The influence of Na2O on the hydration of C3A I. Paste
hydration
Citation for published version (APA):
Spierings, G. A. C. M., & Stein, H. N. (1976). The influence of Na2O on the hydration of C3A I. Paste hydration. Cement and Concrete Research, 6(2), 265-272. https://doi.org/10.1016/0008-8846(76)90124-1
DOI:
10.1016/0008-8846(76)90124-1
Document status and date: Published: 01/01/1976
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THE INFLUENCE OF Na20 ON THE H Y D R A T I O N OF C3A. I. PASTE H Y D R A T I O N
G.A.C.M. Spierings and H.N. Stein Laboratory of General C h e m i s t r y
Technological University, Eindhoven, The Netherlands
(Communicated by H. F. W. Taylor) (Received Dec. 2, 1975)
ABSTRACT
The influence of Na~O on the h y d r a t i o n of C3A was studied both by following t~e hydration of x N a 2 0 . ( 3 - x ) C a O . A 1 2 0 3
(0<x<0.25) in water, and of C~A in solutions of NaOH. Low NaOH c o n c e n t r a t i o n s prevent a very early a p p e a r a n c e of the second heat evolution peak, indicating a m o r e
controlled formation of C~AH~ nuclei. Higher NaOH
c o n c e n t r a t i o n s advance th~ s~cond peak; this is ascribed to a d e c r e a s e d stability of the hexagonal hydrates with increasing NaOH concentrations.
Der Einfluss von NagO auf die H y d r a t a t i o n des C3A wurde untersucht sowohl mlttels der H y d r a t a t i o n von
xNa~O.(3-x)CaO.Al203 (0<x<0.25) in Wasser und von C 3 A in NaOB-L~sungen.
Niedrige N a O H - K o n z e n t r a t i o n v e r h i n d e r n ein sehr fr~hes
Auftreten des zweiten WMrmeentwicklungspeaks; dieses
deutet auf eine besser beherrschte Keimbildung des C~AH 6 hin. H~here N a O H - K o n z e n t r a t i o n e n verfr~hen den zwei£en Peak; d i e s e s w i r d einer abnehmenden Stabilit~t der hexagonalen Hydrate mit steigender N a O H - K o n z e n t r a t l o n
zugeschrieben.
266 Vol. 6, No. 2 G. A. C. M. Spierings, H. N. Stein
I n t r o d u c t i o n
The a l k a l i e s in a p o r t l a n d c e m e n t c l i n k e r h a v e a d i s t i n c t i n f l u e n c e on t h e s t r e n g t h d e v e l o p m e n t of a c e m e n t p a s t e p r e p a r e d
f r o m it (1,2). A s a f i r s t step in u n d e r s t a n d i n g this e f f e c t the
i n f l u e n c e of a l k a l i e s on the h y d r a t i o n m e c h a n i s m of p o r t l a n d c e m e n t m i n e r a l s has to be studied.
The a l k a l i e s c a n be i n c o r p o r a t e d i n t o a n u m b e r of p h a s e s in
the c l i n k e r . P a r t of the N a ~ O is n o r m a l l y t a k e n up by the C3A.
R e c e n t w o r k (3,4) has s h o w n ~hat t h e r e e x i s t s e v e r a l s e r i e s of s o l i d s o l u t i o n s of g e n e r a l f o r m u l a xNa20. ( 3 - x ) C a O . A l ~ O ~ , of w h i c h a c u b i c o n e w i t h 0 < x < 0 . 0 8 , an o r t h o r h o m b i c o n e w i t h 0 7 1 5 < x < 0 . 2 0 and a m o n o c l i n i c one w i t h 0 . 2 0 < x < 0 . 2 5 are r e l e v a n t to the p r e s e n t
i n v e s t i g a t i o n . W h e n 0 . 0 8 < x < 0 . 1 6 a m i x t u r e of two p h a s e s is found.
S o m e a s p e c t s of the i n f l u e n c e of N a ~ O on the h y d r a t i o n of C3A h a v e b e e n i n v e s t i g a t e d (5-9) but no d e t a i l e d study has b e e n
r e p o r t e d . The p r e s e n t i n v e s t i g a t i o n d e a l s w i t h t h e p a s t e h y d r a t i o n
of C3A in s o l u t i o n s of NaOH and of xNa20. ( 3 - x ) C a O . A l 2 0 3 in water. E x p e r i m e n t a l
M e t h o d s
S p e c i f i c s u r f a c e w a s d e t e r m i n e d by N~ a d s o r p t i o n in an A r e a m e t e r ("Str~hlein") . F r e e l i m e w a s d e t e r m i n e d by the m e t h o d
of P r e s s l e r et al. (I0). S c a n n i n g e l e c t r o n m i c r o g r a p h s (SEM) w e r e
m a d e u s i n g a C a m b r i d g e M K - 2 A i n s t r u m e n t .
X - r a y a n a l y s i s w a s p e r f o r m e d u s i n g a P h i l i p s d i f f r a c t o m e t e r
P W I 0 1 0 w i t h f i l t e r e d Cu r a d i a t i o n ; the q u a n t i t i e s of t h e c o m p o u n d s
p r e s e n t w e r e e s t i m a t e d f r o m the i n t e n s i t i e s of c h a r a c t e r i s t i c peaks, w h i c h are g i v e n in a r b i t r a r y u n i t s ( v v w < v w < w < m w < m < m s < s < v s ) . The p e a k s used w e r e the same as t h o s ~ u s e d b y C o r s t a n j e , S t e i n and S t e v e l s (11) t o g e t h e r w i t h the 10.7 K p e a k for C 2 A H 8.
I s o t h e r m a l c a l o r i m e t r y w a s p e r f o r m e d at 25°C as d e s c r i b e d
p r e v i o u s l y (12). T h e p a s t e s w e r e p r e p a r e d and the h y d r a t i o n
r e a c t i o n s a r r e s t e d as d e s c r i b e d by de Jong, S t e i n and S t e v e l s (I 3). C a l c i u m w a s d e t e r m i n e d b y a s p e c t r o p h o t o m e t r i c t i t r a t i o n m e t h o d
(Slanina et al. (15)) S o d i u m w a s d e t e r m i n e d u s i n g a s o d i u m ion
e l e c t r o d e (Swasey ( 1 6 ) . M a t e r i a l s
The N a 2 0 c o n t a i n i n g C ~ A s a m p l e s w e r e p r e p a r e d f r o m m i x t u r e s
of C a C O ~ (p.a. M e r c k ) , A I 2 0 ~ (U.C.B.; loss on i g n i t i o n 0.57%) and
N a 2 C O 3 ~p.a. M e r c k ) . T h e s £ a r t i n g m a t e r i a l s w e r e m i x e d in an
a g a t e b a l l m i l l , h e a t e d tree t i m e s in p l a t i n u m c r u c i b l e s for two
h o u r s at 1 3 2 5 ° C w i t h i n t e r m e d i a t e g r i n d i n g , and sieved. The
f r a c t i o n s w i t h p a r t i c l e s s m a l l e r t h a n 36 ~ m w e r e used. C 3 A w a s
p r e p a r e d as d e s c r i b e d by de Jong, S t e i n and S t e v e l s (13). T a b l e I
c o n t a i n s s o m e d a t a for t h e m a t e r i a l s .
A c c o r d i n g to R e g o u r d and G u i n i e r ( 3 ) , C q A and N O 0 5 C 2 Q5 A are
c u b i c w h i l e N^ ^~C. 75 A is m o n o c l i n i c , a n d N^ .~C~ ~ ' A a ~ x t u r e
of the c u b i c ~ D o r ~ h o r h o m b i c p h a s e s . T h e s a m p - e s w e e
c h a r a c t e r i z e d by t h e i r X - r a y d i f f r a c t o g r a m s w h i c h a g r e e d c o m p l e t e l y w i t h t h e d a t a g i v e n by R e g o u r d and G u i n i e r .
t e m p e r a t u r e s h o r t l y b e f o r e use. The a l k a l i h y d r o x i d e s o l u t i o n s w e r e p r e p a r e d from L i O H . H 2 0 (Koch light >99%), N a O H and KOH
(Titrisol Merck) and RbOH (Koch light >99.8%). The NaAI(OH)
s o l u t i o n s w e r e p r e p a r e d by d i s s o l v i n g A1 r i b b o n (p.a. M e r c k ) 4 i n
a q u e o u s N a O H solution. A l l p r e p a r a t i o n s w e r e c a r r i e d out using a
g l o v e b o x w i t h a N 2 - a t m o s p h e r e free f r o m C O 2. TABLE I D a t a on M a t e r i a l s E m p l o y e d S p e c i f i c F r e e C a / N a s u ~ f a ~ e lime cm g % T h e o r e t i c a l A n a l y s i s C A 3210 0.3 . . . . 3 N 0 05 2 . 9 5 ~ C 2890 <0.1 2 7. 5 28 1 . N "
0.15 2.85
c 3 0 6 0 0.3 9.5 10 6N0.25C2.75a
2670
0.7
5.5
6.0
H y d r a t i o n of C 3 A in S o l u t i o n s of A l k a l i H ~ d r o x i d e or H y d r o x 6 a f u m i n a t e R e s u l t sFig. I gives t y p i c a l heat e v o l u t i o n c u r v e s for p a s t e s (w/s =
I) m a d e w i t h C 3 A and w a t e r or a q u e o u s NaOH. In Fig. 2, the time
020 [
i!0.15
u~
0.I0
8 o.os I I I I I I/
'l[lO~H
%\'
1 2 3Time (h)
FIG. I H e a t e v o l u t i o n rates of p a s t e s (w/s = 1) m a d e u s i n g w a t e r and a q u e o u s N a O H "~8C " U C O O O E ~0( E E ,,. 2( O E ° ~ o o o I o:',8
\
o v ~ I I I I I 0.25 0.5 I 2 3 NaOH concentration M FIG. 2 T i m e of s e c o n d h e a t e v o l u t i o n peak268 Vol. 6, No. 2 G. A. C. M. Spierings, H. N. Stein
of the second neat e v o l u t i o n peak is p l o t t e d against NaOH
concentration. Heat e v o l u t i o n in the first 15 m i n u t e s d e c r e a s e s
w i t h i n c r e a s i n g NaOH c o n c e n t r a t i o n . W i t h w a t e r or NaOH less
c o n c e n t r a t e d than about 0.5M, the time of the second peak is not
very reproducible. W i t h m o r e c o n c e n t r a t e d NaOH, the
r e p r o d u c i b i l i t y is m u c h better, and the o c c u r e n c e of this peak at
very short times is prevented. The time of the second peak falls
with c o n c e n t r a t i o n above IM. Mori et al. (6) also found this.
X - r a y results (Table II) show that C3AH 6 is formed w i t h i n 10
m i n u t e s and that its amount increases wit~ tlme thereafter. At
short times the amount is v i r t u a l l y i n d e p e n d e n t of NaOH
concentration. H e x a g o n a l h y d r a t e s w e r e only once found (after
20h in 2N NaOH) with X-rays, but the SEM (Figs. 3 and 4) showed
the p r e s e n c e after 10 m i n u t e s of h y d r a t e s other than C3AH 6. T h e s e
had a platey h a b i t r e m i n i s c e n t of that of h e x a g o n a l hydrates. The absence of the c h a r a c t e r i s t i c X - r a y peaks i n d i c a t e s that h e x a g o n a l hydrates, if formed, are m u c h disordered.
The effect of v a r y i n g the alkali c a t i o n was studied u s i n g 2M
solutions. The only o b s e r v e d effect was a small d e c r e a s e in heat
e v o l u t i o n rate over the w h o l e p e r i o d of h y d r a t i o n w h e n the cation radius was increased.
Fig. 5 shows the effect of adding NaAI(OH) 4 as w e l l as NaOH. The second heat e v o l u t i o n peak is d e p r e s s e d a n d - s l i g h t l y retarded.
D i s c u s s i o n
A d d i t i o n of NaOH lowers the s o l u b i l i t y of Ca(OH)~ and
i n c r e a s e s that of AI(OH) 3. Berger, K o t s u p a l o and P u s ~ n y a k o v a (161
found that aqueous alkall p a r t l y d e c o m p o s e s C3AH 6 to give Ca(OH) 2 C4AH1. and a l u m i n a t e ions in solution, but Jones (17) found in a s£udyJof the C - A - N - H system that C3AH 6 is s t a b l e in I% NaOH, even
~ ° FIG. 3 S E M of C 3 A h y d r a t e d for 10 m i n u t e s in w a t e r FIG. 4 SEM of C q A h y d r a t e d for 10 m i n u ~ e s in 2M NaOH
T a b l e II X - r a y D a t a o n P a s t e H y d r a t i o n of C 3 A in R w a t e r and N a O H s o I u t i o n s N a O H H y d r a t i o n C 3 A C 2 A H 8 C 3 A H 6 (M) t i m e (min) 0 I 0 vs - v w 0 30 vs - m 0 120 s - s 0.04 I 0 vs - vw 0.2 I 0 vs - v w 0.2 50 vs - m w 0.2 1200 vs v v w m R N e i t h e r C a ( O H ) ~ nor C 4 A H x was ever d e £ e c t e d . T .06
ro
c o ~ .02 o U l 0 " r m i i \[~
\\\
. z . r oil
x ~'x ~ ~ [ I I 1 2 3 Time (h) FIG. 5 Heat e v o l u t i o n r a t e s of p a s t e s (w/s = I) c o n t a i n i n g b o t h N a O H (2M) and NaAI(OH) 4 of c o n c e n t r a t i o n s s h o w nat low a l u m i n a t e ion c o n c e n t r a t i o n s . The r e s u l t of B e r g e r ,
K o t s u p a l o and P u s h n y a k o v a _ c a n be a s c r i b e d to the i n i t i a l a b s e n c e
in the s o l u t i o n of AI(OH) 4 . It n e v e r t h e l e s s seems s t r a n g e t h a t no
s o l i d Ca(OH) 2 c o u l d b e d e ~ e c t e d in the p r e s e n t work.
R e t a r d a t i o n of the h y d r a t i o n r e a c t i o n a f t e r the f i r s t p e a k is g e n e r a l l y a t t r i b u t e d to ~ p r m a t i o n of a l a y e r of h y d r a t e s , w h i c h
i m p e d e s the p a s s a g e of C a ' - and a l u m i n a t e ions i n t o s o l u t i o n . The
S E M r e s u l t s (Figs. 3 a n d 4) c o n f i r m t h a t such a layer is formed. H o w e v e r , m i s f i t b e t w e e n C ~ A a n d h e x a g o n a l h y d r a t e s as r e g a r d s i n t e r a t o m i c d i s t a n c e s a n d - h a b i t s w i l l m a k e it d i f f i c u l t to o b t a i n a fit o n an a t o m i c scale, and s o m e s p a c e w i l l e x i s t b e t w e e n the
C ~ A and the h y d r a t e c r y s t a l s . S o m e r e t a r d a t i o n m e c h a n i s m s
c ~ m p a t i b l e w i t h t h e e x i s t a n c e of such a s p a c e w i l l b e d i s c u s s e d in a later p a p e r (18).
The e x i s t e n c e of the s e c o n d h e a t e v o l u t i o n p e a k is g e n e r a l l y
a t t r i b u t e d t o r e c r y s t a l l i z a t l o n of this layer. T h e e f f e c t of
a l k a l i in p r e v e n t i n g the v e r y e a r l y o c c u r e n c e of this p e a k can be a t t r i b u t e d t o r e t a r d a t i o n of the h y d r a t i o n of the C ~ A w h i c h c o u l d
be e x p e c t e d t o c a u s e a m o r e c o n t r o l l e d g r o w t h of C3~d{ 6 nuclei.
The f a c t t h a t the a m o u n t of C 3 A H ~ f o r m e d in the f i r s t 10 m i n u t e s d o e s not d e p e n d o n N a O H c o n c e n t r a t i o n i n d i c a t e s t h a t the
n u c l e a t i o n of C 3 A H ~ is not m a r k e d l y a f f e c t e d by t h e t y p e of
a l u m i n a t e ion p r e s e n t in t h e solution. The e a r l i e r a p p e a r a n c e of
the s e c o n d p e a k at h i g h a l k a l i c o n c e n t r a t i o n m i g h t b e c a u s e d b y c h a n g e s in t h e n u c l e u s g r o w t h r a t e of C ~ A due to h i g h e r a l u m i n a t e
c o n c e n t r a t i o n s . H o w e v e r , the s e c o n d p e a k does not o c c u r s o o n e r
w h e n NaAI(OH).- is a d d e d i n i t l a l l y (Fig. 5); t h e r e f o r e t h e e a r l i e r
o c c u r e n c e of ~ h e s e c o n d p e a k is a t t r i b u t e d to c h a n g e s in the r a t e at w h i c h A I ( O H ) 4 p a s s e s into s o l u t i o n f r o m t h e h e x a g o n a l h y d r a t e s .
270 Vol. 6, No. 2
•0.0@
To 0~06 . $ . , r , , ,8
o.o~ -g o LIJ .,., 002-r
G. A. C. M. Spierings, H. N. Stein I I I C3A I \ - - - N0.05C2.95 A I \ -o.-o- N C A \ 0.15 2.85 % I ~ - x - x - N0.25C2.75 At .
1 2 3 Time (h) FIG. 6 H e a t e v o l u t i o n r a t e s for p a s t e s of w a t e r andNxC3_xA p r e p a r a t i o n s
A t , - - ~" 0.0 8 r~ t u trl 0.06 (Mg
0.0~ >, .,_. 0.02: - r I I N0~ 5 C2.95A + N0.15 C2 85 A .... ~005C2 95 A + N02~275A \"-\
I 1 I 1 2 3 T,me (h) FIG. 7 H e a t e v o l u t i o n r a t e s for p a s t e s of w a t e r a n d m i x t u r e s of N x C 3 _ x A p a s t e s H y d r a t i o n . o f x N a 2 0 . ( 3 - x ) C a O . A l 2 ~ 3 S o l i d S o l u t i o n s Figs. 6 a n d 7 g i v e h e a t e v o l u t i o n c u r v e s for s e v e r a l p r e p a r a t i o n s and m i x t u r e s t h e r e o f . A s w i t h h y d r a t i o n of C ~ A in N a O H s o l u t i o n s , N a T O c a u s e s t h e f i r s t p e a k t o o c c u r l a t e r £ h o u g h no i n c r e a s e in t h e - e f f e c t w i t h N a 2 0 c o n t e n t w a s o b s e r v e d b e y o n d x = 0.05 d e s p i t e t h e v a r i a t i o n s in c r y s t a l s t r u c t u r e . M o r i et al. (6) f o u n d a s i m i l a r e f f e c t . T h e s e c o n d p e a k o c c u r r e d s o o n e r at h i g h N a 2 0 c o n t e n t s . X - r a y r e s u l t s (Table III) s h o w e d t h a t C ~ A H R w a s f o r m e d i n i t i a l l y . T h e a m o u n t d e c r e a s e d a f t e r t h e s ~ c o ~ d p e a k and n o n e w a s f o u n d a f t e r 48 h. A S E M (Fig. 8) of a p r e p a r a t i o n w i t h x = 0.25 h y d r a t e d for 50 m i n u t e s s h o w e d p a r t i c l e s c o a t e d w i t h t y p i c a l h e x a g o n a l p l a t e s . W h e n t h e s e N a 2 0 - c o n t a i n i n g p h a s e s h y d r a t e a l k a l i h y d r o x i d e a c c u m u l a t e s in t h e s o l u t i o n . T h e c o n c e n t r a t i o n d e p e n d s on x, the t i m e or d e g r e e _ o f h y d r a t i o n , a n d t h e a m o u n t of w a t e r left. A t w / s = I t h e OH c o n c e n t r a t i o n c o u l d e a s i l y r e a c h 0.5-I M; for e x a m p l e , if in a p a s t e of N^ ~.C~ ~5 A t h a t is 33% h y d r a t e d , a n d a s s u m i n g no c h a n g e in v o l u m ~ ' 6 ~ ~ l i q u i d p h a s e , t h e O H - c o n c e n t r a t i o n is a b o u t IM. T h e a l k a l i w i l l h a v e s i m i l a r e f f e c t s to t h o s e f o u n d o n h y d r a t i o n of p u r e C 3 A in N a O H s o l u t i o n s b u t the s i t u a t i o n is m o r e c o m p l e x b e c a u s e t h e a l k a l i h y d r o x i d e c o n c e n t r a t i o n in s o l u t i o n v a r i e s w i t h time. T h e f a c t t h a t t h e m i x t u r e of p r e p a r a t i o n s w i t h x = 0.05 a n d x = 0.25 b e h a v e s in m u c h t h e s a m e w a y as t h e p r e p a r a t i o n w i t h x =T A B L E III X - r a y D a t a o n P a s t e H y d r a t i o n of N 0 . 2 5 C 2 . 7 5 A~
H y d r a t i o n
C3A C2AH
8 C3AH
6
t i m e (h) 0.83 vs m m 2.50 s w s 48 s - vs I C 4 A H x w a s not found. FIG. 8 SEM of N 0 . 2 5 C 2 . 7 5 A h y d r a t e d for 50 min. in wa~_r~=
0.15 i n d i c a t e s t h a t the e f f e c t s are d e t e r m i n e d by the a l k a l i h y d r o x i d e c o n c e n t r a t i o n in s o l u t i o n and not by any p a r t i c u l a r
p r o p e r t y of the s o l i d phase; this is c o n s i s t e n t w i t h the e a r l i e r
s t a t e m e n t s about the s e c o n d peak. A c k n o w l e d g e m e n t
One of the a u t h o r s (G.A.C.M. Spierings) g r a t e f u l l y a c k n o w l e d g e s f i n a n c i a l s u p p o r t g r a n t e d by the "ENCI J u b i l e u m f o n d s " .
R e f e r e n c es
I. L.E. C o p e l a n d and D.L. K a n t r o in H.F.W. Taylor, The C h e m i s t r y of Cements, Vol. I, p. 315, 333. A c a d e m i c Press, L o n d o n and New Y o r k (I 956) .
2. W.J. M c C o y and O.L. E s h e n o u r , Proc. 5th. Int. Symp. Chem. C e m e n t , Tokyo, 1968, Vol. II, p. 347.
3. M. R e g o u r d and A. G u i n i e r , Proc. 6th. Int. Symp. Chem. C e m e n t , M o s c o w , 1974 ( P r i n c i p a l Paper) .
4. I. Maki, Cem. Concr. Res., 3, 295 (1973). 5. F.T. V ~ z q u e s , Ion, 31, 372 (1971).
6. H. Mori, G. Sudoh, K. M i n i g i s h i and T. Ohta, Rev. 25th. Gen. M e e t i n g , Cem. Asoc. Japan, 1972, p. 52.
7. K. M u r a k a m i , T. H i r o b u m i and Y. Nakura, Chem. and Ind., 1968,
p. 1 769.
8. V.R. R y a z i n , Yu.S. M a l i n i n and K.G. K o l e n o v a , T s e m e n t , 1972, p. 20.
272 Vol. 6, No. 2 G. A. C. M. S p i e r i n g s , H. N. Stein
9. T.A. K h r y z h a n o v s k a y a , V.M. M i r a k ' y a n , B.G. S h o k o t o v a and A.G. Kholodnyi, Tsement, 3__!I, 10 (1965).
10. E.E. Pressler, S. B r u n a u e r and D.L. Kantro, Anal. Chem. 288, 894 (1956).
11. W.A. Corstanje, H.N. S t e i n and J.M. Stevels, Cem. Concr. Res., 3, 791 (1973).
12. H.N. Stein, J. Appl. Chem. (London), 11, 474 (1961) .
13. J.G.M. de Jong, H.N. S t e i n and J.M. Stevels, J. Appl. Chem.
(London) , 1 8 9 (1968) o
14. J. Slanina, P. Vermeer, G. Mook, H.E.R. R e i n d e r s and J. A g t e r d e n b o s , Z. Anal. Chem., 260, 354 (1972).
15. C.C. Swasey, Tappi, 53, 1692 (1970).
16. A°S. Berger, N.P. K o t s u p a l o and V.A. P u s h n y a k o v a , Proc. 6th. Int. Symp. Chem. Cement, Moscow, 1974, S e c t i o n III,
s u p l e m e n t a r y p a p e r III-4.
17. F.E. Jones, J. Phys. Chem., 48, 379 (1944).
