salt combinations

CEMENT and CONCRETE RESEARCH. Vol. 14, pp. 297-299, 1984. Printed in the USA. 0008-8846/84 $3.00+00. Copyright (c) 1984 Pergamon Press, Ltd.

NOTE AIR ENTRAINMENT IN MORTARS AND CONCRETE: THE EFFECT OF SUPERPLASTICIZER/SALT COMBINATIONS

Michael Grutzeck Materials Research Laboratory The P e n n s y l v a n i a S t a t e U n i v e r s i t y U n i v e r s i t y P a r k , PA 16802

(Communicated by J. Skalny) (Received Aug. 2, 1983)

Introduction It has recently come to our attention that the use of salt-saturated solutions in mixing superplasticized m o r t a r s and c o n c r e t e s w i l l s o m e t i m e s l e a d to the entrainment of large quantities o f a i r ( i n e x c e s s o f 20~, o f t e n as h i g h a s 50~). T h i s e f f e c t was u n e x p e c t e d and s u g g e s t s a p o t e n t i a l Incompatibility b e t w e e n s a l t and s u p e r p l a s t i c i z e r . I n an a t t e m p t t o q u a n t i f y t h e p o t e n t i a l of various superplasticizezs t o e n t r a i n a i r when u s e d i n s a l t - c o n t a i n i n g mortars and c o n c r e t e , the f o l l o w i n g t e s t was d e v e l o p e d . The c o n c e p t i s n o t e n t i r e l y new (Dodson, 1 9 8 1 ) , b u t p e r h a p s s o m e w h a t m o r e q u a n t i t a t i v e . Experimental One h u n d r e d g r a m s o f w a t e r a r e added t o a c o n v e n t i o n a l l a b o r a t o r y W a r i n g blender. Superplasticizer ( e i t h e r d r y o r l i q u i d ) i s t h e n added t o t h e w a t e r and olended at setting #4 f o r o n e m i n u t e . Th e l e v e l o f f o a m g e n e r a t e d is observed, relative to the original level of the solution. Observations are made Immediately after mixing and again after one minute (to observe team stability). Usually very little i f any f o a m i n g o c c u r s a t t h i s p o i n t . Next, 35g o f s a l t (NaC1) a r e a d d e d t o t h e o r i g i n a l solution and o n c e a g a i n t h e mixture i s b l e n d e d a t #4 a n d t h e l e v e l o f f o a m i s m e a s u r e d . After these observations the solution is discarded and the process repeated for othez combinations of ingredients. In the present study, the brine compatibility of supezplasticizers were evaluated. The t w o m o s t common s u p e r p l a s t i c i z e r s , a sulphonated naphthalene fozmaldehyde condensate and a sulphonated melamine formaldehyde condensate were studied. In each case three tests were carried out. In the first, the system contained only superplasticizer, w a t e r and s a l t . Foam p r o d u c t i o n as a function of supezplasticizez concentration was m e a s u r e d . I n t h e s e c o n d and third cases, the control o f f o a m i n g was s t u d i e d after adding either a p h o s p h a t e - b a s e d (TBP o r DBP) o r s i l i c o n e - b a s e d defoaming agent to the original solution.

297

298

Vol.

14, No. 2

M. Grutzeck

Results Results of testing a solid form of a sulfonated naphthalene formaldehyde condensate (SNFC) m i x e d w i t h a s a t u r a t e d brine solution, w i t h and w i t h o u t detoamlng agents, are given in Figure I. View (A) d e p i c t s f o a m i n g f o r v a r i o u s a m o u n t s o f SNFC m i x e d w i t h 1 0 0 g H20 a n d 3 5 g o f N a C I . V i e w s (B) a n d (C) g i v e the effect of the addition of either 0.58 of a phosphate or 1.0g of a I0~ active silicone fluid to the original solution, respectively. The l e v e l o f foam d e v e l o p m e n t was u n e x p e c t e d , b u t d i d e x p l a i n why o u r m o r t a r s and c o n c r e t e s w e r e e n t r a i n i n g a i r on p r o l o n g e d m i x i n g .

I

I

I

I

I

I

I -

I

H

I

I

I

I

I

I

I

I

I

I

RIGHT AFTER MIXlN

( ~ . - - O AFTER I MINUTE

0 _J w > Ld /

4 / 2 _

/

0/

-

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~D----e

-

I 0

I 2

% 1.

I

E 4

SNFC

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I 6

-

(B)

(A) 0

Figure

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• /

I 0

I 2

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I 4

% SNFC

I

(c)_

I 6

0

2

4

6

% SNFC

Sulp~onated naphthalene f o r m a l d e h y d e c o n d e n s a t e ' s (SNFC) t e n d e n c y towards foam production when mixed with brine and v a r i o u s defoamers. V i e w (A) 1 0 0 g H20 + 3 5 g NaC1. V i e w (B) 1 0 0 g H20 + 35g NaCI + 0 . S g p h o s p h a t e defoamer. V i e w (C) 1 0 0 g H20 + 35g NaC1 + 1 . 0 g 10S s i l i c o n e d e f o a m e z .

R e p e a t i n g t h e same t e s t , b u t s u b s t i t u t i n g a 20S a c t i v e l i q u i d s u l p h o n a t e d m e l a m i n e f o r m a d e h y d e c o n d e n s a t e (SMFC) f o r t h e above s u p e r p l a s t i e i z e r gave the results s h o w n i n F i g u r e 2. A g a i n , v i e w (A) d e p i c t s the level of Ioaming o b t a i n e d w i t h SMFC m i x e d w i t h w a t e r and s a l t . 0nly relatively little roaming was observed. V i e w s (B) a n d (C) i n d i c a t e effective control o f f o a m i n g by either type of defoamer. Conclusions A p p a r e n t l y some t y p e o f c h e m i c a l i n t e r a c t i o n is taking place between the sulfonate formaldehyde napthalene condensate and t h e s a l t w h i c h p r o d u c e s a large amount of relatively stable foam. Defoamers are only partially effective in controlling t h e foam. In the case of the sulphonated melamine formaldehyde condensate, foaming is of little consequence a n d c a n be effectively controlled with a defoamer. The d e s c r i b e d t e s t i s a s i m p l e one w h i c h a l l o w s one t o q u i c k l y d e t e r m i n e the potential for foaming. I t a l l o w s one t o s i f t t h r o u g h a c o m p l e x m a t r i x o f potential combinations, reducing the number of tull mortar or concrete mixtures needed for evaluation of suitability of potential mixtures.

14, No. 2

Vol.

299

A I R ENTRAINMENT,

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SUPERPLASTICIZERS,

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SALT,

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NAPHTHALENE,

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2"0 %

Figure

2.

30

40

50 0

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TEST

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RIGHT AFTER MIXING_

(A}

0

MELAMINE,

(B}

(C)

A

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1

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I~O

2"0

3"0

4--0

50 0

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4"0

5--0

SMFC

% SMFC

% SMFC

Sulphonated melamine formaldehyde condensate's (SMFC) t e n d e n c y towards foam production when mixed wxth brine and various defoamers. V i e w (A) 1 0 0 g H20 + 35g NaC1. V i e w (B) 1 0 0 g H20 + 35g NaC1 + 0 . $ g p h o s p h a t e defoamer. V i e w (C) 1 0 0 8 H20 + 35S NaC1 + 1.0g 10~ s i l i c o n e d e f o a m e r .

In the present situation we w a n t e d to reduce air entrainment, but conversely, should one want to increase air entrainment, o n e m i g h t do s o b y a d d i n g ~ome s a l t t o t h e s u l f o n a t e d n a p h t h a l e n e c o n d e n s a t e m i x t u r e s . Acknowledgements We a r e g r a t e f u l t o DOE f o r t h e i r like to thank Darlene Wolfe-Confer for tests.

support her help

o f t h i s s t u d y . We w o u l d a l s o in carrying out the described

References

1.

V. Dodson, (1981).

personal

communication.

W.R. G r a c e

and Company,

Cambridge,

MA