Effects of freezing brick masonry at an early age

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Effects of freezing brick masonry at an early age

N A T I O N A L R72SEARCH C O U N C I L CANADA

D I V I S I O N OF

BUILDING

HXSEARCH

EFFXCTS OF

FREEZING

B R I C K MASONRY AT AN EARLY AGI;: by T. R i t c h i e and P. T. Hodgins I n t e r n a l Report No. 213 of t h e D i v i s i o n of B u i l d i n g Research Ottawa March 1961

The promotion of w i n t e r c o n s t r u c t i o n i n Canada a s a n a i d i n r e d u c i n g w i n t e r unemployment i n t h e c o n s t r u c t i o n i n d u s t r y h a s l e d t o a need f o r a r e a s s e s s m e n t of t h e c o l d ?weather p r o t e c t i o n r e q u i r e d d u r i n g t h e l a y i 3 g of masonry. The I l i v i s i o n , r e c o g n i z i n g t h i s n e e d , h a s c o n s t r u c t e d a c o l d room and h a s i n i t i a t e d a prosram of s t u d y of t h e e f f e c - t s of f r e e z i n g , u n d e r v a r i o u s c o n d i t i o n s , upon newly l a i d b r i c k

Inn 5 onry.

.F. T. Hodgins, t h e second a u t h o r , and a r e s e a r c h o f f i c e r w i t h t h e B u i l d i n g M a t e r i a l s S e c t i o n , was i n c h a r g e of t h e f i r s t phase of t h e s t u d y . T h i s r e p o r t of t h e work which was c a r r i e d o u t by M r . Hodgins b e f o r e he l e f t t h e D i v i s i o n t o t a k e u p o t h e r d u t i e s , h a s been p r e p a r e d by 1:vl.r. R i t c h i e , a ceramic e n g i n e e r and a r e s e a r c h o f f i c e r w i t h t h e D t v i s i o n . rho

h a s been engaged f o r many y e a r s i n s t u d i e s of b r i c k masonry. The r e s u l t s r e p o r t e d a r e p r e l i m i n a r y o n l y , s i n c e it; has n o t y e t been p o s s i b l e t o resu1.w work on t h e p r o j e c t .

Ottawa B.

Il.

Hutcheon

By T . _{R i t c h i e and P. T. Hodgins}

B u i l d i n g c o n s t r u c t i o n i n Canada i s c a r r i e d o u t y e a r - round, a l t h o u g h t h e r e i s u s u a l l y a s l a c k e n i n g of a c t i v i t y i n t h e w i n t z r s e a s o n . l)u.rin,q; p e r i o d s of s e v e r e cold., some t y p e s of work mag be c o m p l e t e l y stopped u n l e s s p r o t e c t i o n i s provided f o r t h e work o r t h e workers o r b o t h . I n many c i t i e s ( f o r example, Ot-taws ) b r i c k l a y i n g h a s been c a r r i e d o u t i n a i r t e m p e r a t u r e s

w e l l below f r e e z i n g w i t h o u t p r o - t e c t i o n t o t h e work. The l i m i t i n g c o n s i d e r a t i o n i n many c a s e s a p p e a r s t o be t h e c a p a c i t y of t h e b r i c k l a y e r s t o work i n s e v e r e l y c o l d c o n d i t i o n s , r a t h e r t h a n p o s s i b l e impairment of t h e q u a l i t y of -the work.

To p r e v e n t r e d u c t i o n i n t h e q u a l - i t y of masonry due t o f r e e z i n g a t a n e a r l y a g e , many s p e c i f i c a t i o n s and codes of p r a c t i c e f o r b r i c k masonry c o n s t r u c t i o n r e q u i r e t h a t t h e

t e m p e r a t u r e of t h e masonry be maintained above f r e e z i n g f o r some time ( u s u a l l y a t l e a s t 4 8 h o u r s ) a f t e r t h e briclo?rorlr i s

c o n s t n ~ c t e d t o permit it t o a c h i e v e r e s i s t a n c e t o damage b e f o r e b e i n g f r o z e n . hlan;~ c o n t r i ~ c t o r s however, have n o t e d t h a t briclc masonry which had been c o n s t r u c t e d w i t h o u t p r o t e c t i o n i n v e r y cold weather a p p a r e n t l y h a s performed s a t i s f a c t o r i l y . The need f o r t h e r e q u i r e m e n t s s e t o u t i n s p e c i f i c a t i o n s r e g a r d i n g

p r o t e c t i o n t o t h e masonry d u r i n g c o n s t r u c t i o n i n f r e e z i n g weather h a s t h e r e f o r e been q u e s t i o n e d , and it seems i m p o r t a n t t o d e t e r m i n e how t h e p r o p e r t i e s of b r i c k masonry construe-Led imcier f r e e z i n g c o n d i t i o n s d i f f e r from t h o s e of s i m i l a r masonry c o n s t r u c t e d under normal ( i . e . summer) c o n d i t i o n s .

P r e l i m i n a r y l a b o r a t o r y s t u d i e s of t h i s problem were u n d e r t a k e n i n t h e D i v i s i o n of B u i l d i n g Research i n 1958. I t

was t h e n planned t o s t u d y s m a l l p a n e l s of b r i c k masonry t o d e t e r m i n e t h e e f f e c t on v a r i o u s p r o p e r t i e s of f r e e z i n g a t a n e a r l y age. The p r o p e r t i e s t o be s t u d i e d ?vere r e s i s t a n c e t o m o i s t u r e p e n e t r a t i c n , s t r e n g t h of bond between b r i c k and m o r t a r , and d i m e n s i o n a l changes i n t h e b r i c k ~ o r k . I t was o r i g i n a l l y planned t h a t p a n e l s made of s e v e r a l t y p e s of b r i c k s and s e v e r a l m o r t a r compositions would be s t u d i e d . The b r i c k s were t o be chosen t o c o v e r a wide range of i n i t i a l r a t e of a b s o r p t i o n , o r " s u c t i o n 1 ' , which i s a n i m p o r t a n t p r o p e r t y w i t h r e s p e c t t o t h e bonding between b r i c k and m o r t a r . The f i r s t p a r t of t h e s t u d y i n v o l v e d t h e c o n s t r u c t i o n of p a n e l s u s i n g a l o w - s u c t i o n b r i c k and a v a r i e t y of m o r t a r s . ':hen t h i s p a r t of t h e lnrork was

completed, however, t h e r e s e a r c h o f f i c e r s u p e r v i s i n g t h e s t u d y l e f t t h e D i v i s i o n f o r o t h e r d u t i e s , w i t h t h e r e s u l t t h a t t h e program o r i g i n a l l y planned h a s n o t y e t been completed. The r e s u l t s p r e s e n t e d i n t h i s r e p o r t t h e r e f o r e r e f e r o n l y t o t h e p a r t i c u l a r l o w - s u c t i o n b r i c k u s e d , and it i s c o n s i d e r e d l i k e l y t h a t d i f f e r e n t r e s u l t s w i l l be o b t a i n e d when o t h e r t y p e s of b r i c k s a r e employed.

The p i ~ n e l s c o n s i s t e d of f i v e b r i c k s l a i d one nbovc t h e o t h c r r v i t 3 1 m o r t a r j o i n t s between, asssmbl-ed and t e s t e d f o r m o i s t u r e p e r l c t r a t i o n and bond s t r e n g t h p r o p e r t i e s a s

d c s c r t b e c i i n 1)BR I n t e r n a l R e p o r t s Nos. 1 6 0 and 115 ( 1 , 2 ) . The t i m e i n t e r v : ~ l b e t w e e n pl3c;ine t h e m o r t a r on t h e s u r f a c e of t h e b r i c k and t h e n p l a c i n g t h e n e x t b r i c k on it was s e t a t 30 s e c o n d s , and a t a p p i n g i m p a c t o f 4 pounds d r o p p i n g t h r o u z h

14

i n c h e s was u s e d t o bed t h e bri-clc i n t h e m o r t a r . The t o p and bottom b r i c k s o f e a c h p a n e l , p r i o r t o p a n e l c o n s t r u c t i o n , were f i t t e d

w i t h b r a s s p i n s u s e d t o measure c h a n g e s i n t h e p a n e l h e i g h t .

A m i c r o m e t e r head which gave r e a d i n g s t o 0.0001 i n c h was used f o r m e a s u r i n g t h e d i m e n s i o n a l c h a n g e s .

CONDITIONS OF CONSTRUCTION

P a n e l s were assembled u n d e r t h r e e c o n d i t i o n s : ( a ) The b r i c k s a n d t h e f r e s h l y mixed m o r t a r , b o t h a t a t e m p e r a t u r e of 73OP, were a s s e m b l e d i n t o p a n e l s i n a room a t 73OP, and remained a t t h a t t e m p e r a t u r e u n t i l t e s t e d .

( b ) S r i c k s a n d f r e s h l y mixed m o r t a r , b o t h a t a

t e m p e r a t u r e of 73OF were t a k c n i n t o a c o l d room m a i n t a i n e d a t Oo.F and i m m e d i a t e l y made i n t o p a n e l s .

( c ) _Freshly mixed m o r t a r a t a _{t e m p e r a t u r e of '7T°F}

and b r i c k s ? t a t e m p e r a t u r e of OOP were assembled i n t o p a n e l s i n a c o l d room m a i n t a i n e d a t OoP. The second s i t u a t i o n ( b ) was i n t e n d e d t o c o r r e s p o n d t o t h e p r a c t i c e o f p r o v i d i n g h e a t e d b r i c k s a n d m o r t a r t o t h e b r i c k l a y e r ; t h e b r i c b ~ o r k a f t e r c o n s t r u c t i o n w a s u n p r o t e c t e d and c o o l e d below t h e f r e e z i n g p o i n t . The t h i r d c o n d i t i o n ( c ) was i n t e n d e d t o c o r r e s p o n d t o t h e p r a c t i c e o f u s i n g w s r m m o r t a r w i t h c o l d b r i c k s and t h e masonry l e f t u n p r o t e c t e d and c o o l e d below t h e f r e e z i n g p o i n t . The d i f f e r e n c e between c o n d i t i o n s

( b ) and ( c ) i.s e s s e n t i a l l y

i n

t h e r a t e o f F r e e z i n g o f t h e m o r t a r ; t h e warm b r i c k o f concli-tion ( b ) would produce a s l o w e r r a t e o f c o o l i n g o f t k e m o r t a r , compared w i t h t h a t o f t h e m o r t a r l a i d i n c o n t a c t w i t h t h ? c o l d b r i c k c o n d i t i o n ( c ) .

I t l,vas c o n s i d e r e d t h 8 t a n y damage t o b r l c b v o r k a s a r e s u l t o f f r e e z i n g would be more s e v e r e i f e a r l i e r P r e e z i - n g o f t h e f r e s h m o r t : . ~ r t o o k p l a c e , and f o r t h i s r e a s o n no s t u d y was made o f t h e e f f e c - t s of f r e e z i n g b r i c b v o r l r which h2(1 b e e n aged f o r a c o n s i d . e r a b l e l e n g t h o f t i m e a t a b o v e - f r e e z i n g t e m p e r a t u r e . A l s o , t h e e f f e c t of a l t e r n a t e f r e e z i n g and t h a w i n ~ was n o t

i n v e s t i g a t e d .

For t h e p a n e l s consl;ructec3 und c r "normal" c o n d i t i o n s (73OY) t h e p r o c e d u r e nclopted was t o ::-tore t h e completed p a n e l i n R p1.ar;ti.c c o l ~ c : r f o r 74 h o u r s , thc.t~ I ~ ~ t h e uncovered p a n e l C C

i n a h i ~ h - h t ~ m i d i t y chamber ('7Y0Te and 100 p e r c e n t

R.H.)

f o r 6 d a y s . I t was t h e n removed from t h e chamber and t e s t e d f o r

moist us:^ p e n e t r a t i o n . Aftewvnrds, t h e p a n ~ l was p l a c ? d i n a

room a t 7-3O1;',

50

p e r c e n t R . H . , untj.3 age 1 4 d a y s .hihen t h ~ bond s t r e n g t h t e s t was made.

The pa:lc,l-s which were c o n s t r u c t e d i n t h e c o l d room werc l e f t t h e r e f o r 21 2,ours. On removal t h e y were p l a c e d i n t h e h i f h - h u m i d i t y chamber (73'F and 1 0 0 p e r c e n t R . 9 . ) f o r 7

days and t h e m o i s t i l r e p e n e t r a t i o n t e s t was t h e n made, A f t e r t h i s t e s t t h e r e was a p e r i o d o f ::torage a t 73OP and 50 p e r c e n t

R.H. i ~ n t i l t h e p a n e l was 1 5 d a y s 014, v~hen t h e bond s t r e n g t h

was d e t e r m i n e d .

Some p a n e l s were made of l i m e m o r t a r , i n which c a s e t h e y were s t o r e d a f t e r c o n s t r u c t i o n f o r 1 4 d a y s i n a room a t 73OF and 50 p e r c e n t R.H. ( r a t h e r t h a n

7

da$s a t 100 p e r c e n t h u m i d i t y a s f o r t h e o t h e r p a n e l s ) , and a t a g e 1 4 d.ays t h e m o i s t u r e p e n e t r a t i o n t e s t was made. The bond s t r e n g t h t e s t of p a n e l s of l i m e mort;ar was mad.e a t a g e 28 d a y s ( i n s t e a d of 1 4 d a y s a s f o r t h e o t h e r p a n e l s ) .

One t y p e of b r i c k was u s e d , a d e n s e , l o w - s u c t i o n r e d b r i c k made by t h e e x t r u s i o n p r o c e s s . The i n i t i a l r a t e of

a b s o r p t i o n was i n t h e r a n g e 1 t o

5

p e r minute p e r 30 s q u a r e i n c h e s . The b r i c k s c o n t a i n e t l 10 c o r e h o l e s , a r r a n g e d i n two rows, and t h e s u r f a c e s o f t h e b r i c k s were smooth, n o t t e x t u r e d .

MORTARS

Lime, p o r t l a n d cement, m i x t u r e s of l i m e and p o r t l a n d cement, and two t y p e s of masonry cement were used w i t h s a n d t o p r e p a r e m o r t a r . The r a t i o b y volume of c e m e n t i n g m a t e r i a l t o sand was 1 : 3 , e x c e p t f o r one of t h e masonry cements which i n

a c c o r d a n c e w i t h t h e m a n u f a c t u r e r ~ s recommendation was p r o p o r t i o n e d

w i t h sand i n t h e r a t i o 1:2-213. One masonry cement was a n i n t e r - grouncl m i x t u r e of p o r t l a n d cement and l i m e s t o n e , w h i l e t h e - o t h e r was a b l e n d of p o r t l a n d cement and h y d r a t e d l i m e .

One of t h e cement:lime m o r t a r s was composed o f one p a r t by volume of w e l l - a g e d l i m e p u t t y , two p a r t - s of p o r t l a n d cement and n i n e volilmes of s a n d , w h i l e t h e o t h e r cement:lime m o r t a r c o n t a i n e d two p a r t s of l i m e , one p a r t of p o r t l a n d cement and n i n e p a r t s of s a n d ,

The m o r t a r s were used i n two c o n s f ~ s t e n c i e s of 115 p e r c e n t and 1 2 5 p e r c e n t f l o w a s measured by t h e f l o w t a b l e . H i g h l y v a r i a b l e flax v a l u e s of d u p l i c a t e b a t c h e s of t h e same m o r t a r , however, werc frequently n o t e d .

Thc r e s u l t s o b t a i n e d from t h e t e s t s a r e sumrnarizecl i n Table I. The corrlposition of t h e m o r t a r used i n t h e p a n e l

and its flocv, t h e c o n d i t i o n s under which t h e p a n e l was c o n s t r u c t e d , t h e d i m e n s i o n : ~ l changcs which o c c u r r e d , t h e t o t a l amount of

lealcace wlrich t o o k p l a c e i n 24 h o u r s of t e s t f o r m o i s t u r e penc.tra-tion, and t h e average bond stren'gth of t h e f o u r m o r t a r

j o i n t s of t h e p a n e l , a r e shown. DIMENSIONAL CHANGES

-

!Vhen b r i c k s and m o r t a r were assembled und-er "normal" c o n d i t i o n s ( i n a room a t

73OF)

and were maintained a t t h i s t e m p e r a t u r e

u n t i l

t h e t e s t s were made, i n a l l c a s e s s h r i n k a g e

of -6he panel t o o k p l a c e . Most of t h e movement t o o k p l a c e i n t h e f i r s t

7

days ( i . e . up t o t h e t i m e of t h e l e a k a g e t e s t ) .

I n -the n e x t

7

days ( u p t o t h e t i m e of t h e bond s t r e n g t h t e s t ) t h e r e was l i t t l e a d d i t i o n a l s h r i n k a g e . The f l o w ( w e t n e s s ) of t h e m o r t a r d i d n o t a p p e a r t o i n f l u e n c e g r e a t l y t h e amount of

s h r i n k a g e . The maximum s h r i n k a g e was s l i g h t l y l e s s t h a n 0.007 i n c h , i n a n e f f e c t i v e p a n e l h e i g h t of a b o u t 11 i n c h e s , o r about 0.06 p e r c e n t .

',Then t h e b r i c k s and m o r t a r were assembled i n t h s c o l d room, however, t h e dimensional changes were q u i t e d i f f e r e n t from t h o s e of p a n e l s assembled under "normal1' c o n d i t i o n s . I n s t e a d of s h r i n k a g e , expansion occurred d u r i n g t h e f r e e z i n g of t h e p a n e l s . When t h e p a n e l s were thawed ( a f t e r 24 h o u r s i n t h e c o l d room), a pronounced s h r i n k a g e t o o k p l a c e . T h i s "thawing s h r i n k a g e " i n some c a s e s exceeded t h e i n i t i a l " f r e e z i n g expansion" and i n o t h e r c a s e s was l e s s t h a n t h e expansion, s o t h a t a n e t

movement i n t h e p a n e l from t h e f r e e z i n g and thawing r e s u l t e d . The " f r e e z i n g and thawing" movements were a p p r e c i a b l y g r e a t e r i n e x t e n t t h a n t h e "normal1' s h r i n k a g e of unfrozen p a n e l s .

The d i f f e r e n c e

i n

r e s u l t s between p a n e l s made of c o l d b r i c k s and t h o s e made of warm b r i c k s

( i n

b o t h c a s e s assembled i n t h e cold

room)

appeared t o be i n t h e r a t e of f r e e z i n g , and

it appeared t h a t w i t h t h e c o l d b r i c k s t h e m o r t a r o f t h e bottom j o i n t s of t h e p a n e l was f r o z e n b e f o r e t h e p a n e l was completed, and f o r t h e s e j o i n t s t h e r e f o r e t h e " f r e e z i n g expansion" had t a k e n p l a c e b e f o r e measurement of p a n e l h e i g h t was made.

A f t e r t h e bond s t r e n g t h t e s t s were made, d i s t i n c t i v e " c r o w f s - f e e t " c r y s t a l p a t t e r n s were observed a t t h e b r i c k - m o r t a r i n t e r f a c e of many of t h e p a n e l s which had been f r o z e n . There seems l i t t l e doubt t h a t t h e " f r e e z i n g expansion." was due t o t h e formation of i c e c r y s t a l s i n t h e mortar, o r between m o r t a r and b r i c k , and t h e p a t t e r n s of t h e c r y s t a l s remained a f t e r thawing. MOISTURE PXNETI?ATION

-

A s shown i n Tablq I , o n l y t h o s e p a n e l s of t h e two masonry cements had no l e a k a g e t h r o u & t h e p a n e l i n t h e 24 h o u r s of t e s t when c o n s t r u p t e d under "normal" a s w e l l a s under

e a r l y - f r e e z i n l : con(li.tions. The r e s j . s t a n c e t o moisture p e n e t r a t i o n of thesc! p a n c l s thr?rcrt'o.re, a p p a r e n t l y was n o t i n f l u e n c e d by

e a r l y f r e c z i n ~ : . I n n S l o t h e r c a s e s however, t h e cons1;rucl;j.on o f t h e p a n e l s i n t h e cold room had a n a d v e r s e e f f e c t on r e s i s - t a n c e t o m o i s t i ~ r o pt!nf?tra-tion. For example, p a n e l s of t h e p o r t l a n d cement and sand. m o r t a r and. of t h e cement-lime m o r t a r s

( 1 : 2 : 9 cement:lime:sand and 2:1:9 cernent:lime:sand) when

c o n s t r u c t e d ~ ~ n c i e r condi-Lions had no lealcage of w a t e r i n 24 h o u r s of t e s t , b u t when c o n s t r u c t e d i n t h e cold room, however, t h e r e was lealcage through t h e p a n e l s i n t h e m o i s t u r e p e n e t r a t i o n t e s t . The e a r l y f r e e z i n g of t h e s e p a n e l s , t h e r e f o r e , r e s u l t e d i n more permeable briclcworlc. S i m i l a r l y , t h e p a n e l s of t h e lime : sa.nd mortar c o n s t r u c t e d und.er "normal" c o n d i t i o n s

allowed a p p r e c i a b l e moisture p e n e t r a t i o n i n t h e 24 h o u r s of t e s t , and t h e amount of lealcage was g r e a t l y i n c r e a s e d when t h e p a n e l s were c o n s t r u c t e d . i n t h e c o l d room.

BOND STRENGTH

:Panels of a l l . m o r t a r s had lower bond s t r e n g t h when c o n s t r u c t e d . i n t h e c o l d room compared w i t h s i m i l a r p a n e l s con- s t r u c t e d . und.er "normal" c o n d i t i o n s . I n most c a s e s t h e r e d u c t i o n i n s t r e n o h was a p p r e c i a b l e . For example, p a n e l s of t h e 1 : 2 : 9 cement: lime: sand m o r t a r had a n a v e r a g e bond s t r e n g t h of a b o u t 12.5 p . s . i . when c o n s t r u c t e d und.er "normal11 c o n d i t i o n s , b u t only about h a l f t h i s v a l u e under cold. room c o n s t r u c t i o n . S i m i l a r l y , f o r p a n e l s of t h e 2 : l : g cement:lime:sand m o r t a r , t h e "normal" bond s t r e n g t h was o v e r

30

p . s . i , b u t t h i s was reduced. t o a b o u t 21 p . s . i . f o r c o l d room c o n s t r u c t i o n w i t h warm b r i c k s , and t o about 16 p . s . i . f o r c o l d room c o n s t r u c t i o n w i t h c o l d b r i c k s . For s e v e r a l of t h e p a n e l s s u b j e c t e d t o e a r l y f r e e z i n g t h e bond. s t r e n g t h was c o n s i d e r a b l y l e s s when c o l d b r i c k s were used. t h a n warm b r i c k s . I t i s c l e a r from t h e r e s u l t s shown i n Table I t h a t e a r l y f r e e z i n g of t h e p a n e l s r e s u l t e d . i n c o n s i d e r a b l y lower

s t r e n g t h of bond t h a n t h a t o b t a i n e d from "normal" c o n s t r u c t i o n ,

BOND STRENGTH OF PR0Z:EN BFUCICl"J0RK

Tiken though t h e bond s t r e n g t h of p a n e l s which were f r o z e n t h e n thawed was l e s s t h a n t h a t of s i m i l a r p a n e l s whlch had n o t been f r o z e n , it was found t h a t w h i l e a p a n e l remained f r o z e n it had a p p r e c i a b l e s t r e n g t h of bond. T h i s was determined by makine a t e s t f o r bond s t r e n g t h while a p a n e l was i n t h e

f r o z e n s t a t e . The bond s t r e n g t h t h u s measured was o v e r 7 0 . p . s . i , , compared w i t h l e s s t h a n 1 2 p.s. i. f o r s i m i l a r b r i c k and m o r t a r assembled without subsequent f r e e z i n g . I t a p p e a r s t h a t i c e may

Iorm a comenting m a t e r i a l between t h e b r i c k s , adding t o t h e s t r e n g t h of t h e assemblage a s l o n g a s it remains a s i c e .

A f c v r t e s t s were made u s i n g 2-inch cubes of a masonry ccmen-t rnortar .to i n v e s t i g a t e t h e e f f e c t of e a r l y f r e e z i n g o f t h e frqr.h m o r t a r on i t s compressive s t r e n g t h . No a p p r e c i a b l e d i I f e r e n 2 e i n compressive s t r e n g t h was noted however when cubes

were made and s t o r e d under "normal1t

(73OP)

c o n d i t i o n s and when s i m i l a r cubes were frozen a t a n e a r l y age t h e n thawed and

subsequently t e s t e d . The compressive s t r e n g t h of mortar cubes which had been f r o z e n , and t e s t e d while s t i l l f r o z e n , s l i g h t l y

exceeded t h e compressive s t r e n g t h of "nonnal" mortar cubes i n d i c a t i n ~ t h a t t h e presence of i c e i n t h e mortar contribu-l-es

t o t h e compressive s t r e n g t h a s l o n g a s it remains a s i c e .

The e f f e c t of e a r l y f r e e z i n g of b r i c k masonry panels on dimensional changes, bond s t r e n g t h and r e s i s t a n c e t o moisture p e n e t r a t i o n was s t u d i e d . The i n v e s t i g a t i o n was r e s t r i c t e d t o

t h e use of a low s u c t i o n b r i c k w i t h mortars of s e v e r a l compositions. Panels c o n s t r u c t e d without subsequent f r e e z i n g shrank, v!hile t h o s e which were c o n s t r u c t e d i n a cold room expanded, and

subsequently shrank on thawing. The s t r e n g t h of bond between b r i c k and mortar i n a l l c a s e s was reduced a s a r e s u l t of t h e e a r l y f r e e z i n g , when compared with t h e bond s t r e n g t h of s i m i l a r panels which had n o t been f r o z e n . The e f f e c t of e a r l y f r e e z i n g on r e s i s t a n c e t o moisture p e n e t r a t i o n was v a r i a b l e ; some panels were f r e e of leakage under both "normal" and " e a r l y f r e e z i n g "

c o n d i t i o n s of c o n s t r u c t i o n , while o t h e r s v e r e l e a k - f r e e under llnormaltt c o n d i t i o n s b u t were permeable when b u i l t under f r e e z i n g c o n d i t i o n s , ? a r l y f r e e z i n g o f b r i c k masonry of t h e m a t e r i a l s used t h e r e f o r e s i g n i f i c a n t l y a f f c c t c d t h e p r o p e r t i e s of t h e brickwork; t h e f o m a t l - o n of i c e c r y s t a l s a t t h e brick-mortar i n t e r f a c e and i n t h e mortar was observed.

Thc s t r e n g t h o f bond, and compressive s t r e n g t h , of b r i c l c ~ o r k while s t i l l i n t h e f r o z e n s t a t e was i n d i c a t e d . t o be h i g h e r t h a n t h a t of unfrozen b r i c h ~ o r ' . ~ , t h e i c e a p p a r e n t l y a c - t i n g a s a cementing agent.

REPERENCES

(1) R i t c h i e ,

T.

A Small-panel method f o r i n v e s t i g a t i n g moisture p e n e t r a t i o n of b r i c k masonry. National Research Council, Division of B u i l d i n g Research, I n t e r n a l Report No. 160, Ottawa, September 1958.

( 2 ) Hodgins, P. T. Small r i c k panel t e s t s a t Ottawa

-

a p p a r a t u s and t e c L l i q u e s f o r s t u d y of bond s t r e n g t h .

National Research Council, Division of Building

T A B L E I RESULTS OF TESTS MORTAR COMPOSITION l:3 Lime: Sand I t I ? I t n ?I TOTAL

DIMENSIONAL CHANGE ( INCRES ) ( LEAKAGE AVERAGE

MORTAR CONDITION OF NORMAL ON ON 24 BOND

n o w

CONSTRUCTION (+I CONSTRUCTION FREEZING THAWING HRS

.

S T ~ G T H

rn

( p . s . 1 . )

1 2 5 Normal -0 .OOSS 443 1 3

115 Normal -0.0056 527 1.5

125 Cold Room

-

Warm Bricks +0.0136 -0.0247 no t e s t 0

115 Cold ?toom

-

Warm Bricks +O .0210

-OO.Oy

3035 4450

0

125 Cold Room

-

Cold Bricks + O . O O O ~ -0.05 2 0

115 Cold Room

-

Cold Bricks no t e s t no t e s t no t e a t 0

1:2:9 Cement: Lime: Sand 125 Normal -0.0033 0 12.8

l? 115 Normal _{-0.0025 0 12.9}

II 125 Cold Room

-

Warn Bricks +O .0137 -0 .Ol3O _{164 6.8}

?t 115 Cold Room

-

Warm Bricks +O.O2O9 -0.0150

350 6.2

n 125 Cold Room

-

Cold Bricks +O .0019 -0.0165 78 6.1

11 115 Cold Room

-

Cold Bricks + O . O O ~ -0.0175 161 6.5

2:1:9 Cement: Lime: Sand 125 Normal -0.0024 0 36.6

11 115 Normal -G 0017 0 31 3

I( 125 Cold Room

-

Warm Bricks +0.0168 -0.0082 217 20.2

I! 115 Cold Room

-

Warm Bricks +O. 0183 -0 -0078

11 125 Cold Room

-

Cold Bricks no t e s t -0.0062

4g

17.8

22.5

11 115 Cold Room

-

Cold Bricks +0.0018 -0.0081 7 2

14.4

3 Portland Cement: Sand 115 Normal -0.000s 0 45 2

II 115 Cold Room

-

Warm Bricks +O .Ol45 -0 -0077 120 13.1

I 1 115 _{Cold Room}

-

_{Cold Bricks +O .0057 -0.0150 128 10.9}

1 : Masonry Cement: Sand

11

1: 2 2/3 Masonry Cement: Sand

11

No r n a l Nonnal

Cold Room

-

Warm Bricks Cold Room

-

Warm Bricks Cold Room

-

Cold Bricks Cold Room

-

Cold S r i c k s Nonnal

Normal

Cold Room

-

Warm Bricks Cold Room

-

Warm Bricks Cold Room

-

Cold Bricks Cold Room

-

Cold Bricks

-0.0010 -0.0014 +O

.

00 34 +O .0058

%.88?8

-0.0035 -0.0038 +o .0140

+o

.0020 no t e s t no t e s t

( G ) Normal = M a t e r i a l s a t 7 3 ' ~ c o n s t r u c t e d and maintained a t temp. of 7 3 O ~ . ( ) Minus s i g n i n d i c a t e s shrinkage

Cold Room

-

Warm Bricks = b r i c k s and mortar a t 73OF brought i n t o c o l d - Plus s i g n i n d i c a t e s expansion room f o r assembly.