Effect of silicone treatment on properties of bricks

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Effect of silicone treatment on properties of bricks

NATIONAL RESEARCH COUNCIL CANADA

DIVISION O F BUILDING RESEARCH

E F F E C T O F SILICONE TREATMENT ON P R O P E R T I E S O F BRICKS

by J . I . Davison I n t e r n a l R e p o r t No. 30 3 of t h e Division of Building R e s e a r c h Ottawa August 1964

PREFACE

The introduction of silicones f o r u s e in building h a s led t o many c l a i m s and many questions. T h e s e a r e usually difficult t o

r e s o l v e , mainly because they inevitably involve the science of water in building m a t e r i a l s and building constructions.

One such u s e , i n plant t r e a t m e n t of b r i c k s , h a s been explored through the appreciation of a number of simple t e s t s , the r e s u l t s of which a r e now r e p o r t e d and d i s c u s s e d .

The work was c a r r i e d out a t the Atlantic Regional Station of the Division. The author, a c h e m i s t , is a r e s e a r c h officer engaged in studies of m a s o n r y m a t e r i a l s and constructions in the Atlantic provinces.

Ottawa

August 1964

N. B. Hutcheon, A s s i s t a n t D i r e c t o r .

E F F E C T O F SILICONE TREATMENT ON PROPERTIES OF BRICKS by

J . I. Davison

Introduction of siliconed c l a y b r i c k s in the Atlantic a r e a in the s p r i n g of 1963 prompted s o m e i n q u i r i e s f r o m a r c h i t e c t s concerning the effect of the silicone t r e a t m e n t on the a b s o r p t i o n p r o p e r t i e s of b r i c k s . Specifically, t h e r e w e r e s e v e r a l i n q u i r i e s r e g a r d i n g the effect on the

5 - h r boiling absorption values-. Substantial reductions in initial r a t e of a b s o r p t i o n (I. R. A. ), s a t u r a t i o n coefficient, and tendency toward

e f f l o r e s c e n c e have been r e p o r t e d (1). Information on 24-hr s u b m e r s i o n and 5-hr boiling a b s o r p t i o n s i s lacking however. A study w a s t h e r e f o r e undertaken t o a c q u i r e s o m e information in t h i s a r e a and t o become m o r e f a m i l i a r with the effect of the silicone t r e a t m e n t g e n e r a l l y . The r e s u l t s a r e r e p o r t e d i n t h i s r e p o r t .

An initial attempt t o a s s e s s t h e effect of t h e silicone t r e a t m e n t consisted of a s e r i e s of a b s o r p t i o n t e s t s on two l o t s e a c h containing 100 extruded clay b r i c k s . The b r i c k s i n one lot had been siliconed a t the plant; t h o s e in the o t h e r lot w e r e not siliconed. It was considered that t h e p r o p e r t i e s of the u n t r e a t e d b r i c k s w e r e s i m i l a r t o t h o s e of the

siliconed b r i c k s before t r e a t m e n t , but t h e r e w a s no evidence t o s u b - s t a n t i a t e t h i s . A c o m p a r i s o n of the p r o p e r t i e s of the two l o t s w a s , t h e r e f o r e , m e a n i n g l e s s .

A second a p p r o a c h included d e t e r m i n a t i o n of a b s o r p t i o n

p r o p e r t i e s f o r 25 extruded (low suction) and 25 d r y - p r e s s (high suction) b r i c k s , s e l e c t e d in s u c h a m a n n e r a s t o be r e p r e s e n t a t i v e of the o v e r - a l l r a n g e i n p r o p e r t i e s f o r e a c h v a r i e t y . The b r i c k s w e r e then t a k e n t o the L a n t z plant of L. E . Shaw Ltd. where they r e c e i v e d a "silicone" t r e a t m e n t which consisted of spraying the b r i c k s on five s i d e s with a n aqueous solution r e p o r t e d t o contain 1/10 of 1 p e r cent sodium siliconate. The b r i c k s w e r e r e t u r n e d t o the l a b o r a t o r y and the p r o p e r t i e s again d e t e r m i n e d . A c o m p a r i s o n of r e s u l t s obtained b e f o r e and a f t e r t h e

silicone t r e a t m e n t i s given in T a b l e s I and

II.

It should b e noted t h a t the t r e a t m e n t f o r the extruded b r i c k a s d e s c r i b e d above was developed by the s u p p l i e r . The r e s u l t s obtained with the d r y - p r e s s b r i c k t h e r e f o r e a r e not n e c e s s a r i l y the optimum that might be achieved with a t r e a t m e n t designed specifically f o r it.

DISCUSSION

The information in T a b l e s I and

II

i n d i c a t e s t h a t i n i t i a l r a t e of a b s o r p t i o n w a s the only p r o p e r t y of e i t h e r b r i c k significantly affected

by siliconing. The a v e r a g e value f o r t h e e x t r u d e d b r i c k was reduced f r o m 1 6 . 4 t o 5 . 9 gm/30 s q i n . / m i n and f r o m 57.6 t o 23.0 gm/30 s q i n . / m i n f o r t h e d r y - p r e s s b r i c k . T h e I. R . A . of the u n t r e a t e d extruded b r i c k w a s i n the r a n g e of 1 2 . 1 t o 2 5 . 4 gm/30 s q i n . / m i n ; t h i s was r e d u c e d t o 3 . 1 t o 1 2 . 1 gm/30 s q i n . / m i n by t h e t r e a t m e n t . S i m i l a r l y the 31. 7 t o 9 2 . 7 gm/30 s q i n . / m i n r a n g e f o r t h e d r y - p r e s s b r i c k w a s reduced t o 3 . 8 t o 54. 7 gm/ 30 s q i n . / m i n . The p a t t e r n of reduction w a s not a s c o n s i s t e n t f o r t h e high-suction d r y - p r e s s b r i c k s a s f o r the extruded u n i t s . In view of the wide r a n g e of o r i g i n a l values f o r the d r y - p r e s s u n i t s , t h e g r e a t e r v a r i a t i o n i n final v a l u e s w a s not unexpected.

C o m p a r i s o n of t h e o t h e r a b s o r p t i o n p r o p e r t i e s of t h e u n i t s indicated no significant changes a f t e r siliconing

.

Any changes w e r e

s m a l l and within t h e m a r g i n of e r r o r . T h e r e w a s no reduction in s a t u r a t i o n coefficients f o r e i t h e r b r i c k .

E f f l o r e s c e n c e T e s t

One of t h e m a j o r r e a s o n s f o r siliconing the low-suction e x t r u d e d b r i c k s w a s t o c u r b i t s tendency toward e f f l o r e s c e n c e . In o r d e r t o check t h e effect on e f f l o r e s c e n c e , siliconed and c o n t r o l s p e c i m e n s (2 e a c h ) of both extruded and d r y - p r e s s b r i c k w e r e s e t on end t o a depth of 1 in. in a 10 p e r cent solution of sodium sulphate. After s e v e r a l d a y s t h e b r i c k s w e r e r e m o v e d f r o m the solution, allowed t o d r y , and t h e e f f l o r e s c e n c e w a s a s s e s s e d by v i s u a l o b s e r v a t i o n . S p e c i m e n s w e r e photographed and a r e shown in F i g u r e s 1 and 2.

T h e r e w a s no t r u e e f f l o r e s c e n c e with the extruded b r i c k . S a l t s , however, did c r y s t a l l i z e on t h e b r i c k a s w a t e r , which wicked up t h e

s i d e s , e v a p o r a t e d leaving the s a l t behind. The amount of the deposit a p p e a r s t o be p r o p o r t i o n a l t o t h e I. R. A. of the b r i c k . Thus the silicone t r e a t m e n t w a s helpful in lowering the suction of the b r i c k ( F i g u r e 1 ) .

T h e r e was heavy e f f l o r e s c e n c e Jn all f o u r d r y - p r e s s s p e c i m e n s . On the c o n t r o l s a m p l e s i t a p p e a r e d overnight but w a s s l o w e r in a p p e a r i n g on t h e siliconed b r i c k s . At the end of t h e t e s t , a c l e a r a r e a r e m a i n e d on one of t h e t r e a t e d b r i c k s , and t h e accumulation of s a l t s w a s not a s g r e a t a s on t h e c o n t r o l u n i t s ( F i g u r e 2).

F r e e z e - T h a w Cycling T e s t s

The d r y - p r e s s b r i c k s have c o n s i s t e n t l y failed (2) during r e l a t i v e l y e a r l y s t a g e s of l a b o r a t o r y f r e e z e - t h a w cycling t e s t s . T o check the

effect of siliconing on d u r a b i l i t y , four u n t r e a t e d and four t r e a t e d d r y - p r e s s b r i c k s w e r e subjected t o f r e e z e - t h a w cycling. The b r i c k s w e r e s e l e c t e d in s u c h a m a n n e r t h a t the o r i g i n a l s u c t i o n s of the t r e a t e d b r i c k s w e r e c o m p a r a b l e with t h o s e of t h e c o n t r o l s p e c i m e n s . T h i s m a y be

b r i c k s survived t o f a i l u r e . T h e r e i s no evidence of improved d u r a b i l i t y r e s u l t i n g f r o m the t r e a t m e n t . T h r e e of the c o n t r o l and two siliconed b r i c k s failed a f t e r 7 to 9 c y c l e s . The t h i r d siliconed s p e c i m e n , reduced in I. R. A. f r o m 92.7 to 1 3 . 4

gm/

30 s q in./min, survived 1 3 c y c l e s . The f o u r t h s p e c i m e n , reduced in I . R. A. f r o m 38.

6

t o 3.8 g m / 3 0 s q i n . / m i n , failed a f t e r 27 c y c l e s . Contradicting t h i s indication of i n c r e a s e d d u r a b i l i t y in the siliconed units i s the p e r f o r m a n c e of the r e m a i n i n g c o n t r o l b r i c k , I . R. A. 31. 5 g m / 3 0 s q i n . / m i n , which s u c c e s s f u l l y survived 50 c y c l e s .

T h e r e h a s n e v e r been any breakdown in t h e extruded b r i c k s during f r e e z e - t h a w cycling; it was, t h e r e f o r e , not considered n e c e s s a r y t o

include t h e m in t h i s phase of the study.

Leakage T e s t s on Individual B r i c k s

P r e v i o u s s t u d i e s which included leakage t e s t s on individual u n i t s r e v e a l e d w a t e r penetration of the d r y - p r e s s b r i c k in m e a s u r a b l e amounts ( 2 ) . Accordingly, the effect of the silicone t r e a t m e n t w a s checked by leakage t e s t s on two c o n t r o l and two siliconed b r i c k s . Leakage t o t a l s r e c o r d e d during the 24-hr t e s t period a r e shown in Table IV.

Again s a m p l e s w e r e s e l e c t e d s o t h a t the I. R. A. values of control units w e r e c o m p a r a b l e t o the o r i g i n a l s u c t i o n s of the siliconed b r i c k s . R e s u l t s do not indicate any i m p r o v e m e n t in r e s i s t a n c e t o w a t e r penetration a s a r e s u l t of the silicone t r e a t m e n t .

Extruded b r i c k s w e r e not subjected t o t h e t e s t s i n c e t h e r e h a s n e v e r been any evidence of leakage through t h e s e u n i t s .

S m a l l - P a n e l T e s t s

An extension of the study included leakage and b o n d - s t r e n g t h t e s t s on s m a l l p a n e l s in o r d e r t o a s s e s s the effect of the silicone t r e a t m e n t on the bond between b r i c k s and m o r t a r .

Eight panels w e r e a s s e m b l e d with the extruded b r i c k and f o u r with the d r y - p r e s s units. P e r t i n e n t information concerning panel a s s e m b l y i s contained in Table V and r e s u l t s of leakage and bond-strength t e s t s in Table VI.

R e s u l t s of leakage t e s t s indicate t h a t panels of siliconed u n i t s , both extruded and d r y - p r e s s , w e r e m o r e r e s i s t a n t t o penetration than p a n e l s of c o n t r o l u n i t s .

( a ) Extruded B r i c k s

P a n e l s A21 and A22, containing siliconed units and a ' m o r t a r

1

t i g h t e s t . T h e r e w a s no leakage n o r any indication of m o i s t u r e penetration, and t h e panels only a b s o r b e d 192 g m of w a t e r during t h e t e s t .

Bond-strength values w e r e slightly l o w e r f o r panels of siliconed units than f o r those containing untreated b r i c k s

- - but t h e extent of bond,

judged by v i s u a l observation, was slightly b e t t e r f o r panels of siliconed units.

(b) D r y - P r e s s B r i c k s

R e s u l t s a r e m o r e s t r i k i n g f o r the d r y - p r e s s b r i c k panels. Leakage t o t a l s w e r e reduced f r o m a n a v e r a g e of 2400 m l f o r panels of c o n t r o l

b r i c k s t o 790 m l f o r P a n e l A14 and 1166 m l f o r P a n e l A14D (both containing siliconed units). P a n e l A1 3 was broken p r i o r t o t e s t and its r e p l a c e m e n t A14D contained units having higher I. R. A. values than t h o s e in A14. T h u s the r e s u l t s a r e l i s t e d s e p a r a t e l y , instead of being a v e r a g e d , a s f o r o t h e r s e t s of panels.

Average bond-strength values f o r panels of t r e a t e d b r i c k s w e r e slightly higher t h a n t h o s e f o r panels of c o n t r o l b r i c k s .

R e s u l t s f r o m such a limited n u m b e r of panels a r e not sufficient t o justify rigid conclusions, but t h e i r g e n e r a l a g r e e m e n t with information in t h e l i t e r a t u r e i s c o n s i d e r e d sufficient c a u s e t o include t h e m i n t h i s r e p o r t . A silicone t r e a t m e n t c a n r e d u c e I. R.A. values s o t h a t they will be below the d e s i r a b l e l e v e l of 20 g ~ 3 0 s q in. / m i n and thus provide optimum conditions f o r m a x i m u m bond between units and m o r t a r . T h e r e i s , however, a danger that too much silicone m a y reduce suction t o such low l e v e l s that bond s t r e n g t h i s a d v e r s e l y affected.

CONCLUSIONS

(1) A silicone t r e a t m e n t , consisting of s p r a y i n g units with an. aqueous solution, r e p o r t e d t o contain 1/10 of 1 p e r c e n t sodium s i l i c o n a t e , applied t o extruded and d r y - p r e s s b r i c k s , r e s u l t e d in significant r e d u c t i o n s in i n i t i a l r a t e s of absorption f o r both t y p e s of b r i c k .

(2) T h e r e w a s no significant change in t h e o t h e r a b s o r p t i o n p r o p e r t i e s of t h e units a s a r e s u l t of t h e t r e a t m e n t .

(3) L a b o r a t o r y f r e e z e - t h a w cycling of c o n t r o l and siliconed d r y - p r e s s b r i c k s failed t o indicate any i m p r o v e m e n t in t h e d u r a b i l i t y of t r e a t e d u n i t s . (4) Only m i n o r r e s t r i c t i o n i n the tendency toward e f f l o r e s c e n c e w a s

indicated f r o m t e s t s i n which c o n t r o l and t r e a t e d u n i t s w e r e i m m e r s e d t o a depth of 1 in. in a sodium sulphate solution. The improvement was a t t r i b u t e d t o reduced suction of the t r e a t e d b r i c k s .

(5) Limited t e s t s on s m a l l panels containing t r e a t e d and control units and m a s o n r y m o r t a r mix, indicated i n c r e a s e d r e s i s t a n c e to water

penetration in panels of siliconed b r i c k s

-

-

both extruded and d r y - p r e s s . Bond

-

strength values w e r e slightly lower for panels of siliconed extruded b r i c k s than f o r panels of control b r i c k s . Higher values, however, were obtained f o r silicone d d r y - p r e s s b r i c k panels than in the corresponding duplicate control-brick panels. Extent of bond, a n important p r o p e r t y in determining r e s i s t a n c e t o r a i n penetration, was considered s u p e r i o r in panels of siliconed b r i c k s of both types.

REFERENCES

(1) Carlson, B. C.

,

and William D. Betts. How plant applied silicones affect wall s t r e n g t h s . B r i c k and Clay Record, Vol. 135, No. 1, 1959, p.49-51, 68.

(2) Davis.on, J. I. Effect of silicone t r e a t m e n t on s m a l l panels a s s e m b l e d with high suction d r y - p r e s s b r i c k s . National Re s e a r c h Council, Division of Building R e s e a r c h , Internal Report No. 241, F e b r u a r y 1962.

TABLE I

COMPARISON O F PROPERTIES O F B U F F EXTRUDED

S T I F F -MUD BRICK BEFORG AND A F T E R SILICONE TREATMENT

UNTREATED

I

SILIC ONED

I. R. A.

,

Absorption,

gm/30

% D r y w e i g h t D r y

No. s q in./ 24-hr 5 - h r Sat. P o r . , Density, min Subm. Boil Coeff.

70

g d c c

I. R. A . , Absorption,

70

D r y Weight D r y

s q i n . / 24-hr 5-hr Sat. P o r .

,

Density, min Subm. Boil Coeff.

70

g m / c c

TABLE

II

COMPARISON O F P R O P E R T I E S O F RED

DRY - P R E S S BRICK B E F O R E AND A F T E R SILICONE TREATMENT

UNTREATED

1

SILIC ONED

I. R . A.

,

A b s o r p t i o n ,

70

D r y Weight D r y No. s q i n . / 2 4 - h r 5 - h r S a t . P o r .

,

Density, I. R. A. A b s o r p t i o n ,

gm/3oP

70

D r y Weight D r y s q i n . / 24-hr 5 - h r Sat. P o r

.

,

Density, min Subm. Boil Coeff.

70

g m / c c

I

A n Subm. Boil Coeff.

70

g m / c c

1 3 1 . 7 2 3 2 . 4 3 3 8 . 4 4 3 8 . 6 5 4 0 . 7 6 4 1 . 2 7 4 4 . 8 8 4 7 . 4 9 4 8 . 4 10 5 2 . 5 11 5 4 . 6 12 5 4 . 6 1 3 5 7 . 2 14 5 9 . 4 15 6 1 . 0 1 6 6 2 . 6 17 6 2 . 8 18 65.0 19 6 5 . 9 20 7 0 . 6 21 7 2 . 6 22 8 1 . 9 23 8 4 . 8 24 8 8 . 5 25 9 2 . 7 Ave. 5 7 . 6

TABLE Ill

RESULTS O F FREEZE-THAW CYCLING UNTREATED AND SILICONED BRICKS

TABLE IV

RESULTS O F LEAKAGE TESTS ON DRY-PRESS BRICKS UNTREATED I. R.A. B r i c k

gm/30

F r e e z e - T h a w No. s q i n . / C y c l e s t o m i n F a i l u r e .. 1 31. 5 5 0 No F a i l u r e 2 60.1 7 3 76.4 8 5 95.8 9 T Y P E Leakage REMARKS s q i n . / m i n m l U n t r e a t e d 5 5 . 1 103 Leakage o c c u r r e d in 1/2 h r W a t e r pickup 154.8 g m Untreated 69. 5 286 Leakage o c c u r r e d i n 1/2 h r Water pickup 1 6 4 . 3 g m :K Siliconed 5 2 . 5 +B 20.6 120 L e a k a g e o c c u r r e d i n 1/2 h r Water pickup 1 4 5 . 6 g m :;c Siliconed 7 0 . 6

-+

4 0 . 7 296 Leakage o c c u r r e d in 1/2 h r W a t e r pickup 161. 3 g m S I L K ONED I. R. A. I. R. A. B r i c k B e f o r e , After, F r e e z e - T h a w No. gm/30 gm/30 C y c l e s t o s q in.

/

s q in.

/

F a i l u r e m i n m i n 4 38.6 3.8 27 1 4 5 9 . 4 23. 3 8 23 84.8 54. 3 8 25 9 2 . 7 1 3 . 4 1 3 :; < I. R. A. r e d u c e d f r o m 5 2 . 5

+

2 0 . 6 g m by silicone t r e a t m e n t and f r o m 7 0 . 6 - 40.7 I t II 11

W

-

O f;;

Z T E

M O M

9"

W O

G

-

W V ) o *

Z

E

.Y

Es

3

2s

h k rd Q, d $'

2

1

\

d

E

M rn

5

--

Q

g,

_b E_c

T A B L E

VI

RESULTS O F LEAKAGE AND BOND STRENGTH TESTS ON SMALL PANELS LEAKAGE RESULTS

P a n e l T o t a l W a t e r

N u m b e r L e a k a g e , A b s o r b e d R e m a r k s ml by P a n e l ,

e m

BOND STRENGTH RESULTS A v e r a g e Value R e m a r k s p s i A5, A6 4 , 0 9 9 1 , 1 7 8 L e a k a g e o c c u r r e d 20

-

30 2. 3 m i n a f t e r s t a r t of t e s t and continued s t e a d y t o end.

A l l , A12 6 1 , 0 8 0 Slight leakage f o r A1 1. 1 2 . 8 None f o r A12.

A15, A16 Nil 7 17 Much t i g h t e r p a n e l s

-

slight 4 . 8 l e a k a g e f o r A1 5 not m e a s u r a b l e .

A21, A22 Nil 192 No indication of m o i s t u r e 8 . 0 penetration. A7, A8 2 , 4 0 0 7 36 L e a k a g e o c c u r r e d 15 m i n 20. 3 a f t e r s t a r t of t e s t

- -

t h r o u g h u n i t s and joints. 790 692 L e a k a g e o c c u r r e d 30 min 20.7 a f t e r s t a r t of t e s t - - t h r o u g h u n i t s and joints. A14D 1 , 1 6 6 765 L e a k a g e r e c o r d e d 36 m i n 23. 3 a f t e r s t a r t of t e s t

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t h r o u g h u n i t s and joints

.

Only f o u r v a l u e s obtained f o r eight joints. P o o r extent of bond.

A v e r a g e of 6 v a l u e s

-

-

two low v a l u e s in A1 1 . Good extent of bond in s o m e joints. A v e r a g e includes 8 v a l u e s

.

Not good extent.

E x t e n t of bond fair f o r all 8 joints.

Only 1 value A8. Good extent of bond f o r A7 and 1 joint A8.

Good extent of bond f o r 3 joints.

Good extent of bond i n all 4 joints.

FIGURE 1

Efflorescence on buff extruded b r i c k s after i m m e r s i o n to

a

depth of

1 in. in a 1 8 per cent ssBution s f N a SO Bricks on ieft silicone 4'

t r e a t e d , bricks on right untreated. %lgures in second r o w on bricks

FIGURE 2

E f f l o r e s c e n c e on r e d d r y - p r e s s b r i c k s after immersis~a t o a d e p t h of

1 in. in a _{1 0 p e r cent solution of N a $8 B r i c k s on left untreated}

-

b r i c k s on _{r i g h t s i l i c s n e d .} 2 4 "