Bond strength of masonry joints under freezing and thawing conditions
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Date
1988
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of New Brunswick
Abstract
In o r d e r to examine t h e e f f e c t s of t h e c y c l ic
t e m p e r a t u r e changes on the t e n s i l e and shear bond of
m a s o n r y , test specimens were exposed to a 24-hour
f r e e z e - t h a w c y c l e w h i c h began a t v a r i o u s m o r t a r ages a f t e r
c o n s t r u e t i o n .
A t o t a l o f one h u n d r e d s p e c i m e n s , b o t h c o n c r e te
b l o c k s and c l a y b r i c k s , were t e s t e d i n t e n s i o n . I n a d d i t i o n ,
f i f t y c o n c r e t e - b l o c k specimens were t e s t e d i n s h e a r . Seven
g r o u p s were e x p o s e d t o a f r e e z i n g c y c l e a t d i f f e r e n t m o r t ar
a g e s , and t h e n c u r e d f o r 7 d a y s b e f o r e t e s t i n g . T h r e e g r o u ps
w e r e c u r e d f i r s t f o r 7 days under d i f f e r e n t e n v i r o n m e n ts
p r i o r to t h e f r e e z i n g c y c l e and t h e n t e s t e d.
The maximum t e n s i l e and shear bond f o r c o n c r e te
b l o c k s o c c u r r e d when f r e e z i n g took p l a c e 8 h o u r s a f t er
c o n s t r u c t i o n ; however, f o r t h e c l a y b r i c k s , t h e h i g h e st
t e n s i l e bond s t r e n g t h o c c u r r e d when f r e e z i n g t o o k p l a ce
i m m e d i a t e l y a f t e r c o n s t r u c t i o n . For t h e s p e c i m e n s w h i c h were
c u r e d b e f o r e f r e e z i n g , t h e h i g h e s t bond was e x h i b i t e d i n t h e
c a s e o f t h e 100% humid e n v i r o n m e n t , and t h e l o w e s t was f o r
t h e case of c o n t i n u o u s f r e e z i n g e n v i r o n m e n t . R e s u l ts
i n d i c a t e d t h a t e a r l y p r o t e c t i o n of c o n c r e t e b l o c k s from
f r e e z i n g i s e x t r e m e l y i m p o r t a n t f o r t h e d e v e l o p m e n t o f h i gh
bond s t r e n g t h s . On the o t h e r hand, i n t h e case o f c l ay
b r i c k s , p r o t e c t i o n was found t o be more e s s e n t i a l a t l a t er
m o r t a r ages.