Publisher’s version / Version de l'éditeur:
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la
première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
Internal Report (National Research Council of Canada. Division of Building
Research), 1963-10-01
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
NRC Publications Archive Record / Notice des Archives des publications du CNRC :
https://nrc-publications.canada.ca/eng/view/object/?id=9bca3dd9-21b4-4099-ae1c-3168e867224e https://publications-cnrc.canada.ca/fra/voir/objet/?id=9bca3dd9-21b4-4099-ae1c-3168e867224e
NRC Publications Archive
Archives des publications du CNRC
For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.
https://doi.org/10.4224/20338253
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Adhesion of various plasters to various bases
O'Kelly, B. M.
NATIONAL RESEARCH COUNCIL CANADA
DIVISION O F BUILDING RESEARCH
ADHESION O F VARIOUS PLASTERS TO VARIOUS BASES
by
B . M. O I K e l l y
Internal Report No. 278 of t h e
D i v i s i o n of Building R e s e a r c h
OTTAWA October
1 9 6 3
P R E F A C E
P r o b l e m s involving bond s t r e n g t h of p l a s t e r have a r i s e n a t v a r i o u s t i m e s over a n u m b e r of y e a r s . Some e x p e r i m e n t a l w o r k h a s b e e n c a r r i e d out b y the Division f r o m t i m e t o t i m e in a t t e m p t s t o a n s w e r s p e c i f i c questions. T h e r e s u l t s of t h i s a r e now r e p o r t e d t o r e c o r d s o m e i n f o r m a t i o n on a field of investigation which though of p r a c t i c a l i m p o r
-
t a n c e h a s not always been p a r t i c u l a r l y rewarding.T h e author, a c h e m i s t and a r e s e a r c h officer with the Building M a t e r i a l s Section, was concerned with p l a s t e r i n g m a t e r i a l s f r o m 1952 until h i s d e p a r t u r e in 1960 t o join a n i n d u s t r i a l r e s e a r c h l a b o r a t o r y . T h e s e r e s u l t s of s o m e of h i s w o r k on bond of p l a s t e r w e r e compiled b y h i m but unfortunately r e p o r t i n g of them h a s b e e n delayed.
Ottawa,
October 1963
N. B. Hutcheon, A s s i s t a n t D i r e c t o r
.
CONTENTS ORGANIZATION P a g e DESCRIPTION O F T E S T S T e s t Method (A) T e s t Method ( B )
E X P E R I M E N T A L CONDITIONS AND T E S T RESULTS
Adhesion of 2 1/2:1 V e r m i c u l i t e P l a s t e r t o Gypsum L a t h Adhesion of P u t t y - c o a t t o a 2 1/2:1 V e r m i c u l i t e B a s e -
c o a t s of V a r y i n g A g e s
Adhesion of Unaggr e g a t e d H a r dwall P l a s t e r t o Gypsum L a t h Showing E f f e c t of Cutting T h r o u g h L a t h P a p e r on Bond F o r m e d Adhesion of Unaggregated H a r d w a l l P l a s t e r to V a r i o u s F o r m s of F o a m e d P o l y s t y r e n e a n d t o a S a m p l e of Cor kboar d Adhesion of U n a g g r e g a t e d R e t a r d e d Gypsum P l a s t e r t o F o a m e d P o l y s t y r e n e Adhesion of Sanded ( 1 1/2:1) H a r d w a l l P l a s t e r on F o a m e d P o l y s t y r e n e and C o r k b o a r d Adhesion of P o r t l a n d C e m e n t P l a s t e r t o V a r i o u s F o r m s of F o a m e d P o l y s t y r e n e
V a r i a t i o n of Adhesion t o Gypsum L a t h with V a r i a t i o n i n S a n d z P l a s t e r R a t i o
Adhesion of P u t t y - c o a t
-
V e r m i c u l i t e B a s e -coat S y s t e m with V a r i o u s B a s e s and T r e a t m e n t sAN ACCOUNT O F A T E S T T O ASSESS T H E WORTH O F
A
P L A S T E R BONDLNG AGENT
T e c h n i c a l D e s c r i p t i o n of Bonding Agent D e s c r i p t i o n of T e s t
R e s u l t s
D i s c u s s i o n of R e s u l t s
Effect of Wetting on Bond t o Bonding Agent CONCLUDING REMARKS
ADHESION O F VARIOUS P L A S T E R S T O VARIOUS BASES b y B. M. O I K e l l y It i s t h e p u r p o s e of t h i s r e p o r t t o p r e s e n t i n convenient f o r m , f o r p u r p o s e s of r e f e r e n c e , s o m e i n f o r m a t i o n c o n c e r n i n g t h e bond of v a r i o u s p l a s t e r s t o v a r i o u s b a s e s . 2. ORGANIZATION Although the i n f o r m a t i o n p r o v i d e d h e r e i s i n c o m p l e t e i n t h a t b y n o m e a n s h a v e a l l of t h e c o n v e n t i o n a l b a s e s and p l a s t e r s b e e n c o n s i d e r e d , i t i s b e l i e v e d t h a t t h e r e s u l t s p r e s e n t e d p r o v i d e u s e f u l guidance. T h e r e s u l t s w e r e obtained f r o m d i f f e r e n t p l a s t e r and b a s e a s s e m b l a g e s u s i n g two t e s t i n g t e c h n i q u e s . I n s o f a r a s t h i s i s f e a s i b l e t h e r e s u l t s a r e b r o k e n down u n d e r t h e h e a d i n g s of t h e b a s e s t o which t h e p l a s t e r w a s applied. F u r t h e r o r g a n i z a t i o n of t h e r e s u l t s w a s not p o s s i b l e . It i s hoped t h a t t h e c o m m e n t s m a d e r e g a r d i n g e a c h g r o u p of r e s u l t s w i l l p r e v e n t confusion. 3. DESCRIPTION O F T E S T S 3. 1 T e s t Method ( A ) A s a m p l e of t h e b a s e t o b e t e s t e d ( 1 f t s q ) w a s cut. In a l m o s t a l l c a s e s t h e b a s e w a s r e i n f o r c e d b y n a i l i n g o r gluing i t t o a 1 -ft s q of 3/4-in. plywood. T h e gluing t e c h n i q u e w a s b y f a r t h e m o s t e f f e c t i v e m e t h o d of r e i n f o r c i n g . A 1/4-in. deep d e m o u n t a b l e b r a s s f r a m e
9
1/2 b y9
1/2 in.w a s l a i d on t h e s a m p l e of b a s e . A s u i t a b l e p l a s t e r ( e . g . , p e r l i t e , v e r m i c u l i t e , o r ~ a n d / ~ l a s t e r ) w a s p r e p a r e d and u s e d t o fill t h e mould. T h e p l a s t e r
s u r f a c e w a s t h e n s c r e e d e d off l e v e l u s i n g t h e e d g e s of t h e mould a s g u i d e s . A f t e r c u r i n g f o r 2 4 h r a t 7 0 ° F and c l o s e t o 100 p e r c e n t R . H . , t h e s a m p l e w a s r e m o v e d f r o m t h e m o u l d and allowed t o d r y t o a c o n s t a n t weight a t 7 2 ° F and 50 p e r c e n t R. H. When t h e s a m p l e w a s d r y , a
9
1 / 2 - b y9
1/2-in. s h e e t of 1/8 -in. f o a m r u b b e r w a s glued t o t h e top s u r f a c e of t h e 1/4-in. l a y e r of p l a s t e r t h a t had b e e n applied t o t h e b a s e . A9
1/2- b y9
1/2-in.s h e e t of 3/4-in. plywood w a s , i n t u r n , glued t o t h e top s u r f a c e of t h e 1/8-in. f o a m r u b b e r s h e e t . A s u i t a b l e h a r n e s s w a s a t t a c h e d t o t h e plywood s h e e t b y m e a n s of wood s c r e w s ; the a s s e m b l y w a s t h e n p l a c e d i n a t e s t i n g m a c h i n e and t h e bond d e t e r m i n e d .
It was thought t h a t the u s e of a c o m p a r a t i v e l y l a r g e t e s t a r e a would e n s u r e a r e a l i s t i c m e a s u r e of the bond. In f a c t i t h a s been found that i t i s v i r t u a l l y i m p o s s i b l e t o load t h e s e s a m p l e s evenly and i t is believed t h a t v e r y often f a i l u r e o c c u r s a t a n a r e a w h e r e s t r e s s i s higher than a v e r a g e and that t h i s f a i l u r e i s then propagated a c r o s s the s u r f a c e . In addition t o t h i s l o c a l f a i l u r e effect, i t was found t h a t v e r y often, in addition t o f a i l u r e a t the applied p l a s t e r / l a t h i n t e r f a c e , f a i l u r e or disruption of the c o r e of the l a t h o c c u r r e d . T h i s l a t t e r effect i s believed t o be m o r e i m p o r t a n t than the f o r m e r . T h e s e c o n s i d e r a t i o n s indicate that the a p p a r e n t bond found by Method (A) will b e lower than t h e t r u e bond. R e f e r e n c e t o Method ( B ) would m a k e i t s e e m that Method (A) gives r e s u l t s t h a t a r e about half the t r u e value.
3. 2 T e s t Method ( B )
Usually, a s in Method (A) (and using t h e s a m e m o u l d s ) , s h e e t s of 1/4-in. thick p l a s t e r a r e applied t o the b a s e t o b e t e s t e d . If t h i s i s not convenient, however, i t suffices t o s p r e a d t h e p l a s t e r on t h e b a s e with a t r o w e l s o a s t o produce a s m o o t h - s u r f a c e d l a y e r of p l a s t e r of about 1/4-in. t h i c k n e s s , although any thickness up t o 3/4 in. can be used. T h e s a m p l e s a r e cured and dried a s in Method (A). Again with Method ( B ) i t i s p o s s i b l e t o t e s t the adhesion of p l a s t e r on existing w a l l s and ceilings.
In Method ( B ) a fly-cutter is u s e d t o i s o l a t e a 2-in. d i a m e t e r disk f r o m the p r e p a r e d s a m p l e , wall, or ceiling by cutting a 1/8-in. wide c i r c u l a r groove down into the p l a s t e r t o the b a s e that is u n d e r t e s t . A 2 -in. aluminum d i s k c a r r y i n g a t h r e a d e d stud is then glued t o the i s o l a t e d disk with a suitable adhesive. A p u l l i n g device o p e r a t e d by c o m p r e s s e d g a s (1)
is s c r e w e d t o the t h r e a d e d stud, and the s a m p l e is loaded t o f a i l u r e . F a i l u r e o c c u r s e i t h e r in the applied p l a s t e r / b a s e i n t e r f a c e o r , in t h e c a s e of m a t e r i a l of r e l a t i v e l y low s t r e n g t h , in the top s u r f a c e of the b a s e . T h e only drawback of Method ( B ) is t h a t i t i s a l i t t l e difficult t o cut an a c c u r a t e groove into
the sanded p l a s t e r and i t is s o m e t i m e s difficult t o find a convenient adhesive t h a t w i l l glue t h e aluminum d i s k t o the applied p l a s t e r with a bond g r e a t e r than t h a t between the applied p l a s t e r and i t s b a s e .
T h e r e i s evidence (See Section 4. 1. 3) t h a t t h e bond found in the l a b o r a t o r y will c e r t a i n l y be no higher than t h a t found f o r a c o r r e s p o n d i n g job a s s e m b l a g e .
( 1 ) OIKelly, B. M. P o r t a b l e adhesion t e s t i n g device. Am. Soc. T e s t i n g Mats. Bull.No. 250, D e c e m b e r 1960, p. 32-33. ( R e p r i n t e d a s NRC 6048.)
4. EXPERIMENTAL CONDITIONS AND TEST RESULTS
4. 1 Adhesion of 2 1/2:1 V e r m i c u l i t e P l a s t e r t o Gypsum Lath
4. 1. 1 E x p e r i m e n t a l conditions
F i v e wood f r a m e s w e r e c o n s t r u c t e d and lathed on both f a c e s with gypsum l a t h to give 10 p a n e l s 6 by 8 ft each. One-half-in. s c r e e d s w e r e nailed t o e a c h panel. Over a 2 -day p e r i o d a l l 10 p a n e l s w e r e p l a s t e r e d with a 1/2-in. coat of 2 1/2:1 v e r m i c u l i t e p l a s t e r . T h e p a n e l s w e r e t r e a t e d f u r t h e r ; but t h i s t r e a t m e n t is c o n s i d e r e d in Section 4. 2. Suffice h e r e t o s a y that the f u r t h e r t r e a t m e n t divided the 10 p a n e l s into a t o t a l of 16 s e p a r a t e t e s t a r e a s .
As the panels w e r e being p l a s t e r e d s a m p l e s w e r e r e m o v e d f r o m t i m e t o t i m e and used t o p r e p a r e l a b o r a t o r y t e s t p a n e l s a s d e s c r i b e d i n Section 3. 2.
T h e p a n e l s w e r e allowed t o s e t and d r y in an uncontrolled l a b o r a t o r y a t m o s p h e r e during August and September. E a c h p a n e l i n t u r n w a s then l a i d horizontally a c r o s s two t r e s t l e s , and adhesion d i s k s w e r e i s o l a t e d f r o m each panel with the aid of a suitable f l y - c u t t e r , b y cutting down through t h e p l a s t e r t o (but not into) t h e gypsum lath. Eight t o 10 s a m p l e s f r o m e a c h of the 16 t e s t a r e a s w e r e i s o l a t e d , yielding a t o t a l of 142 s a m p l e s . A t o t a l of 120 s a m p l e s w e r e isolated f r o m t h e s m a l l l a b o r a t o r y p a n e l s . 4. 1. 2 R e s u l t s 4. 1. 2. 1 R e s u l t s f r o m 142 l a r g e - p a n e l t e s t s Bond ( p s i ) Minimum A v e r a g e 24. 8 3 7 . 3 4. 1. 2. 2 R e s u l t s f r o m 120 l a b o r a t o r y - p a n e l t e s t s Maximum 45. 2 Bond ( p s i )
Minimum Average Maximum 21. 5 28. 6 34. 4
4. 1. 3 Discussion of r e s u l t s
T h e group of 142 l a r g e panel t e s t r e s u l t s and the group of 120 l a b o r a t o r y t e s t r e s u l t s w e r e n o r m a l l y distributed. It a p p e a r s f r o m the r e s u l t s t h a t t h e r e i s a difference in the bond f o r m e d i n the l a b o r a t o r y - panel t e s t s and the l a r g e - p a n e l t e s t s . A s t a t i s t i c a l a n a l y s i s (Student's "t" t e s t ) confirmed this. It would b e r a s h t o e x t r a p o l a t e t h e s e findings
t o the extent of supposing that a l l l a b o r a t o r y - s c a l e t e s t s give lower adhesion values than l a r g e - s c a l e o r "job" t e s t s . N e v e r t h e l e s s i t m a y be concluded with son-~e c e r t a i n t y t h a t the l a b o r a t o r y - ( s m a l l ) - p a n e l t e s t is not l i k e l y t o give higher values than a f u l l - s c a l e t e s t .
4.
2 Adhesion of P u t t y - c o a t t o a 2 1/2:1 V e r m i c u l i t e B a s e - c o a t s of Varying Ages 4. 2. 1 E x p e r i m e n t a l conditionsT h e 10 p a n e l s of 2 1/2:1 v e r m i c u l i t e p l a s t e r d e s c r i b e d in Section 4. 1. 1 w e r e used for the t e s t s of putty-coat bond. On t h e day following that on which t h e b a s e -coat p l a s t e r i n g was finished, one of the p a n e l s of b a s e
-
coat p l a s t e r was finished with an (allegedly) 2:l (by volume) l i m e putty: p l a s t e r white -coat. A 2:l white -coat i s not unusual in Quebec P r o v i n c e . In O n t a r i o a 3:l m i x i s c u s t o m a r y . T h e following day a second b a s e - c o a t panel was putty-coated and s o on for 10 consecutive days until a l l 10 p a n e l s w e r e finished. P r i o r t o applying the white -coat or putty-coat s o m e of the p a n e l s w e r e wetted over t h e i r e n t i r e s u r f a c e o r over the l e f t o r r i g h t half of the s u r f a c e . E a c h panel was c o n s i d e r e d to be one t e s t a r e a u n l e s s half of the panel was wetted down and half left d r y , in which c a s e the wetted half w a s one t e s t a r e a and the d r y half a second t e s t a r e a . In t h i s way a t o t a l of 16 t e s t a r e a s w e r e employed. In each t e s t a r e a 20 adhesion disks w e r e isolated using a fly-cutter t o cut through the white-coat until the b a s e - c o a t showed over 80 t o 90 p e r cent of the bottom of the groove being cut. When, in t h e testing of the bond, a portion of the white-coat r e m a i n e d on t h e b a s e - c o a t the t e s t was r e j e c t e d and a second disk i s o l a t e d in the i m m e d i a t e vicinity of the r e j e c t e d t e s t .Analysis of s c r a p i n g s f r o m the 10 p a n e l s showed the composition of the putty-coats t o be a s follows:
P a r t s of Lime-putty (by Volume) t o One Volume of P l a s t e r of P a r i s
P a n e l Number
1A 1B 2A 2B 3A 3B 4A 4B 5A 5B
4. 2. 2 R e s u l t s
R e s u l t s a r e given in T a b l e I . As t h e white -coats w e r e applied
t o b a s e -coats of v a r i o u s a g e s , the r e s u l t s a r e given i n t e r m s of the m a x i m u m , minimum and a v e r a g e bonds f o r m e d t o a b a s e -coat of a p a r t i c u l a r age.
Likewise, a s s o m e of the b a s e - c o a t s w e r e wetted down ( e i t h e r over a l l the s u r f a c e or over half only) the r e s u l t s a r e grouped t o allow the effect of t h i s t r e a t m e n t t o be seen. As s o m e of the bond f a i l u r e s w e r e c l e a n b r e a k s between t h e b a s e - c o a t and the putty-coat, and s o m e w e r e f a i l u r e s in the body of t h e b a s e -coat, a n a u x i l i a r y t a b l e ( T a b l e I B) is given f o r t h e
"clean -break1' f a i l u r e s .
It i s worthy of note t h a t none of the white-coats showed any c r a z i n g or fire-checking, even when wetted with w a t e r .
4.
2. 3 D i s c u s s i o n of r e s u l t sA s t a t i s t i c a l examination of the white-coat bond r e s u l t s i n d i c a t e s t h a t a l l the r e s u l t s belong t o the s a m e s t a t i s t i c a l population. T h e r e is t h u s no e s s e n t i a l difference between a c l e a n - b r e a k and a f a i l u r e in t h e body of the b a s e -coat. It a l s o follows t h a t t h e wetting of t h e b a s e - c o a t p r i o r t o application of the white-coat h a s a negligible effect, and a l s o t h a t the a g e of the b a s e - c o a t when p l a s t e r e d h a s a negligible effect.
T h e f a c t t h a t the a g e of t h e b a s e - c o a t i s unimportant i s quite s u r p r i s i n g s i n c e c u r r e n t job p r a c t i c e is t o r e g a r d t h e a g e of a v e r m i c u l i t e b a s e - c o a t when putty-coated a s of g r e a t i m p o r t a n c e . It m a y be that the composition of the white-coat is of i m p o r t a n c e . F u r t h e r work is obviously needed. F o r the moment, however, i t m a y b e concluded t h a t the a g e of t h e b a s e -coat (up t o 237 h o u r s a t any r a t e ) is not i m p o r t a n t for the white- coat p l a s t e r m i x used.
4.
3 Adhesion of Unaggr egated H a r d w a l l P l a s t e r t o Gypsum Lath Showing E f f e c t of Cutting Through Lath P a p e r on Bond F o r m e dE x p e r i m e n t a l conditions
L a b o r a t o r y s a m p l e s w e r e p r e p a r e d a s d e s c r i b e d i n Section 3. 2
using gypsum l a t h and a m i x t u r e of h a r d w a l l p l a s t e r and w a t e r in t h e r a t i o of 2 : l by weight. T h e 1/4-in. deep b r a s s moulds w e r e used.
In i s o l a t i n g the t e s t d i s k s the f l y - c u t t e r w a s allowed, in s o m e cases, t o cut down through the l a t h p a p e r into t h e c o r e of t h e gypsum lath. T h e r e m a i n d e r of the g r o o v e s extended only t o t h e f a c e of the lath.
4.
3. 2 R e s u l t sNo. of Depth of Groove Bond F o r m e d ( p s i ) D i s k s T e s t e d
-
Minimum A v e r a g e Maximum Groove cut through
l a t h p a p e r 1 1 . 9 19. 1 26. 3
Groove cut t o s u r f a c e
of l a t h p a p e r 23.9 28. 7 32. 5
It i s noteworthy t h a t w h e r e t h e groove extended i n t o t h e l a t h t h e I%ond1' f a i l u r e o c c u r r e d by t e a r i n g out of t h e c o r e of the gypsum lath. W h e r e t h e groove extended t o the s u r f a c e of t h e l a t h p a p e r only, f a i l u r e o c c u r r e d in the l a m i n a t i o n s of the p a p e r .
4.
3. 3 D i s c u s s i o n of r e s u l t sIt i s of i n t e r e s t t o c o m p a r e t h e r e s u l t s of t h e s e v e n " s u r f a c e - c u t " f a i l u r e s with t h o s e r e p o r t e d in Section
4.
1.2. 2. T h e a v e r a g e for t h e l a t t e r was 28.6
psi. T h e p r e s e n c e o r a b s e n c e of v e r m i c u l i t e did not a p p e a r t o have a n y l a r g e - s c a l e effect. T h e r e s u l t s of t h e t e s t s in Section 4. 3. 2 showc l e a r l y t h e i m p o r t a n t p a r t played by t h e l a t h p a p e r i n c o n f e r r i n g t h e n e c e s s a r y p r o p e r t i e s t o gypsum lath.
4.
4
Adhesion of Unaggr egated H a r d w a l l P l a s t e r t o V a r i o u s F o r m s of F o a m e d P o l y s t y r e n e and t o a Sample of C o r k b o a r d4. 1 E x p e r i m e n t a l conditions
Using b r a s s moulds 1/4 in. deep, l a b o r a t o r y s a m p l e s w e r e p r e p a r e d a s d e s c r i b e d in Section 3. 2. After 2 days in conditions of n e a r l y 100 p e r
cent R . H . and 7 0 ° F , a l l s a m p l e s w e r e r e m o v e d and t a k e n out of t h e moulds. T e s t d i s k s w e r e i s o l a t e d u s i n g a f l y - c u t t e r . All c u t s extended into t h e body of the s u b s t r a t e . T h e s a m p l e s of foamed p o l y s t y r e n e w e r e , in a l l c a s e s , 12 by 12 by 1 in. T y p e s A, B and D w e r e c o m p o s e d of s m a l l f o a m e d p o l y s t y r e n e b e a d s a d h e r i n g t o g e t h e r . T y p e C a p p e a r e d t o h a v e been m a n u f a c t u r e d a s a unit. In s o m e c a s e s , t h e t e s t p a n e l s w e r e p r e p a r e d in duplicate and, p r i o r t o i s o l a t i o n of t h e t e s t d i s k s , one p a n e l and a d h e r i n g p l a s t e r w a s
15 minutes. Two in. d i s k s w e r e t h e n i s o l a t e d and t h e adhesion was d e t e r m i n e d .
It should b e noted that one type of p o l y s t y r e n e was t e s t e d twice b e c a u s e a portion of the h a r d w a l l p l a s t e r m i x u s e d f o r the t e s t s in
Section 4. 3 was used t o p r e p a r e adhesion p a n e l s with a s h e e t of type A and f i r e - r e s i s t a n t type B foamed polystyrene.
4. 4. 2 R e s u l t s
R e s u l t s a r e given in T a b l e I
I .
4. 4. 3 Discussion of r e s u l t s
All f a i l u r e s on c o r k b o a r d o r foamed p o l y s t y r e n e involved f a i l u r e e i t h e r a t t h e p l a s t e r / s u b s t r a t e i n t e r f a c e o r in t h e body of t h e s u b s t r a t e . T h e r e a p p e a r e d t o b e no r e l a t i o n between t h e type of f a i l u r e and the bond f o r m e d .
A s t a t i s t i c a l a n a l y s i s of the r e s u l t s yielded the i n f o r m a t i o n that type C foamed p o l y s t y r e n e (both f i r e - r e s i s t a n t and n o n - f i r e - r e s i s t a n t t y p e s ) give a s u p e r i o r bond both b e f o r e and a f t e r vibration. F o r the u n v i b r a t e d s a m p l e s the f i r e - r e s i s t a n t type C gave a g r e a t e r bond than the n o n - f i r e - r e s i s t a n t . After vibration t h e r e was no a p p r e c i a b l e difference between t h e two f o a m s of type C.
A t e n t a t i v e conclusion t o b e drawn f r o m t h e s e t e s t s i s t h a t bond t o f i r e - r e s i s t a n t type C i s somewhat s e n s i t i v e t o vibration, but can a f f o r d t o be s i n c e i t s t a r t s off a t a higher l e v e l than t h e other type. In g e n e r a l , type C h a s a b e t t e r bond than any other type of f o a m e d p o l y s t y r e n e .
4. 5 Adhesion of Unaggregated R e t a r d e d Gypsum P l a s t e r t o F o a m e d P o l y s t y r e n e
4. 5. 1 E x p e r i m e n t a l conditions
Using t h e 1/4-in. deep b r a s s moulds, adhesion s a m p l e s w e r e p r e p a r e d , conditioned, d r i e d and t e s t e d a s d e s c r i b e d in Section 3. 1.
F a i l u r e of the adhesion s a m p l e s a p p e a r e d , in m o s t c a s e s , t o b e initiated a t load s t r e s s concentration points. F o r t h i s r e a s o n the bond found in a l l c a s e s i s believed to b e a m i n i m u m value. T h e r e w e r e a l m o s t a s m a n y p a t t e r n s of f a i l u r e a s t h e r e w e r e s a m p l e s .
T h e t e s t s w e r e c a r r i e d out i n duplicate o r , a t m o s t , i n t r i p l i c a t e , and a l l r e s u l t s obtained a r e given. B a s e s other than type C a r e b e a d -
4.
5.
2
R e s u l t s B a s e (foamed p o l y s t y r e n e )*
T y p e A T y p e B T y p e C T y p e C T y p e D Bond f o r m e d6.86
6.49
3.94
>2.93
3.59
( p s i ){:
6.19
-
-
-
-
A v e r a g e6.
55
5.
83
4.21
2.93t
4.
33*
f i r e - r e s i s t a n t D i s c u s s i o n of r e s u l t s A c o m p a r i s o n of t h e t e s t s r e p o r t e d i n Section4. 4. 2
s h o w s a f a c t o r of about2
t o 3 i n t h e value of bond found i n favour of t h e " s m a l l - s a m p l e " t e s t s . T h i s i s the u s u a l r a t i o . It is believed that t h e r e s u l t s of the l a r g e - s a m p l e t e s t s r e p o r t e d in Section4.
5.
2
a r e m i n i m u m v a l u e s only.4.6
Adhesion of Sanded ( 11/2: 1)
H a r d w a l l P l a s t e r on F o a m e d P o l y s t y r e n e and C o r k b o a r d4.6.
1 E x p e r i m e n t a l conditionsS a m p l e s w e r e p r e p a r e d , conditioned, d r i e d and t e s t e d a s d e s c r i b e d i n Section 3.1. B a s e s , other than t y p e C and c o r k b o a r d , a r e bead-type
foamed polystyrene. All t e s t s w e r e c a r r i e d out i n duplicate.
4.6. 2
R e s u l t s B a s e*
T y p e A T y p e B* T y p e C T y p e C T y p e D C o r k b o a r d Bond f o r m e d4.
50
4. 66
5. 15
2.
57
4. 28
( p s i )2
1.93
5.
15 3.64
4. 66
3.55
3.44
A v e r a g e 1.98
4. 83
4.
15
4. 91
3.06
3.86
*
f i r e - r e s i s t a n t4.6. 3 D i s c u s s i o n of r e s u l t s
T h e low bond value found f o r type A p o l y s t y r e n e i s unaccountable and should be viewed with r e s e r v e . F o r the r e s t , t h e addition of s a n d does not a p p e a r to have had any m a r k e d e f f e c t on t h e bond.
4. 7 Adhesion of P o r t l a n d Cement P l a s t e r t o V a r i o u s F o r m s of F o a m e d P o l y s t y r e n e
4. 7. 1 E x p e r i m e n t a l conditions
T h e t e s t p r o c e d u r e d e s c r i b e d in Section 3. 1 was used. Although a l l the types of p o l y s t y r e n e p r e v i o u s l y t e s t e d w e r e u s e d in t h i s t e s t , s o m e of the s a m p l e s w e r e s o poor that they s e r v e d only t o give a m i n i m u m value for bond. T h e m i x u s e d was (by volume): sand
=
3 p a r t s ; portland c e m e n t ( + l o p e r cent l i m e putty) = 1 p a r t ; w a t e r=
1/5 p a r t . 4. 7. 2 R e s u l t s B a s e T y p e A T y p e B T y p e C T y p eD
All 4. 48 4. 68 3. 70 Bond f o r m e d 4. 47 4.77 ( p s i ) 3. 8 1 Aver a g e>
3.08 4. 39 4.733.
41 4. 7. 3 D i s c u s s i o n of r e s u l t sT h e bond f o r m e d to the p o l y s t y r e n e a p p e a r s t o depend m o r e on the polystyrene than on the p l a s t e r used. C o m p a r e S e c t i o n s 4. 7 . 2 , 4. 6. 2, and 4. 5. 2.
4. 8 Variation of Adhesion t o Gypsum Lath with V a r i a t i o n in S a n d : P l a s t e r R a t i o 4. 8. 1 E x p e r i m e n t a l conditions
A sand conforming t o the r e q u i r e m e n t s of CSA Specification
A. 82. 57 w a s u s e d i n the t e s t s . T h e sand was mixed d r y with p l a s t e r of p a r i s in p r o p o r t i o n s of 1:1, 1:2, 1 :3, 1:4, and 1 :5. S h e e t s of p l a s t e r 1/4 in. t h i c k
a n d
9
1/2 in. s q u a r e w e r e p r e p a r e d a s i n S e c t i o n 3. 2 a n d , when d r y , 2-in. t e s t d i s k s w e r e i s o l a t e d with a f l y - c u t t e r a n d t h e a d h e s i o n w a s d e t e r m i n e d . 4. 8. 2 R e s u l t s R e s u l t s a r e given i n T a b l e111.
4. 8. 3 D i s c u s s i o n of r e s u l t s T h e r e i s a n obvious t e n d e n c y f o r t h e bond f o r m e d t o d e c r e a s e a s t h e s a n d : p l a s t e r r a t i o is i n c r e a s e d . T h i s t e n d e n c y is a l s o m a n i f e s t e d i n t h e n a t u r e of t h e bond f a i l u r e . Up t o a 3 : l r a t i o t h e f a i l u r e is b y d e l a m i n a t i o n of p a p e r . F o r r a t i o s of 4 : l a n d 5 : l t h e t e n a c i t y of t h e bond i s m u c h r e d u c e d s o t h a t t h e f a i l u r e o c c u r s b y a c l e a n s e p a r a t i o n of a p p l i e d p l a s t e r f r o m l a t h p a p e r . 4.9
A d h e s i o n of P u t t y - c o a t-
V e r m i c u l i t e B a s e - c o a t S y s t e m with V a r i o u s B a s e s a n d T r e a t m e n t s 4.9.
1 E x p e r i m e n t a l conditions F i v e wood f r a m e s s i m i l a r t o t h o s e u s e d i n S e c t i o n 4. 1 w e r e c o n s t r u c t e d a n d l a t h e d on b o t h f a c e s t o give 10 t e s t f a c e s e a c h6
b y 8 f t . One s i d e of e a c h p a n e l w a s l a t h e d w i t h g y p s u m l a t h ; t h e o t h e r s i d e w a s p r o v i d e d with one of f i v e d i f f e r e n t b a s e s . T h e b a s e - c o a t of 2 1 / 2 : 1 v e r m i c u l i t e p l a s t e r w a s a p p l i e d t o all f a c e s in 1 day, followed a t d i f f e r e n t t i m e s f o r d i f f e r e n t f a c e s b y t h e a p p l i c a t i o n of t h e p u t t y - c o a t . O n e - h a l f of e a c h t e s t a r e a w a s w e t t e d b e f o r e a p p l i c a t i o n of t h e p u t t y - c o a t ; t h e o t h e r half w a s l e f t d r y . F r a m e s , o r p a n e l s , a r e i d e n t i f i e d b y n u m b e r s 1 t o 5. S i d e A of e a c h p a n e l w a s l a t h e d with g y p s u m l a t h , t h e o t h e r f a c e , d e s i g n a t e d B, c a r r i e d a d i f f e r e n t b a s e . B a s e s f o r l B , 2B, 3B, 4B, a n d 5B w e r e f i b r e - b o a r d , f i r e - r e s i s t a n t ( b l u e ) f o a m e d p o l y s t y r e n e , s t a n d a r d ( w h i t e ) f o a m e d p o l y s t y r e n e , p o l y s t y r e n e b e a d b o a r d , a n d c o r k , r e s p e c t i v e l y . P a n e l s w e r e ~ l a s t e r e d in M a y a n d w e r e l e f t in a l a r g e w e l l - v e n t i l a t e d ( b u t not conditioned) l a b o r a t o r y p r i o r t o t e s t i n g f o r p e r i o d s f r o m 2 t o 3 m o n t h s . A d h e s i o n d i s k s of 2 -in. dia. a n d 25 i n n u m b e r , w e r e t h e n i s o l a t e d , u s i n g t h e p o w e r - o p e r a t e d f l y - c u t t e r on e a c h of t h e 20 d i f f e r e n t t e s t a r e a s . T e n d i s k s w e r e cut t o t h e b o t t o m of t h e p u t t y - c o a t only; t e n w e r e cut t o a p p r o x i m a t e l y half t h e depth of t h e b a s e - c o a t ; i n e a c h c a s e 5 w e r e c u t t o t h e s u r f a c e of t h e p l a s t e r b a s e . T h e s e a r e s u b s e q u e n t l y d e s i g n a t e d as s h a l l o w - cut, d e e p - c u t a n d b a s e - c u t , r e s p e c t i v e l y . T h u s , a t o t a l of 500 s e p a r a t e d i s k s w e r e p r o v i d e d f o r t e s t i n g a c c o r d i n g t o M e t h o d B of S e c t i o n 3. 2.4.
9.
2 R e s u l t s T h e r e s u l t s a r e given in T a b l eIV
in t e r m s of a v e r a g e , m a x i m u m and m i n i m u m v a l u e s obtained f o r e a c h g r o u p of 10 ( o r 5) d i s k s . T h e y a r e g r o u p e d a c c o r d i n g t o p a n e l , b a s e , wetting, a n d depth of c u t , with a g e of b a s e - c o a t a t t i m e of a p p l i c a t i o n of p u t t y - c o a t given. T h e n u m b e r of c l e a n b r e a k s in which t h e p u t t y - c o a t p a r t e d r e l a t i v e l y c l e a n l y f r o m t h e b a s e - c o a t a r e a l s o i n d i c a t e d f o r t h e s h a l l o w - c u t c a s e s . A s u m m a r y of t h e r e s u l t s , giving a v e r a g e s of g r o u p s only, is p r e s e n t e d i n T a b l e V.4.
9.
3 D i s c u s s i o n of r e s u l t s T h e r e s u l t s obtained a r e g e n e r a l l y u n i f o r m , c o n s i d e r i n g t h e n a t u r e of t h e s y s t e m and t h e p o s s i b l e v a r i a t i o n s in v a r i o u s f a c t o r s involved. T h o s e obtained f o r A p a n e l s with gypsum l a t h a r e r e m a r k a b l y c o n s i s t e n t . A s in p r e v i o u s w o r k , n o effect of t h e wetting p r i o r t o a p p l i c a t i o n of p u t t y -coat, o r of t h e i n f l u e n c e of p r i o r d r y i n g of t h e b a s e - c o a t f r o m 1 t o
9
d a y s , i s shown. T h e r e l a t i v e l y s m a l l v a r i a t i o n between s h a l l o w - , d e e p - and b a s e - c u t s f o r A p a n e l s , p a r t i c u l a r l y when c o m p a r e d t o t h o s e f o r B p a n e l s , s u g g e s t s that t h e bond of b a s e -coat t o b a s e , a n d t h e bond between p u t t y and b a s e - c o a t w e r e in g e n e r a l about e q u a l t o t h e i n h e r e n t s t r e n g t h of t h e b a s e - c o a t . T h i s d o e s not t a k e i n t o a c c o u n t p o s s i b l e s t r e s s c o n c e n t r a t i o n e f f e c t s due t o t h e depth a n d s h a r p n e s s of t h e cut, which w a s in a l l c a s e s m a d e with a s q u a r e - end f l y - c u t t e r 1/8 in. wide. ( T h i s w i l l b e t h e s u b j e c t of a n o t h e r r e p o r t . )T h e r e s u l t s f o r B p a n e l s , on b a s e s o t h e r than gypsum l a t h , a r e s o m e w h a t m o r e v a r i a b l e , but t h e u n i f o r m i t y obtained in A p a n e l s s u g g e s t s t h a t t h i s i s r e a l and m u s t t h e r e f o r e b e a t t r i b u t a b l e s o m e h o w t o t h e t y p e s of b a s e s u s e d . As in t h e c a s e of A p a n e l s , t h e r e is l i t t l e r e a s o n t o conclude t h a t p r e w e t t i n g of t h e b a s e - c o a t h a s a n y s i g n i f i c a n t e f f e c t . T h e s e p a n e l s w e r e c o m p l e t e d , h o w e v e r , a f t e r only 2 d a y s of d r y i n g of t h e b a s e -coat. T h e b a s e -cuts in a l l c a s e s showed g r e a t l y r e d u c e d s t r e n g t h s , no doubt r e f l e c t i n g t h e g e n e r a l l y w e a k e r n a t u r e of t h e b a s e m a t e r i a l s o t h e r than gypsum. Deep
c u t s , half -way t h r o u g h t h e b a s e - c o a t , tend t o show r e d u c e d s t r e n g t h s a n d if t h e s e a r e v a l i d , m u s t b e due e i t h e r t o s o m e i n f l u e n c e of t h e b a s e on t h e q u a l i t y of t h e b a s e - c o a t , o r t o a l a c k of s u p p o r t d u r i n g t e s t i n g , t h u s inducing h i g h e r s t r e s s e s f o r a given l o a d a s a r e s u l t of i n c r e a s e d b a s e r e s i l i e n c e . T h e low r e s u l t f o r f i b r e b o a r d could h a v e been due t o i t s high w a t e r a b s o r p t i o n c a p a c i t y which a f f e c t e d t h e bond, o r t o i t s low s t r e n g t h . An examination of t h e b a s e - c u t f a i l u r e s on i t s h o w s f a i l u r e of t h e b o a r d b y d e l a m i n a t i o n in t h i n l a y e r s c l o s e t o t h e s u r f a c e , i n d i c a t i n g t h a t b o a r d s t r e n g t h and not t h e bond w a s t h e l i m i t i n g f a c t o r .
T h e r e would s e e m t o b e s o m e m e r i t in u s i n g t h e t h r e e d e p t h s of cut f o r two-coat s y s t e m s a s a r e g u l a r p r o c e d u r e , s i n c e i t d o e s p r o v i d e s o m e b a s i s f o r judging t h e b a s e - c o a t s t r e n g t h and i t s bond t o t h e b a s e a s well a s t h e p u t t y - c o a t t o b a s e -coat bond.
5.
AN ACCOUNT O F A T E S T T O ASSESS THE WORTH O F A P L A S T E R BONDING AGENT5. 1 'Technical D e s c r i p t i o n of Bonding Agent
T h e l i t e r a t u r e i s s u e d by t h e m a n u f a c t u r e r i n c l u d e s the following d e s c r i p t i o n . "The bonding agent is i n e r t to oxygen, s t a b l e when d r y , v e r m i n - proof, non-toxic, i n c a p a b l e of supporting f l a m e and h a s a t e m p e r a t u r e
r a n g e of f r o m - 3 5 ° F to + 3 0 0 ° F without f a i l u r e of bond. It i s a r e s i n o u s w a t e r e m u l s i o n of b r u s h i n g or s p r a y i n g c o n s i s t e n c y t h a t will bond new b a s e
coat o r finished c o a t of p l a s t e r t o c o n c r e t e , m e t a l , and other s t r u c t u r a l s u r f a c e s . I '
5. 2 D e s c r i p t i o n of T e s t
T h e object of t h e t e s t was t o find out i f t h e bonding agent ( a ) affected n o r m a l bonding p r o p e r t i e s a d v e r s e l y ,
( b ) produced a s a t i s f a c t o r y bond of p l a s t e r t o a s u b s t r a t e t o which the p l a s t e r would n o r m a l l y not a d h e r e s a t i s f a c t o r i l y .
Guided by t h e s e c o n s i d e r a t i o n s i t was decided t o apply a c o a t of t h e bonding agent t o v a r i o u s m a t e r i a l s and apply an unaggregated gypsum p l a s t e r t o t h e s a m p l e s coated with the bonding agent and t o o t h e r s a m p l e s
of the s a m e m a t e r i a l s which had not been coated.
T h e m a t e r i a l s chosen f o r the t e s t w e r e gypsum l a t h , d e n s e c o n c r e t e - b l o c k , an a s b e s t o s c e m e n t b o a r d , a t e m p e r e d c o m p r e s s e d wood- f i b r e b o a r d (rough s i d e ) , and a s h e e t of g l a s s .
A patch of bonding-agent a p p r o x i m a t e l y 1 ft by 10 in. w a s painted on the gypsum l a t h , a s b e s t o s c e m e n t b o a r d , wood-fibre b o a r d , and s h e e t of g l a s s . Half of one s u r f a c e of the c o n c r e t e block was painted with the bonding agent.
After two days, the. v a r i o u s s u b s t r a t e s r e c e i v e d a n application of an unaggregated q u i c k - s e t gypsum p l a s t e r , s p r e a d over t h e s u r f a c e of the s u b s t r a t e u s i n g a t r o w e l , and applied in such a way a s t o c o v e r both painted and unpainted a r e a s . T h e p l a s t e r coat was about 1/4 in. thick.
After four days the p l a s t e r application w a s judged t o b e s u b s t a n t i a l l y dry. Two-in. d i a m e t e r d i s k s w e r e i s o l a t e d f r o m the p l a s t e r s h e e t s u s i n g a f l y - c u t t e r designed f o r the p u r p o s e .
5. 3 R e s u l t s
R e s u l t s a r e p r e s e n t e d in T a b l e V I . T h e l e v e l of a d h e s i o n on s o m e of t h e s u r f a c e s c o a t e d with t h e bonding agent w a s s o high t h a t t h e glue holding t h e a l u m i n u m d i s k s t o t h e t e s t p l a s t e r d i s k f a i l e d t o hold. If, a f t e r r e p e a t e d e f f o r t s , s u c h f a i l u r e continued t o o c c u r , t h e bond is r e p o r t e d a s a m i n i m u m value which, i n f a c t , r e p r e s e n t s t h e a d h e s i o n of t h e glue t o t h e p l a s t e r r a t h e r than of t h e p l a s t e r t o t h e s u b s t r a t e .
5. 4 D i s c u s s i o n of R e s u l t s
T h e i n t e r p r e t a t i o n of t h e r e s u l t s i s c o m p l i c a t e d b y t h e n u m b e r of t i m e s f a i l u r e o c c u r r e d , not a t t h e p l a s t e r / s u b s t r a t e i n t e r f a c e , but in t h e glue. T h e r e s u l t s w i l l b e c o n s i d e r e d in t e r m s of t h e s u b s t r a t e s u s e d .
Gypsum l a t h : F a i l u r e on both c o a t e d and u n c o a t e d l a t h o c c u r r e d i n t h e l a m i n a t i o n of t h e p a p e r c o v e r i n g of t h e l a t h . T h e bonding a g e n t had n o effect. It i s i m p o r t a n t t o note t h a t t h e bond w a s not d e c r e a s e d b y the
bonding agent.
C o n c r e t e block: T h e r e s u l t s show t h a t p l a s t e r a d h e r e s w e l l t o c o n c r e t e block but t h e bond i s s o m e w h a t s e n s i t i v e t o v i b r a t i o n . W h e r e the bonding a g e n t w a s a p p l i e d t h e bond w a s g r e a t l y enhanced, and w a s , i t w a s t e n t a t i v e l y concluded, not a s s e n s i t i v e t o v i b r a t i o n .
A s b e s t o s c e m e n t b o a r d : T h e p l a s t e r bonded s u r p r i s i n g l y w e l l t o t h e b o a r d t h a t w a s not c o a t e d with bonding agent. T h e n u m b e r of glue f a i l u r e s on the b o a r d c o a t e d with bonding agent c o m p l i c a t e s t h e r e s u l t s . It i s believed, h o w e v e r , t h a t t h e r e s u l t s on b o a r d s with bonding a g e n t i n d i c a t e b e t t e r bond t h a n t h o s e on u n t r e a t e d b o a r d s .
Wood f i b r e b o a r d : T h e s e r e s u l t s a r e t h e m o s t e r r a t i c . F r o m t h e m i t c a n only b e concluded t h a t t h e bonding agent did not d e c r e a s e t h e bond f o r m e d , and m a y p e r h a p s have t e n d e d t o e n h a n c e i t .
G l a s s s h e e t : T h i s i s a d r a m a t i c d e m o n s t r a t i o n of t h e a c t i o n of t h e bonding agent. T h e s e r e s u l t s m a k e i t difficult not t o conclude t h a t t h e a c t i o n of t h e bonding a g e n t will b e a f f e c t e d b y t h e s u r f a c e t o which i t i s - -
applied. T h e g l a s s s h e e t did not a f f e c t t h e n a t u r e of t h e bonding a g e n t , a n d a good bond w a s f o r m e d . W h e r e a bond is developed (on bonding a g e n t )
i n f e r i o r t o t h a t developed on t h e g l a s s c o a t e d with bonding a g e n t , i t d o e s not s e e m u n r e a s o n a b l e t o s u p p o s e t h a t t h e s u b s t r a t e in t h e f o r m e r c a s e h a s a d v e r s e l y affected t h e a c t i o n of t h e bonding a g e n t .
In g e n e r a l , t h e c o n c l u s i o n m a y b e d r a w n t h a t t h e bonding agent w i l l not a d v e r s e l y a f f e c t t h e bond f o r m e d t o a given s u b s t r a t e , a n d i n s o m e
c a s e s m a y b e expected t o enhance t h i s bond v e r y m a r k e d l y . No c o n c l u s i o n s can b e drawn r e g a r d i n g t h e d u r a b i l i t y of t h e bond f o r m e d on bonding agent.
5. 5 Effect of Wetting on Bond t o Bonding Agent
5. 5. 1 D e s c r i p t i o n of t e s t
In a n effort t o evaluate t h e s e n s i t i v i t y of t h e bond on t h e bonding agent t o m o i s t u r e , s o m e s a m p l e s ( g l a s s , c e m e n t b o a r d , c o n c r e t e block) w e r e kept o v e r a weekend a t 100 p e r cent R . H . and 7 0 ° F . After r e m o v a l t o t h e l a b o r a t o r y f o r half a day, t h e bond w a s d e t e r m i n e d .
5. 5. 2 R e s u l t s
R e s u l t s a r e given in T a b l e
VI
I .
5. 5. 3 D i s c u s s i o n of r e s u l t s
T h e r e s u l t s a p p e a r to show that a wetting and d r y i n g c y c l e do not n o t i c e a b l y affect t h e bond t o t h e bonding agent.
b e CONCLUDING REMARKS
T h e u s u a l p l a s t e r s y s t e m is a c o m p l e x one f r o m t h e standpoint of bond. Not only i s bond difficult t o m e a s u r e , e v e n by d e s t r u c t i v e m e t h o d s , but t h e r e a r e a g r e a t m a n y v a r i a b l e s involved. T h e m a t e r i a l s t h e m s e l v e s a r e not highly u n i f o r m in quality. T h e s m a l l d i s k m e t h o d m a y b e c r i t i c i z e d quite p r o p e r l y f o r t h e unknown and p r o b a b l y u n r e a l i s t i c s t r e s s p a t t e r n s t h a t a r e induced b y t h e d i s c o n t i n u i t i e s p r o d u c e d b y the cutting n e c e s s a r y f o r p a t c h i s o l a t i o n , and by t h e gluing of a m e t a l d i s k t o a p l a s t e r s u r f a c e having
d i f f e r e n t e l a s t i c p r o p e r t i e s . T h e s t r e n g t h s obtained m u s t b e r e g a r d e d t h e r e f o r e a s s t r e n g t h s t h a t a r e exceeded b y t h e r e a l s y s t e m r a t h e r than a s t r u e s t r e n g t h values. Unfortunately, t h i s m e t h o d m a y not a l w a y s r a n k s y s t e m s in t h e r i g h t o r d e r , b e c a u s e of d i f f e r e n c e s i n b r i t t l e n e s s t h a t m a y in t u r n p r o v i d e d i f f e r e n t r e s p o n s e s t o t h e s t r e s s c o n c e n t r a t i o n s p r o d u c e d b y t h e g e o m e t r y of the i s o l a t e d t e s t disk. D e s p i t e t h e s e d i f f i c u l t i e s , t h e s m a l l d i s k m e t h o d does a p p e a r t o have m e r i t and p r o m i s e s t o b e useful.
It
is a l r e a d y evident f r o m the r e s u l t s which have b e e n p r e s e n t e d t h a t by i t s u s e , s o m e p r o b l e m s f r o m the field c a n b e u s e f u l l y examined.7. ACKNOWLEDGEMENT
The author was ably a s s i s t e d b y
G.
Quenneville who c a r r i e dT A B L E I
( A ) BOND FORMED ( p s i )
Age of B a s e -
B a s e -coat Wetted B a s e -coat Not Wetted coat when
P l a s t e r e d No. of No. of
( h o u r s ) Minimum A v e r a g e M a x i m u m s a m p l e s M i n i m u m A v e r a g e M a x i m u m s a m p l e s
u u u
W
J
q
E-'F . > r e A - G y p e u m L a t h - I day n o t w e t t e d , r h a l l o w - c u t d e e p - c u t b a s e - c u t w e t t e d , s h a l l o w - c u t d e e p - r u t h a a c - c u t P a c e B - F l b r e b o a r d - 2 d a y s not w e t t e d . s h a l l o w - c u t d e e p - c u t b a a e - c u t w e t t e d , ahallrlw - c u t d e e p - c u t b a s e - c u t P a n e l
-
2 F a c p A - C > - p s u m L a t h - 2 d a y s -- n o t w e t t e d , s h a l l o w - c u t d e e p - c u t b ~ s e - r u t w e t t e d , s h a l l o w - c u t d e e p - c u t b d s e -=it1 F a c e B - F a a t n e d k ' * , l y s t y r r n e ( b l u c ) - 2 d a y s n u t w e l t e d , s i ~ a l l o w - c u t d c v p - c u t b a s e - r u t w e t t e d , a h . l l < , w - c u t dcsep - r u t b a a e - r u t F a c e A - G y p s u m l a t h - 7 d a y e r l u l w e t t e d , s h a l l r r w - c u t d r c r > - c u t b a s e - c u t w e t t e d . a h a l l o w - c u t d e e p - c u t b a s e - c u t F a c e D - F o a m e d P o l y s t y r e n e - 2 d a y s n o t w e t t e d , s h a l l o w - c u t d e e p - c u t b a s e - c u t w e t t e d , s h a l l o w - c u t d e c p - c u t b a s e - c u t -- M a x ( p s i ) I p a i ) ( p a l l --*".IN
P a n e l 4 - F a c e A - C y p a t r l n L a t h - H d a y s n u t w e l t e d , a h a l l o w - c u t d e e p - c u t b a s e - c u t w e t t e d , s h a l l o w - c u t d e e p - c u t b n s e - c u t S a m p l e s 10 10 5 10 I 0 5 10 10 5 10 1 0 5 F a c e B - P o l y s t y r e n e B e a d B o a r d - 2 d a y s n o t w e t t e d , s h a l l o w - c u t d e r p - c u t b a a e - c u t w e t t e d , s h a l l o n . - c u t d e u p - c u t b a s e - c u t F a c e A - G y p s u m L a t h - 9 d a y s n o t w e t t e d . s h a l l u w - c u t d e e p - c u t b a s e - c u t w e t t e d , s h a l l o w - c u t d e e p - c u t b a s e - c u t F a c e B - C o r k - L d a y s n o t w e t t e d , e h a l l o w - c u t d e e p - c u t b a s e - c u t w e t t e d , s h a l l o w - c u t d e e p - c u t b a s e - c u t T A B L E [ V M a x I 4 2 38 4 0 38 41 37 37 36 19 39 33 1 9I I
A D H E S I O N IN W H I T E C O A T V E R M I C U L I T E B A S E - C O A T S Y S T E M WI'TH VARIOUS B A S E S A N D T R E A T M E N T SI
A v y ( p s i ) 36. 9 34. 1 36. 0 35. 9 34. D 34. 2 I 3 1 . 3 28.0 1 8 . 0 34. 3 2 5 . 4 1 7 . 4 M i n ( p s i ) 27 31 2 8 32 2 9 32 2 5 2 3 1 7 2 9 1 5 1 5 S a n ' p l e s 10 10 5 I 0 10 5 10 LO 5 10 I 0 5T A B L E
V
SUMMARY O F RESULTS FROM T A B L E
I V
Adhesion R e s u l t s ( p s i ) Age a t
Clean -Br e a k s final
P a n e l B a s e Not wetted Wetted Shallow -Cut
coat
( d a y s ) Shallow Deep B a s e Shallow Deep B a s e N o t w e t t e d wetted
1A 1 Gypsum 36. 7 37. 8 33. 8 40. 7 37. 5 35. 4 7 3 2A 2 Gypsum 31. 8 32. 4 31. 2 31.
8
31. 1 29. 4 4 4 3A 7 Gypsum 39. 3 38. 6 35. 6 3 7 . 7 36. 5 36. 6 6 1 4A 8 Gypsum 36. 9 34. 1 36. 0 35. 9 34. 0 34. 2 7 8 5A 9 Gypsum 30. 9 27. 9 27. 4 31. 4 30. 4 32.6
0 1 1B 2 F i b r e b o a r d 31. 4 27. 6 7 . 2 31. 0 24. 0 5. 8 4 2 2B 2 Blue S t y r o-
f o a m 21. 5 22.9 16, 6 24. 6 21. 3 11.8
6 3 3B 2 S t y r o - f oarn 30. 3 28. 0 14. 4 34. 4 34. 5 14. 8 7 6 4B 2 Bead B o a r d 31. 3 28. 0 18. 0 34. 3 25. 4 17. 4 7 5 5B 2 C o r k 25. 5 19.2 1 1 . 4 19. 6 23. 5 1 1 . 2 0 7TABLE
VI
Bond ( p s i j -
Substrate A B C D E F R e m a r k s
Gypsum lath 35.8 38. 2 36. 5 37.7 36. 5 34. 9 Clean Clean Clean Clean C l e a n C l e a n break b r e a k break break b r e a k b r e a k
- -
Gypsum lath and 37.0 35. 1 31. 3 35. 3 31. 0 36. 2 bonding agent Clean Clean Clean Clean C l e a n C l e a n
b r e a k b r e a k b r e a k b r e a k b r e a k b r e a k
Concrete block See Se e 6a. 2 76. 3 No bond. P o s s i b l y due 33.4 r e m a r k s r e m a r k s Clean C l e a n
-
t o v i b r a t i o n of f l y - c u t t e rb r e a k b r e a k
Concrete block and
>
>
'
**
>
68.2" 105.0** 71.6**
*
*
bonding agent 84. 5
-
-
G l u e f a i l u r e Asbestos cement>
40. 2 52.0 51. 5 38. 750.2**
*
::board Clean Clean Clean C l e a n G l u e f a i l u r e break b r e a k b r e a k b r e a k
>
>
66.8>
*
Asbestos cement
>
,, 10% p l a s t e r l e f t on board and bonding 45.6*' 36.8" Clean 48.7** 69. 8 9 . 2 * s u b s t r a t eagent b r e a k " " ~ l u e f a i l u r e
Wood -fibreboard 21.5 16.5 16. 2 14. 4 13. 4 22. 6 Clean Clean Clean Clean C l e a n C l e a n
break b r e a k b r e a k b r e a k b r e a k b r e a k
Wood fibreboard 21.9 15. 3 26.7 72. 5 *jF1/2 in. wide s e r n i - and bonding agent 81.1** Clean Clean Clean 1 8 . 6 * * C l e a n c i r c u l a r bond l e f t
b r e a k b r e a k b r e a k b r e a k on s u b s t r a t e
Glass sheet No bond No bond No bond No bond No bond No bond
Glass sheet and
3
>
>
>
58.8** 69. 3" 82.
o**
97.3-*
*
T A B L E V I I Bond ( p s i ) S u b s t r a t e A B R e m a r k s G l a s s
