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NATIONAL RESEARCH COUNCIL CANADA
D I V I S I O N O F B U I L D I N G RESEARCH
DECAY O F hlASONRY MORTAR DUE T O SULPHATE S A L T S
by T. R i t c h i e I n t e r n a l R e p o r t No. 276 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 c h O t t a w a J u l y 1963
PREFACE
The s t u d y of t h e d u r a b i l i t y of b u i l d i n g m a t e r i a l s and components i s most i m p o r t a n t b u t a l s o most d i f f i c u l t . The d i f f i c u l t y a r i s e s n o t o n l y because of t h e v a r i e d and
sometimes complex ways i n which t h e environmental o r exposure f a c t o r s may i n t e r a c t w i t h t h e m a t e r i a l s t o cause changes i n d e s i r a b l e p r o p e r t i e s , b u t a l s o because t h e time o v e r which such e f f e c t s a r e of ooncern i s t h e u s e f u l o r s e r v i c e l i f e of t h e m a t e r i a l .
Long-time exposure of m a t e r i a l s i n a c t u a l s e r v i c e o r i n t e s t arrangements s p e c i a l l y d e v i s e d f o r t h e purpose i s t h e r e f o r e a d e s i r a b l e f e a t u r e of many d u r a b i l i t y s t u d i e s . A
number of b r i c k masonry p i e r s were c o n s t r u c t e d f o r long-time outdoor exposure t e s t s a s p a r t of t h e D i v i s i o n ' s program of masonry s t u d i e s . Some of them, a f t e r o n l y 3 y e a r s of
exposure, have developed a n i n t e r e s t i n g form of m o r t a r d e t e r i o r a t i o n which i s now d e s c r i b e d and d i s c u s s e d .
The a u t h o r , a r e s e a r c h o f f i c e r w i t h t h e I n o r g a n i c B u i l d i n g M a t e r i a l s S e c t i o n , i s i n charge of b r i c k masonry
s t u d i e s ,
Ottawa
DECAY OF MASONRY MORTAR DUE TO SULPHATE SALTS
T. R i t c h i e
S e v e r a l brickwork p i e r s were e r e c t e d a t t h e
D i v i s i o n ' s exposure s i t e i n Ottawa i n 1959. F l a k i n g of t h e m o r t a r from t h e j o i n t s of one of t h e p i e r s was observed s h o r t l y a f t e r th;! p i e r was c o n s t r u c t e i . Three y e a r s l a t e r t h e t r o u b l e had p r o g r e s s e d from s l i g h t s u r f a c e s p a l l i n g of t h e m o r t a r t o s e v e r e c r a c k i n g of t h e j o i n t s . llhe same-
m o r t a r was used i n a p i e r b u i l t of a d i f f e r e n t b r i c k b u t it
h a s n o t s u f f e r e d decay, and i t s perforinance i s c o n s i d e r e d s a t i s f a c t o r s . A s t u d s of t h e m a t e r i a l s used. and r e f e r e n c e t o l i t e r a t u i - e on c e r t a i n f a c t o r s a f f e c t i n g t h e d u r a b i l i t y of masonry m a t e r i a l s i n d i c a t e d t h a t -the decay of t h e m o r t a r was caused by t h e m i g r a t i o n of s u l p h a t e s a l t s from t h e b r i c k i n t o t h e - m o r t a r &here t h e i r subsequent c r y s t a l l i z a t i o n e x e r t e d s u f f i c i e n t p r e s s u r e t o cause decay of t h e mortar. PIERS
The p i e r s were e r e c t e d t o s t u d y t h e i n f l u e n c e of t h e p r o p e r t i e s of t h e m a t e r i a l s , and of o t h e r f a c t o r s , on t h e occurrence of e f f l o r e s c e n c e . They were c o n s t r u c t e d of s o l i d brickwork a b o u t 34 i n . wide, 52 i n , h i g h and 12 i n . t h i c k .
A s h e e t of copper f o i l was placed t h r o u g h t h e p i e r , a b o u t 1 2 i n . from t h e b a s e , t o p r e v e n t t h e r i s e of ground w a t e r i n t o t h e brickwork; t h e t o p of t h e briclrwork was covered by copper f o i l on which a c o n c r e t e c a p was s e t .
Two k i n d s of b r i c k s and t h r e e m o r t a r s were used. One of t h e b r i c k s had been made by t h e d r y - p r e s s method, t h e o t h e r by extl-usion. The e x t r u d e d b r i c k was on t h e a v e r a g e lower i n r a t e and amount of w a t e r a b s o r p t i o n and had h i g h e r compressive s t r e n g t h t h a n t h e d r y - p r e s s b r i c k . The p r o p e r t i e s of t h e b r i c k s a r e g i v e n i n Table I. F i f t e e n b r i c k s of each kind 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 ; t h e range i n v a l u e s o b t a i n e d from t h e samples i s l i s t e d i n Table I. Mortars of t h r e e compositions were used: t h e f i r s t was prepared from lime and sand: t h e
-
Asecond from cement, lime and sand; and t h e t h i r d from masonry cement and sand. The s e v e r e c r a c k i n g of m o r t a r j o i n t s d e s c r i b e d p r e v i o u s l y h a s t a k e n p l a c e o n l y i n one of t h e p i e r s of t h e
1ime:sand m o r t a r ; t h e o t h e r p i e r of t h e same m o r t a r b u t d i f f e r e n t b r i c k h a s n o t s u f f e r e d from decay of t h e m o r t a r , PERFORnIANCE OF THE PIERS
The p i e r of t h e d r y - p r e s s b r i c k and 1ime:sand m o r t a r was e r e c t e d on 6 October 1959, while t h a t of t h e
extruded b r i c k and t h e same mortar was e r e c t e d on 14 October. When t h e p i e r s were examined i n Deceinber 1959, it was observed
t h a t f l a k e s of mortar were coming from t h e j o i n t s of t h e p i e r of d r y - p r e s s b r i c k s and t h a t t h e mortar of t h i s p i e r was s o f t i n many p l a c e s and could e a s i l y be scraped w i t h a k n i f e . The mortar of t h e p i e r of t h e extruded b r i c k , however, appeared t o be q u i t e hard and s t r o n g . The s p a l l i n g of t h e mortar j o i n t s of t h e p i e r of dry-press b r i c k s was a g a i n noted i n t h e w i n t e r of 1960-61, b u t it was n o t u n t i l t h e f o l l o ~ i i n g w i n t e r t h a t c r a c k s were observed i n t h e j o i n t s . B y June 1962
( l e s s t h a n t h r e e y e a r s a f t e r t h e p i e r had been c o n s t r u c t e d ) , t h e mortar j o i n t s had become s e v e r e l y cracked. The p i e r o f
t h e extruded b r i c k , however, continued t o perform s a t i s f a c t o r i l y i n t h e same p e r i o d of t i m e , and when examined i n June 1962 t h e r e was no evidence of decay o r d i s t r e s s i n t h e mortar of t h a t p i e r .
The s l i g h t s p a l l i n g of t h e s u r f a c e of t h e mortar o f t h e p i e r of d r y - p r e s s b r i c k s which occurred a t a n e a r l y age i s shown i n t h e photograph of Figure 1. I t s c o n d i t i o n a t a l a t e r age when s e v e r e c r a c k i n g had developed i s shown i n t h e photographs of Figure 2 which were t a k e n i n June 1362. I t i s e v i d e n t t h a t t h e mortar around almost a l l of t h e b r i c k s i n t h e p i e r i s cracked, and t h a t t h e c r a c k i n g has occurred i n a n unusual p a t t e r n . ' k e e x t e n t of t h e l o s s of m o r t a r from t h e s u r f a c e of t h e j o i n t s because of t h e s p a l l i n g a c t i o n i s e v i d e n t from a comparison of F i g u r e s 1 and 2.
The p i e r of t h e extruded b r i c k and lime m o r t a r i s shown i n Figure 3 which was taken i n June 1962. The c o n d i t i o n of t h i s p i e r i s considered good, w i t h no i n d i c a t i o n of t h e s p a l l i n g and c r a c k i n g t h a t a f f e c t e d t h e p i e r of d r y - p r e s s
b r i c k s . The mortar j o i n t s have r e t a i n e d t h e o r i g i n a l concave- t o o l e d s u r f a c e s , a s sho~vn i n t h e c l o s e - u p photograph.
CAUSE OF MORTAR DECAY
The n a t u r e of t h e mortar decay suggested f r o s t
a c t i o n a s t h e cause of f a i l u r e b u t t h i s was r u l e d o u t because of t h e s a t i s f a c t o r y performance of t h e o t h e r p i e r of t h e same mortar. I f f r o s t a c t i o n had been t h e c a u s e , b o t h p i e r s would have been s i m i l a r l y a f f e c t e d ; i n f a c t , t h e p i e r of extruded b r i c k s should hsve been a f f e c t e d f i r s t , because it was b u i l t a t a l a t e r d a t e when t h e weather had t u r n e d c o l d e r . The p i e r of extruded b r i c k s was e r e c t e d 8 days a f t e r t h e p i e r of d r y - p r e s s b r i c k s and t h e d a t e of e r e c t i o n of t h e former p i e r coincided w i t h t h e f i r s t below-freezing temperature of t h e season (14 October: 26OF).
Another cause of decay of masonry m a t e r i a l s b e s i d e s f r o s t a c t i o n i s t h e c r y s t a l l i z a t i o n of s a l t s w i t h i n them, t h e mechanical f o r c e e x e r t e d by t h e c r y s t a l s a s t h e y form
b e i n g s u f f i c i e n t t o d i s r u p t t h e m a t e r i a l s . S e v e r a l c a s e s o f d i s i n t e g r a t i o n of masonry from t h i s c a u s e have b e e n r e p o r t e d . A g e n e r a l d i s c u s s i o n of t h e problem h a s been p r e s e n t e d by Anderegg (1). A p a r t i c u l a r c a s e of s p a l l i n g of b r i c k s i n t h e w a l l of a b u i l d i n g c a u s e d by t h e c r y s t a l l i z a t i o n of c a l c i u m s u l p h a t e h a s been r e p o r t e d by H a r d e s t y ( 2 ) . S i m i l a r damage t o b r i c k s h a s been d e s c r i b e d by B u t t e r w o r t h ( 3 ) ; h e found t h a t magnesium s u l p h a t e o r c a l c i u m s u l p h a t e c o u l d c a u s e s p a l l i n g and d e c a y i f p r e s e n t i n b r i c k s i n s u f f i c i e n t q u a n t i t y . Damage t o m o r t a r by a s a l t c r y s t a l l i z a t i o n p r o c e s s was a l s o d e s c r i b e d by B u t t e r w o r t h ( 3 ) . The damage was a t t r i - b u t e d t o t h e a c t i o n of s o l u t i o n s of c a l c i u m s u l p h a t e i n t h e brickwork which a t t a c k p o r t l a n d cement p r o d u c t s i n t h e m o r t a r ; h y d r a t e d c a l c i u m a l u m i n a t e s a r e t h e r e b y c o n v e r t e d t o c a l c i u m s u l p h o - a l u m i n a t e , t h e change b e i n g accompanied b y c o n s i d e r a b l e e x p a n s i o n which c a u s e s d i s r u p t i o n of t h e m o r t a r . D i s i n t e g r a - t i o n of m o r t a r h a s been a t t r i b u t e d by Connor ( 4 ) t o e f f l o r e s c e n c e c o n t a i n i n g sodium and potassium s u l p h a t e s . H i s s t u d i e s
i n v o l v e d many b u i l d i n g s i n which t h e s u r f a c e of t h e m o r t a r had p r o g r e s s i v e l y s p a l l e d away, p r o d u c i n g deep p i t s i n t h e m o r t a r , t h e a c t i o n r e s u l t i n g from t h e c r y s t a l l i z a t i o n of
s a l t s n e a r t h e s u r f a c e .
It seems c l e a r from t h e s e few r e f e r e n c e s t h a t t h e d e c a y i n t h e m o r t a r of t h e p i e r c a n be e x p l a i n e d by s a l t c r y s t a l l i z a t i o n . A s w i l l be shown t h e b r i c k s used i n t h e p i e r which l a t e r s u f f e r e d from m o r t a r d e c a y c o n t a i n e d con- s i d e r a b l y more s o l u b l e s a l t s t h a n t h o s e i n t h e p i e r of sound m o r t a r , and i n a d d i t i o n , t h e decayed m o r t a r was much h i g h e r i n s u l p h a t e s a l t s t h a n t h e sound m o r t a r . It was t h o u g h t , t h e r e f o r e , t h a t t h e decay of t h e m o r t a r was due t o t h e
m i g r a t i o n of s u l p h a t e s a l t s from t h e b r i c k i n t o t h e m o r t a r , where t h e i r r e c r y s t a l l i z a t i o n caused d i s r u p t i o n of t h e m o r t a r .
SALTS I N BRICIGS
Before t h e p i e r s were c o n s t r u c t e d , t e s t s had been made of t h e v a r i o u s p h y s i c a l p r o p e r t i e s of t h e b r i c k s ; t h e
r e s u l t s a r e g i v e n in Table I. I n a d d i t i o n , a t e s t f o r e f f l o r e s - cence was made u s i n g t h e ASTM method i n which a b r i c k i s
p l a c e d f o r s e v e n days i n a pan c o n t a i n i n g d i s t i l l e d w a t e r 1
i n .
i n d e p t h . l//ater moves t h r o u g h t h e b r i c k and d i s s o l v e s s a l t s i n t h e b r i c k which a r e d e p o s i t e d on t h e s u r f a c e when t h e w a t e r e v a p o r a t e s . I n t h i s t e s t t h e d r y - p r e s s b r i c k s were h e a v i l y marked by s a l t d e p o s i t s b u t t h e e x t r u d e d b r i c k s were o n l y
s l i g h t l y a f f e o t e d . The samples t e s t e d a r e shown i n F i g u r e 4. The f i v e b r i c k s on t h e l e f t s i d e of e a c h row a r e t h o s e which were p l a c e d i n d i s t i l l e d w a t e r f o r s e v e n d a y s , t h e n d r i e d . The f i v e b r i c k s on t h e r i g h t s i d e of e a c h row a r e " c o n t r o l t ' b r i c k s which were d r i e d w i t h o u t t h e w e t t i n g t h a t t h e o t h e r
b r i c k s had received. T h i s t e s t c l e a r l y showed t h a t t h e dry- p r e s s b r i c k s had a much h i g h e r c o n t e n t of s o l u b l e s a l t s t h a n t h e extruded b r i c k s . Prom t h e work of o t h e r s on s o l u b l e
s a l t s i n b r i c k s it was considered probable t h a t s u l p h a t e s a l t s formed t h e e f f l o r e s c e n c e . A chemical a n a l y s i s of samples of t h e b r i c k s showed t h a t ' t h e d r y - p r e s s b r i c k con- t a i n e d 1 p e r c e n t SO4 while t h e extruded b r i c k contained
l e s s t h a n 0.05 p e r c e n t . !The compound formed by t h e s u l p h a t e was n o t determined.
SALTS
IE
MOR!PARThe lime f o r t h e mortar was hydrated lime which was soaked i n w a t e r o v e r n i g h t before b e i n g used. Although no chemical a n a l y s i s was made of t h e p a r t i c u l a r lime used i n c o n s t r u c t i n g t h e p i e r s , a n a n a l y s i s had been made of lime
obtained from t h e same source f o r previous work. This a n a l y s i s shovied t h a t t h e r e was no s u l p h a t e i n t h e l i m e , and t h a t v e r y small amounts of sodium and potassium were p r e s e n t ( 0 . 0 1 p e r c e n t a s potassium oxide and 0.02 p e r c e n t a s sodium o x i d e ) .
The a b i l i t y of s a l t s i n t h e d r y - p r e s s b r i c k s t o
migrate i n t o t h e mortar was i n d i c a t e d by t h e chemical a n a l y s i s of t h e mortar. I n June 1962, samples were t a k e n of decayed mortar from t h e p i e r of t h e d r y - p r e s s b r i c k and of a p p a r e n t l y sound mortzr from t h e p i e r of t h e extruded b r i c k . The chemical a n a l y s i s of t h e samples (Table 11) shows t h a t t h e r e was a con- s i d e r a b l y h i g h e r c o n t e n t of s u l p h a t e s a l t s i n t h e decayed mortar t h a n i n t h e sound mortar. X-ray a n a l y s i s was made of t h e sound and decayed mortars b u t d i d n o t y i e l d t h e i d e n t i t y of t h e
s u l p h a t e compound, n o r could it be l e a r n e d from d i f f e r e n t i a l thermal a n a l y s i s a l t h o u g h t h e l a t t e r i n d i c a t e d t h a t t h e
decayed mortar, and n o t t h e sound mortar, l o s t w a t e r on h e a t i n g t o a low temperature.
PERFORMANCE OF OTHER PIERS
H e r s made of t h e d r y - p r e s s b r i c k w i t h cement:lirne mortar and w i t h masonry cement mortar have n o t s u f f e r e d t h e s e v e r e c r a c k i n g of t h e mortar which occurred i n t h e p i e r of lime mortar. S p a l l i n g of t h e s u r f a c e of t h e mortar j o i n t s h a s occurred i n b o t h p i e r s , b u t t o a g r e a t e r degree w i t h t h e
cement:lime t h a n w i t h t h e masonry cement mortar. I n a d d i t i o n , some c r a c k i n g i n t h e m o r t a r j o i n t s of t h e p i e r of cement:lime mortar h a s developed, a s shown i n Figure 5. The p i e r s of b o t h t h e cement:lime and t h e masonry cement m o r t a r s have, from time t o time, been h e a v i l y marked by e f f l o r e s c e n c e (mainly sodium and potassium s u l p h a t e ) ; t h e p i e r of lime mortar was much l e s s marked by e f f l o r e s c e n c e .
P i e r s of t h e extruded b r i c k and t h e cement:lime and masonry cement mortars were l e s s a f f e c t e d t h a n t h e p i e r s of t h e d r y - p r e s s b r i c k by s p a l l i n g of t h e mortar. I n
a d d i t i o n , t h e p i e r s of t h e extruded b r i c k have been much l e s s marked by e f f l o r e s c e n c e t h a n t h o s e of t h e d r y - p r e s s b r i c k .
A chemical a n a l y s i s was made t o determine t h e s u l p h a t e c o n t e n t of mortar t a k e n from t h e p i e r s of t h e dry- p r e s s and extruded b r i c k s . Both t h e cement:lime and t h e masonry cement mortars contained p o r t l a n d cement, which
i t s e l f normally c o n t a i n s a c e r t a i n amount of calcium s u l p h a t e and o t h e r s u l p h a t e compouhds. I t i s n o t p o s s i b l e , t h e r e f o r e , t o determine, from t h e chemical a n a l y s i s of t h e s e m o r t a r s , t h e amount of s u l p h a t e s a l t s which may have migrated from t h e b r i c k t o t h e m o r t a r , because some s u l p h a t e would have been
p r e s e n t o r i g i n a l l y i n t h e mortar i t s e l f . The s u l p h a t e c o n t e n t s of t h e mortars, shown i n Table 111, c l e a r l y i n d i c a t e , however, a much h i g h e r c o n c e n t r a t i o n of s u l p h a t e i n m o r t a r used w i t h t h e d r y - p r e s s b r i c k t h a n i n t h e same mortar used w i t h t h e extruded b r i c k , i n d i c a t i n g a m i g r a t i o n of s u l p h a t e s a l t s from t h e d r y - p r e s s b r i c k t o t h e mortar.
Although t h e cement:lime m o r t a r of t h e p i e r of d r y - p r e s s b r i c k was h i g h e r i n s u l p h a t e t h a n t h e lime mortar of t h e p i e r of t h e same b r i c k , t h e former m o r t a r d i d n o t s u f f e r decay t o t h e same e x t e n t . S e v e r a l r e a s o n s may be advanced
f o r t h e g r e a t e r s u s c e p t i b i l i t y of t h e lime m o r t a r t o s p a l l i n g and c r a c k i n g . It may be more permeable, t h e r e b y a l l o w i n g
more r e a d i l y t h e movement of s u l p h a t e s o l u t i o n s from t h e b r i c k i n t o t h e mortar and from p l a c e t o place i n t h e mortar. I t undoubtedly h a s lower s t r e n g t h , and t h e r e f o r e would be l e s s a b l e t o r e s i s t t h e i n t e r n a l p r e s s u r e caused by s a l t c r y s t a l l i z a - t i o n w i t h i n it. The p o r o s i t y and pore s i z e s and shapes of
t h e lime mortar a r e probably d i f f e r e n t from t h o s e of t h e o t h e r m o r t a r s , which may have a n e f f e c t on t h e p r e s s u r e developed i n t h e s a l t c r y s t a l l i z a t i o n process.
CONCLUSIONS
The decay of t h e 1ime:sand m o r t a r of a brickwork p i e r , which progressed i n t h r e e y e a r s from s l i g h t s u r f a c e s p a l l i n g t o s e v e r e c r a c k i n g of t h e m o r t a r i s b e l i e v e d t o have been caused by t h e m i g r a t i o n of s u l p h a t e s a l t s from t h e b r i c k i n t o t h e m o r t a r where t h e i r c r y s t a l l i z a t i o n caused d i s r u p t i o n of t h e mortar. Another p i e r of t h e same m o r t a r b u t of a b r i c k much lower i n s u l p h a t e s a l t s h a s n o t s u f f e r e d t h i s damage. The decayed mortar was much h i g h e r i n s u l p h a t e s a l t s t h a n t h e sound mortar from t h e o t h e r p i e r . S e v e r a l a r t i c l e s i n t h e l i t e r a t u r e have been c i t e d which d e s c r i b e t h e f a i l u r e of
masonry m a t e r i a l s by t h e p r o c e s s of s a l t c r y s t a l l i z a t i o n t o which t h e p r e s e n t f a i l u r e i s a t t r i b u t e d . S p a l l i n g of cement:
l i m e and masonry cement m o r t a r s h a s a l s o b e e n o b s e r v e d a n d i s a p p a r e n t l y a s s o c i a t e d w i t h s u l p h a t e i n t h e m o r t a r . Cement: l i m e and masonry cement m o r t a r s , however, a p p e a r t o b e l e s s s u s c e p t i b l e t h a n l i m e m o r t a r t o d e c a y from s u l p h a t e s a l t s , p r o b a b l y b e c a u s e o f t h e i r g r e a t e r s t r e n g t h a n d g r e a t e r r e s i s t a n c e t o m i g r a t i o n of s a l t s o l u t i o n s . ACKNOWLEDGMENTS The a u t h o r w i s h e s t o t h a n k E. C . Goodhue o f t h e D i v i s i o n of A p p l i e d Chemistry f o r making t h e c h e m i c a l a n a l y s e s and J. E. G i l l o t t 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 c h f o r making X-ray and D.T.A. s t u d i e s .
REFERENCES
1. Anderegg, F. 0. H f l o r e s c e n c e . B u l l . No. 1 8 5 , Amer. Soc. T e s t . M a t s . , O c t o b e r 1952.
2, H a r d e s t y , J , M. D i s i n t e g r a t i o n o f f a c e b r i o k b y d i s s o l v e d s a l t s . B e l l L a b o r a t o r i e s Record, Vol. 2 2 , No. 5 , J a n u a r y 1944.
3. B u t t e r w o r t h , B, Some e f f e c t s of s o l u b l e s a l t s i n c l a y p r o d u c t s . T r a n s a c t i o n s of t h e B r i t i s h Ceramic S o c i e t y , Vol. 3 6 , 1937.
4. Connor, C. C. and W. E. Okerson. Recent d i s i n t e g r a t i o n of m o r t a r i n b r i c k w a l l s . Proc. Amer. Soc. T e s t . Mats., Vol. 57, 1957.
TABLE I
PROPERTIES OF THE BRICKS
- T A B U I1 ANALYSIS OF MORTAR P r o p e r t y I n i t i a l r a t e of a b s o r p t i o n (gm/30 sq i n . Water a b s o r p t i o n (%) (24-hr immersion) Water a b s o r p t i o n ( % )
( 5
h r b o i l ) S a t u r a t i o n c o e f f i c i e n t Compressive s t r e n g t h ( p s i ) Dry-press B r i c k (range i n v a l u e ) 46.2-
87.1 6.1-
8.3 7.3-
10.5 0.75-
0.84 3310-
6150 Component C a Mg s04 C02 NaK
Extruded B r i c k ( r a n g e i n v a l u e ) 31.1-
55.4
6.1-
6.9 7.6 - 1 0 . 0 0.75-
0.86 6460-
10,830Sound Mortar From P i e r o f Extruded B r i c k , $ 8.75
1 - 7 9
(0.05 10.6 0.04 0.04 + Decayed Mortar Prom P i e rof Dry-press B r i c k ,
%
8.71
1.70 0.83 11.3 0.08 0.08TABLE I11
SULPHATE CONTENT O F CENENT:LIN[E AND MASONRY
CEMENT MOR'PARS Mortar Used in Pier 1:1:6 (cement:lime:sand) 1:3 (masonry cement:sand) 1:1:6 (cement:lime:sand) 1:3 (masonry cement:sand) Brick Used in Pier dry-press dry-press extruded extruded
%
So4 in Mortar 1.14 0.66 0.26 0.29Figure 1. S c a l i n g o f mortar surface a t an e a r l y age (dry-press b r i c k s and lime : sand mortar )
.
F i g u r e 2 . Cracking o f mortar j o i n t s ; p i e r o f d r y - p r e s s b r i c k s and 1 i m e : s a n d mortar.
Figure 3. Sound mortar joints; pier of extruded b r i c k s and 1ime:sand
mortar.
Figure 4. Efflorescence t e s t of t h e b r i c k s . Top row: extruded b r i c k s
Bottom row: dry-press b r i c k s
The f i v e b r i c k s on t h e l e f t of each row were placed i n 1 i n . of d i s t i l l e d water f o r
7
days t h e n d r i e d . The f i v e b r i c k s on t h e r i g h t a r e " c o n t r o l n samples which were d r i e d without previous wetting.Figure
