Materials and Structures Volume 25 Issue 7 1992 [Doi 10.1007%2Fbf02472254] M. D. a. Thomas; J. D....

8/9/2019 Materials and Structures Volume 25 Issue 7 1992 [Doi 10.1007%2Fbf02472254] M. D. a. Thomas; J. D. Matthews -- The Permeability of Fly Ash Concrete

1/9

M a t e r i a l s a n d S t r u c t u r e s ,

1 9 9 2 , 2 5 , 3 8 8 - 3 9 6

h e p e r m e a b i l it y o f f ly a s h c o n c r e t e

M. D. A. TH OM AS and J. D. MA TT HE WS

Building Research Establishment, Garston, Watford, Herts WD2 7JR, UK

Oxy gen perm eabi l i ty te s ts were carr ied out on p la in ord inary Por t land cement OP C) and

f ly ash concre tes a t three nominal s t rength grades. Pr ior to te s t ing the concre tes were

subjec ted to a w ide range o f cur ing and exposure condi t ions . The resu l t s emphasize the

importance o f adequate cur ing to achieve concre te o f low permeabi l i ty , e spec ia l ly when the

ambient re lative humidity is low. In addit ion, the results demonstrate the considerable benefi t

tha t can be achieved by the use o f f ly ash in concre te. Even under condi t ions o f poor cur ing ,

f ly ash concre te i s s ign if icant ly te ss permeable than equal-grade O PC concre te, the d i f ferences

be ing more marked for h igher-grade concre tes. A t tem pts were made to corre la te s t rength

parameters w i th permeabi l i ty bu t i t i s conc luded tha t ne i ther the s t rength a t the end o f cur ing

nor the 28-day strength provides a re liable indicator of concrete permeabili ty . A reliable

correlation w as established betw een the w ater to tota l cemen tit ious m aterial ratio 1,w/ c + jr)]

and the permea bili ty of concretes subjected to a given curing and expo sure regime.

1. I N T R O D U C T I O N

T h e m o s t p r e v a l e n t c a u s e o f d e t e r i o r a t i o n o f r e i n f o r c e d

c o n c r e t e i s c o r r o s i o n o f th e s t e el r e i n f o r c e m e n t . C o n -

s e q u e n t l y , th e a b i l i ty o f t h e c o n c r e t e c o v e r t o p r o t e c t t h e

s te e l i s o f p a r a m o u n t i m p o r t a n c e i n d e t e r m i n i n g c o n c r e t e

d u r a b i l i t y . I n o r d e r t o m a i n t a i n t h e s t e e l i n a d e p a s s i v a t e d

s t a t e t h e c o n c r e t e c o v e r m u s t r e s is t th e p e n e t r a t i o n o f

c a r b o n d i o x i d e a n d c h l o r i d e io n s t o t h e d e p t h o f t h e s te e l.

A l t h o u g h t h e c h e m i s t r y o f t h e c o n c r e t e m a y i n f l u e n c e t h e

r a t e o f p e n e t r a t i o n o f th e s e a g e n t s , p h y s i c a l r e s i s t a n c e i s

p r o v i d e d b y t h e g e n e r a l lo w p e r m e a b i l i t y o f c o n c r e t e . I n

a d d i t i o n , i f d e p a s s i v a t i o n o f t h e s t e e l o c c u r s , t h e r a t e o f

c o r r o s i o n w i ll d e p e n d o n t h e p e r m e a b i l i t y o f t h e c o n c r e t e

t o o x y g e n a n d w a t e r. T h e p e r m e a b i l i t y o f t h e c o n c r e t e

c o v e r c a n t h e r e f o r e b e s e e n a s a k e y f a c t o r in d e t e r m i n i n g

t h e o v e r a l l d u r a b i l i t y o f r e in f o r c e d c o n c r e t e .

I t h a s b e e n w e l l e s t a b li s h e d t h a t t h e p a r t i a l r e p l a c e m e n t

o f o r d i n a r y P o r t l a n d c e m e n t ( O P C ) b y f ly a s h c a n l e a d

t o a s i g n if i ca n t r e d u c t i o n i n p e r m e a b i l i ty o f b o t h

h a r d e n e d c e m e n t p a s t e I - 1 ,2 ] a n d c o n c r e t e I - 3 ]. T h i s

r e d u c t i o n m a y b e a t tr i b u t e d t o a c o m b i n a t i o n o f t h e

r e d u c t i o n i n w a t e r c o n t e n t f o r a g iv e n w o r k a b i l i t y a n d

t h e p o r e s t r u c t u r e r e f i n e m e n t d u e t o p o z z o l a n i c re a c t i o n .

D u e t o t h e l o n g - t e r m n a t u r e o f th e p o z z o l a n i c r e a c t i o n ,

t h e b e n e f i t s a s s o c i a t e d w i t h i t a r e m o r e e v i d e n t i n

w e l l - c u r e d c o n c r e te , a n d i t h a s b e e n g e n e r a l l y c o n s i d e r e d

t h a t f ly a sh c o n c r e t e h a s a g r e a t e r s u s c e p t i b il i ty t o p o o r

c u r i n g t h a n O P C c o n c r e t e .

I n t h is s t u d y t h e p e r m e a b i l i t y o f f ly a s h c o n c r e t e , w i t h

a r a n g e o f f ly a s h c o n t e n t s , is c o m p a r e d w i t h c o n t r o l

* Present address: Civil Research Department, Ontario Hydro -

Research Division, 800 Kipling Avenue, Toron to, On tario M 8Z 5S4,

Canada..

0025-5432/92 9 RILEM

O P C c o n c r e t e s o f t h r e e n o m i n a l s t r e n g t h g r a d e s. A r a n g e

o f c u r i n g a n d e x p o s u r e c o n d i t i o n s h a s b e e n u s e d .

2. E X P E R I M E N T A L P R O C E D U R E

2 1 M a t e r i a l s

A s in g le s o u r c e o f o r d i n a r y P o r t l a n d c e m e n t c o m p l y i n g

w i t h B S 1 2 [ 4 ] w a s u s e d t h r o u g h o u t t h i s s t u d y a n d i t s

c h e m i c a l a n a l y s i s a n d B o g u e c o m p o s i t i o n s a r e g i v e n i n

T a b l e 1. T h r e e s a m p l e s o f f ly a s h w e r e u s e d a n d t h e se

w e r e s e l e c t e d t o p r o v i d e a s h e s w i t h a r a n g e o f 4 5 I~ m

s i e v e r e t e n t i o n v a l u e s . T h e p h y s i c a l a n d c h e m i c a l

p r o p e r t i e s o f t h e s e a s h e s a r e g i v e n , i n T a b l e 1 . T h a m e s

V a l l e y g r a v e l a g g r e g a t e s w e r e u s e d f o r a l l c o n c r e t e m i x e s .

2 2 C o n c r e t e m i x e s

T h r e e s e ri es o f c o n c r e t e m i x e s , d e s i g n a t e d A , G a n d H ,

w i t h c o n t r o l m i x c e m e n t c o n t e n t s o f 3 0 0 , 2 5 0 a n d

3 5 0 k g m - 3 , r e s p e c t i v e l y , a n d w i t h s l u m p s i n t h e r a n g e

3 0 t o 6 0 m m , w e r e u s e d . E a c h s e r ie s c o m p r i s e d s ix

c o n c r e t e m i x e s, i n c lu d i n g t h e c o n t r o l m i x , w i th a r a n g e

o f fl y a s h l e v el s a n d d e s i g n e d t o e q u a l 2 8 - d a y s t r e n g t h

( 3 5, 2 5 a n d 4 5 N n o m i n a l s t r e n g t h s , r e s p e c ti v e l y ). T h e

m i x p r o p o r t i o n s a r e g i v e n i n T a b l e 2 . F u r t h e r m i x s e ri es

d e s i g n a t e d B , C , D , E a n d F w e r e c a st w i t h t h e s a m e m i x

p r o p o r t i o n s a s f o r s e r i e s A .

2 3 M i x i n g a n d ca s t in g

M a t e r i a l s w e r e d r y - m i x e d f o r 1 m i n p r i o r t o t h e a d d i t i o n

o f w a t e r , a f te r w h i c h m i x i n g c o n t i n u e d f o r a f u r t h e r 2 m i n .

F r e s h c o n c r e t e p r o p e r t i e s w e r e d e t e r m i n e d 6 m i n a f t e r

t h e a d d i t i o n o f w a te r .


2/9

Mater i a l s and S t ruc tu res 389

Table t Chemical and physical properties of OPC and fly ashes

Elemental OPC Fly ash

oxide

P1 P2 P3

SiOz 20.55 48.2 48.1 52.4

AIzO 3 5.07 26.7 24.0 26.0

Fe203 3.10 11.6 10.6 9.4

CaO 64.51 1.71 6.12 1.69

MgO 1.53 1.62 1.61 1.54

K20 0.73 3.18 1.83 2.87

Na 20 0.15 0.65 0.79 1.32

TiO 2 0.26 0.88 1.00 0.94

P: O 5 0.19 0.33 0.63 0.21

MnzO 3


3/9

3 90 T h o m a s a n d M a t t h e w s

2 5 Testing con crete

F o l l o w i n g t h e v a r i o u s c u r i n g p e r i o d s a n d a i r - s t o r a g e

u n t il 2 8 d a y s t h e c y l i n d e r s c a s t f o r o x y g e n p e r m e a b i l i ty

t e s t s w e r e s a w n t o p r o v i d e t h r e e 5 0 m m t h i c k s l i c e s f r o m

t h e t o p o f th e s p e c i m e n . A s t h e p e r m e a b i l it y o f c o n c r e t e

t o g a se s i s s e n s i t i v e t o t h e m o i s t u r e l e v e l w i t h i n t h e

c o n c r e t e , t h e s l ic e s w e r e c o n d i t i o n e d a t 2 0 ~ a n d 6 5

R H f o r a f u r t h e r 2 8 d a y s t o e n s u r e t h a t a ll w e r e t e st e d

a t a s im i l a r m o i s t u r e c o n d i t i o n . T h e d u r a t i o n a n d r e l a ti v e

h u m i d i t y o f t h is c o n d i t i o n i n g p e r i o d h a s b e e n f o u n d t o

p r o d u c e s a t i s fa c t o r y d a t a I -5 ]. T h e s p e c im e n s t h a t w e r e

w a t e r - s t o r e d f o r 2 8 d a y s w e r e a l so su b j e c t e d t o t h i s

c o n d i t i o n i n g p e r i o d .

T h e p e r m e a b i l i t y c el l u s e d f o r t h e o x y g e n p e r m e a b i l i t y

d e t e r m i n a t i o n s w a s d e v e l o p e d b y L a w r e n c e [ 5 ] . I t a ll o w s

a f lu i d p r e s su r e t o b e a p p l i e d t o o n e o f th e f i a t c o n c r e t e

su r f a c e s w h i l e p r o v i d i n g a s e a l t o t h e c u r v e d su r f a c e .

T h e f lo w r a t e f r o m t h e o t h e r f i a t s u r f a ce is t h e n m e a s u r e d

u s i n g a b u b b l e f l o w m e t e r .

T h e g a s p e r m e a b i l i ty c o e f f ic i e nt i s d e t e r m i n e d t h r o u g h

a c o m b i n a t i o n o f D a r c y ' s l aw a n d t h e P o i s e u il le e q u a t i o n ,

t h e c o e f f i c i e n t a t a s i n g le i n l e t p r e s su r e b e i n g g i v e n b y

2QLtIP~

K o

P A

w h e r e K o = c o e f f i c ie n t o f g a s p e r m e a b i l i t y ( m : ) , Q = f l o w

r a t e ( m l s - ~), L = sp e c i m e n t h i c k n e s s ( m ) , ~ = v i s c o s i t y

o f g a s ( 2. 0 2 x 1 0 - 4 p o i s e f o r o x y g e n ) , P~ = o u t l e t p r e s s -

u r e ( b a r ) , P 2 = i n l e t p r e s su r e ( b a r ) a n d A = c r o s s -

s e c t i o n a l a r e a o f sp e c i m e n ( m 2 ) . I n t h i s s t u d y t h e f l o w

r a t e w a s m e a su r e d a t f i v e a b so l u t e i n l e t p r e s su r e s o f 2 ,

3 , 4 , 5 a n d 6 b a r a n d t h e p a r a m e t e r QP1/ P~ - P~) w a s

d e t e r m i n e d b y l i n e a r r e g r e s s io n .

3 . R E S U L T S

R e su l t s o f te s t s o n f r e sh c o n c r e t e a r e g i v e n in T a b l e 2

t o g e t h e r w i t h 2 8 - d a y w a t e r - c u r e d c o m p r e s s i v e s t r e n g t h

d a t a . F o r t h e m i x s e ri e s w i t h a c o n t r o l m i x c e m e n t c o n t e n t

o f 3 0 0 k g m - 3 , t h e se r e su l t s a r e t h e a v e r a g e r e su l t s f r o m

s i x m i x e s ( A t o F ) w i t h t h e s a m e m i x p r o p o r t i o n s . A l l

c o n c r e t e s h a d s l u m p v a l u e s w i t h i n t h e t a r g e t r a n g e o f 30

t o 6 0 m m a l t h o u g h t h e c o m p a c t i n g f a c t o r s ex h i b i t e d a

f a i r l y w i d e r a n g e . G e n e r a l l y , t h e a v e r a g e 2 8 - d a y w a t e r -

c u r e d s t r e n g t h w i t h i n a g i v e n s e r i e s is s i m i l a r f o r a ll m i x e s

a l t h o u g h c o n c r e t e s w i t h 3 0 f ly a s h t e n d t o b e o f s l ig h t ly

h i g h e r s t r e n g t h .

T h e c o e f fi c ie n t s o f o x y g e n p e r m e a b i l i t y d e t e r m i n e d f o r

t h e t o p 5 0 m m s li ce c u t f r o m t h e c o n c r e t e c y l i n d e r s a r e

g i v e n in T a b l e 3 . T h e s e d a t a a r e p r e s e n t e d a n d d i s c u s s e d

i n p r e f e re n c e to t h o s e o b t a i n e d f o r t h e o t h e r t w o s l ic e s

a s i t is t h e p r o p e r t i e s o f th e o u t e r l a y e r ( c o v e r z o n e ) t h a t

w i l l h a v e t h e g r e a t e s t i n f l u e n c e o n d u r a b i l i t y . T h e t r e n d s

s h o w n i n t h e d a t a f r o m t h e o t h e r t w o d i s c s w e r e s i m i l a r

a l t h o u g h g e n e r a l l y c o e f f i c i e n t s w e r e l o w e r a n d l e s s

sens i t i ve to cur ing e f fec t s .

F i g u r e 1 sh o w s t h e e f f e c ts o f c e m e n t c o n t e n t , l e v e l o f

f ly a s h ( P 1 ) r e p l a c e m e n t a n d c u r i n g t e m p e r a t u r e o n t h e

1 0 1 s [ C o n c r e te p e c im e n s u r e d o r 2 8 d a y s n w a t e r

g

>,

~ 10-17

g

5 C . c.

10-1a

F ly a s h con t en t ( P l )

Fig. 1 Perm eabi l i ty of concretes cured in water for 28 days.

o x y g e n p e r m e a b i l i t y o f c o n c r e t e s w a t e r - c u r e d f o r 2 8 d a y s .

T h e r e s u l t s fo r m i x e s w i th a c o n t r o l c e m e n t c o n t e n t o f

3 0 0 k g m - 3 a r e t h e a v e r a g e s f r o m f o u r m i x s e r ie s (A t o

D ) f o r s p e c i m e n s c u r e d at 2 0 ~ a n d f r o m t w o m i x s e r ie s

( E a n d F ) f o r s p e c i m e n s c u r e d a t 5 ~ I t i s c l e a r f r o m

F i g . 1 t h a t t h e p e r m e a b i l i t y d e c r e a se s w i t h i n c r e a se s in

c e m e n t c o n t e n t o r t h e l e v e l o f f ly a sh . T h e p e r m e a b i l i t y

o f t h e fl y a sh c o n c r e t e s w i t h 1 5 , 3 0 a n d 5 0 f l y a s h w e r e

o n a v e r a g e r e d u c e d b y 5 0 , 6 0 a n d 8 6 , r e s p e c t i v e l y ,

c o m p a r e d w i t h t h e p e r m e a b i l it y o f t h e c o n t r o l c o n c r e t e

( n o f l y a s h ). T h i s c o m p a r e s w i t h a r e d u c t i o n i n

p e r m e a b i l i ty o f l es s t h a n 5 0 w h e n th e O P C c o n t e n t o f

t h e c o n t r o l m i x i s i n c r e a s e d f r o m 2 5 0 ( m i x G 1 ) t o

3 5 0 k g m -3 ( m i x H I ) . T h i s i n c r e a s e i n c e m e n t c o n t e n t i s

a c c o m p a n i e d b y a r e d u c t i o n i n t h e f re e w a t e r / c e m e n t

r a t i o f r o m 0 . 6 8 t o 0 . 49 . C o n c r e t e s w a t e r - c u r e d a t 5 ~

w e r e m o r e p e r m e a b l e c o m p a r e d w i th t h o s e a t 2 0 ~

a l t h o u g h d i ff e r en c e s w e r e s m a l l f o r t h e c o n c r e t e s w i t h

z e r o o r 1 5 f l y a sh .

T h e p e r m e a b i l i t y o f a i r - s t o r e d c o n c r e t e s w a s c o n s i d e r -

a b l y h i g h e r (f r e q u e n t ly m o r e t h a n o n e o r d e r o f m a g n i t u d e )

t h a n w a t e r - c u r e d c o n c r e t e s e v e n a f t e r 7 d a y s m o i s t c u r i n g

p r i o r t o a i r - s t o r a g e . T h e l a r g e d i f f e r e n c e s p a r t i a l l y r e f l e c t

t h e d i ff e r e n t c u r i n g m e t h o d s u s e d . M o i s t c u r i n g w a s

c a r r ie d o u t b y t h e a p p l ic a t i o n o f d a m p s a c k in g a n d

p o l y e t h y l e n e t o t h e d e m o u l d e d s p e ci m e n s. M e a s u r e m e n t s

m a d e b y r e l a ti v e h u m i d i t y m e t e r s h o w e d t h e c u r in g

t e c h n i q u e t o g e n e r a l l y p r o v i d e a r e l a t i v e h u m i d i t y i n

e x c e ss o f 9 8 b u t r e a d i n g s b e l o w 9 5 w e r e s o m e t i m e s

r e c o r d e d ( e s p e c ia l ly a ft e r w e e k e n d s w h e n t h e s a c k i n g

w a s n o t r e w e t te d ) . H e n c e t h e c u r i n g c o n d i t i o n w o u l d n o t

h a v e b e e n a s e ff e ct iv e a s t h e s a t u r a t e d c o n d i t i o n o f


4/9

M a t e r i a l s a n d S t r u c t u r e s 3 91

T a b le 3 O x y g e n p e rm e a b i l i t y r e s u l t s fo r c o n c re t e s

M i x C o n t r o l A i r - s t o r a g e F l y a s h O x y g e n p e r m e a b i l i t y x 1 0 - 1 7 m 2 )

s e r ie s c e me n t c o n d i t io n s c o n te n t

con ten t ~o)

k g m - 3 )

W a t e r - c u r e d A i r - s t o r e d f o l l ow i n g

T e m p . R H f o r s p e ci f ie d c u r i n g p e r i o d

~ ~ ) 2 8 d a y s

i d a y 3 d a y s 7 d a y s

A 1 300 20 65 0 4.74 47.5 30.9 24.2

2 15 P1 2.10 34.2 29.0 18.6

3 30 P1 1.10 31.9 17.9 16.5

3 50 P1 0.64 32.2 16.7 8.94

5 30 P2 1.08 26.5 13.6 12.1

6 30 P3 1.98 27.4 17.0 11.8

B 1 300 20 40 0 5.11 65.4 32.5 26.2

2 15 P1 2.21 32.3 25.7 16.2

3 30 P1 1.00 36.1 26.9 16.5

4 50 P1 0.91 35.1 11.3 6.02

C1 300 20 80 0 5.68 43.0 29.8 16.9

2 15 P1 2.57 24 .3 14.4 13.7

3 30 P1 1.92 22.4 14.3 10.9

4 50 P1 0.80 22.6 6.33 6.49

D1 300 20 90 0 3.52 18.8 14.2 12.1

2 15 P1 1.89 13.6 14.0 9.62

3 30 P1 1.08 12.2 10.9 4.80

4 50 P1 0.25 11.2 7.55 4.60

E 1 300 5 65 0 4.85 44.8 25.7 9.14

2 15 P1 2.15 31.2 17.8 5.32

3 30 P1 1.61 43.1 21.9 5.30

4 50 P1 1.73 65.4 28.8 6.53

5 30 P2 2.64 43.9 19.6 10.7

6 30 P3 1.58 31.8 15.4 8.06

F1 300 5 80 0 5.96 42.4 16.0 12.6

2 15 P1 3.04 25.3 6.26 6.60

3 30 P1 3.14 30.3 13.8 3.44

4 50 P1 1.60 21.7 8.12 4.80

G1 250 20 65 0 5.26 65.2 36.2 25.3

2 15 P1 4.60 61.5 32.3 17.3

3 30 P1 3.28 54.1 22.0 16.1

4 50 P1 1.06 40.7 11.4 10.4

5 30 P2 4.97 43.8 22.3 8.06

6 30 P3 2.21 29.1 16.3 21.3

H1 350 20 65 0 2.94 43.7 24.3 19.6

2 15 P I 1.15 24.5 18.4 12.7

3 30 P1 0.84 18.2 9.76 8.59

4 50 P1 0.25 15.8 3.24 3.23

5 30 P2 0.86 14.5 16.3 6.20

6 30 P3 1.05 16.3 12.2 8.60

w a t e r - c u r i n g , b u t n e v e r t h e l e s s w o u l d r e f l e ct t e c h n i q u e s

u s e d o n s i t e .

T h e p e r m e a b i l i t y o f a i r - s t o r e d c o n cr e t e s w a s d e p e n d e n t

o n t h e d u r a t i o n a n d t e m p e r a t u r e o f i n it i a l m o i s t c u r i n g ,

t h e t e m p e r a t u r e a n d r e l at i v e h u m i d i t y o f s u b s e q u e n t

a i r - s t o r a g e a n d t h e l e v e l o f fl y a s h r e p l a c e m e n t . F i g . 2

s h o w s t h e e ff e ct o f f ly a s h c o n t e n t , c u r i n g p e r i o d a n d

t e m p e r a t u r e o n c o n c r e t e p e r m e a b i l i t y . F o r s p e c i m e n s

c u r e d a n d a i r - s t o r e d a t 2 0 ~ t h e p e r m e a b i l i t y d e c r e as e s

w i t h i n c r e a s e s i n c u r i n g p e r i o d a n d f l y a s h c o n t e n t .

I n c r e a s i n g t h e c u r i n g p e r i o d f r o m 1 d a y t o 3 o r 7 d a y s

r e s u l t s in a n a v e r a g e r e d u c t i o n i n t h e p e r m e a b i l i t y o f 37

a n d 5 4 70 , r e s p e c t i v e l y f o r c o n c r e t e s s t o r e d a t 2 0 ~ a n d

6 57 0 R H ) . T h e r e d u c t i o n i n p e r m e a b i l i t y d u e t o t h e f l y

a s h b e c o m e s m o r e m a r k e d a s t h e c u r i n g p e r i o d i s

e x t e n d e d ; a f t e r 7 d a y s c u r i n g , c o n c r e t e w i t h 5 07 0 fl y a s h


5/9


25

o

E

"5

10-1s

10-1~

C u r i n g A i r - s t o r a g e

c o n d i t i o n s

p e r io d 5 ~ & 6 5 % r h 2 0 ~ & 6 5 % r h

1 day - - - o - - - w,

3 days - - . - ~ - - . 9

7 d a y s - - - z ~ . . . . t

C e m e n t c o n t e n t 3 0 0 k g / m 3

~ o I ~ _

\

. J

/

I

J

x

i zx . . . . . . . . ~ . . . . . . . ~ f J

0 1 5 3 0 5 0

F l y a s h c o n t e n t ( % P 1 )

Fig. 2 E ffect of fly ash content, curing period and

tem peratu re on th e permeability of concrete.

w a s o v e r 6 0 l e ss p e r me a b le t h a n c o n c r e t e w i th n o f l y

ash .

T h e r e sp o n se o f t h e p e r m e a b i l i t y o f c o n c r e t e t o s t o r a g e

a t 5 ~ w a s a lso d e p e n d e n t o n t h e l e v el o f f l y a sh

r e p l a c e m e n t a n d t h e d u r a t i o n o f c u r in g . W h e n c u r e d f o r

o n ly 1 d a y , t h e p e r me a b i l i t y o f c o n c r e t e s w i th l o w l e ve l s

o f f l y a sh w a s r e l a t i v e ly u n a f f e c t e d b y t h e s t o r a g e

t e mp e r a tu r e . H o w e v e r , c o n c r e t e s w i th h ig h e r l e v e l s o f

a d d i t i o n s h o w e d m a r k e d i n c r e as e s i n p e rm e a b i l i t y w h e n

s to r e d a t t h e l o w e r t e mp e r a tu r e . A s t h e c u r in g p e r io d

in c r ea se s , t h e c o n c r e t e s s t o r e d a t 5 ~ e x h ib i t a p r o p o r -

t i o n a t e l y g r e a t e r r e d u c t i o n i n p e r m e a b i l i t y t h a n t h e

c o n c r e t e s s t o r e d a t 2 0 ~ F o r c o n c r e te s c u r e d f o r 3 d a y s ,

t h e p e r m e a b i l i t y o f t h o se w i th h ig h e r a d d i t i o n l e v e ls o f

a sh a lso sh o w a n i n cr e a se a t 5~ c o m p a r e d w i th 2 0 ~

a l th o u g h d i f f e r e n c e s w e r e sma l l f o r c o n c r e t e w i th 3 0 ~

f ly a sh . F o r c o n c r e t e s c u r e d f o r 7 d a y s , a ll t h e c o n c r e t e s

w e r e l e ss p e r me a b le w h e n s to r e d a t 5 ~ c o m p a r e d w i th

2 0 ~ th e d i f fe r e n ce s b e in g q u i t e c o n s id e r a b l e f o r

conc re te s wi th 0 to 30 f ly a sh .

F ig . 3 sh o w s th e e f f ec t o f c e me n t a n d f l y a sh c o n t e n t

o n t h e p e r me a b i l i t y o f c o n c r e t e s a i r - s t o r e d a t 2 0 ~ a n d

6 5 ~ R H i m m e d i a t e ly a f t er d e m o u l d i n g . A n i n c re a s e in

th e c e m e n t c o n t e n t o r t h e p r o p o r t i o n o f f l y a sh r e su l t s

i n a r e d u c t io n i n t h e p e r me a b i l i t y o f th e c o n c r e t e . T h e

e f fe c ts o f f ly a sh o n p e r me a b i l i t y a r e mo r e m a r k e d a t t h e

h i g h e r c em e n t c o n t e n t ( 3 50 k g m - 3 ) . F o r c o n c r e te s f r o m

this mix se r ie s ( se r ie s H) cured for one day , the

p e r me a b i l i t y o f t h e c o n c r e t e c o n t a in in g 5 0 f l y a sh w a s

r e d u c e d b y 6 4 ~ c o m p a r e d w i t h t h e c o n tr o l c o n c re t e .

F ig . 4 sh o w s th e e f f e ct o f t h e r e l a t iv e h u m id i t y o f

s to r a g e o n t h e p e r me a b i l i t y o f c o n c r e t e s i n i t i a l l y c u r e d

for 1 and 7 days . Th ere i s l i t t le cons is te n t d i f fe rence

b e tw e e n th e p e r m e a b i l i t ie s o f c o n c r e t e s s t o r e d a t 4 0 o r

65} /0 RH . How ever , conc re te s s tore d a t 80 R H a re le ss

p e r m e a b l e t h a n t h o s e s t o r e d a t 6 5 ~ a n d , a s th e r e l a ti v e

h u m id i ty i s i n c r e a se d a b o v e 8 0 ~ o, f u r th e r r e d u c t io n s i n

p e r me a b i l i t y a r e o b se r v e d .

C o mp a r in g t h e r e su l t s i n T a b l e 3 f o r c o n c r e t e s w i th

3 0 f l y a sh f r o m th e t h r e e d i ff e r e n t so u r c e s (d e s ig n a t e d

P 1 , P 2 a n d P 3 ) , i t i s e v id e n t t h a t t h e r e i s n o c o n s i s t e n t

v a r i a t i o n i n c o n c r e t e p e r me a b i l i t y w i th t h e so u r c e o f f l y

ash.

F ig . 5 sh o w s th e r e l a t i o n sh ip b e tw e e n t h e c o m p r e s s iv e

s t r e n g th a t 2 8 d a y s a n d t h e p e r me a b i l i t y fo r a ll a i r - s t o r e d

c o n c r e t e s ( mix s e r i e s A to H ) . T h e r e i s n o u n iq u e

r e l a t i o n sh ip l i n k in g t h e se tw o p r o p e r t i e s a n d t h e

r e g r e s s io n l i n e s sh o w n in t h e f i g u r e sh o w th e i n f lu e n c e

o f f l y a sh c o n t e n t . F o r a g iv e n a i r - s t o r e d s t r e n g th , f l y a sh

c o n c r e t e is s ig n i f i c a n t ly l e ss p e r me a b le t h a n O P C

o

o

10-15

S p e c i m e n s

m o i s t c u r e d f o r

1 d a y

A i r - s t o r e d a t 2 0 ~ a n d 6 5 % r h

10-1s

C o n t r o l m i x c e m e n t ( k g / m a )

2 5 0 9

3 0 0 =

v

3 5 0

l t5

3 t 0

F l y a s h c o n t e n t ( % P 1 )

Fig. 3 Effect of cement and f ly ash c ontent o n the

permeability of concrete.

o


6/9

M a t e r i a l s a n d S t r u c t u r e s 3 9 3

f

"O

O

10-~s

10"~s

Concretes air-stored

at 20~ (mixes A to D )

. - ' " Fly ash Cu r ing er iod:

~ , ~

a ' " con ten t 1 day 7 days ~ ~

15%P1 ~"

. . . . ~ - - - x

30 P1 . . . . . v . . . " ' o

5 0 P l 9 . . . . t3 . . .

4 ' 0

s ' 0 6 o 7'0 8 0

g 'o

Relat ive hum idity of air-storage

(%)

Fig . 4 E ffect o f ambient rela t ive hum idity on th e permeabi li ty

of concrete.

concrete, the difference increasing with fly ash content

and strength. In ad dition, the qu ality of curing has an

effect on the relationship between 28-day strength and

permeabil ity . T he average 28-d ay air-stored strength of

mi x es G 1 to G 6 (2 5 0 k g

m - 3 0 P C

after 7 days curing

i s 34 .0 M N m -2 co mp a red w i th 3 3 .8 M N m -2 fo r mi x es

A 1 t o A 6 ( 3 0 0 k g m - 3 0 P C ) c ur ed f o r 1 d ay . D e s p it e

these almost equal strengths the average permeabil ity of

the poorly -cured concretes from m ix ser ies A i s tw ice that

of the wel l -cured concretes from mix series G . A further

example o f the ef fects o f curing on the re la t ionship

between s trength and permeabi l i ty can be seen by

com paring water-cured and a ir-stored concretes o f

s imi lar s trength, the water-cured concretes being about

one order of ma gnitud e less permeable.

I t has been sugges ted that for OPC and f ly ash

concretes there is a s ingle relationship between per-

meabi l i ty and the com press ive s trength a t the end o f the

curing period [6 ] . F ig . 6 shows the re la t ionship

between oxygen permeabi l i ty and s trength a t the end o f

curing for OPC and f ly ash concretes cured for 1 , 3 or

7 days prior to air-storage at 20~ and 65% RH (mix

series A, G and H). It can be clearly seen that there is

no un ique re la t ionship between these propert ies for O PC

and f ly ash concrete as the re la t ionship i s dependent on

the fly ash content. For a given strength at the end of

curing, f ly ash concrete is considerably less permeable

than OPC concrete especia l ly a t h igher leve l s o f

replacement and higher strength.

F i g . 7 s h o w s t h e r e l a t i o n s h i p b e t w e e n t h e p e r m e a b i l i t y

and the water to to ta l cementi t ious materia l ra t io

[w / (c + f ) ] for concretes air-s tored a t 20~ and 65% RH

fol low ing curing (mix ser ies A , G and H). There appears

to be a unique re lationship for s imilarly-cured fly ash

and O PC conc retes irrespective of the level of replace-

ment . However , the re la t ionship i s not independent o f

10-1s

A

e~

g

: - E

E

~ I 0 1 6

6

o9

0

A I I c o n c r e t e s ( m i x e s A t o

H )

\ ~ . . ]o _ - .. r ~ - ~ . ~ **..

\ Oo ~ ~ . , o o


7/9

394 Thomas and Matthews

10-1s , Conc re tes a i r - s to red a t 20~ and 65% rh

fo l low ing cur ing (Mixes A, G and H)

1 ~ ~ ~ - ~ ~ r = - - 0 . 9 5 7

/ -o ~

o . - - - - . - ~

] ~

~ o o ~ " " - o _ . ~ D

- ~ , ~ r = - - 0 . 9 2 3 ~

a ~ : - - - - _

0 - , , ~ \ . . : . . o ~ . . ~ 0 .a 7 7 - -

=

~ ~ r = - - 0 .9 0 0

o

10 I; 0 ' 1; 2'0 3~0 4~0

Compress ive s t reng th a t the end o f cu r ing (MN/m2)

F ly ash con ten t

0 %

15% P1

30% P1

- ~ - - - - - - 5 0 % P 1

B 3 0 % P2

3 0 % P3

Fig. 6 Relationship between the compressive strength at the end of curing and permeability of concrete.

I O i S

g

10.ls

E

-~ 10-17 .

o

|

~ r e d at 2O~

n d

65%

rh

alter curing (MixesA, G and H)

Curing

period:

1 day 7 days 28 days

9 o ~ 0 /,, ly ash

9 v (~) 15%P1

9 ~ | 30% P1, P2 or P3

|

9 o | 50% P1

1o-la

0.3 014 015 016

Water/total cementitiousmaterial ratio

w/(c

Fig. 7 Relationship between ratio of water to total

cementitious material and permeability of concrete.

0 .7

the extent of curing or the exposure conditions following

curing.

4. DISCUSSION

The results clearly indicate the importance of curing to

achieve concrete of low permeability and hence good

durability, irrespective of whether or not fly ash is present,

especially if the ambient relative humidity is low. For

concretes stored at 20~ and 65 RH, an increase in

curing from 1 to 7 days had the effect of approximately

halving the permeability. This concurs with the 'doubling

in concrete quality' for the same extension of curing

period observed by Ho e t a l [7] using water sorptivity

measurements.

The ambient relative humidity also has a marked effect

on the permeability of the concrete. Generally, as the

relative humidity increases above about 65 the per-

meability decreases and more marked reduct ions are

observed at relative humidities above 80 . It has been

demonstrated that the hydration of Portland cement

ceases below about 80 RH [8] and a similar figure has

been suggested for cessation of the pozzolanic reaction

[9]. Above 80 RH the rate of both reactions increases

dramatically with further increases in relative humidity.

The relative humidity at the surface of the concrete also

influences the rate of drying of the concrete, the loss of

water from concrete during early stages of drying being

inversely proportional to the ambient relative humidity

[10].

The effect of fly ash on concrete permeabil ity has been

clearly demonstrated in this study. For all concretes

stored at 20~ the permeability of fly ash concrete is

considerably lower than that of similarly-cured OPC

concretes of the same strength grade even when curing

is terminated after 24 h. The reduction in permeability

of the fly ash concretes is believed to be due to a

combination of (i) reduced water content and (ii)

refinement of pore structure due to the pozzolanic

reaction. The first mechanism will not be affected by

curing, and a recent study by one of the authors [9] of

OPC and fly ash (30 fly ash) pastes cast at similar free

water to total cementitious materials ratios to those used

in concrete mixes A1 and A3 (i.e. 0.57 for OPC and 0.45

for fly ash) showed that the fly ash paste had a smaller

volume of large pores (>36.8 nm diameter) compared

with OPC paste after only 24 h hydration. The pozzolanic

reaction is dependent on moisture and is thought to cease

at relative humidities below abou t 80 [9]. However,

only the surface layer of a concrete specimen is


8/9

M a t e r i a l s a n d S t r u c t u r e s 3 9 5

imme d ia t e ly a f f e c t e d b y t h e a mb ie n t r e l a t i v e h u mid i ty

and , a t de pths b e low the sur face , suf f ic ien t m ois tu re wi l l

r e ma in f o r t h e p o z z o l a n i c r e a c t i o n ( a n d c e me n t h y d r a -

t i o n ) t o o c c u r f o r so me t im e a f t e r t h e c e s sa t i o n o f c u rin g .

C o n se q u e n t ly , so me o f t h e b e n e f i t s o f t h e p o z z o l a n i c

reac t io n wi ll be achieve d even in poor l y-cu red spec imens .

P r o v id e d a d e q u a t e c u r in g w a s g iv e n , a l l t h e c o n c r e t e s

s to r e d a t 5~ w e r e a c tu a l l y l e ss p e r me a b le t h a n

c o m p a r a b l e s p e ci m e n s s t o r ed a t 2 0 ~ A l t h o u g h t h e

h y d r a t i o n o f P o r t l a n d c e m e n t i s r e t a r d e d a t l o w

te mp e r a tu r e s , a f t e r su f fi c ie n t c u r in g p e r io d s t h e q u a l i t y

o f c o n c r e t e is e v e n tu a l l y i n c r e a se d d u e t o t h e imp r o v e d

d i s p e rs i o n o f h y d r a t i o n p r o d u c t s [ 1 0] . T h i s p h e n o m e n o n

r e d u c e s t h e p e r me a b i l i t y o f w e l l - c u r e d c o n c r e t e s a t l o w

te mp e r a tu r e , e sp e c i a l l y t h o se w i th l o w o r z e r o l e v e l s o f

f ly ash.

T h e p o z z o l a n i c r ea c t i o n i s al so t e m p e r a tu r e - d e p e n d e n t ,

a n d t h e r e sul t s f r o m th i s s t u d y sh o w th a t t h e p e r me a b i l i t y

o f p o o r ly - c u r e d c o n c r e t e s c o n t a in in g 30 a n d 5 0 f l y a sh

is inc reased b3) s tora ge a t 5~ com par ed wi th 20~

a l th o u g h th e c o n c r e t e c o n t a in in g 3 0 f l y a sh c o n s i s t e n t l y

r e ma in e d l e s s p e r me a b le t h a n t h e c o mp a r a b l e c o n t r o l

c o n c r e t e . T h i s su g g e s t s t h a t a t l o w t e m p e r a tu r e s s l i g h t ly

lo n g e r c u r in g p e r io d s ma y b e r e q u i r e d f o r h ig h f l y a sh

c o n te n t s ( 5 0 ) i f t h e b e n e f it s o f t h e p o z z o l a n i c r e a c t i o n

are to be realized.

A t t e m p t s w e r e m a d e t o e s t a b l i sh re l a t i o n sh ip s b e tw e e n

c o mp r e s s iv e s t r e n g th a n d p e r me a b i l i t y b u t n o s in g l e

r e l a t i o n sh ip e x i s t s t h a t i s i n d e p e n d e n t o f c u r in g h i s to r y ,

su b se q u e n t e x p o su r e c o n d i t i o n a n d f l y a sh c o n t e n t . T h e

c o mp r e s s iv e s t r e n g th a t t h e e n d o f c u r in g i s c l e ar ly

u n su i t a b l e a s a me a su r e o f c o n c r e t e q u a l i t y a s it a s su me s

th a t t h e p r o p e r t i e s o f th e c o n c r e t e a r e f i x e d o n c e c u r in g

i s t e r min a t e d . T h e s t r e n g th a t t h i s a g e t a k e s n o a c c o u n t

o f t h e a m b i e n t c o n d i t i o n s f o l l o w i n g c u r i n g a n d , a s w a s

a d e q u a t e ly d e m o n s t r a t e d i n F ig . 4, c h a n g e s i n t h e r e l a t i v e

h u m i d i t y a l o n e c a n c h a n g e t h e p e r m e a b i l i t y b y a f a c t o r

o f t h r e e . I n a d d i t i o n , w h e n c o mp a r in g c o n c r e t e s e x p o se d

to t h e s a me c o n d i t i o n s f o l l o w in g c u r in g , it is e v id e n t t h a t

f l y a sh c o n c r e t e s a r e c o n s id e r a b ly l e s s p e r me a b le t h a n

O P C c o n c r e t e s o f t h e s a me s t r e n g th a t t h e e n d o f c u r in g .

F o r e x a m p l e , c o m p a r i n g c o n c r e t e s w i t h a c o m p r e s s i v e

s t r e n g th o f 1 5 M N m - 2 a f t e r c u r in g ( t y p i c a l o f mix s e r ie s

H c u r e d f o r o n e d a y ) , a c o n c r e t e w i th n o f l y a sh m ig h t

ty p i c a l l y b e t h re e t ime s mo r e p e r m e a b le t h a n a c o n c r e t e

wi th 50 f ly a sh .

P r e v io u s w o r k e r s [ - 6 ] h a v e su g g e s t e d t h a t a s i n g l e

r e l a t i o n sh ip d o e s e x is t f o r O P C a n d f l y a sh c o n c r e t e s .

H o w e v e r , t h i s w o r k w a s b a se d o n l o w - s t r e n g th f l y a sh

c o n c r e t e s ( 1 8 M N m - 2 a t 2 8 d a y s ) a n d , a s c a n b e s e e n

f r o m F ig . 6 i n t h i s s t u d y , t h e r e i s a t e n d e n c y f o r t h e

d i f f e r e n t r e la t i o n sh ip s e s t a b l i sh e d f o r d i f f e r e n t a sh c o n -

t e n t s t o c o n v e r g e a t l o w e r s t r e n g th v a lu e s .

T h e 2 8 - d a y a i r - s t o r e d s t r e n g th i s a f f e c t e d b y b o th t h e

c u r i n g a n d s u b s e q u e n t e x p o s u r e h i s t o r y o f t h e c o n c r e t e

a n d i s c o n se q u e n t ly a b e t t e r e s t ima te o f c o n c r e t e q u a l i t y

th a n t h e s t r e n g th a t t h e e n d o f c u r in g . H o w e v e r , t h e

r e su l t s i n F ig . 5 w o u ld su g g e s t t h a t t h e 2 8 - d a y a i r - s t o r e d

s t r e n g th i s n o t a r e l ia b l e i n d i c a t i o n o f c o n c r e t e

p e r me a b i l i t y ( a n d t h u s d u r a b i l i t y ) . F ly a sh c o n c r e t e s a r e

c o n s id e r a b ly l e s s p e r me a b le t h a n e q u a l - s t r e n g th O P C

c o n c r e t e s ( b y u p t o f i v e t ime s f o r c o n c r e t e s w i th a s t r e n g th

o f 5 0 M N m - 2 a t 2 8 d a y s ) . I n a d d i t i o n , i t w a s sh o w n

th a t p o o r ly - c u r e d h ig h - g r a d e c o n c r e t e s ma y b e c o n s id e r -

a b l y m o r e p e r m e a b l e t h a n w e l l - c u r e d l o w - g r a d e c o n -

c r e t e s o f t h e s a me a c tu a l 2 8 - d a y a i r - s t o r e d s t r e n g th .

T h e r e l a t i o n sh ip i n F ig . 7 sh o w s th a t t h e p e r me a b i l i t y

o f c o n c r e t e fo r g iv en c u r in g a n d e x p o su r e c o n d i t i o n s i s

c lo se ly r e l a te d t o i t s w a t e r t o t o t a l c e me n t i t i o u s m a te r i a l

ra t io [ -w/(c + f ) ] i r r e spec t ive of the leve l of f ly a sh

r e p l a c e me n t . T h i s w o u ld su g g e s t t h a t , i n t e r ms o f

pe rm eabi l i ty , f ly a sh i s a s e f fec t ive a s an eq ua l ma ss of

O P C . I n p r a c t i c e , th e i n c lu s io n o f fl y a sh i n t h e mix

a l l o w s t h e w a te r c o n t e n t t o b e r e d u c e d , r e su l t i n g i n a

lo w e r w / ( c + f ) r a t i o a n d c o n se q u e n t ly r e d u c e d p e r -

me a b i l i t y .

A l th o u g h th e se r e su lt s r e fe r to a s i ng l e so u r c e o f O P C ,

i t h a s r e c e n t ly b e e n r e p o r t e d [ 1 1 ] t h a t d i f f e r en c e s i n t h e

c o m p o s i t i o n o f P o r t l a n d c e m e n t h a v e a s i g n i fi c a nt l y

sma l l e r e ff e ct o n t h e p e r m e a b i l i t y o f c o n c r e t e t h a n f a c to r s

su c h a s c u r in g o r w a te r / c e me n t r a t i o .

T h e r e su l ts o f t h i s s t u d y c o n c lu s iv e ly sh o w th a t t h e

in c o r p o r a t i o n o f f l y a sh r e su l t s i n a c o n c r e t e o f r e d u c e d

p e r me a b i l i t y a n d c o n se q u e n t ly i n c r e a se d d u r a b i l i t y .

A l t h o u g h t h e s e i m p r o v e m e n t s a r e m o r e n o t i c e a b l e i n

w e l l - c u r e d h ig h - s t r e n g th c o n c r e t e s , f l y a sh c o n c r e t e

r e ma in s l e ss p e r me a b le e v e n w h e n in a d e q u a t e ly c u re d .

T h e se r e su l t s a r e c o n s i s t e n t w i th t h e r e p o r t e d f i n d in g s

[ ,1 2 - 1 4 ] f r o m a n i n v e s t i g a t i o n o f t h e p r o p e r t i e s o f O P C

a n d f l y a sh c o n c r e t e s t a k e n f r o m a r a n g e o f i n - s er v i c e

c o n c r e t e s t r u c tu r e s . I n e a c h c a se e x a min e d , t h e c o v e r

5 0 m m o f t h e f ly a sh c o n c r e t e w a s f o u n d to b e l e ss

p e r m e a b l e t h a n t h e c o m p a r a b l e O P C c o n c r e t e ( c o m -

p a r i s o n s b a s e d o n e q u a l g r a d e o r c e m e n t i t i o u s c o n t e n t )

t a k e n f r o m th e s a me s t r u c tu r e .

5 . C O N C L U S I O N S

1 . F o r c o n c r e t e s t h a t w e r e w a te r - c u r e d f o r 2 8 d a y s ,

t h o s e c o n t a i n i n g f ly a sh w e r e o f l o w e r p e r m e a b i l i t y t h a n

e q u a l - g r a d e O P C c o n c r e te s , t h e d i f fe r e n ce s i n c r e a s in g

w i th f l y a sh c o n t e n t .

2 . T h e p e r m e a b i l i t y o f a l l t h e c o n c r e t e s e x a m in e d w a s

h ig h e s t a t t h e sh o r t e s t c u r in g t ime , e sp e c i a l l y w h e n th e

a m b i e n t r e la t iv e h u m i d i t y w a s l o w .

3 . A s t h e a m b i e n t r e l a t i v e h u m i d i t y d u r i n g s t o r a g e

in c r e a se d , p e r me a b i l i t y d e c r e a se d a n d t h e e f f e c t s o f t h e

d u r a t i o n o f mo i s t c u r in g b e c a m e l e ss s ig n i f i c an t .

4 . F o r c o n c r e t e s c u r e d a n d e x p o se d a t 2 0 ~ f l y a sh

c o n c r e te s w e r e o f l o w e r p e r m e a b i l i t y t h a n e q u a l - g r a d e

O P C c o n c r e t e e v e n u n d e r th e p o o r e s t c u r i n g a n d s t o r a g e

c o n d i t i o n s ( o n e - d a y c u r e , l o w a m b i e n t r e la t iv e h u m i d i t y ) .

5 . F o r c o n c r e t e s c u r e d a n d e x p o se d a t 5 ~ c o n c r e t e

w i t h 5 0 f ly a s h w a s m o r e p e rm e a b l e t h a n t h e

e q u a l - g r a d e O P C c o n c r e t e u n l e s s a d e q u a t e c u r i n g w a s

p r o v id e d . C o n c r e t e s w i th 15 o r 3 0 f l y a sh r e ma in e d le s s

p e r m e a b l e t h a n t h e c o n t r o l c o n c r et e w h e n c u r e d f o r o n l y

1 d a y a n d e x p o s ed t o l o w a m b i e n t r e la t iv e h u m i d i t y .


9/9


A C K N O W L E D G E M E N T

T h e w o r k d e s c r i b e d h a s b e e n c a r r i e d o u t a t t h e B u i l d i n g

R e s e a r c h E s t a b l i s h m e n t i n c o l l a b o r a t i o n w i t h a N a t i o n a l

P o w e r / I m p e r i a l C o l l eg e R e s e a r ch F e l lo w s h i p . T h e a u t h -

o r s w o u l d l ik e to t h a n k M r C h a r l e s H a y n e s f o r c a r r y in g

o u t t h e l a b o r a t o r y w o r k .

R E F E R E N C E S

1 . M anm ohan , D. and M ehta , P . K., In f luence o f pozzo lan ic ,

s l ag and chem ica l adm ix tures on pore s i ze d i s tr ibu t ion

and pe rm eabi l i ty o f ha rdened cem ent pa s te , Cement

Concr. Aggreg.

3(1) (1981) 63-67.

2. M arsh, B. K. , Day , R. L. and B onner, D. G. , Po re s t ructure

characteris t ics affecting the perm eabil i ty of cement pas te

contain ing f ly ash .

Cement Con cr. Res.

15(6) (1985)

1027-1038.

3. T hom as, M. D. A., Ma tthews, J . D. and H ayne s , C. A. , Th e

e ffect o f cur ing on the s t reng th and pe rm eabi l i ty o f P F A

concre te , in American Co ncrete In s t i tute SP-114, edi ted

by V. M. Malho t ra (AC I , De t ro i t , 1989) pp . i91-217 .

4. Bri tish S tanda rds Ins t i tut ion, Specif icat ion for Port lan d

Cem ents , BS 12 (BSI, Londo n, 1989).

5 . Lawrence , C . D. , Mea surem e nts o f pe rm eabi l i ty , in

P roceed ings o f 8 th In te rna t iona l Congres s on the

Chem is t ry o f Cem ent , R io de J ane i ro , 1986 , Vol . 5 ,

pp. 29-34.

6 . Chen Zh ang H ong and P a r ro t t , L . J ., Ai r pe rm eabi l i ty o f

cove r conc re te and the e f fec t o f cur ing , BCA repor t C /5

(Bri t ish Cement Associat ion, S lough, UK, 1989).

7. Ho, D. W. S. , Cui, Q. Y. and Ritchie, D. J. , The influence

of hum id i ty and cur ing t im e on the qu a l i ty o f conc re te ,

Cement Concr. Res. 19(3) (1989) 457 -464.

8. Pow ers , T . C., S truc ture an d ph ysical proper t ies of

ha rdened P or t l and cem ent pas te ,

J . Am. Cera m. Soc.

41(1) (1958) 1-6.

9 . Thom as , M. D. A. , The e f fec t o f cur ing on the h ydra t io n

and po re s t ruc ture o f ha rdened cem ent pas te con ta in ing

pulverized fuel ash ,

Adv. Cement Res.

2(8) (1989)

181-I88 .

10. Nevil le , A . M. , P rope r t i e s o f Con cre te (P i tm an , Lond on ,

1981).

11 Ben-B assat , M. , Nixon, P . J . and Har dcas t le , J ., Th e effect

o f di ffe rences in the com p os i t ion o f P or t l and cem ent on

the p rope r t i e s o f ha rden ed conc re te ,

Mag. Concr. Res.

42(151) (1990) 59-66.

12. Th om as, M. D. A., A n inves t igat ion of 10-year old concre te

br idges cons t ruc ted wi th convent iona l opc and pu l -

verized fuel ash co ncretes ,

Proc. Inst . Civil Engrs Part

1 86 (1989) 1111-1128.

13. Thomas, M. D. A. , Matthews, J . D. , Osborne, G. J . and

Cripwell , J . B., A c om paris on o f the prop ert ies o f opc,

p fa and ggbs conc re te s in re in forced conc re te wa l l s o f

slender sectio n ,

Mag. Co ncr . Res.

42(152) (1990)

127-134.

14. Th om as , M. D . A., A co m pa r i son of the p rope r t i e s o f opc

and pfa conc re te in 3 0-yea r o ld m ass conc re te s t ruc tu res ,

in Du rab i l i ty o f Bui ld ing Mate r ia l s and Co m p onen ts ,

ed i ted by J . M. Baker , P . J . Nixon , A. J . Ma ju m d ar and

H. Davies (S pon , Lo ndon , 1990) pp . 383-394 .

R S U M

P erm6abi l i t6 du b6ton aux cendres vo lante s

On a e f f ec tub des e ssa i s de perm~abi l i t~ sur des bb tons de

c i m e n t P o r t l a n d o r d i n a i r e n o n a r m b ( O P C ) e t s u r d e s

b~ tons aux cendres vo lan te s de t ro i s c lasse s de rk s i s tance

nomina le . Auparavan t , on a soumis l e s b~ tons d rou te une

g a m m e d e c o n d i t i o n s d e c o n s e r v a t i o n e t d ' e x p o s i t i o n . L e s

r~su l ta t s f on t re ssor t i r r imp or tan ce d 'une conserva t ion

adequ ate pou r ob ten i r un bk ton de f a ib l e permkabi l i t~ ,

sur tou t quand l ' humid i t~ re la t i ve ambian te e s t basse , e t

d~mont re , de p lus , l ' avan tage cons iderab le que procure

l ' u t i l i sa t ion de cendres vo lan te s dans l e bb ton .

M~me dans des cond i t i ons m~diocres de conserva t ion , l e

b ~ t o n a u x c e n d r e s v o l a n te s e s t b e a u c o u p m o i n s p e r m e a b l e

que le b~ton OPC de c lasse ~quivalente , les di f fbrences

~ tan t p lus marquees pour des b t ons de hau te c lasse . On

s ' e s t e f f orc~ dYtab l i r une corre la t ion en t re l e s param~t res

de la r~s i s tance e t l a permeabi l i tY , mai s on a conc lu que

n i l a r~s i s tance en f i n de conserva t ion , n i l a r~s i stance d

28

j ours , ne son t des t~moins f i ab l e s de l a perm~abi l it~ du

bk ton . On a ~ tab l i une corre la t ion s~re en t re l e rappor t

e a u / m a t ~ r ia u c i m e n t e u x t o t a l ( w / ( c + f ) ) e t la p e r m ~ a b i li t~

d e s b~ t o n s s o u m i s d u n e c o n s e r v a t io n d o n n ~ e e t d u n r ~ g im e

d ' expos i t i on .

Materials and Structures Volume 25 Issue 7 1992 [Doi 10.1007%2Fbf02472254] M. D. a. Thomas; J. D....

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Transcript of Materials and Structures Volume 25 Issue 7 1992 [Doi 10.1007%2Fbf02472254] M. D. a. Thomas; J. D....