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Petrographic Report on Aggregate Samples from the Worthington Mine
Dump and the High Falls Dam Site Excavation Copper Cliff, Ontario
NATIONAL RESEARCH COUNCIL O F CANADA DIVISION O F BUILDING RESEARCH
P E T R O G R A P H I C R E P O R T ON AGGREGATE S A M P L E S FROM THE WORTHINGTON MINE DUMP
AND THE HIGH F A L L S DAM S I T E EXCAVATION C O P P E R C L I F F , ONTARIO P. E. G r a t t a n - B e l l e w a n d E. G. Swenson I n t e r n a l R e p o r t No. 410 of t h e Division of Building R e s e a r c h OTTAWA N o v e m b e r 1973
P R E F A C E
M o s t c o n c r e t e in the Sudbury a r e a p e r f o r m s s a t i s f a c t o r i l y but a few s t r u c t u r e s have d e t e r i o r a t e d due to e x c e s s i v e c r a c k i n g of the c o n c r e t e ; t h i s h a s given r i s e t o the suspicion t h a t s o m e of the a g g r e g a t e s in the a r e a m a y show a l k a l i r e a c t i v i t y when used in c o n c r e t e . A number of s a m p l e s of r o c k f r o m the Sudbury a r e a w e r e r e c e i v e d f r o m Geocon Ltd. with a r e q u e s t t h a t t e s t s be c a r r i e d out t o d e t e r m i n e if the r o c k s a r e potentially a l k a l i expansive.
The s a m p l e s w e r e taken f r o m a Mine Waste dump and f r o m an excavation a t a d a m s i t e . Neither of the two r o c k s i s c u r r e n t l y being used a s a g g r e g a t e a s t h e r e is a v a s t supply of good g r a v e l in Sudbury. In the f u t u r e , however, higher haulage c o s t s o r a e s t h e t i c r e a s o n s m a y m a k e i t d e s i r a b l e t o u s e mine w a s t e r o c k a t l e a s t f o r the c o a r s e a g g r e g a t e ( s t o n e ) in c o n c r e t e . F o r this r e a s o n i t was decided to t e s t the s a m p l e s f o r a l k a l i r e a c t i v i t y .
The only positive way to d e t e r m i n e if a r o c k i s expansive is by the s t a n d a r d method for d e t e r m i n i n g the potential a l k a l i r e a c t i v i t y , i. e., the M o r t a r B a r Method ASTM T e s t C 227-69. In addition to doing the m o r t a r b a r t e s t s , thin s e c t i o n s of the r o c k s w e r e p r e p a r e d and p e t r o - g r a p h i c d e s c r i p t i o n s m a d e t o define the r o c k types o c c u r r i n g in the s a m p l e s . I t will thus be p o s s i b l e to c o m p a r e s i m i l a r r o c k s with t h e s e and s o e s t i m a t e t h e i r potential f o r a l k a l i r e a c t i v i t y .
OTTAWA
November 1973
N. B. Hutcheon D i r e c t o r
PETROGRAPHIC REPORT ON AGGREGATE SAMPLES FROM THE WORTHINGTON MINE DUMP
AND THE KIGH FALLS DAM SITE EXCAVATION COPPER C L I F F , ONTARIO
P. E. G r a t t a n - B e l l e w and E. G. Swenson
Two s a m p l e s of r o c k w e r e r e c e i v e d f r o m Geocon L t d . , with a r e q u e s t t h a t s o m e t e s t s be c a r r i e d out t o d e t e r m i n e if the s a m p l e s would b e s u i t a b l e f o r u s e a s a g g r e g a t e in c o n c r e t e . The covering l e t t e r , dated
5 May, 1972, s t a t e d that the r o c k is a l r e a d y being used a s a g g r e g a t e i n c o n c r e t e . A subsequent v i s i t t o Sudbury showed that m o s t c o n c r e t e in the a r e a i s being m a d e with a g g r e g a t e d e r i v e d f r o m g l a c i a l g r a v e l s and t h a t only s m a l l jobs, done by l o c a l c o n t r a c t o r s o r p r i v a t e individuals who m i x c o n c r e t e on s i t e , m i g h t u s e r o c k f r o m a l o c a l m i n e dump a s a g g r e g a t e .
Although m i n e w a s t e r o c k i s not c u r r e n t l y being used t o a n y extent a s a g g r e g a t e in c o n c r e t e , i t i s obviously a potential s o u r c e t h a t m i g h t be tapped if a l a r g e s t r u c t u r e w e r e t o b e e r e c t e d a d j a c e n t t o a n
old m i n e dump. An in-depth study of a g g r e g a t e s in the Sudbury a r e a i s c u r r e n t l y being m a d e a s p a r t of DBR P r o j e c t M13 173 and i t w a s f e l t that a n examination of the two s a m p l e s f r o m Geocon Ltd. would f o r m a useful addition t o t h a t study. F u r t h e r m o r e , d a t a obtained f r o m a
study and t h e testing of t h e s e r o c k s would add t o the growing fund of knowledge concerning the potential f o r a l k a l i - r eac tivity of Canadian a g g r e g a t e s .
The p e t r o g r a p h i c examination upon which t h i s r e p o r t is b a s e d was undertaken s o that r e a s o n a b l y e x a c t d e s c r i p t i o n s of the r o c k types would b e a v a i l a b l e f o r c o m p a r i s o n with other s a m p l e s of broadly
s i m i l a r m a t e r i a l . In o r d e r t o check on the a l k a l i - r e a c t i v i t y potential of the r o c k s in c o n c r e t e ASTM C227-69, M o r t a r B a r T e s t s , (1) a r e c u r r e n t l y being m a d e on the s a m p l e s in the DBRINRC l a b o r a t o r i e s in Ottawa. The r e s u l t s of t h e s e t e s t s a r e given in the Appendix.
SUMMARY AND CONCLUSIONS
The following r o c k types w e r e identified in t h e s a m p l e of w a s t e r o c k f r o m the Worthington Mine:
DBR No. 72-1 Amphibolite containing 85 p e r c e n t aimphibole;
72 -2 Qtlartx aillphi1)olc 1)ic)titc g n c - i s s . ' I ' l l L S r o t I, t 0 1 1 t . t 111s bands of f e l s i c and m a f i c n ~ a t c r l a l . In the I t - l s l t . I ) L ~ n t l s , q u a r t z c o m p r i s e s about 65 p e r c e n t of the rock, a m p h i - bole 10 p e r cent. The p e r c e n t a g e s a r e r e v e r s e d in the m a f i c r i c h p o r t i o n s ; and
72-3 Q u a r t z biotite c h l o r i t e s c h i s t containing about 55 p e r c e n t q u a r t z .
High F a l l s Dam S i t e
S a m p l e DBR No. 72-4 f r o m the d a m s i t e a t High F a l l s was amphibolite s c h i s t containing 80 p e r c e n t amphibole and two p e r c e n t chalcopyrite. T h i s s a m p l e i s d i f f e r e n t f r o m the amphibole g n e i s s 72 -1 f r o m the Worthington Mine; f o r d e t a i l s s e e the p e t r o g r a p h i c d e s c r i p t i o n s t h a t follow.
S a m p l e 72-4 and the r o c k s f r o m the Worthington Mine contain a few p e r c e n t of c h a l c o p y r i t e o r pentlandite and p y r i t e o r both.
M u k h e r j e e e t a1 (2) c a r r i e d out m o r t a r b a r t e s t s t h a t indicated t h a t p y r i t i f e r o u s amphibolite A P 50D was n o n - r e a c t i v e . A p e t r o g r a p h i c d e s c r i p t i o n of t h i s r o c k by J. E. Gillott (unpublished d a t a of DBR) i n d i c a t e s that this r o c k is v e r y s i m i l a r to the s c h i s t f r o m the d a m s i t e a t High F a l l s , 72-4. F r o m t h i s i t i s concluded that the amphibole
s c h i s t a t High F a l l s i s unlikely t o be r e a c t i v e . A brief examination of the r o c k s in the i m m e d i a t e vicinity of the dam, suggested t h a t the r o c k was f a i r l y uniform, hence the s a m p l e t e s t e d c a n be c o n s i d e r e d r e a s o n - ably r e p r e s e n t a t i v e . Additional sampling and t e s t i n g would, however, be a d v i s a b l e b e f o r e the r o c k was used a s a g g r e g a t e . I t i s of i n t e r e s t t o note that s a m p l e s of a g g r e g a t e f r o m c o n c r e t e d r i l l c o r e s f r o m the High F a l l s Dam w e r e not amphibole s c h i s t , the l o c a l bedrock, but o t h e r r o c k types which w e r e probably brought i n f r o m e l s e w h e r e .
Waste Rock f r o m the Worthington Mine
L
.
Dolar -Mantuani (3) w r o t e "No difficulties o c c u r r e d with f r e s h biotite g n e i s s e s . " This s u g g e s t s that S a m p l e 72 -3, a q u a r t z biotite c h l o r i t e s c h i s t , m i g h t not be r e a c t i v e . The effect of thep r e s e n c e of c h l o r i t e i s not known, however, s o no definite conclusion c a n be d r a w n about t h i s rock. The other s a m p l e s a r e probably non- r e a c t i v e but owing to the e x t r e m e v a r i a b i l i t y and the a l t e r e d n a t u r e of
m u c h r o c k found in m i n e w a s t e dumps, caution should b e e x e r c i s e d i n using s u c h r o c k a s a g g r e g a t e in c o n c r e t e . To obtain a r e p r e s e n - t a t i v e s a m p l e a c o n s i d e r a b l e a m o u n t of r o c k would need to b e c o l l e c t e d . P o s s i b l y the b e s t p r o c e d u r e would b e t o c r u s h a quantity of r o c k , about half a cubic y a r d , a n d then c o n e and q u a r t e r t h e c r u s h i n g s to p r o d u c e a s m a l l s a m p l e f r o m which to m a k e m o r t a r b a r s f o r the ASTM t e s t C227
-
69.The l o c a t i o n of t h e High F a l l s Dam a n d t h e Worthington Mine a r e shown on a m a p of t h e Sudbury A r e a F i g u r e 1.
PETROGRAPHIC DESCRIPTION O F FOUR ROCK SAMPLES FROM C O P P E R C L I F F A R E A , SUDBURY
S a m p l e of Mine W a s t e Rock f r o m Worthington Mine (DBR No. 72 -1)
The hand s p e c i m e n is a m e d i u m - g r a i n e d b l u e g r e e n 5G 311 r o c k (4) with a m a x i m u m g r a i n s i z e of a b o u t 1 rnrn. S e e n through a hand l e n s t h e r o c k a p p e a r s t o c o n s i s t of l a t h - s h a p e d a m p h i b o l e c r y s t a l s . F i n e l y divided c h a l c o p y r i t e m a k e s up 1 t o 5 p e r c e n t of t h e r o c k . The r o c k is n o n - m a g n e t i c a s judged by i t s i n a b i l i t y t o d e f l e c t a s m a l l s u s p e n d e d m a g n e t and is a s c h i s t o s e amphibolite. M i c r o s c o p i c e x a m i n a t i o n of a thin s e c t i o n showed t h e r o c k t o c o n s i s t m a i n l y of a m p h i b o l e which h a s r e p l a c e d o r i g i n a l p y r o x e n e s . A s m a l l a m o u n t of biotite, q u a r t z a n d s u l p h i d e s (opaque m i n e r a l s ) a r e a l s o p r e s e n t . A t y p i c a l a r e a of t h e thin s e c t i o n i s shown in F i g u r e s 2 a n d 3. In p r i s m a t i c s e c t i o n s t h e amphibole is weakly p l e o c h r o i c i n s h a d e s of p a l e g r e e n t o brown.
Jn
b a s a l s e c t i o n s , which show t h e c h a r a c t e r - i s t i c c l e a v a g e s i n t e r s e c t i n g a t 120" ( F i g u r e 4 ) , t h e a m p h i b o l e i s ad a r k brown c o l o r . The s m a l l g r a i n s of q u a r t z a r e r e a d i l y d i s t i n g u i s h e d f r o m t h e a m p h i b o l e s by t h e i r low r e f r a c t i v e index and c o l o r l e s s a p p e a r - a n c e a s w e l l a s by t h e i r o p t i c a l p r o p e r t i e s . Biotite, which o c c u r s a s o c c a s i o n a l f l a k e s , i s d i s t i n g u i s h e d by i t s s t r o n g p l e o c h r o i s m a n d c h a r a c t e r i s t i c p o l a r i z a t i o n c o l o r s . Opaque m i n e r a l s , shown by e x a m i n a t i o n in r e f l e c t e d l i g h t t o b e d o m - inantly c h a l c o p y r i t e , o c c u r a s s m a l l g r a i n s d i s s e m i n a t e d throughout t h e r o c k . The a p p r o x i m a t e c o m p o s i t i o n of t h e m i n e w a s t e r o c k f r o m Wor thington Mine, e s t i m a t e d v i s u a l l y , i s :
Amphibole, 85 p e r cent; Biotite, 5 t o 7 p e r cent; Q u a r t z , 5 p e r cent; a n d Opaque M i n e r a l s , 1 t o 3 p e r c e n t .
The rocl, i s an amphibolite that has r e s u l t e d f r o m thc alteration of an original pyroxene r i c h rock. The thin section does not s h o w any obvious foliation but in the hand s p e c i m e n thc rock looks vaguely s c h i s t o s e due to the lath shape of the amphibole c r y s t a l s .
Second Sample F r o m Worthington Mine Waste Rock (DBR No. 72 -2) Examination of the r o c k with a hand l e n s shows i t to b e a q u a r t z m i c a s c h i s t . It contains blebs of chalcopyrite that a r e aligned p a r a l l e l to a poorly developed foliation. The r o c k h a s a d a r k g r e y color, N 3.5 (4). It i s m o d e r a t e to weakly magnetic. An examination of a thin section of the r o c k showed i t to c o n s i s t of fine g r a i n s of q u a r t z and amphibole with m i n o r amounts of biotite, f e l d s p a r and sulphides (opaque m i n e r a l s ) . The r o c k h a s a poorly defined foliation due t o the alignment of the biotite flakes, which a r e p a r a l l e l to the boundary between amphibole r i c h (mafic) and amphibole poor (felsic) p a r t s of the thin section ( F i g u r e 5). The amphibole r i c h zone i s on the left side. F i g u r e 6 shows the s a m e a r e a in polarized light, i n this f i g u r e the twinned f e l d s p a r s c a n be r e a d i l y distinguished f r o m the untwinned q u a r t z c r y s t a l s . Some of the q u a r t z g r a i n s show undulatory extinction, o t h e r s do not. Undulatory extinction i s c h a r a c t e r i s t i c of s t r a i n e d g r a i n s and m a y be due e i t h e r to crowding of the g r a i n s during c r y s t a l - lization o r to deformation of the r o c k (5, p. 41). In a deformed m e t a - m o r p h i c r o c k such a s this, s t r a i n e d q u a r t z g r a i n s a r e to b e expected. Gillott e t a1 (6, p. 20) l i s t among "potentially r e a c t i v e s u b s t a n c e s involved in well recognized alkali- s i l i c a r eac tionsf' c o a r s e grained q u a r t z s t r a i n e d internally and c r a c k e d . In the w r i t e r s t opinion,
however, too m u c h importance should not b e placed upon this a s m o s t q u a r t z bearing m e t a m o r p h i c r o c k s (the dominant type in the Canadian Shield) might b e expected to have s t r a i n e d q u a r t z g r a i n s .
Amphibole.
-
M o s t of the amphibole i s c h a r a c t e r i z e d by i t s pale g r e e n color, m o d e r a t e r e f r a c t i v e index and weak pleochroism. Occasional b a s a l sections show the c h a r a c t e r i s t i c cleavages i n t e r s e c t i n g a t 120" ( F i g u r e 7).Biotite.
-
Biotite i s easily distinguished f r o m amphibole by i t sc h a r a c t e r i s t i c pale to d a r k brown pleochroism. Some biotite i s s e e n i n F i g u r e 7 in which s o m e a c c e s s o r y m i n e r a l s , with a high r e f r a c t i v e index, m a y a l s o be observed; t h e s e w e r e not positively identified but m a y b e rutile. In the thin section the opaque m i n e r a l s c o m p r i s e f r o m one to f i v e p e r c e n t of the rock; chalcopyrite dominates and s o m e p y r i t e a l s o o c c u r s . The opaque m i n e r a l s occur a s s m a l l 20-urn g r a i n s and a s l a r g e r patches aligned s u b p a r a l l e l to the foliation. The l a r g e s t opaque a r e a s a r e about 2 mm long ( F i g u r e 8).
The r o c k i s a q u a r t z amphibole g n e i s s with m i n o r f e l d s p a r and sulphides. I t s approximate composition, e s t i m a t e d visually, follows.
Dominant o r f e l s i c r i c h p a r t of the r o c k Mafic o r amphibole r i c h s e c t i o n s q u a r t z 50 to 65% amphibole 10 to 15% biotite 10 to 20% opaque 1 to 3% f e l d s p a r 5% a c c e s s o r i e s 2 to 3% q u a r t z 30 to 40% amphibole 50 to 7 0% biotite 10 to 15% a c c e s s o r y m i n e r a l s 5
70
Third Sample F r o m Worthington Mine Waste Rock (DBR No. 72 - 3 ) In the hand s p e c i m e n the r o c k is s e e n to c o n s i s t of q u a r t z and m i c a with blebs of chalcopyrite up to 3 by 1 m m which m a k e up 10 to 15 p e r c e n t of the rock. The rock, which h a s a m e d i u m g r e e n color N4. 5. 1 (4) is poorly foliated; i t i s weakly magnetic. In thin section the r o c k is s e e n to b e a quartz, biotite,chlorite g n e i s s with 10 to 15 p e r c e n t of sulphides, chalcopyrite and pentlandite. A l a r g e g r a i n of
sulphide is shown in F i g u r e 9. Upon c l o s e r examination the sulphide g r a i n i s s e e n to c o n s i s t of two m i n e r a l s , the lighter chalcopyrite and the d a r k e r pentlandite
.
An a v e r a g e a r e a of the thin section i s shown in F i g u r e s 10 and 11, in which biotite, chlorite, q u a r t z and a l t e r e d f e l d s p a r c a n be readily distinguished. All the m i n e r a l s occur a s angular to subangular g r a i n s with a n a v e r a g e g r a i n s i z e of between 0.1 and 0.2 mm. A few q u a r t z g r a i n s appear to have e u h e d r a l outlines. F e l d s p a r , not a common con- stituent of the rock, o c c u r s m o s t l y a s a l t e r e d clouded g r a i n s but a few f r e s h twinned plagioclase g r a i n s w e r e observed. Chlorite, F i g u r e 10, i s r e a d i l y distinguished f r o m biotite by i t s pale g r e e n color in n o r m a l light, which i s in m a r k e d c o n t r a s t to the pleochroic brown color of the biotite. Chlorite c a n b e s t be distinguished f r o m q u a r t z and f e l d s p a r i n polarized light by its g r e e n g r e y o r u l t r a blue polarization c o l o r s . The r o c k h a s a m o d e r a t e foliation due to the s u b - p a r a l l e l alignment of biotite and chlorite. This i s not obvious in thin section a s the s c a l e of the foliation is too l a r g e to be observed in the s m a l l a r e a viewed in the m i c r o s c o p e . The r o c k is a f i n e grained quartz, biotite, c h l o r i t e s c h i s t c o n t a i n i n g c h a l c o p y r i t e a n d p e n t l a n d i t e . I t s a p p r o x i m a t e c o m - position e s t i m a t e d visually is: Quartz, 50 to 60 p e r cent; Biotite, 10 to 20 p e r cent; Chlorite, 10 to 20 p e r cent; F e l d s p a r , 2 to 7 p e r cent; and Sulphides, 5 p e r cent.
S c h i s t fro111 thcx D a i ~ l a t High F a l l s ( D B R No. 7 2 - 4 )
In thc hand specirnen the r o c k a p p e a r s to b c a g r e c n s c h i s t . 1t
i s a fine grained m e d i u m g r e y N 4. 5 ( 4 ) rock that contains one to two p e r c e n t d i s s e m i n a t e d chalcopyrite. I t i s non-magnetic.
In thin section the r o c k i s composed dominantly of amphibole with m i n o r biotite and c h l o r i t e . The amphibole o c c u r s in two f o r m s : i) a f i n e f i b r o u s v a r i e t y actinolite or u r a l i t e , the l a t t e r usually being a n a l t e r a t i o n p r o d u c t of o r i g i n a l pyroxenes; and ii) a c o a r s e r amphibole occuring a s i r r e g u l a r l y shaped a r e a s o r b a s a l s e c t i o n s showing the typical diamond s h a p e and c l e a v a g e s i n t e r s e c t i n g a t 120" ( F i g u r e 12, which a l s o shows the fine g r a i n e d amphibole).
The r o c k shows a c o m p l e x foliation p a t t e r n and a p p e a r s to
have undergone c o n s i d e r a b l e deformation. The s u b p a r a l l e l a r r a n g e m e n t of the f i n e g r a i n e d amphibole i m p a r t s a foliation t o the rock. In s o m e i n s t a n c e s the foliation a p p e a r s t o "flow" a r o u n d l a r g e c h l o r i t e o r a m - phibole g r a i n s i m p a r t i n g a vague augen t e x t u r e to the r o c k . It i s difficult to c a p t u r e this effect in the s m a l l a r e a of a m i c r o g r a p h but s o m e idea of i t c a n be obtained f r o m F i g u r e 13.
A n a r r o w vein f i l l e d with c a l c i t e and q u a r t z c u t s a c r o s s the section, ( F i g u r e 14). The q u a r t z and c a l c i t e a r e r e a d i l y distinguished by t h e i r optical p r o p e r t i e s and by the c h a r a c t e r i s t i c rhombohedra1 c l e a v a g e of the l a t t e r m i n e r a l . Biotite o c c u r s a s i s o l a t e d f l a k e s o r c l u s t e r s of them. I t c o m p r i s e s 1 to 5 p e r c e n t of the rock. A twinned biotite f l a k e i s s e e n in F i g u r e 15. Opaque m i n e r a l s , m o s t l y chalcopyrite, o c c u r a s g r a i n s s c a t t e r e d throughout the section; they m a k e up about one p e r c e n t of the r o c k . C h l o r i t e in s o m e i n s t a n c e s a p p e a r s to have r e p l a c e d amphibole.
F i g u r e 13 shows a l a r g e g r a i n of c h l o r i t e that h a s the diamond s h a p e c h a r a c t e r i s t i c of b a s a l s e c t i o n s of amphibole. The r o c k is a foliated amphibolite s c h i s t , with m i n o r chalcopyrite. I t s a p p r o x i m a t e composition, e s t i m a t e d visually, is: Amphibole 80 p e r c e n t ; C h l o r i t e 10 p e r cent; Biotite 5 to 7 p e r cent; and Chalcopyrite 1 to 3 p e r cent.
CONCLUDING STATEMENT
The r e s u l t s of the M o r t a r B a r T e s t s indicate t h a t a l l the r o c k s t e s t e d a r e non-expansive.
Worthington Mine Waste Rock
T h r e e r o c k types w e r e identified: amphibolite; q u a r t z amphibole biotite g n e i s s ; and a q u a r t z biotite c h l o r i t e s c h i s t . The a u t h o r s have
not v i s i t e d the Worthington M i n e but a n e x a m i n a t i o n of the w a s t e r o c k a t the V i c t o r i a Mine, which i s n e a r b y , showed t h a t thc roclt types f o u n d in m i n e w a s t c a r c v a r i a b l e ; s o m c of the a l t e r e d r o c k s t h a t wcrL3 forlncl would b e highly s u s p e c t f o r potential a l k a l i - r e a c t i v i t y . It i s not c e r t a i n t h a t the t h r e e r o c k t y p e s l i s t e d h e r e would b e r e p r e s e n t a t i v e of the r o c k p i l e a s a whole, and so, although t h e t h r e e s a m p l e s did not show e x c e s s i v e expansion i t would b e a d v i s a b l e t o t e s t a m o r e r e p r e s e n t a t i v e s a m p l e b e f o r e the r o c k w a s u s e d a s a g g r e g a t e in l a r g e exposed s t r u c - t u r e s s u c h a s d a m s a n d b r i d g e s w h e r e t h e e f f e c t of a l k a l i e x p a n s i v i t y i s m o s t l i k e l y t o c a u s e p r o b l e m s .
The High F a l l s Dam S i t e
T h e r o c k f r o m t h i s s i t e i s a n a m p h i b o l i t e s c h i s t containing about t h r e e p e r c e n t c h a l c o p y r i t e . This r o c k type i s not r e a c t i v e , but s o m e a d d i t i o n a l s a m p l e s should p o s s i b l y be t e s t e d b e f o r e the r o c k i s u s e d a s a g g r e g a t e in c o n c r e t e t o e n s u r e t h a t t h e s a m p l e t e s t e d i s r e p r e s e n t a t i v e of t h e r o c k m a s s a s a whole. R E F E R E N C E S 1. A S T M C227-69. S t a n d a r d T e s t Method f o r P o t e n t i a l A l k a l i R e a c t i v i t y of C e m e n t - A g g r e g a t e Combinations ( M o r t a r B a r Method). 1970 Annual Book of ASTM S t a n d a r d s , p. 50-56.
2. P.K. M u k h e r j e e , M.A.G. Duncan, M.R. F o r a n and A. S a m a n t a (1970). The E x p a n s i v e B e h a v i o r of M o r t a r B a r s P r e p a r e d f r o m A l k a l i - S e n s i t i v e Nova S c o t i a C o n c r e t e A g g r e g a t e s . R e p o r t t o t h e Nova S c o t i a P r o j e c t C o m m i t t e e on C o n c r e t e , Nova S c o t i a T e c h n i c a l
College, Halifax.
3. L. Dolar -Mantuani (1972). H a r m f u l Constituents i n N a t u r a l C o n c r e t e A g g r e g a t e s in O n t a r i o . 24th Int. Geol. Conf.
,
Section 13, p.227 - 234.
a.
Rock C o l o r C h a r t . D i s t r i b u t e d by t h e Geological Society of A m e r i c a , R e p r i n t e d in 1963.5. W.W. M o o r h o u s e (1959). The Study of R o c k s in Thin Section, H a r p e r s G e o s c i e n c e S e r i e s .
6. J. E. Gillott, M. A. G. Duncan a n d E. G. Swenson. P e t r o g r a p h y of C o n c r e t e A g g r e g a t e s and F i e l d C o r e s in Nova Scotia. R e p o r t p r e - p a r e d f o r Nova S c o t i a P r o j e c t C o m m i t t e e on C o n c r e t e , Nova S c o t i a
F I G U R E 1
G E O L O G I C A L M A P O F T H E H I G H F A L L S - W O R T H I N G T O N A R E A . S C A L E 1 I N C H : 1 M I L E .
C o m p i l e d f r o m G . S . C . maps 2 9 2 A 8 2 9 1 A , a n d G . S . C . r e p o r t b u 1 1 . 3 . 1 9 4 6 , b y H . C . C o o k e . m .,I.(
Abbreviations: A - Amphibole
r
A P - P r i s m a t i c1
AB - B a s a l S e c t i o n Q-
Q u a r t z F i g u r e 2 Section 72- 1, Amphibolite. X 25. N o r m a l Light. F i g u r e 3 Section 72-1. (Same a r e a a s F i g u r e 2 ) X 25. P o l a r i z e d Light.A b b r e v i a t i o n s : AB
-
B a s a l S e c t i o n of Amphibole A P - P r i s m a t i c S e c t i o n of Amphibole A - U n d i f f e r e n t i a t e d Amphibole F-
F e l d s p a r Q-
Q u a r t z F i g u r e 4 S e c t i o n 72-
1. Amphibolite. X 100. N o r m a l Light. F i g u r e 5 S e c t i o n 72-2. Q u a r t z Amphibole B i o t i t e G n e i s s . X 25. N o r m a l Light.A b b r e v i a t i o n s : A
-
A m p h i b o l e A C-
A c c e s s o r y M F-
F e l d s p a r Q - Q u a r t z P o s s i b l y R u t i l e ? i n e r a1 F i g u r e6
S e c t i o n 72-2. ( S a m e a r e a a s F i g u r e 5 ) X 25. P o l a r i z e d Light. F i g u r e 7 S e c t i o n 72-2. Q u a r t z A m p h i b o l e B i o t i t e G n e i s s . X 100. N o r m a l Light.A b b r e v i a t i o n s : A
-
Amphibole B-
B i o t i t e C P-
C h a l c o p y r i t e F-
F e l d s p a r P N-
P e n t l a n d i t e P Y-
P y r i t e Q-
Q u a r t z F i g u r e 8 S e c t i o n 72-2. X 25. N o r m a l Light. Q u a r t z B i o t i t e Amphibole G n e i s s . F i g u r e 9 S e c t i o n 72 -3. Q u a r t z B i o t i t e C h l o r i t e G n e i s s Showing L a r g e G r a i n of Sulphide. X 10. N o r m a l Light.A b b r e v i a t i o n s : B
-
B i o t i t e CH - C h l o r i t e F-
F e l d s p a r Q - Q u a r t z F i g u r e 1 0 S e c t i o n 72 - 3 . Q u a r t z B i o t i t e C h l o r i t e G n e i s s . N o r m a l Light. X 40. F i g u r e 11 S e c t i o n 72 - 3 . ( S a m e a r e a a s F i g u r e 1 0 ) X 40. P o l a r i z e d Light.A b b r e v i a t i o n s : A - Amphibole CH
-
C h l o r i t e U - F i b r o u s Amphibole F i g u r e 12 S e c t i o n 72-4. Amphibolite. X 100. P o l a r i z e d Light. F i g u r e 13 S e c t i o n 72-4. Amphibolite. X 25. P o l a r i z e d Light.A b b r e v i a t i o n s : A - A m p h i b o l e B - B i o t i t e CA - C a l c i t e 0
-
Opaque S u l p h i d e s Q - Q u a r t z U-
F i b r o u s A m p h i b o l e F i g u r e 14 S e c t i o n 72 -4. A m p h i b o l i t e with C a l c i t e Q u a r t z Vein. X 40. P o l a r i z e d Light. F i g u r e 15 S e c t i o n 72-4. A m p h i b o l i t e . X 40. N o r m a l Light.A P P E N D I X
R E S U L T S O F MORTAR BAR TESTS
R o c k s a m p l e s f r o m the Worthington M i n e d u m p and t h e High F a l l s D a m s i t e w e r e t e s t e d f o r p o t e n t i a l a l k a l i r e a c t i v i t y of c e m e n t a g g r e g a t e c o m b i n a t i o n s by the M o r t a r B a r T e s t , ASTM C227 - 6 9 . P a i r s of m o r t a r b a r s w e r e m a d e f r o m e a c h s a m p l e with both high and low a l k a l i c e m e n t . Xc
The b a r s w e r e c o n d i t i o n e d a t 100 p e r c e n t r e l a t i v e h u m i d i t y a n d 100"
F
and w e r e m e a s u r e d a t m o n t h l y i n t e r v a l s . T h e r e s u l t s a r e shown on F i g u r e A l , on which the e x p a n s i o n c u r v e s of a n o n - r e a c t i v e r e f e r e n c e s a m p l e and a highly r e a c t i v e r h y o l i t e f r o m Nova S c o t i a a r e a l s o shown.F r o m F i g u r e A1 i t c a n b e s e e n t h a t a l l t h e S u d b u r y s a m p l e s a r e l e s s e x p a n s i v e t h a n t h e r h y o l i t e b u t s o m e w h a t m o r e e x p a n s i v e than the r e f e r e n c e b a r . T h e s a m p l e s m a d e with high a l k a l i c e m e n t a r e m a r g i n a l l y , but n o t s i g n i f i c a n t l y , m o r e e x p a n s i v e t h a n t h o s e m a d e with low a l k a l i c e m e n t ; t h i s s u g g e s t s t h a t s o m e r e a c t i o n h a s o c c u r r e d b e t w e e n the a l k a l i s i n t h e c e m e n t and the a g g r e g a t e . E x p a n s i o n of 0.05 p e r c e n t o r g r e a t e r is c o n s i d e r e d e x c e s s i v e ; t h e e x p a n s i o n c u r v e s of t h e S u d b u r y r o c k s a r e a s y m p t o t i c t o a b o u t 0.035 p e r c e n t and s o i t is c o n c l u d e d t h a t t h e r o c k s a r e e s s e n t i a l l y n o n - e x p a n s i v e .
E x t r a p o l a t i o n of a l o g a r i t h m i c p l o t of t h e e x p a n s i o n of the M o r t a r B a r s t o 30 y e a r s i n d i c a t e d t h a t with high a l k a l i c e m e n t t h e e x p e c t e d e x - p a n s i o n would b e f r o m 0. 05 t o 0.08 p e r c e n t , which would put t h e s a m p l e s i n a m a r g i n a l l y e x p a n s i v e c a t e g o r y . With l o w a l k a l i c e m e n t t h e e x p e c t e d e x p a n s i o n would b e b e t w e e n 0.05 a n d 0.07 p e r c e n t ; n o t s i g n i f i c a n t l y d i f f e r e n t f r o m t h e r e s u l t s obtained with high a l k a l i c e m e n t . T h e r e l i - a b i l i t y of s u c h a n e x t r a p o l a t i o n i s n o t known, but f r o m w o r k d o n e t o d a t e , i t a p p e a r s t h a t with e x p a n s i v e r o c k s , t h e d e l e t e r i o u s e x p a n s i o n o c c u r s d u r i n g t h e f i r s t 100 t o 200 d a y s . A f t e r that, the s l o p e of t h e l o g a r i t h m i c g r a p h i s p a r a l l e l t o t h a t of a non e x p a n s i v e s a m p l e , a n d f o r t h i s r e a s o n i t i s f e l t t h a t t h e e x t r a p o l a t i o n m a y b e j u s t i f i e d , h o w e v e r t o o m u c h r e l i a n c e s h o u l d n o t b e p l a c e d upon i t a s t h e m a t t e r is s t i l l u n d e r i n v e s - tigation. F r o m t h e r e s u l t s of t h e M o r t a r B a r t e s t s i t is c o n c l u d e d t h a t t h e r o c k s i n v e s t i g a t e d would b e s u i t a b l e f o r u s e a s a g g r e g a t e i n c o n c r e t e , p r o v i d e d t h a t t h e y p a s s t h e u s u a l s o u n d n e s s t e s t s . T h e q u e s t i o n of how r e p r e s e n - t a t i v e t h e s a m p l e s a r e of t h e r o c k m a s s , which w a s m e n t i o n e d on p. 6 a n d 7, should h o w e v e r b e k e p t i n m i n d .
