Publisher’s version / Version de l'éditeur:
Cement and Concrete Research, 1, 4, pp. 367-383, 1971-07
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la
première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
NRC Publications Archive
Archives des publications du CNRC
This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.
For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.
https://doi.org/10.1016/0008-8846(71)90030-5
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Morphology and microstructure of hydrating portland cement and its
constituents. IV. Changes in hydration of a C3S, C2S, C3A, C4AF and
gypsum paste with and without the admixtures triethanolamine and
calcium lignosulphonate
Ciach, T. D.; Swenson, E. G.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
NRC Publications Record / Notice d'Archives des publications de CNRC:
https://nrc-publications.canada.ca/eng/view/object/?id=a1126783-2790-4dc1-9c40-cc1478b5999f https://publications-cnrc.canada.ca/fra/voir/objet/?id=a1126783-2790-4dc1-9c40-cc1478b5999fCEMENT and CONCRETE RESEARCH. Vol
.
1,
pp.
367-383, 1971. Pergamon Press, I n c . P r i n t e d i n t h e U n i t e d S t a t e s .A N A L Y Z E D
MORPHOLOGY AND MICROSTRUCTURE O F HYDRATING PORTLAND CEMENT AND ITS CONSTITUENTS
IV. CHANGES IN HYDRATION O F A C3S, C 2 S , C3A, C 4 A F AND GYPSUM P A S T E WITH AND WITHOUT THE ADMIXTURES
TRIETHANOLAMINE AND CALCIUM LIGNOSULPHONATE:: T . D. C i a c h and E . G. Swenson
Division of Building R e s e a r c h , National R e s e a r c h Council of C a n a d a Ottawa 7 , O n t a r i o , Canada (Communicated by G. M. I d o r n ) ABSTRACT S y s t e m a t i c s e q u e n t i a l o b s e r v a t i o n s with t h e e l e c t r o n m i c r o s c o p e w e r e m a d e of m o r p h o l o g i c a l c h a n g e s which o c c u r r e d d u r i n g h y d r a t i o n of a p a s t e m i x t u r e of C3S::::, C 2 S , C,A, C 4 A F and g y p s u m . The pronounced effect on r a t e of h y d r a t i o n of e a c h of two o r g a n i c a d m i x t u r e s w a s c l e a r l y o b s e r v e d . D i f f e r e n c e s could be s e e n a l s o i n t h e s t a b i l i t y and habit of h y d r a t i o n p r o d u c t s and i n the m i c r o s t r u c t u r e i t s e l f . T h e e l e c t r o n m i c r o g r a p h s shown i l l u s t r a t e t h e f o r m s of t h e p r o d u c t s a t d i f f e r e n t h y d r a t i o n t i m e s . SOMM AIRE D e s o b s e r v a t i o n s a u m i c r o s c o p e Clectronique ont 6th f a i t e s e n s6quence systCmatique p o u r o b s e r v e r l e s c h a n g e m e n t s m o r p h o - logiques qui p r e n a i e n t p l a c e a u c o u r s de l l h y d r a t a t i o n d'une p2te de C3S:*:k, C 2 S , C 3 A , C 4 A F e t de g y p s e . L e s e f f e t s p r o n o n c 6 s de deux a d j u v a n t s o r g a n i q u e s s u r l a v i t e s s e d ' h y d r a t a t i o n ont 6t6 n e t t e m e n t observCs. On a pu c o n s t a t e r d e s d i f f 6 r e n c e s d a n s l a stabilitd e t l l h a b i t u s d e s p r o d u i t s d ' h y d r a t a t i o n de m 6 m e que d a n s l a m i c r o s t r u c t u r e e l l e - m G m e . L e s r 6 s u l t a t s de l a m i c r o - g r a p h i e qui s o n t p r b s e n t 6 s i l l u s t r e n t l a f o r m e d e s p r o d u i t s 'a diffCrents s t a g e s de l ' h y d r a t a t i o n .
::Presented a t the C e m e n t S y m p o s i u m of the A m e r i c a n C e r a m i c S o c i e t y , 72 Annual M e e t i n g , P h i l a d e l p h i a , M a y , 1970.
.L .l-
-.-*Standard c e m e n t n o m e n c l a t u r e i s u s e d ; C,S = 3CaO.Si0,; C 2 S = 2CaO.SiQ; C 3 A = 3 C a 0 . A & , 0 3 ; C 4 A F = 4 C a 0 . A & , 0 3 . F e 2 0 3 ; w/c = w a t e r : c e m e n t
r a t i o by weight.
367
.s
V o l .
1,
No. 4 MICROSTRUCTURE, _CEMENT PASTE, ADMIXTUREST h i s i s the f o u r t h of a continuing s e r i e s of p a p e r s which r e p o r t the morphological changes o c c u r r i n g during the hydration of portland c e m e n t and i t s pure constituents in the a b s e n c e and i n the p r e s e n c e of a d m i x t u r e s . The f i r s t dealt with C3A ( I ) , the second with C3S and C,S ( 2 ) , and the t h i r d with C3S and C3A (3); i n e a c h c a s e the changes with and without gypsum w e r e noted.
The p r e s e n t p a p e r d e a l s with the m o r p h o l o g i c a l changes that occur during the hydration of a synthetic cement: a m i x t u r e of C3S, C,S, C3A, C 4 A F and gypsum, in the a b s e n c e and in the p r e s e n c e of two a d m i x t u r e s , t r i e t h a n o l a m i n e and c a l c i u m ligno sulphonate
.
Introduction
Studies t h a t d e s c r i b e the morphological changes o c c u r r i n g during the hydration of s i m p l e s y s t e m s of c e m e n t m i n e r a l s have been r e f e r r e d t o i n the p r e v i o u s p a p e r s i n t h i s s e r i e s ( 1 , 2, 3). E x p e r i m e n t s with the m u l t i - component m i x t u r e u s e d i n the p r e s e n t study, C3S, C$, C3A, %,AF and gypsum, apparently have n e v e r been p e r f o r m e d . C h a t t e r j i and J e f f e r y (4)
u s e d e l e c t r o n optical and x - r a y diffraction techniques i n a study of the hydration t o t h r e e m o n t h s of a m i x t u r e of a l i t e , C3A, C 4 A F and gypsum. T h i s and o t h e r s i m p l e r s y s t e m s have been reviewed r e l a t i v e l y r e c e n t l y by Copeland and K a n t r o ( 5 ) , T a y l o r (6) and de Jong ( 7 ) . T h e s e s t u d i e s would l e a d one t o expect c o n s i d e r a b l e d i f f e r e n c e s to o c c u r i n the r a t e s of r e a c t i o n and i n the n a t u r e of p r o d u c t s f o r m e d , a s a r e s u l t of varying the conditions o r combining the components.
C e r t a i n f o r m s of a l u m i n a , i r o n and sulphate, s u c h a s C3A i n C3S s y s t e m s , can e n t e r the CSH l a t t i c e s t r u c t u r e ; s u c h p e n e t r a t i o n s a r e r e p o r t e d t o affect t h e r a t e of hydration of the s i l i c a t e s and possibly a l s o t h e m i c r o - s t r u c t u r e ( 5 , 6, 7). R a t h e r than being i s o m o r p h o u s , p e n e t r a t i o n s m a y be
-
-
due t o additions t o the l a t t i c e ( 5 ) ; f o r e x a m p l e , SO4 m a y be added by a n extension of t h e CSH l a t t i c e .
The p r e s e n c e of gypsum a p p e a r s t o a c c e l e r a t e the hydration of a l i t e but only during the f i r s t d a y o r s o of C3S hydration ( 5 ) . W a t e r - t o - s o l i d s
V o l . 1 , No.
4
369MICROSTRUCTURE, CEMENT PASTE, ADMIXTURES
r a t i o in a C,S component s y s t e m affects the formation of l i m e and this i s believed t o effect changes in the r a t e s of f o r m a t i o n of s i l i c a t e h y d r a t e s .
With a d m i x t u r e s like s u c r o s e and calcium lignosulphonate, no new solid p h a s e s a p p e a r t o occur (8) but the r a t e s of hydration of the m a j o r
components a r e s h a r p l y affected. The r e t a r d a t i o n of C3S by such a d m i x t u r e s i s believed t o be due t o the inhibition of the r e l e a s e of l i m e . The p r e s e n c e of C3A, however, a c c e l e r a t e s the hydration of C3S due t o a p r e f e r e n t i a l adsorption of calcium lignosulphonate into the f o r m e r (8,
9,
10, 11). A lignosulphonate i s a l s o able t o delay the precipitation of gypsum. Some question e x i s t s a s to the effect of calcium lignosulphonate in r e t a r d i n g the change of C, AHB and C, AHl3 t o the C3AH6 f o r m ( 1 2, 13).The various effects r e p o r t e d above w e r e kept in mind when examin- ing the s y s t e m s in t h i s study.
M a t e r i a l s and P r o c e d u r e
-
The sample m a t e r i a l s u s e d , C3S, C,S, C3A, gypsum, t r i e t h a n o l - arnine and calcium lignosulphonate, a r e the s a m e a s those d e s c r i b e d in previous p a p e r s ( 1 , 2) dealing with the m o n o m i n e r a l p a s t e s . T h e C 4 A F had been p r e p a r e d s o m e y e a r s ago at the University of Saskatchewan by D r . T . Thorvaldson.
The d r y m i x t u r e of t h e synthetic c e m e n t used consisted of 44 p e r cent C3S, 34 p e r cent C 2 S, 12 p e r cent C3A, 5 p e r cent C 4 A F and 5 p e r cent
gypsum. T h e s e proportions w e r e considered reasonably in line with those o c c u r r i n g i n n o r m a l portland cement. They w e r e ground together in a porcelain -alumina ball -mill.
P a s t e s w e r e p r e p a r e d based on a r a t i o of 0. 5 p e r cent by weight w a t e r - t o - d r y powder. Admixture d o s a g e s w e r e 0 . 5 p e r cent by weight of the d r y m i x t u r e s .
At i n t e r v a l s of 5 m i n u t e s , 1 and
6
h o u r s , 1 , 2, 3, 7 and 14 days and 1 , 2 and 3 m o n t h s , s a m p l e s w e r e taken. Hydration was stopped by t r e a t i n g the p a s t e with acetone a t about -18"C, and then drying the f r o z e nMICROSTRUCTURE, CEMENT PASTE, ADMIXTURES V o l . 1, No. 4 Single s t a g e r e p l i c a s f r o m b r o k e n s u r f a c e s of the p a s t e w e r e m a d e using t h e p l a t i n u m - c a r b o n t e c h n i q u e . Only t h o s e e l e c t r o n m i c r o g r a p h s which d e p i c t t h e a v e r a g e and g e n e r a l m o r p h o l o g y a r e p r e s e n t e d i n t h i s p a p e r . R e s u l t s and O b s e r v a t i o n s 1. Hydration of s y n t h e t i c c e m e n t p a s t e with no a d m i x t u r e p r e s e n t T h e m i c r o s t r u c t u r e of s y n t h e t i c c e m e n t (w/c r a t i o 0. 5) a f t e r 5 m i n u t e s of h y d r a t i o n d i s p l a y e d a m i x t u r e of u n h y d r a t e d g r a i n s of c e m e n t m i n e r a l s and a m o r p h o u s f i l m s of h y d r a t i o n p r o d u c t s , A l s o p r e s e n t w e r e t h e r o d - l i k e p a r t i c l e s of e t t r i n g i t e and s o m e i r r e g u l a r p l a t e s on the s u r f a c e s of g r a i n s ( F i g . 1 ) . B y 6 h o u r s t h e a m o r p h o u s f i l m s and t h e e t t r i n g i t e p a r t i c l e s w e r e t h e m a i n h y d r a t i o n p r o d u c t s , but s m a l l rounded p a r t i c l e s on t h e s u r f a c e s of g r a i n s a p p e a r e d a s w e l l ( F i g . 2).
At the end of 1 d a y of h y d r a t i o n , l a r g e thin p l a t e s of h y d r a t i o n
p r o d u c t s and s m a l l f i b r o u s p a r t i c l e s of CSH had f o r m e d between u n h y d r a t e d g r a i n s of c e m e n t m i n e r a l s ( F i g . 3 ) .
At 3 d a y s h y d r a t i o n t h e m i c r o s t r u c t u r e d i s p l a y e d a c l o s e l y k n i t s t r u c t u r a l f o r m , with n e e d l e s of e t t r i n g i t e , p l a t e s of hexagonal CAH and s o m e s m a l l f i b r e s of CSH r a d i a t i n g f r o m c a l c i u m s i l i c a t e g r a i n s ( F i g . 4 ) . D u r i n g t h e next 2 w e e k s , m a n y d i f f e r e n t t y p e s of h y d r a t i o n p r o d u c t s w e r e f o r m e d , the d o m i n a n t being p l a t e l e t a g g r e g a t i o n s ( F i g . 5). F i b r o u s p a r t i c l e s of CSH w e r e p r e s e n t between t h e m , and s o m e t i m e s a f i b r o u s s t r u c t u r e developed on t h e s u r f a c e of p l a t e s ( F i g .
6 ) .
A t 1 m o n t h of h y d r a t i o n t h e s y n t h e t i c c e m e n t p a s t e had a d e n s e m i c r o s t r u c t u r e i n which p s e u d o m o r p h s of c a l c i u m s i l i c a t e g r a i n s s u r r o u n d e d by f i b r o u s p a r t i c l e s o r i r r e g u l a r f o r m s of p a r a l l e l c l e a v a g e could be distinguished ( F i g . 7 ) . S o m e of t h e p l a t e -like f o r m s of the h y d r a t i o n p r o d u c t s d i s p l a y e d f i b r o u s f r a c t u r e on t h e s u r f a c e s .D u r i n g t h e s e c o n d and t h i r d m o n t h s of h y d r a t i o n t h e m i c r o s t r u c t u r e i s v e r y d e n s e , although n o new f o r m s of h y d r a t i o n p r o d u c t s a p p e a r e d .
V o l . 1, No. 4 371 MICROSTRUCTURE, CEMENT PASTE, A D M I X T U R E S
F I G . 1 F I G . 2 M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e , w/c = 0 . 5. Age 5 m i n . M i x - p a s t e , w/c = 0. 5. Age
6
h r . R o d - t u r e of u n h y d r a t e d g r a i n s of c e m e n t l i k e e t t r i n g i t e and s m a l l rounded c o n s t i t u e n t s c e m e n t e d by a m o r p h o u s p a r t i c l e s of h y d r a t i o n p r o d u c t s . h y d r a t i o n p r o d u c t s . Note r o d - l i k e e t t r i n g i t e p a r t i c l e s and s o m e i r r e g-
u l a r , p l a t e - l i k e p r o d u c t s on the s u r f a c e s of g r a i n s . F I G . 3 FIG. 4 M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e , w/c = 0 . 5 . Age 1 day. L a r g e p a s t e , w/c = 0. 5. Age 3 d a y s . thin p l a t e s of h y d r a t i o n p r o d u c t s and D e n s e s t r u c t u r e of n e e d l e s and s m a l l f i b r o u s p a r t i c l e s of CSH. p l a t e s of CAH a n d s o m e s m a l lf i b r o u s p a r t i c l e s of CSH r a d i a t i n g f r o m c a l c i u m s i l i c a t e g r a i n s .
V o l . 1 , No. 4 MICROSTRUCTURE, CEMENT PASTE, A D M I X T U R E S
F I G . 5 F I G . 6
M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e , w/c = 0 . 5. Age 1 4 d a y s . p a s t e , w/c = 0. 5. Age 1 4 d a y s . Many d i f f e r e n t t y p e s of h y d r a t i o n Some p l a t e s of h y d r a t i o n p r o d u c t s p r o d u c t s with t h e dominant f o r m s d i s p l a y an o r i e n t e d two - d i m e n s i o n a l being p l a t e l e t a g g r e g a t i o n s . f i b r o u s s t r u c t u r e . F I G . 7 M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e , w/c = 0. 5. Age 1 m o n t h . V a r i o u s t y p e s of h y d r a t i o n p r o d u c t s with c l o s e l y packed s t r u c t u r e .
Vol. 1 , No. 4
373
MICROSTRUCTURE, CEMENT PASTE, ADMIXTURES
P l a t e s a r e t h e p r e d o m i n a n t f o r m , w i t h p s e u d o m o r p h s of c e m e n t m i n e r a l s a l s o a p p e a r i n g plentifully ( F i g . 8 ) .
X - r a y d i f f r a c t i o n s t u d i e s done on t h i s s y n t h e t i c c e m e n t p a s t e a f t e r 1 , 3 and 7 d a y s of h y d r a t i o n , showed t h a t t h e 4 . 9 i p e a k f o r CH a p p e a r e d a f t e r one d a y of h y d r a t i o n . L a t e r t h e p e a k s of t h e c e m e n t m i n e r a l s d i s a p p e a r e d but none of t h e d i f f r a c t o g r a m s showed m u c h change due t o t h e p o o r c r y s t a l - l i n e h a b i t s of the h y d r a t i o n p r o d u c t s .
2. H y d r a t i o n of s y n t h e t i c c e m e n t p a s t e w i t h 0. 5% t r i e t h a n o l a t n i n e p r e s e n t T h e f i r s t h y d r a t i o n p r o d u c t s developed between 5 m i n u t e s and 1 h o u r of h y d r a t i o n a s s h o r t r o d - l i k e p a r t i c l e s of e t t r i n g i t e t y p e , and r o u n d e d , u n o r i e n t e d p l a t e s on the s u r f a c e s of u n h y d r a t e d g r a i n s of c e m e n t m i n e r a l s ( F i g . 9 ) . At
6
h o u r s ' the m a i n h y d r a t i o n p r o d u c t s w e r e p l a t e s and s i n g l e r o d - l i k e p a r t i c l e s ( F i g . 1 0 ) . A f t e r 1 d a y of h y d r a t i o n t h e m i c r o s t r u c t u r e w a s a c l o s e l y knit s t r u c t u r e c o n s i s t i n g m a i n l y of p l a t e s ( F i g . 1 1 ) . D u r i n g t h e next p e r i o d up t o 3 d a y s , t h e a m o r p h o u s , f i b r o u s p a r t i c l e s of CSH w e r e r a d i a t i n g g r a i n s of c a l c i u m s i l i c a t e s and in s o m e p l a c e s w e r e i n the f o r m of p l a t e s ( F i g . 1 2 ) . T h e d o m i n a n t f o r m s of h y d r a t i o n p r o d u c t s a t 7 d a y s ' h y d r a t i o n w e r e l a r g e f i b r e s of CSH, r a d i a t i n g g r a i n s of c a l c i u m s i l i c a t e s , and a g g r e g a t e s of p l a t e s , s o m e of which d i s p l a y e d a f i b r o u s s t r u c t u r e ( F i g . 1 3 ) . T h e m i c r o s t r u c t u r e a t 14 d a y s c o n s i s t e d of i r r e g u l a r l y s h a p e d h y d r a t i o n p r o d u c t s which w e r e f o r m i n g a n u n o r i e n t e d s t r u c t u r e ( F i g . 1 4 ) . F i b r o u s p a r t i c l e s of CSH w e r e g r a d u a l l y changing t o p l a t e s having a t h r e e - d i r e c t i o n a l f i b r o u s f r a c t u r e o r c l e a v a g e . M a n y d i f f e r e n t f o r m s of h y d r a t i o n p r o d u c t s w e r e p r e s e n t a f t e r 1 m o n t h of h y d r a t i o n . Among t h e m t h e p s e u d o m o r p h o u s g r a i n s of c e m e n t m i n e r a l s , f i b r e s and p l a t e s could be d i s t i n g u i s h e d . S o m e of t h e p l a t e s a l s o d i s p l a y e d f i b r o u s f r a c t u r e ( F i g . 1 5 ) .374
Vol.
1 ,
No. 4
MICROSTRUCTURE, CEMENT PASTE, ADMIXTURES
F I G . 8 F I G . 9
M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e , w/c = 0. 5. Age 2 m o n t h s . p a s t e with 0. 5% t r i e t h a n o l a m i n e , S e v e r a l f o r m s of h y d r a t i o n p r o d u c t s w/c = 0. 5. Age 1 h r . H y d r a t i o n a m o n g w h i c h one c a n d i s t i n g u i s h p r o d u c t s a p p e a r a s p l a t e s , a m o r - m a n y p l a t e l e t s and f i b r o u s f o r m s . phous f i l m s and s h o r t r o d s between
t h e u n h y d r a t e d g r a i n s of c e m e n t m i n e r a l s . FIG. 10 FIG. 1 1 M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e w i t h 0. 5% t r i e t h a n o l a m i n e , p a s t e with 0. 5% t r i e t h a n o l a m i n e , w/c = 0. 5. Age 6 h r . M a i n h y d r a - w/c = 0. 5. Age 1 d a y . V a r i o u s t i o n p r o d u c t s a r e p l a t e s and s i n g l e f o r m s of h y d r a t i o n p r o d u c t s d i s - r o d s o r n e e d l e - l i k e p a r t i c l e s . playing a s o m e w h a t d e n s e s t r u c
-
t u r e , m a i n l y of p l a t e l e t s .V o l . 1, N o . 4 375 MICROSTRUCTURE, CEMENT PASTE, ADMIXTURES
F I G . 12 FIG. 1 3 M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e w i t h 0. 57'0 t r i e t h a n o l a m i n e , p a s t e w i t h 0. 5% t r i e t h a n o l a m i n e , w / c = 0.5. Age 3 d a y s . S e m i - w/c = 0.5. Age 7 d a y s . D o m i n a n t a m o r p h o u s f i b r o u s p a r t i c l e s of CSH f o r m s a r e f i b r e s , l a r g e r a d i a t i n g i n s o m e c a s e s a s s u m e a p l a t e - l i k e a g g r e g a t e s and p l a t e s which s o m e - f o r m . t i m e s d i s p l a y f i b r o u s f r a c t u r e . F I G . 14 FIG. 1 5 M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t M i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e w i t h 0. 57'0 t r i e t h a n o l a r n i n e , p a s t e w i t h 0. 57'0 t r i e t h a n o l a m i n e , w/c = 0. 5. Age 14 d a y s . I r r e g u l a r W / C = 0. 5. Age 1 m o n t h . Between
f o r m s of h y d r a t i o n p r o d u c t s d i s p l a y the v a r i o u s f o r m s of h y d r a t i o n p r o d - a n u n o r i e n t e d s t r u c t u r e . u c t s a r e p s e u d o m o r p h s of c e m e n t
m i n e r a l s , f i b r e s and p l a t e s . S o m e p l a t e s d i s p l a y t h r e e - d i r e c t i o n a l f i b r o u s f r a c t u r e .
Vol. 1 , No. 4
MICROSTRUCTURE, C E M E N T PASTE, ADMIXTURES
At 2 and a l s o a t 3 months the m i c r o s t r u c t u r e w a s v e r y dense, with I
the m a i n f o r m s of the hydration products being p l a t e s and f i b r e s ( F i g . 16). In s o m e i n s t a n c e s s m a l l rounded p l a t e l e t s a p p e a r e d t o be growing on the
l a r g e r plates.
X - r a y diffraction p a t t e r n s of the synthetic cement p a s t e with
triethanolamine w e r e taken a f t e r 4 h o u r s , 1 day, 3 d a y s and 90 days h y d r a -
tion t i m e , and the r e s u l t s a r e p r e s e n t e d in F i g u r e 17. I t i s v e r y significant that peaks of calcium hydroxide appeared a f t e r 3 days of hydration and that a f t e r this t i m e , t h e r e w a s v e r y little change.
3 . Hydration of synthetic cement p a s t e with 0. 5% calcium lignosulphonate
The f i r s t hydration products a t 5 m i n u t e s w e r e amorphous foils and s m a l l rod-like ettringite-type p a r t i c l e s between unhydrated g r a i n s of cement m i n e r a l s . T h e s e w e r e the m a i n hydration products a l s o during the next 6 h o u r s of hydration ( F i g . 18). In s o m e c a s e s t h e s e rod-like p a r t i c l e s a p - p e a r e d a s a s o r t of i r r e g u l a r plate.
At 1 day hydration the products a p p e a r e d a s unoriented p l a t e l e t s and f i b r e s located around the g r a i n s of the calcium s i l i c a t e s ( F i g . 19). After 3
days of hydration, the s p a c e s between the unhydrated g r a i n s of cement m i n e r a l s w e r e n e a r l y filled by t h e s e p l a t e l e t s and f i b r e s (Fig. 20).
At 7 days of hydration the m i c r o s t r u c t u r e had become a closely knit s t r u c t u r e with m a n y different f o r m s of hydration products. F r o m this period up t o 14 days the m a i n hydration products w e r e fibrous p a r t i c l e s (Fig. 21).
At 1, 2 and 3 months the m i c r o s t r u c t u r e looked dense and un-
oriented. P s e u d o m o r p h s of cement m i n e r a l s a p p e a r e d to be cemented t o - gether by platy and fibrous f o r m s of the hydration products. Some of t h e s e platy f o r m s had a s t r i a t e d cleavage and s o m e t i m e s a fibrous f r a c t u r e a s well ( F i g . 2 2 ) .
X - r a y diffraction p a t t e r n s of the synthetic cement paste with calcium lignosulphonate w e r e obtained at 4 h o u r s , 1, 3 and 90 days of hydration. I t
Vol. 1 , No. 4
37
7
M I C R O S T R U C T U R E , C E M E N T P A S T E , A D M I X T U R E S
FIG. 16 F I G . 18.
M i c r o s t r u c t u r e of synthetic c e m e n t M i c r o s t r u c t u r e of synthetic c e m e n t p a s t e with 0. 5% t r i e t h a n o l a m i n e , p a s t e with 0 . 5% c a l c i u m ligno- w/c = 0 . 5. Age 3 m o n t h s . F i b r e s sulphonate, w/c = 0 . 5. Age 6 h r . and p l a t e l e t s f o r m i n g a d e n s e Rod -like p a r t i c l e s of e t t r i n g i t e a r e
s t r u c t u r e . the dominant f o r m of hydration
p r o d u c t s . 90 d a y 3 d a y FIG. 17 X - r a y d i f f r a c t o g r a m s a t v a r i o u s t i m e s of h y d r a t i o n of synthetic c e m e n t p a s t e with 0 . 5% t r i e t h a n o l a m i n e , w/c = 0. 5. ( c u / N ~ , 45KV, 25mA.)
378
MICROSTRUCTURE, CEMENT PP ISTE, ADMIXTURES V o l . 1 , No. 4
FIG. 19
M i c r o s t r u c t u r e of synthetic c e m e n t p a s t e with 0. 5% c a l c i u m l i g n o -
sulphonate, w/c = 0. 5. Age 1 day. Unoriented p l a t e l e t s and a f i b r o u s s t r u c t u r e of hydration p r o d u c t s . F I G . 20 M i c r o s t r u c t u r e of synthetic c e m e n t p a s t e with 0. 5% c a l c i u m ligno- sulphonate, w/c = 0. 5. Age 3 d a y s . F i b r o u s p a r t i c l e s of hydration p r o d - u c t s f i l l s p a c e s between g r a i n s of c e m e n t m i n e r a l s . F I G . 21 M i c r o s t r u c t u r e of synthetic c e m e n t p a s t e with 0. 5% c a l c i u m l i g n o - s u l p h o n a t e , w/c = 0 . 5 . Age 14 d a y s D i f f e r e n t f o r m s of hydration p r o d - u c t s , m a i n l y of f i b r o u s habit. FIG. 22 M i c r o s t r u c t u r e of synthetic c e m e n t p a s t e with 0. 5% c a l c i u m ligno-
sulphonate, w/c = 0. 5. Age 1 month. D e n s e m i c r o s t r u c t u r e with m a n y p l a t y f o r m s of hydration p r o d u c t s .
V o l . 1, No. 4 379 MICROSTRUCTURE, CEMENT PASTE, A D M I X T U R E S
w a s o b s e r v e d that t h e m a j o r change o c c u r r e d i n t h e p e a k s r e p r e s e n t i n g c a l c i u m hydroxide; t h i s p e a k a p p e a r e d a f t e r 1 day of h y d r a t i o n ( F i g . 23) i n s t e a d of a f t e r 3 d a y s a s had b e e n the c a s e when t r i e t h a n o l a m i n e had been p r e s e n t . 90 d a y 3 d a y 1 d a y FIG. 23 X - r a y d i f f r a c t o g r a m s a t v a r i o u s t i m e s of h y d r a t i o n of synthetic c e m e n t p a s t e with 0. 5'3'0 c a l c i u m lignosulphonate, w/c = 0. 5. ( c u / N ~ , 45KV, 25mA. ) D i s c u s s i o n T h e p r o d u c t s f o r m e d by t h i s m u l t i c o m p o n e n t s y s t e m with no o r g a n i c a d m i x t u r e p r e s e n t , and t h e t i m e s a t which t h e s e p r o d u c t s f o r m e d , when i t w a s h y d r a t e d o v e r a p e r i o d of 3 m o n t h s , w e r e v e r y s i m i l a r t o t h o s e f o r m e d by t h e s i m p l e r s y s t e m , C,S, C 3 A and g y p s u m , d e s c r i b e d i n t h e p r e c e d i n g p a p e r of t h i s s e r i e s ( 3 ) . Again t h e e a r l y p r o d u c t a f t e r a few m i n u t e s of h y d r a t i o n w a s a n a m o r p h o u s film, pos sibly c o r r e s p o n d i n g in C/S r a t i o t o t h e o r i g i n a l Cg S . T h e i r r e g u l a r , f i b r o u s m a t e r i a l p r o b a b l y c o r r e s p o n d e d t o t h e l o w e r C/S s t a g e , and the p l a t e -like f o r m s t o t h e l a t e r , h i g h e r C/S p r o d u c t r e p o r t e d by o t h e r s
( 6 ,
7). T h e f a i l u r e t o positively identify Ca(OH)2s u g g e s t s t h a t t h e l i m e l i b e r a t e d i n t h e e a r l y r e a c t i o n , i n v e r y finely divided f o r m , i s taken into t h e CSH l a t t i c e i n s o m e m a n n e r ( 2 , 3, 7 ) . I t i s c l e a r
V o l . 1 , No. 4 MICROSTRUCTURE, CEMENT PASTE, ADMIXTURES
f r o m t h e s e s t u d i e s and the p r e v i o u s i n v e s t i g a t i o n s ( 1 - 3 ) t h a t both t h e CAH and CSH h y d r a t e s c a n and d o t a k e on c r y s t a l h a b i t s v e r y like t h o s e of w e l l - c r y s t a l l i z e d l i m e , and t h a t a l l s u c h c r y s t a l l i t e s have in t h e p a s t been m i s - takenly believed t o be Ca(OH),
.
The f r e e l i m e c a n o c c u r m o r e r e a d i l y , of c o u r s e , in s u s p e n s i o n s t h a n in p a s t e s ( 5 ) . O t h e r w o r k h a s i n d i c a t e d t h a t s i m i l a r l y o r i e n t e d l a t t i c e s of f o i l s of CSH l i n k r e a d i l y t o t h e t h r e e - d i m e n - s i o n a l n e t w o r k of Ca(OH), ( 1 4 ) .Significant a m o u n t s of the p l a t e - l i k e CSH p r o d u c t s a p p a r e n t l y do not develop a s e a r l y in t h i s s y s t e m a s in s o m e w h a t s i m i l a r s y s t e m s with a l i t e in p l a c e of C3S ( 4 ) . T h i s m a y be due t o the c l a i m e d h i g h e r a c t i v i t y of the a l i t e ( 5 ) o r t o t h e d i f f e r e n c e s in conditions, m a t e r i a l s o r p r o p o r t i o n s .
A r e l a t i v e abundance of p s e u d o m o r p h s of o r i g i n a l C3S p a r t i c l e s i n l a t e r s t a g e s of h y d r a t i o n , and a p p a r e n t l y f o r m i n g a n i n t e g r a l p a r t of t h e f i n a l m i c r o s t r u c t u r e of the p a s t e , w a s o b s e r v e d in t h i s study. Such p s e u d o m o r p h s do not a p p e a r t o be m e n t i o n e d by o t h e r r e s e a r c h e r s a s a m a j o r component. T h e i r o c c u r r e n c e m i g h t be i n t e r p r e t e d a s indicating t h a t hydration d o e s not o c c u r a s a t h r o u g h - s o l u t i o n p r o c e s s .
In t h i s m u l t i c o m p o n e n t s y s t e m t h e cubic f o r m of CAH did not a p p e a r a s i t d o e s in a hydrating p o r t l a n d c e m e n t s y s t e m . It h a s been o b s e r v e d ( 7 )
t h a t the p r e s e n c e of l a r g e a m o u n t s of C3S r e t a r d s t h e f o r m a t i o n of C3AH6; t h i s m a y be t h e explanation. C h a t t e r j i and J e f f e r y ( 4 ) did not r e p o r t the cubic f o r m in t h e i r s y s t e m of a l i t e , C 3 A , C,AF and gypsum, but did r e p o r t i t in the s a m e s y s t e m with n o g y p s u m p r e s e n t , with o r without t h e p r e s e n c e of a l k a l i . It i s concluded t h a t i n t h e i r s y s t e m s the g y p s u m h a s t a k e n up s o l a r g e a p r o p o r t i o n of the C3A h y d r a t e in producing the s u l p h o - a l u m i n a t e s t h a t not enough CAH i s l e f t t o p r o d u c e significant o r noticeable quantities of t h e cubic C3AH6. The s y s t e m in the p r e s e n t study a p p e a r s t o s u p p o r t t h i s . T h e p r e s e n t study did not r e v e a l t h e r a t h e r e x t e n s i v e v a r i a t i o n s i n m o r p h o l o g y and r a t e s one m i g h t have e x p e c t e d f r o m the l i t e r a t u r e on
s i m p l e r s y s t e m s . It i s believed t h a t the low diffusion r a t e s in s u c h a low w a t e r - c e m e n t r a t i o s y s t e m m a y have been a c o n t r i b u t o r y f a c t o r . A l s o , the v a r i o u s i n t e r a c t i o n s r e p o r t e d m a y t e n d t o d a m p e n out i n a m u l t i c o m p o -
V o l . 1, N o . 4
MICROSTRUCTURE, CEMENT PASTE, ADMIXTURES
nent s y s t e m s u c h a s w a s u s e d i n t h i s study. It should be r e c a l l e d t h a t only the p r e d o m i n a n t p r o d u c t s w e r e studied in t h i s s e r i e s , and a l s o t h a t t h e p r o p o r t i o n s of o r i g i n a l c o n s t i t u e n t s of m i x t u r e s in t h i s s y s t e m , a s w e l l a s i n t h e p r e v i o u s l y r e p o r t e d s y s t e m s , w e r e in the s a m e o r d e r a s n o r m a l l y found i n p o r t l a n d c e m e n t .
T h e r e w e r e definite d i f f e r e n c e s between the p a s t e s with the two different o r g a n i c a d m i x t u r e s , t r i e t h a n o l a m i n e and c a l c i u m lignosulphonate
,
in t h e i r r a t e s of r e a c t i o n , and in the p r o d u c t s t h e y f o r m e d , but no significant d i f f e r e n c e could be d e t e c t e d in the f i n a l m o r p h o l o g y of the p a s t e s .The p a s t e s , with and without the a d m i x t u r e s , u l t i m a t e l y t a k e on a c l o s e -packed m i c r o s t r u c t u r e ; the filling-in p r o c e s s o c c u r s in m u c h the s a m e way in both p a s t e s although the t i m i n g v a r i e s . A c h a r a c t e r i s t i c of t h i s d e n s e s t r u c t u r e i s the c l e a v e d , t a b u l a r m a s s m a d e up of the combined hydration p r o d u c t s , CH, CSH and CAH and p s e u d o m o r p h s of o r i g i n a l c o n s t i t - u e n t s . F u r t h e r i n t e r p r e t a t i o n of the a p p a r e n t l y pseudohexagonal p l a t e s t h a t f o r m the t a b u l a r m a s s e s i s provided in a s e p a r a t e publication (15) which i s b a s e d on the p r e s e n t and p r e v i o u s s t u d i e s ( 1 - 3 ) .
Conclusions
1 . The effect of e a c h of the a d m i x t u r e s , t r i e t h a n o l a m i n e and c a l c i u m lignosulphonate, on the h y d r a t i o n p r o c e s s e s of the s y n t h e t i c c e m e n t w a s v e r y pronounced, but not a s definite a s the e f f e c t s which w e r e a p p a r e n t d u r i n g t h e hydration of the m o n o m i n e r a l p a s t e s . T h i s w a s probably due t o the d i f f e r e n t action of e a c h a d m i x t u r e on e a c h of the m i n e r a l components a s well a s t o t h e influence of one m i n e r a l on t h e o t h e r .
2 . T h e h y d r a t i o n p r o c e s s e s with no a d m i x t u r e s p r e s e n t a p p e a r e d
t o be v e r y s i m i l a r t o t h o s e o c c u r r i n g with t r i e t h a n o l a m i n e and c a l c i u m lignosulphonate p r e s e n t .
3 . With c a l c i u m lignosulphonate i t w a s noted t h a t during the e n t i r e t i m e of h y d r a t i o n t h e r e w a s c o n s i d e r a b l y l e s s hydration of the c e m e n t
m i n e r a l s than when e i t h e r no a d m i x t u r e o r t r i e t h a n o l a m i n e had been u s e d . T h e s e hydration p r o d u c t s , h o w e v e r , d i s p l a y e d b e t t e r c r y s t a l habit. With
382 V o l . 1 , N o .
4
MICROSTRUCTURE, CEMENT PASTE, ADMIXTURESt r i e t h a n o l a m i n e m o r e h y d r a t i o n p r o d u c t s a p p e a r e d , but a t a l o w e r l e v e l of c r y s t a l l i n i t y .
X - r a y d i f f r a c t i o n e x a m i n a t i o n s showed t h a t the p r e s e n c e of c a l c i u m lignosulphonate p r o d u c e d p e a k s of c r y s t a l l i n e C H a t 1 d a y of h y d r a t i o n , c o m p a r e d with 3 d a y s f o r the t r i e t h a n o l a m i n e p a s t e . P e a k s of C H w e r e s m a l l e r with t r i e t h a n o l a m i n e t h a n t h o s e which o c c u r r e d with c a l c i u m lignosulphonate ( F i g s
.
17 a n d 23).4. T h e m o r p h o l o g y of t h e h y d r a t i o n p r o d u c t s , and t h e s e q u e n c e i n which t h e y f o r m e d d u r i n g t h e h y d r a t i o n p r o c e s s , did not d i f f e r s i g n i f i c a n t l y f r o m t h e p r o d u c t s of t h e s i m p l e r s y s t e m s , but t h e t i m e s of t h e i r a p p e a r a n c e w e r e dependent upon the a d m i x t u r e p r e s e n t .
5. A l m o s t a l l c h a n g e s o c c u r r e d within the f i r s t 7 d a y s of h y d r a - t i o n , and d u r i n g t h i s t i m e d i f f e r e n c e s in m i c r o s t r u c t u r e of s y n t h e t i c c e m e n t p a s t e a s c o m p a r e d with the m o n o m i n e r a l p a s t e s w e r e m o s t significant.
Acknowledgements
We acknowledge g r a t e f u l l y t h e i n v a l u a b l e c o n t r i b u t i o n of M r . E . Quinn i n p r e p a r i n g r e p l i c a s f r o m the s a m p l e s f o r e l e c t r o n m i c r o s c o p i c e x a m i n a t i o n . T o P o r t l a n d C e m e n t A s s o c i a t i o n f o r supplying the p u r e c o n s t i t u e n t s of c e m e n t we a r e a l s o m o s t g r a t e f u l .
T h i s p a p e r i s a contribution of t h e Division of Building R e s e a r c h , National R e s e a r c h C o u n c i l of C a n a d a and i s published with t h e a p p r o v a l of t h e D i r e c t o r of t h e Division. R e f e r e n c e s 1. T . D. C i a c h a n d E . G . S w e n s o n , C e m e n t a n d C o n c r e t e R e s . 1 , 143(1971). 2. T . D . C i a c h and E . G . S w e n s o n , C e m e n t and C o n c r e t e R e s .
1,
159 (1971). 3. T . D . C i a c h and E . G . S w e n s o n , C e m e n t and C o n c r e t e R e s .1,
257 (1971). 4. S. C h a t t e r j i a n d J . W. J e f f e r y , J . A m . C e r a m . Soc. 46, 187 (1963).-
V o l . 1 ,
No.
4 383 MICROSTRUCTURE, CEMENT PASTE, ADMIXTURES5. L. E . Copeland and D. L. K a n t r o , F i f t h Int. Symp. on t h e C h e m . of C e m e n t , Tokyo, 11, 387 (1968).
-
6. H. F. W. T a y l o r , F i f t h Int. Symp. on t h e C h e m . of C e m e n t , Tokyo,
11, 1 ( 1 9 6 8 ) -
-
J . G. M . d e J o n g , T h e I n t e r a c t i o n of T r i c a l c i u m S i l i c a t e and T r i - c a l c i u m A l u m i n a t e d u r i n g t h e i r Hydration. P h . D. T h e s i s , T e c h n i s c h e Hogeschol, Eindhoven, (1968). P. S e l i g m a n n a n d N. R . G r e e n i n g , Highw. R e s . R e c . No. 62, 80 (1964); P C A R e s . Dept. Bull. 185.B. Blank, D. R. R o s s i n g t o n and L. A. Weinland, J . A m . C e r a m . SOC.
-
46, 3 9 5 ( 1 9 6 3 ) .D o R. R o s s i n g t o n and E . J . Runk, J . A m . C e r a m . Soc.
a,
46(1968). J . F. Young, J . Am. C e r a m . Soc.-
52, 4 4 ( 1 9 6 9 ) .J . F. Young, M a g . C o n c r . R e s .
