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Cement and Concrete Research, 2, March 2, pp. 179-94, 1972-03-01

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Interaction of calcium lignosulfonate with tricalcium silicate, hydrated

tricalcium silicate, and calcium hydroxide

Ramachandran, V. S.

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CEMENT

a n d

CONCRETE RESEARCH. Vol

.

2 ,

p p .

179-194, 1972. Pergamon P r e s s ,

Inc.

Printed

i n

the United S t a t e s .

INTERACTION O F CALCIUM LIGNOSULFONATE WITH TRICALCIUM S I L I C A T E , HYDRATED TRICALCIUM

S I L I C A T E , AND CALCIUM HYDR0XI.DE

V. S. R a m a c h a n d r a n D i v i s i o n of Building R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a Ottawa 7 , O n t a r i o , C a n a d a (Communicated

by

P . 3 . Sereda) ABSTRACT T r i c a l c i u m s i l i c a t e , bottle - h y d r a t e d t r i c a l c i u m s i l i c a t e and c a l c i u m h y d r o x i d e w e r e e a c h t r e a t e d w i t h 0. 015-1. 0% c a l c i u m l i g n o s u l f o n a t e ( C L S ) u s i n g w a t e r o r d i m e t h y l sulfoxide

.

At low C L S c o n c e n t r a t i o n s C S h y d r a t e s a n d i r r e v e r s i b l y a d s o r b s CLS. 3 A t c o n c e n t r a t i o n s beyond a b o u t 0 . 2 5 - 0 . 3 5 % t h e h y d r a t i o n of C S 3 i s i n h i b i t e d . B o t t l e - h y d r a t e d C S a d s o r b s C L S i r r e v e r s i b l y in 3

both t h e a q u e o u s and the n o n - a q u e o u s m e d i a . T h e CH p h a s e a l s o i r r e v e r s i b l y a d s o r b s C L S . D i s p e r s i o n and t h e f o r m a t i o n of b a s i c C L S a r e i n d i c a t e d . S OMMAIRE On a t r a i t 6 l e s i l i c a t e d e t r i c a l c i u m , l e s i l i c a t e d e t r i c a l c i u m h y d r a t h e n b o u t e i l l e e t l'hydroxyde d e c a l c i u m a v e c 0 . 0 1 5 - 1 . 0% d e l i g n o s u l f o n a t e d e c a l c i u m ( L S C ) a u m o y e n d ' e a u ou d e s u l - foxyde de dirnhthyle. P o u r d e f a i b l e s c o n c e n t r a t i o n s d e LSC, l e C3S d e v i e n t un h y d r a t e e t a d s o r b e l e LSC i r r h v e r s i b l e m e n t . L e s c o n c e n t r a t i o n s d e p l u s d l e n v i r o n 0 . 2 5 - 0 . 35% e m p g c h e n t l ' h y d r a - t a t i o n du C S . L e C S h y d r a t h e n b o u t e i l l e a d s o r b e l e LSC 3 3 i r r h v e r s i b l e m e n t d a n s l e s m i l i e u x a q u e u x e t non a q u e u x . L a p h a s e C H a d s o r b e h g a l e m e n t l e LSC i r r d v e r s i b l e m e n t . On indique l a d i s p e r s i o n e t l a f o r m a t i o n d e LSC d e b a s e .

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Vol. 2 , No. 2

A D M I X T U R E , T R I C A L C I U M - S I L I C A T E , H Y D R A T I O N , L I G N O S U L F O N A T E

Introduction

Lignosulfonic acid and i t s s a l t s a r e widely u s e d a s w a t e r - r e d u c i n g and s e t - r e t a r d i n g a d m i x t u r e s in c o n c r e t e p r a c t i c e . T h e s e a d m i x t u r e s a r e known t o extend the setting t i m e by 30 - 60%, r e d u c e the w a t e r r e q u i r e m e n t f r o m 5

-

10% and i n c r e a s e t h e c o m p r e s s i v e s t r e n g t h a t 28 d a y s by 10

-

2070.

Even s m a l l amounts of lignosulfonate influence considerably the p h y s i c a l - m e c h a n i c a l p r o p e r t i e s of c o n c r e t e and hence it i s g e n e r a l l y b e l i e v - ed that the m e c h a n i s m of the action of t h e a d m i x t u r e involves the phenomenon of a d s o r p t i o n . A t t e m p t s have been m a d e t o study the adsorption of a d m i x - t u r e s on portland c e m e n t and the individual c e m e n t m i n e r a l s s u c h a s C S ,

3 C S , C3A and C AF:: (1 - 9 ) . In m o s t s t u d i e s the amount of t h e a d m i x t u r e

2 4

a d s o r b e d by the c e m e n t m i n e r a l s was d e t e r m i n e d by e x p o s u r e to an aqueous solution. By t h i s method hydration of the a d s o r b e n t could not be avoided, and consequently conclusions d r a w n f r o m s u c h e x p e r i m e n t s a r e questionable.

In a hydrating c e m e n t , a t any s t a g e of hydration, both the unhydrated and h y d r a t e d p h a s e s c o - e x i s t , and the p r e s e n c e of an a d m i x t u r e such a s c a l c i u m lignosulfonate (CLS) m a y r e s u l t in i n t e r a c t i o n s with t h e s e two t y p e s of p h a s e s . In view of t h i s i t was thought that a m o r e r e a l i s t i c a p p r o a c h t o the study of a d s o r p t i o n i s o t h e r m s should involve ( a ) m e a s u r e m e n t s u n d e r conditions in which the c e m e n t m i n e r a l d o e s not h y d r a t e . T h i s condition m a y be achieved by using a non-aqueous solvent f o r CLS. ( b ) D e t e r m i n a - tion of the adsorption i s o t h e r m on the h y d r a t e d p h a s e s using both aqueous and non-aqueous m e d i a . A t t e m p t s t o explain t h e action of CLS on C S

3 should include studies on the C-S-H and CH p h a s e s . ( c ) Study of t h e d e s o r p t i o n scanning b r a n c h e s emanating a t d i f f e r e n t points on the main' adsorption c u r v e . T h i s should indicate t h e type of s u r f a c e i n t e r a c t i o n . By adopting the above a p p r o a c h , s o m e s u c c e s s h a s been achieved in an u n d e r - standing of the influence of CLS on C A and i t s hydration p r o d u c t s (1 0, 11).

3

P r i o r s t u d i e s in t h i s Division w e r e concerned with the effect of CLS on the m i c r o s t r u c t u r e and morphology of P o r t l a n d c e m e n t and i t s constit

-

':Notations used i n t h i s p a p e r : C = CaO, S = SiO A = A1 0 F = F e 0

2' 2 3' 2 3'

H = H 0, CLS = C a l c i u m lignosulfonate, H-C S = bottle-hydrated C S.

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ADMIXTURE, TRICALCIUM-SILICATE, HYDRATION, LIGNOSULFONATE

u e n t s ( 1 2 ) . T h i s p a p e r e x a m i n e s t h e a d s o r p t i o n of C L S on C S , CH and 3 H-C S w i t h the hope of r e v e a l i n g t h e m e c h a n i s m of t h e a c t i o n of t h i s 3 a d m i x t u r e . M a t e r i a l s and P r o c e d u r e M a t e r i a l s T r i c a l c i u m s i l i c a t e u s e d i n t h i s w o r k c o n t a i n e d 99. 3370 C S , 0. 21

70

3

C A and 0.4670 f r e e l i m e and had a B l a i n e s u r f a c e a r e a of 3310 s q ~ m / ~ . 3

D e t a i l s of the p r e p a r a t i o n and c h a r a c t e r i z a t i o n of the C A p h a s e and 3 i t s h y d r a t e s a r e given i n a n o t h e r p u b l i c a t i o n ( 1 0 ) . C a l c i u m hydroxide w a s obtained by a c a l c i n a t i o n of C a ( 0 H ) ( a n a l a r ) 2 a t 1000°C f o r 5 h o u r s t o d e c o m p o s e t h e C a C O t h a t m a y have b e e n a c o n - 3 t a m i n a n t . T h e r e s u l t a n t C a O w a s h y d r a t e d i n a n e x c e s s of double d i s t i l l e d w a t e r . T h e e x c e s s w a t e r w a s r e m o v e d by v a c u u m d r y i n g . T h e b o t t l e - h y d r a t e d C S ( H - C S ) w a s p r e p a r e d by h y d r a t i n g C S 3 3 3 o v e r a r o t a t i n g w h e e l f o r 1 -1/2 y e a r s a t a

water/^

S r a t i o of 5. A f t e r 3 f i l t r a t i o n t h e m a t e r i a l w a s d r i e d a t 1170 R. H. o v e r a s a t u r a t e d s o l u t i o n of LiC1. H 2 0 . T h i s m a t e r i a l did not show a n y l i n e s f o r C S in the X - r a y

3 p a t t e r n . C a l c i u m lignosulfonate ( C L S ) i n t h e f o r m of p o w d e r w a s supplied by L i g n o s o l L t d .

,

Q u e b e c . T h i s m a t e r i a l w a s obtained by c h e m i c a l l y t r e a t i n g t h e s p e n t l i q u o r t o d e s t r o y s u g a r s . T h e s a m p l e contained 4. 570 r e d u c i n g b o d i e s , m a i n l y a s r e d u c i n g e n d g r o u p s t i e d t o t h e l i g n o s u l f o n a t e m o l e c u l e . M e t h o d s D i f f e r e n t i a l t h e r m a l a n a l y s i s ( D T A ) w a s c a r r i e d out i n a i r o r in a f l o w of N using a DuPont-900 T h e r m a l A n a l y s e r . S u r f a c e a r e a w a s obtain-

2

e d u s i n g N a s t h e a d s o r b a t e by a N u m i n c o - O r r s u r f a c e a r e a - p o r e volume 2

a n a l y s e r . T h e pH v a l u e s w e r e d e t e r m i n e d by t h e s t a n d a r d B e c k m a n pH m e t e r . F r e e l i m e i n the H-C S s a m p l e w a s e s t i m a t e d by the well-known

3 solvent v a r i a t i o n m e t h o d ( 1 3).

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TRICALCIUM-SILICATE,

H Y D R A T I O N ,

LIGNOSULFONATE

T h e conduction c a l o r i m e t e r containing s i x c h a m b e r s w a s supplied by I n s t i t u t e of Applied P h y s i c s , Delft. Though t h e c h a m b e r s a r e c o a t e d with t e f l o n , t h e h y d r a t e d p r o d u c t s t e n d e d t o s t i c k t o t h e s u r f a c e ; t h e r e f o r e , u s e of polyethylene l i n e r s w a s n e c e s s a r y . T h e s e n s i t i v i t y of t h e c a l o r i m e t e r i s 40 m v / W . A P e r k i n - E l m e r d o u b l e - b e a m 350 s p e c t r o p h o t o m e t e r w a s u s e d t o e s t i m a t e C L S i n s o l u t i o n s . P r o c e d u r e A d s o r p t i o n - d e s o r p t i o n i s o t h e r m s w e r e d e t e r m i n e d on C S , H - C S o r 3 3 CH by exposing t h e m t o d i f f e r e n t c o n c e n t r a t i o n s of C L S i n an a q u e o u s m e d i u m o r i n d i m e t h y l s u l f o x i d e . T o 0. 5-g s a m p l e s , e a c h c o n t a i n e d i n d i f f e r e n t s t o p p e r e d p o l y p r o p y - l e n e t u b e s , w e r e added 1 5 c c of t h e C L S s o l u t i o n of c o n c e n t r a t i o n s r a n g i n g f r o m 0. 01 5 t o 1 . 0%. T h e t u b e s w e r e r o t a t e d continuously f o r a day. At t h e end of t h i s p e r i o d t h e s u s p e n s i o n w a s c e n t r i f u g e d a n d 10 c c of the s u p e r - n a t a n t s o l u t i o n w i t h d r a w n , d i l u t e HC1 a d d e d t o o b t a i n a pH of 3 . 0 a n d t h e con

-

c e n t r a t i o n of C L S e s t i m a t e d by the s p e c t r o p h o t o m e t r i c m e t h o d a t a w a v e - l e n g t h of 375 m p . T h e d i f f e r e n c e i n t h e a m o u n t of C L S a d d e d o r i g i n a l l y and t h a t left i n t h e s o l u t i o n g a v e t h e p e r c e n t a g e of C L S a d s o r b e d by t h e s o l i d . At h i g h e r c o n c e n t r a t i o n s of C L S t h e s o l u t i o n s w e r e a d e q u a t e l y d i l u t e d f o r s p e c t r - o p h o t o m e t r i c d e t e r m i n a t i o n . Scanning c u r v e s on t h e d e s o r p t i o n b r a n c h w e r e o b t a i n e d a s follows. At a n y point on t h e a d s o r p t i o n c u r v e , a f t e r p i p e t t i n g out 10 c c of the s u p e r - n a t a n t s o l u t i o n s f o r C L S d e t e r m i n a t i o n , 10 c c of d i s t i l l e d w a t e r o r d i m e t h y l

sulfoxide w a s a d d e d t o t h e m i x t u r e . T h e tube w a s t h e n r o t a t e d on r o l l e r s f o r 2

-

3 d a y s . At t h e e n d of t h i s p e r i o d t h e c o n c e n t r a t i o n of C L S a n d t h e a m o u n t of C L S h e l d by t h e s o l i d w e r e d e t e r m i n e d a s b e f o r e . T h e s a m e p r o c e d u r e w a s a d o p t e d t o o b t a i n t h e s e c o n d p o i n t on t h e d e s o r p t i o n b r a n c h .

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Re s u l t s

I n t h e d e t e r m i n a t i o n of t h e a m o u n t of C L S s o r b e d by C S in a n a q u e o u s 3

m e d i u m , t h e o r d i n a t e r e f e r s t o t h e i n i t i a l c o n c e n t r a t i o n of C L S , r a t h e r t h a n t h e e q u i l i b r i u m c o n c e n t r a t i o n b e c a u s e C S, e s p e c i a l l y a t low C L S c o n c e n t r a - 3 t i o n s , i s not s t a b l e . I t should a l s o be s t a t e d t h a t e a c h of the p o i n t s w a s obtained t h r o u g h a s e p a r a t e r u n . In t h e C S - C L S - H 0 s y s t e m a t low con-

3 2 c e n t r a t i o n s of C L S t h e r e i s a s t e e p i n c r e a s e i n t h e a m o u n t of a d s o r p t i o n u p t o a c o n c e n t r a t i o n of about 0 . 1

%

C L S ( F i g . 1 ) . Above t h i s c o n c e n t r a t i o n a s t e e p d r o p i n t h e a m o u n t of a d s o r p t i o n i s n o t i c e a b l e . At c o n c e n t r a t i o n s above about 0 . 1 5 % t h e r e i s a g r a d u a l i n c r e a s e i n t h e a m o u n t of a d s o r p t i o n . On t h e d e s o r p t i o n b r a n c h s t a r t i n g f r o m 4 p o i n t s a t low c o n c e n t r a t i o n l e v e l s ( s i t u a t e d on t h e s t e e p p o r t i o n of t h e a d s o r p t i o n c u r v e ) t h e r e i s a l m o s t c o m p l e t e i r r e v e r s i b i l i t y of a d s o r p t i o n ( F i g . 2 ) . De s o r p t i o n f r o m p o i n t s c o r r e s p o n d i n g t o i n i t i a l c o n c e n t r a t i o n s of 0. 5, 0 . 7 and 1. 0'7'0 C L S show a d i f f e r e n t t r e n d ( F i g . 1 ) . S o m e i r r e v e r s i b i l i t y i n t h e a m o u n t of a d s o r p t i o n i s

e v i d e n t t o c o n c e n t r a t i o n l e v e l s of about 0. 1 5

-

0.2'7'0, but below t h e s e v a l u e s t h e r e i s a s t e e p a n d s i g n i f i c a n t i n c r e a s e i n t h e a m o u n t of a d s o r p t i o n .

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

I N I T I A L C O N C E N T R A T I O N O F C L S , gllOO

m a

F I G . 1

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FIG. 2 A d s o r p t i o n - d e s o r p t i o n c u r v e s of C L S on C3S i n a n aqueous m e d i u m a t low C L S c o n c e n t r a t i o n s . F i g u r e s 3 and 4 r e f e r t o the a d s o r p t i o n - d e s o r p t i o n i s o t h e r m s of C L S on t h e H - C S s a m p l e u s i n g w a t e r and d i m e t h y l sulfoxide r e s p e c t i v e l y a s 3 s o l v e n t s . The e q u i l i b r i u m c o n c e n t r a t i o n s a r e plotted on t h e a b s c i s s a , a s t h e a d s o r b e n t i s s t a b l e . E a c h p o i n t on the a d s o r p t i o n c u r v e r e f e r s t o a s e p a r a t e r u n . I n t h e aqueous m e d i u m t h e r e i s a r a p i d i n i t i a l a d s o r p t i o n of C L S followed by a m u c h s l o w e r r a t e a t h i g h e r c o n c e n t r a t i o n s . The scanning d e s o r p t i o n i s o t h e r m s d o not follow the a d s o r p t i o n i s o t h e r m . A s i m i l a r t r e n d i s evident i n t h e i s o t h e r m s u s i n g d i m e t h y l sulfoxide a s t h e solvent, but a t any e q u i l i b r i u m c o n c e n t r a t i o n m o r e C L S i s a d s o r b e d by t h e H-C S 3 s a m p l e i n a n aqueous m e d i u m .

The a d s o r p t i o n - d e s o r p t i o n i s o t h e r m s of C L S on t h e CH p h a s e a r e shown i n F i g . 5. The amount of a d s o r p t i o n i n c r e a s e s with the c o n c e n t r a - tion but t h e r a t e g r a d u a l l y d e c r e a s e s . T h e scanning i s o t h e r m s show a l m o s t c o m p l e t e i r r e v e r s i b i l i t y a t low c o n c e n t r a t i o n s studied. D i s c u s s i o n I n t e r a c t i o n of C L S with C S i n H 0 3- 2- T h e C S p h a s e a d s o r b s p r a c t i c a l l y no C L S i n a non-aqueous m e d i u m . 3

T h i s i s expected, considering the low s u r f a c e a r e a of C S a v a i l a b l e f o r the 3

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0 0 0.02 0.04 0.06 0.08 0. 10 0. 12 0. 14 0. 16 0. 18 E Q U I L I B R I U M C O N C E N T R A T I O N OF C L S , gllOO

me

FIG. 3 Adsorption-desorption i s o t h e r m s of C L S on hydrated C S

in the aqueous medium. 3

FIG. 4 i s o t h e r m s of calcium lignosulfonate on the hydrated C3S in a non- aqueous medium. E Q U I L I B R I U M C O N C E N T R A T I O N OF C L S , gllOO m a F i g . 1 the adsorption-desorption c h a r a c t e r i s t i c s m a y be explained a s follows. The initial s t e e p portion indicating adsorption of i n c r e a s i n g amounts of C L S i s due t o the formation of a high s u r f a c e a r e a , hydrated

2

C S ( N s u r f a c e a r e a -70 rn / g ) . The hydration of C S i s facilitated i n t h e

3 2 3

p r e s e n c e of low C L S concentrations. At a C L S concentration of about 0.15% C L S t h e r e i s a d e c r e a s e in the adsorption value. At a concentration

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0 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40

E Q U l L l B R l U M C O N C E N T R A T I O N O F C L S , gllOO m i

F I G . 5

A d s o r p t i o n - d e s o r p t i o n i s o t h e r m s of CLS on C a ( 0 H )

2'

of 0. 370 and beyond, t h e h y d r a t i o n of C S s e e m s t o be p r a c t i c a l l y nil. The 3 g r a d u a l i n c r e a s e i n t h e a d s o r p t i o n value f o r i n i t i a l c o n c e n t r a t i o n l e v e l s f r o m 0 . 3 t o 1 . 070 C L S m a y be due t o t h e d i s p e r s i o n of C S p a r t i c l e s . The 3 d i s p e r s i o n i n c r e a s e s the s u r f a c e a v a i l a b l e f o r t h e C L S m o l e c u l e s . In addition, m u l t i m o l e c u l a r a d s o r p t i o n of C L S m a y r e s u l t . The d i s p e r s i o n of c e m e n t p a r t i c l e s i s known t o o c c u r and i n c r e a s e a s t h e c o n c e n t r a t i o n of C L S i s i n c r e a s e d ( 1 ) .

T h e above explanation i s i n a c c o r d w i t h the DTA d a t a ( F i g .

6).

T h e c u r v e A c o r r e s p o n d i n g t o t h e s a m p l e on t h e p e a k of t h e a d s o r p t i o n c u r v e shows a b r o a d e n d o t h e r m a l e f f e c t below 250°C and a s h a r p e n d o t h e r m i c e f f e c t between 4 5 0 ° C and 5 0 0 ° C . T h e two inflections a r e r e s p e c t i v e l y due t o the d e h y d r a t i o n of C -S-H and C a ( 0 H ) i n t h e h y d r a t e d C S p r o d u c t . The

2 3

e x o t h e r m a l e f f e c t a t about 300°C i s due t o t h e oxidation of CLS. T h i s i s a b s e n t i n a n a t m o s p h e r e of N T h e points B a n d C , r e p r e s e n t i n g p o i n t s of

2'

low CLS a d s o r p t i o n , f a i l t o i n d i c a t e p e a k s f o r t h e p r e s e n c e of h y d r a t e d C S.

3

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F I G .

6

T h e r m o g r a m s of C3S t r e a t e d with C L S i n a n aqueous m e d i u m . ( C u r v e s A, B , C , D c o r r e s p o n d t o t h e s a m p l e s t a k e n a t d i f - e r e n t points on t h e a d s o r p t i o n - d e s o r p t i o n c u r v e d r a w n a b o v e . ) CONCENTMTION OF CLS ( g / 1 0 0 m e )

y

0 250 4 5 0 6 5 0 0 250 4 5 0 6 5 0 TEMPERATURE. " C TEMPERATURE, " C

s a m p l e s containing m o r e a d s o r b e d CLS. T h e pH value of the solution c o r r e s p o n d i n g t o t h e point A i s m u c h h i g h e r t h a n t h o s e c o r r e s p o n d i n g t o points B and C c o n f i r m i n g t h a t t h e r e i s p r a c t i c a l l y no h y d r a t i o n a t c o n - c e n t r a t i o n l e v e l s r e p r e s e n t e d by points B and C . T h e i r r e v e r s i b i l i t y i n t h e d e s o r p t i o n b r a n c h e s a t c o n c e n t r a t i o n s u p t o about 0.170 should i n d i c a t e t h a t CLS i s s t r o n g l y a d s o r b e d on t h e h y d r a t e d C S a s a c o m p l e x ( F i g . 2). It a p p e a r s t h a t in t h e s y s t e m C S - C L S - H 0 i t 3 3 2 h a s w r o n g l y been a s s u m e d t h a t a d s o r p t i o n o c c u r s only on t h e C S s u r f a c e , 3 even a t low CLS c o n c e n t r a t i o n s .

T h e scanning d e s o r p t i o n b r a n c h e s f r o m d i f f e r e n t points beyond a

c o n c e n t r a t i o n of 0. 5, 0. 7 and 1 % CLS m a y be explained a s f o l l o w s . The p a r t i a l i r r e v e r s i b i l i t y u p t o a c o n c e n t r a t i o n of about 0. 1 5

-

0.2570 C L S on t h e d e s o r p t i o n b r a n c h m a y p o s s i b l y r e p r e s e n t t h e e x i s t e n c e of a s t r o n g l y

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bound s u r f a c e c o m p l e x involving t h e i o n s on t h e s u r f a c e of C S , CLS and

3 H 0. T h e s t e e p i n c r e a s e i n t h e a d s o r p t i o n v a l u e s a t c o n c e n t r a t i o n s l e s s 2 t h a n about 0 . 2 5 % C L S i s d u e t o t h e f o r m a t i o n of t h e h y d r a t e d C S p r o d u c t , 3 which i s f a c i l i t a t e d a t low CLS c o n c e n t r a t i o n s . T h e f o r m a t i o n of h y d r a t e d C S a t t h e s e c o n c e n t r a t i o n s i s c o n f i r m e d f r o m t h e t h e r m o g r a m ( c u r v e D, 3 F i g .

6 ) .

T h e t h e r m o g r a m s h o w s l a r g e e n d o t h e r m i c p e a k s r e p r e s e n t i n g t h e p r e s e n c e of C - S - H a n d CH. On t h e d e s o r p t i o n b r a n c h t h e a m o u n t of CLS a d s o r b e d i s s i g n i f i c a n t l y m o r e f o r s a m p l e C t h a n f o r t h e o t h e r s b e c a u s e i t m u s t h a v e d i s p e r s e d a n d c o n s e q u e n t l y h y d r a t e d t o a g r e a t e r e x t e n t ( F i g . 1 ) . T h e i n h i b i t i v e e f f e c t of C L S on t h e h y d r a t i o n of C S d o e s not s e e m t o 3 be a s i m p l e function of t h e p e r c e n t a g e of i t s p r e s e n c e with r e s p e c t t o C S. 3 T h e c o n c e n t r a t i o n i n t h e a q u e o u s p h a s e and t h e w a t e r / s o l i d r a t i o a r e o t h e r f a c t o r s t o be t a k e n i n t o a c c o u n t . I n F i g . 7 c u r v e s A ,

B y

C a n d D r e p r e s e n t t h e conduction c a l o r i m e t r i c c u r v e s f o r C S t r e a t e d r e s p e c t i v e l y with 070, 3 0.1250/0, 0.250/0and 170 s o l u t i o n of C L S a t a w a t e r / s o l i d r a t i o of 2. I f C S i s 3 t r e a t e d with

. l q o

C L S s o l u t i o n a t a w a t e r / s o l i d r a t i o of 0. 5, t h e p e r c e n t a g e of C L S on t h e b a s i s of C S would be 0. 5, t h e s a m e a s s a m p l e C. T h e r e s u l t - 3

ing c u r v e would, h o w e v e r , be s i m i l a r t o D. A l l t h e above r e s u l t s s e e m t o s u g g e s t t h a t C S i s s t a b i l i z e d i n c o n t a c t w i t h a C L S solution of c o n c e n t r a t i o n 3 above abuut 0 . 2 5%. T h e i n f l u e n c e of t h e C L S c o n c e n t r a t i o n on t h e inhibitive a c t i o n on t h e h y d r a t i o n of C S m a y be i l l u s t r a t e d with a n o t h e r e x a m p l e . I n t h e h y d r a t i o n 3 of C S t h e i n h i b i t i v e a c t i o n of CLS m a y be c o u n t e r e d by t h e a d d i t i o n of s m a l l 3 F I G . 7 R a t e of h y d r a t i o n of C3S a s a function of t h e c o n c e n t r a t i o n of C L S by conduction c a l o r i m e t r y . TIME. H O U R S

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F I G . 8 Influence of C L S on the h y d r a t i o n of C S i n p r e s e n c e of C A. 3 3 C 3 S + 0 . 8 % C L S + H ( 1 D A Y ) , 0 6 1 2 I 8 2 4 3 0 H Y D R A T I O N , D A Y S a m o u n t s of C A o r i t s m e t a s t a b l e h y d r a t e s . The C A p h a s e c o n s u m e s l a r g e 3 3 a m o u n t s of C L S , leaving t h e s o l u t i o n d i l u t e w i t h r e s p e c t t o CLS. By t h e a d d i t i o n of 0.870 C L S ( o n C S b a s i s ) the h y d r a t i o n of C S i s stopped a l m o s t 3 3 i n d e f i n i t e l y ( F i g . 8 ) . By m i x i n g 5% C A with C S , h y d r a t i o n of C S 3 3 3 p r o c e e d s n o r m a l l y a f t e r t h r e e d a y s . T h i s i n d i c a t e s t h a t by i n t e r a c t i o n of C L S and C A the solution a t t a i n s a low CLS c o n c e n t r a t i o n , facilitating

3 d e s o r p t i o n of the s u r f a c e c o m p l e x on t h e C S p h a s e . By s t a r t i n g w i t h a 3 C L S c o n c e n t r a t i o n of 3 . 270, t h e inhibitive a c t i o n m a y be p r o l o n g e d ( c u r v e 4 , F i g . 8 ) . A C S s a m p l e , p r e t r e a t e d with a solution of C L S f o r a f e w m i n u t e s , 3 d r i e d and s u b s e q u e n t l y e x p o s e d t o t h e a c t i o n of C A r e q u i r e s 3 d a y s b e f o r e 3 t h e inhibitive a c t i o n of C L S i s r e m o v e d . T h i s i n d i c a t e s that CLS f o r m i n g a s u r f a c e c o m p l e x on t h e C S p h a s e i n a n a q u e o u s m e d i u m i s not e a s i l y 3 d e s o r b e d . T h e f o r m a t i o n of t h i s c o m p l e x o c c u r r i n g a s soon a s C L S solution c o m e s i n t o c o n t a c t with C S m a y be c o m p a r e d t o t h e f o r m a t i o n of a s u r f a c e 3 h y d r a t e d p r o d u c t of C S with w a t e r i n t h e induction p e r i o d . J u s t a s t h e 3 induction p e r i o d i s r e d u c e d a t t h e h i g h e r w a t e r / s o l i d r a t i o , t h e inhibitive a c t i o n of t h e c o m p l e x f o r m e d w i t h C L S i s a l s o r e d u c e d with a n i n c r e a s e i n t h e w a t e r / C ~ ~ r a t i o . I n t e r a c t i o n of C L S with H y d r a t e d C S i n 3- Aqueous o r Non-aqueous m e d i a T h e a d s o r p t i o n - d e s o r p t i o n i s o t h e r m s of C L S on t h e h y d r a t e d C S 3 (H-C3S) a r e shown i n F i g s . 3 and 4 . T h e scanning i s o t h e r m s d o not follow

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t h e a d s o r p t i o n , showing i n c r e a s i n g a m o u n t s of i r r e v e r s i b i l i t y of t h e a d s o r b e d C L S a s t h e c o n c e n t r a t i o n i n c r e a s e s . At a n y e q u i l i b r i u m c o n c e n t r a t i o n t h e a d s o r p t i o n v a l u e s a r e m u c h g r e a t e r i n t h e a q u e o u s t h a n i n the n o n - a q u e o u s m e d i u m . W a t e r m o l e c u l e s s e e m t o d i s p e r s e t h e h y d r a t e d C S b e t t e r and t o p r o m o t e p e n e t r a t i o n of 3 C L S i n t o t h e l a y e r p o s i t i o n s of t h e C - S - H p h a s e . In the C S - C L S - H 0 3 2 s y s t e m a n i n c r e a s i n g a m o u n t of a d s o r p t i o n a t h i g h e r c o n c e n t r a t i o n s w a s a t t r i b u t e d t o t h e d i s p e r s i o n e f f e c t . In o r d e r t o t e s t w h e t h e r t h i s i s likely t o o c c u r i n the H-C S s a m p l e s , N s u r f a c e a r e a s w e r e d e t e r m i n e d f o r 3 2 s a m p l e s containing 0 , 2 . 8 , 7 . 7 and 13. 270 a d s o r b e d CLS. N e g l e c t i n g t h e 2 s u r f a c e a r e a of a d s o r b e d C L S ( 0 . 69 m / g ) t h e r e c a l c u l a t e d v a l u e s of s u r f a c e a r e a of t h e H-C S component of t h e above s a m p l e s a r e 6 6 . 0 , 6 7 . 9 , 2 3

71. 2 and 6 7 . 9 m / g . The d i f f e r e n c e s b e t w e e n v a l u e s a r e not s i g n i f i c a n t enough t o s u g g e s t d i s p e r s i o n . T h e r e s u l t s i n d i c a t e t h a t C L S not only a d s o r b s a s a s u r f a c e c o m p l e x on t h e H-C S p h a s e but a l s o e n t e r s t h e i n t e r l a y e r s of t h e C - S - H p h a s e . 3 T h i s w a s a l s o o b s e r v e d f o r the h e x a g o n a l c a l c i u m a l u m i n a t e p h a s e i n w h i c h t h e i n t e r l a y e r p e n e t r a t i o n w a s a t t e n d e d by an i n c r e a s e i n the c - a x i s . It is

not p o s s i b l e t o c h e c k t h i s f o r the C - S - H p h a s e b e c a u s e of t h e difficulty of obtaining d i f f r a c t i o n l i n e s c o r r e s p o n d i n g t o t h e c - s p a c i n g . T h e e n t r y of C L S i n t o t h e i n t e r l a y e r s of C -S-H n e e d not n e c e s s a r i l y r e s u l t i n a n i n c r e a s e i n t h e N s u r f a c e a r e a b e c a u s e i n s a m p l e s t h a t a r e p r e d r i e d p r i o r t o s u r f a c e 2 a r e a d e t e r m i n a t i o n t h e e n t r a n c e of t h e i n t e r l a y e r s i s s e a l e d ( 1 4 ) . It i s p o s s i b l e t h a t t h e p e n e t r a t i o n of C L S m a y have a b e a r i n g on t h e s h r i n k a g e a n d c r e e p c h a r a c t e r i s t i c s of c e m e n t containing t h e C L S a d m i x t u r e . U n d e r the c o n d i t i o n s of low C L S c o n c e n t r a t i o n s and v e r y s h o r t p e r i o d s allowed f o r e q u i l i b r a t i o n by p r e v i o u s w o r k e r s , C L S m a y be bound m a i n l y a s a s u r f a c e c o m p l e x a n d n o t e n t e r the i n t e r l a y e r p o s i t i o n s i n t h e C - S - H p h a s e ( 8 ) . T h e t h e r m o g r a m s of H-C S t r e a t e d w i t h C L S , i n addition t o showing 3 e x o t h e r m i c p e a k s f o r t h e oxidation e f f e c t s i n t h e C L S , a l s o e x h i b i t t h e t y p i c a l l a r g e e n d o t h e r m a l e f f e c t a t a b o u t 8 0 0 ° C due t o t h e CLS-HC S 3 c o m p l e x ( F i g . 9 ) . T h e c u r v e D , r e p r e s e n t i n g the s a m p l e containing 13.270 C L S , s h o w s a n e x o t h e r m a l e f f e c t a t about 7 0 0 ° C followed by a l a r g e

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F I G .

9

D i f f e r e n t i a l t h e r m a l c u r v e s of h y d r a t e d C3S w i t h d i f f e r e n t a m o u n t s of a d s o r b e d CLS. A = H-C3S

+

070 CLS; B = H-C3S

+

2.870 CLS; C = H-C3S

+

7.770 CLS: D = H-C3S

+

1 3 . 2 % CLS; E = H-C3S

+

7% C L S ( N o n - a q u e o u s m e d i u m ) . 0 200 400 600 800 950 T E M P E R A T U R E , " C e n d o t h e r m a l e f f e c t a t 8 0 0 ° C . T h i s i s s i m i l a r t o t h e t h e r m a l c u r v e f o r t h e h e x a g o n a l a l u m i n a t e h y d r a t e containing C L S i n t h e i n t e r l a y e r s p a c e s ( 1 1 ) . I n t e r a c t i o n of C L S w i t h C a l c i u m H y d r o x i d e T h e a m o u n t of C L S a d s o r b e d by CH i n c r e a s e d with t h e c o n c e n t r a t i o n of C L S ( F i g . 5). T h e i n c r e a s e i n a d s o r p t i o n w i t h c o n c e n t r a t i o n m a y be d u e t o t h e d i s p e r s i o n of t h e C a ( 0 H j p a r t i c l e s and a n i n c r e a s e both i n the

2 p h y s i c a l and c h e m i c a l i n t e r a c t i o n s of C L S with CH. T h e s u r f a c e a r e a of 2 CH i s 1 6 . 2 m / g and t h a t containing a b o u t 1070 C L S s h o w s a n i n c r e a s e d 2 a r e a of 2 2 . 6 m / g . In t h e h y d r a t e d C S t h e c o n t r i b u t i o n t o the s u r f a c e a r e a 3

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d u e t o the d i s p e r s i o n of C H i s difficult t o a s s e s s . T h e h y d r a t e d C S c o n - 2 3 t a i n i n g about 35'7'0 CH h a s a t o t a l s u r f a c e a r e a of about 66 m / g . In a d d i t i o n t o i t s p r e s e n c e in s m a l l e r p r o p o r t i o n s , t h e s u r f a c e a r e a of CH i s l e s s than t h a t of t h e C - S - H c o m p o n e n t . In the H-C3S s a m p l e containing C L S t h e s m a l l i n c r e a s e i n the s u r f a c e a r e a m a y be a t t r i b u t e d t o t h e d i s p e r s i o n of t h e CH p h a s e . T h e d e s o r p t i o n i s o t h e r m s show l a r g e i r r e v e r s i b i l i t y a t a l l c o n c e n - t r a t i o n s ( F i g . 5). T h e s m a l l a m o u n t s of r e v e r s i b i l i t y a t h i g h e r c o n c e n t r a - t i o n s m a y i n d i c a t e a p h y s i c a l a d s o r p t i o n e f f e c t . T h e i r r e v e r s i b l e n a t u r e of the s c a n n i n g d e s o r p t i o n i s o t h e r m s u g g e s t s a c h e m i c a l i n t e r a c t i o n b e t w e e n C L S and CH. At high l i m e c o n c e n t r a t i o n s t h e C L S f o r m s a n i n s o l u b l e b a s i c lignosulf o n a t e . T h e r m o g r a m s of CH containing 1.20/0, 3.40/0, 6 . 4 % a n d 10.0'7'0 C L S show c l e a r l y a n e x o t h e r m i c e f f e c t a t about 300°C due t o oxidation of C L S ( F i g . 1 0 ) . T h e r e i s a l s o an e n d o t h e r m a l e f f e c t a t about 750

-

8 0 0 ° C OBCLS 1. 2% CLS 3.4% CLS 6.4% CLS 10.0% CLS F I G . 10 T h e r m o g r a m s of C a ( 0 H ) containing 2 d i f f e r e n t a m o u n t s of a d s o r b e d CLS. I I

1

'

,

I 0 200 400 600 800 TEMPERATURE. "C

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r e p r e s e n t i n g the p r e s e n c e of the basic CLS. The intensity of this effect p r o g r e s s i v e l y i n c r e a s e s with the amount of the i r r e v e r s i b l e CLS. The t e m - p e r a t u r e of the endothermal effect, and i t s i n c r e a s e d intensity with the CLS content, r e v e a l that i t i s not due to the p r e s e n c e of CaCO

3' Conclusions

At low concentrations of CLS in the t r i c a l c i u m s i l i c a t e - c a l c i u m lignosulfonate-water s y s t e m , i t i s the hydrated C S and not C S that i s

3 3

r e s p o n s i b l e f o r perceptible amounts of adsorption. T h e r e i s p r a c t i c a l l y no adsorption of CLS on the C S phase in a non-aqueous m e d i u m . Higher

3

concentrations of CLS, i n addition to inhibiting the hydration of C S , s e e m 3

to d i s p e r s e i t . The r e t a r d i n g o r inhibiting influence of CLS i s mainly dependent on i t s concentration in solutions and not on i t s proportion with r e s p e c t t o C S. The action of CLS on the hydration of C S a t e a r l y p e r i o d s

3 3

i s r e l a t e d t o the stability of the s u r f a c e complex involving the s i l i c a t e

s u r f a c e , CLS and H 2 0 . The s u r f a c e complex i s l e s s stable a s the CL* 0 2 r a t i o d e c r e a s e s . Both C-S-H and CH p h a s e s i r r e v e r s i b l y a d s o r b CLS. T h e r e i s an indication t h a t CLS not only c h e m i s o r b s on the C-S-H s u r f a c e but a l s o e n t e r s the i n t e r l a y e r positions.

Acknowledgments

T h e author thanks G. M. P o l o m a r k f o r the e x p e r i m e n t a l a s s i s t a n c e

.

T h i s p a p e r i s a contribution f r o m the Division of Building R e s e a r c h ,

National R e s e a r c h Council of Canada, and i s published with the approval of the D i r e c t o r of the Division.

R e f e r e n c e s

1. F . M . E r n s b e r g e r and W. G. F r a n c e , I n d u s t r i a l Eng. C h e m .

,

37,

-

598 (1945).

2. J . F . Young, J . Am. C e r a m . Soc. 52, 44 (1969)

-

3. B. Blank, D . R . Rossington and L . A . Weinland, J . A m . C e r a m . Soc. 46, 395 (1963).

-

(19)

Vol. 2 , No.

2

ADMIXTURE, TRICALCIUM-SILICATE, HYDRATION, LIGNOSULFONATE

T . Manabe and N. K a w a d a , Rev. 13th G e n e r a l M e e t i n g , J a p a n C e m e n t E n g i n e e r i n g A s s o c . , Tokyo, 1959, pp. 4 0 - 4 6 .

N. Nawada and M . N i s h i y a m a , Rev. 14th G e n e r a l M e e t i n g , J a p a n C e m e n t E n g i n e e r i n g A s s o c . , Tokyo, 1960, pp. 25-26.

W. C . H a n s e n , A m . Soc. T e s t i n g M a t . , Spec. T e c h . P u b l . , No. 266, pp. 3 - 3 7 , 1959. W . C . H a n s e n , J . M a t e r i a l s , - 5, 842 (1970). S. Diamond, J . A m . C e r a m . S o c . ,

-

54, 273 (1971). V.S. R a m a c h a n d r a n and R . F. F e l d m a n

,

C e m e n t Technol. 2, 121

-

(1971). V. S . R a m a c h a n d r a n and R. F. F e l d m a n , M a t g r i a u x e t C o n s t r u c t i o n s , ( u n d e r publication).

T. D. C i a c h and E . G. Swenson, C e m e n t and C o n c r e t e R e s . , 1 , P a r t I,

-

143; P a r t 11, 159 (1971).

E . E . P r e s s l e r , S. B r u n a u e r , D. L . K a n t r o and C . H. W e i s e , Anal. C h e m . 38, 877 (1961).

-

Figure

FIG.  2  A d s o r p t i o n - d e s o r p t i o n   c u r v e s   of  C L S  on  C3S  i n  a n  aqueous m e d i u m   a t  low  C L S  c o n c e n t r a t i o n s
FIG.  4  i s o t h e r m s   of  calcium  lignosulfonate  on the  hydrated  C3S  in a non-  aqueous  medium

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