Hydration kinetics of tricalcium silicate solid solutions at early ages

CEMENT and CONCRETERESEARCH. Vol. 8, pp. 6i-72, 1978. Pergamon Press, Inc Printed in the United States.

HYDRATION

KINETICS OF T R I C A L C I U M SILICATE SOLUTIONS AT EARLY AGES

G.L.Valenti,

V.Sabatelli,

SOLID

B.Marchese

Istltuto di Chimica A p p l i c a t a - F a c o l t ~ U n i v e r s i t ~ di N a p o l i - 8 O 1 2 5 Napoli

d'Ingegneria - Italy

(Refereed) (Received July 8; in final form Oct. 12, 1977) ABSTRACT The h y d r a t i o n kinetics, during the first 24 hours of reaction, of synthetic alites bearing AI, Fe, Mg has been followed by X-ray d i f f r a c t i o n and scanning electron microscopy. In respect to the pure t r i c a l c i u m silicate, lower h y d r a t i o n degrees, in p a r t i c u l a r for the AI - and Fe-alites, were found. The SEM m o r p h o l o g i c a l features of the n e w l y - f o r m e d products allowed the course of h y d r a t i o n for each sample to be followed and c o n f i r m e d the sequence of rea c t i v i t y pointed out by kinetic curves.

E' stata determinata, n e l l ' a r c o delle prime 24 ore di reazione, la c i n e t i c a di i d r a t a z l o n e di aliti sintetithe contenenti AI, F e e Mg, m e d i a n t e d l f f r a z i o n e dei raggi X e m i c r o s c o p i a e l e t t r o n i c a a scansione. Sono stati r i s c o n t r a t i valori del grado di i d r a t a z i o ne pi~ bassi di quelli del sillcato trlcalcico puro, p a r t i c o l a r m e n t e per le aliti c o n t e n e n t i alluminio e ferro. Le c a r a t t e r i s t i c h e m o r f o l o g i c h e dei prodotti di n e o f o r mazione, rilevate m e d i a n t e SEM, hanno p e r m e s s o di seguire q u a l i t a t i v a m e n t e l ' a n d a m e n t o della reazione di idratazione per ciascun camplone e di c o n f e r m a r e la sequenza dl r e a t t i v l t ~ messa in luce dalle curve clnetithe.

61

62

Vol. 8, No. 1 G. L. V a l e n t i , V. S a b a t e l l i ,

B. Marchese

Introduction As is k n o w n (I), (2), (3), (4), (5), (6), the p r e s e n c e of f o r e i g n ions in the t r i c a l c i u m s i l i c a t e l a t t i c e p r o m o t e s s i g n i f i cant d i f f e r e n c e s in the c r y s t a l l i n e s t r u c t u r e and h y d r a u l i c b e h a viour. As r e g a r d s the h y d r a t i o n k i n e t i c s , m a i n l y two kinds of res e a r c h h a v e b e e n p e r f o r m e d ; the first to e v a l u a t e the i n f l u e n c e of the m o d i f i c a t i o n s i n d u c e d by the m i n o r c o m p o n e n t s on the hyd r a t i o n m e c h a n i s m , d u r i n g the very early stages of r e a c t i o n (7), (8); the s e c o n d to c o r r e l a t e r e a c t i v i t y and m e c h a n i c a l s t r e n g t h after one day of h y d r a t i o n (9), (i0), (II). S y s t e m a t i c s t u d i e s c o n c e r n i n g a g i n g p e r i o d s lower than i day are not f r e q u e n t in the l i t e r a t u r e (12). A r e s e a r c h was t h e r e f o r e d e v e l o p e d to e v a l u a t e the influence that some ions, u s u a l l y o c c u r r i n g in the a l~tes of i n d u s t r i al c l i n k e r s , e x e r c i s e on the k i n e t i c s of h y d r a t i o n d u r i n g the first 24 h o u r s of r e a c t i o n . D i r e c t and i n d e p e n d e n t t e c h n i q u e s , such as X - r a y d i f f r a c t i on (XRD) and s c a n n i n g e l e c t r o n m i c r o s c o p y (SEM), were e m p l o y e d . I n d i r e c t m e t h o d s of e v a l u a t i n g the h y d r a t i o n d e g r e e , i.e. d e t e r m i n a t i o n of the heat of h y d r a t i o n or e v a l u a t i o n of the c a l c i u m hyd r o x i d e and "non e v a p o r a b l e " water, offer d i s a d v a n t a g e s since the c o m p o s i t i o n of the h y d r a t i o n p r o d u c t s is not c o n s t a n t d u r i n g such aging i n t e r v a l . Experimental The e x p e r i m e n t s w e r e c a r r i e d out on three a l i t e s c o n t a i n i ng 1% MgO, 1% A1203, 1% Fe203 and on pure t r i c a l c i u m s i l i c a t e , as r e f e r e n c e sample. Both pure C3S and its solid s o l u t i o n s were obtained by solid state r e a c t i o n s at 1550°C, e m p l o y i n g as s t a r t i n g mat e r i a l s CaC03, Si02, ( M g C O 3 ) 4 - M g ( O H ) 2 . S H 2 0 , AI(OH) 3, Fe203, r e a g e nt grade. The m i n o r oxide c o n c e n t r a t i o n s w e r e fixed so as not to e x c e e d their s o l u b i l i t y limits in t r i c a l c i u m s i l i c a t e , at 1550°C (13). The s t a r t i n g m i x t u r e s w e r e s i n t e r e d at 950°C for six hours, then g r o u n d and sieved t h r o u g h a 270 m e s h sieve. The p o w d e r s w e r e then p r e s s e d in Pt c r u c i b l e s , h e a t e d at 1550°C and f i n a l l y g r o u n d and sieved; this p r o c e d u r e was r e p e a t e d till the end of the reaction, c o n t r o l l e d by the free CaO e v a l u a t i o n . The final p r o d u c t s were g r o u n d to about 5000 Blaine. The m i n o r oxide c o n c e n t r a t i o n s w e r e c o n t r o l l e d by atomic a b s o r p t i o n s p e c t r o p h o t o m e t r y . The h y d r a t i o n r e a c t i o n s were c a r r i e d out at 20°C + I°C emp l o y i n g a w a t e r / s o l i d ratio of 0.50. At the end of the p r o g r a m m e d r e a c t i o n time, the h y d r a t i o n was s t o p p e d by i m m e r s i n g the specimens, e n c l o s e d in sealed p o l y t h e n e e n v e l o p e s , in a dry i c e - m e t h a nol m i x t u r e . Then the pastes were s u b m i t t e d to D - d r y i n g (14). Suitable a m o u n t s of the dried s a m p l e s were used to e v a l u a t e the loss on i g n i t i o n by h e a t i n g up to I050°C and the u n r e a c t e d C3S or alite by q u a n t i t a t i v e XRD a n a l y s i s , the i n t e r n a l s t a n d a r d b e i n g MgO. The

Vol. 8, No. l

63

HYDRATION KINETICS, C3S, SOLID SOLUTIONS

oF I

: .2 Q

30

O

C3S

A

C3S.

D

C]S-1.0%

F*20:

V

C3S.

t0%

AI203

I

I 8

1.0% M g O

*I o

~ 2°I

'°I [ 0

I 4

I

I 12

I

time.

Fig.

i 16

I

l 20

I

I 24

h

1

H y d r a t i o n degree of C3S and its solid solutions.

reference X-ray peaks were 4 1 . 3 ° 20 CuK= for the C3S or the elite and 43.O ° 20 CuK~ for the MgO. A third f r a c t i o n of each sample was submitted, after Au-Pd shadowing, to SEM, a JSM-212 JEOL scanning e l e c t r o n m i c r o s c o p e being used.

TABLE Hydration

rate

reacted moles ( starting moles

lutions at various tion of the curves Time

aging times in Fig. I)

I

. h x iOO) of C3S and its solid s o (data obtained by graphical

Hydration

deriva-

rate

(hours)

pure C3S

C3S+1% MgO

9

3.87

2 35

Ii

6.40

3 27

1.82

13

2.97

4 17

2.20

i .57

15

2.12

2 95

2.45

2.15

19

1.12

1 27

1.30

1.65

23

0.80

O 85

0.92

1.12

C3S+1% Fe203

C3S+1% AI203

64

Vol. 8, No. 1 G. L. V a l e n t i , V. S a b a t e l l i , Results

and

B. Marchese

Discussion

The pure t r i c a l c i u m s i l i c a t e shows (Fig.l) the h i g h e s t hyd r a t i o n degree; the M g - a l i t e , the F e - a l i t e and the A l - a l i t e follow in that order. The i day v a l u e s of the F e - a l i t e and the A l - a life are a p p r e c i a b l y lower, about 30%, than those shown by the pure t r i c a l c i u m s i l i c a t e and the M g - a l i t e , r e s p e c t i v e l y . The m a x i m u m h y d r a t i o n rate was reached, T a b l e I, in the s h o r t e s t time by the pure t r i c a l c i u m s i l i c a t e , in the l o n g e s t time by the A l - a n d F e - a l i t e s . The s e q u e n c e of the m a x i m u m h y d r a t i o n rates was in d e c r e a s i n g order: pure C 3 S > M g - a l i t e > F e - a l i t e > A l - a l i t e . Kondo and Y o s h i d a (12), did not find d i f f e r e n c e s in the hyd r a t i o n degree, e v a l u a t e d by XRD a n a l y s i s after 9; 15; 24 hours of r e a c t i o n , b e t w e e n a pure t r i c a l c i u m s i l i c a t e and an alite cont a i n i n g both 2.14% MgO and 1.01% A I 2 0 3 in solid s o l u t i o n . T h o m p son et al. (15) s t u d i e d the r e a c t i v i t y of a l i t e s w i t h v a r i a b l e MgO a m o u n t s , in terms of heat of h y d r a t i o n e v o l v e d d u r i n g the first 35 hours. For a l i t e s c o n t a i n i n g up to about 1% MgO a d e c r e a s e of r e a c t i v i t y in c o m p a r i s o n w i t h pure t r i c a l c i u m s i l i c a t e was noticed. F i e r e n s et al. (16), owing to the i n t r o d u c t i o n of Fe203 in the t r i c a l c i u m s i l i c a t e l a t t i c e , o b s e r v e d a c o n s i d e r a b l e d e c r e a s e of the r e a c t i o n rate as e v a l u a t e d in terms of Ca ++ c o n c e n t r a t i o n in the liquid phase. The lower h y d r a t i o n rate s h o w n by the F e - a n d A l - a l i t e s may be c o n n e c t e d w i t h the h i g h e r m e c h a n i c a l s t r e n g t h found by S e r s a l e (17), in a c c o r d a n c e w i t h the w e l l - k n o w n i n c r e a s e of m e c h a n i c a l s t r e n g t h i n d u c e d by r e t a r d e r s . Microscopical observations, Figs. 2, 3, 4, 5 and 6, give qual i t a t i v e c o n f i r m a t i o n of our above m e n t i o n e d r e s u l t s . The m i c r o g r a p h s , r e p o r t e d in Fig. 2, c h a r a c t e r i z e the samples in the a n h y d r o u s phase, as r e g a r d s b o t h the grain forms and the s u r f a c e c o n d i t i o n s . No a p p r e c i a b l e d i f f e r e n c e s w e r e n o t i c e d among the s a m p l e s in the a n h y d r o u s state; such o b s e r v a t i o n s are h o w e v e r u s e f u l in d i s t i n g u i s h i n g even s l i g h t d i f f e r e n c e s in the surface conditions, a r i s i n g f r o m the p r e s e n c e of n e w l y - f o r m e d products in the s a m p l e d u r i n g the h y d r a t i o n . The first h y d r a t i o n signs can be o b s e r v e d after 1.5 hours in the t r i c a l c i u m s i l i c a t e and M g - a l i t e s a m p l e s and, in m i n o r amount, in the F e - a l i t e sample, Fig. 3. T o g e t h e r w i t h the p a r t i c l e s still a n h y d r o u s , a l r e a d y shown in Fig. 2, f i b r i l l a r p a r t i c l e s long about l~m appear. It may be s u p p o s e d these forms arise from the c o n d e n s a t i o n of n u c l e i (18) and their m o r p h o l o g i e s d e p e n d on various factors. T h e s e p a r t i c l e s r e s e m b l e those o b s e r v e d in v a r i o u s Portland

cement

pastes

by D i a m o n d

(19)

and

named

"Type

I" p a r t i c l e s

Filamentous particles, long and thin, have b e e n r e c e n t l y o b s e r ved in a "wet" cell by m e a n s of I MeV e l e c t r o n m i c r o s c o p e ~ [ The m o r p h o l o g y of the s a m p l e s h y d r a t e d for 6 h o u r s is dep i c t e d in Fig. 4. The g r a i n s u r f a c e seem to be d e e p l y a l t e r e d and new m o r p h o l o g i e s appear. Pure C3S shows c o n s p i c u o u s l e n t i cular p a r t i c l e s ; the same p a r t i c l e s a p p e a r in the s a m p l e s with

::3

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r~ :3" m

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LF) 0 r-

L~ 0 r"

L,J LF)

o,1

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CD Lt~ CD

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--t

Z

Z

--t .....-4

"1-

0

0

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68

Vol. 8, ;io. I G. L. V a l e n t i , V. S a b a t e l l i ,

B. Marchese

m a g n e s i u m and iron, but fewer in n u m b e r and t o g e t h e r w i t h those a l r e a d y n o t i c e d a f t e r 1.5 hours of h y d r a t i o n . In A l - a l i t e c h a n ges in the g r a i n ' s s u r f a c e a p p e a r more d i s t i n c t a l o n g the b o r d e rs, but there is no e v i d e n c e of forms like those above m e n t i o n e d . The l e n t i c u l a r p a r t i c l e s b e l o n g to the d e n d r i t i c type and are c o n n e c t e d w i t h a h i g h rate of g r o w t h (21); their d e v e l o p m e n t may be r e l a t e d to the g r e a t e r slope of the c o r r e s p o n d i n g k i n e t i c curve, Fig. I. On the o t h e r hand, it s h o u l d be m e n t i o n e d that t r i c a l c i u m s i l i c a t e shows m a x i m u m heat e v o l u t i o n a b o u t six hours after the h y d r a t i o n (22). A f t e r 12 h o u r s of h y d r a t i o n , Fig. 5, pure t r i c a l c i u m silicate shows l a n c e o l a t e p a r t i c l e s , c o l l e c t e d in s p h e r u l i t i c a g g l o m e r a t i o n s ; the M g - a l i t e shows the same a g g l o m e r a t i o n s and the same p a r t i c l e s , even t h o u g h of s l i g h t l y s m a l l e r size; the F e - a l i t e shows m o r p h o l o g i c a l c h a r a c t e r i s t i c s of the same type but not well o u t l i n e d and fewer in number. A l - a l i t e p r e s e n t s p a r t i c l e s r e s e m b l i n g those o b s e r v e d a f t e r 6 h o u r s of h y d r a t i o n in the s a m p l e s c o n t a i n i n g m a g n e s i u m and iron. A f t e r 24 hours, Fig. 6, pure C3S shows quite large a g g l o m e r a t i o n s , t o g e t h e r w i t h i s o l a t e d p a r t i c l e s u n c h a n g e d in size. These areas a r i s e from the c o a l e s c e n c e of the s p h e r u l i t i c p a r t i c l e s and may be c o n s i d e r e d as c o n t r i b u t i n g most to the i n c r e a s e in mec h a n i c a l s t r e n g t h (23), (24). The f e a t u r e s of the M g - a l i t e are very s i m i l a r to those of pure C3S even t h o u g h the i n d i v i d u a l p a r t i c l e s are s m a l l e r in size, as a l r e a d y found after 12 hours of h y d r a t i o n . The F e - a l i t e shows the same m o r p h o l o g i c a l f e a t u r e s that pure C3S and M g - a l i t e showed a f t e r 12 h o u r s of h y d r a t i o n . The A l - a l i t e d i s p l a y s a n a l o g i e s w i t h the F e - a l i t e . The m i c r o g r a p h s in Fig~. 6C and 6C', show the outer part c o n s i s t i n g of the n e w l y - f o r m e d p r o d u c t s in d o m p a r i s o n w i t h the inner part still a n h y d r o u s , and the c o n s i d e r a b l e s e p a r a t i o n b e t w e e n them. Conclusions D u r i n g the first 24 hours of r e a c t i o n the h y d r a t i o n k i n e tics of the t r i c a l c i u m s i l i c a t e is c o n s i d e r a b l y i n f l u e n c e d by for e i g n ions such as AI, Fe, Mg in solid s o l u t i o n . The h y d r a t i o n d e g r e e of the a l i t e s is a l w a y s lower than that of the pure t r i c a l c i u m s i l i c a t e . The d e c r e a s e is more r e m a r k a b l e for the F e - a n d A l - a l i t e s and less n o t i c e a b l e for the M g - a l i re. The SEM o b s e r v a t i o n s c o n f i r m e d q u a l i t a t i v e l y the s e q u e n c e p o i n t e d out by the k i n e t i c c u r v e s . It was p o s s i b l e in s l o w e r hyd r a t i n g s a m p l e s to d i s t i n g u i s h m o r p h o l o g i c a l and d i m e n s i o n a l fea t u r e s c l o s e to those shown, at s h o r t e r times, by f a s t e r h y d r a ting

ones. Acknowledgements The

authors

would

like

to a c k n o w l e d g e

the

financial

suppo-

Vol. 8, No. 1

69 HYDRATION KINETICS, C3S, SOLID SOLUTIONS

Fig, SEM's of the specimens

5 hydrated

for 12 h.

Vol. 8, ~',io.

70 G. L. Valenti, V. S a b a t e l l i , B. Marchese

a~ i

Fig. SEM's

of

the

specimens

6 hydrated

for

2G h.

1

Vol. 8, No. 1

71

HYDRATION KINETICS, C3S, SOLID SOLUTIONS

rt of the "Consiglio Nazionale Prof. R.Sersale for his useful for his technical assistance.

delle Ricerche". Thanks are due to discussions and to Mr. A.Annetta

References I) M.Regourd, A.Guinier, Moscow (1974). 2) W.Eysel,

Th. Hahn,

VI Intern.Cong. Chem. Cement.l,

E.Woermann,

J.Amer. Ceram. Soc.50,

609

3) R.W.Nurse, H.G.Midgley, W.Gutt, K.Fletcher, Higway Board, Special Report 90, 258 Washington (1966). 4) G.Mascolo, B.Marchese, 56, 222 (1973).

G.Frigione,

R.Sersale,

V.S.Ramachandran,

Mater.Constr.

7) T.Sakurai, T.Sato, A.Yoshinaga, I, 300, Tokyo (1968).

Research

Portland

8, 373-376

Cement,

(1975).

Proc.V.Intern. Cong. Chem. Cement

8) JoDescamps, P.Fierens, J.P.Verhaegen, nt, II, Suppl.Paper, Moscow (1974).

VI Intern. Cong. Chem. Ceme-

9) Yu.M.Butt., V.V.Timashev, V.E.Kaushanski, te Ind., 59, Budapest (1968). I0) W.Kurdowski,

(1967).

J.Amer.Ceram. Soc.

5) G.Yamaguchi, K.Shirasuka, T.Ota, Symp. Structure Highway Res. Board 263-268, Washington (1966). 6) G.Mascolo,

Princ.Paper,

VI Intern. Cong. Chem.

Cement,

Proc.gth

Conf.

Silica-

I, Suppl.Paper,

Moscow

(1974). ii) J.H.Welch, W.Gutt, shington (1960).

Proc. IV Intern. Symp. Chem.

12) R.Kondo, K.Yoshida, kyo (1968). 13) E.Woermann,

Th. Hahn,

Proc.V.Intern. Cong. Chem. W.Eysel,

14) L.E.Copeland,

J.C.Hayes,

15) R.A.Thompson, 54-57 (1975).

D.C.Killoh,

16) P.Fierens, (1972).

M.Thauvoye,

17) R.Sersale, Proc. Moscow (1974).

Cement

Zement-Kalk-Gips

ASTM Bull.No.194, J.A.Forrester,

J.P.Verhaegen,

59-67,

Cement,l, 16,

70-74

Wa-

262 To-

370-375

(1963)

(1953).

J.Amer.Ceram. Soc.

II Cemento 69,

58,

211-222

VI Intern. Cong. Chem. Cement. Suppl.Paper

11-3

18) L.G.Shpymova, V.l. Sinenkaya, V.I.Chirk, l.l.Nikonets, Proc. Symp. VI Intern. Cong. Chem. Cement, Section II, Suppl.Paper,Moscow (1974). 19) S.Diamond,

Proc.Conf.Univ. Sheffield

8-9 April

(1976).

72

Vol. 8, No. 1 G. L. V a l e n t i ,

V. S a b a t e l l i ,

20) D.D.Double,

A.Hellawell,

Nature

21) A.Van Hook, (1961).

Cristallization,

22) M.E.Tadros, (1976).

J.Skalny,

R,S.

B. Marchese

261,

141,

486-8

Reinhold

Kalyoncu,

II Cemento 73,

195-208

Publ.Corp.

J.Am. Ceram. Soc.

23) R.Hedin, Proc. Vl Intern. Cong. Chem. Cement, Paper, Moscow (1974). 24) B,Marchese,

(1976).

(1976).

Section

New York 5_99, 344-346

II,

Suppl.