04.439~449(07-085).fm

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1 G Journal of the Korea Concrete Institute Vol. 20, No. 4, pp. 439~449, August, 2008 ywgj p y en w ü w š w 1) Á y 1) *Á 1) Á½ y 1) Á» 1) 1) w zy lœw Chloride Penetration Resistance of Ternary Blended Concrete and Discussion for Durability Ha-Won Song, 1) Chang-Hong Lee, 1) * Kewn-Chu Lee, 1) Jae-Hwan Kim, 1) and Ki-Yong Ann 1) 1) Dept. of Civil and Environmental Engineering, Yonsei University, Seoul , Korea ABSTRACT Mineral admixtures are used to improve the quality of concrete and to develop sustainability of concrete structures. Supplementary cementitious materials (SCM), such as silica fume (SF), granulated blast furnace slag (GGBS) and pulverized fly ash (PFA), are gradually recognized as useful mineral admixture for producing high performance concrete. The study on ternary blended concrete utilizing mainly three major mineral admixtures is limited and the study on durability and chloride induced corrosion resistance of ternary blended concrete is very few. This study examines the durability characteristics of the ternary blended concrete composed of different amount of the SCM with ordinary Portland concrete and the study experimentally focuses on corrosion resistance evaluation of ternary blended concrete subjected to chloride attack. In this study, 50% replacement ratio of mineral admixture to OPC was used, while series of combination of 20~40% GGBS, 5~15% SF and 10~45% PFA binder were used for chloride corrosion resistance test. This study concerned the durability properties of the ternary blended concrete including the corrosion resistance, chloride binding, chloride transport and acid neutralization capacity. It was found that the ternary blended concrete utilizing the SCM densified the pore structures to lower the rate of chloride transport. Also, increased chloride binding and buffering to acid were observed for the ternary blended concrete with chlorides in cast. Keywords : ternary blended concrete, durability, chloride transport, chloride penetration, concrete mix 1. gj p ³ ƒ» e ƒ w. gj p z ƒ w e. gj p y w» w w, w w. gj p ü, ü y w w. gj p d» d w (life-cycle) š ü š w ƒ w, 1) ƒ t ü» w gj p w šü w œw v *Corresponding author lch1730@yonsei.ac.kr Received October 2, 2007, Revised March 18, 2008, Accepted May 23, by Korea Concrete Institute ù š ev y. ü t w w gj p œ» wš ƒ w z ƒ š. ù ü ev (SF), š (GGBS) v (PFA) w w gj p w œ ù š ev v w w w gj p w.» g j p w w msp p ev š, y msp p š v msp p v, ev yw eyw w g j p w w. gj p w y yy z y z» š š š ù ü p w w ¾ wš x y. msp p š 439

2 , v, ev y w z w yw w z w ü w z w ü d gj p w z y ƒ wš w. w p y w» w p w gj p w, œ»» e x, š y x y w w x, w x, SEM, XRD w x mw w yw gj p w w y en w ü w š wwš w. 2. x z ywgj p w ü w sƒ wwš, ƒ x SEM, XRD,, œ», y en x gj p r w, š y y w w x p yw š w» w pr p w š p x» w z jš k r w x ww. ƒ x Table 1 ùkü. 2.1 ywgj p y w gj p ü p Áyw p š y pr p y w, w y SEM, XRD»» w ywgj p y y p w w. w» Table ywgj p» w p ywgj p» w p x, œ» d x ww, w w yw p p S msp p (OPC) w. v ü k y B w š K, ev q S w w. w, OPC 3,250 ± 300 cm 2 /g, v 2,400 cm 2 /g, š 4,000 cm 2 /g, ev 150,000~300,000 cm /g OPC ü % w. yw Table w yw p w p 50% w š, š 40%, v 20%, Table 1 Outline of experiments Micro structure Durability Corrosion Experiments Specimen & size Age of measuring (days) Internal chloride contents (% of binder) Remark SEM XRD Compressive strength Air contents Chloride binding capacity ANC RCPT Corrosion potential Concrete, Φ mm Concrete, Φ mm Concrete, Φ mm Concrete, Φ mm Cement paste, mm Cement paste, mm Concrete, Φ mm Mortar, Φ mm 7 - Piece collection 7 - Powder collection 7, 28, , 28, 56-7, 28, 56 After 200days later 9 level (0.1 to 3.0) - Casting condition Powder collection Powder collection level (0 to 3.0) - Table 2 Chemical composition of various binder CaO SiO 2 Al 2 O 3 MgO Fe 2 O 3 SO 3 K 2 O Na 2 O Mn 2 O 3 TiO 3 OPC PFA GGBS SF w gj pwz 20«4y (2008)

3 ev 10%» w w y j ƒ yy ƒ y d w. / p 40%, gj p r k r w d x w t 1 : 2.45 w. w Table œ x yw w z, w ƒw gj p 5 y wwš d x œ Φ mm k w, t ( 20 o C, 60%) 1 w 20 ± 2 C o 7, 28, 56 w gj p x (KS L 2405) d w. 2.3 pr p š y x» w n w 9 (0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 % of binder) y ü y mw, ƒ x y w» w d w š y y x mw d y w w. OPC, PFA, GGBS SF ƒƒ 3.12, 2.19, , w pr p r ƒ yw w š ƒ wš 0.4 / w ƒx ( mm) w. NaCl yw w 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0% w. w 2-4) y j» w 24 6rpm r z g. kx z, r s p v w š 6 20 ± 1 C o w. kxw r ü wš 105 ± 5 C o 5 w. r w z 300 µm ƒ w w. z 50 C o 5 w w w. z, 30» vl w Table 3 Ternary blended concrete mix OPC GGBS SF OPC GGBS PFA OPC SF PFA Binder Content (%) W/B (%) Water (kg/m 3 ) Binder contents (kg/m 3 ) Fine aggregates (kg/m 3 ) Course aggregates (kg/m 3 ) OPC ,106 GGBS ,100 SF GGBS ,102 SF GGBS ,106 SF GGBS ,091 PFA GGBS ,097 PFA GGBS ,103 PFA SF ,078 PFA SF ,078 PFA SF ,078 PFA ywgj p y en w ü w š 441

4 액을 추출하였고, 추출용액은 질산은 적정법에 의한 전 위차 적정기를 사용하여 세공용액상의 자유 염소이온농 도로 각 1회씩 측정하였다. 2.4 삼성분계 시멘트페이스트의 산중성화 저하 특성 콘크리트 내 철근은 부동태 피막으로 둘러싸여 있으나 산소 및 수분의 공급이 원활한 상태에서 콘크리트내로 침투되는 염소이온 및 탄산화로 인해 부동태 피막을 파 괴시키며 종국적으로 콘크리트 내 철근의 부식을 일으킨 다. 한편, 철근 표면의 공식 (pitting corrosion)에 의해 발 생되는 전기화학적 반응에 의한 수소이온의 증가는 철근 주위의 ph를 저하시키고 철근의 부동태 피막을 파괴하 여 철근부식의 주요 원인으로 지적되고 있는 실정이다. 따라서 이에 대한 대책으로써 수산화칼슘 및 CSH gel과 같은 알칼리성 시멘트 수화물의 영향에 따른 부식 제어 방안이 논의되고 있으나, 개념적 접근만 있을 뿐 대부분 의 철근부식에 관한 연구는 시멘트 수화물의 부식 억제 능력에 대하여 이를 고려하고 있지 않다. 부식의 진행 과정에 있어서 시멘트 수화물의 영향은 산중성화 능력 (acid neutralization capacity)실험으로 측 정할 수 있으며, 시멘트 성분에 따른 ph 감소에 대한 저 항성을 측정지표로 사용한다. 즉, 매트릭스 내 수화생 성물의 중성화 방지 저항성을 통해 부동태의 중성화 속 도를 지연시킬 수 있으며, 이는 삼성분계 시멘트 등 결 합재의 종류에 따라 각기 다른 수화 속도 및 수화생성 물을 발생시켜 중성화 저항성에 있어서 고유의 저항 능 력을 형성시킨다고 할 수 있다. 본 연구에서는 산중성화 능력에 따른 부식 저항성을 평가하고자 염소이온 고정화 능력 실험과 동일한 시편이 나 염분이 함유되지 않은 시멘트페이스트 시편을 재령 200일이 경과한 후 분말 형태로 분쇄한 후 5 g을 채취하 였다. 이와 동시에 50 ml의 필터링 용액으로 치환 교반하 여 질산용액의 단계별 누적 첨가 (2.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 35, 40 및 45 ml)에 따른 ph 변화를 ph meter에 의한 전위차 측정기를 통해 산중 성화 저항성으로 계산하였다. 5,6) 2.5 linear polarization 방법에 의한 철근의 부식전위를 측정을 수행하였다. 시험시편은 [OPC]와 [90OPC + 10SF], [70OPC + 30PFA], [40OPC+60GGBS]의 경우와 [ + 35GGBS + 15SF], [ + 40GGBS + 10SF], [ + 45GGBS + 5SF], 1[ + 20GGBS + 30PFA], [ + 30GGBS + 20PFA], 1[+40GGBS+10PFA], [+15SF+35PFA], [ + 15SF + 35PFA]로 구성되며, 물/시멘트비 40%의 모르타 르 시편을 제작한 뒤 재령 28일째 부식전위 측정을 실 시하였다. 또한, 사용배합의 경우는 Table 3에 따른 굵은 11-25) 골재 부분을 제외한 모르타르 배합법에 의거하여 타설을 수행하였다 실험 결과 및 분석 미세구조 관찰 결과 일반적으로 시멘트의 수화진행 과정에서 CSH gel의 경 우는 70~80%, Ca(OH) (이하 CH로 표기)는 20~25%, 칼슘 설포네이트가 5%의 비율을 차지하며, 에트린자이트의 경 우는 극미하게 검출되는 것으로 알려져 있다. Fig. 1에 각종 삼성분계 혼합콘크리트의 초기재령 7일에서의 SEM 으로 관찰한 수화생성물과 그의 조직 사진을 나타내었다. 여기서, [ + 35GGBS + 15SF]의 경우는 전형적인 CH 를 보여주고 있으며, [ + 40GGBS + 10SF]의 경우는 칼슘설포네이트를 나타내고 있다. 또한 [ + 40GGBS + 10 PFA]의 경우에는 CSH gel을 나타내고 있다. 한편 Fig. 2 그림에서는 XRD 분석에 의한 [ + 45GGBS + 5SF]의 수화생성물 분포를 관찰하였다. 결정 2 삼성분계 혼합콘크리트의 염분 침투 특성 염소이온 확산계수 도출 및 침투깊이 측정을 위한 시편 의 배합은 강도측정용 공시체와 동일하게 수행하여 삼성분 계 콘크리트의 염소이온 침투 특성을 평가하였다. 실험을 통한 확산계수의 추정은 Berke 등이 ASTM C 1202 시험 결과의 총 통과전하량과 농도차 확산시험 결과로부터 얻은 경험식을 적용하여 콘크리트의 확산계수를 도출하였다. 7-10) 2.6 삼성분계 혼합 모르타르의 부식 특성 철근부식에 대한 저항성을 파악하고자 본 연구에서는 442 한국콘크리트학회 논문집 제20권 제4호 (2008) Fig. 1 SEM image of ternary blended concrete

5 Fig. 2 XRD result of +45GGBS+5SF CH C 3 Sƒ wš, p 27 o 28 o CH C 3 S vjƒ ùkûš, y» w r y y w. 3.2 w p Fig. 3 w p 50% š wš 45% 20%, v 45% 10%, ev 15% 5% j yw gj p d w ùkü. 7 x [ + 40GGBS + 10SF] ƒ 24.1 MPa d w ùkü š y w š, [ + 5SF + 45PFA] ƒ 13.9 MPa ùkû. wr, 28 [ + 40GGBS + 10SF] ƒ 31.6 MPa š ùkû y w. w 56 [ + 40GGBS + 10SF]ƒ x ùkû 45% š 5% ev y w, ey mw y w z x xw y w. p, yw gj p OPC w» d ù, ev v yww ƒw w š ƒ ùkù ev v y w d OPC y w. wr Fig. 4 ywgj p w œ» d ùkü. œ» y r [ + 40GGBS + 10SF] ƒ œ» 2.7% ùkù w œ ƒ j ùkû. [ + 15SF + 35PFA] œ» 1.1% ùkû ev ƒ œ z w ü š w. 3.3 š y Fig. 5,, yw pr p š y w v w. 9 y ü y š y 3) Langmuir isotherm txw, x l» 7 š y [ + 5SF + 45PFA] > [ + 45GGBS+5SF] > [ + 10SF + 40PFA] > [40OPC + 60GGBS] > [90OPC + 10SF] > [ + 30PFA + 20GGBS] > [70OPC + 30PFA] >[OPC] ùkù š y eyz ƒ OPCù w w y Fig. 4 Air contents of ternery blended concrete Fig. 3 Compressive strength of ternery blended concrete Fig. 5 Binding capacity of ternary blended concrete ywgj p y en w ü w š 443

6 w.» 3-6) l š y w ƒw š y y en j š y ywgj p ƒ k w mw ü d šü gj p w z ƒ y ƒ w, yy š y z ƒ w. 3.4 y w p Table 4 y w w sƒ w w yw pr p ƒ w ph w p w. x mw š v yw w ƒ e v sww pr p w y w ùkû. Fig. 6 ph w y w w. l ƒ yw pr p ü, ƒw ph w ù, ƒ w ph ƒ y w, 21 mol/kg w ph OPC > SF > PFA > GGBS ùkùš y w. Fig. 6 ƒ š, ev v eyw x w,» ph 12.6 d ph ƒ y w ƒƒ ph 12.4, ph 12.2 ph 11.5 vj(peak) ƒ ùküš š, p y w ye w ph w w ùkü H + Fig. 6 ANC (acid neutralization capacity) test result w ww ùkü v š w. [OPC],[ + 40GGBS + 10SF],[ + 30GGBS + 20PFA], [ + 10SF + 40PFA],[40OPC + 60GGBS],[90OPC + 10S F], [70OPC + 30PFA] ƒ v y w ùkû y w [Cl : OH] tx [Cl : H] d ƒ w ù ký y w. w, ƒ w w ƒ ph w w q š w, OPC > [90OPC + 10SF] > [70OPC + 30PFA] > [40OPC + 60GGBS] > [ + 10SF + 40PFA] > [ + 35GGBS + 15SF] > [ + 20GGBS + 30PFA] > [ + 40GGBS + 10SF] > [ + 45GGBS + 5SF] > [ + 30GGBS + 20PFA] > [ + 40GGBS +10PFA] ùkû y w. w y w w ü ph Table 4 ph reduction test results 35GGBS + 15SF 40GGBS + 10SF 45GGBS + 5SF 20GGBS + 30PFA 30GGBS + 20PFA 40GGBS + 10PFA 10SF + 40PFA w gj pwz 20«4y (2008)

7 w k v q j OPC ƒ y w w ƒ j d j z ƒ ƒ j š»w,» š y x gj p w w ü sƒ üá e n, yy ey, gj p y w w ƒ w. 3.5 en p y en¾ d w r w d œ w w w gj p en p sƒ w. x mw y Berke (1994) ASTM C 1202 x m w y x l x ( (1)) w gj p y w. D = Q total ( ) 0.84 m 2 /s ( ) x mw en¾ y ty w Table 5. (1) Table 5 x l yw gj p OPC gj p m w { û en û. p [ + 30GGBS + 20PFA] m w OPC gj p w Berke y x w w y d 2.69 y z ùkü, š v yy ey w y w e n j w ƒ ywgj p w d w q. wr, y š w, [OPC + GGBS + PFA] > [OPC + SF + PFA] > [OPC + GGBS + SF] m w y z ƒ š y w. y en GGBS PFA w ƒ w w š w, ey d [+30GGBS+20PFA] w w w q. w x mw ywg j p w 56 ƒ r m w 3,000 i OPC w w en û ùkù z w y ywgj p w gj Table 5 ASTM C 1202 test results Specimen Chloride penetration depth (mm) Total passed charges Diffusion coefficient Avg. (Coulomb) (10-12 m 2 /s) OPC GGBS SF 40GGBS SF 45GGBS SF 20GGBS PFA 30GGBS PFA 40GGBS PFA 15SF PFA 10SF PFA 5SF 45PFA ywgj p y en w ü w š 445

8 p y w q. 3.6 w sƒ yw k r 10 ü (0, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0% of binder) y y w x ww. k r 50 mm, 100 mm x œ r w, x d w w wš 20 mm, w 10 mm t gq ww x w d w d y w. Fig. 7 x l, š ƒ w e. p, š y w 0.5% w w wù, ƒ w w j. š k r ü œ e w w, w w ww ù w w. wù ùkü, š w w w y û. ù w ù» w w wƒ j w e w. w š w k y w, j, y» w. y ƒ w w w e w. wr, y, y tx y w w» w w ƒ v w. xš w k t 275 mv vs. SHE, 275 mv corrosion potential w y w ) Fig. 7» w w» mw ƒ w. š y š, w ƒ w y Table 6 ùkü. 10 ü y mw yw k r e [90OPC+10SF]>[OPC]>[40OPC+60GGBS]> [70OPC + 30PFA] > [ + 40GGBS + 10PFA] > [ + 45GGBS + 5SF] > [ + 40GGBS + 10SF]>[ + 5SF + 45PFA] ùkùš y w. Fig. 7 Linear polarization test result 446 w gj pwz 20«4y (2008)

9 Table 6 Chloride threshold level of ternary blended concrete Specimens CTL (%, binder) O P C OPC+30PFA OPC+60GGBS OPC+10SF GGBS+15SF GGBS+10SF GGBS+5SF GGBS+30PFA - +30GGBS+20PFA - +40GGBS+10PFA SF+35PFA - +10SF+40PFA - +5SF+45PFA ywgj p wü sƒ mw yw gj p ü w ty w Table 7. d SEM XRD d y q» yw, OPC» k y ywgj p y CSH gel CH, CS p p s w. p, y ƒ w ey y wz w w xkƒ OPC w w úe x y w š gj p wš p p ü z šü gj p w y ƒ w š w. wr, ü p d 7, 28, 56 gj p gj p w OPC w ù w ù, ev v ey y ww w OPC ƒ w š d ùkû. w, gj p k œ» x mw OPC gj p gj p œ w sƒw [ + 40GGBS + 10SF] [ + 30GGBS + 20PFA] w wš OPC œ» ùkù šü d y w š w. w, š yd p r p w w OPC š y w ùkù p w y w œ g w k w, w» d w t y w x l ph w y w w OPCƒ w w w ùkù š y x. wr, y en x mw d y d, w OPC m w y ƒ w y w š y ƒ w ƒ w. d w w d x x w w, t y» 275 mv Table 7 Durability assessment of ternary blended concrete Binder Micro structure Durability character Corrosion character SEM XRD Compressive strength Air content Chloride binding capacity ANC RCPT Corrosion potential OPC C 1) C C C C C C C C 60OPC+40GGBS OPC+30PFA OPC+10SF GGBS+15SF GGBS+10SF GGBS+5SF - - 2) +20GGBS+30PFA GGBS+20PFA GGBS+10PFA SF+35PFA - - 3) - +10SF+40PFA SF+45PFA - - Note 1) Control specimen, Note 2) : Higher than OPC, Note 3) : Lower than OPC CTL ywgj p y en w ü w š 447

10 » k ƒ w y w, w OPC û y ƒ. y mw yw k w OPC w û, d š y wgj p y w š w. ù š z š y y y y, en w d» ü z» w q. 5. msp p 50% ey š w z, š 20~40%, ev 5~15%, v 10~45% eyw gj p y en w w ü p w š yy w w gj p ü z wz w w. 1) ywgj p w gj p, œ» d OPC w gj p ùkû, y wgj p OPC š, v ev y w gj p, Ÿ y y x s y wš, w ywgj pƒ OPC ƒ œ z ƒ» q. ù ev v y w d OPC û ƒ ùkù» x w š gj p d w w w. 2) š y d pr p w w OPC š y w ùkû. w œ j w w. 3)» d w t y w x l ph w y w w OPCƒ w w w ùkù š y x ùký. 4) yw gj p OPC gj p m w { û en û q. p, ywgj p w gj p 56 z m w 3,000 i en û ùkù, z w y ywgj p w gj p y w. 5)»yw x, ywgj p w gj pƒ OPC w gj p ƒ ùkù w d wù š y y w ü z» w. mr&d Á v» t y, gj p g (Concrete Corea) z» sƒ (ISARC). š x 1. Song, H. W., Kim, H. J., Saraswathy, V., and Kim, T. H., A Micro-Mechanics Based Corrosion Model for Predicting the Service Life of Reinforced Concrete Structures, Int J Electro Sci., Vol. 2, 2007, pp. 341~ Arya, C., Buenfeld, N. R., and Newman, J. B., An Assessment of Four Methods of Determining the Free Chloride Content of Concrete, Mater Struct., Vol. 23, 1990, pp. 319~ Song, H. W., Ann, K. Y., Lee, C. H., and Jung, M. S., Chloride Binding Isotherms in Cement Paste Containing Various Binders, 2006 Life Cycle Management of Coastal Concrete Structues Conference, Nagaoka, Japan, Nov. 2006, pp. 109~ Song, H. W., Lee, C. H., and Ann, K. Y., Prediction of Chloride Profile Considering Binding of Chlorides in Cement Matrix, International Corrosion Engineering Conference, May, 2007, pp.139~ Song, H. W., Lee, C. H., Jung, M. S., and Ann, K. Y., Development of Chloride Binding Capacity in Cement Pastes and the Influence of the ph of Hydration Products, Can Civ Eng J., In Press, Song, H. W., Jung, M. S., and Ann, K. Y., Resistance of Cementitous Binders Against a Fall in the ph at Corrosion Initiation, International Corrosion Engineering Conference, May, 2007, pp. 144~ Berke, N. S. and Hicks, M. C., Predicting Chloride Profiles in Concrete, Corr Eng., Vol. 1, 1994, pp. 234~ Collepardi, M., Marcialis, A., and Turriziani, R., The Kinetics of Penetration of Chloride Ions into the Concrete, II Cement, 2nd Edition, Clarendon Press, Oxford, 1975, 21 pp. 9. Song, H. W., Lee C. H. and Ann, K. Y., Factors Influencing Chloride Transport in Concrete Structures Exposed to Marine Environment, Cem Concr Comp., Vol. 30, Issue 2, pp. 113~ Thomas, M. D. A., Matthews, J. D., and Haynes, C. A., Chloride Diffusion and Reinforcement Corrosion in Marine Exposed Concretes Containing PFA, In: Corrosion of 448 w gj pwz 20«4y (2008)

11 Reinforcement in Concrete, Warwickshire, UK, 1990, pp. 198~ Andrade, C., Castelo, V., Alonso, C., and Gonzalez, J. A., The Determination of the Corrosion Rate of Steel Embedded in Concrete by Polrization Resistance and AC Impedance Methods, In: Corrosion Effect of Stray Currents and the Techniques for Evaluating Corrosion of Rebar in Concrete, V. Chaker, eds., ASTM STP 906, 1986, pp. 46~ Ann, K. Y., Song, H. W., Lee, C. H., and Lee, K. C., Buildup of Surface Chloride and Its Influence on Corrosion Initiation Time of Steel in Concrete, EASEC-10, The Tenth East Asia-Pacific Conference on Structural Engineering & Construction, Bangkok, Thai, Aug. 3-5, 2006, pp. 767~ Broomfield, J. P., Corrosion of Steel in Concrete-Understanding, Investigation and Repair, E&FN Spon, 1997, pp. 222~ Cady, P. D., Corrosion of Reinforcing Steel, Significance of Tests and Properties of Concrete and Concrete Making Materials, STP-169B, ASTM, Philadelphia, 1978, pp. 275~ Hausmann, D. A., Steel Corrosion in Concrete, Mater Protection, Vol. 11, 1967, 19 pp. 16. Hope, B. B. and Alan, K. C., Chloride Corrosion Threshold in Concrete, ACI Mater J., Vol. 43, 1987, pp. 306~ Schiessl, P. and Breit, W., Local Repair Measures at Concrete Structures Damaged by Reinforcement Corrosion, Proceedings of the Fourth International Symposium on Corrosion of Reinforcement in Concrete Constructionm, Cambridge, 1996, pp. 525~ Song, H. W., Ann, K. Y., Lee, C. H., and Lee, K. C., Corrosion of Steel in Mortars Containing OPC, PFA, GGBS and SF with Chlorides in Cast, The 4th Civil Engineering Conference in the Asian Region, Taipei, Taiwan, Jun. 25~ , pp. 80~ Song, H. W., Ann, K. Y., and Kim, T. S., Assessing the Resistance of Cementitious Binders to Chloride-Induced Corrosion of Steel Embedment Via Electrochemical and Microstructural Studies, International Corrosion Engineering Conference, May 20~24, 2007, pp. 149~ Saraswathy, V. and Song, H. W., Effectiveness of Fly ash Activation on the Corrosion Performance of Steel Embedded In Concrete, Mag Concr Res., Accepted, Saraswathy, V. and Song, H. W., Evaluation of Corrosion Resistance of Portland Pozzolana Cement and Fly Ash Blended Cements in Pre-Cracked Reinforced Concrete Slabs under Accelerated Testing Conditions, Mat Chemi Phy., Vol. 104, No. 2-3, 2007, pp. 356~ Song, H. W. and Saraswathy, V., Analysis of Corrosion Resistance of Inhibitors in Concrete Using Electrochemical Studies, Met and Mat Int., Vol. 12, No. 4, 2006, pp. 323~ Saraswathy, V. and Song, H. W, Electrochemical Studies on the Corrosion Performance of Steel Embedded in Activated Fly Ash Blended Concrete, Electrochimica Acta., Vol. 51, 2006, pp. 4601~ Saraswathy, V. and Song, H. W., Corrosion Performance of Fly Ash Blended Cement Concrete: A State of Art Review, Corros Rev., Vol. 24, No. 1-2, 2006, pp. 87~ Saraswathy, V. and Song, H. W., Performance of Galvanized and Stainless Steel Rebars in Concrete under Macrocell Corrosion Conditions, Mat Corros., Vol. 56, No. 10, 2005, pp. 685~ Song, H. W. and Ann, K. Y., Chloride Threshold Level for Corrosion of Steel in Concrete, Corros Sci., Vol. 49, 2007, pp. 4113~ Glass, G. K. and Buenfeld, N.R., The Presentation of the Chloride Threshold Level for Corrosion of Steel in Concrete, Corros Sci., Vol , pp. 1001~ Song, H. W., Ann, K. Y., Lee C. H., and Jung, M. S., Chloride Threshold Value for Stell Corrosion in Concrete Considering the Buffering Capacity against a Fall in the ph, ACI Mat J., In Press, Thomas, M. D. A., Chloride Thresholds in Marine Concrete, Cem and Concr Res., Vol. 26, No. 4, 1996, pp. 513~519. yy w ywgj p gj p t j ƒ w gj p» wš. ev (SF), š (GGBS), v (PFA) p w š gj p yy ƒ š ù, ywgj p w w, p w w w d w. msp p 50% ey š w z š 20~40%, ev 5~15%, v 10~45% eyw ƒ w w w w w x ww. ywgj p w w sƒw, w x w x, š y x, y x, y w x ww., gj p e y w j š y w. w, w w ywgj p ü š y y w j š y w w w w w. w : gj p, ü, y, y n, gj p w ywgj p y en w ü w š 449