Studies on expansive cement 1-volume changes

CEMENTand CONCRETERESEARCH. Vol. 6, pp. 707-710, 1976. Pergamon Press, Inc Printed in the United States.

STUDIES

ON E X P A N S I V E

I- V O L U M E H.

E6-Didamony,

N.

CEMENT

CHANGES

Mostafa

and M o Z o

Mostafa

Chemistry Department,Faculty of S c i e n c e , Z a g a z i g U n i v e r s i t y and Refractories and Building Materials Department, National Research Centre, Bokki, Cairo, Egypt.

(Communicated by H. F. W. Taylor) (Received May 25, 1976)

ABSTRACT K a o l i n w a s u s e d as an a l u m i n o u s r a w m a t e r i a l i n s t e a d of b a u x i t e f o r the m a n u f a c t u r e of e x p a n s i v e c e m e n t clinker. The linear expansions and compressive s t r e n g t h s of the d i f f e r e n t e x p a n s i v e c e m e n t p a s t e s were investigated. T h e e x p a n s i b i l i t y of the p a s t e w a s h i g h e s t at a m o l a r r a t i o G a S 0 L , : CaO : C4A3~ of 8 : 6 : I.

In e i n e r L a b o r u n t e r s u c h u n g wird Kaolin aber kein B a u x i t als R o h s t o f f e d e r A 6 p 0 3 f ~ r d i e Q u e l l z e m e n t h e r stellun~ verwendet. Die L~ngen~nderungen sowie die Druckfestigkeiten der verschiedenen Mischungen werden bestimmt. Es w i r d f e s t g e s t e l l t , d a s s das Molverhaltnis yon CaSO 4 : Ca0 : C4A3~ = 8:6 : I die besten Quelleigenschaften und Festigkeiten besitzt.

707

708

Vol. 6, No. 5 H. EI-Didamony, N. Mostafa, M. Z. Mostafa Introduction

Concrete made from normal portland cement suffers from shrinkage, which can cause major problems. S h r i n k a g e c a n be e l i m i n a t e d , or at l e a s t r e d u c e d , b y u s i n g an e x p a n s i v e c e m e n t , and for s o m e a p p l i c a t i o n s it m a y be d e s i r a b l e to d e v e l o p a p o s i t i v e e x p a n s i o n , as for i n s t a n c e to i n d u c e t e n s i l e s t r e s s e s in the r e i n f o r c i n g steel. The most successful expansive c e m e n t s h a v e b e e n o n e s in w h i c h e x p a n s i o n is c a u s e d b y the f o r m a t i o n of e t t r i n g i t e , C ~ A . 3 C ~ . 3 2 H 2 0 . One w a y of p r o d u c i n g this p h a s e is b y u s i n g a m l x t u r e of P o r t l a n d c e m e n t w i t h an e x p a n s i v e c l i n k e r c o n t a i n i n g the c o m p o u n d C 4 A 3 S . F o r the f o r m a t i o n of e t t r i n g i t e , it is n e c e s s a r y that the e x p a n s i v e c l i n k e r s h o u l d a l s o c o n t a i n free C a S 0 4 and Ca0. Expansive c l i n k e r s c o n t a i n i n g t h e s e two c o m p o n e n t s h a v e u s u a l l y b e e n m a d e u s i n g b a u x i t e as a r a w m a t e r i a l , b u t N a k a m u r a et al. (I) and E6-Didamony and H e n n i n g (2) h a v e e x a m i n e d the p o s s i b i l i t y of r e p l a c i n g this w i t h k a o l i n . In the p r e s e n t p a p e r , we i n v e s t i g a t e the p o s s i b i l i t y of m a k i n g an e x p a n s i v e c l i n k e r u s i n g g y p s u m , l i m e s t o n e and k a o l i n f r o m E g y p t i a n s o u r c e s , and the s t r e n g t h and e x p a n s i v e c h a r a c t e r i s t i c s of the e x p a n s i v e c e m e n t s prepared using varying proportions of e x p a n s i v e c l i n k e r and portland cement.

Experimental The m a t e r i a l s u s e d w e r e p o r t l a n d c e m e n t , k a o l i n (fro m Kalabsha, Aswan, Egypt), limestone (from Sammalout, Minia, E g y p t ) and g y p s u m (from A l e x a n d r i a , Egypt). Table 1 gives a n a l y s e s of the k a o l i n , g y p s u m and c e m e n t ; the l i m e s t o n e c o n t a i n e d o v e r 9 8 % C a C O 3. The calculated phase composition of the g y p s u m w a s C a S O 4 . 2 H 2 0 , 88%; C a C O 3, 9%; other phases ( i n c l u d i n g SiO 2 and N a C g ) , 3%. T h e w e i g h t s of k a o l i n , l i m e s t o n e and g y p s u m n e e d e d to m a k e an e x p a n s i v e c l i n k e r of g i v e n p h a s e c o m p o s i t i o n , r e f e r r e d to the i g n i t e d w e i g h t , w e r e c a l c u l a t e d by N a k a m u r a ' s e q u a t i o n s (I). 100 1 . 7 8 ( ( 0 . 5 5 + 0 . 1 8 3 n ) P + 1 . 1 7 F + 1.875) 1.13 ( 0 . 4 4 5 ( I + m ) P + I. 13S ) , w h e r e 5% Ag203 - 0.426 %Fe203) in k a o l i n ; Fe203 in k a o l i n ; % Si02 in k a o l i n ; desired molar ratio OaS04/C4A3S in c l i n k e r , desired molar ratio CaO /C4A3S in c l i n k e r .

Kaolin Limestone Gypsum P F S

= = = = = =

m

=

n

=

Four each case porcelain then mixed and b u r n e d g r o u n d to

c l i n k e r s w e r e m a d e w i t h d i f f e r e n t r a t i o s m : n. In the t h r e e c o n s t i t u e n t s w e r e g r o u n d s e p a r a t e l y in a b a l l m i l l to p a s s c o m p l e t e l y t h r o u g h a 2 0 0 - m e s h sieve, in a s l u r r y w i t h w a t e r in the b a l l m i l l for one h o u r , as p e l l e t s for one h o u r at 1150°C. The p r o d u c t w a s b e l o w 63 wm. Table 2 gives analyses.

and

P a s t e s w e r e m a d e u s i n g m i x t u r e s of one or o t h e r of t h e s e e x p a n s i v e c l i n k e r s w i t h the p o r t l a n d c e m e n t in v a r i o u s p r o p o r t ions, at a w a t e r / t o t a l c e m e n t r a t i o of 0.25. The expansive c e m e n t c l i n k e r and p o r t l a n d c e m e n t w e r e m i x e d t o g e t h e r for one

Vol. 6, No. 5

709

EXPANSIVE CEMENT, VOLUMECHANGES, RAW MATERIALS TABLE

I

Chemical Analyses of Kaolin, Gypsum and Portland Cement

Kaolin Gypsum Portland

Cement

SiO 2

A6203

Fe203

46.02

39.44

0.45

0.38

--

5.40

3.45

64.03

-21.06

CaO

MgO

0.30

0.26

34.06

0.03

41.03

3.31

0.80

2.40

--

TABLE

S03

C02

. . . .

I.L.

Total

13.50

99.97

21.32

100.17

2.42

99.55

2

Chemical Analyses of the Clinkers SiO 2

A6203

Fe203

Ca0

SO 3

Total

m

n

m/n

I 2

10.74 9.70

9.00 7.75

0.70 0.65

48.30 52.00

31.72 30.10

100.46 100.20

8 8

6 8

1.33 1.00

3

9.40

7.60

0.60

51.80

31.25

100.65

9

7

1.29

4

9.15

7.30

0.50

52.92

30.02

99.89

10

8

1.25

h o u r in a p o r c e l a i n b a l l m i l l u s i n g one b a l l . Mixing was d o n e u s i n g o r d i n a r y g a u g i n g t r o w e l s on a s t e e l p l a t e c o n t i n uously and vigorously for 4 minutes. The pastes were moulded i n t o I x I × 6 cm p r i s m s f o r e x p a n s i o n t e s t s and i n t o one i n c h ( 2 . 5 4 cm) c u b e s f o r the c o m p r e s s i v e s t r e n g t h t e s t s . I m m e d i a t e l y a f t e r m o u l d i n g , the s p e c i m e n s f o r e x p a n s i o n t e s t s w e r e c u r e d in a moist c a b i n e t f o r 6 h o u r s ; they were then r e m o v e d f r o m t h e i r m o u l d s a n d c u r e d c o n t i n u o u s l y at r o o m temperature (23 ~ I°C) in w a t e r f o r 28 days. Length measurem e n t s w e r e m a d e a f t e r 6 h o u r s and 3, 7, 14, a n d 28 d a y s , u s i n g a p r o c e d u r e s i m i l a r to t h a t d e s i g a t e d C 1 5 1 - 6 0 in the A S T M s t a n d a r d s f o r c e m e n t , l i n e a r e x p a n s i o n s in m m / m b e i n g c a l c u l a t e d f r o m a v e r a g e l e n g t h c h a n g e s b a s e d on the i n i t i a l measurements at 6 h o u r s . Results

and

Discussion

Fig. I s h o w s the v a r i a t i o n w i t h c u r i n g t i m e a n d p r o p o r t i o n of e x p a n s i v e c l i n k e r in c o m p r e s s i v e s t r e n g t h a n d l i n e a r e x p a n s i o n f o r p a s t e s m a d e u s i n g e a c h of the f o u r d i f f e r e n t expansive clinkers. I n Fig. r e p l o t t e d to clinkers.

2 the allow

results for 20% expansive clinker a direct comparison between these

are four

I n all c a s e s the e x p a n s i o n i n c r e a s e s w i t h the a m o u n t of expansive clinker. The highest expansions were obtained with e x p a n s i v e c l i n k e r 1, w h i c h a l s o g a v e r e a s o n a b l e c o m p r e s s i v e strengths. In t h i s c l i n k e r , the m o l a r r a t i o s C a S O 4 : C a O : C 4 A 3 S are 8 : 6 : 1 ; t h i s c o r r e s p o n d s to the c o m p o s i t i o n of e t t r i n g i t e ,

710

Vol. 6, No. 5 H. EI-Didamony, N. Mostafa, M. Z. Mostafa

w h e r e a s m i x t u r e s c o n t a i n i n g l o w e r p r o p o r t i o n s of s u l p h a t e m i g h t be e x p e c t e d to y i e l d m o n o s u l p h a t e : H20 3 (C3A. 3CS. 32H20) C4A3S + 8CaSO 4 + 6CaO

ion

H20 04A3S

> 3 ( C 3 A . C S . 12H20)

+ 2CaSO 4 + 6CaO

r ,

I

uJ

S 10

15

j_gJ- J

20

Tame(days) EC% Expansive Chnker 2

Dine (days)

EC% Expansive Clinker 1

13 7 Dine (days)

%

28

10

Dme (days)

f C Z

15 20 EC %

Expansive Chnker 4

Expansive Clinker3

FIG. 1 Linear expansions (E,mm/m) and compressive strengths (R,ibxinxll0-3) for pastes made with four different expansive clinkers, plotted against curing time and the percentage of expansive clinker in the cement (E.C.). In plots against time, percentages of expansive clinker are shown thus: o 0%, o 10%, • 15%, and A 20%. In plots against percentage of expansive clinker, curing times are shown thus: o 1 day, • 3 days, A 7 days, ; 14days, and i 28 days. 14

12

#0

R8 6 4 2 I

I

I

I

20

E

FIG. 2 Linear expansion (E,mm/m) and compressive strengths (R, ib/in2xl0 -3) for pastes made with 20% of four different expansive clinkers.

~6

o Clinker 1

• Clinker 2

~2

A Clinker 3

i Clinker 4

~0 8

m Portland cement

6 &

2 3

1 .

2.

7

~ rime ( d ~ s }

N. Nal~amura,

G.

References S u d o h and S . A k a i w a ,

Cement, Tokyo,

1968, ~,

H.

and O. H e n n i n g ,

Eg-Didamony

5th

Int.

Symp.

Chem.

351 ( 1 9 6 9 ) . S i l i k a t t e c h ~ 2__44 279

(1973).