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Journal of the Korea Concrete Institute

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




๊ฑด์กฐ์ˆ˜์ถ•๊ท ์—ด์‹œํ—˜, ํŒฝ์ฐฝ์žฌ, ๊ณ ์„ฑ๋Šฅ ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด, ๋ง-ํ…Œ์ŠคํŠธ, ์ˆ˜์ถ•, ์ˆ˜์ถ•์ €๊ฐ์ œ
Drying shrinkage cracking test, Expansive Admixture (EA), High Performance Fiber reinforced Cementitious Composites (HPFRCC), Ring-Test, Shrinkage, Shrinkage Reducing Agent (SRA)

1. ์„œ ๋ก 

์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์˜ค๋žซ๋™์•ˆ ํ˜„๋Œ€์‚ฌํšŒ์˜ ์ธํ”„๋ผ๋ฅผ ๊ตฌ์ถ•ํ•œ ์ฃผ์š” ๊ฑด์„ค์žฌ๋ฃŒ๋กœ์„œ ๊ฒฝ์ œ์„ฑ ๋ฐ ์—ญํ•™์  ์„ฑ๋Šฅ, ๋‚ด๊ตฌ์„ฑ์ด ์šฐ์ˆ˜ํ•˜์—ฌ ์‚ฌ ํšŒ๊ธฐ๋ฐ˜์‹œ์„ค๋ฌผ์— ๊ฐ€์žฅ ๋ณดํŽธ์ ์œผ๋กœ ์‚ฌ์šฉ๋˜์–ด์˜จ ๊ฑด์„ค์žฌ๋ฃŒ์ด๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ์ค‘๋Ÿ‰๋Œ€๋น„ ๋‚ฎ์€ ๊ฐ•๋„ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ด๊ณ , ์ทจ์„ฑ์ ์œผ๋กœ ํŒŒ ๊ดดํ•˜๋Š” ๋“ฑ ์—ฌ๋Ÿฌ ๋ฌธ์ œ์  ๋˜ํ•œ ๋‚ดํฌํ•˜๊ณ  ์žˆ๋‹ค.

๊ทธ๋Ÿฌ๋‚˜ ์ตœ๊ทผ์—๋Š” ์ด๋Ÿฌํ•œ ํ•œ๊ณ„์ ์„ ๊ทน๋ณตํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋ฌผ-๊ฒฐ ํ•ฉ์žฌ๋น„ (W/B)๋ฅผ ๋‚ฎ์ถ”๊ณ , ํ˜ผํ™”์žฌ๋ฃŒ์™€ ๊ฐ•์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•˜์—ฌ ๊ฐ• ๋„์™€ ์ธ์„ฑ์„ ๋ณตํ•ฉ์ ์œผ๋กœ ํ–ฅ์ƒ์‹œํ‚จ ๊ณ ์„ฑ๋Šฅ ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด (High Performance Fiber Reinforced Cement Composites, ์ดํ•˜ HPFRCC)๊ฐ€ ๊ฐœ๋ฐœ๋˜์—ˆ์œผ๋ฉฐ, ์‹ค์šฉํ™”๋ฅผ ์œ„ํ•œ ๊ด€๋ จ ์—ฐ๊ตฌ๊ฐ€ ํ™œ๋ฐœ ํžˆ ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค (Kim et al., 2008; Kamen et al., 2008; Graybeal et al., 2008).

HPFRCC๋Š” ๋ฌผ-๊ฒฐํ•ฉ์žฌ๋น„ (W/B)๊ฐ€ 20%๋กœ ์ƒ๋‹นํžˆ ๋‚ฎ๊ณ  ๊ตต ์€ ๊ณจ์žฌ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š์œผ๋ฉฐ, ๊ณ ๋ถ„๋ง ํ˜ผํ™”์žฌ๋ฃŒ๋ฅผ ํ˜ผ์ž…ํ•˜๊ธฐ ๋•Œ ๋ฌธ์— ์ž๊ธฐ์ˆ˜์ถ•์ด ์ƒ๋‹นํžˆ ํฌ๊ฒŒ ๋ฐœ์ƒํ•œ๋‹ค. ํŠนํžˆ, HPFRCC์™€ ๊ฐ™์ด W/B๊ฐ€ 20% ์ดํ•˜์ธ ์ดˆ๊ณ ๊ฐ•๋„ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฒฝ์šฐ์—๋Š” ์žฌ ๋ น 60์ผ์—์„œ ์•ฝ 800ฮผฮต ์ด์ƒ์˜ ์ž๊ธฐ์ˆ˜์ถ•์ด ๋ฐœ์ƒํ•˜๊ณ , ๋งŒ์•ฝ ์™ธ๋ถ€ ๊ฑฐํ‘ธ์ง‘ ๋ฐ ๋‚ด๋ถ€ ๋ณด๊ฐ•๊ทผ์— ์˜ํ•ด ๊ตฌ์†๋  ๊ฒฝ์šฐ ์ˆ˜์ถ•๊ท ์—ด์˜ ์œ„ํ—˜์„ฑ์ด ์ƒ๋‹นํžˆ ํฌ๋‹ค (Yoo et al., 2011). ์ด๋Ÿฌํ•œ ์ˆ˜์ถ•๊ท ์—ด ์€ ๊ตฌ์กฐ๋ฌผ์˜ ๋‚ด๊ตฌ์ˆ˜๋ช… ๋ฐ ๊ตฌ์กฐ์  ์„ฑ๋Šฅ์„ ์ €ํ•˜์‹œํ‚ค๊ธฐ ๋•Œ๋ฌธ์— HPFRCC๋ฅผ ์‹ค์ œ ๊ตฌ์กฐ๋ฌผ์— ์ ์šฉํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ์ˆ˜์ถ•๊ฑฐ๋™์— ๋Œ€ํ•œ ์ •ํ™•ํ•œ ์ดํ•ด ๋ฐ ๊ท ์—ด์ €๊ฐ ๋Œ€์ฑ…์— ๊ด€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ๋ฐ˜๋“œ์‹œ ์ˆ˜ํ–‰๋˜์–ด์•ผ ํ•œ๋‹ค.

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ˆ˜์ถ•์„ ์ €๊ฐ์‹œํ‚ค๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ๋Š” ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ CSA๊ณ„ ํŒฝ์ฐฝ์žฌ๋ฅผ ์กฐํ•ฉํ•˜์—ฌ ํ˜ผ์ž…ํ•˜๋Š” ์—ฐ๊ตฌ๊ฐ€ ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค (Maltese et al., 2005). C4A3S ํด๋ง์ปค๋ฅผ ํฌํ•จํ•˜๊ณ  ์žˆ๋Š” ํŒฝ์ฐฝ ์žฌ๋Š” ์ดˆ๊ธฐ์— ๋‹ค๋Ÿ‰์˜ ์—ํŠธ๋ง๊ฐ€์ดํŠธ (ettringite)๋ฅผ ์ƒ์„ฑํ•˜์—ฌ ์ˆ˜ ํ™”๋ฐ˜์‘์„ ์ด‰์ง„์‹œํ‚ค๊ณ  ๋ถ€ํ”ผ๋ฅผ ํŒฝ์ฐฝ์‹œํ‚ค๋ฉฐ, ์ˆ˜์ถ•์ €๊ฐ์ œ๋Š” ์‹œ๋ฉ˜ ํŠธํŽ˜์ด์ŠคํŠธ์˜ ๋‚ด๋ถ€๊ณต๊ทน์ˆ˜์˜ ํ‘œ๋ฉด์žฅ๋ ฅ์„ ๊ฐ์†Œ์‹œ์ผœ ์ˆ˜์ถ•์„ ์ € ๊ฐ์‹œํ‚จ๋‹ค (Bentz, 2006).

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ˆ˜์ถ•์„ ์ธก์ •ํ•˜๊ณ  ํ‰๊ฐ€ํ•˜๋Š” ์ฃผ์š”๋ชฉ์ ์€ ๊ตฌ์กฐ๋ฌผ ์˜ ์ˆ˜์ถ•๊ท ์—ด์„ ์–ต์ œํ•˜์—ฌ ๋‚ด๊ตฌ์ˆ˜๋ช…์„ ์ฆ๊ฐ€์‹œํ‚ค๊ธฐ ์œ„ํ•จ์ด๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ˆ˜์ถ•๊ท ์—ด์€ ์ˆ˜์ถ• ๋ฐœํ˜„์†๋„ ๋ฐ ํฌ๊ธฐ, ๊ตฌ์†๋„, ๊ฐ• ๋„๋ฐœํ˜„, ์‘๋ ฅ์˜ ์ด์™„ ๋“ฑ์— ์˜ํ•ด ์˜ํ–ฅ์„ ๋ฐ›์œผ๋ฉฐ ๋งค์šฐ ๋ณต์žกํ•˜ ๊ธฐ ๋•Œ๋ฌธ์— ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฐ•๋„๋ฐœํ˜„๊ณผ ํฌ๋ฆฌํ”„ ํŠน์„ฑ ๋“ฑ์„ ๊ณ ๋ คํ•  ์ˆ˜ ์—†๋Š” ์ž์œ ์ˆ˜์ถ• ์‹คํ—˜๋งŒ์„ ํ†ตํ•ด์„œ๋Š” ๊ท ์—ด๊ฑฐ๋™์˜ ํ‰๊ฐ€์— ํ•œ ๊ณ„๊ฐ€ ์žˆ๋‹ค (See et al., 2003; Weiss, 1999).

ํŠนํžˆ, W/B๊ฐ€ ๋‚ฎ์€ ๊ณ ๊ฐ•๋„ ์ฝ˜ํฌ๋ฆฌํŠธ์ผ์ˆ˜๋ก ์ถฉ๋ถ„ํ•œ ๊ฐ•๋„๋ฐœ ํ˜„์ด ๋˜๊ธฐ ์ด์ „, ์ฆ‰ ํƒ€์„ค ์ดˆ๊ธฐ์— ์ž๊ธฐ์ˆ˜์ถ•์ด ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚˜๊ณ  ์ทจ์„ฑ์ ์ธ ํŒŒ๊ดด๊ฑฐ๋™์„ ๋ณด์ด๊ธฐ ๋•Œ๋ฌธ์— ๋ง-ํ…Œ์ŠคํŠธ (Ring-test)์™€ ๊ฑด์กฐ์ˆ˜์ถ• ๊ท ์—ด์‹คํ—˜ (KS F 2959) ๊ณผ ๊ฐ™์€ ๊ตฌ์†์ˆ˜์ถ•์— ๋Œ€ํ•œ ์‹คํ—˜์—ฐ๊ตฌ๊ฐ€ ๋ฐ˜๋“œ์‹œ ์ˆ˜ํ–‰๋˜์–ด์•ผ ํ•œ๋‹ค (Hossain and Weiss, 2004; See et al., 2003; Li et al., 1999).

๊ทธ๋Ÿฌ๋ฏ€๋กœ ์ด ์—ฐ๊ตฌ์—์„œ๋Š” HPFRCC์˜ ์ˆ˜์ถ•์„ ํšจ์œจ์ ์œผ๋กœ ์ €๊ฐ์‹œํ‚ฌ ์ˆ˜ ์žˆ๋Š” ๋ฐฐํ•ฉ์„ ์ฐพ๊ณ  ์ด๋ฅผ ๊ฒ€์ฆํ•˜๊ธฐ ์œ„ํ•ด ์ˆ˜์ถ•์ €๊ฐ ์ œ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ ์—ญํ•™์  ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜์˜€๊ณ  ๊ตฌ ์†์ˆ˜์ถ• ์‹คํ—˜์„ ํ†ตํ•ด ์ˆ˜์ถ•ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜์˜€๋‹ค. ๊ตฌ์†์ˆ˜์ถ• ์‹คํ—˜ ์ค‘์—์„œ ์ˆ˜์ถ•์„ ์ €๊ฐ์‹œํ‚ค๋Š” ์ตœ์  ๋ฐฐํ•ฉ์„ ๋„์ถœํ•˜๊ธฐ ์œ„ํ•ด ๋ง-ํ…Œ ์ŠคํŠธ (Ring-test)๋ฅผ ์ˆ˜ํ–‰ํ•˜์˜€๊ณ  ์ˆ˜์ •๋œ ๊ฑด์กฐ์ˆ˜์ถ• ๊ท ์—ด์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์—ฌ ์ด๋ฅผ ๊ฒ€์ฆํ•˜๊ณ ์ž ํ•˜์˜€๋‹ค. ํ•œํŽธ, HPFRCC์˜ ๊ฒฝ์šฐ ์šฐ์ˆ˜ํ•œ ์ธ์žฅ๊ฐ•๋„ ๋ฐœํ˜„ ํŠน์„ฑ์œผ๋กœ ์ธํ•ด ๊ธฐ์กด์˜ ๊ตฌ์†์ˆ˜์ถ• ์‹คํ—˜ ๋ฒ•๋“ค๋กœ๋Š” ์ˆ˜์ถ•๊ท ์—ด์„ ์œ ๋„ํ•  ์ˆ˜ ์—†๋‹ค (Park et al., 2011; Yoo et al., 2011). ์ด์— KS F 2959๋ฅผ ํ† ๋Œ€๋กœ HPFRCC์— ์ ํ•ฉํ•˜ ๊ฒŒ ์ˆ˜์ •๋œ ๊ฑด์กฐ์ˆ˜์ถ• ๊ท ์—ด์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

2. ์‹คํ—˜๊ณ„ํš

2.1. ์žฌ๋ฃŒ ๋ฐ ๋ฐฐํ•ฉ๋น„

๋ณธ ์‹คํ—˜์—๋Š” 1์ข… ๋ณดํ†ต ํฌํ‹€๋žœ๋“œ ์‹œ๋ฉ˜ํŠธ ๋ฐ ์ž…๊ฒฝ 0.5mm ์ด ํ•˜์˜ ์ž”๊ณจ์žฌ, 96%์˜ SiO2๋ฅผ ํฌํ•จํ•˜๊ณ  ํ‰๊ท ์ž…๊ฒฝ์ด 2ฮผm์ธ ์ถฉ ์ „์žฌ, ๋…ธ๋ฅด์›จ์ด์‚ฐ ์‹ค๋ฆฌ์นดํ“ธ (SF), ์ผ๋ณธ์‚ฐ CSA๊ณ„ ํŒฝ์ฐฝ์žฌ, ๋… ์ผ์‚ฐ ๋ฐฑ์ƒ‰ ๋ถ„๋ง์˜ ๊ธ€๋ฆฌ์ฝœ๊ณ„์˜ ์ˆ˜์ถ•์ €๊ฐ์ œ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๋ฐฐ ํ•ฉ์— ์‚ฌ์šฉ๋œ ์žฌ๋ฃŒ๋“ค์˜ ํ™”ํ•™์  ๊ตฌ์„ฑ์„ฑ๋ถ„์€ Table 1๊ณผ ๊ฐ™๋‹ค.

Table 1.

Chemical properties of materials

Composition % (mass) Cement1) Silica fume (SF) Expansive admixture (EA)
CaO 61.33 0.38 13.55
Al2O3 6.40 0.25 18.66
SiO2 21.01 96.00 3.80
Fe2O3 3.12 0.12 -
MgO 3.02 0.10 -
SO3 2.30 - 51.35
K2O - - 0.56
F-CaO - - 16.02
Specific surface(cm2/g) 3,413 200,000 3,117
Density(g/cm3) 3.15 2.10 2.98

1) Note, Type I Portland cement

๊ฐ•์„ฌ์œ ์˜ ๋ฌผ๋ฆฌ์  ํŠน์„ฑ์น˜๋Š” Table 2์— ์ •๋ฆฌํ•˜์˜€๋‹ค. Table 3 ์€ ํŒฝ์ฐฝ์žฌ์™€ ์ˆ˜์ถ•์ €๊ฐ์ œ์˜ ํ˜ผ์ž…์—ฌ๋ถ€์— ๋”ฐ๋ฅธ ์ˆ˜์ถ•์‹คํ—˜์— ์‚ฌ ์šฉ๋œ ๋ฐฐํ•ฉํ‘œ์ด๋‹ค.

Table 2.

Properties of steel fiber

Type of fiber Density (kg/cm3) Tensile strength (MPa) lf 1) (mm) lf/df2) (mm/mm)
Straight fiber 7.8 2,500 13 65

1) Note, lf : length of fiber

2) lf : diameter of fiber

Table 3.

Mix proportions of HPFRCC (ratio in weight)

Nomenclature W/B Cement SF Filler Sand Superplasticizer (SP) Steel fiber SRA1) EA2)
HPF 0.2 1 0.25 0.30 1.10 0.012 Vf=2% - -
HPF-S1 0.01
HPF-S2 0.02
HPF-E5 - 0.05
HPF-E7.5 - 0.075
HPF-S1E7.5 0.01 0.075

1) Note, Shrinkage reducing agent

2) Expansive admixture

2.2. ์‹œํŽธ์ œ์ž‘ ๋ฐ ์‹คํ—˜๋ฐฉ๋ฒ•

2.2.1. ์—ญํ•™์  ํŠน์„ฑ ํ‰๊ฐ€

์••์ถ•๊ฐ•๋„ (KS F 2405)๋Š” ฯ†100โ…น200mm์ธ ์›์ฃผํ˜• ๊ณต์‹œ์ฒด๋ฅผ ๋ณ€์ˆ˜๋ณ„๋กœ 3๊ฐœ์”ฉ ์ œ์ž‘ํ•˜๊ณ  ์ตœ๋Œ€์šฉ๋Ÿ‰ 3,000kN์˜ UTM (Universal Testing Machine)์„ ์ด์šฉํ•˜์—ฌ ์ธก์ •ํ•˜์˜€๋‹ค. ์ง์ ‘ ์ธ์žฅ๊ฐ•๋„๋Š” Fig. 1์˜ Dog-bone ํ˜•์ƒ์„ ๊ฐ–๋Š” ์‹œํ—˜์ฒด๋กœ ์ธก์ •ํ•˜์˜€์œผ๋ฉฐ, ์•• ์ถ•๊ฐ•๋„ ์‹คํ—˜๊ณผ ๋™์ผํ•˜๊ฒŒ ์žฌ๋ น๋ณ„๋กœ 3๊ฐœ์”ฉ ์ œ์ž‘ํ•˜์—ฌ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์—ฌ ํ‰๊ท ๊ฐ’์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค.

Fig. 1

Test Methods for Direct Tensile Strength Test

JKSMI-18-34_F1.jpg

2.2.2. ํ…Œ์ŠคํŠธ (Ring-test)

๊ตฌ์†์ˆ˜์ถ• ์‹คํ—˜์€ AASHTO PP34-98์—์„œ ์ œ์•ˆํ•œ ๋ฐฉ๋ฒ•๊ณผ ๋™์ผํ•˜๊ฒŒ ์‹ค์‹œํ•˜์˜€์œผ๋ฉฐ ๋ชฐ๋“œ ๋ฐ ์‹œํŽธ์˜ ์ƒ์„ธ๋Š” Fig. 2์™€ ๊ฐ™ ๋‹ค. ํ•˜๋ถ€ ๋ชฉ์žฌํŒ์— ํ…Œํ”„๋ก  ์‹œํŠธ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ๋งˆ์ฐฐ์— ์˜ํ•œ ์ฝ˜ ํฌ๋ฆฌํŠธ ๊ตฌ์†์„ ๋ฐฉ์ง€ํ•˜๊ณ , ๋‚ดโ‹…์™ธ๋ถ€ ๊ฐ•์žฌ ๋ง์„ ์„ค์น˜ํ•œ ํ›„์— HPFRCC๋ฅผ ํƒ€์„คํ•˜์˜€๋‹ค.

Fig. 2

Geometry of Ring-Test

JKSMI-18-34_F2.jpg

ํƒ€์„ค ํ›„ 24์‹œ๊ฐ„ ์ดํ›„์—๋Š” ์™ธ๋ถ€ ๊ฐ•์žฌ ๋ง์„ ์ œ๊ฑฐํ•˜๊ณ  ์•Œ๋ฃจ๋ฏธ ๋Š„ ๋ถ€์ฐฉ ํ…Œ์ดํ”„๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ์‹œํŽธ์˜ ์ƒโ‹…ํ•˜๋ถ€์˜ ์ˆ˜๋ถ„์ด๋™์„ ์ฐจ๋‹จํ•˜์˜€๋‹ค. ๊ตฌ์† ๋ณ€ํ˜•๋ฅ  ์ธก์ •์„ ์œ„ํ•ด ์ด 4๊ฐœ์˜ ํ‘œ๋ฉด๊ฒŒ์ด์ง€ ๋ฅผ ๋‚ด๋ถ€ ๊ฐ•์žฌ์˜ ์ค‘์•™๋ถ€์— ์„ค์น˜ํ•˜๊ณ  ๋ฐ์ดํ„ฐ๋กœ๊ฑฐ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ๋ณ€ํ˜•๋ฅ ์„ ์ธก์ •ํ•˜์˜€๋‹ค. ์ด ๋ชจ๋“  ์ ˆ์ฐจ๋Š”, ์˜จ๋„ 23ยฑ1โ„ƒ, ์Šต๋„ 60ยฑ5%์ธ ํ•ญ์˜จํ•ญ์Šต์‹ค์—์„œ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

2.2.3. ๊ฑด์กฐ์ˆ˜์ถ•๊ท ์—ด์‹คํ—˜

์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์ˆ˜์ •๋œ ๊ฑด์กฐ์ˆ˜์ถ•๊ท ์—ด์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ๊ธฐ ์กด ๊ฑด์กฐ์ˆ˜์ถ•๊ท ์—ด์‹คํ—˜์— ๊ด€ํ•œ KS ๊ทœ์ •์— ์˜ํ•˜๋ฉด ๊ตฌ์†๋˜๋Š” ์ฝ˜ ํฌ๋ฆฌํŠธ ์‹œํŽธ ์ค‘์•™์˜ ๋‹จ๋ฉด์ด 100ร—100mm์œผ๋กœ ๊ทœ์ •๋˜์–ด ์žˆ์œผ ๋‚˜, ์ˆ˜์ •๋œ ๊ฑด์กฐ์ˆ˜์ถ•๊ท ์—ด์‹คํ—˜์€ Fig. 3๊ณผ ๊ฐ™์ด ์–‘๋๋‹จ๋ถ€์— ๋Œ๊ธฐ๋ฅผ ์ฃผ์–ด ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ๊ตฌ์†ํ•˜๋„๋ก ์„ค๊ณ„ํ•˜์˜€๊ณ  ์ค‘์•™๋ถ€ ์ฝ˜ ํฌ๋ฆฌํŠธ์˜ ๋‘๊ป˜๋ฅผ ๊ธฐ์กด์˜ 100mm์—์„œ 20, 30, 40mm๋กœ ๊ฐ์†Œ ์‹œ์ผœ ๊ตฌ์†๋„๋ฅผ ํ–ฅ์ƒ์‹œ์ผœ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

Fig. 3

Test Procedure of Drying Shrinkage Cracking Test

JKSMI-18-34_F3.jpg

๊ทธ ์™ธ์˜ ์‹คํ—˜๋ฐฉ๋ฒ• ๋ฐ ๋‹จ๋ฉด์˜ ์ƒ์„ธ๋Š” KS F 2959์˜ ๊ทœ์ •๊ณผ ๋™์ผํ•˜๊ฒŒ ์ ์šฉํ•˜์˜€๋‹ค. ์‹คํ—˜ ์ˆ˜ํ–‰๊ณผ์ •์€ ์šฐ์„ , ์‹คํ—˜ ๋ชฐ๋“œ์— HPFRCC๋ฅผ ํƒ€์„คํ•˜๊ณ  ํ‘œ๋ฉด์ด ๊ธ‰๊ฒฉํžˆ ๋งˆ๋ฅด์ง€ ์•Š๋„๋ก ๋น„๋‹์„ ๋ฎ์–ด ํ‘œ๋ฉด์ฒ˜๋ฆฌ๋ฅผ ํ•˜์˜€๋‹ค. HPFRCC ํƒ€์„ค ํ›„ 1์ผ ์ดํ›„์—๋Š” ์ค‘ ์•™๋ถ€์œ„๋ฅผ ๊ฐ์‹ธ๊ณ  ์žˆ๋Š” ๊ฑฐํ‘ธ์ง‘์„ ํƒˆํ˜•ํ•˜๊ณ  ๋‹จ๋ฉด์„ ๋ชจ๋‘ ๋…ธ์ถœ ์‹œํ‚จ ํ˜•ํƒœ๋กœ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ ์ˆ˜์ถ•์— ์˜ํ•œ ๊ท ์—ด ๋ฐœ์ƒ ์‹œ์ ์€ ๊ตฌ์† ๋ชฐ๋“œ์— ์Šคํ‹ธ๊ฒŒ์ด์ง€ ๋ถ€์ฐฉํ•˜์—ฌ ๋ณ€ํ˜•๋ฅ ์„ ์ธก ์ •ํ•˜๊ณ  ๊ทธ ๋ณ€ํ˜•๋ฅ ์ด ๊ธ‰๋ณ€ํ•˜๋Š” ์‹œ์ ์œผ๋กœ ๊ทœ์ •ํ•˜์˜€์œผ๋ฉฐ, ์ƒ๊ธฐ ์˜ ์‹คํ—˜์€ ์˜จ๋„ 23ยฑ1โ„ƒ, ์Šต๋„ 60ยฑ5%์ธ ํ•ญ์˜จํ•ญ์Šต์‹ค์—์„œ ์ˆ˜ ํ–‰ํ•˜์˜€๋‹ค.

3. ์‹คํ—˜๊ฒฐ๊ณผ

3.1. ์—ญํ•™์  ํŠน์„ฑ

Fig. 4๋Š” ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ HPFRCC ์˜ ์••์ถ•์‹คํ—˜ ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์œผ๋กœ ํŒฝ์ฐฝ์žฌ๋ฅผ ํ˜ผ์ž…ํ•œ ๊ฒฝ์šฐ ์•• ์ถ•๊ฐ•๋„๋Š” ๋‹ค์†Œ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€์œผ๋ฉฐ, ์ˆ˜์ถ•์ €๊ฐ์ œ๋Š” ์•• ์ถ•๊ฐ•๋„๋ฅผ ๊ฐ์†Œ์‹œํ‚ค๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. ํŒฝ์ฐฝ์žฌ์™€ ์ˆ˜์ถ•์ €๊ฐ์ œ๋ฅผ ๋ชจ๋‘ ํ˜ผ์ž…ํ•œ HPF-S1E7.5์˜ ๊ฒฝ์šฐ์—๋Š” ์••์ถ•๊ฐ•๋„๊ฐ€ ์•ฝ 200 MPa์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ๋ฅผ ํ˜ผ์ž…ํ•˜์ง€ ์•Š์€ HPF ์‹œํŽธ๋ณด๋‹ค๋Š” ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚ฌ์ง€๋งŒ, ํŒฝ์ฐฝ์žฌ๋งŒ ํ˜ผ์ž…ํ•œ HPF-E5 ๋ฐ HPF-E7.5์— ๋น„ํ•ด์„œ๋Š” ์•ฝ๊ฐ„ ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. ๋ชจ ๋“  ์‹œํŽธ์—์„œ ์„ค๊ณ„๊ธฐ์ค€๊ฐ•๋„ 180 MPa๋ณด๋‹ค ํฐ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

Fig. 4.

Effect of SRA and EA on the Compressive Strength of HPFRCC

JKSMI-18-34_F4.jpg

Fig. 5๋Š” ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ HPFRCC ์˜ ์ธ์žฅ์‹คํ—˜ ๊ฒฐ๊ณผ์ด๋‹ค. ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…ํ•จ์— ๋”ฐ ๋ผ์„œ ์ธ์žฅ๊ฐ•๋„๋Š” ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ทธ ์ด์œ ๋Š” ์ˆ˜์ถ• ์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…์œผ๋กœ ์ธํ•ด ์„ฌ์œ ์™€ HPFRCC ๋งคํŠธ๋ฆญ ์Šค (matrix)๊ฐ„์˜ ๊ตฌ์†์••๋ ฅ (radial confinement pressure)์ด ๊ฐ์†Œํ•˜์—ฌ ์„ฌ์œ ์˜ ๋ถ€์ฐฉ๊ฐ•๋„๊ฐ€ ๊ฐ์†Œํ–ˆ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค (Park et al., 2012). ์ดˆ๊ธฐ ๊ท ์—ด ๊ฐ•๋„ (first crack strength)๋Š” ์„ฌ์œ  ๊ฐ€๊ต ํšจ๊ณผ (fiber bridging effect) ๋ณด๋‹ค๋Š” ๋งคํŠธ๋ฆญ์Šค (matrix) ์˜ ๊ฐ•๋„์— ์˜ํ–ฅ์„ ํฌ๊ฒŒ ๋ฐ›๋Š”๋‹ค (Kang et al., 2010). ์‹คํ—˜๊ฒฐ ๊ณผ HPF-E5 ์‹œํŽธ์—์„œ ์ดˆ๊ธฐ ๊ท ์—ด ๊ฐ•๋„๊ฐ€ ๊ฐ€์žฅ ์ž‘๊ฒŒ ๋‚˜ํƒ€๋‚ฌ์œผ ๋ฉฐ, ์ธ์žฅ๊ฐ•๋„์™€ ์œ ์‚ฌํ•˜๊ฒŒ ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…์— ๋”ฐ ๋ผ์„œ ์ดˆ๊ธฐ ๊ท ์—ด ๊ฐ•๋„๊ฐ€ ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. ๋ชจ๋“  ์‹œํ—˜ ์ฒด์˜ ์ธ์žฅ๊ฐ•๋„๋Š” ์„ค๊ณ„๊ธฐ์ค€ ์ธ์žฅ๊ฐ•๋„ 8.8 MPa (KICT, 2012) ์ด์ƒ์„ ํ™•๋ณดํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

Fig. 5.

Effect of SRA and EA on the First Crack and Tensile Strengths of HPFRCC

JKSMI-18-34_F5.jpg

3.2. ๋ง-ํ…Œ์ŠคํŠธ (Ring-test)

Fig. 6์€ ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ HPFRCC ์˜ ๋ง-ํ…Œ์ŠคํŠธ ์‹คํ—˜ ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ๋ชจ๋“  ์‹œํ—˜์ฒด์˜ ๊ฒฝ ์šฐ ์˜จ๋„๋ณ€ํ™”์™€ ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๋ณ€ํ˜•์ด ๋‹ฌ๋ผ์ง€๋Š” ์‹œ์ ์„ ์ธก์ • ์‹œ์ ์œผ๋กœ ํ•˜์˜€๋‹ค (Park et al., 2014). Fig. 6์—์„œ ์ˆ˜์ถ•์ €๊ฐ์ œ ์™€ ํŒฝ์ฐฝ์žฌ๋ฅผ ํ˜ผ์ž…ํ•˜์ง€ ์•Š์€ HPF ์‹œํŽธ์—์„œ ๊ฐ€์žฅ ํฐ ๋‚ด๋ถ€ ๊ฐ• ์žฌ ๋ง์˜ ๋ณ€ํ˜•๋ฅ ์ด ์ธก์ •๋˜์—ˆ๋‹ค. ์ˆ˜์ถ•์ €๊ฐ์ œ์˜ ํ˜ผ์ž…๋ฅ ์ด ์ฆ๊ฐ€ ํ•จ์— ๋”ฐ๋ผ ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๋ณ€ํ˜•๋ฅ ์€ ๊ฐ์†Œํ•˜์˜€๊ณ , ์ˆ˜์ถ•์ €๊ฐ์ œ ๋ฅผ ๊ฐ๊ฐ 1% ๋ฐ 2% ํ˜ผ์ž…ํ•œ ๊ฒฝ์šฐ (HPF-S1, HPF-S2), 28์ผ ์žฌ๋ น์—์„œ ๋‚ด๋ถ€ ๊ฐ•์žฌ์˜ ๋ณ€ํ˜•๋ฅ ์ด ์•ฝ 15%, 18% ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํŒฝ์ฐฝ์žฌ๋ฅผ ๊ฐ๊ฐ 5% ๋ฐ 7.5% ํ˜ผ์ž…ํ•œ ๊ฒฝ์šฐ (HPF-E5, HPF-E7.5)์˜ ๊ฒฝ์šฐ ํŒฝ์ฐฝ์žฌ์˜ ๊ธ‰๊ฒฉํžˆ ์‘๊ฒฐํ•˜๋Š” ์„ฑ ์งˆ์— ์˜ํ•ด ์ตœ๋Œ€ ํŒฝ์ฐฝ๋ฅ  ์ดํ›„์— ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๋ณ€ํ˜•๋ฅ ์ด ๊ธ‰ ๊ฒฉํžˆ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. ํƒ€์„ค ํ›„ ์•ฝ 10์ผ ์žฌ๋ น ์ดํ›„๋ถ€ ํ„ฐ๋Š” ์˜คํžˆ๋ ค ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๋ณ€ํ˜•๋ฅ ์ด ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค.

Fig. 6.

Average Steel Ring Strains of HPFRCC

JKSMI-18-34_F6.jpg

์ด๋Š” 10์ผ ์žฌ๋ น ์ดํ›„๋ถ€ํ„ฐ ์ž์œ ์ˆ˜์ถ• ๋ณ€ํ˜•๋ฅ ์ด ๋ฏธ๋ฏธํ•˜์˜€๊ณ , ๋˜ํ•œ ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๊ตฌ์†์••๋ ฅ์— ์˜ํ•ด ์ธ์žฅ ํฌ๋ฆฌํ”„ ํ˜„์ƒ์ด ๋ฐœ์ƒํ–ˆ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค (Yoo et al., 2013). ๋”ฐ๋ผ์„œ, HPF ์‹œํŽธ์— ๋น„ํ•ด 28์ผ ์žฌ๋ น์—์„œ ์•ฝ 40%, 52%์˜ ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๋ณ€ํ˜•๋ฅ ์ด ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํŠนํžˆ, ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ ์ฐฝ์žฌ๋ฅผ ์‹œ๋ฉ˜ํŠธ ์ค‘๋Ÿ‰์— ๋Œ€ํ•ด ๊ฐ๊ฐ 1%, 7.5% ์กฐํ•ฉํ•˜์—ฌ ํ˜ผ์ž…ํ•œ HPF-S1E7.5 ์‹œํŽธ์˜ ๊ฒฝ์šฐ, ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๋ณ€ํ˜•๋ฅ ์€ ๊ฐ€์žฅ ์ž‘ ์€ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด HPFRCC์˜ ์ˆ˜์ถ•์„ ๊ฐ€์žฅ ํšจ์œจ์ ์œผ๋กœ ์ €๊ฐ์‹œ ํ‚ค๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋Š” ์ˆ˜์ถ•์ €๊ฐ์ œ์˜ ํ˜ผ์ž…์œผ๋กœ ํŒฝ์ฐฝ์žฌ ์˜ ๊ธ‰๊ฒฉํžˆ ์‘๊ฒฐํ•˜๋Š” ์„ฑ์งˆ์„ ์ƒ์‡„ํ•˜๊ณ , ์ˆ˜์ถ• ๋ฐœํ˜„์‹œ์ ์„ ์ง€์—ฐ ์‹œ์ผฐ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค (Park et al., 2014).

3.3. ๊ฑด์กฐ์ˆ˜์ถ• ๊ท ์—ด์‹คํ—˜

์ด ์—ฐ๊ตฌ์—์„œ๋Š” HPFRCC์˜ ์ˆ˜์ถ•์„ ๊ฐ€์žฅ ํšจ์œจ์ ์œผ๋กœ ์ €๊ฐ ์‹œํ‚ฌ ์ˆ˜ ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚œ ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ๋ฅผ ์กฐํ•ฉํ•˜ ์—ฌ ํ˜ผ์ž…ํ•œ HPF-S1E7.5์— ๋Œ€ํ•˜์—ฌ ๊ฑด์กฐ์ˆ˜์ถ•์‹œํ—˜์„ ํ†ตํ•ด ๊ฒ€์ฆ ์„ ํ•˜๊ณ ์ž ํ•˜์˜€๋‹ค. ๋น„๊ต๋ฅผ ์œ„ํ•˜์—ฌ ์ˆ˜์ถ•์ €๊ฐ์žฌ๋ฃŒ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š์€ HPF์™€ ๋น„๊ต๋ฅผ ํ•˜์˜€๋‹ค.

Fig. 7์€ ์™ธ๋ถ€ ๊ฐ•์žฌ ํ”„๋ ˆ์ž„์˜ ๋ณ€ํ˜•๋ฅ  ๊ทธ๋ž˜ํ”„์ด๋‹ค. ์™ธ๋ถ€ ๊ฐ• ์žฌ์˜ ๋ณ€ํ˜•๋ฅ ์€ ์ŠคํŠธ๋ ˆ์ธ ๊ฒŒ์ด์ง€๋ฅผ ์™ธ๋ถ€ ๊ฐ•์žฌ ํ”„๋ ˆ์ž„์˜ ์–‘์ชฝ์— ๋‘ ๊ฐœ๋ฅผ ์„ค์น˜ํ•˜์—ฌ ํ‰๊ท ๊ฐ’์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. HPF ์™€ HPF-S1E7.5 ๋ชจ๋‘ ํƒ€์„ค ํ›„ ์•ฝ 7์ผ ์žฌ๋ น๊นŒ์ง€๋Š” ์™ธ๋ถ€ ๊ฐ•์žฌ์˜ ๋ณ€ํ˜•๋ฅ ์ด ๊ธ‰๊ฒฉ ํžˆ ์ฆ๊ฐ€ํ•˜๋‹ค๊ฐ€ ๊ทธ ์ดํ›„์—๋Š” ๊ฐ•์žฌ์˜ ๋ณ€ํ˜•๋ฅ ์˜ ์ฆ๊ฐ€๋Ÿ‰์ด ๊ธ‰๊ฒฉ ํžˆ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ทธ ์ด์œ ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฐ•๋„๊ฐ€ ํƒ€์„ค ์ดํ›„ ์•ฝ 7์ผ ์žฌ๋ น๊นŒ์ง€๋Š” ๊ธ‰๊ฒฉํ•˜๊ฒŒ ์ฆ๊ฐ€ํ•˜์—ฌ, ์™ธ๋ถ€ ๊ฐ•์žฌ ๋ฅผ ์ˆ˜์ถ•์‹œํ‚ค๋Š” ๊ตฌ์†์••๋ ฅ์€ ์ฆ๊ฐ€ํ–ˆ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค (Yoo et al., 2013).

Fig. 7.

Average Strains of outer steel frame

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Fig. 7์€ ์™ธ๋ถ€ ๊ฐ•์žฌ ํ”„๋ ˆ์ž„์˜ ๋ณ€ํ˜•๋ฅ  ๊ทธ๋ž˜ํ”„์ด๋‹ค. ์™ธ๋ถ€ ๊ฐ• ์žฌ์˜ ๋ณ€ํ˜•๋ฅ ์€ ์ŠคํŠธ๋ ˆ์ธ ๊ฒŒ์ด์ง€๋ฅผ ์™ธ๋ถ€ ๊ฐ•์žฌ ํ”„๋ ˆ์ž„์˜ ์–‘์ชฝ์— ๋‘ ๊ฐœ๋ฅผ ์„ค์น˜ํ•˜์—ฌ ํ‰๊ท ๊ฐ’์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. HPF ์™€ HPF-S1E7.5 ๋ชจ๋‘ ํƒ€์„ค ํ›„ ์•ฝ 7์ผ ์žฌ๋ น๊นŒ์ง€๋Š” ์™ธ๋ถ€ ๊ฐ•์žฌ์˜ ๋ณ€ํ˜•๋ฅ ์ด ๊ธ‰๊ฒฉ ํžˆ ์ฆ๊ฐ€ํ•˜๋‹ค๊ฐ€ ๊ทธ ์ดํ›„์—๋Š” ๊ฐ•์žฌ์˜ ๋ณ€ํ˜•๋ฅ ์˜ ์ฆ๊ฐ€๋Ÿ‰์ด ๊ธ‰๊ฒฉ ํžˆ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ทธ ์ด์œ ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฐ•๋„๊ฐ€ ํƒ€์„ค ์ดํ›„ ์•ฝ 7์ผ ์žฌ๋ น๊นŒ์ง€๋Š” ๊ธ‰๊ฒฉํ•˜๊ฒŒ ์ฆ๊ฐ€ํ•˜์—ฌ, ์™ธ๋ถ€ ๊ฐ•์žฌ ๋ฅผ ์ˆ˜์ถ•์‹œํ‚ค๋Š” ๊ตฌ์†์••๋ ฅ์€ ์ฆ๊ฐ€ํ–ˆ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค (Yoo et al., 2013).

ํŒฝ์ฐฝ์žฌ์™€ ์ˆ˜์ถ•์ €๊ฐ์ œ๋ฅผ ํ˜ผ์ž…ํ•œ DS-HPF-S1E7.5 (DS: Drying shrinkage) ๊ณ„์—ด์˜ ๊ฒฝ์šฐ์—๋Š” ํƒ€์„ค ์ดˆ๊ธฐ์— ๋ถ€ํ”ผ๊ฐ€ ํŒฝ์ฐฝํ•จ์— ์˜ํ•ด์„œ ๋ณ€ํ˜•๋ฅ ์ด+๋ฐฉํ–ฅ (ํŒฝ์ฐฝ)์œผ๋กœ ๋ฐœ์ƒํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€์œผ ๋ฉฐ, ์•ฝ 2์ผ ์žฌ๋ น์ดํ›„๋ถ€ํ„ฐ๋Š” ์ˆ˜์ถ•ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚˜ DS-HPF ๊ณ„์—ด์— ๋น„ํ•ด ์ตœ๋Œ€ ๋ณ€ํ˜•๋ฅ ์ด ์•ฝ 26.5%์—์„œ 29.3% ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. DS-HPF ๊ณ„์—ด์˜ ๊ฒฝ์šฐ, ์•ฝ 7์ผ ์žฌ๋ น์ดํ›„๋ถ€ํ„ฐ ๋Š” ์™ธ๋ถ€ ๊ฐ•์žฌ ํ”„๋ ˆ์ž„์˜ ๋ณ€ํ˜•๋ฅ ์ด ์•ฝ๊ฐ„ ๊ฐ์†Œํ•˜๊ฑฐ๋‚˜ ์ผ์ •ํ•œ ๊ฐ’ ์— ์ˆ˜๋ ดํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์ด๋Š” ์ˆ˜์ถ•๊ท ์—ด์˜ ์˜ํ–ฅ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค (Park et al., 2014).

๊ท ์—ด๊ด€์ธก๊ฒฐ๊ณผ DS-HPF ๊ณ„์—ด์˜ ๋ชจ๋“  ์‹œํŽธ์—์„œ ํƒ€์„ค ํ›„ 10 ์ผ ์žฌ๋ น ์ด์ „์—์„œ ์ˆ˜์ถ•๊ท ์—ด์ด ๋ฐœ์ƒํ•œ ๊ฒƒ์œผ๋กœ ํ™•์ธ๋˜์—ˆ๋‹ค. ๊ทธ ๋Ÿฌ๋‚˜ HPFRCC๋Š” ๋ณ€ํ˜•๋ฅ  ๊ฒฝํ™” (strain-hardening) ๊ฑฐ๋™์„ ๋ณด ์ด๋Š” ์‹œ๋ฉ˜ํŠธ๋ณตํ•ฉ์ฒด์ด๊ธฐ ๋•Œ๋ฌธ์— ์™ธ๋ถ€ ๊ฐ•์žฌ์˜ ๋ณ€ํ˜•๋ฅ  ์ธก์ •์œผ ๋กœ๋Š” ์ˆ˜์ถ•๊ท ์—ด ์‹œ๊ธฐ๋ฅผ ์ •ํ™•ํ•˜๊ฒŒ ํŒŒ์•…ํ•  ์ˆ˜๋Š” ์—†์—ˆ๋‹ค.

Fig. 8์€ ๊ฑด์กฐ์ˆ˜์ถ• ๊ท ์—ด์‚ฌ์ง„์ด๋‹ค. ๋ณด๋Š”๋ฐ”์™€ ๊ฐ™์ด HPF์˜ ๊ฒฝ์šฐ, ๋ชจ๋“  ์‹œํŽธ์—์„œ ์ˆ˜์ถ•๊ท ์—ด์ด ๋ฐœ์ƒํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋ฐ˜๋ฉด์— ์ด ์—ฐ๊ตฌ์—์„œ ๋ง-ํ…Œ์ŠคํŠธ๋ฅผ ํ†ตํ•ด ์ˆ˜์ถ•์ €๊ฐ์— ๊ฐ€์žฅ ํšจ์œจ ์ ์ธ HPFRCC์˜ ๋ฐฐํ•ฉ์กฐ๊ฑด์œผ๋กœ ์ œ์‹œ๋œ ์‹œํŽธ์ธ HPF-S1E7.5 ์—๋Š” ์ˆ˜์ถ•๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์ง€ ์•Š์•˜๋‹ค.

Fig. 8.

Crack patterns of drying shrinkage cracking test specimens

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์ˆ˜์ถ•์ €๊ฐ์žฌ๋ฃŒ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š์€ DS-HPF20์˜ ๊ฒฝ์šฐ ๊ท ์—ด๊ฒŒ ์ด์ง€๋ฅผ ์ด์šฉํ•˜์—ฌ ์ธก์ •ํ•œ ๊ฒฐ๊ณผ ์ตœ๋Œ€ ๊ท ์—ดํญ์€ 28์ผ ์žฌ๋ น์—์„œ ์•ฝ 0.2mm๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, DS-HPF30 ๋ฐ DS-HPF40์˜ ๊ฒฝ์šฐ ์—๋Š” 0.2mm, 0.04mm๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

์•ž์„œ ์„ค๋ช…ํ•œ ๊ฒƒ๊ณผ ๊ฐ™์ด HPFRCC์˜ ๊ฒฝ์šฐ ์ฒซ ๊ท ์—ด ์ดํ›„์— ๋ณ€ํ˜• ๊ฒฝํ™” ๊ฑฐ๋™์„ ๋ณด์ด๊ธฐ ๋•Œ๋ฌธ์— ๊ท ์—ด ์‹œ์ ์— ๋Œ€ํ•œ ์ •ํ™•ํ•œ ์ธก์ •์ด ๋ถˆ๊ฐ€๋Šฅ ํ•˜์˜€๋‹ค. ๋˜ํ•œ, ์ „์ฒด ๋ถ€ํ”ผ์˜ 2%์— ํ•ด๋‹นํ•˜๋Š” ๊ฐ• ์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•˜์˜€๊ธฐ ๋•Œ๋ฌธ์— ๋‹ค์ˆ˜์˜ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์‹œํŽธ์˜ ๋‘๊ป˜๊ฐ€ ๊ฐ€์žฅ ํฐ DS-HPF40์˜ ๊ฒฝ์šฐ ์ตœ๋Œ€ ๊ท ์—ดํญ์ด 0.04mm๋กœ ๊ฐ€์žฅ ์ž‘์€ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์ด๋Š” ๋‹จ๋ฉด ์˜ ๋‘๊ป˜๊ฐ€ ๋‘๊บผ์›Œ์ ธ ๊ท ์—ด ์ €ํ•ญ์„ฑ์ด DS-HPF20์™€ DS-HPF30 ์˜ ์‹œํŽธ์— ๋น„ํ•ด์„œ ํฌ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค (Park et al., 2013).

4. ๊ฒฐ ๋ก 

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” HPFRCC์˜ ์ˆ˜์ถ•์„ ํšจ์œจ์ ์œผ๋กœ ์ €๊ฐ์‹œํ‚ฌ ์ˆ˜ ์žˆ๋Š” ๋ฐฐํ•ฉ์„ ์ฐพ๊ธฐ ์œ„ํ•ด ์ˆ˜์ถ•์ €๊ฐ์ œ ๋ฐ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ฅธ ์—ญํ•™์  ํŠน์„ฑ ํ‰๊ฐ€, ๊ตฌ์† ์ˆ˜์ถ• ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ๋ณธ ์—ฐ ๊ตฌ๋ฅผ ํ†ตํ•ด ์–ป์€ ๊ฒฐ๋ก ์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

  1. HPFRCC์— ํŒฝ์ฐฝ์žฌ๋ฅผ ํ˜ผ์ž…ํ•œ ๊ฒฝ์šฐ ์••์ถ•๊ฐ•๋„๊ฐ€ ์ฆ๊ฐ€ํ•˜ ์˜€์œผ๋‚˜ ์ˆ˜์ถ•์ €๊ฐ์ œ ๋ฐ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผํ•ฉ์— ๋”ฐ๋ฅธ ์ธ์žฅ๊ฐ•๋„ ๋Š” ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ทธ ์ด์œ ๋Š” ์ˆ˜์ถ•์ €๊ฐ์ œ ์™€ ํŒฝ์ฐฝ์žฌ์˜ ํ˜ผ์ž…์œผ๋กœ ์ธํ•ด ์„ฌ์œ ์™€ HPFRCC์˜ ๋งคํŠธ ๋ฆญ์Šค (matrix) ๊ฐ„์˜ ๊ตฌ์†์••๋ ฅ์ด ๊ฐ์†Œํ•˜์—ฌ ์„ฌ์œ ์˜ ๋ถ€์ฐฉ ๊ฐ•๋„๊ฐ€ ๊ฐ์†Œํ–ˆ๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๊ฐ•๋„๊ฐ’์˜ ๊ฐ์†Œ๋Ÿ‰์ด ํฌ์ง€ ์•Š๊ณ , ๋ชจ๋“  ์‹œํ—˜์ฒด์˜ ์ธ์žฅ๊ฐ•๋„๊ฐ€ ์„ค๊ณ„ ๊ธฐ์ค€ ์ธ์žฅ๊ฐ•๋„ 8.8 MPa ๋ณด๋‹ค ํฐ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๊ธฐ ๋•Œ ๋ฌธ์— HPFRCC์— ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ๋„ ๊ตฌ์กฐ์„ค๊ณ„ ๋ฐ ์—ญํ•™์  ํŠน์„ฑ์— ๋Œ€ํ•œ ๋ถ€๋ถ„์—๋Š” ๋ฌธ์ œ๊ฐ€ ์—† ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

  2. ๋ง-ํ…Œ์ŠคํŠธ (Ring-test) ์‹คํ—˜ ๊ฒฐ๊ณผ ์ˆ˜์ถ•์ €๊ฐ์ œ์™€ ํŒฝ์ฐฝ์žฌ ๋ฅผ ๊ฐ๊ฐ 1%, 7.5% ์กฐํ•ฉํ•˜์—ฌ ํ˜ผ์ž…ํ•œ ๊ฒฝ์šฐ ์ˆ˜์ถ•์ €๊ฐ์ œ ๊ฐ€ ํŒฝ์ฐฝ์žฌ์˜ ๊ธ‰๊ฒฉํžˆ ์‘๊ฒฐํ•˜๋Š” ์„ฑ์งˆ์„ ์ƒ์‡„ํ•˜๊ณ , ์ˆ˜์ถ• ๋ฐœํ˜„์‹œ์ ์„ ์ง€์—ฐ์‹œ์ผœ ๋‚ด๋ถ€ ๊ฐ•์žฌ ๋ง์˜ ๋ณ€ํ˜•๋ฅ ์ด ๊ฐ€์žฅ ์ž‘์€ ๊ฐ’์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋”ฐ๋ผ์„œ ์ด ์กฐ๊ฑด์ด HPFRCC์˜ ์ˆ˜์ถ•์„ ๊ฐ€์žฅ ํšจ์œจ์ ์œผ๋กœ ์ €๊ฐ์‹œํ‚ฌ ์ˆ˜ ์žˆ๋Š” ์ตœ์ ๋ฐฐํ•ฉ์œผ ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

  3. ์ˆ˜์ •๋œ ๊ฑด์กฐ์ˆ˜์ถ• ๊ท ์—ด์‹คํ—˜์„ ํ†ตํ•ด ์ˆ˜์ถ•์ €๊ฐ์— ํšจ์œจ์  ์ธ HPFRCC์˜ ์ตœ์ ๋ฐฐํ•ฉ์„ ๊ฒ€์ฆํ•œ ๊ฒฐ๊ณผ, ์ˆ˜์ถ•์ €๊ฐ์žฌ๋ฃŒ ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š์€ HPFRCC ๊ฒฝ์šฐ ๋ชจ๋“  ์‹œํŽธ์—์„œ ์ˆ˜์ถ• ๊ท ์—ด์ด ๋ฐœ์ƒํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋ฐ˜๋ฉด์— ํŒฝ์ฐฝ์žฌ์™€ ์ˆ˜ ์ถ•์ €๊ฐ์ œ ๊ฐ๊ฐ 1%, 7.5% ํ˜ผ์ž…ํ•œ HPFRCC์—๋Š” ์ˆ˜์ถ• ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์ง€ ์•Š์•„ ์ด ๋ฐฐํ•ฉ์ด HPFRCC์˜ ์ˆ˜์ถ•์„ ๊ฐ์†Œ์‹œ์ผœ ๊ท ์—ด์ €๊ฐ์— ํšจ๊ณผ๊ฐ€ ์žˆ์Œ์„ ํ™•์ธํ•˜์˜€๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

๋ณธ ์—ฐ๊ตฌ๋Š” ๊ตญํ† ๊ตํ†ต๋ถ€ ๊ฑด์„ค๊ธฐ์ˆ ์—ฐ๊ตฌ์‚ฌ์—… ๋ฐฉํ˜ธโ‹…๋ฐฉํญ ์—ฐ๊ตฌ ๋‹จ (๊ณผ์ œ๋ฒˆํ˜ธ : 13๊ฑด์„ค์—ฐ๊ตฌSO2 ๋ฐฉํ˜ธโ‹…๋ฐฉํญ์šฉ ๊ณ ์„ฑ๋Šฅ ์„ฌ์œ ๋ณด ๊ฐ• ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์žฌ๋ฃŒ ๋ฐ ์„ฑ๋Šฅํ‰๊ฐ€ ๊ธฐ์ˆ  ๊ฐœ๋ฐœ)์˜ ์—ฐ๊ตฌ๋น„ ์ง€์›

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