micro structure chloride difussion

8/3/2019 Micro Structure Chloride Difussion

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ELSEVIER

C emen t & C o n cr e t e C o mp o s i t e s ! 6 ( 1 9 9 4 ) 7 3 - 8 1 1 9 9 4 E l s e v i e r S c i e n ce L i m i t e dPr in ted in Grea t Br i t a in . A l l r i gh t s reserved0 9 5 8 - 9 4 6 5 / 9 4 / S 7 . 0 0

M icros tru c tu re , C h lor id e D i f fu s ion an dR e i n fo r c e m e n t C o r r o s io n in B l e n d e d C e m e n t P a st ea n d C o n c r e t eE S. M ang at,* J. M . Khatib* & B . T. MolloyDep artm ent of Engineering, University of Aberdeen, Kings College, Aberdeen, UK(Received 8 Ma rch 1993 ; accepted 6 December 1993)

Abstrac tThis pap er presen ts som e resu lt s f ro m a w ide-ranging invest igation o f por osi ty an d pore -s truc-ture, chloride-dif fusion, and reinforcement-c o r ro s io n s tud i e s i n b l e n d e d c e m e n t p a s t e a n d c o n -crete . The cem en t - rep lace m ent mater ia ls used werep fa , s la g , an d micros il ica . Mercury- in trus ion-p o r o s im e t r y e x p e r im e n t s w e r e c ar r ie d o u t o n p a s t e swi th w/c o f 0 .45 . Chlor ide-d i f fus ion s tud ies andcorrosion invest igation on rebars we re carried ou tb y u s in g c o n c r et e m ix e s o f p r o p o r t i o n s b y w e ig h t1:2 .5:1 .2 a nd w/c o f 0 .58 . In a l l these exper imen ts ,in i t ial curing fo r a t least 14 days was un der rela-t i ve l y l o w - h u m id i t y e n v i r o n m e n t s i n s te a d o f i d ea -l ised wet curing.

The resul ts sh ow tha t micros i lica cem en t pas teshave a larger pore vo lum e than o ther pas tes use d inthe investigation. The chloride pene tration, ho w-ever , i s the m in im um in s i l i ca-fume concre te . Thech lor ide-b ind ing capac i ty o f p fa concre te i s l e ssthan tha t o f nor m al concre te in the surface zone ,but , at a greater dept h (> 20 mm ), the bin dingcapac i ty o f p fa concre tes exceeds tha t o f p la inconcrete. The results generally in dica te a highercorrosion act iv i ty o f re info rcem ent with increasingchlor ide concen tra t ion in the pore flu id . M icro-si lica w as by far the m os t e f fect ive cem ent-rep lace-m en t m aterial in increasing the corro sion resis tanceo f re in forcem en t in concre te .

*To whom correspondence should be addressed at: Schoolof Construction, Sheffield Hallam University, Pond Street,Sheffield S 1 1WB, UK.~Department of Civil Engineering, Glamorgan University,Pontypridd, UK.~Mentor Project Engineering, Blackness Road, Aberdeen,UK.

Key words: b l e n d e d c e m e n t s , c o r r o si o n , c o n c r e t edurab i l i ty , poros i ty , ch lor ide d i f fus ion , cor ros ionpoten t i a l , f ly ash , s l ag , s i l i ca fume, mercury poro-s imet ry .I N T R O D U C T I O NC e m e n t r e p l a c e m e n t m a t e r i a l s a r e k n o w n t oi m p r o v e t h e d u r a b i l i t y o f c o n c r e t e . P o r o s i t y i sd e e m e d t o b e r e d u c e d a n d p o r e s iz e t o b e re f in e d ,w h i c h t h u s h i n d e r s t h e m o v e m e n t o f ag g r e ss iv es u b s t a n c e s s u c h a s c h l o r i d e i o n s a n d c a r b o nd i o x i d e , w h i c h a r e r e s p o n s i b l e f o r t h e c o r r o s i o no f r e i n f o r c e d - c o n c r e t e s t r u c tu r e s . A c o n s i d e r a b l ea m o u n t o f w o r k h a s b e e n c o n d u c t e d o n t h e in -f l u e n c e o f c e m e n t - r e p l a c e m e n t m a t e r i a l s o n t h ed u r a b i l i t y o f b l e n d e d c e m e n t s y s te m s . l , 2I t i s r e p o r t e d b y s o m e r e s e a r c h e r s t h a t 3 0 %r e p l a c e m e n t o f c e m e n t w i t h p f a r e s u l t e d i n ah i g h e r i n t r u d e d p o r e v o l u m e b u t t h a t t h e p o r e -s ize d i s t r ibu t ion was f iner . S imi la r r esu l t s wereo b t a i n e d a t 2 0 % r e p l a c e m e n t l e v e l ) ,4 O t h e r s h a v er e p o r t e d t h a t a 3 0 % r e p l a c e m e n t l e v e l o f p f ai n c r e a s e s t h e p o r e v o l u m e a t t h e a g e o f 2 8 d a y s ,b u t a s i m i l a r v o l u m e t o t h a t o f o r d i n a r y c e m e n tp a s t e w a s o b t a i n e d a t t h e a g e o f o n e y e a r . 5G r o u n d g r a n u l a t e d b l a s t - f u r n a c e s l a g a t a r e p l a c e -m e n t l e v e l o f 4 0 % r e d u c e s t h e p o r e v o l u m e a n dp o r e s iz e c o m p a r e d w i t h p a s t e w i t h o u t s la g )A d d i n g m i c ro s il ic a ( 0 - 1 6 % ) t o a c e m e n t p a s t el e a d s t o a r e f i n e m e n t o f p o r e s t r u c tu r e . 7 M o s tr e s e a r c h w o r k c a r r i e d o u t o n p o r o s i t y a n d p o r e -s i z e d i s t r i b u t i o n o f c e m e n t p a s t e a n d b l e n d e dp a s t e h a s a d o p t e d c u r in g m e t h o d s t h a t a ll o w th em a x i m u m h y d r a t i o n t o t a k e p l ac e . 4 A d o p t i n go t h e r i n i t ia l - c u r in g m e t h o d s b y e x p o s i n g s p e c i -m e n s t o r e l a t i v e l y l o w r e l a t iv e h u m i d i t y c a ng r e a t l y a f f e c t t h e p o r o s i t y a n d p o r e s t r u c t u r e o ft h e p a s t e )

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74 P. S. Mangat, J. M.A considerable volume of research has beenconducted in recent years to study the resistanceof hydraulic-cement-based materials to chlor ide

diffus ion. 2,9-12 This research has adopted bothaccelerated forms of testing by means of diffu-sion-cell techniques9,"~ and longer-term testinginvolving the use of more realistic chloride-exposure environments.~ 1. t 2 Tests on samples thatwere cured for 60 days at 22C in saturated air, toallow full hydration of the cement-blending mate-rials, have shown the potential of pfa and slag as ameans of reducing chloride diffusionY. "1 Initial aircuring after casting for fourteen days to simulatemore practical curing conditions, however.resulted in higher chloride uptake when 26% ofcement was replaced with pfa. ~t

Some recent work demonstrates the increasedcorrosion resistance of reinforcement in concretescontaining pfa or microsilica.2,13 The work isoften conducted on mixes in which pfa is used toobtain the same strength as for the control mix.This leads to a lower water/(cement + blend) ratioof the pfa mix, relative to the control plain-con-crete mix.The porosity and pore structure of concretewill influence directly the diffusion characteristicsof chlorides and other corrosion-inducing sub-

stances, and consequent ly it will control the initia-tion and rate of reinforcement corrosion. There is,however, little work done to confirm this rela-tionship in Portland-cement concretes and inconcretes containing blended cements. In the caseof blended cements, the effect on chloride diffu-sion of a cement-replacement material is notsimply the result of its effect on the physical pro-perties but also includes the chemical com-bination of chloride ions with the blended-cementmaterial. There is information available on thechemical effects, 14 but little work has beenreported to correlate the porosity and pore struc-ture of the paste to chloride diffusion in concreteand hence to reinforcement corrosion. This paperinvestigates this relationship between micro-structure, chloride diffusion, and corrosion resist-ance of reinforcement.

E X P E R I M E N T A L P R O G R A M M EP o r o s i t y a n d p o r e s t r u c t u r eFour different pastes were employed to inves-tigate the porosity and pore structure of blendedcements, details of which are given in Table 1. Thepastes were PA, in which ordinary Portlandcement was used and which formed the control

EI-Khat ib , B. 11 M o l l o yTable t . Details of pas te mixes for poros im etry s tudy

Pro portion (by weighO (%)Mix OPC* Pfa Microsi l ica Slag Water/ Superplast iciserbinder+ %

PA 100 -- -- -- 0'45 1"2PB 78 22 -- -- 0-45 1-2PC 91 -- 9 -- 0"45 1"5PD 60 -- -- 40 0"45 1"2* Ordinar y Port land cement .tBi nd er (cement i t ious material ) consis t ing of OPC andcement - rep lacement mate r ia l .

specimens, and PB, PC, and PD, which containedpfa, microsilica, and ground granulated blast-furnace slag, respectively. The water/cementitiousmaterials ratio was kept constant at 0.45. Super-plasticiser SP2000 was added to all pastes, whichis based on the sodium salt of a copolymer of anunsaturated carboxylic acid and its alkyl ester.15 Itconformed to Type F and G materials of ASTM-C494.

Cubes (100-ram) of paste shown in Table 1were cast in steel moulds at a room temperatureof 20C and relative humidity of 55%. Just beforewater on the top face (trowelled face) had evapo-rated, the surface was sprayed with a curingcompound, Curex 90, according to the manufac-turer's recommendations.~ After 24 h, specimenswere demoulded and the o ther five faces of eachcube were moistened before applying the curingmembrane. The specimens continued to be curedin air at 20C and 55% r.h. for a total period of 28days. At the end of this curing period, samples formercury-intrusion-porosimetry testing weretaken from the middle of the side face of eachcube. The weight of each test sample rangedbetween 0.8 and 2.5 g. The mercury-intrusion-porosimetry technique was employed to measurethe porosity and pore structure of the variouspastes. Data were computed by using the follow-ing Washburn equation t6 to determine the porediameter:

D = (46 cos O)/pwhere D is the pore diameter,p is the applied pressure,6 is the surface tension, which was takenas 486 dyn/cm, and0 is the contact angle, which was taken

as 142 Further details of the mercury-intrusion poro-simetry tests are given by Mangat and E1-Khatib. sCube strengths of the pastes were not deter-mined, but concrete cubes made with the same


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Properties of cement-replacernent materials 75w a t e r / c e m e n t i t i o u s m a t e r i a l s r a t i o o f 0 . 4 5 w e r et e s t e d a f t e r c u r i n g i n w a t e r a t 2 0 C f o r 2 8 d a y sa n d f o r 2 3 w e e k s . T h e m i x p r o p o r ti o n s , b y w e i g h to f c e m e n t : fi n e a g g r e g a t e : c o a r s e a g g r e g a te w e r e1 : 2 . 0 : 3 . 4 3 , w i t h a c e m e n t i t i o u s c o n t e n t o f 3 5 0k g / m 3. T h e s t r e n g t h s a f t e r 2 8 d a y s ' c u r i n g f o rm i x e s w i th c e m e n t - r e p l a c e m e n t l e v e l s o f 0 % , 2 2 %p f a , 4 0 % s l a g , a n d 9 % m i c r o s i l i c a w e r e 4 8 , 3 6 ,4 1 , a n d 4 8 N/mm 2, r e sp e c ti v e ly . T h e c o r r e s p o n d -i n g v a l u e s a f t e r 2 3 w e e k s ' c u r in g w e r e 5 3 , 4 7 , 5 4 ,a n d 6 2 N/ra m 2, r espec t ive ly .C h l o r i d e d i f f u s i o nT h e m i x e s u s e d f o r t h e c h l o r i d e - d i f f u s i o n i n v e s t i -g a t i o n a r e g i v e n i n T a b le 2 . T h e c o n t r o l m i xD 1 w a s o f p r o p o r t i o n s b y w e ig h t 1 : 2 . 5 : 1 . 2( c e m e n t : f i n e a g g r e g a t e : c o a r s e a g g r e g a t e ) w i t h aw a t e r / c e m e n t r a t i o o f 0 . 58 . T h e c e m e n t c o n t e n tw a s 4 3 0 k g / m 3, a n d n o c e m e n t - r e p l a c e m e n tm a t e r i a l s w e r e i n c o r p o r a t e d . I n m i x D 2 , c e m e n tw a s p a r t i a l l y r e p l a c e d b y 2 0 % p f a . I n m i x D 3 ,1 0 % o f c e m e n t w a s r e p l a c e d b y m i c r o s i l i c a ,w h e r e a s , i n m i x D 4 , 4 0 % o f c e m e n t w a s r e p l a c e db y b l a s t - f u r n a c e s l a g . T h e c e m e n t i t i o u s c o n t e n t( O P C + b l e n d i n g m a t e r ia l ) w a s k e p t c o n s t a n t a t4 3 0 k g / m 3, a n d t h e w a t e r / c e m e n t i t i o u s r a t io w a s0 " 5 8 . T h e c o m p r e s s i v e s t r e n g t h s o f t h e s e m i x e s ,a f te r c u r i n g u n d e r m a r i n e - s p r a y c y c le s f o r 5 2 0d a y s , a r e l i s t e d i n T a b l e 2 . T h e s e a r e s i m i l a re x c e p t f o r t h e s l ig h t l y h i g h e r v a l u e f o r t h e m i c r o -s i l ica mix.

P r i s m s p e c i m e n s o f 1 0 0 x 1 0 0 5 0 0 m m w e r ec a s t i n s t e e l m o u l d s a n d w e r e c o v e r e d w i t h a p o l y -t h e n e s h e e t . T h e s p e c i m e n s w e r e d e m o u l d e d a f t er2 4 h a n d w e r e l e ft t o c u r e u n d e r u n c o n t r o l l e dc o n d i t i o n s o f t e m p e r a t u r e a n d h u m i d i t y i n t h el a b o r a t o r y a i r f o r f o u r t e e n d a y s . T h e e n t i r e s u r -f a c e o f t h e p r i s m w a s c o a t e d w i t h b i t u m i n o u sp a i n t, a p a r t f r o m o n e 1 0 0 x 5 0 0 - r a m s i d e f a c e toa l lo w f o r c h l o r i d e p e n e t r a t i o n d u r i n g e x p o s u r e t oa c h l o r i d e e n v i r o n m e n t . T h e b i t u m i n o u s p a i n tT a b l e 2. Details of mixes used for chloride-diffusion andcorrosion-resistance studiesMix Binder Cem ent- Water / Comp ress ivecontent replacement binder s trength(kg /m-~) mater ial (%) (N /mm 2) D1 430 -- 0-58 35D2 430 Pfa (20%) 0-58 36D3 430 Microsilica (10%) 0-58 40D4 430 Slag (40%) 0.58 36*Equivalent cube strength after 520 days of marine-spray-cycle curing.

e f f e c t i v e l y s e a l e d t h e s u r f a c e s a g a i n s t c h l o r i d ep e n e t r a t i o n . A f t e r f o u r t e e n d a y s o f in i t i a l c u r i n g ,s p e c i m e n s w e r e t r a n s f e r r e d t o a l a b o r a t o r y s e a -w a t e r s p r a y c h a m b e r , w h i c h p r o v i d e d t w o w e t a n dt w o d r y c y c l e s i n e v e r y 2 4 h , s i m u l a t i n g t i d a l - z o n ee x p o s u r e . A f t e r 5 2 0 d a y s o f m a r i n e c y c l e s , t h ec h l o r i d e c o n t e n t s a t d i ff e r e n t d e p t h s i n t o c o n c r e t es p e c i m e n s w e r e m e a s u r e d b y u s i n g t w o t e c h -n i q u e s : d r y d r i l l i n g t o o b t a i n p o w d e r s a m p l e s ,w h i c h w e r e a n a l y s e d c h e m i c a l l y , t h e i r c h l o r i d ec o n c e n t r a t i o n b e i n g r e f e r r e d t o a s a c i d - s o l u b l ech lor id e , 11 an d che m ica l ana lys i s of p ore f lu ide x p r e s s e d f ro m c o n c r e t e u n d e r h i g h p re s s u r e a n dr e f e r r e d t o a s f r e e - c h l o r i d e c o n c e n t r a t i o n . 17F u r t h e r d e t a i l s o f t h e t e s t p r o c e d u r e a n d o f a c i d -s o l u b l e - c h l o r i d e a n a l y s i s a r e g i v e n in R e f . 1 1 . T h ec h l o r i d e w a s e x t r a c t e d f r o m p o w d e r s a m p l e s b yh e a t i n g i n d i l u t e n i t r i c a c i d . O n c o o l i n g , t h e s o l u -t i o n w a s fi l te r e d , a n d a M o h r t i t r a t i o n w a s c a r r i e do u t . T h e c h l o r i d e c o n c e n t r a t i o n w a s d e t e r m i n e df r o m t h e f o l l o w i n g e x p r e s s i o n : ~

3 5 . 4 5 3 v N% C 1 - - 1 0 ww h e r e N i s t h e n o r m a l i ty o f A g N O 3 ,v i s t h e v o l u m e o f Ag NO 3, a n d

w i s t h e m a s s o f t h e p o w d e r s a m p l e i ng r a m s .T h e t e s t p r o c e d u r e f o r p o r e - f l u i d e x t r a c t i o na n d i t s c h e m i c a l a n a l y s i s a r e d e s c r i b e d i n R e f. 1 7 .T h e s m a l l q u a n t i t y o f e x t ra c t e d p o r e f l u id w a sa n a l y s e d b y m i c r o t i t r a t i o n . A s o l u t i o n o f d i l u t ep o r e f l u i d , p o t a s s i u m d i c h r o m a t e i n d i c a t o r s o l u -t i o n , a n d b o r a x w a s t i t r a t e d a g a i n s t 0 " l s AgNO 3t o d e t e r m i n e t h e f re e C 1 - c o n c e n t r a t i o n o f th e

por e fluid. 17

C o r r o s i o n r e s i s t a n c eM i x e s D 1 , D 2 , D 3 , a n d D 4 , w h i c h w e r e u s e d t os t u d y c h l o r i d e d i f f u s i o n , w e r e a l s o e m p l o y e d t os t u d y t h e c o r r o s i o n r e s i s t a n c e o f s t e e l r e i n f o r c e -m e n t i n t h e s e m i x e s . T h e s a m e i n i t i a l - c u r i n gm e t h o d ( a f o u r t e e n - d a y a i r - c u r i n g ) a s i n t h ep r e v i o u s s e c t i o n w a s u s e d i n t h i s c a s e . T h e s p e c i -m e n s w e r e t h e n e x p o s e d t o u p t o 1 2 0 0 m a r i n ec y c l e s i n t h e s e a w a t e r s p r a y c h a m b e r o v e r 6 0 0d a y s .O n e p r i s m s p e c i m e n o f d i m e n s i o n s 1 0 0 x

1 0 0 x 3 7 0 m m w a s c a s t f o r e a c h o f t h e a b o v em i x e s , w i t h t h r e e r e p l i c a t e r e b a r e l e c t r o d e sp o s i t io n e d a t a c o v e r o f 1 0 m m f r o m t h e s id e f ac eo f t h e p r i s m r e l a t i v e t o i t s c a s t i n g p o s i t i o n a s


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7 6 P. S . M anga t , J . M . EI -Kha t ib , B . T . M ol l ovs h o w n i n F i g . 1 . T h i s s i d e f a c e o f t h e p r i s m w a sk e p t u n s e a l e d d u r i n g i t s p e r i o d o f m a r i n e e x p o -s u re , w h e r e a s t h e r e m a i n i n g f a c e s w e r e s e a l e dw i t h a b i t u m i n o u s p a i n t . T h e e l e c t r o d e s w e r elabel led T ( top) , M (middle) , or B (bot tom), refer -r ing to the i r pos i t ion r e la t ive to the top face of thes p e c i m e n d u r i n g c a s t i n g . D e f o r m e d r e i n f o r c e -m e n t b a r s o f 1 2 - m m d i a m e t e r w e r e u s e d a se l e c t r o d e s i n 3 6 0 - m m l e n g t h s . F u r t h e r d e t a i l s o ft h e s p e c i m e n s a r e g i v e n in R e f . 1 2 .C o r r o s i o n p o t e n t i a l , E c, a n d p o l a r i s a t i o n r e s i st -a n c e , R p , w e r e m e a s u r e d b y u s in g a p o t e n t i o s t a ta p p a r a t u s . D e t a i l s o f t e s t p r o c e d u r e s a r e g i v e n i nRef. 18.

M a t e r i a l sO r d i n a r y P o r t l a n d c e m e n t , f in e a g g r e g a t e o f C a t e -g o r y M o f B S 8 8 2 , a n d c r u s h e d - g r a n i te c o a r s ea g g r e g a t e o f n o m i n a l s i z e 1 0 m m w e r e u s e d .D e f o r m e d h i g h - y i e l d - s t e e l r e i n f o r c i n g b a r s o f 1 2 -m m d i a m e t e r w e r e u s e d , w h o s e c h e m i c a l c o m -pos i t ion i s g iven in Table 3 . P fa was suppl i ed f romt h e L o n g a n n e t p o w e r s t a t i o n n e a r E d i n b u r g h .B l a s t - f u r n a c e s l a g w a s s u p p l i e d b y B l u e C i r c l eL t d . M i c r o s i l i c a w a s s u p p l i e d b y E l k e m C h e m i -c a l s L t d i n t h e f o r m o f a s l u r r y o f e q u a l p r o p o r -t i o n s o f s o l i d s a n d w a t e r . T h e c h e m i c a lc o m p o s i t i o n o f t h e c e m e n t a n d r e p l a c e m e n t m a t e -r i a ls i s g iven in Table 4 .

I00 x1OO.5OOmmprism mould100,100mm / - ' " ~

p ersp ex I o cato rs . - ' " ] \\ ~ - ] ~ f ~ e l ec t ro d es. . . . . . , , oowre~ ~ m m . m /r . . . . ~. . . - ~ / "

i ( T I . T - - ~~ / . . .. . . z /L (M_!~]...- . /....... (B~" Y ' - . . ~ /Bracnqframe ~

~ v o i d ork -i~ 2 ~ . . . . . . fi0nwresFig . 1 . De ta i l s o f c o r ro s io n - t e s t sp e c ime n .

R E S U L T S A N D D I S C U S S I O N SP o r o s i t y a n d p o r e s t r u c t u r eT h e i n t r u d e d p o r e v o l u m e o f t h e v a r i o u s p a s t e sc o n s i d e r e d i n t h is i n v e s t i g a t io n i s p r e s e n t e d i nTable 5 . I t i s c l ear tha t the micros i l i ca pas tep o s s e s s e s t h e l a r g e s t i n t r u d e d p o r e v o l u m e o f t h ep a s t e s , t h e v a l u e b e i n g 0 . 2 0 2 8 c m 3 / g . T h i s i sf o l l o w e d b y p f a b l e n d e d p a s t e , w h i c h y i e l d e d a ni n t r u d e d p o r e v o l u m e o f 0 . 1 9 5 3 c m 3 / g . T h ei n t r u d e d p o r e v o l u m e o f t h e s la g b l e n d e d p a s t e ,h o w e v e r , i s 0 . 1 6 5 5 c m 3 /g , w h i c h i s m o r e t h a n t h a to f th e c o n t r o l p a s t e , w h i c h i s 0 .1 4 6 2 c m 3 /g .T h e p o r e - s i z e d i s t r i b u t i o n o f p a s t e s P A , P B ,P C , a n d P D i s s h o w n i n F i g . 2 . T h e p o r e s a r ed i v i d e d i n t o l a r g e p o r e s , w h o s e d i a m e t e r i sg r e a t e r t h a n 0 . 1 / ~ m , a n d s m a l l p o r e s o f d ia m e t e r

T a b l e 3 . C h e m i c a l c o m p o s i t i o n o f 1 2 - m m - d i a m e t e r H . Y . r e i n fo r c i n g b a rE l e m e n t C S i M n P h S C r M b N i C u V n

(%) 0 '15 0 '21 0"81 0-011 0"035 0"04 0 '02 0"06 0"06 0 '00 4

T a b l e 4 . C h e m i c a l c o m p o s i t i o n o f o r d i n a r y P o r t la n d c e m e n t ( O P C ) a n d c e m e n t - r e p l a c e m e n t m a t e r ia l sO PC Pfa Slag Microsil ica

(SiO2) (%) 2 0 .4 48 ' 0 36"0 92 .0(A1203) (%) 4.8 9 38.2 9.0 (1.7(Fe203) (%) 3.18 4.5 1.0 1.2(CaO) (%) 64 .02 3"3 43 .0 0 .2(Mg O) (%) 2-56 1-5 7.0 0.2(Na2 0) (%) 0 '07 0-3 1-0 2 .0(K20 ) (%) 0"53 1 .7(TiO2) (%) 1.3(So 42 - ) (% ) 0 .44(s 2- ) (%) 1.0Lo ss on igni t ion (%) 0"98 2-3S u r f a c e a r e a ( m Z/ kg ) 3 6 7 . 7 6 3 0 0 - 6 0 0 3 0 0 - 5 0 0 1 5 0 0 0 - 2 0 0 0 0


5/9

Pr o p e r t ie s o f c e me n t - r e p l a c e me n t ma t e r i al s 77l e s s than 0 .1 /~m, which a re p resented in Tab le 5 .F i gu r e 2 s ho w s t ha t t he p fa b l e nde d p a s t e ha s ac o a r s e r p o r e s t r u c t u re a n d a l a r ge r do mi na n t p o r es ize . The dominant pore s izes co r re sponding tothe m axim um inc rem enta l v o lume , d V, in F ig . 2a r e a b o u t 0 . 51 / a m fo r t he p fa b l e nde d p a s t e a nd0" 2 3 / a m fo r t he c o n t r o l p a st e . T he p r o p o r ti o ns o fla rge pores a re 68 .3% of the to ta l in t ruded porevo l u me fo r t he p fa b l e nde d p a s t e a nd 52 . 4% fo rthe cont ro l mix (Tab le 5) . The dominant pores izes o f mic ros i l i ca pas te and cont ro l pas te a re

s imilar , as is the dominant pore s ize of the s lagb l e nde d p a s te . T he l a r ge p o r e s o c c u p y 70 . 6% a nd67 . 8% o f t he t o t a l i n t r u de d p o r e vo l u me i n t hemic ros i l i ca pas te and the s l ag b lended pas te ,respectively.Ch l or i d e d i f fu s ionAcid-soluble chlor ide-diffus ion profi les for mixesD 1 , D 2 , D 3 , a nd D 4 a f t e r 52 0 da y s o f e x p o s u re t om ar ine cyc les a re shown in F ig . 3 . I t can be seenthat the 10% microsi l ica mix (D3) exhibi ts the

Table 5. Pore volume of the pastesMix Pore volume (cm3/g)

Total Large Small Largevolu m e po res po res (>- 0"1 I~m )(> 0"1 ktm ) (< 0.11zm)

Pores (%)Small( < O .1/zm)

PA (control) 0.1462 0.0767 0.0695 52.4 47-6PB (22% pfa) 0-1953 0.1334 0.0619 68.3 31.7PC (9% microsilica) 0.2028 0"1432 0.0596 70.6 29.4PD (40% slag) 0.1655 0-1122 0.0533 67"8 32.2

P A ( c o n t r o l )

0 - 0 5 5 -

0 . 0 5 -

0 . 0 4 5 -" ~ 0 . 0 4 -" 0 - 0 3 5 -a

0 . 0 3 -o> 0-02 55_~ o-o2

~ 0 . 0 1 5 -0.01 -

O.OOS -0. 01000

1 ~ o\

lO 1 o' i O . b lH e a n p o r e d i a m e t e r (u rn )

0.0550.05

_ 0 - 0 4 50"04

0- 035=~ 0.03"

0 0 2 5 .0 . 0 2 "

0 . 0 1 5 .0 . 0 1 -

0.005 -0 -0 1000

P B ( 2 2 % p f a )

1 ~ o l O 1 ~ . 1 o ! o lM e a n p o r e d i a m e t e r (urn)

O.OSS0.05

0.0450"04

0 . 0 3 S= 0 . 0 3>o 0.025mg o-o2E 0 - 0 1 5 -

0.Ol -0 . 0 0 5 -

0 00-001 1000

0 . 0 5 5 -0 . 0 5

_ O . O ~ S0-04

~a 0 - 350 . 0 3

O> 0 . 025toc 0.02E 0.015

0"010 - 0 O 5

i 0. 0i f001 1000

P C ( 9 % m i c r o s it i c a)

! T100 10 1 0"1 0"01M e a n p o r e d i a m e t e r ( u r n )

P D ( 4 0 % s l a g )

I00 10 I 0.1 0.0 1M e a n p o r e d i a m e t e r ( ur n)

0.~)01

0 ~F i g . 2 . Pore-sizedistribution of different pastes.


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78 P. S. Mangat, J . M. El-Khatib, B. T. Molloy"~ O l ~ C o n t r o lE.~ D 2 o P F A ( 2 0 % )

D3 o M i c r o s i t i c a ( 1 0 % )3 \ ~ Dr, ~' S l a g ( 4 0 % )"6 \ \

1 0 2 0 3 0 4 0 SO 6 0 7 0D e p t h ( m m )

Fig. 3. Ac id-soluble chloride-concentration profiles formixes D1, D2, D3, and D4.3 0 0 0

Eg= 2000c

o 1 0 0 0i

u_

F i g . 4 .

0 0 . / O ~

10 20 3 0 4 0D e p t h ( m m )

O l x C o n f r o tO z o P F A ( 2 0 % )D 3 u M i c r o s i t i c a ( 1 0 % )D(, ~ S t ag ( 6 0 % )

510 iO 7' 0

Pore-fluid chloride-conce ntration profiles for mixesD 1 , D 2 , D 3 , a n d D 4 .

l o w e s t c h l o r i d e i n g r e s s a t a l l d e p t h s c o m p a r e dw i t h t h e c o n t r o l m i x ( D 1 ) a n d t h e o t h e r m i x e s ( D 2a n d D 4 ) , a l t h o u g h t h e p o r e v o l u m e o f t h e s i l i c a -f u m e p a s t e w a s f o u n d t o b e g r e a t e r t h a n t h a t o ft h e c o n t r o l p a s t e ( a n d a l l o t h e r p a s t e s ) a s s e e n i nt h e p r e c e d i n g s e c t i o n . T h e 2 0 % p f a m i x ( D 2 )e x h i b i t s a h i g h e r c h l o r i d e c o n c e n t r a t i o n a t t h ec o n c r e t e s u rf a c e t h a n t h e c o n t r o l m i x ( D 1 ) u p t o ad e p t h o f a b o u t 9 m m f r o m t h e c o n c r e t e s u r fa c e .A t g r e a t e r d e p t h s , t h e c h l o r i d e c o n t e n t o f m i x D 2i s l o w e r t h a n t h a t o f t h e c o n t r o l m i x. T h e 4 0 % s la gm i x ( D 4 ) s h o w s a s im i l a r t r e n d t o t h e 2 0 % p f am i x , t h e c h l o r i d e c o n t e n t s b e i n g h i g h e r t h a n f o rt h e c o n t r o l m i x u p t o a d e p t h o f a b o u t 1 5 m m .B e y o n d t h i s d e p t h , t h e c h l o r i d e c o n t e n t s a r el o w e r i n m i x D 4 t h a n i n m i x D 1 .C h l o r i d e c o n c e n t r a t io n i n p o r e f l u i d fo r m i x e sD 1 , D 2 , D 3 , a n d D 4 i s s h o w n i n F i g . 4 . T h em i c r o s i l i c a m i x ( D 3 ) s h o w s t h e l o w e s t c h l o r i d ec o n c e n t r a t i o n s o f t h e f o u r m i x e s a t a l l d e p t h s .H i g h e r c h l o r i d e c o n c e n t r a t i o n s a r e o b t a i n e d f o rt h e p f a b l e n d e d m i x a n d f o r t h e s la g b l e n d e d m i xt h a n f o r t h e c o n t r o l m i x u p t o a d e p t h o f a b o u t 1 5r a m .

F i g u r e s 3 a n d 4 s h o w n e g l i g i b l e c h l o r i d e c o n -c e n t r a t i o n ( a c i d - s o l u b l e a n d p o r e - f l u i d ) a f t e r ad e p t h o f 2 5 m m f r o m t h e c o n c r e t e s u r f a c e f o r th e1 0 % m i c r o s il i ca m i x. T h e p f a b l e n d e d m i x a n d t h e

E t e c t r o d e ISymbotlj

: 3 l ' , ' (a l M i, o i. . . . . . . . . . I B o . 0 m I o , I

" : # ~ . . . . . . . . . . . . . . . . . . . . o5 0 0 ~ , ~ . . . . . . . . ~ . . . . . - . . . . . . . . . .-600 / , , , ~ , ..... ~0 10 0 200 300 400 500 600Time(days)- 4 O 0 ] ( b } M ix D 2 ( 2 0 % p f a )

. . . . . . . . . . . . . . . . . . .

- 60 0- t ' ~ . . . . . . . . . . . . . . " . . . . . . . . . . . . .

0 100 200 300 4O0 5O0 600T i m e ( d a y s )

- 3 0 0 - ~ ( c ) M i x D 3 { 1 0 % m i c r o s it . ic a )t . . . . . . . . .- t O0 - ~ ' ,

~ " " = = 5 ;-'s- "ii i/ ......"600- :,- ..................-700 - ','~ : o .. .- B 0 0 # l- 9 0 0 0 1 6 0 2 0 0 3 0 0 / * b O S 0 0 ' 60 0

T i m e ( d a y s )o - " " c {~ 0 0 - , , ~ . ( d ) M i x D 4 ( 4 0 % s t a g )

- 5 0 0 ~.~::.=::~'~::,~,::.-.--.:=:====,=_.. . . . .; . . . . . . . 7 . . . . . . . : . . . . . . .0 1 0 0 2 0 0 3 0 0 4 O0 5 O0 60 0

T i m e ( d a y s )Fig. 5. Corrosion potential with time for mixes D1, D2,D3, and D4.

s la g b l e n d e d m i x s h o w n e g l ig i b le c h l o r id e c o n t e n ta f t e r a d e p t h o f 3 5 n u n f r o m t h e c o n c r e t e s u r fa c e ,w h e r e a s t h e c o n t r o l m i x e x h i b i t s a c o n s i d e r a b l ec h l o r i d e c o n t e n t , e v e n a f t e r a d e p t h o f 6 5 m m .S i m i l a r o b s e r v a t i o n s o f g r e a t e r d e p t h s o f c h l o r i d ep e n e t r a t i o n i n t o n o r m a l c o n c r e t e h a v e b e e n m a d eb y o t h e r r e s e a r c h e rs , w h o h a v e s t a t e d t h a t d e t r i -m e n t a l a m o u n t s o f c h l o r o i d e r e a c h e m b e d d e ds t e e l e v e n t h r o u g h h i g h - q u a li t y c o n c r e t e w h e no r d i n a r y P o r t l a n d c e m e n t i s u se d i n t h e m i x w i th -o u t c e m e n t - r e p l a c e m e n t m a te ri al .1 9C o r r o s i o n p o t e n t i a l s , E cC o r r o s i o n p o t e n t ia l s o f th e t h r e e e l e c t ro d e s i n t h ec o n t r o l - m i x ( D 1 ) s p e c i m e n a r e p l o t t e d a g a i n s te x p o s u r e t i m e i n F i g . 5 ( a ) . S i m i l a r p l o t s f o r 2 0 %p f a m i x ( D 2 ) , 1 0 % m i c r o s i l i c a m i x ( D 3 ) a n d 4 0 %s lag mix (D4) a r e p lo t t ed in F ig . 5 (b) , ( c ) and (d ) .T h e l o n g - t e rm e l e c t r o d e p o t e n t i a l s o f t h e p f a m i x( D 2 ) a r e m o r e n e g a t i v e t h a n t h o s e o f th e c o n t r o lm i x , w h i c h i n d i c a t e s m o r e c o r r o s i o n a c t i v i t y i nt h e p f a m i x . I n t h e 1 0 % m i c r o s i li c a m i x (D 3 ) , t h ep o t e n t i a l s a t a n e a r l y s t a g e , u p t o 1 0 0 d a y s , a r em u c h m o r e n e g a t i v e t h a n t h o s e o f t h e c o n t ro l m i xa n d t h e o t h e r m i x e s ( D 2 , D 4 ) . T h e l o n g - t e r m


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Properties o f cement-replacement materials 79p o t e n t i a l s o f m i x D 3 , h o w e v e r , s h o w l e s s n e g a t i v ev a l u e s t h a n t h e c o n t r o l m i x ( D 1 ) . O n t h e o t h e rh a n d , t h e l o n g - t e r m p o t e n t i a l s o f t h e 4 0 % s l a gb l e n d e d m i x s h o w s i m i l a r c o r r o s i o n p o t e n t i a l s tot h e c o n t r o l m i x , a l th o u g h p r e v i o u s r e s e a r c h e r sh a v e i n d i c a t e d a s l o w e r p r o g r e s s i o n t o a c t i v ep o t e n t i a l s f o r r e b a r s i n s l a g conc rete. 19Polarisation resistance, RpT h e p o l a r i s a t i o n r e s i s t a n c e , R p , w h i c h i sm e a s u r e d b y u s i n g a p o t e n t io s t a t a p p a r a tu s , w a sc o n v e r t e d i n t o t h e c o r r o s i o n r a t e b y u s i n g F a ra -d a y ' s la w . D e t a i l s o f t h e e q u a t i o n s u s e d a r e g i v e ni n R e f. 1 8 . T h e a v e r a g e l o n g - t e r m p o l a r i s a t i o nr e s is t a n c es f o r r e b a rs e m b e d d e d i n s p e c i m e n s o fm i x e s D 1 , D 2 , D 3 : a n d D 4 a n d t h e c o r r e s p o n d i n gc o r r o s i o n r a t e s a r e l i s te d i n T a b le 6 . T h e p f a m i x( D 2 ) y i e l d s t h e l o w e s t gp va lue a n d t h e r e f o r e th eh i g h e s t c o r r o s i o n r a te . T h e c o r r o s i o n r a t e s w e r e0 "0 1 8 m m / y e a r a n d 0 . 0 0 7 5 4 m m / y e a r fo r t h e pf am i x a n d t h e c o n t r o l m i x , r e s p e c ti v e l y . T h e m i c r o -s i li c a m i x s h o w s a c o r r o s i o n r a t e o f 0 . 0 0 4 7 m m /y e a r , w h i c h i s t h e l o w e s t v a l u e o f t h o s e o b t a i n e df o r t h e f o u r m i x e s. T h e s la g b l e n d e d m i x y i el d s ac o r r o s i o n r a t e o f 0 . 0 0 5 4 m m / y e a r .

F urther discussionP a s t e s p e c i m e n s , w h i c h w e r e c a s t f o r m e r c u r y -i n t r u s i o n p o r o s i m e t r y , w e r e i n i ti a ll y m e m b r a n e -c u r e d i n a i r a t 2 0 C a n d 5 5 % r . h . P r e v i o u s w o r kh a s s h o w n a p o o r p e r f o r m a n c e o f t h e c u r i n gm e m b r a n e u s e d i n t h e i n v e s t i g a t i o n ,8 so them e m b r a n e - c u r i n g w a s c o n s i d e r e d t o b e i d e n t i c a lt o a i r - c u r i n g . I n o r d e r t o c o m p a r e t h e v a r i o u sa s p e c t s i n v e s t i g a t e d i n t h i s s t ud y , t h e a c i d - s o l u b l ec h l o r i d e a n d p o r e - f l u i d c h l o r i d e - c o n c e n t r a t i o nv a l u es a t 1 0 m m f r o m t h e c o n c r e t e s u r f ac e w e r eo b t a i n e d f r o m F i g s 3 a n d 4 a n d a r e l i s t e d i n T a bl e6 . T h e 1 0 - m m d e p t h r e p r e s e n t s t h e c o v e r t o t h er e i n f o r c in g ba r s u s e d i n t h e c o r r o s i o n e x p e r i-m e n t s .I t c a n b e o b s e r v e d f r o m t h e r e s u l t s o b t a i n e dt h a t t h e i n t r u d e d p o r e v o l u m e o f t h e m i c r o s i l i c a

p a s t e i s t h e l a r g e s t o f th e p a s t e s s t u d i e d , a l t h o u g ht h e m i c r o si l ic a c o n c r e t e h a s t h e l o w e s t c h l o r i d ec o n c e n t r a t i o n s ( a c i d - s o l u b l e a n d p o r e - f l u i d ) a n dt h e l o w e s t c o r r o s i o n a c t i v it y . O n e p o s s i b l e e x -p l a n a t i o n f o r t h e l o w e r c h l o r i d e i n g r e s s d e s p i t et h e g r e a t e r p o r e v o l u m e i n m i c r o s i li c a c o n c r e t em a y b e t h e i m p r o v e d m a t r i x -a g g r e g a t e b o n d t h a th a s b e e n o b s e r v e d i n c o n c r e t e s c o n t a i n i n g m i c r o -s i l i c a a s p a r t i a l c e m e n t r e p l a c e m e n t . O t h e rr e s e a r c h h a s s h o w n t h a t , i n c o n c r e t e w i t h m o r et h a n 7 . 5 % c e m e n t r e p l a c e m e n t b y m i c r o s i l i c a ,a g g r e g a t e f a i l u r e l e a d s t o c o m p r e s s i o n f a i l u r e ,w h e r e a s , i n s i m i l a r n o n - m i c r o s i l i c a c o n c r e t e ,b o n d f a i l u r e a t t h e m a t r i x - a g g r e g a t e i n t e r f a c eo c c u r s a t t h e c o m p r e s s i o n - f a i l u r e s ta g e. T h i ss u p e r i o r i n t e r ra c i a l b o n d m a y b e r e s p o n s i b le f o rh i n d e r i n g c h l o r i d e p e n e t r a t i o n i n t o m i c r o s i l i c ac o n c r e t e .T h e i n t r u d e d p o r e v o l u m e o f t h e p f a p a s t e i sh i g h e r t h a n t h a t o f t h e c o n t r o l p as t e, a l t h o u g h t h ea c i d - s o l u b l e c h l o r i d e i n t h e p f a c o n c r e t e m i x w a sf o u n d t o b e l o w e r t h a n t h a t i n t h e c o n t r o l m i x , a ss h o w n i n T a b l e 6 . T h e c h l o r i d e c o n c e n t r a t i o n o ft h e p o r e f l u i d i n t h e p f a c o n c r e t e , h o w e v e r , w a sl a r g e r th a n t h a t i n th e c o n t r o l m i x u p t o a d e p t h o fa b o u t 2 0 m m . T h e s e r e s u l t s s h o w t h a t t h e c a p a -c i t y t o c o m b i n e c h e m i c a l l y ( b i n d ) c h l o r i d e i o n s i nt h e m a t r ix i s l o w e r i n p fa c o n c r e t e t h a n i n n o n - p f ac o n c r e t e a t r e l a t i v e l y l o w d e p t h s f r o m t h e c o n -c r e t e s u r f a c e . T h e s p e c i m e n s o f th i s i n v e s t i g a t io nw e r e e x p o s e d i n i t ia l l y t o a i r - c u r i n g fo r f o u r t e e nd a y s . T h e s u r f a c e z o n e o f c o n c r e t e w a s m o r e s u s -c e p t i b l e to t h e p o o r c u r i n g t h a t d i d n o t a l l o w f u llh y d r a t i o n o f p f a p a r t i c l e s a n d t h e r e f o r e l e d t o ah i g h e r c h l o r i d e c o n c e n t r a t i o n o f t h e p o r e f lu id .B u t , a t d e p t h s b e y o n d 3 0 m m , i n p f a c o n c r e te , t h ep o r e - f lu i d c h l o r i d e c o n c e n t r a t i o n d e c r e a s e d r e la -t i v e t o t h e a c i d - s o l u b l e c h l o r i d e c o n c e n t r a t i o n ,w h i c h t h u s i n d i c a t e d a s u p e r i o r c h l o r i d e - b i n d i n gc a p a c i t y o f t h e m a t r i x a t g r e a t e r d e p t h s , w h e r e t h ee f f e c t o f l o w - h u m i d i t y c u r i n g i s l e s s c r i t i c al . T h eh i g h c o n c e n t r a t i o n o f c h l o r id e i n t h e p o r e f lu i d( f re e c h l o r i d e ) i n t h e p f a c o n c r e t e a t a 1 0 - m md e p t h i s a c c o m p a n i e d b y a h i g h e r c o r r o s i o n r a te

Table 6. State of rebar corrosion and chloride concentration at 520 days of marine exposureMix Rp (ohm cm 2) Corrosionrate(m m / y e ar)

E c (m V S C E) Chloride concentration at lO-m m dep thAc id - so l ub& Pore - f l u id~ ) ~mM/~tre)

D1 4 104 0.00754D2 1.7 104 0.018D3 6-3 x 104 0.0047D4 5"6 104 0.0054

-4 50 to -5 50 2-0 1200-5 80 to -6 90 1-8 1325-44 0to -48 0 1.3 750-5 40 to -5 60 2.1 1250


8/9

80 P. S. Mangat, J . M. El-Khatib, B. T. Mollovthan in non-pfa concrete, although the acid-solu-ble chloride is lower in pfa concrete at the samedepth relative to the control mix D 1 and the slag-concrete mix D4. This indicates that the concen-tration of chloride in the pore fluid is responsiblefor determining the corrosion rate.The intruded pore volume of the slag blendedpaste is found to be larger than that of the controlpaste. Slightly higher concentrations of chloride(acid-soluble and pore-fluid) are obtained at theconcrete surface up to a depth of about 20 mm.The corrosion potentials of the reinforcementelectrodes embedded in the slag blended concreteare similar to, or slightly more negative than, thoseof the control mix at various periods of marineexposure (Figs 5(a) and 5(d)), which thus indicatessimilar progression to active corrosion potentials.The corrosion rate of 0.0054 mm/year for thereinforcement in slag concrete (Table 6) is lowerthan the value for the control specimen. Results ofother researchers indicate a slower progression toactive potentials for rebars in BFS concrete.2.2~

CONCLUSIONSThe following conclusions are based onexperimental results repor ted in this paper.

the1. Replacing about 10% of cement with micro-silica in a cement paste increases theintruded pore volume. However, both chlo-ride penetration (acid-soluble and pore-fluid) and the corrosion rate of embeddedsteel reinforcement decrease in concretecontaining a similar cement,replacementlevel of microsilica.2. The replacement of cement with about 20%pfa leads to a higher pore volume and a

coarser pore-size distribution in a hardenedpaste. It increases the concentration of acid-soluble chloride and of free chloride in thepore fluid in the concrete surface zone. Atdepths beyond 30 mm, the acid-solublechloride and the concentration of chloridein the pore fluid are reduced.3. The corrosion rate of steel in concretecontaining 20% pfa is higher than that innon-pfa concrete at a depth of 10 nun fromthe concrete surface.4. Replacing 40% of cement with slagincreases the intruded pore volume ofcement paste. The rate of corrosion of rebarembeded in concrete containing a similarreplacement level of slag is, however, lower.

5. Higher chloride concentration in the porefluid leads to higher corrosion activity ofrebar in concrete.6. The microstructure of paste matrix is notnecessarily related to chloride diffusion andto reinforcement-corrosion rates in con-cretes containing different cement-replace-ment materials.

A C K N O W L E D G E M E N T SThe authors gratefully acknowledge the financialsupport of the Science and Engineering ResearchCouncil and the University of Aber deen for thisproject.R E F E R E N C E S

1. Barrow, R. S . , Hadchi t i , K. M., Carrasqui l lo , P . M. &C a r ra sq u i l lo , R . L . , Te mp e ra tu re r i se a nd du ra b i l i ty o fc o nc re t e c o n ta in ing f ly a sh, A m e r ic a n C o n c re t e In s t i tu t eR e p o r t SP-114 , Vol . 1, 1989 , p p. 33 1 -4 7 .2 . Be rk e , N . S . , R e s i s t a nc e o f m ie ro s il i c a c o nc re t e to s t e e lc o r ro s io n , e ro s io n a nd c he mic a l a t t a c k . A me r ic a nC o nc re t e In s t i tu t e R e p o r t SP-114 , Vo l . 2 , 1989 , p p .8 6 1 - 8 6 .3 . Da y , R . C . & Ma rsh , B . K ., Me a su re m e n t o f p o ro s i ty inb l e n d e d c e m e n t p a s te s . Ce me n t a nd Conc r e t e R e s e a r c h ,1 8 ( 1 9 8 8 ) 6 3 - 7 3 .4 . Shigun, L. & Roy, D. M., Invest iga t ion of re la t ionsb e twe e n p o ro s i ty , p o re s t ru c tu re a n d C I - d i f fu s io n o f flya s h a n d b l e n d e d c e m e n t p a s t e s . C e m e n t a n d C o n c r e t eR e s e a r c h , 1 6 ( 1 9 8 6) 7 4 9 - 5 9 .5 . Ma nm o ha n , D . & Me h ta , P . K . , I n f lu e nc e o f p o zzo la mic ,s la g a nd c he mic a l a dm ix tu re s o f p o re s ize d i s t r ib u t io na n d p e r m e a b i l it y o f h a r d e n e d p a s te . Ce me n t , Conc r e t eand Aggregates, 3 ( S u m m e r ) ( 1 9 8 1 ) 6 3 - 7 .6 . R o y , D . M. & Pa rk e r , K . M. , Mic ro s t ru c tu re s a ndp ro p e r t i e s o f g ra nu la t e d s la g , Po r t l a nd c e m e n t b l e nds a tn o r m a l a n d e l e v a te d t e m p e r a t u re s . A m e r i c a n C o n c r e t eIn s t i tu t e R e p o r t SP-79 , 1983 , p p . 397 -414 .7 . Se l l e vo ld , E . J . , Ba ge r , D . H . , K l i tga a rd , E . & Knu dse n ,T . , S i l i c a fu me - - c e me n t p a s t e s : hy d ra t io n a nd p o res t ru c tu re . No rwe g ia n In s t i tu te o f Te c hno lo gy , Tro nd -h e l m , R e p o r t B M L 8 2 . 1 6 0 , 1 9 8 2 , p p . 1 9 - 5 0 .8 . Man gat , E S. & EI-Kh at ib , J . M., Inf luence of in it ia lc u r i n g o n p o r e s t r u c t ur e a n d p o r o s i t y o f b le n d e d c e m e n tc o nc re t e . A me r ic a n C o nc re t e In s t i tu t e , SP , 1992 . I npress.9 . Page , C. L. , Short , N. R. & EI-Tarras, A. , Dif fusion ofc h lo r ide io ns in ha rde ne d c e me n t p a s t e s . C e m e n t a n dConc r e t e R e s e a r c h , 1 1 ( 1 9 8 1 ) 3 9 5 - 4 0 6 .10. Byfors, K. , Inf luence of s i l ica fume and f ly ash onc h lo r ide d i f fu s io n a nd p H va lu e s in c e me n t p a s t e s .C e m e n t a n d C o n c r e te R e s e a rc h , 1 7 ( 1 9 8 7 ) 1 1 5 - 3 0 .11 . Ma nga t , P . S . & G u ru sa my , K . , C h lo r ide d i f fu s io n ins t e e l f ib re r e in fo rc e d c o nc re t e c o n ta in ing p fa . C e m e n ta nd Conc r e t e R e s e a r ch , 1 7 ( 1 9 87 ) 6 4 0 - 5 0 .

12. Mangat , P . S . & Molloy, B. T. , Fac tors inf luenc ingc h l o r id e i n d u c e d c o r r o s i o n o f r e i n f o r c e m e n t i n c o n -c re t e . Ri lem Mater ia ls and S t ruc tures , 2 5 ( 1 9 9 2 )4 0 4 - 1 1 .13 . Tho ma s , M. D . A . , Ma t the ws , J . D . & H a y ne s , C . A . ,C h lo r ide d i f fu s io n a nd re in fo rc e me n t c o r ro s io n in


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P ro p e r t i e s o f c e m e n t - r e p l a c e rn e n t m a t e r i a l s 8 1m a r i n e e x p o s e d c o n c r e t e c o n t a in i n g p u l v e r i s e d -f u e l as h.Corrosion of Reinforcement in Co ncr ete , E l s e v i e rA p p l i e d Sc ie nc e , Ba rk ing , Esse x , UK , 1990 , p p .1 9 8 - 2 1 4 .14 . Pa ge , C . L . & Ve nne s l a nd , O . , Po re so lu t io n c o m p o s i t io na nd c h lo r ide b ind ing c a p a c i ty o f s i l i c a - fu me c e me n tp a s t e , Materials and Structures, 1 6 ( 1 9 8 3 ) 1 9 - 2 5 .15 . C o rm ix L td . , W o rk ing to n , C u m b r ia , UK.1 6 . W a s h b u r n , E . W ., N o t e o n a m e t h o d o f d e t e rm i n i n g t h ed i s t r ib u t io n o f p o re s i ze s i n p o ro u s ma te r i a l s . Proc. Nat.Acad. Sci., 7 ( 1 9 2 1 ) 1 1 5 - 1 6 .17 . Ma nga t , P . S . & G u ru sa my , K . , Po re f lu id c o mp o s i t io nu n d e r m a r i n e e x p o s u r e o f s t e e l f i b r e r e i n f o r c e d c o n -c re t e . Cement and Concrete Research, 1 7 ( 1 9 8 7 )7 3 4 - 4 2 .18. Ma ngat , E S. & M olloy, B. T., Inf luen ce of pfa , slag andm i c r o s il i ca o n c h l o r i d e i n d u c e d c o r r o s i o n o f r e i n f o r c e -

m e n t i n c o n c r e t e . Cement and Concrete Research, 2 1( 1 9 9 1 ) 8 1 9 - 3 4 .19 . G jo rv , O . E . & V e nne s l a nd , O . , D i f fu s io n o f c h lo r idei o n s f r o m s e a w a t e r i n to c o n c r e t e . Cement and ConcreteResearch, 1 9 ( 1 9 7 9 ) 2 2 9 - 3 8 .2 0 . Po c o c k , D . C . , G u ru sa m y , K . & Mc A n o y , R . , P ro te c t iveme a su re s fo r ne w o r e x i s t ing r e in fo rc e d c o nc re t e s t ru c -t u r e s - - a n u p d a t e o n c u r r e n t d e v e l o p m e n t . I n Proceed-ings of 3rd Internat ional Conference on Deteriorat ion a ndRepair o f Reinforced Co ncrete in the Arabian Gulf,Ba hra in , 1 989 , Vo l. 2 , p p . 2 99 -33 6 .2 1 . Ke e r , J . G . , C ha dwic k , J. R . & Th o m p so n , D . M. , P ro te c -t i o n o f r e i n f o r c e m e n t b y c o n c r e t e r e p a i r m a t e r i al sa ga in s t c h lo r ide indu c e d c o r ro s io n . I n Corrosion ofReinforcement in Concrete, e d ? Pa ge , ? Tre a da wa y & ?Ba mfo r th . E l se v ie r A p p l i e d Sc ie nc e , Ba rk ing , Esse x ,U K , 1 9 9 0 , p p . 4 2 0 - 3 2 .

micro structure chloride difussion

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