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  1. ๊ฐ•์›๋Œ€ํ•™๊ต ๊ฑด์„ค์œตํ•ฉํ•™๋ถ€ ํ† ๋ชฉ๊ณตํ•™์ „๊ณต ์—ฐ๊ตฌ๊ต์ˆ˜ (Research Professor, Department of Civil Engineering, Kangwon National University, Samcheok 25913, Rep. of Korea)
  2. ๊ฐ•์›๋Œ€ํ•™๊ต ๊ฑด์„ค์œตํ•ฉํ•™๋ถ€ ํ† ๋ชฉ๊ณตํ•™์ „๊ณต ๊ต์ˆ˜ (Professor, Department of Civil Engineering, Kangwon National University, Samcheok 25913, Rep. of Korea)



SIFRCC, ๋‚ด์ถฉ๊ฒฉ์„ฑ๋Šฅ, ๊ณ ์˜จ๋…ธ์ถœ, ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ, ๊ทนํ•œํ•˜์ค‘
SIFRCC, impact and blast resistance, exposure temperature, energy absorbing capacity, extreme loading cases

1. ์„œ ๋ก 

์ „ ์„ธ๊ณ„์ ์œผ๋กœ ์ถฉ๋Œ, ํญ๋ฐœ์‚ฌ๊ณ ์— ์˜ํ•œ ์œ„ํ—˜์„ฑ์ด ์ ์ฐจ ๋†’์•„์ง€๊ณ  ์žˆ์œผ๋ฉฐ, ๊ตญ์ œ์ •์„ธ์˜ ๋ณ€ํ™” ์†์—์„œ ์‚ฌ๊ณ ๋ฐœ์ƒ ๊ฐ€๋Šฅ์„ฑ์€ ํ•ญ์ƒ ์กด์žฌํ•œ๋‹ค. ์ถฉ๋Œ๊ณผ ํญ๋ฐœ์‚ฌ๊ณ  ๋ฐœ์ƒ ์‹œ, ์ธ๊ตฌ๋ฐ€์ง‘ํ˜• ์ฃผ๊ฑฐ ํŠน์„ฑ์„ ์ง€๋‹Œ ๋Œ€๋„์‹œ์—์„œ๋Š” ํ”ผํ•ด์˜ ๊ทœ๋ชจ๊ฐ€ ๋” ์ปค์งˆ ์ˆ˜ ์žˆ๋‹ค(Kim et al. 2015(6)). ๋˜ํ•œ ์ด๋Ÿฌํ•œ ์ถฉ๊ฒฉ ๋ฐ ํญ๋ฐœ์‚ฌ๊ณ ๋“ค์— ์˜ํ•ด ํ•„์—ฐ์ ์œผ๋กœ ๋™๋ฐ˜๋˜๋Š” ํ™”์žฌ ์—ญ์‹œ ์ฆ๊ฐ€ํ•˜๊ณ  ์žˆ๋‹ค.

๊ณผ๊ฑฐ์— ์„ค๊ณ„๋œ ๊ธฐ์กด์˜ ์‚ฌํšŒ๊ธฐ๋ฐ˜์‹œ์„ค๋ฌผ ๋ฐ ํ† ๋ชฉ๊ตฌ์กฐ๋ฌผ์€ ๋ฐฉํ˜ธโ€ง๋ฐฉํญ์„ฑ๋Šฅ ๋ฐ ๋‚ดํ™”์„ฑ๋Šฅ์„ ๊ณ ๋ คํ•˜์ง€ ์•Š์•˜๊ธฐ ๋•Œ๋ฌธ์— ์˜ˆ์ƒํ•˜์ง€ ๋ชปํ•œ ์ถฉ๋Œ ๋˜๋Š” ํญ๋ฐœ์‚ฌ๊ณ , ๊ทธ์— ๋”ฐ๋ฅธ ํ™”์žฌ์— ์ทจ์•ฝํ•œ ํŠน์ง•์„ ๊ฐ€์ง€๊ณ  ์žˆ๋‹ค(Kim 2017(5)). ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์ถฉ๊ฒฉ ๋ฐ ํญ๋ฐœํ•˜์ค‘์— ๋Œ€ํ•˜์—ฌ ์ถฉ๋ถ„ํ•œ ์ €ํ•ญ์„ฑ๋Šฅ์„ ๊ฐ€์ง€์ง€ ์•Š๊ธฐ ๋•Œ๋ฌธ์— RC ๊ตฌ์กฐ๋ฌผ์˜ ์ทจ์„ฑํŒŒ๊ดด์— ๋”ฐ๋ฅธ ํŒŒํŽธ์œผ๋กœ ์ธํ•œ ์ธ๋ช…ํ”ผํ•ด ๋“ฑ ๋ฐœ์ƒ์˜ ์šฐ๋ ค๊ฐ€ ์žˆ๋‹ค(Kim 2017(5)). ์ด๋Ÿฌํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์ ์„ ๊ฐœ์„ ํ•˜๊ณ , ๋‚ด์ถฉ๊ฒฉ์„ฑ๋Šฅ์„ ํ–ฅ์ƒ์‹œํ‚ค๊ธฐ ์œ„ํ•ด์„œ๋Š” ์ผ๋ฐ˜ ์„ฌ์œ ๋ณด๊ฐ• ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ์ ์ธ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์˜ ๊ทน๋Œ€ํ™”๋ฅผ ์œ„ํ•˜์—ฌ ๊ณ ํ˜ผ์ž…๋ฅ (Vf 4% ์ด์ƒ) ๊ณ ์„ฑ๋Šฅ ๊ฐ•์„ฌ์œ ๋ณด๊ฐ• ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด๊ฐ€ ๊ทธ ๋Œ€์•ˆ์ด ๋  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ์˜ˆ์ƒํ•œ๋‹ค(Kim et al. 2015(6); Kim 2017(5)).

๊ตญ๋‚ด์—์„œ๋Š” ์ถฉ๋Œ ๋ฐ ํญ๋ฐœ ์‚ฌ๊ณ ์— ๋Œ€ํ•œ ๋ฐฉํ˜ธโ€ง๋ฐฉํญ ๊ด€๋ จ ์‹œ์žฅ์ด ์ฃผ๋กœ ํ™”ํ•™ ํ”Œ๋žœํŠธ, ์›์ „ ๊ตฌ์กฐ๋ฌผ ๋ฐ ๊ตญ๋ฐฉ ์‹œ์„ค๋ฌผ ๋“ฑ๊ณผ ๊ฐ™์€ ์ผ๋ถ€ ๊ตญ๊ฐ€ ์ค‘์š”์‹œ์„ค์— ํ•œ์ •๋˜์–ด ์žˆ๋‹ค. ์‹ ์„ค ๊ตฌ์กฐ๋ฌผ์— ๋Œ€ํ•œ ๋ฐฉํ˜ธโ€ง๋ฐฉํญ ๋ฐ ๋‚ดํ™”์„ฑ๋Šฅ ๊ธฐ๋Šฅ์„ ๋ถ€์—ฌํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ๋ณ„๋„์˜ ๋Œ€์‘์ฑ… ๋งˆ๋ จ๊ณผ ๊ณ ์„ฑ๋Šฅ ๋ณด๊ฐ•์ž์žฌ์˜ ๊ฐœ๋ฐœ ๋ฐ ์ ์šฉ๊ธฐ์ˆ ์ด ํ•„์š”ํ•œ ์‹ค์ •์ด๋‹ค(Lee et al. 2015(7)).

๋”ฐ๋ผ์„œ ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์ถฉ๊ฒฉ ๋˜๋Š” ํญ๋ฐœ๊ณผ ๊ฐ™์ด ์ž‘์šฉ์‹œ๊ฐ„์ด ๋งค์šฐ ์งง์€ ํ•˜์ค‘์— ๋Œ€ํ•œ ๋‚ด์ถฉ๊ฒฉ์„ฑ๋Šฅ ์ฆ๋Œ€๋ฅผ ์œ„ํ•˜์—ฌ ๊ณ ํ˜ผ์ž… ์Šฌ๋Ÿฌ๋ฆฌ ์ถฉ์ „ ๊ฐ•์„ฌ์œ ๋ณด๊ฐ• ์ฝ˜ํฌ๋ฆฌํŠธ(Slurry Infiltrated Fiber Concrete, SIFCON) ํ˜•ํƒœ์˜ ๊ณ ์„ฑ๋Šฅ ๊ฐ•์„ฌ์œ ๋ณด๊ฐ• ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด(High Performance Fiber Reinforced Cementitious Composite, HPFRCC)์ธ ์Šฌ๋Ÿฌ๋ฆฌ ์ถฉ์ „ ๊ฐ•์„ฌ์œ ๋ณด๊ฐ• ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด(Slurry Infiltrated Fiber Reinforced Cementitious Composite, SIFRCC)๋ฅผ ๊ฐœ๋ฐœ์„ ํ•˜์˜€์œผ๋ฉฐ, ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ํœจ์„ฑ๋Šฅ ํŠน์„ฑ์„ ๋ถ„์„ํ•˜๊ณ ์ž ํ•œ๋‹ค. ๊ธฐ ๊ฐœ๋ฐœ๋œ SIFRCC๋Š” ์ผ๋ฐ˜ ์„ฌ์œ ๋ณด๊ฐ• ์ฝ˜ํฌ๋ฆฌํŠธ์™€๋Š” ๋‹ค๋ฅด๊ฒŒ ์„ฌ์œ ๋ฅผ ๋จผ์ € ์ฑ„์›Œ ๋„ฃ๊ณ  ๊ทธ ์‚ฌ์ด์‚ฌ์ด๋ฅผ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ์ถฉ์ „ํ•˜๋Š” ํ˜•ํƒœ๋กœ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ์˜ ๊ทน๋Œ€ํ™”๋ฅผ ๊ธฐ๋Œ€ํ•  ์ˆ˜ ์žˆ๋‹ค. ๊ฐ•์„ฌ์œ  ์‚ฌ์ด์˜ ์ถฉ์ „์„ฑ๋Šฅ ๊ฐœ์„ ์„ ์œ„ํ•ด ๊ตต์€ ๊ณจ์žฌ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š๋Š” ํŠน์ง•์„ ๊ฐ–๊ณ  ์žˆ๋‹ค. ๋˜ํ•œ SIFRCC์™€ ๊ฐ™์€ ํŠน์ˆ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ณ ์˜จ๋…ธ์ถœ ์žฌ๋ฃŒ ๊ฑฐ๋™ ํŠน์„ฑ ์ž๋ฃŒ๊ฐ€ ๋งค์šฐ ๋ถ€์กฑํ•˜๋ฏ€๋กœ ์ด ์—ฐ๊ตฌ๋ฅผ ํ†ตํ•ด ๊ธฐ์ดˆ์ ์ธ ์ž๋ฃŒ ์ œ๊ณต์ด ๊ฐ€๋Šฅํ•  ๊ฒƒ์œผ๋กœ ๊ธฐ๋Œ€ํ•œ๋‹ค.

2. ์‹คํ—˜๊ฐœ์š”

2.1 ์‚ฌ์šฉ์žฌ๋ฃŒ

2.1.1 ์‹œ๋ฉ˜ํŠธ

์ด ์—ฐ๊ตฌ์—์„œ๋Š” 1์ข… ๋ณดํ†ตํฌํ‹€๋žœ๋“œ์‹œ๋ฉ˜ํŠธ๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ๋ฌผ๋ฆฌ์ โ€งํ™”ํ•™์  ํŠน์„ฑ์€ Table 1๊ณผ ๊ฐ™๋‹ค.

Table 1. Material properties of used ordinary Portland cement

Physical properties

Specific gravity

Fineness (cm2/g)

Stability

(%)

Setting time

(min)

LOI (%)

Initial

Final

3.15

3,400

0.10

230

410

2.58

Chemical compositions (%, mass)

SiO2

CaO

MgO

SO3

Al2O3

21.95

60.12

3.32

2.11

6.59

2.1.2 ์‹ค๋ฆฌ์นด ํ“ธ

์ถฉ์ „์šฉ ์Šฌ๋Ÿฌ๋ฆฌ์˜ ๊ณ ๊ฐ•๋„ ๋ฐœํ˜„์„ ์œ„ํ•˜์—ฌ ํ˜ผํ™”์žฌ๋กœ์„œ ์‹ค๋ฆฌ์นด ํ“ธ์„ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ์‚ฌ์šฉํ•œ ์‹ค๋ฆฌ์นด ํ“ธ์˜ ๋ฌผ๋ฆฌ์ โ€งํ™”ํ•™์  ํŠน์„ฑ์€ Table 2์™€ ๊ฐ™๋‹ค.

Table 2. Material properties of used silica fume

Physical properties

Specific gravity

Fineness (cm2/g)

2.10

200,000

Chemical compositions (%, mass)

SiO2

CaO

MgO

SO3

Al2O3

96.00

0.38

0.10

-

0.25

2.1.3 ๊ณจ์žฌ

์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์Šฌ๋Ÿฌ๋ฆฌ์˜ ์ถฉ์ „์„ฑ๋Šฅ์„ ๊ฐœ์„ ํ•˜๊ณ  ์žฌ๋ฃŒ๋ถ„๋ฆฌ ์ €๊ฐ์„ ์œ„ํ•˜์—ฌ 0.5 mm ์ดํ•˜์˜ ์ง๊ฒฝ์„ ๊ฐ–๋Š” ์ž”๊ณจ์žฌ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๋˜ํ•œ ๊ฒฐํ•ฉ์žฌ ๋Œ€๋น„ ์ž”๊ณจ์žฌ๋Ÿ‰์€ 1:0.5๋กœ ์„ค์ •ํ•˜์˜€์œผ๋ฉฐ, ๊ฐ•์„ฌ์œ  ์‚ฌ์ด์‚ฌ์ด์˜ ์ถฉ์ „์„ ์œ„ํ•˜์—ฌ ๊ตต์€๊ณจ์žฌ๋Š” ์‚ฌ์šฉํ•˜์ง€ ์•Š์•˜๋‹ค. Fig. 1์€ ์‚ฌ์šฉ ์ž”๊ณจ์žฌ์˜ ์ž…๋„๋ถ„ํฌ๋ฅผ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค.

Fig. 1. Grading curve of fine aggregate

../../Resources/kci/JKCI.2019.31.2.139/fig1.png

2.1.4 ๊ณ ์„ฑ๋Šฅ๊ฐ์ˆ˜์ œ

์Šฌ๋Ÿฌ๋ฆฌ์˜ ์œ ๋™์„ฑ์„ ํ–ฅ์ƒ์‹œํ‚ค๊ณ , ์ถฉ์ „์„ฑ๋Šฅ์„ ํ™•๋ณดํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ํด๋ฆฌ์นด๋ฅด๋ณธ์‚ฐ๊ณ„ ๊ณ ์„ฑ๋Šฅ๊ฐ์ˆ˜์ œ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. Table 3์€ ์‚ฌ์šฉํ•œ ๊ณ ์„ฑ๋Šฅ๊ฐ์ˆ˜์ œ์˜ ์„ฑ์งˆ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค.

Table 3. Properties of polycarboxylate high range water reducer (HRWR)

Specific gravity

pH

Alkali content

(%)

Chloride content (%)

1.05 ยฑ 0.05

5.0 ยฑ 1.5

less than 0.01

less than 0.01

2.1.5 ๊ฐ•์„ฌ์œ 

๊ฐ•์„ฌ์œ ๋Š” ๋ฒจ๊ธฐ์— B์‚ฌ์—์„œ ์ƒ์‚ฐํ•˜๋Š” ์ง๊ฒฝ 0.9 mm, ๊ธธ์ด 60 mm, ํ˜•์ƒ๋น„ 65๋ฅผ ๊ฐ–๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋ณด๊ฐ•์šฉ ๊ฐ•์„ฌ์œ (5D)๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ์‚ฌ์šฉํ•œ ๊ฐ•์„ฌ์œ ์˜ ํŠน์ง•์€ ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์šฉ ๊ฐ•์„ฌ์œ (3D)์™€ ๋™์ผํ•˜๊ฒŒ ํ›„ํฌ ํƒ€์ž…์ด๋‚˜, Fig. 2์™€ ๊ฐ™์ด ํ›„ํฌ์˜ ํ˜•ํƒœ๊ฐ€ ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์šฉ ๊ฐ•์„ฌ์œ ๋ณด๋‹ค ๋‘ ๋ฒˆ ๋” ๊บพ์—ฌ ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค์™€์˜ ๋ถ€์ฐฉ ์ฆ๊ฐ€ ๋ฐ ์•ต์ปค๋ง ํšจ๊ณผ๋กœ ์ธํ•˜์—ฌ ๋ณด๋‹ค ์šฐ์ˆ˜ํ•œ ์ธ์„ฑ์„ ํ™•๋ณดํ•  ์ˆ˜ ์žˆ๋‹ค. ์„ฌ์œ  ํ›„ํฌ ํƒ€์ž…์— ๋”ฐ๋ฅธ ์—ฐ๊ตฌ๊ฒฐ๊ณผ 3D ๊ฐ•์„ฌ์œ ๋ณด๋‹ค 5D ๊ฐ•์„ฌ์œ ๊ฐ€ 1.8๋ฐฐ ์ด์ƒ ์šฐ์ˆ˜ํ•œ ์ธ๋ฐœ ์ €ํ•ญ์„ฑ๋Šฅ์„ ๋ฐœํœ˜ํ•˜๋ฉฐ(RACEK and VACLAC 2015(9)), ์ด ์—ฐ๊ตฌ์—์„œ ๋ชฉํ‘œํ•˜๋Š” ์ธ์„ฑ ์ฆ์ง„ ํšจ๊ณผ์— ๊ธฐ์—ฌํ•  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋˜์–ด 5D ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉ ๊ฐ•์„ฌ์œ ๋กœ ๊ฒฐ์ •ํ•˜์˜€๋‹ค. ๋˜ํ•œ ์‚ฌ์šฉ ๊ฐ•์„ฌ์œ ์˜ ์ธ์žฅ๊ฐ•๋„๋Š” 2,400 MPa์ด๋‹ค.

Fig. 2. Shape of steel fiber (5D vs. 3D)

../../Resources/kci/JKCI.2019.31.2.139/fig2.png

2.2 SIFRCC

์ด ์—ฐ๊ตฌ์—์„œ ๊ฐœ๋ฐœํ•œ SIFRCC๋Š” ์ถฉ๊ฒฉ ๋˜๋Š” ํญ๋ฐœ๊ณผ ๊ฐ™์€ ๊ทนํ•œํ•˜์ค‘์— ๋Œ€ํ•œ ์ €ํ•ญ์„ฑ๋Šฅ์„ ์ฆ๋Œ€์‹œํ‚ค๊ธฐ ์œ„ํ•˜์—ฌ ๊ฐ•์„ฌ์œ ์˜ ๊ณ ํ˜ผ์ž…์ด ๊ฐ€๋Šฅํ•œ SIFCON ํ˜•ํƒœ์˜ HPFRCC๋กœ์„œ ๊ฐ•์„ฌ์œ ๋ฅผ ๋ฏธ๋ฆฌ ํฌ์„คํ•˜๊ณ  ๊ณ ์„ฑ๋Šฅ์˜ ์Šฌ๋Ÿฌ๋ฆฌ๋ฅผ ์ถฉ์ „ํ•˜๋Š” ํ˜•ํƒœ๋กœ SIFRCC๋ฅผ ์ œ์ž‘ํ•˜์˜€๋‹ค. Fig. 3์€ SIFRCC ์ œ์ž‘ ๊ณผ์ •์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค.

Fig. 3. Fabrication process of SIFRCC

../../Resources/kci/JKCI.2019.31.2.139/fig3.png

2.3 ๋ฐฐํ•ฉ

๋ฏธ๋ฆฌ ํฌ์„คํ•œ ๊ฐ•์„ฌ์œ  ๋‚ด๋ถ€๊ณต๊ฐ„์„ ์ถฉ์ „ํ•˜๊ธฐ ์œ„ํ•œ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ๋Š” ์ถฉ์ „์„ฑ๋Šฅ์„ ์œ„ํ•˜์—ฌ ๋ฌผ-๊ฒฐํ•ฉ์žฌ๋น„๋ฅผ 0.4๋กœ ๊ณ ์ •ํ•˜์˜€์œผ๋ฉฐ, ๊ณ ์„ฑ๋Šฅ๊ฐ์ˆ˜์ œ ์‚ฌ์šฉ๋Ÿ‰์„ ๊ฒฐํ•ฉ์žฌ ์ค‘๋Ÿ‰๋Œ€๋น„ 2.5%๋กœ ์„ค์ •ํ•˜์˜€๋‹ค. ๋˜ํ•œ ์žฌ๋ฃŒ๋ถ„๋ฆฌ ์ €๊ฐ ๋ฐ ์†Œ์š” ๊ฐ•๋„ ํ™•๋ณด๋ฅผ ์œ„ํ•˜์—ฌ ์ž”๊ณจ์žฌ๋Ÿ‰์€ ๊ฒฐํ•ฉ์žฌ ์ค‘๋Ÿ‰์˜ 50%, ์‹ค๋ฆฌ์นด ํ“ธ์€ ์‹œ๋ฉ˜ํŠธ ์ค‘๋Ÿ‰์˜ 15%๋ฅผ ์น˜ํ™˜ํ•˜์—ฌ ๋ฐฐํ•ฉ์„ ์ง„ํ–‰ํ•˜์˜€๋‹ค. Table 4๋Š” ์‚ฌ์šฉ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ์˜ ๋ฐฐํ•ฉ ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค. ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์€ 8%๋กœ ๊ณ ์ •ํ•˜์—ฌ SIFRCC๋ฅผ ์ œ์ž‘ํ•˜์˜€๋‹ค.

Table 4. Mix proportions of slurry mortar

W/B ratio

0.4

Superplasticizer

2.5 % (cement weight percent)

Fine aggregate content

1 : 0.5 (binder : fine aggregate)

Silica fume

15 % (cement weight percent)

2.4 ์‹คํ—˜๋ฐฉ๋ฒ•

์ด ์—ฐ๊ตฌ์—์„œ๋Š” ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋…ธ์ถœ์˜จ๋„ 200 ยฐC ๋ฐ 400 ยฐC์—์„œ 2์‹œ๊ฐ„ ๋…ธ์ถœ ํ›„ SIFRCC์˜ ํœจ๊ฑฐ๋™ ํŠน์„ฑ์„ ๋ถ„์„ํ•˜์˜€๋‹ค. Fig. 4๋Š” 200 ยฐC ๋ฐ 400 ยฐC์˜ ์˜จ๋„๊ฐ€์—ด๊ณก์„ ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ์œผ๋ฉฐ, Fig. 5๋Š” ๊ณ ์˜จ๋…ธ์ถœ ์‹คํ—˜์ „๊ฒฝ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค.

Fig. 4. Heating curve for mortar slurry and SIFRCC

../../Resources/kci/JKCI.2019.31.2.139/fig4.png

Fig. 5. High temperature exposure of mortar slurry and SIFRCC

../../Resources/kci/JKCI.2019.31.2.139/fig5.png

๋˜ํ•œ ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ SIFRCC์˜ ํœจ์„ฑ๋Šฅ ํ‰๊ฐ€๋ฅผ ์œ„ํ•˜์—ฌ ASTM C 1609 Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete(Using Beam With Third-Point Loading)์— ์˜๊ฑฐํ•˜์—ฌ 100 ร— 100 ร— 350 mm์˜ ๊ฐ์ฃผํ˜• ์‹œํ—˜์ฒด๋ฅผ ์ œ์ž‘ํ•˜์—ฌ ํœจ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค(Kim et al. 2015(6); Kim 2017(5)). Fig. 6๊ณผ ๊ฐ™์ด 200ํ†ค๊ธ‰ ๋งŒ๋Šฅ์žฌ๋ฃŒ์‹œํ—˜๊ธฐ(UTM)๋กœ 4์  ๊ฐ€๋ ฅ์„ ํ•˜์˜€์œผ๋ฉฐ, ์‹œํ—˜์ฒด ์ค‘์•™๋ถ€ ๋ณ€์œ„๊ณ„(LVDT) 2๊ฐœ๋ฅผ ์žฅ์ฐฉํ•œ ๊ฑฐ์น˜๋Œ€(Japanese Yoke)๋ฅผ ํ™œ์šฉํ•˜์—ฌ ์ค‘์•™๋ถ€์˜ ์ฒ˜์ง ๋ณ€์œ„๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ํ•˜์ค‘ ๊ฐ€๋ ฅ์€ 1 mm/min์˜ ์†๋„๋กœ ๋ณ€์œ„์ œ์–ด ๋ฐฉ์‹์œผ๋กœ ํœจ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค(Kim et al. 2015(6); Kim 2017(5)). ํœจ์„ฑ๋Šฅ ํ‰๊ฐ€๋ฅผ ์œ„ํ•˜์—ฌ ASTM C 1609์˜ ์‹(1)๊ณผ ๊ฐ™์ด ํœจ๊ฐ•๋„๋ฅผ ์‚ฐ์ •ํ•˜์˜€๋‹ค.

Fig. 6. Bending test with third-point loading

../../Resources/kci/JKCI.2019.31.2.139/fig6.png

(1)
f=PLbd2

์—ฌ๊ธฐ์„œ, P๋Š” ์‹คํ—˜์—์„œ ์ธก์ •๋œ ์ตœ๋Œ€ ํ•˜์ค‘, L์€ ์ง€๊ฐ„๊ฑฐ๋ฆฌ(300 mm), b๋Š” ์‹œํ—˜์ฒด์˜ ๋„ˆ๋น„(100 mm), d๋Š” ์‹œํ—˜์ฒด์˜ ๋†’์ด(100 mm)์ด๋‹ค. ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ASTM C 1609์—์„œ ์ œ์‹œํ•˜๋Š” ์‹œํ—˜์ฒด ์ธ์„ฑ(specimen toughness)์„ ๊ณ„์‚ฐํ•˜์˜€์œผ๋‚˜, ์ด ์—ฐ๊ตฌ์—์„œ ๊ณ ๋ คํ•œ SIFRCC์˜ ํœจ๊ฑฐ๋™ ํŠน์„ฑ์ƒ ASTM C 1609์—์„œ ์ œ์‹œํ•˜๋Š” ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์—์„œ์˜ ์ง€๊ฐ„๊ฑฐ๋ฆฌ L์˜ 1/150๊นŒ์ง€์˜ ๋ฉด์ ์œผ๋กœ ์ •์˜๋˜๋Š” ๊ฒƒ์— ์ ํ•ฉํ•˜์ง€ ์•Š์œผ๋ฏ€๋กœ ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์„ ์ƒ๋Œ€์ ์œผ๋กœ ๋น„๊ตํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์—์„œ ์ฒ˜์ง 15 mm๊นŒ์ง€์˜ ๋ฉด์ ์œผ๋กœ ๋Œ€์ฒดํ•˜์—ฌ ์‹œํ—˜์ฒด ์ธ์„ฑ ํŠน์„ฑ์„ ๋น„๊ตโ€ง๋ถ„์„ํ•˜์˜€๋‹ค(Kim et al. 2015(6); Kim 2017(5)).

๋˜ํ•œ ์ฒซ ๋ฒˆ์งธ ํ”ผํฌ์ ์—์„œ์˜ ํ•˜์ค‘์„ ์„ ํ˜•ํƒ„์„ฑ๊ฑฐ๋™์œผ๋กœ ๊ฐ€์ •ํ•  ๊ฒฝ์šฐ, ์‹(2)๋ฅผ ํ†ตํ•ด ์ฒซ ๋ฒˆ์งธ ํ•˜์ค‘ ํ”ผํฌ์ ์—์„œ์˜ ์ฒ˜์ง์„ ๊ตฌํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์ด๋ฅผ ์ดˆ๊ธฐ๊ท ์—ด๋กœ ๊ฐ„์ฃผํ•  ์ˆ˜ ์žˆ๋‹ค(Ghosni et. al. 2014). ASTM C 1609์—์„œ๋Š” 100 ร— 100 ร— 350 mm ํฌ๊ธฐ์˜ ์‹œํ—˜์ฒด์˜ ์ฒซ ๋ฒˆ์งธ ํ•˜์ค‘ ํ”ผํฌ์ ์—์„œ์˜ ์ฒ˜์ง์„ ์•ฝ 0.04 mm๋กœ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค.

(1)
ฮด1=23P1L31296EI[1+216d2(1+ฮผ)115L2]

์—ฌ๊ธฐ์„œ, ฮด1์€ ์ฒซ ๋ฒˆ์งธ ํ•˜์ค‘ ํ”ผํฌ์ ์—์„œ์˜ ์ฒ˜์ง, P1์€ ์ฒซ ๋ฒˆ์งธ ํ”ผํฌ์ ์—์„œ์˜ ํ•˜์ค‘, L์€ ์ง€๊ฐ„๊ฑฐ๋ฆฌ, E๋Š” ์‹œํ—˜์ฒด์˜ ํƒ„์„ฑ๊ณ„์ˆ˜, I๋Š” ๋‹จ๋ฉด 2์ฐจ ๋ชจ๋ฉ˜ํŠธ, d๋Š” ํŒŒ๊ดด ์‹œ ํ‰๊ท  ๊นŠ์ด, ฮผ๋Š” ์‹œํ—˜์ฒด์˜ ํฌ์•„์†ก ๋น„์ด๋‹ค.

3. ์‹คํ—˜๊ฒฐ๊ณผ ๋ฐ ๋ถ„์„

3.1 ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ ๊ณ ์˜จ๋…ธ์ถœ ํŠน์„ฑ

Fig. 7์€ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ์˜ ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์••์ถ•๊ฐ•๋„ ๋ฐ ์ค‘๋Ÿ‰์†์‹ค๋ฅ ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค. ๊ณ ์˜จ๋…ธ์ถœ์„ ํ•˜์ง€ ์•Š์€ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ์˜ ์••์ถ•๊ฐ•๋„๋Š” 64 MPa ์ˆ˜์ค€์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. 200 ยฐC ๋ฐ 400 ยฐC 2์‹œ๊ฐ„ ๋…ธ์ถœ ํ›„ ์••์ถ•๊ฐ•๋„๋Š” 200 ยฐC์˜ ๊ฒฝ์šฐ, ์•ฝ 13.3% ๊ฐ์†Œํ•œ 55.5 MPa์˜ ์••์ถ•๊ฐ•๋„ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋˜ํ•œ 400 ยฐC ๋…ธ์ถœํ•œ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ์˜ ์••์ถ•๊ฐ•๋„๋Š” ๊ณ ์˜จ๋…ธ์ถœํ•˜์ง€ ์•Š์€ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ๋ณด๋‹ค ์•ฝ 20.5% ๊ฐ์†Œํ•œ 50.9 MPa๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ์™€ ๊ฐ™์€ ์‹œ๋ฉ˜ํŠธ ํŽ˜์ด์ŠคํŠธ๋Š” 100 ยฐC ์ดํ•˜์—์„œ๋Š” ์ˆ˜๋ถ„๊ฐ์†Œ์— ์˜ํ•œ ๊ฑด์กฐ์ˆ˜์ถ•์€ ๋‚ฎ์€ ์ˆ˜๋ถ„๋Ÿ‰์—์„œ ์—ดํŒฝ์ฐฝ๊ณ„์ˆ˜์˜ ์ฆ๊ฐ€์— ์˜ํ•ด ์ƒ์‡„๋˜๋ฉฐ, ๋ถ€ํ”ผ๊ฐ€ ์ „์ฒด์ ์œผ๋กœ ์ฆ๊ฐ€ํ•œ๋‹ค(Sidney Mindess et. al. 2003(11)). ๋˜ํ•œ ์‹œ๋ฉ˜ํŠธ ํŽ˜์ด์ŠคํŠธ์™€ ๊ณจ์žฌ๋Š” 80~90 ยฐC์˜ ์˜จ๋„์—์„œ๋Š” ๋ชจ๋‘ ํŒฝ์ฐฝํ•˜๊ฒŒ ๋˜๊ณ , ์•ฝ 110 ยฐC ์ด์ƒ์ด ๋˜๋ฉด ๊ณจ์žฌ๋Š” ๊ณ„์†ํ•ด์„œ ํŒฝ์ฐฝํ•˜์ง€๋งŒ, ์‹œ๋ฉ˜ํŠธ ํŽ˜์ด์ŠคํŠธ๋Š” ์ˆ˜์ถ•ํ•œ๋‹ค๊ณ  ๋ณด๊ณ ๋˜๊ณ  ์žˆ๋‹ค(Aldea et al. 1997(1); Bang 2017(3)). ํ•˜์ง€๋งŒ ์ด ์—ฐ๊ตฌ์—์„œ ๊ณ ๋ คํ•œ 200 ยฐC ๋ฐ 400 ยฐC์—์„œ๋Š” ๋ชจ๋“  ์ˆ˜๋ถ„์ด ํŽ˜์ด์ŠคํŠธ๋กœ๋ถ€ํ„ฐ ๋น ์ ธ๋‚˜๊ฐˆ ๋•Œ๊นŒ์ง€ ๊ฑด์กฐ์ˆ˜์ถ•์ด ๋ฐœ์ƒํ•˜๋ฉฐ, ๋†’์€ ์˜จ๋„์—์„œ ๋‚ด๋ถ€์ ์œผ๋กœ ์ˆ˜ํ™”๋ฌผ ๊ตฌ์„ฑ์˜ ํŒŒ๊ดด๊ฐ€ ๋ฐœ์ƒํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์••์ถ•๊ฐ•๋„๊ฐ€ ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 7. Test results of compressive strength and weight loss of mortar slurry with respect to exposure temperature

../../Resources/kci/JKCI.2019.31.2.139/fig7.png

๋˜ํ•œ ์••์ถ•๊ฐ•๋„ ์ €ํ•˜ ์›์ธ์œผ๋กœ ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ์˜ ์ค‘๋Ÿ‰์†์‹ค์ด ๊ทธ ์›์ธ์ด ๋  ์ˆ˜ ์žˆ๋‹ค. 200 ยฐC ๋ฐ 400 ยฐC 2์‹œ๊ฐ„ ๋…ธ์ถœ ํ›„ ์ค‘๋Ÿ‰์†์‹ค๋ฅ ์€ ๊ฐ๊ฐ 14.6%, 17.9% ๊ฐ์†Œํ•œ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์‹œ๋ฉ˜ํŠธ ๊ฒฝํ™”์ฒด๊ฐ€ ๊ณ ์˜จ์— ๋…ธ์ถœ๋˜๋ฉด ์•ฝ 105 ยฐC์—์„œ ์ˆ˜๋ถ„์ด ์ฆ๋ฐœํ•˜๋ฉฐ, 180 ยฐC์—์„œ ํ™”ํ•™์ ์œผ๋กœ ๊ฒฐํ•ฉํ•˜๊ณ  ์žˆ๋˜ ์ˆ˜๋ถ„์˜ ์ผ๋ถ€๊ฐ€ ์ฆ๋ฐœํ•˜๊ธฐ ์‹œ์ž‘ํ•œ๋‹ค. ๋˜ํ•œ ์•ฝ 250~350 ยฐC์—์„œ๋Š” ์นผ์Š˜์‹ค๋ฆฌ์ผ€์ดํŠธ ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์€ ๊ทธ ํ•จ์œ ์ˆ˜๋ถ„์˜ ์•ฝ 20% ์†์‹ค์„ ์ผ์œผํ‚จ๋‹ค๊ณ  ๋ณด๊ณ ๋˜๊ณ  ์žˆ๋‹ค(Menzel 1943(8); Sanjayan and Stocks 1993(10); Bang 2017(3)). ์ด๋Ÿฌํ•œ ์›์ธ๋“ค๋กœ ์ธํ•˜์—ฌ ๊ณ ์„ฑ๋Šฅ ์Šฌ๋Ÿฌ๋ฆฌ์˜ ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์••์ถ•๊ฐ•๋„ ๊ฐ์†Œ๋Š” ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์™€ ๋น„๋ก€์ ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์ด๋Š” ๊ฐ•์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋œ SIFRCC์˜ ํœจ์„ฑ๋Šฅ์—๋„ ๋‹ค์†Œ ์˜ํ–ฅ์„ ๋ฏธ์น  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

3.2 ํœจ๊ฑฐ๋™ ํŠน์„ฑ

Fig. 8์€ ๋…ธ์ถœ์˜จ๋„ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ๋ณ€์ˆ˜๋ณ„ ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์„ ๋น„๊ตํ•˜๊ณ  ์žˆ๋‹ค.

Fig. 8. Load-mid span deflection curves with respect to exposure temperature

../../Resources/kci/JKCI.2019.31.2.139/fig8.png

์ฒซ ๋ฒˆ์งธ ํ•˜์ค‘ ํ”ผํฌ์ ์—์„œ์˜ ์ฒ˜์ง์€ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์˜ ๊ฒฝ์šฐ ์‹(2)์— ์˜ํ•ด ์•ฝ 0.5 mm๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ฐ 400 ยฐC ๋ณ€์ˆ˜์—์„œ๋Š” ์•ฝ 0.5 mm, ๋ฐ 0.4 mm๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค.

๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ SIFRCC ํœจ๊ฑฐ๋™ ํŠน์„ฑ์€ ์ดˆ๊ธฐ๊ท ์—ด ๋ฐœ์ƒ(์ฒซ ๋ฒˆ์งธ ํ•˜์ค‘ ํ”ผํฌ์ ์—์„œ์˜ ์ฒ˜์ง) ์ดํ›„ ํ•˜์ค‘์ด ์ง€์†์ ์œผ๋กœ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ๊ณ ํ˜ผ์ž…์˜ ๊ฐ•์„ฌ์œ ๊ฐ€ ์ดˆ๊ธฐ๊ท ์—ด ๋ฐœ์ƒ์—๋„ ๊ฐ€๊ต์—ญํ• (bridging effect)์„ ํ•จ์œผ๋กœ์จ ์ถฉ๋ถ„ํ•œ ์—๋„ˆ์ง€์˜ ํก์ˆ˜๋ฅผ ํ†ตํ•˜์—ฌ ํ•˜์ค‘์ด ์ง€์†์ ์œผ๋กœ ์ฆ๊ฐ€ํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋˜ํ•œ ๊ณ ์˜จ๋…ธ์ถœ์„ ํ•˜์ง€ ์•Š์€ normal condition์—์„œ์˜ ๋ณ€์ˆ˜๋Š” ์ฒ˜์ง 3 mm ์ˆ˜์ค€์—์„œ ์ตœ๋Œ€ํ•˜์ค‘ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ์ด๋Š” ์ตœ๋Œ€ํ•˜์ค‘ ์ดํ›„์—๋„ ์ถฉ๋ถ„ํ•œ ์—๋„ˆ์ง€๋ฅผ ํก์ˆ˜ํ•˜์—ฌ ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด๊ฐ€ ์ถฉ๊ฒฉ, ํญ๋ฐœ ๋“ฑ๊ณผ ๊ฐ™์€ ๊ทนํ•œํ•˜์ค‘์— ์ €ํ•ญํ•  ์ˆ˜ ์žˆ๋„๋ก ์—ญํ•™์  ์„ฑ์งˆ์ด ๊ฐœ์„ ๋œ ๊ฒƒ์„ ์˜๋ฏธํ•œ๋‹ค. ๋˜ํ•œ ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ฐ 400 ยฐC์— ๋…ธ์ถœํ•œ ๋ณ€์ˆ˜์˜ ๊ฒฝ์šฐ, ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์™€ ๋™์ผํ•˜๊ฒŒ ์ดˆ๊ธฐ๊ท ์—ด ๋ฐœ์ƒ ์ดํ›„์—๋„ ๊ณ ํ˜ผ์ž…์˜ ๊ฐ•์„ฌ์œ ๋กœ ์ธํ•˜์—ฌ ์ง€์†์ ์œผ๋กœ ํ•˜์ค‘์ด ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์—ˆ๋‹ค. ํ•˜์ง€๋งŒ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์—์„œ๋Š” 3 mm ์ „ํ›„์—์„œ ์ตœ๋Œ€ํ•˜์ค‘ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์ดํ›„ ํ•˜์ค‘์ด ๊ฐ์†Œํ•œ ๋ฐ˜๋ฉด, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ฐ 400 ยฐC ๋ณ€์ˆ˜์—์„œ๋Š” 6~7 mm ์ˆ˜์ค€์—์„œ ์ตœ๋Œ€ํ•˜์ค‘ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ์ดํ›„ ํ•˜์ค‘์ด ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. ์ด๋Š” ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์—์„œ๋Š” ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ๋†’์€ ๊ฐ•๋„์™€ ๊ฐ•์„ฌ์œ ์˜ ํŠน์ง•(5D)์ธ ์•ต์ปค๋ง ํšจ๊ณผ๋กœ ์ธํ•œ ๋ถ€์ฐฉ์„ฑ๋Šฅ ์ฆ์ง„์ด ํŒŒ๊ดด๋ฉด์—์„œ Fig. 9์™€ ๊ฐ™์ด ์„ฌ์œ ๊ฐ€ ํŒŒ๋‹จ๋˜๋Š” ํŒŒ๊ดด์–‘์ƒ์ด ๋‚˜ํƒ€๋‚˜ ์ดˆ๊ธฐ์— ํ•˜์ค‘ ์ฆ๊ฐ€๊ฐ€ ๊ธ‰๊ฒฉํžˆ ์ด๋ฃจ์–ด์ง„ ๊ฒƒ์œผ๋กœ ์‚ฌ๋ฃŒ๋œ๋‹ค. ๋ฐ˜๋ฉด ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ฐ 400 ยฐC ๋ณ€์ˆ˜์—์„œ๋Š” ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ๊ฐ•๋„ ๊ฐ์†Œ, ๋‚ด๋ถ€ ์ˆ˜๋ถ„์˜ ์ฆ๋ฐœ ๋“ฑ๊ณผ ๊ฐ™์€ ๋ฌผ๋ฆฌโ€งํ™”ํ•™์  ๋ณ€ํ™”๋กœ ์ธํ•˜์—ฌ ๊ฐ•์„ฌ์œ  ๊ณ„๋ฉด์—์„œ์˜ ๋ถ€์ฐฉ์„ฑ๋Šฅ์ด ์ €ํ•˜ํ–ˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด๋Š” ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์—์„œ๋Š” ํŒŒ๊ดด๋ฉด์—์„œ์˜ ์„ฌ์œ ๊ฐ€ ํŒŒ๋‹จ๋˜์—ˆ์œผ๋‚˜, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ฐ 400 ยฐC์˜ ๋ณ€์ˆ˜์—์„œ๋Š” Fig. 10๊ณผ ๊ฐ™์ด ํŒŒ๊ดด๋ฉด์—์„œ์˜ ํŒŒ๊ดด์–‘์ƒ์ด ์„ฌ์œ ํŒŒ๋‹จ์ด ์•„๋‹Œ ๋ถ€์ฐฉ๊ฐ•๋„ ์ €ํ•˜๋กœ ์ธํ•œ ์„ฌ์œ  ๋ฝ‘ํž˜ ํ˜„์ƒ์ด ๋ฐœ์ƒํ•œ ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์—ˆ๋‹ค. ์ด๋Ÿฌํ•œ ์ด์œ ๋กœ ์ธํ•ด ์ดˆ๊ธฐ๊ท ์—ด ๋ฐœ์ƒ ์ดํ›„์—๋„ ์ง€์†์ ์œผ๋กœ ํ•˜์ค‘์˜ ์ฆ๊ฐ€๊ฐ€ ์ด๋ฃจ์–ด์กŒ์œผ๋ฉฐ, ์ดˆ๊ธฐ์˜ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์€ ๊ณ ์˜จ๋…ธ์ถœ์„ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๋ณด๋‹ค ์ž‘์•˜์œผ๋‚˜, ์ตœ๋Œ€ํ•˜์ค‘ ์ดํ›„์—์„œ์˜ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์€ ์šฐ์ˆ˜ํ•œ ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค

Fig. 9. Failure mode at normal condition

../../Resources/kci/JKCI.2019.31.2.139/fig9.png

Fig. 10. Failure mode at 400 ยฐC

../../Resources/kci/JKCI.2019.31.2.139/fig10.png

Fig. 11์—์„œ Fig. 13์€ ๋…ธ์ถœ ์˜จ๋„์— ๋”ฐ๋ฅธ ๋ณ€์ˆ˜๋ณ„ ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค. ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์˜ ์‹คํ—˜๊ฒฐ๊ณผ, ํ‰๊ท  ์ตœ๋Œ€ํ•˜์ค‘ 152.3 kN(45.7 MPa) ์ˆ˜์ค€์˜ ๋งค์šฐ ์šฐ์ˆ˜ํ•œ ํœจ์ €ํ•ญ ์„ฑ๋Šฅ์„ ๊ฐ–๋Š” ๊ฒƒ์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. ๋˜ํ•œ ์ตœ๋Œ€ํ•˜์ค‘์—์„œ์˜ ์ฒ˜์ง์€ 3 mm ์ˆ˜์ค€์œผ๋กœ ๋ถ„์„๋˜์—ˆ์œผ๋ฉฐ, ์ตœ๋Œ€๊ฐ•๋„ ๋„๋‹ฌ ์ดํ›„ ์ž”๋ฅ˜๊ฐ•๋„๊ฐ€ ์ง€์†๋˜๋Š” ํŠน์ง•์„ ๋ณด์˜€๊ณ , ์ด๋Š” ์ž”๋ฅ˜๊ฐ•๋„ ํ™•๋ณด๋ฅผ ํ†ตํ•ด ์ถฉ๋Œ ๋ฐ ํญ๋ฐœ์‚ฌ๊ณ  ์ดํ›„์—๋„ ๊ตฌ์กฐ๋ฌผ์˜ ์ทจ์„ฑํŒŒ๊ดด์— ๋Œ€ํ•œ ๋ถ•๊ดด๋ฅผ ๋ฐฉ์ง€ํ•  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜์˜ ์‹คํ—˜๊ฒฐ๊ณผ, ํ‰๊ท  ์ตœ๋Œ€ํ•˜์ค‘ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์˜ ํ‰๊ท  ์ตœ๋Œ€ํ•˜์ค‘๋ณด๋‹ค 5.3% ๊ฐ์†Œํ•œ 144.2 kN(43.3 MPa) ์ˆ˜์ค€์œผ๋กœ ์šฐ์ˆ˜ํ•œ ํœจ์ €ํ•ญ ์„ฑ๋Šฅ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๋˜ํ•œ Fig. 12์™€ ๊ฐ™์ด ์ตœ๋Œ€ํ•˜์ค‘์—์„œ์˜ ์ฒ˜์ง์ด ์•ฝ 6~7 mm ์ˆ˜์ค€์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. ์ด๋Š” ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ๊ฐ•๋„ ๊ฐ์†Œ ๋ฐ ๋‚ด๋ถ€ ํ™”ํ•™์  ๋ณ€ํ™”๋กœ ์ธํ•˜์—ฌ ๊ฐ•์„ฌ์œ ์™€์˜ ๊ณ„๋ฉด ๋ถ€์ฐฉ์„ฑ๋Šฅ ์ €ํ•˜๋กœ ์ธํ•˜์—ฌ ์„ฌ์œ ์˜ ๋ฝ‘ํž˜ ํ˜„์ƒ์ด ๋ฐœ์ƒํ•˜์—ฌ SIFRCC ์ž์ฒด์˜ ์ธ์„ฑ๋Šฅ๋ ฅ์— ์˜ํ–ฅ์„ ๋ฏธ์นœ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ดˆ๊ธฐ ์ธ์„ฑ๋Šฅ๋ ฅ์˜ ๊ฒฝ์šฐ, ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๊ฐ€ ์„ฌ์œ ์™€ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค ์‚ฌ์ด์˜ ๊ณ„๋ฉด ๋ถ€์ฐฉ์„ฑ๋Šฅ์ด ์šฐ์ˆ˜ํ•˜์—ฌ ๋†’์€ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์„ ๋‚˜ํƒ€๋‚ธ ๋ฐ˜๋ฉด, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜๊ฐ€ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๋ณด๋‹ค ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ ์ธก๋ฉด์—์„œ๋Š” ์šฐ์ˆ˜ํ•œ ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์—ˆ๋‹ค.

๊ณ ์˜จ๋…ธ์ถœ 400 ยฐC ๋ณ€์ˆ˜์˜ ์‹คํ—˜๊ฒฐ๊ณผ, ํ‰๊ท  ์ตœ๋Œ€ํ•˜์ค‘ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์˜ ํ‰๊ท  ์ตœ๋Œ€ํ•˜์ค‘๋ณด๋‹ค 29.6%, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜๋ณด๋‹ค 25.7% ๊ฐ์†Œํ•œ 107.2 kN(32.2 MPa) ์ˆ˜์ค€์˜ ํœจ์ €ํ•ญ ์„ฑ๋Šฅ์„ ๊ฐ–๋Š” ๊ฒƒ์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. Fig. 13๊ณผ ๊ฐ™์ด ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ์ตœ๋Œ€ํ•˜์ค‘์—์„œ์˜ ์ฒ˜์ง์€ ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜์˜ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„์Šทํ•œ 6 mm ์ „ํ›„ ์ˆ˜์ค€์œผ๋กœ ๋ถ„์„๋˜์—ˆ๋‹ค. ๋˜ํ•œ ํ•˜์ค‘-์ฒ˜์ง ๊ฑฐ๋™ ํŠน์„ฑ์€ Fig. 12์˜ ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜์™€ ๋น„์Šทํ•œ ํ•˜์ค‘-์ฒ˜์ง ๊ฑฐ๋™ ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ์ง€๋งŒ, ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ ์ธก๋ฉด์—์„œ๋Š” ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜์— ๋‹ค์†Œ ๋ชป ๋ฏธ์น˜๋Š” ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ๊ณ ์˜จ๋…ธ์ถœ๋กœ ์ธํ•œ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ๊ฐ•๋„ ์ €ํ•˜ ๋ฐ ํ™”ํ•™์  ๋ฌผ์„ฑ๋ณ€ํ™”๋กœ ์ธํ•˜์—ฌ ๊ฐ•์„ฌ์œ ์™€์˜ ๊ณ„๋ฉด์—์„œ ๋ถ€์ฐฉ์„ฑ๋Šฅ ์ €ํ•˜๊ฐ€ ์›์ธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 11. Load-mid span deflection curves at normal condition

../../Resources/kci/JKCI.2019.31.2.139/fig11.png

Fig. 12. Load-mid span deflection curves at 200 ยฐC

../../Resources/kci/JKCI.2019.31.2.139/fig12.png

Fig. 13. Load-mid span deflection curves at 400 ยฐC

../../Resources/kci/JKCI.2019.31.2.139/fig13.png

3.3 ํœจ๊ฐ•๋„ ๋ฐ ์ธ์„ฑ

Fig. 14๋Š” ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ํœจ๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ๋น„๊ตํ•˜๊ณ  ์žˆ๋‹ค. ๊ณ ์˜จ๋…ธ์ถœ์„ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์˜ ๊ฒฝ์šฐ, ์ตœ๋Œ€ ํœจ๊ฐ•๋„ 50 MPa ์ˆ˜์ค€์˜ ์šฐ์ˆ˜ํ•œ ํœจ๊ฐ•๋„ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ์••์ถ•๊ฐ•๋„์˜ ์•ฝ 60% ์ด์ƒ์— ํ•ด๋‹นํ•˜๋Š” ๊ฐ•๋„ ์ˆ˜์ค€์œผ๋กœ ๋†’์€ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ๋กœ ์ธํ•˜์—ฌ ์ผ๋ฐ˜ ์„ฌ์œ ๋ณด๊ฐ• ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ๋‹ฌ๋ฆฌ ํœจ์— ๋Œ€ํ•œ ์ €ํ•ญ์„ฑ์ด ์šฐ์ˆ˜ํ•œ ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜์˜ ์ตœ๋Œ€ ํœจ๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ, 46.2 MPa ์ˆ˜์ค€์œผ๋กœ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๋ณด๋‹ค ๋‹ค์†Œ ๊ฐ์†Œํ•˜์˜€์œผ๋‚˜ ์ด ์—ญ์‹œ ๋งค์šฐ ์šฐ์ˆ˜ํ•œ ํœจ๊ฐ•๋„ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋ฐ˜๋ฉด ๊ณ ์˜จ๋…ธ์ถœ 400 ยฐC ๋ณ€์ˆ˜์˜ ํœจ๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ, 35.9 MPa ์ˆ˜์ค€์œผ๋กœ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜ ๋ฐ ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜๋ณด๋‹ค ์•ฝ 29% ๋ฐ 26% ๊ฐ์†Œํ•œ ํœจ๊ฐ•๋„ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ๋…ธ์ถœ์˜จ๋„์˜ ์ƒ์Šน์œผ๋กœ ์ธํ•˜์—ฌ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ๊ฐ•๋„ ์ €ํ•˜์— ๊ธฐ์ธํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. Table 5๋Š” ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ๋ณ€์ˆ˜๋ณ„ ์ตœ๋Œ€ ํœจ๊ฐ•๋„ ๋ฐ ์‹œํ—˜์ฒด ์ธ์„ฑ ์‚ฐ์ •๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค.

Fig. 14. Tests result of flexural strength with respect to exposure temperature

../../Resources/kci/JKCI.2019.31.2.139/fig14.png

Table 5. Flexural strength and specimen toughness

Variables

(exposure temperature)

Flexural strength

(MPa)

Specimen toughness

(Nโ€งm)

Average of flexural strength

(MPa)

Average of specimen toughness

(Nโ€งm)

Normal

44.9

50.4

41.8

1,243.2

1,567.3

1,216.1

45.7

1,342.9

200 ยฐC

40.4

46.2

1,471.8

1,582.2

43.3

1,527.0

400 ยฐC

28.4

35.9

1,057.3

1,221.8

32.2

1,139.6

์ด ์—ฐ๊ตฌ์—์„œ๋Š” 2.4์ ˆ ์‹คํ—˜๋ฐฉ๋ฒ•์— ์„ค๋ช…ํ–ˆ๋“ฏ์ด ASTM C 1609์—์„œ ์ œ์‹œํ•˜๋Š” ์‹œํ—˜์ฒด ์ธ์„ฑ์„ ๊ณ„์‚ฐํ•˜์˜€์œผ๋‚˜, SIFRCC ํœจ๊ฑฐ๋™ ํŠน์„ฑ์ƒ ์ง€๊ฐ„๊ฑฐ๋ฆฌ L์˜ 1/150(2 mm)๊นŒ์ง€์˜ ๋ฉด์ ์œผ๋กœ ์ •์˜๋˜๋Š” ๊ฒƒ์— ์ ํ•ฉํ•˜์ง€ ์•Š์œผ๋ฏ€๋กœ ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์„ ์ƒ๋Œ€์ ์œผ๋กœ ๋น„๊ตํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์—์„œ ์ฒ˜์ง 15 mm๊นŒ์ง€์˜ ๋ฉด์ ์œผ๋กœ ๋Œ€์ฒดํ•˜์—ฌ ๋ณ€์ˆ˜๋ณ„ ์ธ์„ฑ ํŠน์„ฑ์„ ๋น„๊ตํ•˜์˜€๋‹ค.

Fig. 15๋Š” ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ์‹œํ—˜์ฒด ์ธ์„ฑ ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ๋น„๊ตํ•˜๊ณ  ์žˆ๋‹ค. ์ฒ˜์ง 15 mm๊นŒ์ง€์˜ ์‹œํ—˜์ฒด ์ธ์„ฑ ์‹คํ—˜๊ฒฐ๊ณผ, ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์˜ ์ธ์„ฑ์€ 1,342.9 Nโ€งm๋ฅผ ๋‚˜ํƒ€๋‚ธ ๋ฐ˜๋ฉด, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜์˜ ์ธ์„ฑ์€ ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ์ธ์„ฑ๋ณด๋‹ค 12% ์ฆ๊ฐ€ํ•œ 1,527.0 Nโ€งm ์ˆ˜์ค€์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ํœจ๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋ฐ˜๋Œ€๋กœ ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC์— ๋”ฐ๋ฅธ ์ธ์„ฑ ๊ฐ’์ด ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๋ณด๋‹ค ๋” ์šฐ์ˆ˜ํ•œ ์ด์œ ๋Š” ๊ฐ•์„ฌ์œ ์™€ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค ์‚ฌ์ด์˜ ๊ณ„๋ฉด ๋ถ€์ฐฉ์„ฑ๋Šฅ์œผ๋กœ ์ธํ•˜์—ฌ ๊ฐ•์„ฌ์œ ์˜ ํŒŒ๋‹จ ๋˜๋Š” ๋ฝ‘ํž˜ํ˜„์ƒ์— ๊ธฐ์ธํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 15. Tests result of specimen toughness with respect to exposure temperature

../../Resources/kci/JKCI.2019.31.2.139/fig15.png

๋˜ํ•œ ๊ณ ์˜จ๋…ธ์ถœ 400 ยฐC ๋ณ€์ˆ˜์˜ ์‹œํ—˜์ฒด ์ธ์„ฑ ์‹คํ—˜๊ฒฐ๊ณผ, ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜ ๋ฐ ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜๋ณด๋‹ค ์•ฝ 12% ๋ฐ 15% ๊ฐ์†Œํ•œ 1,139.6 Nโ€งm ์ˆ˜์ค€์˜ ์ธ์„ฑ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ํœจ๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ์—์„œ์˜ ๊ฐ์†Œ์œจ(26~29%)๋ณด๋‹ค ๋” ์ž‘์€ ๊ฐ์†Œ์œจ์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC๋ณด๋‹ค ์ƒ๋Œ€์ ์œผ๋กœ ๋†’์€ ๊ณ ์˜จ๋…ธ์ถœ 400 ยฐC๋กœ ์ธํ•˜์—ฌ ์Šฌ๋Ÿฌ๋ฆฌ ๋ฐ ๊ฐ•์„ฌ์œ ์˜ ์„ฑ๋Šฅ์ €ํ•˜๋กœ ์ธํ•˜์—ฌ ์ธ์„ฑ์ด ๊ฐ์†Œํ•œ ๊ฒƒ์œผ๋กœ ์‚ฌ๋ฃŒ๋œ๋‹ค. ๋˜ํ•œ ์ตœ๋Œ€ํ•˜์ค‘ ์ดํ›„์˜ ์ž”๋ฅ˜๊ฐ•๋„ ํ™•๋ณด๊ฐ€ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ ํ–ฅ์ƒ์— ์˜ํ–ฅ์„ ๋ฏธ์นœ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

4. ๊ฒฐ ๋ก 

์ด ์—ฐ๊ตฌ๋Š” ์ถฉ๊ฒฉ ๋˜๋Š” ํญ๋ฐœ๊ณผ ๊ฐ™์ด ์ž‘์šฉ์‹œ๊ฐ„์ด ๋งค์šฐ ์งง์€ ํ•˜์ค‘์— ๋Œ€ํ•œ ๋‚ด์ถฉ๊ฒฉ์„ฑ๋Šฅ ์ฆ๋Œ€๋ฅผ ์œ„ํ•˜์—ฌ ๊ฐœ๋ฐœํ•œ SIFRCC์˜ ๊ณ ์˜จ๋…ธ์ถœ ์˜จ๋„ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ํœจ๊ฑฐ๋™ ํŠน์„ฑ์— ๋Œ€ํ•œ ์‹คํ—˜์  ์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ด์— ๋”ฐ๋ฅธ ๊ฒฐ๋ก ์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

1) ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ์••์ถ•๊ฐ•๋„๋Š” ๋…ธ์ถœ์˜จ๋„ ์ฆ๊ฐ€์— ๋”ฐ๋ผ ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ์ด๋Š” ๊ณ ์˜จ๋…ธ์ถœ๋กœ ์ธํ•˜์—ฌ ์‹œ๋ฉ˜ํŠธ ํŽ˜์ด์ŠคํŠธ์—์„œ ์ˆ˜๋ถ„์ด ๋น ์ ธ๋‚˜์™€ ๊ฑด์กฐ์ˆ˜์ถ•์— ์˜ํ•ด ๊ฐ•๋„๊ฐ€ ์ €ํ•˜๋œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

2) ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ์ค‘๋Ÿ‰์†์‹ค์€ ์ตœ๋Œ€ 18% ์ˆ˜์ค€์ด์—ˆ์œผ๋ฉฐ, ์ด๋Š” ์นผ์Š˜์‹ค๋ฆฌ์ผ€์ดํŠธ ์ˆ˜ํ™”์ƒ์„ฑ๋ฌผ์ด 350 ยฐC ์ˆ˜์ค€์—์„œ 20%์˜ ํ•จ์œ ์ˆ˜๋ถ„์„ ์†์‹คํ•œ๋‹ค๋Š” ์„ ํ–‰์—ฐ๊ตฌ ์ž๋ฃŒ์™€ ๋น„์Šทํ•œ ์ˆ˜์ค€์˜ ์ˆ˜์น˜์ธ ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์—ˆ๋‹ค.

3) ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์—์„œ๋Š” ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ๋†’์€ ๊ฐ•๋„์™€ ๊ฐ•์„ฌ์œ ์˜ ํŠน์ง•(5D)์ธ ์•ต์ปค๋ง ํšจ๊ณผ๋กœ ์ธํ•œ ๋ถ€์ฐฉ์„ฑ๋Šฅ ์ฆ์ง„์ด ํŒŒ๊ดด๋ฉด์—์„œ ์„ฌ์œ ๊ฐ€ ํŒŒ๋‹จ๋˜๋Š” ํŒŒ๊ดด์–‘์ƒ์ด ๋‚˜ํƒ€๋‚˜ ์ดˆ๊ธฐ์— ํ•˜์ค‘ ์ฆ๊ฐ€๊ฐ€ ๊ธ‰๊ฒฉํžˆ ์ด๋ฃจ์–ด์ง„ ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๋ฐ˜๋ฉด, ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ฐ 400 ยฐC ๋ณ€์ˆ˜์—์„œ๋Š” ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ์Šฌ๋Ÿฌ๋ฆฌ ๋งคํŠธ๋ฆญ์Šค์˜ ๊ฐ•๋„ ๊ฐ์†Œ, ๋‚ด๋ถ€ ์ˆ˜๋ถ„์˜ ์ฆ๋ฐœ ๋“ฑ๊ณผ ๊ฐ™์€ ๋ฌผ๋ฆฌโ€งํ™”ํ•™์  ๋ณ€ํ™”๋กœ ์ธํ•˜์—ฌ ๊ฐ•์„ฌ์œ  ๊ณ„๋ฉด์—์„œ์˜ ๋ถ€์ฐฉ์„ฑ๋Šฅ์ด ์ €ํ•˜ํ•˜์—ฌ ์„ฌ์œ  ๋ฝ‘ํž˜ ํ˜„์ƒ์ด ๋ฐœ์ƒํ•˜์˜€๋‹ค. ํ•˜์ง€๋งŒ ์ฒ˜์ง 0.4~0.5 mm์—์„œ์˜ ์ดˆ๊ธฐ๊ท ์—ด ๋ฐœ์ƒ ์ดํ›„์—๋„ ์ง€์†์ ์œผ๋กœ ํ•˜์ค‘์˜ ์ฆ๊ฐ€๊ฐ€ ์ด๋ฃจ์–ด์กŒ์œผ๋ฉฐ, ์ดˆ๊ธฐ์˜ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์€ ๊ณ ์˜จ๋…ธ์ถœ์„ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๋ณด๋‹ค ์ž‘์•˜์œผ๋‚˜, 1,000 Nโ€งm ์ด์ƒ์˜ ์šฐ์ˆ˜ํ•œ ์—๋„ˆ์ง€ ํก์ˆ˜๋Šฅ๋ ฅ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค.

4) ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ ํœจ๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ, ๊ณ ์˜จ๋…ธ์ถœ์„ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜์˜ ๊ฒฝ์šฐ ์ตœ๋Œ€ 50 MPa์˜ ์šฐ์ˆ˜ํ•œ ํœจ๊ฐ•๋„๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ์ด๋Š” ์••์ถ•๊ฐ•๋„์˜ ์•ฝ 60% ์ด์ƒ์— ํ•ด๋‹นํ•˜๋Š” ๊ฐ•๋„ ์ˆ˜์ค€์œผ๋กœ ๋†’์€ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ๋กœ ์ธํ•˜์—ฌ ์ผ๋ฐ˜ ์„ฌ์œ ๋ณด๊ฐ• ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ๋‹ฌ๋ฆฌ ํœจ์— ๋Œ€ํ•œ ์ €ํ•ญ์„ฑ์ด ์šฐ์ˆ˜ํ•œ ๊ฒƒ์„ ์•Œ ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜์˜ ์ตœ๋Œ€ ํœจ๊ฐ•๋„ ์‹คํ—˜๊ฒฐ๊ณผ, ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜๋ณด๋‹ค ๋‹ค์†Œ ๊ฐ์†Œํ•˜์˜€์œผ๋‚˜ ๋น„์Šทํ•œ ์ˆ˜์ค€์œผ๋กœ ๊ณ ์˜จ๋…ธ์ถœ ํ›„์—๋„ ์šฐ์ˆ˜ํ•œ ํœจ๊ฐ•๋„ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ธ ๋ฐ˜๋ฉด, ๊ณ ์˜จ๋…ธ์ถœ 400 ยฐC ๋ณ€์ˆ˜์˜ ํœจ๊ฐ•๋„๋Š” ๊ณ ์˜จ๋…ธ์ถœ ํ•˜์ง€ ์•Š์€ ๋ณ€์ˆ˜ ๋ฐ ๊ณ ์˜จ๋…ธ์ถœ 200 ยฐC ๋ณ€์ˆ˜๋ณด๋‹ค ์•ฝ 29% ๋ฐ 26% ๊ฐ์†Œํ•œ ํœจ๊ฐ•๋„ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

5) ๊ณ ์˜จ๋…ธ์ถœ์— ๋”ฐ๋ฅธ SIFRCC์˜ ํœจ ํŒŒ๊ดด ์‹œ, ์ฒ˜์ง 0.4~0.5 mm์—์„œ์˜ ์ดˆ๊ธฐ๊ท ์—ด ๋ฐœ์ƒ ์ดํ›„์—๋„ ๋†’์€ ์„ฌ์œ ํ˜ผ์ž…๋ฅ ๋กœ ์ธํ•˜์—ฌ ํ•˜์ค‘์ด ์ง€์†์ ์œผ๋กœ ์ฆ๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ๊ณ ํ˜ผ์ž…์˜ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…์œผ๋กœ ์ธํ•˜์—ฌ ์ตœ๋Œ€ ๊ฐ•๋„ ์ดํ›„์—๋„ ์ถฉ๋ถ„ํ•œ ์ž”๋ฅ˜๊ฐ•๋„๋ฅผ ํ™•๋ณดํ•˜์˜€๋‹ค. ์ด๋Ÿฌํ•œ ์ž”๋ฅ˜๊ฐ•๋„ ํ™•๋ณด๋ฅผ ํ†ตํ•ด ์ถฉ๊ฒฉ, ํญ๋ฐœ๊ณผ ๊ฐ™์€ ์ž‘์šฉ์‹œ๊ฐ„์ด ์งง์€ ๊ทนํ•œํ•˜์ค‘์— ๋Œ€ํ•œ ์ €ํ•ญ์„ฑ๋Šฅ ๋ฐ ๊ตฌ์กฐ๋ฌผ์˜ ์ทจ์„ฑํŒŒ๊ดด๋ฅผ ์–ต์ œํ•  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

์ด ์—ฐ๊ตฌ๋Š” ๊ตญํ† ๊ตํ†ต๋ถ€ ๊ฑด์„ค๊ธฐ์ˆ ์—ฐ๊ตฌ์‚ฌ์—…(๊ณผ์ œ๋ฒˆํ˜ธ:17SCIP- B128706-01)๊ณผ ๊ตญํ† ๊ตํ†ต๋ถ€ ๊ฑด์„ค๊ธฐ์ˆ ์—ฐ๊ตฌ์‚ฌ์—…(๊ณผ์ œ๋ฒˆํ˜ธ: 18SCIP-B146646-01)์˜ ์—ฐ๊ตฌ๋น„ ์ง€์›์— ์˜ํ•ด ์ˆ˜ํ–‰๋˜์—ˆ์Šต๋‹ˆ๋‹ค.

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