Small brick panel tests at Ottawa: apparatus and techniques for study of bond strength

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Small brick panel tests at Ottawa: apparatus and techniques for study of bond strength

NATIONAL RESEARCH C O U N C I L O F CANADA D I V I S I O N O F B U I L D I N G RESEARCH

SMALL

B R I C K P A I W L T E S T S A T OTTAWA

APPARATUS AND T E C H N I Q U E S FOR S T U D Y O F BOND S T R E N G T H

by P.T. H o d g i n s R e p o r t No.

175

of t h e D i v i s i o n of B u i l d i n g R e s e a r a h O t t a w a M a r c h

1959

PREFACE The D i v i s i o n i s engaged i n a n e x t e n s i v e s t u d y of b r i c k masonry performance, I n i t i a l l y , a t t e n t i o n i s b e i n g d i r e c t e d t o t h e f a c t o r s t h a t a f f e c t r a i n p e n e t r a t i o n and bond s t r e n g t h of masonry. The l a r g e p a n e l l e a k a g e a p p a r a t u s developed by t h e D i v i s i o n h a s a l r e a d y been des- c r i b e d (DBR I n t e r n a l Report 1 6 0 ) , Much u s e i s now b e i n g made of a s m a l l p a n e l a p p a r a t u s f o r l e a k a g e s t u d i e s . P r e l i m i n a r y s t u d i e s a r e r e p o r t e d i n DBR I n t e r n a l Report 108. S i n c e bond and r e s i s t a n c e t o r a i n p e n e t r a t i o n a r e r e l a t e d , it i s d e s i r a b l e t o be a b l e t o t e s t f o r bond s t r e n g t h on t h e same s m a l l p a n e l s u s e d i n l e a k a g e t e s t s , The a p p a r a t u s and t e c h n i q u e s u s e d i n s u c h bond a t r e n g t h t e s t s a t Ottawa, t o g e t h e r w i t h some of the p r e l i m i n a r y r e s u l t s a r e now r e p o r t e d . A s i m i l a r program of masonry r e s e a r c h , o l o s e l y c o r r e l a t e d w i t h t h e work a t Ottawa, i a b e i n g c a r r i e d o u t a t t h e A t l a n t i c R e g i o n a l S t a t i o n of t h e D i v i s i o n a t H a l i f a x . Ottawa March

1959

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

SMALL B R I C K PANEL TESTS AT OTTAWA

APPARATUS AND TECHNIQUES FOR

STUDY

OF BOND STRENGTH

P.T. Hodgins

I n e a r l y

1958

a program of bond s t r e n g t h measurements of Canadian brickwork was begun by t h e D i v i s i o n of B u i l d i n g Research of t h e N a t i o n a l Researoh Council. I n some r e s p e o t a t h e new program f o l l o w e d the l e a d of o t h e r o r g a n i z a t i o n s t h a t had a a r r i e d o u t

i n v e s t i g a t i o n s i n t h e b r i c k masonry f i e l d , b u t t h e p r o c e d u r e s and equipment adopted were meant s p e c i f i c a l l y t o t i e i n w i t h t h e

D i v i s i o n ' s e s t a b l i s h e d s t u d i e s of masonry m o i s t u r e p e n e t r a t i o n . By t h i s means i t was p o s s i b l e t o measure the bond s t r e n g t h s of j o i n t s whose l e a k a g e c h a r a c t e r i s t i c s had p r e v i o u s l y been i n v e s t i - g a t e d , and much v a l u a b l e i n f o r m a t i o n h a s t h u s been gained.

A s m a l l p a n e l c o n s i s t i n g of f i v e b r i c k s i n s t a c k bond, (i.e., v e r t i o a l a l i g n m e n t ) , and f o u r m o r t a r j o i n t s had j u s t been adopted a s t h e "standard'! specimen f o r s t u d i e s o f c e r t a i n a s p e o t a

of leakage of brickwork, I n such s t u d i e s a s m a l l p a n e l was more a p p r o p r i a t e than t h e f o r m e r l y used " w a l l e t t e n c o n t a i n i n g s e v e r a l

s c o r e s of b r i c k s assembled b y a b r i c k l a y e r , A convenient a p p a r a t u s c o u l d e a s i l y be designed t o accommodate suoh a s m a l l p a n e l and t o b r e a k i t s j o i n t s one by one, measuring t h e u l t i m a t e s t r e n g t h of each. The most u s e f u l advantage was t h a t t h e new s t a n d a r d p a n e l s i z e p e r m i t t e d t h e r e a d y s a l v a g e and t e s t i n g , b o t h f o r m o i s t u r e p e n e t r a t i o n and bond s t r e n g t h c h a r a o t e r i s t i o s , of brickwork of a c t u a l b u i l d i n g s under d e m o l i t i o n . I n such c a s e s , rough s l a b s of masonry need o n l y be o u t t o t h e s t a n d a r d p a n e l s i z e by means of a diamond saw, and t h e n t r e a t e d i n t h e s t a n d a r d i z e d way.

Appara t u a f o r Mea s u r i n g Bond S t r e n g t h

The d e s i g n of t h e bond s t r e n g t h t e s t a p p a r a t u s had t o be based upon t h e h o r i z o n t a 1 dimens i o n s of common Canadian b r i c k s

(about

8 3/8

i n . by

4

In. maximum) and a p a n e l h e i g h t of about

4

i n . R e s u l t s p u b l i s h e d by o t h e r i n v e s t i g a t o r s i n d i c a t e d t h a t t h e l o a d o a p a a i t y of' t h e equipment r e q u i r e d t o b r e a k t h e s t r o n g e r m o r t a r j o i n t s would be a p p r o x i m a t e l y 100 l b p e r square i n a h of

j o i n t a r e a , o r a b o u t 3000 l b t o t a l l o a d f o r j o i n t s of the t y p e

i n

Three s t y l e s of bond s t r e n g t h t e s t a p p a r a t u s have beon designed t o d a t e ; t h e one used c h i e f l y i s shown i n F i g , 1. T h i s

a p p a r a t u s g r i p s two a d j o i n i n g b r i c k s and a p p l i e s and measures t h e s t r a i g h t t e n s i l e f o r c e n e c e s s a r y t o break t h e i n t e r v e n i n g

j o i n t ,

The t h r e e s t e p s i n the procedure used f o r mounting samples f o r t e s t a r e shovm i n Fig. 2

.

A simple j i g c o n s i s t i n g of a s m a l l r e c t a n g u l a r s h e a t of plywood w i t h b l o c k i n g a l o n g two o p p o s i t e edges i s p l a c e d on a t a b l e and t h e masonry panel i s

placed upon

i t ,

between the blocks. A clamping frame i s t h e n f i t t e d over t h e t o p of t h e p a n e l and s l i p p e d down t o r e s t upon t h e blocking, t h u s surrounding t h e lowest b r i c k a t i t s mid- h e i g h t . S t r i p s of l/8-inch b i r c h plywood, o r of t h i c k s t i f f

l e a t h e r a r e i n t e r p o s e d a s f i l l e r s whenever p o s s i b l e between t h e clamping frame and t h e b r i c k . The frame i s c e n t r e d and t h e b o l t s a r e t i g h t e n e d uniformly t o g r i p t h e b r i c k s o t h a t it remains

c e n t r e d .

The b o l t s themselves do n o t b e a r a g a i n s t the b r i c k o r t h e f i l l e r s but t r a n s f e r t h e i r clamping f o r c e t o e i g h t D-shaped h a l f - d i s c s w i t h i n t h e frame designed t o swivel s o a s t o conform t o i r r e g u l a r i t i e s i n t h e shape of the b r i c k , I t i s p o s s i b l e , t h e r e - f o r e , t o p r e s e n t r e l a t i v e l y l a r g e , s e l f - a d j u s t i n g , smooth-bearing a r e a s t o t h e y i e l d i n g f i l l e r s . The h a l f - d i s c s appear i n edge view i n s k e t c h no, 1 of Fig. 2.

The b r i c k panel and clamping frame a r e t h e n l i f t e d a s assembled from t h e j i g and s l i d i n t o t h e t e s t i n g machine s o t h a t t h e clamping frame b e a r s d i r e c t l y upon t h e lotver f l a n g e of t h e main frame a s shown i n s k e t c h no, 2, F i g , 2. Next, t h e upper

clamping frame i s f i t t e d over t h e panel, and lowered t o b e a r on t h e upper f l a n g e of t h e main frame. The r e l a t i v e p o s i t i o n s of t h e p a n e l and t h e upper frame may be a d j u s t e d by t h e f o u r l o n g b o l t s i n t h e lower f l a n g e when, f o r example, t h e bottom j o i n t i s found t o be i r r e g u l a r i n t h i c k n e s s . The upper frame i s t h e n clamped t o the second b r i c k i n t h e same way t h a t t h e lower frame was t o t h e f i r s t .

The assembly, which by now c o n s i s t s of a panel of b r i c k s w i t h t h e two clamping frames i n p l a c e , i s r a i s e d by means of t h e t r a v e l of t h e t e s t i n g machine ( t a k i n g c a r e t h a t no s t r e s s i s

p l a c e d on t h e j o i n t s of t h e p a n e l ) u n t i l t h e lower clamping frame b e a r s upon t h e u n d e r s i d e of t h e upper f l a n g e of t h e main frame. The f o u r long b o l t s i n t h e lower f l a n g e a r e extended upward and, when t h e assembly i s c e n t r e d , a r e t i g h t e n e d so t h a t t h e lower clamping frame i s f i x e d f i r m l y t o t h e upper f l a n g e , The two

hooked hanger b a r s a r e t h e n suspended from t h e t o p of t h e t e s t i n g machine by means of a p i v o t e d cross-bar or yoke, and t h e i r lower ends a r e p o s i t i o n e d i n s o c k e t s i n t h e upper clamping frame ( s k e t c h no.

3,

F i g , 2).

The p o s s i b i l i t y of i r r e g u l a r l o a d i n g of t h e mortar j o i n t s i s minimized by t h e many f l e x i b l e j o i n t s b u i l t i n t o t h e a p p a r a t u s , shown i n Fig. 1. Beginning a t the t o p of the t e s t i n g machine, t h e primary hanging r o d i s s e a t e d on t h e machine's s t a t i o n a r y c r o s s h e a d w i t h a smooth s p h e r i c a l c o n t a c t . Next, a t t h e lower end of t h i s r o d comes the yoke; t h i s c o n t a i n s , i n e a c h end, a b a l l - b e a r i n g f r e e t o move i n i t s s o c k e t s b o t h i n t h e c r o s s - b a r and i n t h e hooked hanger b a r s . F i n a l l y , s i m i l a r ball-and-socket j o i n t s a r e provided a t t h e lower ends of the hanger b a r s where t h e s e hook under t h e upper clamping frame.

The p a n e l i s now r e a d y f o r t h e t e s t . The t e s t i n g machine i s t u r n e d on and s e t f o r a t r a v e l r a t e of 0.05 i n c h e s p e r minute, corresponding t o a l o a d i n g r a t e of 1200 pounds p e r minute. Loads a p p l i e d t o t h e j o i n t a r e r e c o r d e d on t h e d i a l of t h e machine. A f t e r f r a c t u r e of t h e j o i n t t h e u l t i m a t e g r o s s l o a d c a r r i e d by t h e j o i n t i s recorded, a s i s t h e t a r e l o a d of dead weight of t h e p a n e l and t e s t i n g a p p a r a t u s . S u b t r a c t i o n y i e l d s t h e maximum n e t l o a d p l a c e d upon t h e j o i n t , i . e e , t h e j o i n t ' s a c t u a l t o t a l s t r e n g t h :

( g r o s s l o a d )

-

( t a r e l o a d )

=

n o t l o a d . The j o i n t t s u n i t s t r e n g t h i s f i n a l l y c a l c u l a t e d i n pounds p e r square i n c h of g r o s s j o i n t a r e a .

A second, q u i t e d i f f e r e n t a p p a r a t u s was made up f o r use a t t h e A t l a n t i c Regional L a b o r a t o r i e s of the D i v i s i o n of B u i l d i n g Research a t H a l i f a x , N.S. These l a b o r a t o r i e s a r e n o t equipped w i t h a u n i v e r s a l t e s t i n g machine and s o a s m a l l p o r t a b l e s e t of equipment c o n s i s t i n g b a s i c a l l y of a l i g h t h y d r a u l i c jack and l o a d gauge, a p a i r of l e v e r s and a p a i r of clamping frames was designed and b u i l t i n Ottawa t o perform t h e H a l i f a x bond s t r e n g t h t e s t s . The a c t i o n of t h i s s m a l l machine was t o pry t h e b r i c k s a p a r t , by a p p l i c a t i o n of a bending couple r a t h e r t h a n t o p l a c e t h e e n t i r e bonded a r e a of the j o i n t s i n u n i f ornl t e n s i o n .

R e s u l t s from t h e use of t h i s machine have proved d i s p r o - p o r t i o n a t e , i n p r a c t i c e , t o t h e r e s u l t s of d i r e c t - t e n s i o n t e s t s on s i m i l a r j o i n t s . The bending method of j o i n t t e s t i n g , t h e r e f o r e , h a s been dropped.

A t h i r d a p p a r a t u s , shown i n Fig.

3,

i s now being used i n H a l i f a x ; i t i s a d i r e c t - t e n s i o n t y p e of machine b u t makes u s e of a h y d r a u l i c jack s i m i l a r t o t h a t used i n t h e second, bending type of a p p a r a t u s f i r s t mentioned. The new equipment c o n s i s t s e s s e n t i a l l y of a p a i r of clamping frames; t h e lower i s r i g i d l y connected t o

t h e base of t h e jack, while t h e upper may be p u l l e d upward by two hanger b a r s when t h e jack i s pumped.

T h i s simple arrangement i s supplemented by a base p l a t e upon which t h e weight of t h e b r i c k p a n e l and t h e t e s t i n g equipment r e s t and i n which two l o n g t h r e a d e d r o d s , equipped w i t h l a r g e n u t s ,

a r e anchored. A f u r t h e r supplementary i t e m i s a j a c k i n g screw c e n t r a l l y l o c a t e d under t h e j a c k ' s base, and d e s i g n e d t o b e a r upon t h e t o p of t h e b r i c k panel.

The f i r s t f u n c t i o n of t h e j a c k i n g screw i s t o a d j u s t v e r i ; j . c a l l y t h e r e l a t i v e p o s i t i o n s of t h e t e s t i n g a p p a r a t u s and t h e b r i c k panel; t h e second i s t o supply, i n c o n j u n c t i o n w i t h

t h e l o n g t h r e a d e d r o d s and t h e i r n u t s , a downward f o r c e on t h e p a n e l s o t h a t a l l i t s m o r t a r j o i n t s my be p l a c e d i n compression. T h i s p r o t e c t s t h e j o i n t s a g a i n s t a c c i d e n t a l breakage when t h e clamping frame b o l t s a r e t i g h t e n e d .

A f t e r t h e clamping f r a m e s have been s e c u r e d i n p l a c e by means of f o u r b o l t s i n e a c h frame b e a r i n g d i r e c t l y upon t h e b r i c k s ,

t h e j a c k i n g screw must be withdrawn t o f r e e t h e topmost j o i n t of t h e p a n e l f o r t e s t i n g . By k e e p i n g t h e t h r e a d e d r o d s t i g h t t h e lower j o i n t s w i l l n o t be d i s t u r b e d a s t h e t e s t p r o c e e d s s i n c e t h e downward f o r c e mentioned p r e v i o u s l y c o n t i n u e s t o be a p p l i e d t o t h e lower p a r t s of t h e p a n e l t h r o u g h t h e b o l t s of the l o w e r clamping frame. The d e s i g n of t h i s a p p a r a t u s r e q u i r e s t h a t , e a c h t i m e a j o i n t i s broken, b o t h t h e clamping f r a m e s must be r e s e t on

p r o g r e s s i v e l y lower b r i c k s . This i s a simple o p e r a t i o n , however, s i n c e u s u a l l y o n l y two b o l t s must be t u r n e d i n e a c h frame. The clamping f r a m e s u s e d have o n l y two b o l t s p e r s i d e i n s t e a d of t h e f o u r p r o v i d e d i n t h e o r i g i n a l a p p a r a t u s f o r u s e i n a t e s t i n g

machine. T h i s arrangement a p p e a r s t o g r i p t h e b r i c k s a t i s f a c t o r i l y , a v o i d s p o s s i b l e d i s t o r t i o n of t h e b r i c k due t o uneven t i g h t e n i n g of a d j a c e n t screws and r e d u c e s t h e a d j u s t m e n t r e q u i r e d i n f i t t i n g t h e f r a m s t o b r i c k s . The four-screw frame, however, c o u l d be s u b s t i t u t e d i f n e c e s s a r y .

P r e p a r a t i o n of Specimens

Before t h e bond s t r e n g t h t e s t i n g program was i n s t i t u t e d , a s t a n d a r d method o f p r e p a r a t i o n and c u r i n g of f i v e - b r i c k m o i s t u r e p e n e t r a t i o n p a n e l s had a l r e a d y been developed, a s d e s c r i b e d i n

DBR I n t e r n a l R e p k No.

160.

T h i s method was adopted and u s e d a l m o s t unchanged t h r o u g h o u t a n i n i t i a l s e r i e s of bond s t r e n g t h

t e s t a , It h a s s i n c e been a l t e r e d o n l y s l i g h t l y f o r the p r e p a r a t i o n of b o t h l e a k a g e p a n e l s and bond s t r e n g t h p a n e l s . T h e flow v a l u e of t h e m o r t a r f o r e a c h j o i n t o f t h e bond s t r e n g t h p a n e l s was r e c o r d e d

Eond S t r e n a t h T e s t R e s u l t s

Although many p a n e l s of b r i c k masonry have been t e s t e d f o r bond s t r e n g t h i n c o n j u n c t i o n w i t h t h e DBR masonry l e a k a g e t e s t i n g program, and w i t h a n i n v e s t i g a t i o n of t h e p r o p e r t i e s of t h e brickwork of a 26-year o l d Ottawa house (DBR I n t e r n a l Rept.

168),

o n l y t h e r e s u l t s of t e s t s made s o l e l y t o s t u d y t h e e f f e c t s of v a r i o u s f a c t o r s upon bond s t r e n g t h v a l u e s w i l l be r e p o r t e d

here. These t e s t s have been made i n t h r e e s e r i e s , ( i ) t o d e t e r m i n e t h e e f f e c t s of c o r t a i n v a r i a b l e s upon t h e b r i c k - m o r t a r bond, ( i i ) , t o d i s c o v e r t h e b e s t method of p r e p a r i n g p a n e l s f o r u s e i n such t e s t s and ( i i i ) t o compare t h e f i r s t and t h i r d t y p e s of t e s t i n g a p p a r a t u s d e s c r i b e d p r e v i o u s l y b

Some d i f f i u u l t i e s were encountered i n t h e f i r s t s e r i e s of t e s t s t o o c c a s i o n the second s e r i e s . A l a r g e p r o p o r t i o n of t h e

j o i n t s broken i n the f i r s t t e s t s y i e l d e d no measurable s t r e n g t h s

a t a l l , which r a i s e d s e r i o u s d o u b t s about t h e u t i l i t y of t h e r e s u l t s , TJnf o r t u n a t e l y , t h e f i r s t warning of t h e s i t u a t i o n came a f t e r two

weeks' c u r i n g time from t h e d a t e of manufacture of the f i r s t of t h e very l o w - s t r e n g t h p a n e l s , The manufacture of s i m i l a r l y d e f e c t i v e p a n e l s had c o n t i n u e d and more f r u i t l e s s t e s t i n g was

t h e r e f o r e n e c e s s a r y b e f o r e t h e f i r s t s e r i e s of t e s t s could be ended, It was hoped t h a t a r e c u r r e n c e of t h i s s i t u a t i o n could be avoided by improving t h e methods of specimen p r e p a r a t i o n .

The d i f f i c u l t y d i d n o t r e s u l t s o l e l y from t h e p r e p a r a t i o n methods, however, The t r o u b l e began w i t h a changeover from a

proven bag of masonry cement t o a new and a p p a r e n t l y i n f e r i o r b a g b I n t h e f i r s t s e t o f t e s t s i t was hoped t o s t u d y t h e e f f e c t s upon bond s t r e n g t h of t h e f o l l o w i n g f a c t o r s :

(1) Flow c h a r a c t e r i s t i c s ( c o n s i s t e n c y ) of t h e m o r t a r , measured a s d e s c r i b e d i n ASTM ~ 1 0 9 - 5 6 , S e c t i o n

9

( 2 ) Brick absorbency o r " s u c t i o n " a s measured by t h e

I n i t i a l R a t e Absorption t e s t s p e c i f i e d

i n

ASTM ~ 6 7 - 5 7

( 3 ) " ~ i m e

f a c t o r " o r t h e time l a p s e between t h e c a s t i n g of t h e mortar bed and t h e bedding of a b r i c k i n i t

(4)

D i f f e r e n c e s between two b r i c k manufacturers1 p r o d u c t s having t h e same i n i t i a l r a t e of a b s o r p t i o n ( I R A ) .

The r e s u l t s o b t a i n e d from t h e s e r i e s of t e s t s c a n be q u i c k l y summarized a s f o l l o w s f o r t h e p a r t i c u l a r m a t e r i a l s and p r o c e d u r e s used. Bond s t r e n g t h i s i n c r e a s e d by:

( i ) i n c r e a s e d m o r t a r f l o w

( i t )

r a p i d assembly of t h e m a t e r i a l s , and

( i i i ) lower b r i c k s u c t i o n s .

Bond s t r e n g t h may be f a i r l y c o n s t a n t , a l l o t h e r t h i n g s being e q u a l , f o r b r i c k s of e q u a l s u c t i o n ( I R A ) r e g a r d l e s s of source. These

c o n c l u s i o n s a r e l a r g e l y based upon v i s u a l o b s e r v a t i o n . I t i s hoped t h a t a new, more s a t i s f a c t o r y s e r i e s of t e s t s y i e l d i . n g r e l i a b l e n u m e r i c a l r e s u l t s may be made soon by way of c o r r o b o r a t i o n .

The f o l l o w i n g i s a t y p i c a l s e t of n u m e r i c a l r e s u l t s f o r t h o s e p a n e l s from which any bond s t r e n g t h v a l u e s o t h e r t h a n z e r o were o b t a i n e d : Panel

2-3.

-

Flow h e l d c o n s t a n t a s f a r a s p o s s i b l e ; time f a c t o r v a r i a b l e ; I R A of b r i c k s o o n s t a n t a t 24g/min/30 s q i n . S t a n d a r d p a n e l c u r i n g : 2 4 hr wrapped i n s h e e t p l a s t i c , 73.4'~; t h e n s t a n d i n g i n a i r a t 50% R.H., 73.4O~ w i t h e d g e s wrapped i n p l a s t i c , t o age

14

days.

J o i n t No. Time F a c t o r Mortar Flow

( s e c )

<%>

Bond S t r e n g t h ( p s i )

While t h e s e r e s u l t s i l l u s t r a t e f a i r l y w e l l t h e e f f e c t of v a r i e d t i m e f a c t o r s , Figs. h a , b, c can be used t o d e m o n s t r a t e v i s i b l y t h e e f f e c t s of a l l t h e f a o t o r s i n v e s t i g a t e d , I n t h e s e t h r e e f i g u r e s t h e b r i c k f a c e s from which t h e m o r t a r p a r t e d (always above t h e m o r t a r b e d s ) a r e shown f o r e a c h j o i n t i n t u r n , f o r e a c h of t h e p a n e l s . The o o n t r a s t of d a r k b r i c k s u r f a c e t o l i g h t m o r t a r p r o v i d e s a p i c t u r e from which i t i s p o s s i b l e t o judge t h e e x t e n t of bond. Only Fig. 4a was n o t made on o r t h o c h r o m a t i o ( r e d - b l i n d )

f i l m t o d a r k e n t h e r e d d i s h b r i c k s .

F i g u r e 4a shows t h r e e p a n e l s made up a s n e a r l y i d e n t i c a l a a p o s s i b l e i n o r d e r t h a t t h e r e p r o d u c i b i l i t y of t h e t e s t s c o u l d be s t u d i e d . I n e a c h p a n e l j o i n t s were l a i d w i t h t i m e f a c t o r s

b r i c k ) of 60,

45,

30 and

15

seconds r e s p o c t i v c l y , f o r t h e f o u r j o i n t s , Con~parj.sons between p a n e l s a l l o w a sbudy of the t e s t s 1 r e p r o d u c i b i l i t y , while comparisons i n a v e r t i c a l d i r e c t i o n show t h e e f f e c t of t h e time f a c t o r i t s e l f ,

F i g u r e hb shows f o u r p a n e l s of which Z - 1 1 and Z - 1 a r e of b r i c k s s i m i l a r i n I R A but from d i f ' f e r e n t m a n u f a c t u r e r s s i t u a t e d i n d i f f e r e n t p a r t s of O n t a r i o . Theso two p a n e l s show o n l y s l i g h t d f f f e r e n c e s i n mortar o o n t a c t a r e a s considering t h a t t h e masonry cement of p a n e l Z - 1 1 was o b t a i n e d froin t h e i n f e r i o r bag mentioned e a r l i e r ,

P a n e l s Z-1, 2-6 and 2-7 show t h e mortar c o n t a c t s o b t a i n e d w i t h b r i c k s having I R A I S of 2hg, 17g and 9g. The j o i n t s of p a n e l 2-7 would have shown b e t t e r c o n t a c t i f t h i s p a n e l had n o t been made w i t h t h e i n f e r i o r masonry cement, I t i s s i g n i f i c a n t t h a t t h e time f a c t o r seems r e l a t i v e l y unimportant f o r p a n e l 2-7; t h e r e l a t i v e l y low s u c t i o n b r i c k s of t h i s p a n e l d i d n o t a l t e r the mortar p r o p e r t i e s t o any e x t e n t d u r i n g t h e 45-3ec v a r i a t i o n i n t h e t i m i n g used,

F i v e p a n e l s made w i t h c o n s t a n t time f a c t o r s a r e shown i n F i g ,

40,

I n t h e s e p a n e l s t h e m o r t a r f l o w was v a r i e d from h i g h

( a b o u t 130%) t o low ( a b o u t 100%) v e r t i c a l l y , and t h e b r i c k I R A was changed h o r i z o n t a l l y , The I R A ' S i n t h e f i v e p a n e l s a r e a a

follows.-

Z-9,

32g; 2-4, 248;

Z-5,

17g; 2-3,

1 6 ~ ;

2-19, 9go P a n e l s 2-4 and

Z-5

were made w i t h tho f i r s t bag of masonry cement used i n t h e t e s t s e r i e s , while p a n e l s 2-8,

Z-9

and Z-10 c o n t a i n e d cement from t h e second ( i n f e r i o r ) bag.

A d r a m a t i c comparison of t b r e s u l t s w i t h . t h e two bags of cement i s a f f o r d e d by p a n e l s

Z-5

and 2-8, These were rnade w i t h b r i c k s of s i m i l a r I R A , a s l i g h t advantage b o i n g given p a n e l 2-8, b u t t h e i n f e r i o r i t y of t h e m o r t a r used f o r

Z-8

shows i n i t s much p o o r e r c o n t a c t a r e a s ,

The e f f e c t of v a r i a t i o n s of I R A on mortar c o n t a c t can be s e e n h o r i z o n t a l l y i n Fig. 4c, i n s p i t e of the obvious s e t b a c k t o mortar c o n t a c t which has o c c u r r e d between p a n e l s

Z-5

and

Z-8,

Comparf sons i n t h e v e r t i c a l d i r e c t i o n show t h a t h i g h e r mortar f l o w c h a r a c t e r i s t i c s a r e b e n e f i c i a l t o bonding throughout t h e I R A range i n v e s t i g a t e d ,

The second s e r i e s of t e s t s was d e s i g n e d t o d i s c o v e r a method of m o r t a r - j o i n t compaction which could be used w i t h confidence t o produce c o n s i s t e n t , r e l a t i v e l y h i g h b o n d - s t r e n g t h v a l u e s ( i n o r d e r t o avoid unbonded j o i n t s and a c c i d e n t a l

t h a t might be expected i n the f i e l d * A 1/2-in, mortar-bed t h i c k n e s s was used throughout t h e s e r i e s so t h a t a 3/8-in, j o i n t t h i c k n e s s could be a t t a i n e d a f t e r some compaction of t h e mortar.

The f o l l o w i n g compaction methods were t r i e d :

(1) A s i n g l e t a p from a 2 - l b weight dropped 1 1/2 i n . ( t h i s was the method used i n the f i r s t s e r i e s of t e s t s i n t h i s r e p o r t ) ,

( 2 ) A s i n g l e t a p from a 4 - l b weight dropped 1 1/2 i n ,

( 3 )

A SO-lb s t e a d y squeeze f o r f i v e seconds, a p p l i e d by a l e a d weight h o i s t e d and lowered by a p u l l e y

system, I n t h i s c a s e a frame h o l d i n g f o u r 3/8-in0 h i g h narrow vanes was used t o c o r r e c t l y space t h e minimum w i d t h of t h e j o i n t ,

Although p r o c e d u r e s i n v o l v i n g two o r more t a p s c o u l d a l s o have been t r i e d and b o t h a t a p and a s t e a d y squeeze c o u l d have

been used t o s i m u l a t e more c l o s e l y t h e b r i c k l a y e r ' s a c t u a l p r a c t i c e , t h e s e methods would have been t o o d i f f i c u l t t o reproduce w i t h

s u f f i c i e n t p r e c i s i o n .

None of t h e t h r e e methods t e s t e d gave any r e a s o n a b l e degree of c o n s i s t e n c y i n b o n d - s t r e n g t h t e s t r e s u l t s ; i n c o n s i s t e n c y seems, i n f a c t , t o be a n i n e v i t a b l e h a z a r d o f r e s e a r c h i n t h i s f i e l d . The second method (4-pound t a p ) gave h i g h e s t - s t r e n g t h j o i n t s , The f i r s t method (2-pound t a p ) y i e l d e d f i v e unbonded o r v e r y weak

j o i n t s i n t h i s s e r i e s , while t h e o t h e r two methods y i e l d e d one each.

On t h e b a s i s of t h e s e o b s e r v a t i o n s i t was d e c i d e d t h a t t h e 4-pound t a p joint-compaction method was t h e most promising of t h o s e t r l e d , T h i s method w j l l t h e r e f o r e be used, a s f a r a s c a n be f o r - seen, i n t h e manufacture of a l l t h e b o n d - s t r e n g t h p a n e l s t o be c o n s t r u c t e d i n f u t u r e a t t h e D i v i s i o n of B u i l d i n g Research l a b o r a - t o r i e s , The t h i r d s e r i e s of b o n d - s t r e n g t h t e s t s c o n s i s t e d of t h e comparison of two s e t s o f t e s t i n g a p p a r a t u s by t h e b r e a k i n g of 22 m o r t a r j o i n t s made a s s i m i l a r a s p o s s i b l e , I n s p i t e of c o n s i d e r a b l e v a r i a t i o n i n t h e t e s t r e s u l t s f o r i n d i v i d u a l j o i n t s , the t h i r d t y p e of a p p a r a t u s d e s c r i b e d e a r l i e r i n t h i s r e p o r t was found e q u a l t o t h e f i r s t , and was adopted f o r u s e a t t h e D i v i s i o n ' s A t l a n t l c Regional S t a t i o n a t H a l i f a x ,

Some i n t e r e s t i n g o b s e r v a t i o n s were made d u r i n g t h i s t h i r d t e s t s e r i e s . Improved and a c c e l e r a t e d h a r d e n i n g of t h e masonry cement m o r t a r j o i n t s was o b t a i n e d by a week's s t o r a g e of t h e t e s t p a n e l s

i n

a c o n c r e t e - c u r i n g room a t 10@

R.He

f o l l o w e d by two d a y s , s t o r a g e a t

SO$

R.H.

The j o i n t s were s t i l l damp a t t h e t i m e of t e s t i n g , and a l m o s t a l l broke s o t h a t t h e m o r t a r bed p a r t e d from t h e b r i c k below upon which t h e bed had been c a s t . T h i s l a s t f a c t c o n t r a d i c t s a l l p r e v i o u s b o n d - s t r e n g t h t e s t s where t h e p a r t i n g almost always o c c u r r e d a t t h e upper j o i n t s u r f a c e . The

i m p r e s s i o n h a s been t h a t a b r i c k p l a c e d upon a m o r t a r bed c a n n o t a c h i e v e a s i n t i m a t e c o n t a c t a s can t h e b r i c k below t h e bed, s i n c e t h e l a t t e r would have p a r t i a l l y d e s i c c a t e d t h e m o r t a r and r e n d e r e d

i t l e s s p l a s t i c .

I n t h i s t e s t s e r i e s t h e r e seemed t o be a f a i r d e g r e e of c o r r e l a t i o n between m o r t a r f l o w and j o i n t bond s t r e n g t h ( small

v a r i a t i o n s i n f l o w b e i n g u n a v o i d a b l e ) ; p o i n t s p l o t t e d on a c h a r t of m o r t a r f l o w v s bond s t r e n g t h were r a t h e r s c a t t e r e d , however. I t w a s e s t i m a t e d t h a t

a

hundred m o r t a r j o i n t s might have t o be t e s t e d t o e x p l o r e f u l l y t h e m o r t a r f l o w

-

bond s t r e n g t h r e l a t i o n -

[Y uj 5

E?

P a k a 0 : La.

F i g u r e 3snd s t r e n q t h a n p a r a t u s used at

E'Brr~~re

4a

Three panels showin.$ e f f e c t of v a r i o u s

factors upon m o r t a r contact

ImT?

I n t e r n a l . 2eno1-t No.

175

Figure

4b

Four p a n e l s shewing d . i f % e r e n c e s in

m o r t a r c s n t a . c t areas

F i g u r e 4c Pive panels mith

constant

-Lime _fac-bors

showing contras%ing mortar c o n t a c t a r e a s