Influence of bricklaying method on the strength and moisture penetration properties of brick masonry

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NATIONAL RESEARCH COUNCIL

CANADA

DIVISION OF _BUILDING RESEARCH

I N F L W C E OF

_BRICKLAYING

~ T H O D ON THE

STRENGTH AND MOISTURE PENETRATION PROPERTIES OF BRICK MASONRY

by

T.

Ritchie

Internal Report

No.

200

o f the

Division

o f Building Researoh

OTTAWA

PREFACE

An extensive program o f l a b o r a t o r y i n v e s t i g a t i o n s i n t o t h e f a c t o r s a f f e c t i n g r a i n p e n e t r a t i o n and bond-strength c h a r a c t e r i s t i c s of b r i c k masonry i s i n progress a t t h e A t l a n t i c Regional S t a t i o n i n Halifax a s w e l l a s i n t h e Ottawa l a b o r a t o r i e s of t h e Division, It h a s been necessary, i n studying t h e e f f e c t s of t h e v a r i o u s f a c t o r s involved, t o develop h i g h l y standard- i z e d techniques f o r making and t e s t i n g t h e small b r i c k and mortar assemblages used. The techniques used i n making and t e s t i n g t h e specimens f o r moisture p e n e t r a t i o n have a l r e a d y been described

i n DBR

Report no, 160. S t u d i e s c a r r i e d out a t Halifax have been described i n Reports No. 161 and 173 and t h e development of a p p a r a t u s and techniques f o r measurement of bond s t r e n g t h a t Ottawa have been described i n Report' No. 175.

!be l a b o r a t o r y techniques developed f o r t h e making of t e s t panels were designed t o i n c o r p o r a t e p e r t i n e n t f e a t u r e s of t h e b r i c l s l a y e r l s techniques as

f a r

as t h e s e were understood a t the time. A n opportunity was a f f o r d e d during

t h e c o n s t r u c t i o n of some masonry t e s t p i e r s f o r t h e c o n s t r u c t i o n by t h e b r i c k l a y e r of some t e s t panels f o r d i r e c t comparison

rmith s i m i l a r p a n e l s made i n the l a b o r a t o r y . The r e s u l t s , which suggest t h a t l a b o r a t o r y techniques used t o d a t e do n o t adequately simulate those of t h e b r i c k l a y e r a r e now r e p o r t e d ,

m e a u t h o r of t h i s r e p o r t , a r e s e a r c h o f f i c e r w i t h t h e Building M a t e r i a l s Section,

i s

r e s p o n s i b l e f o r t h e b r i c k masonry s t u d i e s being o a r r i e d out a t Ottawa.

Ottawa,

IXTLUmCE OF BRICKLAYING MEICHOL) OPlT

THE

SmENGTH

AND

MOIS!lDRE PENETRATION PROPERTIES OF BRICK

I ~ S O M Y

T,

R i t c h i e

Much of t h e l a b o r a t o r y work being done

i n

t h e D i v i s i o n of B u i l d i n g Research, N a t i o n a l Research Council, i n connection w i t h moisture p e n e t r a t i o n end s t r e n g t h of bond of b r i c k masonry has made use of small assemblages of b r i c k and m o r t a r c o n s i s t i n g of f i v e b r i c k s l a i d one above t h e o t h e r with mortar j o i n t s between, m e assemblages a r e c o n s t r u c t e d by a method adapted from t h a t of C.C. Fishburn

(U.S.

N a t i o n a l Bureau of Standards ) f o r de ternlining t h e t e n s i l e s t r e n g t h of bond between b r i c k and m o r t a r by means of orossed-brick

c o u p l e t s .

I n t h e D i v i s i o n ' s work, t h e method of panel c o n s t r u c t i o n c o n s i s t s , i n b r i e f , of mixing a b a t c h of mortar, p l a c i n g it i n a metal mould on a b r i c k and s c r a p i n g off t h e

excess. The mould i s removed, and a f t e r a c e r t a i n time a n o t h e r b r i c k i s s e t on t h e mortar bed and t h e b r i c k i s given a s i n g l e t a p by a hammer dropped on it. The procedure i s r e p e a t e d f o r subsequent mortar j o i n t s ( s e e

D.P.R.

I n t e r n a l ReportlTo. 1 6 0 ) .

E a r l i e r t e s t s i n d i c a t e d t h a t t h e s t r e n g t h of bond and t h e r e s i s t a n c e t o moisture p e n e t r a t i o n of p a n e l s

depended on t h e p r o p e r t i e s of t h e b r i c k and mortar used, on t h e l e n g t h of time t h e mortar bed w a s i n c o n t a c t w i t h t h e b r i c k before t h e second b r i c k was placed on

it,

and on t h e t a p p i n g impact g i v e n t o t h e b r i c k a f t e r

it

had been placed on t h e mortar. No s t u d i e s had been made up t o t h e p r e s e n t , however, t o determine how t h e p r o p e r t i e s of brickwork made by t h i s l a b o r a t o r y method compared w i t 2 1 t h o s e of brickwork

An o p p o r t u n i t y t o compare t h e methods w a s a f f o r d e d d u r i n g t h e c o n s t r u c t i o n of some brickwork p i e r s f o r e f f l o r e s c e n c e s t u d i e s i n t h e f a l l of 1959. lChe p i e r s were c o n s t r u c t e d on t h e Ottawa exposure s i t e of t h e D i v i s i o n by a b r i c k l a y e r w i t h more t h a n 20 y e a r s ' e x p e r i e n c e i n t h e t r a d e . A t t h e same time t h e b r i c k l a y e r was a s k e d t o b u i l d , i n a d d i t i o n , many f i v e - b r i c k assemblages such a s have been u s e d i n t h e l a b o r a t o r y s t u d i e s , u s i n g however h i s normal t e c h n i q u e of p l a c i n g t h e m o r t a r bed and s e t t i n g t h e b r i c k i n it. B r i c k s and m o r t a r o f t h e same t y p e a s h e used were t a k e n t o t h e l a b o r a t o r y a n d assemblages were c o n s t r u c t e d of them by t h e " l a b o r a t o r y " t e c h n i q u e .

The s m a l l p a n e l s were s u b s e q u e n t l y t e s t e d f o r 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 o n (bjr t h e method d e s c r i b e d i n I n t e r n a l Report No. 1 6 0 ) , a n d a f t e r t h e l e a k a g e t e s t were t e s t e d f o r s t r e n g t h of bond i n d i r e c t t e n s i o n (by t h e method d e s c r i b e d i n I n t e r n a l Repor* No. 1 7 5 ) .

BRICKS

Wo t y p e s of b r i c k s mere used: a c l a y a n d s h a l e b r i c k made by t h e e x t r u s i o n method, and a d r y - p r e s s s h a l e briclc. Both t y p e s were r e d - c o l o u r e d and h a d t h r e e c o r e h o l e s . P r o p e r t i e s of t h e b r i c k s a r e shown i n Table I; f i f t e e n b r i c k s of each t y p e were t e s t e d f o r w a t e r a b s o r p t i o n p r o p e r t i e s and f i v e f o r compressive s t r e n g t h . !be maximum a n d minimum v a l u e s o b t a i n e d from e a c h l o t o f b r i c k s a r e shown.

MORTAR

llcvo m o r t a r s were used. One was composed of a masonry cement and sand, i n p r o p o r t i o n s by volume o f one part masonry cement t o t h r e e p a r t s of dry s a n d ; t h e o t h e r w a s

made of p o r t l a n d cement, l i m e and sand, i n p r o p o r t i o n s by volume o f one p a r t cement, one p a r t l i m e and s i x p a r t s of

d r y sand. The l i m e was a d r y h y d r a t e , soaked o v e r n i g h t b e f o r e u s e . The m o r t a r s were mixed i n a m o r t a r t r o u g h on t h e job s i t e by t h e b r i c k l a y e r ' s h e l p e r . Each b a t c h amounted t o approxiniately one c u b i c f o o t , and t h e amount o f w a t e r added was t h a t which produced t h e optimum c o n s i s t e n c y from t h e b r i c k l a y e r t s p o i n t o f view. A s measured by t h e flow t a b l e , t h e m o r t a r b a t c h e s were q u i t e f l u i d , w i t h f l o w i n e x c e s s o f 140 p e r c e n t .

When t h e briclclayer constructed panels on t h e job s i t e , mortar w a s removed from h i s board and taken t o t h e l a b o r a t o r y where a d d i t i o n a l panels were constructed by t h e l a b o r a t o r y technique, using t h e same brick.

In

h i s work on t h e p i e r s , the b r i c k l a y e r v a r i e d t h e ' s p r e a d of t h e mortar bed, depending on t h e type of b r i c k and mortar, up t o a maximum spread f o r f o u r b r i c k s , t h e

l e n g t h of t h e p i e r . The time i n t e r v a l between placing t h e mortar bed on t h e b r i c k s and s e t t i n g t h e n e x t b r i c k s i n it v a r i e d from about 15 seconds t o 2 minutes, Since previous s t u d i e s i n t h e Division had i n d i c a t e d t h a t t h i s time f a c t o r h a s a very important i n f l u e n c e on t h e p r o p e r t i e s of b r i c k masonry, it was decided t o c o n t r o l it i n t h e b r i c k l a y e r r s technique of panel construction. He was permitted t o l a y t h e mortar bed i n h i s u s u a l manner and t o s e t t h e b r i c k i n place a s he u s u a l l y d i d , b u t was allowed t o s e t t h e b r i c k only a t a c e r t a i n time f o l l o v ~ i n g t h e placing of t h e mortar

I

bed ( e i t h e r 2 o r 1. minute).

H i s method of p l a c i n g t h e mortar bed was t o dump a t r o w e l f u l of mortar on t h e b r i c k , i n v e r t t h e trowel s o that it pointed downvrards a t a n a n g l e , and run i t s p o i n t along t h e c e n t r e of t h e mortar t o form a deep f u r r o w . He then s e t t h e b r i c k on t h e mortar and tapped it quickly f i v e o r s i x times w i t h t h e edge of t h e trowel t o bed it. Although t h e b r i c k was l i g h t l y h e l d i n t h e l e f t hand while being

tapped it seemed t h a t t h e b r i c k l a y e r d i d n o t attempt t o

p r e s s it i n t o t h e mortar. Rather he used t h e trowel t o place it. The heaviness of t h e tapping and t h e number of t a p s

d e l i v e r e d v a r i e d with t h e type OF b r i c k and mortar used. Mortar squeezed from t h e j o i n t was c u t by t h e trowel i n an upward motion, and f o r t h i s study t h e j o i n t s were n o t tooled,

LAB

ORATORY TECHNIQUE

The morta.r, a s r e c e i v e d from t h e b r i c k l a y e r t s board, was placed i n a $-inch deep metal mould on t h e b r i c k and remained i n c o n t a c t w i t h it f o r

&

minute o r 1 minute

(corresponding t o t h e time i n t e r v a l used i n t h e b r i c k l a y e r ' s p a n e l s ) u n t i l Yne n e x t b r i c k was placed. The b r i c k was t h e n tapped, ei-bher by a hammer weighing 4 pounds dropped through

1s

inches ("heavy" t a p ) , o r by a hammer of h a l f t h e weight dropped t h e same h e i g h t ( " l i g h t N t a p ) . A l l t h e panels were s t o r e d i n t h e l a b o r a t o r y a t 73OP and

50

per c e n t r e l a t i v e

humidity f o r s e v e r a l weeks u n t i l t e s t e d f o r moisture penetration. After t h i s t e s t , they were d r i e d i n t h e same room f o r about

RESULTS

Test r e s u l t s a r e -tabulated i n Table 11, where tihe second column i n d i c a t e s t h e d e t a i l s of c o n s t r u c t i o n of t h e panels. Panels 1 3 , 14 and 1 5 , f o r example, were made

by t h e b r i c k l a y e r of extruded b r i c k and masonry cement m o r t a r ,

w i t h a l-minute time i n t e r v a l between p l a c i n g t h e mortar on t h e b r i c k and t h e n s e t t i n g t h e n e x t b r i c k on i t , Panels

1 6 , 1 7 and 18 were made i n t h e l a b o r a t o r y of t h e same m a t e r i a l s , u s i n g t h e " l i g h t 1 ' hammer t o t a p t h e b r i c k s i n t o t h e m o r t a r ,

while p a n e l s 25, 26 and 27 were c o n s t z u c t e d u s i n g t h e "heavy" hammer. The t h i r d column l i s t s t h e s t r e n g t h of bond between b r i c k and m o r t a r i n d i r e c t t e n s i o n (pounds p e r square i n c h ) , as t h e average of t h e r e s u l t s obtained f o r t h e j o i n t s of each panel. The f i g u r e i n b r a c k e t s i s t h e average bond s t r e n g t h of a l l t h e j o i n t s t e s t e d o f t h e t h r e e p a n e l s i n each se*.

The l a s t f o u r columns of Table I1 r e f e r t o r e s u l t s of moisture p e n e t r a t i o n t e s t s , The amount of w a t e r which passed through t h e panel i n t h e first hour of t e s t i s shorn, a l o n g

w i t h t h a t which p e n e t r a t e d i n 24 h o u r s (measured i n

m l ) .

m e maximum r a t e of l'eakage of moisture through t h e panel ( m l p e r minute) is shown n e x t , and f i n a l l y , t h e time a f t e r t h e s t a r t of t h e t e s t when dampness was first observed on t h e back of t h e panel.

Comparing t h e " b r i c k l a y e r " and " l a b o r a t o r y " p a n e l s on t h e b a s i s of bond s t r e n g t h i n d i r e c t t e n s i o n ,

i t

may be seen t h a t i n every case t h e average b o n d d r e n g t h of

t h e b r i c k l a y e r - c o n s t r u c t e d p a n e l s exceeded t h a t of t h e l a b o r a t o r y - c o n s t r u c t e d p a n e l s , u s u a l l y by a v e r y wide margin. I n a l l

c a s e s , t o o , t h e average bond s t r e n g t h of t h e p a n e l s c o n s t r u c t - ed u s i n g t h e t a p w a s g r e a t e r t h a n t h a t of t h e p a n e l s tapped by t h e " l i g h t " hammer. The change i n time i n t e r v a l from

4

minute t o 1 minute, which was s t u d i e d only f o r t h e e x t r u d e d b r i c ? and masonry cement mortar, d i d n o t a p p e a r t o have a s i g n i f i c a n t i n f l u e n c e on s t r e n g t h of bond f o r e i t h e r t h e l a b o r a t o r y - c o n s t r u c t e d o r t h e b r i c k l a y e r - c o n s t r u c t e d panels.

In

comparing t h e r e s u l t s of t h e leakage t e s t s it can be seen t h a t most of t h e s e t s of t h r e e p a n e l s produced a n anomalous r e s u l t which makes it d i f f i c u l t t o r e l a t e

d i f f e r e n c e s i n performance t o d i f f e r e n c e s i n c o n s t r u c t i o n methods. I n one case (panel

25)

it was found on breaking t h e panel t h a t a depression a c r o s s one b r i c k ' s bedding s u r f a c e had prevented b r i c k and mortar from coning i n t o c o n t a c t and provided a

It a p p e a r s from -the t e s t r e s u l t s t h a t moisture penetra-tion i s no-t a s dependent on c o n s t r u c t i o n method a s i s s t r e n g t h of bond. The r e s u l t s f o r -the p a n e l s of p r e s s e d b r i c k w i t h 1:1:6 mortar ind-icated a s l i g h t l y b e t t e r moisture

r e s i s t a n c e f o r t h e l a b o r a t o r y paliels t h a n f o r t h e b r i c k l a y e r - c o n s t r u c t e d p a n e l s , altliough t h e d i f f e r e n c e was s l i g h t . The bond s t r e n g t h of t h e lat-l-er p a n e l s , ho~vever, was s u p e r i o r .

P a n e l s of ex-bruded b r i c k mith 1:1:6 m o r t a r

showed no g r e a t d i f f e r e n c e i n moisture p e n e t r a t i o n p r o p e r t i e s betmeen t h e briclclayer-construc%ed and t h e labora-tory-constructed

( "heavyn t a p ) p a n e l s , altlzou@i t h e r e mere max?.red d i f f e r e n c e s

ill bond s t r e i i g t h . P a n e l s made u s i n g t h e " l i g h t " harmer, however,

were c o n s i s t e n t l y l e a k i e r t h a n t h o s e i n which t h e "heavy'" hammer was employed.

The na-ture of t h e b r e a k s i n t b e m o r t a r j o i n t s was q u i t e d i f f e r e n t b e t ~ ~ e e n t h e b r i c k l a y e r t s p a n e l s and t h e

othe:cs. 'This n a s par-Licularly no-kiceable f o r t h e p a n e l s

of extruded b r i c k and masonry cement mor-tar. For l a b o r a t o r y - c o n s t r u c t e d p a n e l s 1 6 t o 1 3 and 22 t o 3 0 , a l l except t-vo of t h e 48 j o i n t s broke c l e a n l y between t h e bottom of t h e b r i c k and t h e t o p of t h e m o r t a r , wit11 v e r y l i t t l e o r no breakage i n t h e mortar. The corresponding p a n e l s made by -t?ne b r i c k - l a y e r , however, c o n s i s t e n t l y broke i n such a way t h a t l a r g e amounts of mortar adhered t o b o t h s u r f a c e s , much 02 t h e

breakage t a k i n g p l a c e i n t h e m o r t a r i t s e l f a s shov~ii i n Pig. 1; h e r e t y p i c a l mortar-brick bonding c o n d i t i o n s a r e i l l u s t r a t e d f o r t h e two t y p e s of p a n e l s , f o r trvo time i n t e r v a l s , and f o r "light" and t a p s . !he b r i c k s a t lower l e f t sllow t h e v o i d i n t h e mortar caused by furrowing of t h e m o r t a r bed.

B r i c k masonry p a n e l s c o n s t r u c t e d by a method p r e f e r r e d by a b r i c k l a y e r and one used i n t h e Divisiont s l a b o r a t o r y work were cor~~pared on t h e b a s i s of m o i s t u r e pene-bration and bond s t r e n g t h p r o p e r t i e s .

I n -the leakage t e s t s laboratory-made p a n e l s g e n e r a l l y performed i n a s i m i l a r manner t o those made by t h e b r i c k l a y e r , b u t anomalous r e s u l t s prevented a t r u e corn- parison.

I n

bond s t r e n g t h t e s t s , ho~lvzver, t h e b r i c k l a y e r r s p a n e l s were i n a l l c a s e s c o n s i d e r a b l y s t r o n g e r t h a n t h o s e made i n t h e l a b o r a t o r y and Yne n a t u r e of t h e break i n bond tvas

The B r i c k l a y e r ' s method of c o n s t r u c t i o n o f tile p a n e l s appeared t o d i f f e r from t h e l a b o r a t o r y method i n tmo

r e s p e c t s , and may a c c o u n t f o r t h e d i f f e r e n c e s

i n

r e s u l t s , I n t h e f i r s t p l a c e , h e s p r e a d a t h i c l r e r , furrowed m o r t a r bed

(3/4

i n c h o r more compared w i t h t h e +-inch bed used i n t h e l a b o r a t o r y method); t h i s probably meant t h a t t h e upper p a r t o f t h e mortar bed l o s t l e s s moisture because of t h e b r i c k ' s s u c t i o n , s o t h a t i n t h e same p e r i o d of c o n t a c t w i t h t h e b r i c k it would be i n a more p l a s t i c s t a t e . I n t h e second p l a c e , t h e b r i c k l a y e r bedded t h e b r i c k i n t h e mortar by g i v i n g it a s e r i e s of s h a r p t a p s w i t h t h e t r o w e l , whereas

i n

t h e l a b o r a t o r y method, a s i n g l e t a p w a s given t o t h e b r i c k .

Since l a b o r a t o r y - c o n s t r u c t e d rnasonq samples should be s i m i l a r i n t h e i r v a r i o u s p r o p e r t i e s t o f i e l d - c o n s t r u c t e d " masonry, f u r t h e r development work should be undertaken i n t h e method of panel assemblage. T h e use of a t h i c k e r , fbrrowed mortar bed and of a t a p p i n g device t o d e l i v e r

a

_{s e r i e s of t a p s t o t h e b r i c k should a l s o be}

i n v e s t i g a t e d and a comparison made of t h e p r o p e r t i e s of b r i c k l a y e r - c o n s - t m c t e d and l a b o r a t o r y - c o n s t r u c t e d p a n e l s ,

FABLE

I

PROPERTIES OF THE BRICKS

Extruded Pressed

b r i c k b r i c k

Suction (grams p e r min p e r maximum 55.4 87.1

30 sq i n . ) minimum 31.1 46.2 Water a b s o r p t i o n (24 h r , p e r maximum 6.9 8

3

c e n t dry w t ) minimum 6.1 6.1 Water a b s o r p t i o n ( 5 h r b o i l , maximum 10.0 10.5 p e r c e n t d r y w t ) minimum

7.6

7.3 Sa-taration c o e f f i c i e n t maximum 0.86 0.84 minimum 0.75 0.76

Compressive s t r e n g t h ( p s i ) maximum LO, 830 6,150

6,460 3,310

TABLE I1

-

RESULTS OF TESTS

Bond S t r e n g t h T o t a l Leakage ( m l ) Maximum Time f o r

7

D e t a i l s D i r e c t Tension Leakage Dampness I

24

(Average 1 ( p s i 1 _Hour First Rate (ml/min ) l o Appear i

--- Hours

u _{ZT'BECl-an ' ~ s o n r y cement alortar}

1

I 1 3 Made by b r i c k l a y e r 51.0 0 16 Very s l i g h t 3 hours \ 14 (1-min. i n t e r v a l ) (3) 47.3 (50.5) 100 4820 4 .O Immediate

I I

1 5 53.1 0 1 8 Very slight 1 5 minutes I

16 Made i n l a b o n t o r y 38.7 0 125 Very s l i g h t 11 minutes 17 (1-min. i n t e r v a l ) 10.8 (23.0) 0 165 Very s l i g h t 11 minutes ,

1 E, ( " l i g h t " t a p ) 25.7 0 41 Very s l i g h t 45 minutes

25 Vade i n l a b o r a t o r y 31.8 365 7912 8.5 Immediate

26 (1-min. i n t e r v a l ) 35.0 (28.1) 0 5 1 Very s l i g h t 65 minutes

27 ("heavy" t a p ) (**%) 13.8 0 617 1 . 0 Immediate

19 Blade by bricklayer 52.1 405 10820 8.0 Immediate

2 C ($-mln. i n t e n e l ) 47.2 (46.5) 0 68 Very s l i g h t 1 hour

2 1 40.3 0 51 Very s l i g h t 18 hours

22 i%de i n l a b o r a t o r y 28.6 0 1 9 Very s l i g h t

la

minutes

23

(i- in.

i n t e r v a l 20.8 (22.5) 177 5410 4.5 3 minute

24 ( light" t a p ) 15.9 0 50 Very s l i g h t 3 minutes

26 Made i n l a b o r a t o r y 25.2 0 7 Very s l i g h t 5 minutes 2 9 (4-min. i n t e r v a l 28,2 (26.8) 0 124 Very s l i g h t 6 m i ~ u t e s

30 ( heavy" t a p ) 26.9 0 56 Very s l i g h t 28 minutes

Extruded Brick and 1 :1:6 mortar

1 Made by b r i c k l a y e r 29.2 0 7 Very s l i g h t 55 minutes

2 (1-min. i n t e r v a l ) 44.0 (36.9) 0 7 Very s l i g h t

13

hours

3 37.5 o 510 1.2 5 minutes 1 0 Yade i n l a b o r a t o r y 16.0 42 3410 3.0 Immediate I 11 (1-min. i n t e r v a l 23.5 (19.6) 260 9300 8.5 Immediate 12 ( " l i g h t " t a p ) 19.3 107 4685 7.0 $ minu*e 7 Made i n l a b o r a t o r y 18.9 0 114 5 1.0 2 minutes e (1-min. i n t e r v a l ) 37.3 (27.4) 0 9 Very s l i g h t 2$ h,.. c.-rs

5 ( "heavy" t a p ) 26.0 C 2 0 Verg s l i g h t 2r hours Pressed Brick and 1:1:6 Mortar

-

45 Made by b r i c k l a y e r 26.1 31 1630 1.3 4 mir;utes 4 4 (3-ffiin. i n t e r v a l 20.1 (19.2) 28 1247 1.5 1 2 minutes 45 13.7 38 2285 1 . 5 6 m i ~ u t e s 4 6 Wde i n l a b o r a t o r y 7.1 2 0 1280 1 . 0 12 minutes 47 (*-mine i n t e r v a l 11.3 ( 7 . 5 ) 1 0 1110 1 . 0 17 minutes 48 ( l i g h t " t a p ) 4.2 1 5 1320 1 . 0 1 5 mirutes 5 2 Made i n l a b o r a t o r y 13.5 11 1245 1 . 0 1 8 n i n u t s s 5 3 ('-min, i n t e r v a l ) 18.6 (14.2) 11 1130 1 . 0 1 7 m i r . ~ - ) c s 54 (

%cavy"

t a p 5.8 24 1460 1 . 0 1 5 minutes -1

( G ) 1-rnin. i n t e r v a l = 1 minute between p l a c i n g mortar on b r i c k then p l a c i n g b r i c k on mortar, I ( ::2L ) "Light " t a p = 2-lb harrner dropped 1$ inches.

FIGURE I COhWARISON OF B O D OF

MORTAR

IPO BRICK FOR BRICKLAYER- AND LABORATORY-CONSTRUC3ZD PANELS