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Publisher’s version / Version de l'éditeur:

Journal of the Canadian Ceramic Society, 30, pp. 15-20, 1962-01-01

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Research on brick masonry by the Division of Building Research of the

National Research Council

Ritchie, T.

https://publications-cnrc.canada.ca/fra/droits

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OIVISION OF BUILDING RESEARCH

DBRiNRC

Publications

CopY

RESEARCH

ON BRICK

MASONRY

BY

THE DIVISION

OF BUILDING

RESEARCH

OF

TTIE NATIONAL

RESEARCH

COUNCIL

BY

A N A L Y Z E D

T. RITCHIE

REPRINTED FROM

JOURNAL OF THE C'ANAOIAN CERAMIC SOCIETY. VOL 30. t 9 6 t , P . t 5 ' 2 0

TECHNICAL PAPER NO. I33 OF 'HE

DIVISION OF BUILDING RESEARCH

OTTAWA

JANUARY 196?

PRICE IO CENTS

, 6 4

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T h i s p u b l i c a t i o n i s b e i n g d i s t r i b u t e d b y t h e D i v i s i o n o f B u i l d i n g R e s e a r c h o f t h e N a t i o n a l R e s e a r c h C o u n c i l . I t s h o u l d n o t b e r e p r o d u c e d i n w h o l e o r i n p a r t , w i t h o u t p e r m i s -s i o n o f t h e o r i g i n a l p u b l i -s h e r . T h e D i v i s i o n w o u l d b e g l a d t o b e o f a s s i s t a n c e i n o b t a i n i n g s u c h p e r r n i s s i o n . P u b l i c a t i o n s o f t h e D i v i s i o n o f B u i l d i n g R e s e a r c h m a y b e o b t a i n e d b y m a i l i n g t h e a p p r o p r i a t e r e r n i t t a n c e , ( a B a n k , E x p r e s s , o r P o s t O f f i c e M c n e y O r d e r o r a c h e q u e r n a d e p a y -a b l e -a t p -a r i n O t t -a w -a , t o t h e R e c e i v e r G e n e r -a l o f C-an-ad-a, c r e d i t N a t i o n a l R e s e a r c h C o u n c i l ) t o t h e N a t i o n a l R e s e a r c h G o u n c i l , O t t a w a . S t a m p s a r e n o t a c c e p t a b l e . A c o u p o n s y s t e r n h a s b e e n i n t r o d u c e d t o r n a k e p a y -ments for publications relatively sirnple. Ccupons are availa b l e i n d e n o r n i n availa t i o n s o f 5 , 2 5 availa n d 5 0 c e n t s , availa n d m availa y b e o b -t a i n e d b y m a k i n g a r e m i -t -t a n c e a s i n d i c a t e d a b o v e . T h e s e c o u p o n s r n a y b e u s e d f o r t h e p u r c h a s e o f a l l N a t i o n a l R e s e a r c h Council publications including specifications of the Canadian G o v e r n m e n t S p e c i f i c a t i o n s B o a r d .

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RESEARCH

OI.I BRICK

IIIASOI{RY

BY THE

DIVISION

OF BUIIDING

RESEARCH

OI THE

NATIONAT

RESEARCH

COU$iCIt

81 T' Rrrcxm*

at Ottawa and the other at the Atlanti search Council, in Halifax, Nova Scotia. .r

t;;;;;;td.mLf. ti-. ft"t'been spent investigating the problems,of eflorescence and moisture penetratio" rio"g iith various" othEr aspicts of the performance of brick m^rolnty. The purp-ose of this paper is to discuss generally these problems.

ErrlonrscrNcr

Efiorescence is a problem that has been studied for- many.years; in the last i0 years probably troi.-tfr^. 100 papers have been written-about it in North i;:;1.; il;;.:-i4;;h-i, kr,'o",n

"6o,it conditions that cause them to torm onth. problem - about the tvpe,of salts

be a cause of the Problem. There are effiorescence which- are relatively sim routine quali'tv check at the plant. In r New York College of Cerimics' sPor Research Foundati,on, have greatly extt effiorescence salts form in bricks during developed by these studies for improv and the drying and burning of the bri being a source of the salts is greatly redu<

Even if the bricks buili into a wall are free of efflorescence-p.-roducing. salts, and m""y bricks made in Canada are in this category, it is. still possible- fo.r ,"".r. .fiorescence to form on them in a wall. The source ot the selts In such

il]**, ofiicer, Butl<lins Matrrlats section, Divisioa of Buildiog Rearch' Nstional Rmarch Council Ottrwa" Graadr

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slirface as the masonf v dfies. This rnovenrent is restricted, horvever, by the s.ater reDellencv of a silicone-treated surface. Inste.rd of the salts depositing on the surfice as in the case of untreated masonfy, evrporation takes phce behind the surfaCe and the salts form there. As a rcsult, the suriace rematns tree Ot effiorescence.

A somewhet difierent use of silicones to ovefcome efflorescence is th* of treating individual bricks before they are used in construction brickwork. For this a;plication a water-soluble silic6ne is generalll' uscd, as opposed to the minerif spirits solution usually employed in tleating-brick *'alls. A similar effect of u'ater-r-epellency however is obtained on the bridi surface.

In the Division's studies of the use of silicones for the control of efllor-escence. test piers constructed of seyeral types of bricks and mortrrs, with ;;;i;;r'siiicon8 treatments have bctn erected on tlte Division's outdoor exposure site in Ottawa. The results of the use of silicone treatments have been favour-"Ut. i" that efforescence which norrnally occurred without the treatrnent, has been sreatlv reduced in severity by the usl of a silicone treatment. These resulis, il;;.:;;"lu;;l;6;udies irraf,e over a relctively short period of time, and an itnport.ht',iu'estiori, which it is hoped the piers mey help to answ'er, -is how i",i" iii. .Atiiir..n"it of the treatmerit wilt last. Another inrportant consideration ;;g;r;l;tih.-

"t" of silicones is the possibility that lhe gro-:vtl of sa_lt crystels Uei;nd ihe treated surface mav cause the surface to be spalled off. It appears that at present the most usefui solution to the problem 6f effiorescence lies in itt. t.t..iion of .fio..t.rnce-free rnaterials rather'than in attempts to control the movement of salt solutions in the masonry. Under certain conditions, hot'ever, the latter course may be necessary.

RalN PrNernnrloN oF Bnrcr lr{asoNnv Probably most bricknrakers at one quently. have been involved in a situat ttteir liict s has leaked in rainstorms. 11 the Division, some of them very large a difficult to account for these failures bt ence behveen the building giving troub

in some parts of Canada to come acros three n'alis, with the fourth, on the "wr such as clap-board to act as a raio-shield.

tces the possibility of leakage problems' ide overhang that acts as an umbrella ls ;ned from t-he poin-t of view of resist-ihatt , similar building t'ithout such a roiecting the wall from

rain-ls has been a severe problern in many t Britain, and the prirblem has led to all to proride protcttion ageinst leekege' rf con..iruction two walls are built, sep-together by metal ties so that the t'all n t"hat penetrates the outer wall drains rf the oitside wall end is let out at the 3

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base of the wall through "weep holes". rVater therefore does not come into contact with the inner wall and it remains dry.

A possible reason for the development of the cavity wall may have been the assumption that there are so many ways in which a wall may become "leaky", that the best solution is to allow leakage to take place but to control its path. It has been customary in mironry construcfion in Canada to rely on the'wall itself for resistance to iain penetration, rather than to use a schemeiuch as the cavity wall, although in re?eot years many architects in Caoada have called for cavity wall construction in their designs.

stance of solid walls to moisture penetrafion. crnaker is the role of bricks in the 6erfornoaoce

rain. If a test wall of brickwork is'subjected to wind pressure, and many tests of this Iaborat6ry studies. it somitimes happens :ks and leak out tbe other side- On'e

im-Another property of the brick, besi portance to the rnoisture resistance of sorption or suction. It is important ber b;it and the morrar. Vheh bricks a belween bricks and rnortar, with the res

interface, which act as channels for the passage of water through the wall. It usually happeos, thereforg that rain penetrites a-wall not through t-he bricks them-selves, nor through the mortar, but at the interface between them.

I{any tests have demonstrated thc sorption of bricks in the performance o rapialy are difficult to bo'nd'with mort such bricks it rapidly loses its moisture stiff and non-plaitic'before the next co bond between-brick and mortar is there Present at the interface. \U7ith bricks t. bonding may also arise; even though ' apparently established between brick ar

broken io service. Bricks that absorb water at a moderate rate are without doubt the rnost suitable for obtaining good bonding with rnortar, and because of the great importance of this proi'eriy to the qu"ality of masonry it is con-sidered -that stahdardization of 6rici sriction to 'a mdderate rangi of values would be very useful.

_properties of mortar also influence significantly the bonding between brick and- mortar, and thus influenc-e tl

same brick used with two different mo

,f a mortar to remain plastic when in more plastic the rnortai remains until re bond. The combination of a brick of water retention value is highly favour-nt brick walls.

:tion of brick masonry have been made Many of the tests hive used bricks of 4

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subsc'gucntl)' becomes rigid. Chaoges accompanied by shrinkage n'hich in?uc, is conipleted a'nd is in iervice its walls

High str_esses.may thus be set up in the opment Ot cracks.

ls, expansion on heating and contractioa

although over a long period of time, cl

rnrv expand, particularly if they have been under burned. The lon.g-ierrn expansion in- service of undcr-burned clay bricks is known to have prdduced serious cracking in buildiogs

Ifovernents in materials are frequently caused by chemical reaction betweeo difrerent components of the materiai or between thi material and the noisture and carbon dioxide in the air. concrete products, for example, on exposure to the air absorb carbon dioxide from it ahd this process is- accompanied by a shrinliage caused by drying. On the other expansion, such as may occur in mortar or rrticles. Some brickrnakers mav be aware n fronr experience with the lroblem of

sional chenges in ,building rnaterials is erstand the* difficulties n'-Uctr arise in of s'alls and decay of the materials. rnt part of the work of the Division of dies'of dimensional chanses of various building materials and studies of othcr factors that affect the?urability and performance of rnaterials.

Sutrtlranl'

: interest of the Division of Buildine Re-;truction. The conrmon troubles of

Fflor-outlined and the important role of the

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irnportant to draw attention to the fact that unsuiiable properties of bricks can be the cause of serious trouble in nrasonry. To elimiaate the brick as a source of some common problems it is considerdd that the brick should be

(1) a "clean" brick; that is, a brick which will not contribute sar.ts of its own for efiorescence,

(2) a nroderate suction brick, to provide optirnurn bonding with mortar, (3) a standard-size brick. free from -warpage oi cracks, and

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