Some aspects of the problem of moisture penetration of brick masonry

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Some aspects of the problem of moisture penetration of brick masonry Ritchie, T.

Ser

m

BY2 no. 1 2

c . 2

SOME ASPECTS

OF

THE PROBLEM

OF

MOISTUFE

PENETRATION

OF

BRICK MASONRY

T.

R i t c h i e

Information

taken

from a paper p m s e n t e d -ta

t h e

50th Annual

Convention of

the Canadian Ceramic

.

Society,

February

12,

1952.

3,'.i/"s, ;:-

I n v e s t i g a t f ons o f t h e

performance

or

v m i a u s ~ a t e r l a l s o f

c o n s t r u c t i o n , 5ncPuZzing brick masonry, hare Seen undertaken by the Division of B u i l d l n ~ Research of the h r a t l o n a l Ee s e a r c h C o m c i l * , One p r o b l e n l a f f e c t i n g t h e perfltrmmce oi' b r i c k roasonrg

in

c e r t e 5 n areas

of

Canada has been the p e n e t r a ~ i o n

of

S r i c k w o r k by m o i s t u r e .

This

p e r t i c u l a r p r o b l e m and some o f t h e f a c k o r s a s s o c i a t e d w i t l ~ Tts occurrence, p a r t i c u l a r f y the i n r l u e n c e of scve p r o p e r t i e s o f

the

masonry

~ a t e r l a l s , a r e d i s c u s s s d

in

this t i o t e , The u s e or

ivpervious msmbrmes on the e x t e r i c r

uf

masonry

a s

a m e a n s ~f excluding mcisttu?e w i l l

not

h e d e a l t w i t h her^,

Because of t h e wide v a r i a t t s n

Zn clL~atic

conditlona

in

v a r i o u s p a r t s o f Canada, a c r i t e r f on of s a t i s f a c t o r y p e r f o r ~ a n c e of

a

rnzscnry ;material enclosing a buTlding in *he f i a f ~ i s P r o v i n c e s

may be i + , s i n s u l a t L q p r o p e r t i e s , whereas 2 2 t h e M a r l t t m e P r c v i z c e s

I t mzy Se

its

r e s i s t a n c e to r a i n p e n s t r a t L o n ,

I x v e s + , i g a t i o n s

by

the D i v l s i o r ,

wT5h

respect; kc the p e r f o r - mance o f masonry, both of n a t u r a l s t o n e s and o f c l a y p r o d u c t s , have fnclud-ed:

firs%,

a s t u d y of l S t e r a t u r e d e a l i n g with t h e weztherkng

of masonry

m a t e r i a l s and t h e elated p r o b l e m of r ? l o i s t u r e pene5ration; s e c o n d , a f i e l d a u r v e y

of

the performance sf masonry fn t h e M = i f i r n s

P r o v i n c e s , and $0 E l e s s e r ~ x t e l n t e l s e w h e r e ,

and

t h i r d , t h s d e t e r m i -

n a t i o n , on a v e r y l T m i t e d s c a l e , o f some p r c p e r t l e a a f Cmadian masonry m a t e r i a l s which have been r e p o r t e d t o

i n f l u e n c e

3 e r f omance

of

masonry

with r e s p e c t $c

n o i s t ~ ~ e

r e s i s t a ~ c e ,

In

a s u r v e y of the performance o f ms.sonr.y s t r v - c t u r e s Ln

%he

M u i t i r n s P r o v i n c e s c a r r i e d out in the f a l l of

1950,

it >:as fcw-d t h a t d e 5 e r i o ~ a t i o n of masonry 5n g e n e r a l , and ncfskure psne 5ratim of' b ~ i c k t r o r k + ir, p a r t i c u l a r : are p r o b l e w a of v u c h ccncern t o a. g r e a t

manF architects, b u l l d e r s and c o n t r a c t o r s t h e r e , Although t h e r e are many examples o f e x c e l l e n t p e ~ f c r m a n c e ol"

b ~ l e k

mascnyy

In

:he

~ ~ ~ a r l t f m e P r o v h c s s , e s p e c i a l l y o r scms s l d e r b u f I d i n g s , 'c'hers are a l s o numerous relatively m o d e m b u E l d i n g s cr' b r c c k nrasonrg in r ~ f i i c h moisture p e n e t r a t i c n has had damaging e f f e c t s ,

The problem of r a i n penetraticm of b r i c k m a s o m y has been experienced

in

rea at

B r i t a i n and the U n i t e d S t a t e s , p a r t Z c u l a r l y

t h a t part o f t h e

U,S,

along t h e n o r f , h - e a s t e r n c e a s t , as w e l l as :n

Canada* In 1931, B,S, d r i g h t l y ( I ) ,

in

discussing some economfc

a s p e c t s

of

masonry decap Tn the Unlted S t a t e s wrote

"

.

.

.

I t seems

i m p o r t a n t to p o i n t t o moisture p e n e t r a t i o n as the b i g f a c t o r

in

considerzng the s u r f a c e disintegration, or decay, o f masonry

n a t e r t a l s , and, in consequence o r t h i s , to p o i n t out t h e 5flpor.-

t a n c e of t a k b g e v e r y means of prevenfing

the

penetration o f m o i s t u r e

The f i r s t s y s t e a a k i c r s s e a r c b UE r a i n y e n e t r a t i o s t h r o u g h

brickwork a p p e a r s

to

have b e e n s t a r t e d about

la32

a d e a r l y s t u d i e s i n d i c a t e d t h a t when mof s t u r e p a s s e d through Srickr,rrork L t seemed t o do so

most

r e a d i l y at

the

juncture of b r i c k

and m o r - t a r ,

Ln

a study b y p e t r o g r a p h i c m t h o d s of

t b

bcnd between bricks and r n o r t a ~ s

r e p o r t e d

i n

1 9 3 T 9 S t a l e y ( 2 ) c l a i m e d t h a t when moisture leskage t & a s

p l a c e

in

brickwor!:

it

d o e s s o at t h e brick and m o r t a r i n t s r f a c e , He r e p o r t e d t h a t i n t i m a c y , c m t i n u i t g , and permenonce of i n t e r f a c i a l bond is n e c e s s a r y for w a t e r - t i g h t n e s s of masonry w a l l s ,

1

t

had been o b s e r v e d by s e v e r a l i n v e s t i g a t o r s , however,

t h a t b r i c k s of c e r t a i n p r o p e r t i e s in combination w i t h c e r t a i n m o r t a r s

a p p a r e n t l y d l d not; p r o d u c e rafn-re slsting w a l l s ,

In

;L929, J - W l@:cBurrzey

( 3 )

at t h e N a t i o n a l B u r e a u of S t a n d a ~ d s p o i n t e d

o u t

t h e i m p o r t a n c e

of

o p e n i n g s

in

the m a s o n r y as a s o u r c e of leaka,ge, h i s ~ p i n i c n having been f o r m e d "

.

? , a f t e r o b s e r v z t 2 o n s

of

w a l l constructions where the

f a c e of t h e w a l l w a s l a i d up wTth h g g h l y i p n p e ~ v f o u s and i ~ c n e t r a b l e bricks, a r i c h cerclent n o r t a r w a s u s e d and a back-up of i ~ e ~ v l o u s units and

In

s p i t e of all t h l s the w a l l t r a n s m i t t e d water a b u n d a n t l y wibh r a i n s aad winds of mode-rate d u r a t i o n and i n t e n ~ ? ~ t y .

It

wae

o b s e r v e d

that

t h e m o r t a ~ jofnts had a g p a r e n t l y shrunk, leaving c 2 a c k s between the bricks and m o r t a r in som c a s e s of s u c h sfze as t o pemnft t h e insertion of a k n i f e blade

an

inch

o r

m o r e " .

W,C,

Voss,

14)

of the Massachusetts I n s t i t u t e o f Technology, a p f o n e e r in i n v e s t i g a 3 i o n s o~ the leakage o f b r i s k w o r k observed

Tn

1933

t h a t

"

,,

.

the w a l l s t h a t a r e causing

this

t r o u b l e t a - d a y a r e

the ones where r e l a t i v e l y dense brlcks have b e e n l a i d with r e l a t i v e l y strong and dense m o r t m " ,

He

also p a i n t e d o u t

that

" S t r e n g t h f s n o t t h e c r i t e r i o n f o r m o r t a r bond''.

C - C , C o n n o r

(51

r e p o r t e d in

1934

t h a t t h e development of l a c k of b m d bef,ween b r i c k

and

m o r t a r

i n

buildings, which h e c e l l e d

II _{s e p a r a t i o n c r a c k i n g " , w a s r e l a t e d in ex-Lent t o the r a t e}

of

a b s o r p t i o n o r the b r i c k s used and the lime c o n t e n t o f t h e m o r t a r

u s e d ,

Dr,

V o s s

(4)

had p c i n t s d o u t t h a t t h e natwe and e x t e n t

of t h e bond establfshed between

brick

and m o r t a r

gas

a p p a r e n t l y

i n f l u e n c e d to a consfderabLe degree by the r a t e of water absorption

of

t h e b r i c k u s e d , The same idea w a s expressed b y E , O , Hills ( 6 )

in

1932

who wrote " , , , the efficiency o f the u n i o n of b r i c k and . n o r t a r

is

i n t i m a t e l y a s s o c i a t e d w i t h the e a s e w i t h which

the

b r f z k

czul absorb t h e w a t e r , t o g e t h e r with same of the f i n e r p a r t i c l e s of t h e mortar" l,

P s o p e ~ t i e a of d r i c k t.lasolnrg and !.lostars

It

is w e l l known t h a t c l a y b r i c k s exhi'oit widely d i f f e r - l n g p r o p e r t f e s w l t h r e s p e c t to

amount

and

r a t e

of

w a t e r a b s o r p t i o n .

Some d e n s e , a l m o s t v i t r l r i e d b r i c k s absorb w a t e r v e r y s l o w l y a n d t h e i r t o t a l a b s o r p t i o n is r e l a t i v e l y l o w , o f t e n less than 2 p e r c e n t of t h e d r y weight; t h e r e are, h m e v e r , p c r o u s b r i c k s which t a k e up w a t e r

than 20 p e r cent of t h e d r y w e i g h t . The nlarcyer of f o r m i n g b r f c l r s s e e v s -t;o i n f l u e n c e t h e r a t e of a b s o r p t i o n , F o r s x a ~ y l e , r.~c?jurneg

( 7 )

has r o u n d t h a t

f o r

bricks

wlth

t h e s a w t o t a l absorption, dry p r e s s b r i c k s have a much h i g h e r r a t e of a b s o r i k 3 t i ~ n t h a n s o f t ; mnd b r l c k s ,

The initial r a t e :01 w a t e r z b s o r ~ t i o n

cf

b r i c k s

is

g e n e r a l l y

measwed according to t h e m e t l ~ o d tlf the d ~ e r i c a n S o c i e t y f o r T e s t i n g Piaterials. The weighed dry b r i c k is p l z c e d flat s Z d e down in

1\8

lnch or w a t e r for one minute and :&an revoved and re-weighed t h e i n c r e a s e

in

w e i g h t in p a m s corrected t o a s t a n d a r d a r e a of 30 square inches 1 s taken as t h e initial r a t e of p r a t e r a b s o r p t i o n . T h i s measurement

allows a comparison to be rnade of the r e l a t i v e " s u c t i o n T ' p r o p e r t y of b r i c k s ,

There is wide variation in this p r o p r t g of " s u c t i o n " of

b r i c k s , and a l s o t h e r e 1 s a c o n s i d e r a b l e v a r T a t i o n in

the

p r o p e r t i e s of m o r t a r s u s e d

in

binding b r i c k s t o g e t h e r ,

Almost i n v a r i a b l y m a s o n q m o r t a r s a r e composed of" a p a s t e of p o r t l a n d cement o r a p a s t e

of l i m e ,

or a mixture of the two,

and

s a n d , iuiortars which c o n s i s t essentially of a p a s t e of p o r t l a n d

cevent

and

sand a r e c h a r a c t e r i z e d by r a t h e r harsh w o r k i n g p r e p e r t z e s ,

r e l a t i v e l y

low

a b i l i t y to r e t a i n m o i s t u r e when p l a c e d in

c o n t a c t

w i t h

an

absorbent n a t e r i a l ,

and

r e l a t i v e l y qujck rlevelo_ament o f strength. On the o t h e r hand, n o r t a r s which a r e of l i m e paste and sand, p r i m a r i l y ,

are

u s u a l l y highly p l a s t i c and e a s i l y worked, w i t h a

high

c a p a c i t y

to r e t a i n moisture

and

a r e l a t i v e l y s l o w development of strength,

T o

o b t a i n some o f the d e s i r a b l e c h a r a c t e r i s t i c s o f b o t h t y p e s , m o r t a r s a r e a l m o s t always a m i x t u r e of l i m e and p o r t l a n d cement p a s t e s . F o r example, a

c o r n o n

r n m t a r has the p r o p o r t i o n s

1:P:6,

one volume

of

portland cement to one v o l u v e of' l i m e t o six volumes of sand.

A l t h o u g h d i f f e r e n t l i m e s e x h i b i t Cif rerent, degree s

of

p l a s - t i c i t y , it is g e n e r a l l y c o n s i d e r e d t h a t the p l a s t i c i t y , ~ r o r k a b i l i t y and water-retaining c a p a c i t y

o r

a m o p t a r i n c r e a s e s w i t h I n c r e a s e

in

IZve c o n t e n t , StaLey

(2)

a s s e r t s t h a t "Mortar

must

have p l a s t i c i k y and w o r k a b i l i t y t3 enable a w o r k m a n

to

do a good job, P l a s t i c i t y

and

a b 5 l i t y to g a i n intimacy of c o n t a c t a r e the e s s e n t f a l s o f a good YaSunry W O T

t

a r t $

.

If we

c o n s i d e r t h e brlnging t o z e t h e r of a b r z c k of h i g h

11 _suction"

and a m o r t a r of low water--retaining c a p a c i t y ,

it

may be v i s u a l t z e d t h a t a l a r g e p r o p o r t i o n o f the w a t e r

in

the a d r t a r may

be taken up by the b r i c k , t h u s p r e v e n t i n g complete l ~ y d r a t i o n of the cement in the m o r t a r and a d v e r s e l y a f f e c b i n g t h e q u a l i t y of the bond of the m o r t a r , S i m i l a r l y , as has been d e s c r f o e d by S t a l e y (21,

when any t y p e of m o r t a r , w l t h high

or

low watey-setaln5ng c a p a c i t y , is b r o u g h t

in

c o n t a c t

wlth a

v e r y dense b r i c k ,

w a t e r

v o i d s may f o m at the j u n c t i o n of the brick and m o r t a r and a f f e c t , the bond between t h e

t w o .

Y o m e s s e n t i a l p r o p e r t f e s of masonry unff;s a 4 r c o r t a r s

w i t h ~ e s ; 3 e c t t o t h e bond d e v e l o p e d betvesn the two have bee=

c o n s i d e r e d alaove. Whzt then, in. p r ~ c t i c e , m e t h e l l m i t , s 3n t h e i n i t i a l r a t s of a b s o r p t , i c n o r f ' s u c t 5 ~ n "

of

b r i c k s and the ceqpo- sition of n o r t a r s , to g i v e assuraxce t h a t , w i t h r e s 2 e c t

t o

r e s i s t a n c e

to

moisture p e ~ e t ~ a t i a n ,

a

s a t i s r ' n c t o r y bond be

tween

S r i c k and

m o r t a r

uf 11 tdke p l ~ e e ?

An

answer to t h i s q u e s t i c n

was

p r o v i d e d by C * C , Connor in 1948,

O - r ~ e r a nlmber of g e a r s Connor

( 8 )

made o b s e r v a t i o n s on

the p e r f a r v m c e ,

with

r e s p e c t t o r a i n r e s i s t m c e , of E large number

of

b r i c k masonry b u l l d i n g s s i t u a t e d i n an a r e & of t h e Vnited S t a t e s

in

which raLn p e n e t r a t i o n of b r l c k w o r 2 h a s been a problsrn, He: has r e l a t e d t h e resPstance o r lack of r e s i s t a n c e to r a l n p e n e t r a t i o n of t h e s e buLldlngs to c e r t a i n f a c t o r s i n the materials and p r a c t i c e s

of

their canstruckion,

This study I s cons5dered t.o be f - n p o r t a n t since here,

r i e l d p e r f ormmce i s r e l a t e d to s p e c i f i c p r o p e r t i e s or p r a c t i c e s , A s Mcfiurney

( 3 )

has p o i n t e d o u t "1% must be yemenbered t h a t f ieLd

o b s e r v a t i o n i s -in i t s e l f the

f i n a l

s t a n d a r d f o ~ . intexlprsting l a b o r a t ~ r y tests , It

F a c t o r s Determining M o i s t u r e R e s f s t a n c e

Generalizations on t h e r e l a t i o n s h i p batween g r o p e r t i s s of nlasonry m a t e r i a l s and v o F s t w e r e s i s t a n c e of masonry have been made by s e v e r a l i n v e s t i g a t o r s of t h e p r o b l e m ; some of t h e s e h a w been

mentioned above,

C o m e r ( 8 ) c l a s s i f f e s c e ~ t a i n f a c t o r s and p r a c t i c e s as

f avourable o r d e t r i m e n t a l t o t h e

ncisture

r e s f s t a n c e of b r i c k masonry s t r u c ' t ; u r e s , These f a c t o r s are: the r a t e of a b s o r p t i o n

of t h e brfcks, -the composition

of

the mor%ar, m d c e r t a i n a s p e c t s of the desfgn =d construc"ticn

of

the b u i l d i n g ,

T o ~ r o d u a e moisture-proof SuXldfngs c c n s i s t e n t l y ,

G

onnor

f ousld t h a t there must a x t s t In corriSinet2en f o u r f a v o u r a b l e f a c t o r s , with no d e t r i m e n t a l T a c t o r s , These f a v o u r a b l e f a c t o r s are: brick3 of moderate r a t e o r a b s o r p t i o n , m o r t a r s w i t h hfgh l i m c o n t e n t ,

concave m o r t a r j o i n t tooling, snd the u s e of p a r a p e t w a l l coverings

or

r o o f s , The following f a c t o r s w e r e f o u n d to be d e t r i m e n t a l by

Connor:

brecks w i t h h i g h or low r a t e of a b s o r p t f on, m o r t a r s

with

low l i m e content, f l a t - . t o o l e d , rough-cut and r a k e d m o r t a r joints,

spmcbel bearrr w a t e r p r o o f

fng,

and Kne use of p a r a p e t f l a s h i n g s t h a t do not completely c u t off

or

c o v e r t h e t o p and b a c k of p a r a p e t s ,

M o r t a r s

of

high water retentivity and the use of w a l l f u r r i n g were f o u n d t o be d e s i r a b l e f a c t o r s , The k i n d or t y p e of lime, the m a n u f a c t u r i n g p r o c e s s of t h e b r l c k , t h e back--up m a t e r i a l u s e d h i n t e g r a l walls a n d the h e i g h t of the w a l l s up to f o u r s t o r e y s

?id

not s e e a s in Cormor' s opinion

to

i n f l u e n c e s l g n i f icantl3- t h e m o i s t u r e r e s i s t a n c e ~f t h e b u t l d f n g s ,

I n

e l a b o ~ a f , i ~ n o f t h e above f a c t o r s Connor m o t e t h a t

t h e u s e

of

bricks

wlth

a

r a t e

of a b s o r p t f o n between

5

m d 25 gravs of water when a e t f l a t side down in

1/8

i n c h

of

w a t e r f o r 1 m i n u t e was a f a c t o r h i g h l y f a v o u r z b l e

t o

the moisture r e s i s t a n c e of b r i c k masonry

walls,

In

c o n t r a s t , he f o u n d t h a t t h e u s e o r b r f c k s w i t h a r a t e of a b s o r p t i o n greateF t h a n 25 grams was a f a c t o r d e t r i m e n t a l

ts

t h e m o i s t u r e r e s i s t a n c e of b r i c k masonry w a l l s ; a l s o ,

that

t h e use of

b r i c k s having a r a t e of a b s o r p t i o n l e s s t h a n

5

grams

of

water, as

rne asured above, a p p a r e n t l y was a f a c t or d e t r i m e n t a l t o t h e m o i s t u r e r e s i s t a n c e of b r i c k masonry w a l l s . C o n n o r f omd, h o w e v e q t h a t

the

e v i d e n c e

in

the l a t t e r case w a s

not

c o n c l u s i v e ,

Use of m o r t a r s w i t h EL l i m e c o n t e n t e q u a l t o

or

g r e a t e r

than

50 p e r

cent

of the volume of the c e m n t ' w a s found by C o n n o r to be a h5ghly r'avourable f a c t o r in the moisture r e s i s t a n c e of b r i c k masonry w a l l s , Concave t o o l i n g

of

the m o r t a r joints, a

p r a c t i c e which r e d u c e s the s e p a r a t i o n cracking between b r i c k s and

m o r t a r s was a l s o h l g h l y cormended,

Conslderine; only the p r o p e r t i e s of the masonry m a t e r i a l s

w l t h r e s p e c t to t h e problem o f r a i n p e n e t r a t i o n of brickwork, Connor found t h a t

two things

I n t r o d u c e d d e t r i m e n t a l f a c t o r s , These a r e the u s e of b r i c k s whose r a t e s of absorpition are o u t s i d e a n a r r o w

r a g e and the use o f m o r t a r whose l i m e content

is

l e s s than

a

c e r t a i n p r o p o r t i o n of the cement c o n t e n t ,

The r a t e s of a b s o r p t l o n ef s e v e r a l t y p e s or b r i c k s made in Canada and u s e d in a r e a s where r a i n p e n e t r a C i o n o r br5ckwar.L has o c c u r r e d have been f o u n d to Se _{o u t s i d e t h e d e s i s a b l e range of}

a b s o r p t i o n r a t e of between

5

and 25 grams,

In

cne instarlce, the r a t e was l e s s than

5

gravs,

in

another more than 100 grams, when t h e b r i c k s were s e t flat s i d e down

in

118

inch

of w a t e r

for one

m i n u t e ,

Another g u i d e t o a d e s i r a b l e r a t e o f a b s o r p t l o n

of

brfcks w i t h r e s p e c t t o the p r o b l e m o f

v o l s t u r e

penetration

is

provided by

the s p e c i f i c a t i o n f o r C l a y Building B r i c k of t h e Amerrcan S o c i e t y for T e s t i n g Ma.t;erials, C62-50, in t h e n o t e c o n t a i n e d t h e r e t n : "Data

i n d i c a t e t h a t a

1061.

r a t e o f s u c t f on ( 2 0 grams p e r m i n u t e or l e s s ) is

d e s i r a b l e b o t h f r o m the s t a n d p o i n t of bond and watertfghtnesst\ It a l s o s t a t e s t h a t "

,.,

t h e s u c t i o n r a t e

or

bricks t h a t n o r m a l l y have

h i g h r a t e s

of

s u c t i o n c a n be reduced to my p r e d e t e r m i n e d value b y wetting b e f o r e layLng

...

t l

The r a t e o f absorption o f b r i c k s , as p o i n t e d o u t above, decreases w i t h i n c r e a s e i n m o i s t u r e c o n t e n t of' t h e b r i c k s , B y i m e r s i n g brLcks in w a t e r or o t h e r w g s e w e t t i n g them b e f o r e u s e , it

i s p o s s i b l e

to

a l t e r t h e i r r a t e of' a b s o r p t i o n .

In

attemptfng tc do this

on

the construction s i t e , however, non-unTf'orrnfty of w e t t i n g of the b r i c k s and t h e r e f o r e d i f f e r e n c e s

in

s u c t i o n of the b r f c k s

would l i k e l y occur, A l s o

in

some i n s t a n c e s

it

may be v e r y u n d e s i r a b l e to e r e c t a w a l l which is r e l a t i v e l y damp, for example,

in

cold

A n i l l u s t r a t i o n of the change

In

" a u c t l a n " w i t h ~ o i s t u r e content o f a b r i c k may be

of

i n t e r e s t , The b r i c k u s e d , a dry-pressed shale of a b s o r p t f o n oxl

24-hour

i m e r s l o n

of

12,8 p e r c e n t , Is repre- s e n t a t i v e of a nurrber or' b r i c k s

of

the same t y p e t e s + e d , ':!hen d r y , its r a t e of a b s o r p t i o n was

106

grams when s e t f i a t s i d e down

in

1,/8

linch o f w a t e r f o r one minute;$, The decrease

in

r a t e of a b s o r p t i o n

w i t h change

in moisture

c o n t e n t is shorn

i n

PTg.

1,

t h e moisture

content b e i n g plotted as a p e r c e n t a g e of t h e dry weight of

the

brick, T h u s ,

for

example, at a m o i s t u r e of about

5

p e r cent the ' ' s ~ c t i o n ' ~

i s

78

grams,

Thus ~ O Tt l 5 s b r i c k

t o

a d j ~ s t the i n i t i a l r a t e of

a b s o r p t i o n t o t h e u p p e r

l i m i t

of 20 grams as s u g g e s t e d

"Jy

A,S,T,Iq. a

m b i m u m

addition

of

water

o f

n e a r l y 10

p e r c e n t o f t h e d r y weight of

the brlck or about h a l f a pound o f r ~ a t e r m u s t ke m a d e ,

Ths i m p o r t a n c e of r a k e a b s o r p t i o n as a m e a s u r e o f 5he s u i t a b Z l i t y of Sricks w i t h r e s p e c t

t o

r e s i s t a n c e o f b r i c k aesonry

to r a f n p e n e t r a t i o n , seems t o be c l e a r l y i n d i c a t e d f r o m a consideration

of some of t h e work on t h i s p r o b l e m whfch h a s been reviewed above, e s p e c i a l l y the werk c f Comer,

Concluding Statemen5

An a t t e m p t has been vade here t o d e s c r i b e one problem of. br2ck masonry construction whfcb has been e x p e r i e n c e d

fn

p a r t s of

Canada and t o r e v i e w some of the werk With has b e e n done, The preblen? of moisture p e n e t r a t i o n o f brick vasonry i n v o l v e s

many

f a c t o r s , , till of' g r e a t i m p o r t a n c e in the f i n a l

r e s u l t ,

Thess I n c l u d e the p r o p e r t i e s and c o ~ p o a i t i o n o f t h e w a t e r i a l s used, p r a c t i c e s in

t h e i r assembly, and desTgn of the s t r u c t u r e which t h e y

form,

Ths f ~ f l u e n c e o f workmm-ship on t h e r e s i a t m-ce t o r a i n p e n e t r a t i o n or

b r E c k m a s o r r y has been

much

d i s c u s s e d in t h e l i t e r a t u r s ; this r e v f e w ,

however, has d e a l t m a i n l y

with the

inf'luence o f t h e p r o p e r t f e s o f t h e masonry ater rials o n r a l n r e s i s t a n c e ,

A l t h o u g h much r e s e a r c h w o r k has been done on t h e e f f e c t s .

of ~ o f s t u r e on %he p e r f o r m a n c e

sf'

c o n s t r u c t i o n m a t e r f a l s , mmy of the prcble-os a r e I ~ c o m p l e t e l y answered,

if at

all. The f u t u r e wcrk o f the Division of U u i l d i n g fiesearch w i f v h r e s p e c t

t~

i n v e s t i g a t 5 o n s o r %he p e r f o r m a n c e o f

masonry

w i l l i n c l u d e t h e f o l l o w i n g , F i e l d s t u d i e s of t h e p e r f o r m a n c e o f masonry

in

r e l a t i o n t o

the

p r o p e r f u i e s of the m a t e r i a l s w i l l be c o n t i n u e d . Some s t u d f e s o f h e e t and

moisture f l o w through masonry and o t h e r wall m a t e r i a l s , u n d e r n a t u r a l conditions of e x p o s u r e and a l s o

in

c o l d rooms, ase now being c e r r i e d

o u t by t h e D i v i s i o n .

It

is e x p e c t e d t h a t s t u b i e s w i l l be undertaken, by m e a n s of t h e microscope, of t;h@ i n t e r f a c i a l bond be tween b r i c k s

and . n o r t a r s , both f o r laboratory-prepared

and

f l e l d samples, A s S t a l e y ( 2 ) h a s g o i n t e d o u t , "The u s e o f " c e m i c r ~ s c c p e p r o v i d e s t h e only s i v l e m e m z whereby the characteristics of t h e bond between brfck and m o r t a r ,

In

existing

~ ~ a l l s ,

c a n be studTed''*

4lc I-Teasurements w e r e made

by

H,R, Me i n c k e , MaterSals S e c t i o n ,

D l v i s l o n

af Su2lding Research,

Si.nce as S r i g h t l y

(1)

has p o i n t s d

out the

decay 3f m a s o n r y

i n a t e r i a l s is,

in

qany c a s e s , i n t i m a t e l y a s s o c i a t e d w i t h

m o i s t w s

p e n e t r a t i o n , it is felt t h a t Sy overcoming

this

problerr: o r

rnoisturs

p e n e t r a t i o n of b r i c l r masonry a considerable

advance will

have been made toward the achievement o f the o p t i r n u . ~ p e r f orrnmce and d u r a b i -

l i t y of b r i c k m a s o m y , R e f e r e n c e s

(I)

B r i g h t l y , H . S , Economic a s p e c t s of masonr2 d e c a y f r o m w a t e r i n g .

A,S.T,M.

PFOC.

~ o l .

31,

Iqjl,

p ,794-721.~0

(2) S t a l e y ,

R,R.

A p e t r o g r a p h i c s t u d y of t h e bcnd between b r i c k and a o r t a r . Zulletin Amarlcan Railway Xngineering Associ-

atdon

V o l ,

39,

KO,

396.

1937.

{ 3 ?

KcBurney,

J-W,

T h e w a t e r absorption and p e n e t r a b f l f t y of b r i c k , A.S.T,T-1,

Proc*

Vol, 2 9 , 1 9 2 9 , P e r r e . a b i l i t y of S r i c k rrlzsomy w a l l s

-

an

hypothesis.

p,711-739.

(4)

Voss, k.r,C, P e r v e a b i l i t y of b r l c k masonry xa2ls

-

an

h y p o t h e s i s , 11,S,T,!?i, f r o c . V a l ,

33,

Part 11,

1?33.,

p.670-6910

( 5 )

Connor, C,C, h e s u l t a n t s e p a r a t i o n cracking between v a r i o u s

m o r t a r s and b r i c k in existing brlck

s t r u c t u r e s ,

P r o c , A,S,T,M, Vol,

34,

P a r t 11,

193.!+,

p.454-47yC

( 6 ) P l l l l l s , E.O. The p e r r n e a 5 i l i t y t o air and to w a t e r c? some building b r i c k s , T r a n s , Cer, Soc, Val,

33

1933-34.

( 7 )

McBurney, J,W, The weathering of s t r u c t u r a l c l a y products

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A r e v i e w , P r o c o A,S,T,P!, V a l ,

31,

1931.

p0745-148.

(81 Cornor,

C.C, F a c t o r s

fn

tEe resistance

of

b r i c k masonry w a l l s t o moisture p e n e t r a t i o n , P r o c . A , S , T , H . VoE,

I?@=

F I G .

1

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- - f - /LA