Mobile QR Code QR CODE
Export citation EndNote

  1. ๊ณ ๋ ค๋Œ€ํ•™๊ต ๊ฑด์ถ•์‚ฌํšŒํ™˜๊ฒฝ๊ณตํ•™๊ณผ ๋ฐ•์‚ฌ๊ณผ์ • (Graduate Student, School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Rep. of Korea)
  2. ๊ณ ๋ ค๋Œ€ํ•™๊ต ๊ฑด์ถ•์‚ฌํšŒํ™˜๊ฒฝ๊ณตํ•™๊ณผ ์„์‚ฌ (Master, School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Rep. of Korea)
  3. ๊ณ ๋ ค๋Œ€ํ•™๊ต ๊ฑด์ถ•์‚ฌํšŒํ™˜๊ฒฝ๊ณตํ•™๊ณผ ์„์‚ฌ๊ณผ์ • (Graduate Student, School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Rep. of Korea)
  4. ๊ณ ๋ ค๋Œ€ํ•™๊ต ๊ฑด์ถ•์‚ฌํšŒํ™˜๊ฒฝ๊ณตํ•™๊ณผ ๊ต์ˆ˜ (Professor, School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Rep. of Korea)



๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ, ๊ธฐ๊ฑด๋ฐ€๋„, ๊ฐ•๋„, ์ „๊ธฐ ๋น„์ €ํ•ญ, ์ฐจํ ํšจ๊ณผ
lightweight aggregate concrete, air dry density, strength, electrical resistivity, shielding effectiveness

1. ์„œ ๋ก 

์ตœ๊ทผ ์ •๋ณดํ†ต์‹ ๊ธฐ์ˆ ์˜ ๋ฐœ์ „์— ๋”ฐ๋ผ ์ธ๋ฅ˜์˜ ์ „์ž๊ธฐ๊ธฐ ์‚ฌ์šฉ๋Ÿ‰์ด ์ฆ๊ฐ€ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ์ด์™€ ๋™์‹œ์— ์ „์žํŒŒ ์ฐจํ์— ๊ด€ํ•œ ๊ด€์‹ฌ๋„ ์ฆ๊ฐ€ํ•˜๊ณ  ์žˆ๋‹ค. EMI์— ์˜ํ•ด ๊ฑด๋ฌผ ์™ธ๋ถ€์˜ ์ „์žํŒŒ๊ฐ€ ๊ฑด๋ฌผ ๋‚ด ์ „์ž๊ธฐ๊ธฐ์˜ ์ „๊ธฐํšŒ๋กœ๋ฅผ ํŒŒ๊ดดํ•จ์œผ๋กœ์จ, ์ „์ž๊ธฐ๊ธฐ์˜ ์˜ค์ž‘๋™ ๋ฐ ๊ณ ์žฅ์ด ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋‹ค(Hyun et al. 2012;Yehia et al. 2014). ์ด๋Ÿฌํ•œ ํ˜„์ƒ์„ ๋ฐฉ์ง€ํ•˜๊ธฐ ์œ„ํ•ด, ์ „์žํŒŒ ์ฐจํ๋Š” ๊ตฐ์‚ฌ์‹œ์„ค๋ฟ๋งŒ ์•„๋‹ˆ๋ผ, ์˜๋ฃŒ๊ธฐ๊ธฐ, ํ†ต์‹  ๋“ฑ ๋‹ค์–‘ํ•œ ๋ถ„์•ผ์— ์ ์šฉ๋˜๊ณ  ์žˆ๋‹ค(Yehia et al. 2014;Choi et al. 2020;Chung 2020). ๋Œ€๋ถ€๋ถ„์˜ ๊ฑด๋ฌผ์€ ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ตฌ์กฐ๋กœ ๊ฑด์„ค๋˜๊ธฐ ๋•Œ๋ฌธ์— ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „์žํŒŒ ์ฐจํ ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜๋Š” ๊ฒƒ์€ ๋งค์šฐ ์ค‘์š”ํ•˜๋‹ค(Hyun et al. 2014).

์ผ๋ฐ˜์ ์ธ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์ „๊ธฐ ์ „๋„์„ฑ์ด ๋‚ฎ์€ ์žฌ๋ฃŒ๋กœ, ์ „๋„์„ฑ ์žฌ๋ฃŒ๋ฅผ ํ˜ผ์ž…ํ•จ์œผ๋กœ์จ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ์  ํŠน์„ฑ์„ ํ–ฅ์ƒ์‹œํ‚ฌ ์ˆ˜ ์žˆ๋‹ค. ๋‹ค์ˆ˜์˜ ์—ฐ๊ตฌ์ž(Wang et al. 2016;Yoo et al. 2020)๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ ์ „๋„์„ฑ์ด ์šฐ์ˆ˜ํ• ์ˆ˜๋ก ์ „์žํŒŒ ์ฐจํ ์„ฑ๋Šฅ๋„ ์šฐ์ˆ˜ํ•ด์ง€๋Š” ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ํ•˜๊ณ  ์žˆ๋‹ค. ์ด๋Š” ์ „๋„์„ฑ ์žฌ๋ฃŒ๊ฐ€ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด์— ๊ณ ๋ฅด๊ฒŒ ๋ถ„ํฌ๋œ ๊ฒฝ์šฐ, ์ „๋„์„ฑ ์žฌ๋ฃŒ๋Š” ์ „์ž์˜ ์ด๋™๊ฒฝ๋กœ์ธ ์ „๋„์„ฑ ๊ฒฝ๋กœ๋ฅผ ํ˜•์„ฑํ•˜๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค. ์ „๋„์„ฑ ์žฌ๋ฃŒ๋กœ๋Š” ์นด๋ณธ๋‚˜๋…ธํŠœ๋ธŒ(carbon nanotube, CNT), ํƒ„์†Œ์„ฌ์œ (carbon fiber), ๊ฐ•์„ฌ์œ (steel fiber) ๋“ฑ์ด ์žˆ์œผ๋ฉฐ, ์ตœ๊ทผ์—๋Š” ์‚ฐ์—…๋ถ€์‚ฐ๋ฌผ์ธ ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ๋„ ์ „๋„์„ฑ ์žฌ๋ฃŒ๋กœ ํ™œ์šฉ๋˜๊ณ  ์žˆ๋‹ค(Hong et al. 2020b).

ํ•œํŽธ, ์ตœ๊ทผ์˜ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ ๊ฑด์„ค ์‚ฐ์—…์—์„œ๋Š” ๊ตฌ์กฐ๋ฌผ์˜ ๊ฒฝ๋Ÿ‰ํ™”๊ฐ€ ํ™”๋‘๋กœ ๋– ์˜ค๋ฅด๊ณ  ์žˆ๋‹ค. ๊ตฌ์กฐ๋ฌผ์„ ๊ฒฝ๋Ÿ‰ํ™”์‹œํ‚ฌ ์ˆ˜ ์žˆ๋Š” ๋Œ€ํ‘œ์ ์ธ ๋ฐฉ๋ฒ•์€ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋ฅผ ํ™œ์šฉํ•˜๋Š” ๊ฒƒ์ด๋ฉฐ, ์ด์— ๋”ฐ๋ผ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๊ด€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ํ™œ๋ฐœํ•˜๊ฒŒ ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค(Kim and Lee 2011;Kim et al. 2020). ํ•˜์ง€๋งŒ, ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋Š” ๋‚ด๋ถ€์— ๊ณต๊ทน์ด ๋‹ค๋Ÿ‰์œผ๋กœ ๋ถ„ํฌํ•˜์—ฌ ์™ธ๋ ฅ์— ์ทจ์•ฝํ•  ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด ๋ฐฐํ•ฉ์ˆ˜๋ฅผ ํก์ˆ˜ํ•˜์—ฌ ์œ ๋™์„ฑ์˜ ์ €ํ•˜๋ฅผ ์œ ๋ฐœํ•˜๋Š” ๊ฒƒ์œผ๋กœ ์•Œ๋ ค์ ธ ์žˆ๋‹ค(Kim et al. 2020;Ankur and Singh 2021). ์ด๋กœ ์ธํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ’ˆ์งˆ ์ €ํ•˜ ๋ฐ ๊ฐ•๋„ ๊ฐ์†Œ๊ฐ€ ๋‚˜ํƒ€๋‚˜๊ฒŒ ๋œ๋‹ค. ๋”ฐ๋ผ์„œ ๊ณ ํ’ˆ์งˆ์˜ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ํ™•๋ณดํ•˜๊ณ  ์ด์— ๋Œ€ํ•œ ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜๋Š” ๊ฒƒ์ด ์ค‘์š”ํ•˜๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋Œ€ํ•œ ๊ธฐ์ดˆ์ž๋ฃŒ๋ฅผ ์ œ๊ณตํ•˜๊ณ ์ž, ๋ฐ”ํ…€์• ์‹œ๊ณ„ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋ฅผ ํ™œ์šฉํ•˜์—ฌ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฐ•๋„ ๋ฐ ์ „๊ธฐ์  ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜์˜€๋‹ค.

2. ์‹คํ—˜๊ณ„ํš ๋ฐ ๋ฐฉ๋ฒ•

2.1 ์‹คํ—˜๊ณ„ํš

๋ณธ ์—ฐ๊ตฌ์—์„œ ์‚ฌ์šฉํ•œ ๋ณ€์ˆ˜๋“ค์˜ ๋ฐฐํ•ฉ์ƒ์„ธ๋Š” Table 1๊ณผ ๊ฐ™๋‹ค. ๋ฌผ-๋ฐ”์ธ๋”๋น„(water to binder ratio, w/b)๋Š” 0.325, 0.200์œผ๋กœ ์„ค์ •ํ•˜์˜€์œผ๋ฉฐ, ๊ฒฐํ•ฉ์žฌ๋กœ๋Š” ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ์ค‘ ๋ฏธ๋ถ„๋ง ํ˜•ํƒœ์˜ ์ „๊ธฐ๋กœ ์‚ฐํ™”์Šฌ๋ž˜๊ทธ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๋‹ค์ˆ˜์˜ ์—ฐ๊ตฌ์ž๋Š” ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์„ ํ™œ์šฉํ•˜์—ฌ, ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ฏธ์„ธ๊ตฌ์กฐ(Hong et al. 2019), ๊ฐ•๋„(Roslan et al. 2016), ๋‚ด๊ตฌ์„ฑ(Hong et al. 2021)์„ ํ‰๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์˜ ์น˜ํ™˜์œจ์ด 15 % ์ด๋‚ด์—์„œ๋Š” ๊ฐ•๋„์ €ํ•˜, ๋‚ด๊ตฌ์„ฑ ์ €ํ•˜ ๋“ฑ์˜ ์—ดํ™”๊ฐ€ ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚˜์ง€ ์•Š๋Š” ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ํ•˜๊ณ  ์žˆ๋‹ค. ์ด ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋“ค์— ๊ธฐ๋ฐ˜ํ•˜์—ฌ ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์˜ ์น˜ํ™˜์œจ์„ 15 %๋กœ ์ ์šฉํ•˜์—ฌ ๋ฐฐํ•ฉ๋ณ€์ˆ˜๋ฅผ ์„ค์ •ํ•˜์˜€๋‹ค. ๋˜ํ•œ, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์—ฐ์„ฑ๋Šฅ๋ ฅ์„ ๊ฐœ์„ ์‹œํ‚ค๊ธฐ ์œ„ํ•ด ํ›„ํฌํ˜• ๊ฐ•์„ฌ์œ ๋ฅผ 0.75 % ํ˜ผ์ž…ํ•˜์˜€๋‹ค. ์ถ”๊ฐ€๋กœ, ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ๋ฅผ ๋ฐ”ํ…€์• ์‹œ๊ณ„ ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋กœ 100 % ์น˜ํ™˜ํ•˜์—ฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฒฝ๋Ÿ‰ํ™”๋ฅผ ๊ณ ๋ คํ•˜์˜€์œผ๋ฉฐ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ด 4 ๋ณ€์ˆ˜์— ๋Œ€ํ•œ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. Fig. 1์€ ๋ณ€์ˆ˜๋ช…์— ๋Œ€ํ•œ ์„ค๋ช…์ด๋ฉฐ, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์˜ ์น˜ํ™˜์œจ์ด 0 %์ธ Plain ๋ณ€์ˆ˜๋Š” NN์œผ๋กœ, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์ด 15 % ํ˜ผ์ž…๋œ ๋ณ€์ˆ˜๋Š” ES15๋กœ ๋ช…๋ช…ํ•˜์˜€๋‹ค. ๋˜ํ•œ, ๊ฐ•์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋œ ๊ฒฝ์šฐ์—๋Š” ๋’ค์— SF๋ฅผ ์ถ”๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ๋ฅผ ํ™œ์šฉํ•  ๊ฒฝ์šฐ NA, ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋ฅผ ํ™œ์šฉํ•  ๊ฒฝ์šฐ LA๋กœ ํ‘œ๊ธฐํ•˜์˜€๋‹ค.

Table 1 Mix designs of concrete specimens

Mix

w/b

(%)

Unit weight (kg/m$^{3}$)

SF

(vol. %)

SP

(wt. %)

AEA

(wt. %)

Slump

(mm)

W

C

ES

FA

NA

LA

NA-NN

32.5

170

523

-

657

971

-

-

0.57

0.02

175

NA-ES15

32.5

170

445

79

657

971

-

-

0.67

0.02

210

LA-ES15

20.0

160

680

120

584

-

569

-

0.66

0.02

155

LA-ES15-SF

20.0

160

680

120

584

-

569

0.75

0.69

0.02

175

Note: w/b: water to binder ratio; W: water; C: cement; ES: electric arc furnace oxidizing slag powder; FA: fine aggregate; NA: normal coarse aggregate; LA: lightweight coarse aggregate; SF: steel fiber; SP: superplasticizier; AEA: air entraining agent
Fig. 1 Designations of test specimens
../../Resources/KCI/JKCI.2022.34.2.153/fig1.png

2.2 ์‚ฌ์šฉ์žฌ๋ฃŒ

Fig. 2๋Š” ๋ณธ ์—ฐ๊ตฌ์—์„œ ์‚ฌ์šฉํ•œ ๊ฒฐํ•ฉ์žฌ์™€ ๊ณจ์žฌ์˜ ์ž…๋„ ๋ถ„ํฌ๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ์‹œ๋ฉ˜ํŠธ๋Š” 1์ข… ๋ณดํ†ต ํฌํ‹€๋žœ๋“œ ์‹œ๋ฉ˜ํŠธ๋กœ์„œ 3,413 cm$^{2}$/g์˜ blaine์„ ๊ฐ€์ง€๋ฉฐ, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์€ ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๊ณจ์žฌ๋ฅผ ๋ณผ๋ฐ€(ball mill)์— ๋„ฃ์–ด ๋ถ„์‡„ํ•จ์œผ๋กœ์จ ์•ฝ 4,893 cm$^{2}$/g์˜ blaine์„ ํ™•๋ณดํ•˜์˜€๋‹ค(Hong et al. 2020b). ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋Š” ๊ตญ๋‚ด์—์„œ ์ƒ์‚ฐ๋œ ์ตœ๋Œ€์น˜์ˆ˜ 20 mm์˜ ๋ถ„์‡„ํ˜• ๋ฐ”ํ…€์• ์‹œ๊ณ„ ๊ตต์€๊ณจ์žฌ๋กœ, ํก์ˆ˜์œจ ๋ฐ ์ ˆ๊ฑด๋ฐ€๋„๋Š” ๊ฐ๊ฐ 1.76 g/cm3 ๋ฐ 6.1 %๋กœ ์ธก์ •๋˜์—ˆ๋‹ค(Hong et al. 2020a). ๊ณจ์žฌ๋“ค์˜ ์ž…๋„ ๋ถ„ํฌ๋Š” ์ผ๋ฐ˜์ฝ˜ํฌ๋ฆฌํŠธ(MOLIT 2021a)์™€ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ(MOLIT 2021b) ๋‚ด ํ‘œ์ค€ ์ž…๋„ ๋ถ„ํฌ ๋ฒ”์œ„๋ฅผ ๋ชจ๋‘ ๋งŒ์กฑํ•˜์˜€๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ ํ™œ์šฉํ•œ ๊ฒฐํ•ฉ์žฌ ๋ฐ ๊ณจ์žฌ์˜ ํ™”ํ•™์  ํŠน์„ฑ์€ Table 2์— ๋‚˜ํƒ€๋‚˜ ์žˆ์œผ๋ฉฐ, ๊ฐ•์„ฌ์œ ์˜ ๋ฌผ๋ฆฌ์  ํŠน์„ฑ์€ Table 3๊ณผ ๊ฐ™๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋ชฉํ‘œ์Šฌ๋Ÿผํ”„๋ฅผ 180ยฑ30 mm๋กœ ์„ค์ •ํ•˜์˜€์œผ๋ฉฐ, ์œ ๋™์„ฑ ํ™•๋ณด๋ฅผ ์œ„ํ•ด ํด๋ฆฌ์นด๋ฅด๋ณธ์‚ฐ๊ณ„ ๊ณ ์„ฑ๋Šฅ๊ฐ์ˆ˜์ œ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ํ•œํŽธ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋Š” ๊ณต๊ทน์ด ๋งŽ์•„ ์ˆ˜๋ถ„์„ ํก์ˆ˜ํ•˜๋Š” ์„ฑ์งˆ์ด ๊ฐ•ํ•˜์—ฌ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐฐํ•ฉ ์‹œ ์œ ๋™์„ฑ์„ ์†์‹ค์‹œํ‚ค๋ฉฐ, ์ด๋Š” ๋™์‹œ์— ๊ณ ์„ฑ๋Šฅ๊ฐ์ˆ˜์ œ์˜ ์‚ฌ์šฉ๋Ÿ‰์„ ์ฆ๊ฐ€์‹œํ‚จ๋‹ค(Kim et al. 2020). ํ•˜์ง€๋งŒ ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” Hong et al.(2020a)์ด ์ œ์•ˆํ•œ ๊ฒฝ๋Ÿ‰์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ œ์กฐ๋ฐฉ๋ฒ•์— ๋”ฐ๋ผ ๋ฐฐํ•ฉ์„ ์ˆ˜ํ–‰ํ•˜์—ฌ ์œ ๋™์„ฑ์˜ ์†์‹ค์„ ์ตœ์†Œํ™”ํ•˜์˜€๋‹ค. ๋จผ์ €, ๊ฐ•์žฌ์‹ ๋ฏน์„œ๋ฅผ ํ™œ์šฉํ•˜์—ฌ ๊ณจ์žฌ๋“ค์„ ๊ฑด๋น„๋น”ํ•˜์˜€์œผ๋ฉฐ, ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ๋‚ด๋ถ€๋กœ ์ˆ˜๋ถ„์„ ์นจํˆฌ์‹œํ‚ค๊ธฐ ์œ„ํ•ด ๋ฐฐํ•ฉ์ˆ˜์˜ ์ ˆ๋ฐ˜์„ ์‚ฌ์šฉํ•˜์—ฌ 5๋ถ„ ์ด์ƒ ํ˜ผํ•ฉํ•˜์˜€๋‹ค. ์ดํ›„, ๊ฒฐํ•ฉ์žฌ, ๋‚จ์€ ๋ฐฐํ•ฉ์ˆ˜, ๊ฐ์ˆ˜์ œ ๋ฐ ๊ณต๊ฐœ์—ฐํ–‰์ œ๋ฅผ ํ˜ผ์ž…ํ•˜์—ฌ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ์ œ์กฐํ•˜์˜€๋‹ค. ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ณต๊ธฐ๋Ÿ‰์€ 5.5ยฑ1.5 %์˜ ๋ฒ”์œ„๋ฅผ ๋งŒ์กฑํ•˜์˜€๋‹ค(MOLIT 2021b).

Fig. 2 Size distribution of binders and aggregates
../../Resources/KCI/JKCI.2022.34.2.153/fig2.png
Table 2 Chemical properties of binders and aggregates

Content

Binders

Aggregates

C

ES

FA

NA

LA

SiO$_{2}$

17.9

14.2

66.8

61.8

60.9

CaO

65.5

22.1

1.43

2.51

3.49

Al$_{2}$O$_{3}$

4.67

11.1

17.6

17.8

17.0

Fe$_{2}$O$_{3}$

2.79

39.9

2.38

4.54

9.64

MgO

2.65

3.33

0.85

3.76

1.89

SO$_{3}$

4.65

0.02

0.25

0.77

0.13

MnO

0.10

5.59

0.06

0.10

0.11

TiO$_{2}$

0.27

0.69

0.31

0.76

1.01

Table 3 Chemical properties of steel fibers

Type

Diameter

(mm)

Length

(mm)

Aspect ratio

Tensile strength

(MPa)

Hooked-end

0.55

35

64

1,250

2.3 ์‹คํ—˜๋ฐฉ๋ฒ•

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ฐ€๋„๋Š” ASTM C567 (2020)์— ์˜๊ฑฐํ•˜์—ฌ ์ธก์ •ํ•˜์˜€๋‹ค. ์ ˆ๊ฑด๋ฐ€๋„์— ๋Œ€ํ•œ ์‹œํ—˜์ฒด๋Š” ํƒ€์„ค ํ›„ ํ•˜๋ฃจ ๋’ค์— ํƒˆํ˜•ํ•˜์˜€์œผ๋ฉฐ, ์ดํ›„ ์›์ฃผํ˜• ์‹œํ—˜์ฒด์˜ ์ˆ˜์ค‘์งˆ๋Ÿ‰์„ ์ธก์ •ํ•˜์˜€๋‹ค. ์ธก์ • ํ›„์—๋Š” ์‹œํ—˜์ฒด ํ‘œ๋ฉด์˜ ์ˆ˜๋ถ„์„ ์ œ๊ฑฐํ•˜์—ฌ ํ‘œ๋ฉด๊ฑด์กฐ ํฌํ™”์ƒํƒœ์˜ ์‹œํ—˜์ฒด ์งˆ๋Ÿ‰์„ ์ธก์ •ํ•˜์˜€๊ณ  ๊ทธ ํ›„ 3์ผ๋™์•ˆ 110ยฑ5 ยฐC์˜ ์˜จ๋„๋กœ ์‹œํ—˜์ฒด๋ฅผ ๊ฑด์กฐ์‹œ์ผฐ๋‹ค. ์‹ (1)์€ ์ ˆ๊ฑด๋ฐ€๋„์˜ ๊ณ„์‚ฐ์‹์ด๋‹ค.

(1)
$O_{m}=(D\times 997)/(F-G)$

์—ฌ๊ธฐ์„œ, $O_{m}$์€ ์ ˆ๊ฑด๋ฐ€๋„, $D$๋Š” 3์ผ ๊ฑด์กฐ ํ›„์˜ ์‹œํ—˜์ฒด ์งˆ๋Ÿ‰, $F$๋Š” ํ‘œ๋ฉด๊ฑด์กฐ ํฌํ™”์ƒํƒœ์˜ ์‹œํ—˜์ฒด ์งˆ๋Ÿ‰, $G$๋Š” ์ˆ˜์ค‘์งˆ๋Ÿ‰์„ ์˜๋ฏธํ•œ๋‹ค.

๊ธฐ๊ฑด๋ฐ€๋„๋ฅผ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•ด, ์‹œํ—˜์ฒด๋Š” 7์ผ๊ฐ„ ํ‘œ์ค€์–‘์ƒ์„ ์ง„ํ–‰ํ•˜์˜€๋‹ค. ์ดํ›„, ํ•˜๋ฃจ ๋™์•ˆ 23ยฑ2 ยฐC์˜ ์ˆ˜์กฐ์— ์‹œํ—˜์ฒด๋ฅผ ์นจ์ˆ˜์‹œ์ผฐ์œผ๋ฉฐ, ์ดํ›„ ์‹œํ—˜์ฒด๋ฅผ ์žฌ๋ น 28์ผ๊นŒ์ง€ ์˜จ๋„ 23ยฑ2 ยฐC, ์ƒ๋Œ€์Šต๋„ 50ยฑ5 %์˜ ์กฐ๊ฑด์— ๋…ธ์ถœ์‹œ์ผฐ์œผ๋ฉฐ, ๊ธฐ๊ฑด๋ฐ€๋„๋Š” ์‹ (2)์— ๋”ฐ๋ผ ์‚ฐ์ •ํ•˜์˜€๋‹ค.

(2)
$E_{m}=(A\times 997)/(B-C)$

์—ฌ๊ธฐ์„œ, $E_{m}$์€ ๊ธฐ๊ฑด๋ฐ€๋„, $A$๋Š” ๊ฑด์กฐ ํ›„์˜ ์‹œํ—˜์ฒด ์งˆ๋Ÿ‰, $B$๋Š” ํ‘œ๋ฉด๊ฑด์กฐ ํฌํ™”์ƒํƒœ์˜ ์‹œํ—˜์ฒด ์งˆ๋Ÿ‰, $C$๋Š” ์ˆ˜์ค‘์งˆ๋Ÿ‰์„ ์˜๋ฏธํ•œ๋‹ค.

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••์ถ•๊ฐ•๋„ ๋ฐ ํœจ๊ฐ•๋„๋Š” ๊ฐ๊ฐ KS F 2405(KATS 2017) ๋ฐ ASTM C1609 (2020)์— ๋”ฐ๋ผ ์ธก์ •ํ•˜์˜€๋‹ค. ์‹คํ—˜์žฅ๋น„๋กœ๋Š” ์ตœ๋Œ€ 200 t ์šฉ๋Ÿ‰์„ ๊ฐ–๋Š” ๋งŒ๋Šฅ์žฌ๋ฃŒ์‹œํ—˜๊ธฐ๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ์žฌํ•˜์†๋„๋Š” ๊ฐ๊ฐ 0.35 mm/min ๋ฐ 0.20 mm/min์œผ๋กœ ์„ค์ •ํ•˜์˜€๋‹ค. 6๊ฐœ์˜ ์›์ฃผํ˜• ์‹œํ—˜์ฒด(์ง๊ฒฝ 100 mm, ๋†’์ด 200 mm)๋ฅผ ์ œ์ž‘ํ•˜์—ฌ, ์žฌ๋ น 7์ผ์—์„œ 3๊ฐœ, ์žฌ๋ น 28์ผ์—์„œ 3๊ฐœ์˜ ์••์ถ•๊ฐ•๋„๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ํœจ ๊ฐ•๋„ ์‹œํ—˜์ฒด๋Š” ๋‹จ๋ฉด 100ร—100 mm$^{2}$, ๊ธธ์ด 400 mm์˜ ๊ฐ์ฃผํ˜•์œผ๋กœ ์ œ์ž‘ํ•˜์˜€์œผ๋ฉฐ, ํœจ ๊ฐ•๋„๋Š” 28์ผ ์žฌ๋ น์—์„œ ์ธก์ •ํ•˜์˜€๋‹ค.

๋ณธ ์—ฐ๊ตฌ์—์„œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ์  ํŠน์„ฑ์„ ์ „๊ธฐ ๋น„์ €ํ•ญ(electrical resistivity)๊ณผ ์ฐจํ ํšจ๊ณผ๋ฅผ ํ†ตํ•ด ํ‰๊ฐ€ํ•˜์˜€๋‹ค. ์‹œํ—˜์ฒด๋Š” 4๊ฐœ์˜ ๊ตฌ๋ฆฌํŒ(ํญ 20 mm, ๊ธธ์ด 100 mm)์„ 60 mm ๊ฐ„๊ฒฉ์œผ๋กœ ๋งค์ž…ํ•˜์—ฌ 100 mmร—100 mmร—400 mm ํฌ๊ธฐ๋กœ ์ œ์ž‘ํ•˜์˜€๋‹ค(You et al. 2017;Xue et al. 2021). ์ „๊ธฐ์ €ํ•ญ ์ธก์ • ์‹œ 4-probe method๋ฅผ ํ™œ์šฉํ•˜์˜€์œผ๋ฉฐ, ํŽธ๊ทนํšจ๊ณผ(polarization effect)๋ฅผ ์ œ์–ดํ•˜๊ธฐ ์œ„ํ•ด 100 kHz ๋Œ€์—ญ์˜ ๊ต๋ฅ˜์ „๋ฅ˜๋ฅผ ์ ์šฉํ•˜์˜€๋‹ค(Hong et al. 2020b). ๊ณ„ํš๋œ ์žฌ๋ น์—์„œ ์ธก์ •ํ•œ ์ „๊ธฐ์ €ํ•ญ์„ ํ™œ์šฉํ•˜์—ฌ ์‹ (3)๊ณผ ๊ฐ™์ด ์ „๊ธฐ ๋น„์ €ํ•ญ์„ ๊ณ„์‚ฐํ•˜์˜€๋‹ค.

(3)
$\rho =RA/L$

์—ฌ๊ธฐ์„œ, $\rho$๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋น„์ €ํ•ญ, $R$์€ ๊ณ„ํš๋œ ์žฌ๋ น์—์„œ์˜ ์ฝ˜ํฌ๋ฆฌํŠธ ์ „๊ธฐ์ €ํ•ญ, $A$๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ๊ตฌ๋ฆฌํŒ์˜ ์ ‘์ด‰๋ฉด์ , $L$์€ ๊ตฌ๋ฆฌํŒ์˜ ๊ฐ„๊ฒฉ์„ ์˜๋ฏธํ•œ๋‹ค.

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ฐจํ ํšจ๊ณผ๋ฅผ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•ด, ๋‹จ๋ฉด 300ร—300 mm$^{2}$ ๋ฐ ๋‘๊ป˜ 140 mm์˜ ํŒจ๋„์„ ์ œ์ž‘ํ•˜์—ฌ ๋ฒฝ์ฒด๋ฅผ ๋ชจ์‚ฌํ•˜์˜€๋‹ค(Choi et al. 2020). Fig. 3(a)๋Š” ์‹œํ—˜์ฒด์˜ ์ƒ์„ธ์ด๋ฉฐ, ์ง๊ฒฝ 10 mm์˜ ์ฒ ๊ทผ ๋ฐ CFRP ๋ณด๊ฐ•๊ทผ์„ ํ™œ์šฉํ•˜์—ฌ 100 mm ๊ฐ„๊ฒฉ ๋ฐ 2๋‹จ์œผ๋กœ ๋ฐฐ๊ทผํ•˜์˜€๋‹ค. ์‹คํ—˜์€ Fig. 3(b)์™€ ๋™์ผํ•˜๊ฒŒ, ์•ˆํ…Œ๋‚˜์˜ ์ค‘์‹ฌ๊ณผ ์‹œํ—˜์ฒด์˜ ์ค‘์‹ฌ์„ ์ผ์น˜์‹œํ‚จ ํ›„ ์ง„ํ–‰ํ•˜์˜€๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ธก์ • ์ „ ์‹œํ—˜์ฒด๋ฅผ 3์ผ ๋™์•ˆ 60 ยฐC๋กœ ๊ฑด์กฐ์‹œ์ผฐ์œผ๋ฉฐ, ์ดํ›„ 0.4~ 1.4 GHz ๋ฒ”์œ„์— ๋Œ€ํ•ด 0.1 GHz ์ฐจํ ํšจ๊ณผ๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ์ธก์ •๊ฒฐ๊ณผ๋Š” ์†Œํ”„ํŠธ์›จ์–ด์— ์ฐจํ ํšจ๊ณผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ๊ทธ ๊ฐ’์€ ์‹ (4)์— ์˜ํ•ด ๋„์ถœ๋˜์—ˆ๋‹ค.

(4)
$SE = -10\log(P_{t}/P_{i})$

์—ฌ๊ธฐ์„œ, $SE$๋Š” ์ฐจํ ํšจ๊ณผ, $P_{t}$๋Š” ๋งค์งˆ์„ ํ†ต๊ณผํ•œ ์ˆ˜์‹ ์ „๋ ฅ, $P_{i}$๋Š” ๋งค์งˆ์— ์ž…์‚ฌ๋˜๋Š” ์ˆ˜์‹ ์ „๋ ฅ์„ ์˜๋ฏธํ•œ๋‹ค.

Fig. 3 Details for measuring shielding effectiveness of concrete
../../Resources/KCI/JKCI.2022.34.2.153/fig3.png

3. ์‹คํ—˜๊ฒฐ๊ณผ ๋ฐ ๋ถ„์„

3.1 ๋ฐ€๋„ ๋ถ„์„

Fig. 4๋Š” ๋ชจ๋“  ๋ณ€์ˆ˜์˜ ๋ฐ€๋„๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. Plain ๋ณ€์ˆ˜์ธ NA-NN์€ ๊ธฐ๊ฑด๋ฐ€๋„๊ฐ€ 2,197 kg/m$^{3}$์œผ๋กœ ์ธก์ •๋˜์—ˆ์œผ๋ฉฐ, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์„ 15 % ์น˜ํ™˜ํ•˜์—ฌ ํ˜ผ์ž…ํ•  ๊ฒฝ์šฐ, ๊ธฐ๊ฑด๋ฐ€๋„๋Š” 2,323 kg/m$^{3}$์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. LA-ES15๋Š” ๋ณธ ์—ฐ๊ตฌ์—์„œ ๊ฐ€์žฅ ์ž‘์€ ๊ธฐ๊ฑด๋ฐ€๋„ ํŠน์„ฑ์„ ๋ณด์˜€๋‹ค. ์ด๋Š” ๋‹จ์œ„ ๋ฐ”์ธ๋”์˜ ์–‘์ด ์ฆ๊ฐ€ํ•˜๋”๋ผ๋„, ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ๋ณด๋‹ค ๋ฐ€๋„๊ฐ€ ์•ฝ 30 % ๊ฐ์†Œํ•œ ๋ฐ”ํ…€์• ์‹œ๊ณ„ ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋ฅผ ํ™œ์šฉํ•จ์œผ๋กœ์จ, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฒฝ๋Ÿ‰ํ™”๋ฅผ ๊ฐ€๋Šฅํ•˜๊ฒŒ ํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค(Hong et al. 2020a). ํ•œํŽธ, ๊ฐ•์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•œ ๊ฒฝ์šฐ, LA-ES15-SF๋Š” LA-ES15์— ๋น„ํ•ด ์•ฝ 4.4 % ์ฆ๊ฐ€ํ•œ ๊ธฐ๊ฑด๋ฐ€๋„๊ฐ€ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํŠนํžˆ, LA-ES15-SF๋Š” ์„ฌ์œ ์˜ ํ˜ผ์ž…์œผ๋กœ ๋ฐ€๋„๊ฐ€ ์ฆ๊ฐ€ํ•˜์˜€์Œ์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  Plain ๋ณ€์ˆ˜์ธ NA-NN๋ณด๋‹ค ์•ฝ 3.6 % ๊ฐ์†Œํ•œ 2,119 kg/m$^{3}$ ๊ฐ’์ด ๋‚˜ํƒ€๋‚ฌ๋‹ค.

Fig. 4 Test results of concrete density
../../Resources/KCI/JKCI.2022.34.2.153/fig4.png

์ ˆ๊ฑด๋ฐ€๋„๋Š” ๊ธฐ๊ฑด๋ฐ€๋„์™€ ๊ฒฝํ–ฅ์ด ์œ ์‚ฌํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚ฌ์ง€๋งŒ, ๋ชจ๋“  ๋ณ€์ˆ˜์˜ ์ ˆ๊ฑด๋ฐ€๋„ ์ˆ˜์น˜๋Š” ๊ธฐ๊ฑด๋ฐ€๋„์— ๋น„ํ•ด ๋‚ฎ๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค. NA-NN, NA-ES15์˜ ์ ˆ๊ฑด๋ฐ€๋„๋Š” ๊ธฐ๊ฑด๋ฐ€๋„์— ๋น„ํ•ด ๊ฐ๊ฐ 93 kg/m$^{3}$, 90 kg/m$^{3}$ ๊ฐ์†Œํ•˜์˜€๋‹ค. ๋˜ํ•œ, ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๊ฐ€ ํ˜ผ์ž…๋œ LA-ES15์™€ LA-ES15-SF๋Š” ๊ฐ๊ฐ 62 kg/m$^{3}$, 84 kg/m$^{3}$ ๊ฐ์†Œํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํ•œํŽธ, ACI 318-19 (2019)์—์„œ๋Š” ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ธฐ๊ฑด๋ฐ€๋„๋ฅผ 2,160 kg/m$^{3}$ ์ดํ•˜๋กœ ์ œํ•œํ•˜๊ณ  ์žˆ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ LA-ES15 ๋ฐ LA-ES15-SF์˜ ๊ธฐ๊ฑด๋ฐ€๋„๋Š” ๊ฐ๊ฐ 2,029 kg/m$^{3}$, 2,119 kg/m$^{3}$๋กœ ์ธก์ •๋˜๋ฉฐ, ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์— ์†ํ•œ๋‹ค.

3.2 ๊ฐ•๋„ ๋ถ„์„

Fig. 5๋Š” ๋ฐฐํ•ฉ ๋ณ€์ˆ˜์— ๋Œ€ํ•œ ์••์ถ•๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ์ด๋‹ค. ์ดˆ๊ธฐ ์žฌ๋ น์—์„œ, NA-NN์€ ์•ฝ 56 MPa์˜ ์••์ถ•๊ฐ•๋„๋ฅผ ๋ฐœํ˜„ํ•˜์˜€๋‹ค. ํ•˜์ง€๋งŒ ์‹œ๋ฉ˜ํŠธ์˜ ์ผ๋ถ€๋ฅผ ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง๋กœ ์น˜ํ™˜ํ•  ๋•Œ, ๊ฐ•๋„์˜ ์ €ํ•˜๊ฐ€ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, NA-ES15๋Š” NA-NN์— ๋น„ํ•ด ์•ฝ 8.6 % ๊ฐ์†Œํ•œ ๊ฐ’์ด ์ธก์ •๋˜์—ˆ๋‹ค. ์ด๋Š” ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์˜ ๋‚ฎ์€ ์ˆ˜๊ฒฝ์„ฑ(hydraulicity)์— ๊ธฐ์ธํ•œ๋‹ค(Hong et al. 2019;Lee et al. 2019). ์‹ค์ œ๋กœ ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์„ ์น˜ํ™˜ํ•˜์—ฌ ํ˜ผ์ž…ํ•œ ๊ฒฝ์šฐ, ์‹œ๋ฉ˜ํŠธ์˜ ์‚ฌ์šฉ๋Ÿ‰์ด ๊ฐ์†Œํ•˜๊ฒŒ ๋˜๋Š”๋ฐ, ์ด๋Š” ์ˆ˜ํ™”๋ฐ˜์‘์˜ ์ง€์—ฐ์„ ์œ ๋ฐœํ•˜์—ฌ Ca(OH)2์˜ ์ƒ์„ฑ์„ ์ œํ•œํ•œ๋‹ค(Roslan et al. 2016). ์ด์™€ ๊ด€๋ จํ•˜์—ฌ, ๋‹ค์ˆ˜์˜ ์—ฐ๊ตฌ์ž๋“ค์€(Hong et al. 2019, 2021;Lee et al. 2019)์€ XRD, MIP ๋ถ„์„ ๋ฐ ๊ด€์ž…์ €ํ•ญ ์‹œํ—˜์„ ํ†ตํ•ด, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์˜ ํ˜ผ์ž…์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ˆ˜ํ™”๋ฐ˜์‘์„ ์ง€์—ฐ์‹œํ‚ค๋Š” ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ํ•˜์˜€๋‹ค. ์ด๋Ÿฌํ•œ ์˜ํ–ฅ์œผ๋กœ ์ธํ•ด 28์ผ ์žฌ๋ น์—์„œ NA-ES15๋Š” NA-NN์— ๋น„ํ•ด ์••์ถ•๊ฐ•๋„๊ฐ€ ์•ฝ 6.5 % ๊ฐ์†Œํ•˜์˜€๋‹ค. ํ•œํŽธ, ๋‹ค์ˆ˜์˜ ์—ฐ๊ตฌ์ž๋Š” ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์˜ ํ˜ผ์ž…๋ฅ ์„ 15 % ์ด๋‚ด๋กœ ์„ค์ •ํ•  ๋•Œ ๊ฐ•๋„ ์ €ํ•˜๊ฐ€ ํฌ๊ฒŒ ๋ฐœ์ƒํ•˜์ง€ ์•Š๋Š” ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ํ•˜๊ณ  ์žˆ๋Š”๋ฐ, ์žฅ๊ธฐ ์žฌ๋ น์— ๋„๋‹ฌํ• ์ˆ˜๋ก NA-ES15๋Š” NA-NN๊ณผ ์œ ์‚ฌํ•œ ์••์ถ•๊ฐ•๋„๋ฅผ ๋ฐœํ˜„ํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค(Hong et al. 2019;Lee et al. 2019). ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฒฝ๋Ÿ‰ํ™”๋ฅผ ์œ„ํ•ด ๊ณ ๋ คํ•œ ๋ณ€์ˆ˜์ธ LA-ES15์˜ ๊ฒฝ์šฐ, ๋‚ฎ์€ w/b์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  ๋ณธ ์—ฐ๊ตฌ์—์„œ ํ™œ์šฉํ•œ ๋ชจ๋“  ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐฐํ•ฉ ๋ณ€์ˆ˜์—์„œ ๊ฐ€์žฅ ๋‚ฎ์€ ์••์ถ•๊ฐ•๋„๊ฐ€ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋Š” ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๊ฐ€ ์ผ๋ฐ˜๊ณจ์žฌ์— ๋น„ํ•ด ๋ฐ€๋„๊ฐ€ ์ž‘๊ณ , ๋‹ค๋Ÿ‰์˜ ๊ณต๊ทน์„ ํ•จ์œ ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ๊ฐ•๋„์— ๋Œ€ํ•œ ์ €ํ•ญ์„ฑ์ด ๋‚ฎ๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค(Wongsa et al. 2016;Kim et al. 2020). Hong et al.(2020a)์— ์˜ํ•˜๋ฉด, ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ๋ฅผ ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋กœ 100 % ์น˜ํ™˜ํ•  ๋•Œ ์•ฝ 7 % ์ด์ƒ์˜ ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„๊ฐ€ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ๋˜์—ˆ์œผ๋ฉฐ, Kim et al.(2020)์˜ ์—ฐ๊ตฌ์—์„œ๋Š” ์•ฝ 21 % ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํ•œํŽธ, ๊ฐ•์„ฌ์œ ์˜ ํ˜ผ์ž…์€ ์••์ถ•๊ฐ•๋„์— ๊ธ์ •์ ์ธ ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. 28์ผ ์žฌ๋ น์—์„œ, LA-ES15-SF์˜ ์••์ถ•๊ฐ•๋„๋Š” LA-ES15์— ๋น„ํ•ด ์•ฝ 5.5 % ์ฆ๊ฐ€ํ•œ ์ˆ˜์น˜๊ฐ€ ์ธก์ •๋˜์—ˆ์œผ๋ฉฐ, LA-ES15-SF๋Š” NA-ES15์™€ ์œ ์‚ฌํ•œ ์••์ถ•๊ฐ•๋„ ํŠน์„ฑ์ด ๋‚˜ํƒ€๋‚ฌ๋‹ค.

Fig. 5 Test results of compressive strength at different ages
../../Resources/KCI/JKCI.2022.34.2.153/fig5.png

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํœจ ๊ฑฐ๋™ ํŠน์„ฑ ๊ฒฐ๊ณผ๋Š” Fig. 6 ๋ฐ Table 4์— ๋‚˜ํƒ€๋‚˜ ์žˆ๋‹ค. ์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋˜์ง€ ์•Š์€ ์‹œํ—˜์ฒด(NA-NN, NA-ES15, LA-ES15)๋Š” ํ•˜์ค‘์˜ ์ฆ๊ฐ€์— ๋”ฐ๋ผ ์ฒ˜์ง์ด ์ฆ๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ์ทจ์„ฑ ํŒŒ๊ดด๋ฅผ ๋ณด์˜€๋‹ค. NA-NN๊ณผ NA-ES15๋Š” ์ฒ˜์ง์ด 0.050 mm ์ด์ƒ ๋ฐœ์ƒํ•œ ๋ฐ˜๋ฉด์—, LA-ES15๋Š” ์ฒ˜์ง์ด ์•ฝ 0.032 mm์— ๋„๋‹ฌํ•˜์ž๋งˆ์ž ์‹œํ—˜์ฒด์˜ ํŒŒ๊ดด๊ฐ€ ๋‚˜ํƒ€๋‚ฌ๋‹ค. LA-ES15๋Š” NA-NN๊ณผ NA- ES15์— ๋น„ํ•ด w/b๊ฐ€ ๋งค์šฐ ๋‚ฎ์Œ์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  ๊ฒฝ๋Ÿ‰๊ณจ์žฌ์˜ ์ทจ์•ฝํ•œ ํ•˜์ค‘ ์ €ํ•ญ ํŠน์„ฑ์— ์˜ํ•ด ํœจ ์„ฑ๋Šฅ์ด ์ €ํ•˜๋œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ผ๋ฐ˜๊ณจ์žฌ์™€ ๋‹ฌ๋ฆฌ, ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋Š” ์™ธ๋ ฅ์— ์˜ํ•œ ๊ท ์—ด์ด ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ๋‚ด๋ถ€๋ฅผ ๊ด€ํ†ตํ•˜๋ฉฐ, ์ด๋กœ ์ธํ•ด LA-ES15๋Š” NA-ES15์— ๋น„ํ•ด ์ฒ˜์ง๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ์ตœ๋Œ€ ํ•˜์ค‘๋„ ๊ฐ์†Œํ•˜์˜€๋‹ค(Kim and Lee 2011). ํ•œํŽธ, ๊ฐ•์„ฌ์œ ๊ฐ€ ๋ณด๊ฐ•๋œ LA-ES15-SF๋Š” ์ตœ๋Œ€ ํ•˜์ค‘์— ๋„๋‹ฌํ•œ ์ดํ›„์—๋„ ์ทจ์„ฑํŒŒ๊ดด๊ฐ€ ๋ฐœ์ƒํ•˜์ง€ ์•Š์•˜๋‹ค. ์ฆ‰, LA-ES15- SF๋Š” ์ฒซ ํ”ผํฌ(peak) ํ•˜์ค‘๊นŒ์ง€ ํ•˜์ค‘์ด ์ผ์ •ํ•˜๊ฒŒ ์ฆ๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ์ฒซ ํ”ผํฌ ํ•˜์ค‘ ์ดํ›„์—๋Š” ๊ฒฝํ™”(hardening) ๊ฑฐ๋™์„ ๋ณด์˜€๋‹ค. Hardening ๊ฑฐ๋™์€ ๋‘ ๋ฒˆ์งธ ํ”ผํฌ ํ•˜์ค‘์— ๋„๋‹ฌํ•  ๋•Œ๊นŒ์ง€ ์ง€์†๋˜์—ˆ์œผ๋ฉฐ, ์ตœ๋Œ€ ํ•˜์ค‘ ์ดํ›„์—๋Š” ์—ฐํ™”(softening) ๊ฑฐ๋™์„ ๋ณด์ด๋ฉฐ ์—ฐ์„ฑ์ ์ธ ๊ฑฐ๋™์ด ๋‚˜ํƒ€๋‚ฌ๋‹ค. Table 4๋ฅผ ํ†ตํ•ด, ๊ฐ•์„ฌ์œ ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ตœ๋Œ€ ํ•˜์ค‘๊ณผ ์—ฐ์„ฑ์„ ๋ชจ๋‘ ๊ฐœ์„ ์‹œ์ผฐ์Œ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. ํ•œํŽธ, C1609 (2020)์€ ์—๋„ˆ์ง€ ํก์ˆ˜ ๋Šฅ๋ ฅ(energy absorption capacity)์„ ํ†ตํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ธ์„ฑ์„ ํ‰๊ฐ€ํ•˜๋Š” ๋ฐฉ๋ฒ•์„ ์ œ์•ˆํ•˜๋Š”๋ฐ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ง€๊ฐ„ ๊ธธ์ด(span length, L)๋ฅผ 300 mm๋กœ ์„ค์ •ํ•˜์—ฌ ๊ฐ•์„ฌ์œ  ๋ณด๊ฐ• ์ฝ˜ํฌ๋ฆฌํŠธ(steel fiber reinforced concrete, SFRC)์˜ ์ธ์„ฑ์„ ์‚ฐ์ถœํ•˜์˜€๋‹ค. ์‹ (5)๋Š” ์ธ์„ฑ์˜ ๊ณ„์‚ฐ์‹์ด๋ฉฐ, L/150์—์„œ์˜ LA-ES15-SF์˜ ์ธ์„ฑ์€ ์•ฝ 96.5 %๋กœ ๋„์ถœ๋˜์—ˆ๋‹ค.

(5)
$R_{150}^{D}=\dfrac{150T_{150}^{D}}{f_{1}bh^{2}}\times 100%$

์—ฌ๊ธฐ์„œ, $T_{150}^{D}$๋Š” L/150๊นŒ์ง€ ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์˜ ๋ฉด์ , $f_{1}$์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํœจ๊ฐ•๋„๋ฅผ ์˜๋ฏธํ•˜๋ฉฐ, $b$, $h$๋Š” ๊ฐ๊ฐ ์‹œํ—˜์ฒด์˜ ํญ ๋ฐ ๋†’์ด๋ฅผ ์˜๋ฏธํ•œ๋‹ค.

Fig. 6 Load-deflection curve of concrete
../../Resources/KCI/JKCI.2022.34.2.153/fig6.png
Table 4 Flexure test results of concrete

Max. load

(kN)

Deflection at max. load

(mm)

Flexural strength

(MPa)

Toughness ratio at L/150 (%)

NA-NN

23.32

0.054

7.0

-

NA-ES15

21.32

0.052

6.4

-

LA-ES15

16.66

0.032

5.0

-

LA-ES15-SF

26.66

0.354

8.0

96.5

3.3 ์ „๊ธฐ ๋น„์ €ํ•ญ ๋ถ„์„

Fig. 7์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ ๋น„์ €ํ•ญ ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ๋ชจ๋“  ์ฝ˜ํฌ๋ฆฌํŠธ ์‹œํ—˜์ฒด๋Š” ์žฌ๋ น์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์ „๊ธฐ ๋น„์ €ํ•ญ์ด ์ฆ๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ์žฌ๋ น์ด ๊ธธ์–ด์งˆ์ˆ˜๋ก ์ฆ๊ฐ€ํญ์ด ๋”์šฑ ์ƒ์Šนํ•˜์˜€๋‹ค. ์ด๋Ÿฌํ•œ ํ˜„์ƒ์€ Plain ๋ณ€์ˆ˜์ธ NA-NN์—์„œ ๊ฐ€์žฅ ๋‘๋“œ๋Ÿฌ์ง€๊ฒŒ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์ด๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด ๊ณต๊ทน์ˆ˜๊ฐ€ ์žฌ๋ น์ด ์ฆ๊ฐ€ํ•จ์— ์†Œ๋ชจ๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค(Hong et al. 2020b). ํ•œํŽธ ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์ด 15 % ์น˜ํ™˜๋˜์—ˆ์„ ๋•Œ, ์ „๊ธฐ ๋น„์ €ํ•ญ์ด ๊ฐ์†Œํ•˜์˜€๋‹ค. ์ผ๋ฐ˜์ ์œผ๋กœ ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ๋Š” ๊ณ ๊ฐ•๋„ ์ฒ ๊ทผ์˜ ์ œ์กฐ ์‹œ ๋ฐœ์ƒํ•˜๋Š” ์‚ฐ์—…๋ถ€์‚ฐ๋ฌผ๋กœ, ์ฒ  ์„ฑ๋ถ„, ํŠนํžˆ Fe2O3๋ฅผ ๋‹ค๋Ÿ‰ ํ•จ์œ ํ•˜๊ณ  ์žˆ๋‹ค. ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋‚ด Fe2O3๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ ์ „๋„์„ฑ์„ ํ–ฅ์ƒ์‹œํ‚ฌ ์ˆ˜ ์žˆ์œผ๋ฉฐ, ๋‹ค์ˆ˜์˜ ์—ฐ๊ตฌ์ž๋Š” ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ํ˜ผ์ž…์— ๋”ฐ๋ฅธ ์ „๊ธฐ์  ํŠน์„ฑ์˜ ๋ณ€ํ™”๋ฅผ ๋ณด๊ณ ํ•˜์˜€๋‹ค(Baeza et al. 2018;Hong et al. 2020b). ์ด๋ฅผ ํ†ตํ•ด, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ๋Š” ์ „๋„์„ฑ ์žฌ๋ฃŒ๋กœ์„œ ์ฝ˜ํฌ๋ฆฌํŠธ ๋งคํŠธ๋ฆญ์Šค ๋‚ด์— ์ž˜ ๋ถ„ํฌ๋˜์–ด ์ „๋„์„ฑ ๊ฒฝ๋กœ๋ฅผ ํ˜•์„ฑํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด์— ๋”ฐ๋ผ, 28์ผ ์žฌ๋ น์—์„œ NA-ES15๋Š” NA-NN์— ๋น„ํ•ด ์ „๊ธฐ ๋น„์ €ํ•ญ์ด ์•ฝ 22.38 % ๊ฐ์†Œํ•˜์˜€๋‹ค.

๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ ์—ญ์‹œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ์  ํŠน์„ฑ์„ ๊ฐœ์„  ์‹œํ‚ค๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. LA-ES15์˜ ๊ฒฝ์šฐ, 7์ผ ์žฌ๋ น ๋ฐ 14์ผ ์žฌ๋ น์—์„œ์˜ ์ „๊ธฐ ๋น„์ €ํ•ญ์€ ์œ ์‚ฌํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์žฌ๋ น์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ๋น„์ €ํ•ญ์˜ ์ฐจ์ด๊ฐ€ ๋”์šฑ ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ์ด๋Š” ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ์™€ ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ์˜ ํ™”ํ•™ ๊ตฌ์„ฑ์„ฑ๋ถ„์˜ ํ•จ์œ ๋Ÿ‰ ์ฐจ์ด๊ฐ€ ์›์ธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ ์‚ฌ์šฉํ•œ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋Š” ๋ฐ”ํ…€์• ์‹œ๊ณ„๋กœ์„œ, ์‹ค๋ฆฌ์นด(silica), ์•Œ๋ฃจ๋ฏธ๋‚˜(alumina), ์ฒ ์„ ์ฃผ์š” ์„ฑ๋ถ„์œผ๋กœ ๊ฐ€์ง„๋‹ค(Ankur and Singh 2021). Table 2์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด, ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๊ฐ€ ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ์— ๋น„ํ•ด Fe2O3๋ฅผ ์•ฝ 5.1 % ๋” ํ•จ์œ ํ•˜๊ณ  ์žˆ๊ธฐ ๋•Œ๋ฌธ์— ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋Š” ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ๋ณด๋‹ค ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋”์šฑ ์šฐ์ˆ˜ํ•œ ์ „๊ธฐ์  ํŠน์„ฑ์„ ๋ถ€์—ฌํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๊ฐ•์„ฌ์œ ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ ์ „๋„์„ฑ์„ ํ–ฅ์ƒ์‹œํ‚ค๋Š” ์žฌ๋ฃŒ๋กœ ์ž˜ ์•Œ๋ ค์ ธ ์žˆ๋‹ค. ๊ฐ•์„ฌ์œ ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด์—์„œ ์„œ๋กœ ๊ต์ฐจ๋˜๋ฉฐ ํšจ๊ณผ์ ์ธ ์ „๋„์„ฑ ๊ฒฝ๋กœ๋ฅผ ํ˜•์„ฑํ•œ๋‹ค(Zhang and Sun 2012). LA- ES15์— 0.75 %์˜ ๊ฐ•์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•  ๊ฒฝ์šฐ, ์ „๊ธฐ ๋น„์ €ํ•ญ์˜ ๊ธ‰๊ฒฉํ•˜๊ฒŒ ๊ฐ์†Œํ•˜์˜€๋‹ค. ๋ชจ๋“  ์žฌ๋ น์—์„œ, ์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๋“ค์€ ์ „๊ธฐ ๋น„์ €ํ•ญ์ด ๋ชจ๋‘ ์•ฝ 12.6~29.0 ฮฉ๏ฝฅm์— ๋ถ„ํฌํ•œ ๋ฐ˜๋ฉด์—, ์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋œ LA-ES15-SF ๋ชจ๋‘ ์•ฝ 1.6~2.1 ฮฉ๏ฝฅm ์‚ฌ์ด์— ๋ถ„ํฌํ•˜์˜€๋‹ค.

Fig. 7 Test results of electrical resistivity at different ages
../../Resources/KCI/JKCI.2022.34.2.153/fig7.png

3.4 ์ฐจํ ํšจ๊ณผ ๋ถ„์„

Fig. 8์€ 0.4~1.4 GHz ๊ตฌ๊ฐ„์— ๋Œ€ํ•˜์—ฌ ์ฃผํŒŒ์ˆ˜์— ๋Œ€ํ•œ ์ฐจํ ํšจ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ๋จผ์ €, ์ฒ ๊ทผ์„ 100 mm ๊ฐ„๊ฒฉ์œผ๋กœ ๋ฐฐ๊ทผํ•œ ์‹œํ—˜์ฒด(-S series)์— ๋Œ€ํ•œ ๊ฒฐ๊ณผ๋ฅผ ์‚ดํŽด๋ณด๋ฉด, ์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋˜์ง€ ์•Š์€ ์‹œํ—˜์ฒด๋Š” ๋ชจ๋‘ ์œ ์‚ฌํ•œ ์ฐจํ ํšจ๊ณผ๋ฅผ ๋ณด์˜€๋‹ค. NA-NN, NA-ES15, LA-ES15๋Š” ๋ชจ๋‘ ์ฐจํ ํšจ๊ณผ๊ฐ€ ์•ฝ 4~17 dB ์‚ฌ์ด์— ๋ถ„ํฌํ•˜์˜€๋‹ค. NA-ES15๋Š” NA-NN์— ๋น„ํ•ด ์ฐจํ ํšจ๊ณผ๊ฐ€ ํ‰๊ท ์ ์œผ๋กœ ์•ฝ 0.9 dB ํ–ฅ์ƒ๋˜์—ˆ๋‹ค. ์ธก์ •๊ฒฐ๊ณผ๋ฅผ ํ†ตํ•ด, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋ฏธ๋ถ„๋ง์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ฐจํ ํšจ๊ณผ๋ฅผ ๋ฏธ์„ธํ•˜๊ฒŒ ๊ฐœ์„ ์‹œํ‚ค๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์ด๋Š” ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ ๋‚ด ๊ธˆ์† ์„ฑ๋ถ„, ์ฆ‰ Fe2O3์™€ Al2O3์— ์˜ํ•œ ์˜ํ–ฅ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค(Wanasinghe et al. 2020). Wanasinghe et al. (2020)์€ ๊ธˆ์† ์„ฑ๋ถ„์ด ์ „์žํŒŒ์˜ ์†์‹ค์„ ์œ ๋ฐœํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ํ•˜์˜€์œผ๋ฉฐ, Wanasinghe et al. (2020)์˜ ์—ฐ๊ตฌ์—์„œ๋Š” Fe2O3๊ฐ€ ์ „์žํŒŒ๋ฅผ ํก์ˆ˜ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํ•˜์ง€๋งŒ, ์ œ๊ฐ•์Šฌ๋ž˜๊ทธ๋Š” ์ „์žํŒŒ ์ฐจํ ์„ฑ๋Šฅ์„ ํ–ฅ์ƒํ•˜๋Š”๋ฐ ํšจ๊ณผ์ ์ด์ง€ ์•Š์€ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 8 Test results of shielding effectiveness of concrete
../../Resources/KCI/JKCI.2022.34.2.153/fig8.png

๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ์˜ ํ˜ผ์ž…์„ ํ†ตํ•ด, LA-ES15๋Š” NA-ES15์— ๋น„ํ•ด ์ฐจํ ํšจ๊ณผ๊ฐ€ ํ‰๊ท ์ ์œผ๋กœ ์•ฝ 1.7 dB ํ–ฅ์ƒ๋˜์—ˆ์œผ๋ฉฐ, 1.0 GHz์—์„œ ์ตœ๋Œ€ 4.5 dB ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋„ Fe2O3๋ฐ Al2O3์— ์˜ํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ฐจํ ํšจ๊ณผ๋ฅผ ๋ฏธ์„ธํ•˜๊ฒŒ ๊ฐœ์„ ์‹œํ‚ค๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. Ozturk et al. (2018)์€ ๊ธˆ์† ์„ฑ๋ถ„์ด ์ „์žํŒŒ์˜ ์ „ํŒŒ๋ฅผ ๋ง‰๋Š” ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ํ•˜์˜€์œผ๋ฉฐ, Table 2์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด, ๋ณธ ์—ฐ๊ตฌ์—์„œ ์‚ฌ์šฉํ•œ ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋Š” ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ์™€ ์œ ์‚ฌํ•œ Al2O3 ํ•จ๋Ÿ‰ ๋ฐ 1.12๋ฐฐ ๋” ๋งŽ์€ Fe2O3๋ฅผ ํ•จ์œ ํ•˜๊ณ  ์žˆ๋‹ค. ๋˜ํ•œ, ๊ฒฝ๋Ÿ‰๊ณจ์žฌ์˜ ๊ณต๊ทน ํŠน์„ฑ๋„ ์ฐจํ ํšจ๊ณผ ๊ฐœ์„ ์— ์˜ํ–ฅ์„ ๋ฏธ์นœ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋Š” ๋‚ด๋ถ€์— ๊ณต๊ทน์ด ๋‹ค๋Ÿ‰์œผ๋กœ ๋ถ„ํฌํ•˜์—ฌ ์ „์žํŒŒ๋ฅผ ํก์ˆ˜ํ•˜๋Š” ์„ฑ์งˆ์ด ์ผ๋ฐ˜๊ณจ์žฌ๋ณด๋‹ค ์šฐ์ˆ˜ํ•˜๋ฉฐ, ์ด๋Ÿฌํ•œ ํŠน์„ฑ์ด LA-ES15์˜ ์ฐจํ ํšจ๊ณผ๋ฅผ ํ–ฅ์ƒ์‹œํ‚จ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค(Baoyi et al. 2011).

๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ ๊ฐ•์„ฌ์œ ๋กœ ๋ณด๊ฐ•๋  ๊ฒฝ์šฐ, ๋ชจ๋“  ์ฃผํŒŒ์ˆ˜ ๋ฒ”์œ„์— ๋Œ€ํ•ด ์ตœ์†Œ 23 dB ์ด์ƒ์”ฉ ์ฐจํ ํšจ๊ณผ๊ฐ€ ํ–ฅ์ƒ๋˜์—ˆ๋‹ค. LA-ES15-SF๋Š” LA-ES15์— ๋น„ํ•ด ์ฐจํ ํšจ๊ณผ๊ฐ€ ํ‰๊ท ์ ์œผ๋กœ ์•ฝ 38.5 dB ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ๊ฐ•์„ฌ์œ ๋Š” ๊ธˆ์†์„ฑ์„ ๋ ๋Š” ์žฌ๋ฃŒ๋กœ์„œ, ์ „์ž๋ถ„๊ทน(electronic polarization) ๋ฐ ์ด์˜จ๋ถ„๊ทน(ionic polarization)์„ ์œ ๋ฐœํ•˜์—ฌ ์ „์žํŒŒ๋ฅผ ๊ฐ์‡ ํ•˜๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค(Fan et al. 2017). ์ฆ‰, ๊ฐ•์„ฌ์œ ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด์—์„œ ์„œ๋กœ ๊ต์ฐจํ•˜์—ฌ ์ „๊ธฐ ์ „๋„์„ฑ์„ ํ–ฅ์ƒ์‹œํ‚ด๊ณผ ๋™์‹œ์— ์ „์žํŒŒ์˜ ํก์ˆ˜๋ฅผ ์ฆ๊ฐ€์‹œํ‚ค๋ฉฐ, ์ด๋Ÿฌํ•œ ํŠน์„ฑ์œผ๋กœ ์ธํ•ด, ๊ฐ•์„ฌ์œ ๋Š” ๊ธˆ์†์„ฑ ํก์ˆ˜์žฌ(metallic absorbent)๋กœ์„œ ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด์— ๊ฐ€์žฅ ๋งŽ์ด ํ™œ์šฉ๋˜๊ณ  ์žˆ๋‹ค(Zhang and Sun 2012;Fan et al. 2017). LA-ES15-SF๋Š” 1.2 GHz์—์„œ ์ตœ๋Œ€ 59.8 dB์˜ ์ฐจํ ํšจ๊ณผ๊ฐ€ ์ธก์ •๋˜๋ฉฐ ์šฐ์ˆ˜ํ•œ ์ „์žํŒŒ ์ฐจํ ๊ฑฐ๋™์„ ๋ณด์˜€๋‹ค.

ํ•œํŽธ, CFRP ๋ณด๊ฐ•๊ทผ์€ ์ „๊ธฐ ์ „๋„์„ฑ์„ ๋„๋ฉฐ ์ฒ ๊ทผ๊ณผ ์œ ์‚ฌํ•œ ์ „์žํŒŒ ์ฐจํ ๊ฑฐ๋™์„ ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ผ๋ฐ˜์ ์œผ๋กœ FRP ๋ณด๊ฐ•๊ทผ์€ ๋น„์ „๋„์„ฑ์ด์ง€๋งŒ, CFRP ๋ณด๊ฐ•๊ทผ์€ ํƒ„์†Œ์„ฌ์œ ๊ฐ€ ํฌํ•จ๋˜์–ด ์ „๋„์„ฑ์ด ์ฆ๊ฐ€ํ•˜์—ฌ ์ฒ ๊ทผ๊ณผ ์œ ์‚ฌํ•œ ๊ฑฐ๋™์„ ํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์‹ค์ œ๋กœ, Yoo et al. (2020)์€ ํƒ„์†Œ์„ฌ์œ  ํ˜ผ์ž…์— ์˜ํ•ด ์ „๊ธฐ ์ „๋„์„ฑ ๋ฐ ์ฐจํ ํšจ๊ณผ๊ฐ€ ํ–ฅ์ƒ๋œ๋‹ค ๋ณด๊ณ ํ•˜์˜€๋‹ค. ์ด์— ๋”ฐ๋ผ NA-NN, NA-ES15 ๋ฐ LA-ES15๋ฅผ CFRP ๋ณด๊ฐ•๊ทผ์œผ๋กœ ๋ณด๊ฐ•ํ•œ ์‹œํ—˜์ฒด(-C series)๋Š” -S series์™€ ์œ ์‚ฌํ•œ ์ฐจํ ํšจ๊ณผ๊ฐ€ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋ฅผ ํ†ตํ•ด, ๊ธฐ์กด์˜ ์ฒ ๊ทผ์„ CFRP ๋ณด๊ฐ•๊ทผ์œผ๋กœ ๋Œ€์ฒดํ•  ๊ฒฝ์šฐ, ์œ ์‚ฌํ•œ ์ฐจํ ํšจ๊ณผ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ๊ตฌ์กฐ๋ฌผ์˜ ์ค‘๋Ÿ‰์„ ๊ฐ์†Œ์‹œํ‚ฌ ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

4. ๊ฒฐ ๋ก 

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋ฐ”ํ…€์• ์‹œ๊ณ„ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ๋ฅผ ์ฝ˜ํฌ๋ฆฌํŠธ์— ํ˜ผ์ž…ํ•˜์—ฌ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ธฐ๊ณ„์  ๋ฐ ์ „๊ธฐ์  ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜์˜€๋‹ค. ๋ณธ ์—ฐ๊ตฌ์˜ ๋ฒ”์œ„ ๋‚ด์—์„œ ์–ป์€ ๊ฒฐ๋ก ์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

1) ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ์˜ ์น˜ํ™˜์„ ํ†ตํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฒฝ๋Ÿ‰ํ™”๋ฅผ ๋‹ฌ์„ฑํ•˜์˜€์œผ๋ฉฐ, LA-ES15-SF๋Š” ๊ฐ•์„ฌ์œ ์˜ ํ˜ผ์ž…์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  ๊ธฐ๊ฑด๋ฐ€๋„๊ฐ€ 2,119 kg/m$^{3}$๋กœ ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์— ์†ํ•˜์˜€๋‹ค.

2) ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋Š” ๊ณต๊ทน ํŠน์„ฑ์œผ๋กœ ์ธํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ•˜์ค‘์ €ํ•ญ์„ฑ๋Šฅ์„ ๊ฐ์†Œ์‹œ์ผฐ์ง€๋งŒ, LA-ES15-SF์—์„œ๋Š” ๊ฐ•์„ฌ์œ ์˜ ํ˜ผ์ž…์— ์˜ํ•ด ์ตœ๋Œ€ํ•˜์ค‘ ๋ฐ ์—ฐ์„ฑ์ด ๊ฐœ์„ ๋˜์—ˆ๋‹ค.

3) ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ๋Š” ์ผ๋ฐ˜๊ตต์€๊ณจ์žฌ์— ๋น„ํ•ด Fe2O3๋ฅผ ๋” ๋งŽ์ด ํ•จ์œ ํ•˜์—ฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๊ธฐ ์ „๋„์„ฑ์„ ํ–ฅ์ƒ์‹œ์ผฐ์œผ๋ฉฐ, ๊ฐ•์„ฌ์œ  ๋˜ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด ์ „๋„์„ฑ ๊ฒฝ๋กœ๋ฅผ ํ˜•์„ฑํ•˜์—ฌ ์ „๊ธฐ ๋น„์ €ํ•ญ์„ ๊ธ‰๊ฒฉํ•˜๊ฒŒ ๊ฐ์†Œ์‹œ์ผฐ๋‹ค.

4) ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ ๋‚ด ๊ธˆ์† ์„ฑ๋ถ„ ๋ฐ ๊ณต๊ทน ํŠน์„ฑ์€ ์ „์žํŒŒ์˜ ๊ฐ์‡ ๋ฅผ ์œ ๋„ํ•˜์˜€์œผ๋ฉฐ, LA-ES15-SF๋Š” ์ฐจํ ํšจ๊ณผ๊ฐ€ ์ตœ์†Œ 23 dB ํ–ฅ์ƒ๋˜์—ˆ๋‹ค.

์ด์ƒ์„ ์ข…ํ•ฉํ•˜์—ฌ ๋ณผ ๋•Œ, ๋ฐ”ํ…€์• ์‹œ๊ณ„ ๊ฒฝ๋Ÿ‰๊ตต์€๊ณจ์žฌ์™€ ๊ฐ•์„ฌ์œ ๋ฅผ ํ•จ๊ป˜ ํ˜ผ์ž…ํ•  ๊ฒฝ์šฐ, ๊ฒฝ๋Ÿ‰๊ณจ์žฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ธฐ์ค€์„ ๋งŒ์กฑํ•  ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ, ๊ฐ•๋„, ์ „๋„์„ฑ ๋ฐ ์ฐจํ ํšจ๊ณผ์˜ ํ–ฅ์ƒ์ด ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ถ”๊ฐ€๋กœ, CFRP ๋ณด๊ฐ•๊ทผ์„ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋ฐฐ๊ทผํ•  ๊ฒฝ์šฐ, ์ฒ ๊ทผ๊ณผ ์œ ์‚ฌํ•œ ์ „์žํŒŒ ์ฐจํ ๊ฑฐ๋™์„ ํ•˜์˜€๋‹ค. ์ด๋ฅผ ๊ธฐ๋ฐ˜์œผ๋กœ CFRP ๋ณด๊ฐ•๊ทผ์„ ์ฒ ๊ทผ๋Œ€์ฒด์žฌ๋กœ ํ™œ์šฉํ•  ๊ฒฝ์šฐ ์ „์žํŒŒ ์ฐจํ ํšจ๊ณผ ๋ฐ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ตฌ์กฐ๋ฌผ์˜ ๊ฒฝ๋Ÿ‰ํ™”๋ฅผ ๊ธฐ๋Œ€ํ•  ์ˆ˜ ์žˆ์ง€๋งŒ, ์‹ค์ ์šฉ์„ ์œ„ํ•ด์„œ๋Š” CFRP ๋ณด๊ฐ•๊ทผ ํ™œ์šฉ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋Œ€ํ•œ ๋ถ€์ฐฉ ๋ฐ ๊ตฌ์กฐ ํŠน์„ฑ ๋“ฑ ๋‹ค์–‘ํ•œ ์—ฐ๊ตฌ๊ฐ€ ์„ ํ–‰๋˜์–ด์•ผ ํ•œ๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

๋ณธ ์—ฐ๊ตฌ๋Š” ๊ตญํ† ๊ตํ†ต๋ถ€/๊ตญํ† ๊ตํ†ต๊ณผํ•™๊ธฐ์ˆ ์ง„ํฅ์›์˜ ์ง€์›(๊ณผ์ œ๋ฒˆํ˜ธ 21NANO-B156177-02)์œผ๋กœ ์ˆ˜ํ–‰๋˜์—ˆ์Šต๋‹ˆ๋‹ค. ์ด์— ๊ฐ์‚ฌ๋“œ๋ฆฝ๋‹ˆ๋‹ค.

References

1 
ACI Committee 318. , 2019, Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary, Farmington Hills, MI; American Concrete Institute (ACI)Google Search
2 
Ankur N., Singh N., 2021, Performance of Cement Mortars and Concretes Containing Coal Bottom Ash: A Comprehensive Review, Renewable and Sustainable Energy Reviews, Vol. 149, pp. 111361DOI
3 
ASTM C1609 , 2020, Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete (Using Beam with Third- Point Loading), West Conshohocken. PA; ASTM International.Google Search
4 
ASTM C567 , 2020, Standard Test Method for Determining Density of Structural Lightweight Concrete, West Conshohocken. PA; ASTM International.Google Search
5 
Baeza F. J., Galao O., Vegas I. J., Cano M., Garcรฉs P., 2018, Influence of Recycled Slag Aggregates on the Conductivity and Strain Sensing Capacity of Carbon Fiber Reinforced Cement Mortars, Construction and Building Materials, Vol. 184, pp. 311-319DOI
6 
Baoyi L., Yuping D., Yuefang Z., Shunhua L., 2011, Electromagnetic Wave Absorption Properties of Cement- Based Composites Filled with Porous Materials, Materials and Design, Vol. 32, No. 5, pp. 3017-3020DOI
7 
Choi J., Yuan T., Hong S., Yoon Y., 2020, Evaluating of Electromagnetic Shielding Characteristics of Reinforced Concrete Using Reinforcing Details, Journal of the Korean Society of Hazard Mitigation, Vol. 20, No. 5, pp. 245-254Google Search
8 
Chung D. D. L., 2020, Materials for Electromagnetic Interference Shielding, Materials Chemistry and Physics, Vol. 255DOI
9 
Fan Y., Zhang L., Volski V., Vandenbosch G. A. E., Blanpain B., Guo M., 2019, Utilization of Stainless-Steel Furnace Dust as an Admixture for Synthesis of Cement-Based Electromagnetic Interference Shielding Composites, Scientific Reports, Vol. 7, No. 1, pp. 1-8DOI
10 
Hong S. H., Choi J. S., Lee J., Yoon Y. S., 2020a, Optimal Mix Design and Quality Properties of 50 MPa Self-Consolidating Lightweight Concrete, Journal of the Korean Society of Hazard Mitigation, Vol. 20, No. 6, pp. 135-142Google Search
11 
Hong S. H., Yuan T. F., Choi J. S., Yoon Y. S., 2020b, Effects of Steelmaking Slag and Moisture on Electrical Properties of Concrete, Materials, Vol. 13, No. 12, pp. 2675DOI
12 
Hong S. H., Yuan T. F., Choi J. S., Yoon Y. S., 2021, Assessing the Effects of Steelmaking Slag Powder on the Pore Structure and Durability of Concrete, Journal of the Korean Society of Hazard Mitigation, Vol. 21, No. 1, pp. 1-11Google Search
13 
Hong S., Yuan T., Choi J., Yoon Y., 2019, Evaluating Microstructure and Self-Sensing Properties of High-Strength Concrete with Electric-Arc-Furnace Oxidizing Slag, Journal of the Korean Society of Hazard Mitigation, Vol. 19, No. 5, pp. 189-197Google Search
14 
Hyun S. Y., Du J. K., Lee H. J., Lee K. W., Lee J. H., Jung C., Kim E. J., Kim W., Yook J. G., 2014, Analysis of Shielding Effectiveness of Reinforced Concrete Against High-Altitude Electromagnetic Pulse, IEEE Transactions on Electromagnetic Compatibility, Vol. 56, No. 6, pp. 1488-1496DOI
15 
Hyun S. Y., Lee K. W., Kim M. S., Yook J. G., 2012, Electromagnetic Modeling of Shielding Effectiveness of Reinforced Concrete Walls, The Journal of Korean Institute of Electromagnetic Engineering and Science, Vol. 23, No. 3, pp. 384-391DOI
16 
KATS , 2017, Standard Test Method for Compressive Strength of Concrete (KS F 2405). Seoul, Korea, Korea Agency for Technology and Standards (KATS), Korea Standard Association (KSA). (In Korean)Google Search
17 
Kim H. K., Lee H. K., 2011, Use of Power Plant Bottom Ash as Fine and Coarse Aggregates in High-Strength Concrete, Construction and Building Materials, Vol. 25, No. 2, pp. 1115-1122DOI
18 
Kim Y. H., Kim H. Y., Yang K. H., Ha J. S., 2020, Evaluation of Workability and Mechanical Properties of Bottom Ash Aggregate Concrete, Applied Sciences, Vol. 10, No. 22, pp. 8016DOI
19 
Lee J. Y., Choi J. S., Yuan T. F., Yoon Y. S., Mitchell D., 2019, Comparing Properties of Concrete Containing Electric Arc Furnace Slag and Granulated Blast Furnace Slag, Materials, Vol. 12, No. 9, pp. 1371DOI
20 
MOLIT , 2021a, Korean Construction Specification: General Concrete (KCS 14 20 10). Sejong, Korea, Ministry of Land, Infrastructure and Transport (MOLIT). (In Korean)Google Search
21 
MOLIT , 2021b, Korean Construction Specification: Light Weight Aggregate Concrete (KCS 14 20 20). Sejong, Korea, Ministry of Land, Infrastructure and Transport (MOLIT). (In Korean)Google Search
22 
Ozturk M., Akgol O., Sevim U. K., Karaaslan M., Demirci M., Unal E., 2018, Experimental Work on Mechanical, Electromagnetic and Microwave Shielding Effectiveness Properties of Mortar Containing Electric Arc Furnace Slag, Construction and Building Materials, Vol. 165, pp. 58-63DOI
23 
Roslan N. H., Ismail M., Abdul-Majid Z., Ghoreishiamiri S., Muhammad B., 2016, Performance of Steel Slag and Steel Sludge in Concrete, Construction and Building Materials, Vol. 104, pp. 16-24DOI
24 
Wanasinghe D., Aslani F., Ma G., 2020, Effect of Water to Cement Ratio, Fly Ash, and Slag on the Elctromagnetic Shielding Effectiveness of Mortar, Construction and Building Materials, Vol. 256, pp. 119409DOI
25 
Wang Z., Zhang T., Zhou L., 2016, Investigation on Electromagnetic and Microwave Absorption Properties of Copper Slag-Filled Cement Mortar, Cement and Concrete Composites, Vol. 74, pp. 174-181DOI
26 
Wongsa A., Zaetang Y., Sata V., Chindaprasirt P., 2016, Properties of Lightweight Fly Ash Geopolymer Concrete Containing Bottom Ash as Aggregates, Construction and Building Materials, Vol. 111, pp. 637-643DOI
27 
Xue J., Wang X., Wang Z., Xu S., Liu H., 2021, Investigations on Influencing Factors of Resistivity Measurement for Graphite Tailings Concrete, Cement and Concrete Composites, Vol. 123, pp. 104206DOI
28 
Yehia S., Qaddoumi N., Hassan M., Swaked B., 2014, Conductive Concrete for Electromagnetic Shielding Applications, Advances in Civil Engineering Materials, Vol. 3, No. 1, pp. 270-290URL
29 
Yoo D. Y., Kang M. C., Choi H. J., Shin W., Kim S., 2020, Electromagnetic Interference Shielding of Multi-Cracked High-Performance Fiber-Reinforced Cement Composites - Effects of Matrix Strength and Carbon Fiber, Construction and Building Materials, Vol. 261, pp. 119949DOI
30 
You I., Yoo D. Y., Kim S., Kim M. J., Zi G., 2017, Electrical and Self-Sensing Properties of Ultra-High-Performance Fiber-Reinforced Concrete with Carbon Nanotubes, Sensors, Vol. 17, No. 11, pp. 2481DOI
31 
Zhang X., Sun W., 2012, Electromagnetic Shielding and Absorption Properties of Fiber Reinforced Cementitious Composites, Journal of Wuhan University of Technology- Mater. Sci. Ed., Vol. 27, pp. 172-176DOI