœ ํ˜•์„ฑ์ด ๋งค์šฐ ๋ถ€์กฑํ•จ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค.

Fig. 11 SEM images with different fiber volume fractions. (a) Vf=0.1% (b) Vf=0.3% (c) Vf=0.4% (d) Vf=0.6% (e) Vf=0.25% and (f) Vf=1.25%
../../Resources/ksm/jksmi.2022.26.3.72/fig11.png

4.2 SEM/EDS ๋ถ„์„

Fig. 12๊ณผ Table 5์—์„œ๋„ ์ „๋„์„ฑ CFRCM์™€ SFRCM์˜ ํŒŒ๋‹จ๋ฉด์—์„œ ์ฑ„์ทจํ•œ ํƒ„์†Œ์„ฌ์œ ์™€ ๊ฐ•์„ฌ์œ ์˜ SEM ์ด๋ฏธ์ง€์™€ EDS ๋ถ„์„๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์˜ ์„ฑ๋ถ„๋ถ„์„์„ ์œ„ํ•ด SEM์— ๋ถ€์ฐฉ๋˜์–ด ์žˆ๋Š” EDS๋ฅผ ํ†ตํ•ด ์„ฌ์œ ํ‘œ๋ฉด์˜ ๊ตฌ์„ฑ์„ฑ๋ถ„๋Ÿ‰(C, O, Ca, Fe ๋“ฑ)์„ ์ธก์ •ํ•˜์˜€๋‹ค. ์ธก์ •๋ฐฉ๋ฒ•์œผ๋กœ ๊ตฌ์„ฑ์›์†Œ์˜ ์–‘์„ ์ •ํ™•ํžˆ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•ด ์„ฌ์œ  ๋งˆ๋‹ค ๋™์ผํ•˜๊ฒŒ ๊ฑฐ๋ฆฌ๋ฅผ ๋‘๊ณ  ์ž„์˜ ์œ„์น˜์—์„œ 2์  ๋ฉด์ ์˜ ํ‰๊ท ๊ฐ’์„ ๊ตฌํ•˜๋Š” ๋ฐฉ์‹์œผ๋กœ ์›์†Œ์˜ ์–‘์„ ์ธก์ •ํ•˜์˜€๋‹ค. Fig. 12(a)์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ EDS ์ŠคํŽ™ํŠธ๋Ÿผ์— ์˜ํ•œ ์›์†Œ๋ถ„์„ ๊ฒฐ๊ณผ, ํƒ„์†Œ์„ฌ์œ ๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์˜ ๊ฒฝ์šฐ ๋นจ๊ฐ„์ƒ‰ ์œ„์น˜ (1)์— ํ‘œ์‹œ๋œ ์„ฑ๋ถ„์€ ๊ฐ๊ฐ ํƒ„์†Œ(C) 86.65%, ์‚ฐ์†Œ(O) 12.83%์™€ ์†Œ๋Ÿ‰์˜ ์นผ์Š˜(Ca) 0.52%๊ฐ€ ๊ฒ€์ถœ๋˜์—ˆ๋‹ค. ์•„์šธ๋Ÿฌ, ๋นจ๊ฐ„์ƒ‰ ์œ„์น˜ (2)์— ํ‘œ์‹œ๋œ ์„ฑ๋ถ„์€ ํƒ„์†Œ(C) 90.57%, ์‚ฐ์†Œ(O) 8.61%์™€ ์†Œ๋Ÿ‰์˜ ์นผ์Š˜(Ca) 0.82%๋ฅผ ํ•จ์œ ํ•˜๊ณ  ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. ํ•˜์ง€๋งŒ Fig. 12(b)์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ๊ฐ•์„ฌ์œ ๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ SFRCM์—์„œ ํŒŒ๋ž€์ƒ‰ ์œ„์น˜ (1)์— ํ‘œ์‹œ๋œ ์„ฑ๋ถ„์€ ์ฒ (Fe) 64.77%, ํƒ„์†Œ(C) 12.47%, ์‚ฐ์†Œ(O) 10.32%, ์นผ์Š˜(Ca) 10.3%์™€ ์†Œ๋Ÿ‰์˜ ๊ทœ์†Œ(Si) 1.63%, ์•Œ๋ฃจ๋ฏธ๋Š„(AI) 0.51%๊ฐ€ ๊ฒ€์ถœ๋˜์—ˆ๋‹ค. ์•„์šธ๋Ÿฌ, ํŒŒ๋ž€์ƒ‰ ์œ„์น˜ (2)์— ํ‘œ์‹œ๋œ ์„ฑ๋ถ„์€ ์ฒ (Fe) 75.26%, ํƒ„์†Œ(C) 18.26%, ์‚ฐ์†Œ(O) 5.74%์™€ ์†Œ๋Ÿ‰์˜ ์นผ์Š˜(Ca) 0.74%๋ฅผ ํ•จ์œ ํ•˜๊ณ  ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. ๋”ฐ๋ผ์„œ ์ „๋„์„ฑ CFRCM์—์„œ ํƒ„์†Œ์„ฌ์œ ๋Š” ๋‹ค์ˆ˜์˜ ํƒ„์†Œ(C)์™€ ์†Œ๋Ÿ‰์˜ ์นผ์Š˜(Ca)์ด ์กด์žฌํ•˜๋Š” ๊ฒƒ์„ ๋ณด์—ฌ ์ฃผ๊ณ  ์žˆ๋Š” ๋ฐ˜๋ฉด, ์ „๋„์„ฑ SFRCM์—์„œ ๊ฐ•์„ฌ์œ ๋Š” ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋Š”๋ฐ, ์นผ์Š˜(Ca)๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ์†Œ๋Ÿ‰์˜ ๊ทœ์†Œ(Si)์™€ ์•Œ๋ฃจ๋ฏธ๋Š„(Al)์ด ๊ฒ€์ถœ๋˜์–ด ์ˆ˜ํ™”์ž‘์šฉ์ด ํ™œ๋ฐœํ•˜๊ฒŒ ์ง„ํ–‰ํ•˜๊ณ  ์žˆ๋Š” ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค.

Fig. 12 EDS analysis results of the CF and SF captured at the fracture surface in CFRCM and SFRCM
../../Resources/ksm/jksmi.2022.26.3.72/fig12.png
Table 5 EDS analysis results of cement mortars

Spectrum-1

Spectrum-2

Spectrum-3

Spectrum-4

Element

wt.%

wt.%

wt.%

wt.%

C

86.65

90.57

12.47

18.26

O

12.83

8.61

10.32

5.74

Ca

0.52

0.82

10.30

0.74

Si

-

-

1.63

-

Al

-

-

0.51

-

Fe

-

-

64.77

75.26

Total

100.00

100.00

100.00

100.00

4.3 ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์••์ถ•๊ฐ•๋„ ๋ฐœํ˜„์„ฑ๋Šฅ ํ‰๊ฐ€

์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์••์ถ•๊ฐ•๋„๋Š” ์žฌ๋ฃŒ์  ํŠน์„ฑ์„ ํŒŒ์•…ํ•˜๋Š”๋ฐ ์žˆ์–ด์„œ ๊ฐ€์žฅ ๊ธฐ๋ณธ์ ์ธ ๋ณ€์ˆ˜๋กœ ๊ฐ•๋„๋ฅผ ์ธก์ •ํ•˜๋Š” ์š”์†Œ์ด๋‹ค. Table 4์˜ ๋ฐฐํ•ฉ์—์„œ์™€ ๊ฐ™์ด ๋™์ผํ•œ ๋ฐฐํ•ฉ์กฐ๊ฑด์—์„œ ์ „๋„์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์••์ถ•๊ฐ•๋„๋ฅผ ์ธก์ •ํ•˜๊ธฐ ์œ„ํ•ด ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์€ ๋ถ€๋น„ํ”ผ๋กœ 0.25, 0.5, 0.75, 1.0 ๋ฐ 1.25%๊นŒ์ง€ 0.25%์”ฉ ๋ณ€ํ™”๋ฅผ ์ฃผ์–ด ์‹œํŽธ์„ ์ œ์ž‘ํ•˜์˜€์œผ๋ฉฐ, Fig. 13์€ ์–‘์ƒ์žฌ๋ น 28์ผ์—์„œ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ ์ „๋„์„ฑ FRCM์™€ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์••์ถ•๊ฐ•๋„ ์ธก์ •๊ฒฐ๊ณผ๋ฅผ ๋น„๊ตํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ๋ชจ๋“  ์‹œํŽธ์—์„œ ์ „๋„์„ฑ CFRCM์™€ SFRCM์˜ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์••์ถ•๊ฐ•๋„๊ฐ€ ๋ชจ๋‘ ์ ์ฐจ ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. Fig. 13์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ํ‰๊ท  ์••์ถ•๊ฐ•๋„๋Š” 45.9MPa๋กœ ์ธก์ •๋˜์—ˆ์œผ๋ฉฐ, ์ „๋„์„ฑ SFRCM์˜ ๊ฒฝ์šฐ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์— ๋น„ํ•ด ๊ฑฐ์˜ ์œ ์‚ฌํ•˜๊ฑฐ๋‚˜ ์•ฝ๊ฐ„ ๋†’๊ฒŒ ๋‚˜ํƒ€๋‚ด, ๋™๋“ฑํ•œ ์••์ถ•๊ฐ•๋„ ์„ฑ๋Šฅ์„ ๋ฐœํ˜„ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํ•˜์ง€๋งŒ 0.25%์™€ 0.5%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์˜ ๊ฒฝ์šฐ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์— ๋น„ํ•ด ์••์ถ•๊ฐ•๋„๊ฐ€ ๊ฐ๊ฐ 0.8MPa์™€ 3.0 MPa ์ •๋„ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, 0.75%์™€ 1.0%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM๋Š” ๊ฐ๊ฐ 4.8MPa์™€ 8.7MPa ์ •๋„ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํŠนํžˆ, 1.25%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM๋Š” 20.1 MPa ์ •๋„ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋”ฐ๋ผ์„œ 0.25, 0.5, 0.75 ๋ฐ 1.0%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์˜ ์••์ถ•๊ฐ•๋„๋Š” ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์— ๋Œ€๋น„ํ•ด ๋น„์œจ์€ ๊ฐ๊ฐ ์•ฝ 1.7, 6.5, 10.4 ๋ฐ 18.9%๋กœ ๊ฐ•๋„๊ฐ€ ์ €ํ•˜๋˜์—ˆ์œผ๋ฉฐ, 1.25%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM๋Š” ์•ฝ 43.8 %๋กœ ํ˜„์ €ํžˆ ์ €ํ•˜๋˜์—ˆ๋‹ค. 1.25%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM๋Š” ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์—์„œ์˜ ์„ฌ์œ ๊ฐ€ ๊ท ์ผํ•˜๊ฒŒ ๋ถ„์‚ฐ์‹œํ‚ค๊ธฐ๊ฐ€ ์–ด๋ ต๊ณ  ์„ฌ์œ ๋ผ๋ฆฌ ์—‰ํ‚ค๋Š” ๋ญ‰์นจํ˜„์ƒ์ด ๋ฐœ์ƒํ•˜๋ฉฐ, ์ถฉ๋ถ„ํžˆ ๋ถ„์‚ฐ๋˜์ง€ ์•„๋‹ˆํ•˜๊ณ  ๊ณต๊ทน์ฆ๊ฐ€๋กœ ์ธํ•ด ์˜คํžˆ๋ ค ์••์ถ•๊ฐ•๋„๊ฐ€ ํ˜„์ €ํžˆ ๋‚ฎ๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋Š” ํƒ„์†Œ์„ฌ์œ ๋Š” ์„ฌ์œ ํ‘œ๋ฉด์˜ ๋น„์นœ์ˆ˜์„ฑ ๋ฌผ์งˆ๋กœ ์ธํ•ด ๊ฒฝํ™” ํ›„์˜ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์—์„œ ์„ฌ์œ ์™€ ๋งคํŠธ๋ฆญ์Šค ์‚ฌ์ด์˜ ๊ณ„๋ฉด๊ฒฐํ•ฉ๋ ฅ์ด ์•ฝํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์••์ถ•๊ฐ•๋„๊ฐ€ ์ €ํ•˜๋œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด๋Ÿฌํ•œ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋Š” ์„ ํ–‰์˜ ์—ฐ๊ตฌ์—์„œ๋„ ๋ณด๊ณ ๋˜์—ˆ๋‹ค(Dehghani and Aslani, 2020; Heo et al., 2020). ํŠนํžˆ 1.25%๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์˜ ๊ฒฝ์šฐ ์••์ถ•๊ฐ•๋„๊ฐ€ ๊ธ‰๊ฒฉํ•˜๊ฒŒ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ด, ์••์ถ•๊ฐ•๋„ ํ™•๋ณด๋ฅผ ์œ„ํ•œ ๋Œ€์ฑ…์ด ์š”๊ตฌ๋œ๋‹ค.

Fig. 13 The effect of fiber content on the compressive strength of conductive CFRCM and SFRCM versus PM specimens.
../../Resources/ksm/jksmi.2022.26.3.72/fig13.png
Fig. 14 Morphology of the fracture surface of the CFRCM specimens
../../Resources/ksm/jksmi.2022.26.3.72/fig14.png

์•„์šธ๋Ÿฌ, Fig. 14๋Š” SEM ์ด๋ฏธ์ง€ ๋ถ„์„์„ ํ†ตํ•ด CF๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์— ๋Œ€ํ•œ ์„ฌ์œ ์˜ ๋ถ„์‚ฐ์„ฑ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Fig. 14(a)์—์„œ ๋ณด๋Š” ๊ฒƒ์ฒ˜๋Ÿผ ํƒ„์†Œ์„ฌ์œ ์˜ ๊ท ์งˆํ•œ ๋ถ„์‚ฐ์œผ๋กœ ์–‘ํ˜ธํ•œ ์ƒํƒœ๋ฅผ ๋ณด์ธ ๋ฐ˜๋ฉด, Fig. 14(b)๋Š” ํƒ„์†Œ์„ฌ์œ ์˜ ๋ถˆ๊ท ์งˆํ•œ ๋ถ„์‚ฐ์œผ๋กœ ์ธํ•ด ์‹คํƒ€๋ž˜์ฒ˜๋Ÿผ ์‘์ง‘๋˜๊ณ , ์„ฌ์œ ๋‹ค๋ฐœ๋กœ ํ˜•์„ฑํ•˜๊ณ  ์žˆ๋‹ค. ์ด ๋ถ€์œ„์—์„œ ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์ด ์กด์žฌํ•˜์ง€ ์•„๋‹ˆํ•˜๊ณ , ๋งคํŠธ๋ฆญ์Šค ์กฐ์ง ๋‚ด ๊ณต๊ทน์œผ๋กœ ์กด์žฌํ•˜๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋˜๋ฉฐ, ์ผ์ข…์˜ ๊ณต๊ทน ํ˜•ํƒœ๊ฐ€ ์ทจ์•ฝ๋ถ€๋กœ ์ด์–ด์ ธ ์••์ถ•๊ฐ•๋„ ์ €ํ•˜๋กœ ๋ฐœ์ƒํ•œ ๊ฒƒ์œผ๋กœ ์‚ฌ๋ฃŒ๋œ๋‹ค. ๋”ฐ๋ผ์„œ ์ „๋„์„ฑ CFRCM ๋‚ด์—์„œ ํƒ„์†Œ์„ฌ์œ ์˜ ๊ท ์งˆํ•œ ๋ถ„์‚ฐ์„ฑ ํ™•๋ณด๊ฐ€ ์••์ถ•๊ฐ•๋„ ํŠน์„ฑ์— ์ค‘์š”ํ•œ ์˜ํ–ฅ์„ ๋ฏธ์นœ ๊ฒƒ์œผ๋กœ ์˜ˆ์ƒ๋œ๋‹ค.

5. ๊ฒฐ ๋ก 

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ „๋„์„ฑ ์žฌ๋ฃŒ์ธ ํƒ„์†Œ์„ฌ์œ ์™€ ๊ฐ•์„ฌ์œ ๊ฐ€ ํ•จ์œ ๋œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋ฏธ์„ธ๊ตฌ์กฐ ๋ฐ ์ „๊ธฐ์  ํŠน์„ฑ, ์••์ถ•๊ฐ•๋„์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์™€ ๋น„๊ต, ๊ฒ€ํ† ํ•˜์˜€๋‹ค. ๊ทธ ๊ฒฐ๊ณผ ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๊ฒฐ๋ก ์„ ์–ป์—ˆ๋‹ค.

1. ๋ชจ๋“  ์‹œํŽธ์—์„œ ์–‘์ƒ์žฌ๋ น์ด ๊ฒฝ๊ณผ๋จ์— ๋”ฐ๋ผ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ๋น„์ €ํ•ญ์ด ์ ์ฐจ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. ์ด๋Š” ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋‚ด์—์„œ ์ž์œ ์ˆ˜๊ฐ€ ์ฆ๋ฐœํ•˜๊ณ  ์ˆ˜ํ™”์ž‘์šฉ์ด ์ง„ํ–‰๋จ์— ๋”ฐ๋ผ ์ž์œ ์ˆ˜๋ฅผ ๊ฐ์†Œ์‹œํ‚จ ๊ฒƒ์— ๊ธฐ์ธํ•œ ๊ฒฐ๊ณผ๋ผ๊ณ  ํŒ๋‹จ๋œ๋‹ค. ์ด๋Ÿฌํ•œ ํ˜„์ƒ์€ ์–‘์ƒ์žฌ๋ น์ด ๊ฒฝ๊ณผ๋˜๋ฉด์„œ ์ง€์†์ ์ด๋ฉฐ ๋น„์ €ํ•ญ์˜ ๋ณ€ํ™”๊ฐ€ ๋‹ค์–‘ํ•˜๊ฒŒ ๋ฐœ์ƒํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค.

2. ์ „๋„์„ฑ CFRCM๊ณผ SFRCM์˜ ๋น„์ €ํ•ญ์ด ํ™•์—ฐํžˆ ์„œ๋กœ ์ƒ์ดํ•จ์„ ํ™•์ธํ•˜์˜€์œผ๋ฉฐ, 0.4% ์ด์ƒ ํ•จ์œ ๋œ ํƒ„์†Œ์„ฌ์œ ์˜ ๊ฒฝ์šฐ ์„ฌ์œ ๋“ค๋ผ๋ฆฌ์˜ ์—ฐ๊ฒฐ์ด ์™„์ „ํ•ด์ ธ์„œ ๋น„์ €ํ•ญ์ด ํ˜„์ €ํžˆ ๊ฐ์†Œํ•˜์˜€๋‹ค. ๋ณธ ์‹คํ—˜์— ์‚ฌ์šฉ๋œ ์ „๋„์„ฑ CFRCM์—์„œ ๊ฐ์ง€๋œ ์นจํˆฌ ์ „์ด์˜์—ญ์€ 0.1โˆผ0.4% ์ •๋„๋กœ ํŒ๋‹จ๋˜๋ฉฐ, 0.5โˆผ0.6%์—์„œ๋Š” ์ „๋„์„ฑ ๊ฒฝ๋กœ๊ฐ€ ์ด๋ฏธ ํ˜•์„ฑ๋˜์–ด ์™„๋งŒํ•œ ์ฆ๊ฐ€๋กœ ๊ทธ ์ฆ๊ฐ€์œจ์€ ๋‘”ํ™”๋˜์—ˆ๋‹ค.

3. SEM/EDS ๊ด€์ฐฐ์„ ํ†ตํ•ด CF๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ CFRCM์—์„œ ํƒ„์†Œ์„ฌ์œ ์˜ ๋ถˆ๊ท ์งˆํ•œ ๋ถ„์‚ฐ์œผ๋กœ ์„ฌ์œ  ๋ฉ์–ด๋ฆฌ๋‚˜ ์„ฌ์œ ๋ญ‰์นจ์ด ํ˜•์„ฑ๋จ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด๋Ÿฌํ•œ ๋ถ€์œ„์—์„œ ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์ด ์กด์žฌํ•˜์ง€ ์•„๋‹ˆํ•˜๊ณ , ์ผ์ข…์˜ ๊ณต๊ทน ํ˜•ํƒœ์ธ ์ทจ์•ฝ๋ถ€๋กœ ์ด์–ด์ ธ ์••์ถ•๊ฐ•๋„ ์ €ํ•˜๊ฐ€ ๋ฐœ์ƒํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ํ•˜์ง€๋งŒ SF๊ฐ€ ํ•จ์œ ๋œ ์ „๋„์„ฑ SFRCM์˜ ๊ฒฝ์šฐ ์„ฌ์œ ํ‘œ๋ฉด ์ฃผ๋ณ€์œผ๋กœ ์‹œ๋ฉ˜ํŠธ์˜ ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ ๊ฒฐ์ •ํ˜•์„ฑ์œผ๋กœ ์น˜๋ฐ€ํ•œ ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด ๋ฏธ์„ธ๊ตฌ์กฐ์˜ ์กฐ์ง์„ ๊ฐ–๊ฒŒ ๋˜๋ฉฐ, ์ด๋กœ ์ธํ•œ ์••์ถ•๊ฐ•๋„ ์ฆ์ง„์˜ ํšจ๊ณผ๊ฐ€ ๋ฐœ์ƒํ•œ ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์—ˆ๋‹ค.

4. ์ „๋„์„ฑ SFRCM์˜ ๊ฒฝ์šฐ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์— ์ƒ๊ด€์—†์ด ํ”Œ๋ ˆ์ธ ๋ชจ๋ฅดํƒ€๋ฅด์— ๋น„ํ•ด ๊ฑฐ์˜ ์œ ์‚ฌํ•˜๊ฑฐ๋‚˜ ๋™๋“ฑ ์ด์ƒ์˜ ์••์ถ•๊ฐ•๋„๋ฅผ ๋ฐœํ˜„ํ•œ ๋ฐ˜๋ฉด, ์ „๋„์„ฑ CFRCM์˜ ์••์ถ•๊ฐ•๋„๋Š” ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์ƒ๋‹นํžˆ ์ €์กฐํ•œ ๊ฐ•๋„๋ฐœํ˜„์„ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

์œ„์˜ ์‹คํ—˜๊ฒฐ๊ณผ๋กœ๋ถ€ํ„ฐ, ์‹œ๋ฉ˜ํŠธ ๋ชจ๋ฅดํƒ€๋ฅด์˜ ์ „๊ธฐ์ €ํ•ญ ์ธก์ •๊ฒฐ๊ณผ ๊ฐ’๋“ค์€ ์‹œํŽธ ๋‚ด๋ถ€์— ํฌํ•จ๋œ ๊ณต๊ทน๊ณผ ์ž์œ ์ˆ˜ ์กด์žฌ๋กœ ์ „๋„์„ฑ FRCM์˜ ๋ถ„์‚ฐ์ •๋„์˜ ์˜ํ–ฅ์„ ๋ฐ›์•„ ์ „๊ธฐ์ €ํ•ญ ๊ฐ’์˜ ํŽธ์ฐจ๊ฐ€ ํฌ๊ฒŒ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ์œผ๋ฏ€๋กœ ์ด์— ๋Œ€ํ•œ ์„ธ๋ฐ€ํ•œ ๊ฒ€ํ† ๊ฐ€ ์š”๊ตฌ๋œ๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

์ด ๋…ผ๋ฌธ์€ 2018๋…„๋„ ์ •๋ถ€(๊ต์œก๋ถ€)์˜ ์žฌ์›์œผ๋กœ ํ•œ๊ตญ์—ฐ๊ตฌ์žฌ๋‹จ์˜ ์ง€์›์„ ๋ฐ›์•„ ์ˆ˜ํ–‰๋œ ๊ธฐ์ดˆ์—ฐ๊ตฌ์‚ฌ์—…์ž…๋‹ˆ๋‹ค (Grant No. NRF-2018R1A6A1A03025542).

References

1 
ACI Committee 544, (2018), Guide to Design with Fiber- Reinforced Concrete(ACI 544.4R-18), Hills, MI 48331; American Concrete Institute (ACI).Google Search
2 
Belli, A., Mobili, A., Bellezze, T., Tittarelli, F. (2020), Commercial and Recycled Carbon/Steel Fibers for Fiber-Reinforced Cement Mortars with High Electrical Conductivity, Cement and Concrete Composites, 109(2020), 103569DOI
3 
Brandt, A.M. (2008), Fibre Reinforced Cement-Based(FRC) Composites after over 40 Years of Development in Building and Civil Engineering, Composites Structures, 86, 3-9.DOI
4 
Lee, H.J., Lim, H.J. (2018), Evaluation of Setting Delay in Mortar Adding Superplasticizer Using Electrical Resistivity Measurement, Journal of the Korea Institute for Structural Maintenance and Inspection, 22(6), 9-15.DOI
5 
McCarter, W.J., Starrs, G., Chrisp, T.M. (2000), Electrical Conductivity, Diffusion, and Permeability of Portland Cement-Based Mortars, Cement and Concrete Research, 30(9), 1395-1400.DOI
6 
Chiarello, M., Zinno, R. (2005), Electrical Conductivity of Self-Monitoring CFRC, Cement and Concrete Composites, 27(4), 463-469.DOI
7 
Han, B., Ding, S.D., Yu, X. (2015), Intrinsis Self-Sensing Concrete and Structures: A Review, Measurement, 59(2015), 110-128.DOI
8 
Yildirim, G., ร–ztรผrk, O., Al-Dahawi, A., Ulu, A.A., Sahmaran, M. (2020), Self-Sensing Capability of Engineered Cementitious Composites: Effects of Aging and Loading Conditions, Construction and Building Materials, 231(2020), 117132DOI
9 
Lim, Y.C. (2018), Experimental Study on the Effect of Specimen Size on Electrical Resistivity Measurement, Journal of the Korea Institute for Structural Maintenance and Inspection, 22(6), 164-169.DOI
10 
Yoon, I.S. (2013), Influence of Micro-Structural Characteristics of Concrete on Electrical Resistivity, Journal of the Korea Institute for Structural Maintenance and Inspection, 17(6), 122-129.DOI
11 
Kang, S.H. (1998), Electrically Conductive Concrete, Magazin of the Koea Concrete Institute, 10(6), 34-40.Google Search
12 
Chung, D.D.L. (2004), Electrically Conductive Cement-Based Materials, Advances in Cement Research, 16(4), 167-176.DOI
13 
Han, B., Guan, X., Ou, J. (2007), Electrode Design Measuring Method and Data Acquisition System of Carbon Fiber Cement Paste Piezoresistive Sensors, Sensors and Actuators A: Physical, 135(2), 360-369.DOI
14 
Kang, M.S., Kang, M.S., Lee, H.J., Yim, H.J., An, Y.K. (2018), Crack Initiation and Temperature Variation Effects on Self-Sensing Impedance Responses of FRCCs, Journal of the Korea Institute for Structural Maintenance and Inspection, 22(3), 69-74.DOI
15 
Lee, N.K., Park, G.J., Park, J.J., Kim, S.W. (2019), A Study on the Electrical Conductivity and Electromagnetic Shielding of High Performance Fiber Reinforced Cementitious Composites(HPFRCC), Journal of the Korea Institute for Structural Maintenance and Inspection, 23(2), 37-43.DOI
16 
Xie, P., Gu, P., Beaudoin, J.J. (1996), Electrical Percolation Phenomena in Cement Composites Containing Conductive Fibres, Journal of Materials Science, 31, 4093-4097.DOI
17 
KSL ISO 679, (2016), Methods of Testing Cements- Determination of Strength, Seoul, Korea: Korea Agency for Technology and Standards (KATS).Google Search
18 
EI-Enein, S.A., Kotkata, M.F., Hanna, G.B., Sadd, M., EI Razek, M.M.A. (1995), Electrical Conductivity of Concrete Containing Silica Fume, Cement and Concrete Research, 25(8), 1615-1620.DOI
19 
Wang, C., Jiao, G.S., Li, B.L., Peng, L., Feng, Y., Gao, N., Li, K.Z. (2017), Dispersion of Carbon Fibers and Conductivity of Carbon Fiber-Reinforced Cement-Based Composites, Ceramics International, 43(17), 15122-15132.DOI
20 
Whittington, H., McCarter, J., Forde, M. (1981), The Conduction of Electricity Through Concrete, Magazin of Concrete Research, 33, 48-60.DOI
21 
Dehghani, A., Aslani, F. (2020), The Effect of Shape Memory Alloy, Steel, and Carbon Fibres on Fresh, Mechanical, and Electrical Properties of Self-Compacting Cementitious Composites, Cement and Concrete Composites, 112(2020), 103659DOI
22 
Heo, G.H., Park, J.G., Song, K.C., Park, J.H., Jun, H.M. (2020), Mechanical Properties of SiO2-Coated Carbon Fiber-Reinforced Mortar Composites with Different Fiber Length and Fiber Volume Fractions, Advances in Civil Engineering, (2020) 8881273DOI