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Alkali-aggregate reaction in Nova Scotia. Part 1. Summary of a 5-year
study
Duncan, M. A. G.; Swenson, E. G.; Gillott, J. E.; Foran, M. R.
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p p .
55-69, 1973. Pergamon P r e s s , Inc. P r i n t e d i nthe
United S t a t e s .ALKALI-AGGREGATE REACTION IN NOVA SCOTIA I. SUMMARY O F A FIVE-YEAR STUDY
M. A. G. Duncan, A t l a n t i c I n d u s t r i a l R e s e a r c h I n s t i t u t e , Halifax; now with M i n i s t r y of R o a d s , S a l i s b u r y , R h o d e s i a .
E. G. Swenson, Div. of Building R e s e a r c h , Nat. R e s . C o u n c i l of C a n a d a . J. E . Gillott, Div. of Building R e s e a r c h , Nat. R e s . C o u n c i l of C a n a d a ; now
with Univ. of C a l g a r y , C a l g a r y , A l b e r t a . M. R. F o r a n , Nova S c o t i a T e c h n i c a l C o l l e g e , H a l i f a x , ( D e a n of G r a d u a t e S t u d i e s ) ; now r e t i r e d . (Communicated by
G .
M .
I d o r n ) ABSTRACT L a b o r a t o r y e x p e r i m e n t s c o n f i r m e d t h a t a l k a l i - a g g r e g a t e r e a c t i o n c a u s e d e x c e s s i v e e x p a n s i o n of s o m e Nova S c o t i a c o n c r e t e . M a j o r r o c k t y p e s w e r e t e s t e d a s a g g r e g a t e s i n m o r t a r b a r s and c o n c r e t e p r i s m s and a s r o c k c y l i n d e r s i m m e r s e d i n a l k a l i s o l u t i o n . G r e y-
w a c k e s , a r g i l l i t e s , p h y l l i t e s , and s o m e q u a r t z i t e s , s c h i s t s and r h y o l i t e s w e r e identified a s h i g h l y r e a c t i v e t h r o u g h p e t r o g r a p h i c s t u d i e s and l e n g t h c h a n g e t e s t s . S OMMAIRE D e s e x p g r i e n c e s e n l a b o r a t o i r e c o n f i r m e n t q u e l a d i l a t a t i o n e x c e s - s i v e de c e r t a i n s bCtons e n Nouvelle E c o s s e e s t due 3 u n e r 6 a c t i o n a l c a l i - g r a n u l a t . L e s p r i n c i p a u x g e n r e s d e r o c h e f u r e n t m i s 'a l ' e s s a i c o m m e g r a n u l a t s d a n s d e s b a r r e s d e m o r t i e r et d e s p r i s m e s d e bhton, e t s o u s f o r m e de c y l i n d r e s d e r o c h e plong6s d a n s u n e s o l u t i o n a l c a l i n e . L e s g r a u w a c k e s , a r g i l i t e s , p h y l l i t e s et c e r t a i n s q u a r t z i t e s , s c h i s t e s et r h y o l i t e s f u r e n t i d e n t i f i g s c o m m e d e s r o c h e s tr'es r g a c t i v e s , a u m o y e n d'Ctudes ~ C t r o g r a p h i q u e s et d ' e s s a i s d e c h a n g e m e n t d e l o n g u e u r .A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE
V o l . 3, N o . 1
Introduction
An e x t e n s i v e investigation was begun in 1965 to d e t e r m i n e t h e n a t u r e
of and solution to a c o n c r e t e p r o b l e m in t h e P r o v i n c e of Nova Scotia. Ex- c e s s i v e d i s p l a c e m e n t and c r a c k i n g of c o n c r e t e had been o b s e r v e d o v e r m a n y y e a r s by t h e Nova Scotia P o w e r C o m m i s s i o n i n t h e i r h y d r a u l i c s t r u c t u r e s . S e v e r a l independent investigations had been m a d e but t h e c a u s e r e m a i n e d u n c e r t a i n . The a c t u a l expansion was m e a s u r e d i n the field o v e r m a n y y e a r s by t h e C o m m i s s i o n and was o b s e r v e d t o b e exceedingly slow. Except f o r the c l e a r - c u t c a s e s , t h e r e s u l t a n t d e t e r i o r a t i o n of c o n c r e t e often could not b e distinguished f r o m , f o r example, f r o s t action. P e t r o g r a p h i c and o t h e r
evidence indicated t h a t a n a l k a l i - a g g r e g a t e r e a c t i o n was probably r e s p o n s i b l e .
T o s o m e d e g r e e t h e s l o w n e s s of t h e field r e a c t i o n could be a t t r i b u t e d t o f a i r l y low annual a v e r a g e t e m p e r a t u r e s . T h e o b j e c t s of t h e p r e s e n t s t u d y w e r e to d e t e r m i n e : ( a ) whether i t was an a l k a l i - a g g r e g a t e r e a c t i o n , ( b ) t h e r o c k t y p e o r t y p e s r e s p o n s i b l e , ( c ) t h e p r e v e n t i v e m e a s u r e s , ( d ) t h e extent of t h e p r o b l e m , and ( e ) t h e m e c h a n i s m . T h i s p a p e r i s t h e f i r s t of four p a p e r s t h a t d e s c r i b e i n condensed f o r m t h e f i v e - y e a r study and follows an e a r l i e r , p r e l i m i n a r y r e p o r t on p r o g r e s s during t h e investigation ( 1 ) . T h e s u b s e q u e n t p a p e r s will d e s c r i b e field and p e t r o g r a p h i c s t u d i e s , l a b o r a t o r y s t u d i e s of volume change, and c h a r a c t e r of t h e r e a c t i o n .
M a t e r i a l s and Methods
The r o c k types s e l e c t e d for study w e r e m a i n l y t h o s e t h a t w e r e found t o p r e d o m i n a t e in field c o n c r e t e s a s d e t e r m i n e d f r o m c o r e s and f r o m known s o u r c e s of c o n c r e t e a g g r e g a t e . T h e o r i g i n , n a t u r e , and r e l a t i v e abundance of t h e s e r o c k t y p e s a r e d e s c r i b e d i n a second p a p e r . A t o t a l of 7 5 c o n c r e t e c o r e s w e r e t a k e n f r o m field s t r u c t u r e s ; 48 r o c k s , 5 b a l l a s t s and 6 s a n d s f r o m a c r o s s mainland Nova Scotia w e r e studied. Rocks and s a n d s t h a t w e r e of doubtful quality a s c o n c r e t e a g g r e g a t e , f r o m t h e point of view of conventional t e s t s , w e r e not included i n t h e sampling. Two r e f e r e n c e c o a r s e a g g r e g a t e s and two r e f e r e n c e f i n e a g g r e g a t e s f r o m outside t h e Appalachian region, and
V o l . 3, N o . 1 5 7 A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE
with known p e r f o r m a n c e r e c o r d s , w e r e included a s controls. The scope of
the project did not p e r m i t evaluation of new s o u r c e s of c o n c r e t e aggregate
considered t o be nonreactive.
The alkali contents of the t h r e e n o r m a l portland c e m e n t s used in t h e study a r e given in Table I. T o obtain a l k a l i contents exceeding the 0. 88 p e r c e n t maximum in t h e s e c e m e n t s , e x t r a alkali, usually sodium hydroxide, was added t o the mixing w a t e r , using t h e medium alkali cement a s t h e b a s e in m o s t c a s e s .
Table I
Alkali Contents of Cements
-
As P e r c e n t a g e by Weight of Cement Total, Cement N a 2 0 K 2 ° calculated a s Na 0 2 Low alkali 0. 1 4 0. 30 0. 34 Medium alkali 0. 2 0 0. 78 0 . 71 High alkali 0. 27 0. 9 3 0. 88Expansivity was determined by t h r e e length change methods: a m o d i - fied f o r m of the ASTM C227 m o r t a r b a r t e s t (2), a modified f o r m of the ASTM C586 rock cylinder t e s t ( 3 ) , and a c o n c r e t e p r i s m t e s t ( 4 ) . T h e m o d i -
fications involved mainly methods of a c c e l e r a t i o n n e c e s s i t a t e d by the e x t r e m e slowness of the reaction. T h i s added a c c e l e r a t i o n was achieved by higher conditioning t e m p e r a t u r e , i n c r e a s e d a l k a l i content t o supplement t h a t in t h e cement, and i n c r e a s e d concentration of potentially r e a c t i v e r o c k types in each t e s t aggregate. Special t e s t s w e r e c a r r i e d out with KOH instead of NaOH.
Besides t h e m a i n t e s t p r o g r a m involving variations in t e m p e r a t u r e , alkali content, and concentration of r e a c t i v e rock type, other f a c t o r s w e r e
studied, including the effect of fly a s h and pozzolan, r e s t r a i n i n g s t e e l , and cycles of wetting and drying. Studies w e r e m a d e of physical p r o p e r t i e s such a s i n t e r n a l s u r f a c e a r e a , porosity, and specific gravity. Use w a s m a d e of
x - r a y and electron m i c r o s c o p e techniques. Not a l l of t h e t e s t data can be reported because of s p a c e limitations.
ALKALI AGGREGATE REACTION, EXPANSION, CONCRETE
Vol.
3,
No.
1
Typical T e s t Results
Of t h e numerous r o c k types p r e s e n t in the Appalachian region, of which Nova Scotia i s a p a r t , those shown by length change t e s t s t o be a l k a l i - expansive a r e shown in Table I1 along with t h o s e showing no expansivity. Within each group and within each r o c k type w e r e considerable v a r i a t i o n s in d e g r e e of alkali-expansivity. T h e l a s t t h r e e shown o c c u r r e d in both catego- r i e s . Concurrent studies of c o n c r e t e field c o r e s indicated, on the b a s i s of c r a c k i n g and other evidence, good a g r e e m e n t with r e s u l t s of length change studies in determining the above classification.
Table I1
G e n e r a l Classification of Nova Scotia Rock Types Investigated
It i s i m p o r t a n t t o note that a r o c k c l a s s i f i e d a s a greywacke o r a Highly Alkali Expansive
greywackes a r gillit e s phyllite s
phyllite, for example, contains m a n y r o c k types in v a r y i n g proportions, Non -Alkali Expansive
pink graphitic g r a n i t e s b a s a l t s
a r k o s e s sandstones
dolomitic l i m e stone
syenite xenoliths in a n acid i n t r u s i v e
m a s s i v e milky q u a r t z amphibolit e
s o m e alkali-expansive and s o m e not. Examples of compositional c h a r a c t e r - q u a r t z i t e s
s c h i s t s rhyolites
i s t i c s a r e given in the second p a p e r in t h i s s e r i e s .
1. M o r t a r B a r T e s t s
Some 2000 m o r t a r b a r s , m a d e t o ASTM b a r dimensions ( 1 by 1 by
1 1 i in. (25 by 25 by 285 m m ) ) , w e r e conditioned in vari'ous ways and m e a - s u r e d for length change, in s o m e c a s e s f o r a s long a s four y e a r s . T r i p l i -
V o l . 3, N o . 1
A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE
c e s s i v e when it reached o r exceeded 0. 05 p e r c e n t ( l i n e a r ) . The slowness of t h e reaction compared with m o s t alkali-silica r e a c t i o n s described in the l i t e r a t u r e r e q u i r e d different c r i t e r i a of t i m e v e r s u s d e g r e e of expansion. Final selection was based on p e r f o r m a n c e in l a b o r a t o r y and field.
F i g u r e 1 shows typical expansion r e s u l t s for m o r t a r b a r s c u r e d over water in sealed containers. T h e c u r v e s show that greywacke and a r g i l l i t e
FIG. 1
Typical m o r t a r b a r expansion a t 100' F (38" C) (ASTM C227) with Nova Scotia rocks a s aggregate and low alkali cement (0. 3 40/0), medium alkali cement (0. 710/0), high alkali cement ( 0 . 88%), and t h e medium a l k a l i cement plus additions of NaOH. ( T o t a l a l k a - l i s calculated a s p e r c e n t Na 0 . )
2
Moist-cured in sealed contain- e r s . - R E F E R E N C E - - P 7 7 0 2 4 4 8 7 2 9 6 1 2 0 0 2 4 4 8 7 2 9 6 1 2 0 1 4 4 T I M E , W E E K S
produce significantly high alkali -expansivity with t h e higher alkali concentra- tions, a s against no significant expansions for t h e a r k o s e o r r e f e r e n c e a g g r e - gate
.
F i g u r e 2 shows typical expansion v e r s u s t i m e c u r v e s with t e m p e r a - t u r e a s a variable. T h e change in r a t e and d e g r e e of expansion from 1 0 0 ° F (37. 8 ° C ) t o 1 2 5 ° F (51. 7 ° C ) was generally quite pronounced f o r rock types shown t o be alkali-expansive in other t e s t s . Except f o r s m a l l i n c r e a s e s in a few c a s e s , expansions w e r e not e x c e s s i v e when low alkali cement was used, even a t 150" F (64. 4 ° C ) . Studies of t h i s n a t u r e m a d e it p o s s i b l e t o develop time-length change c r i t e r i a for t e s t p u r p o s e s .
M o r t a r b a r t e s t s w e r e c a r r i e d out i n which the p e r c e n t a g e s of Nova Scotia (N. S. ) rock in t h e t o t a l aggregate ( m a d e up with a non-alkali expansive sand) w e r e 100, 65, 35 and 4. Twenty-six r o c k s a m p l e s w e r e studied. In 3 c a s e s the maximum expansion, 0. 05 p e r c e n t o r m o r e at 48 weeks, o c c u r r e d with 35 percent N. S. aggregate ( a n i m p u r e g r a n u l a r quartzite, a rhyolite and a heterogeneous m i x t u r e ) . In 8 c a s e s the maximum expansion o c c u r r e d
A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE V o l . 3, N o .
1
0 2 0 4 0 6 0 8 0 1 0 0 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 T I M E , W E E K S FIG. 2 Effect of c u r i n g t e m p e r a t u r e on e x p a n s i o n of m o r t a r b a r s m a d e with Nova S c o t i a a g g r e g a t e s ; with low a l k a l i c e m e n t (LA, 0. 34%) and h i g h a l k a l i c e m e n t (HA, 0. 88%). M o i s t-
c u r e d i n s e a l e d c o n t a i n e r s a t t e m p e r a t u r e s s t a t e d . with 65 p e r c e n t N. S. a g g r e g a t e ( a phyllite, a n a r g i l l i t e , a h e t e r o g e n e o u s combination, 3 g r e y w a c k e s and 2 q u a r t z i t e s ) . In 7 c a s e s t h e m a x i m u m e x - p a n s i o n o c c u r r e d with 100 p e r c e n t N. S. r o c k ( a p h y l l i t e , a r h y o l i t e , 3 g r e y - w a c k e s , and 2 q u a r t z i t e s ) . A c h e r t y a g a t e p r o d u c e d m a x i m u m e x p a n s i o n when p r e s e n t a s 4 p e r c e n t of t o t a l a g g r e g a t e . T h e r e m a i n i n g 7 s a m p l e s did not p r o d u c e e x c e s s i v e expansion when p r e s e n t in a n y of t h e s e p r o p o r t i o n s .
M o r t a r b a r s t u d i e s showed t h a t i n g e n e r a l t h e expansion r a t e i n - c r e a s e s with i n c r e a s e i n a v e r a g e p a r t i c l e s i z e of a l k a l i - e x p a n s i v e r o c k s . T h e effect is not c o n s i d e r e d sufficient t o u s e a g r a d i n g d i f f e r e n t t o t h a t of ASTM C227.
M o r t a r b a r t e s t s w e r e m a d e t o s t u d y s u c h f a c t o r s a s effect of t y p e of a l k a l i and effect of m o i s t - d r y cycling. Low a l k a l i c e m e n t w a s u s e d with added KOH and with added NaOH t o b r i n g t h e t o t a l a l k a l i c o n t e n t s t o t h a t of a h i g h a l k a l i c e m e n t (1. 0070 a s Na 0). In t h e s e t w o c a s e s t h e r e w a s n o
2
e s s e n t i a l d i f f e r e n c e i n r a t e and d e g r e e of e x p a n s i o n of a l k a l i - e x p a n s i v e Nova S c o t i a r o c k s . T h i s i s not i n a g r e e m e n t with findings of t h e r o c k c y - l i n d e r t e s t , noted in s e c t i o n ( 3 ) .
I n t e r m i t t e n t d r y i n g d u r i n g m o i s t c u r i n g g r e a t l y r e t a r d e d t h e e x p a n - s i o n and i n t h i s r e g a r d t h e r e a c t i o n is s i m i l a r t o o t h e r a l k a l i - a g g r e g a t e
V o l . 3, No. 1
A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE
r e a c t i o n s . In t h e s e m a n y t e s t s only r a r e l y did t h e m o r t a r b a r s exhibit exudations o r popout s .
2. C o n c r e t e P r i s m T e s t s
About 380 c o n c r e t e p r i s m s , 3 by 3 by 11 in. ( 7 5 by 75 by 275 m m ) ,
w e r e m a d e with r o c k s s u s p e c t e d of a l k a l i - e x p a n s i v i t y when used a s c o a r s e a g g r e g a t e and a sand f r e e f r o m r e a c t i v i t y . In each c a s e , an additional
s a m p l e w a s m a d e i n which t h e s u s p e c t e d a l k a l i - e x p a n s i v e r o c k constituted both t h e c o a r s e and t h e fine a g g r e g a t e . T h e s e r e s u l t s a r e not r e p o r t e d a s t h e y w e r e of t h e s a m e g e n e r a l o r d e r a s t h o s e m a d e with t h e n e u t r a l s a n d .
Twenty-six r o c k types w e r e studied in one s e r i e s ; c o n t r o l s a m p l e s m a d e with i m p o r t e d , non-expansive a g g r e g a t e w e r e u s e d in each s e t of t e s t s . T h e m i x w a s designed f o r 3500 p s i a t 28 d a y s ; s l u m p w a s 2 t o 3 in. (50 t o 75 m m ) , m a x i m u m s i z e c o a r s e a g g r e g a t e w a s 3/4 in. ( 1 9 m m ) , and w a t e r
-
cement r a t i o 0. 60 + 0 . 02. Duplicate o r t r i p l i c a t e s a m p l e s w e r e subjected t o t e s t . Among t h e v a r i a b l e s w e r e a l k a l i content, t e m p e r a t u r e , pozzolan o r fly a s h a d m i x t u r e , and r e s t r a i n i n g s t e e l . Changes i n length and e l a s t i c p r o p e r t i e s ( t h e l a t t e r d e t e r m i n e d by n o n d e s t r u c t i v e sonic t e s t s ) , w e r e o b -s e r v e d on m o s t of t h e s a m p l e s . D e s t r u c t i v e s t r e n g t h t e s t s w e r e p e r f o r m e d on one s e r i e s .
F i g u r e 3 shows t y p i c a l expansion c u r v e s of c o n c r e t e p r i s m s m a d e with 4 different c o a r s e a g g r e g a t e s . Low, m e d i u m , and high a l k a l i c e m e n t s w e r e used and conditioning w a s done a t 73 and 1 0 0 ° F (23 and 3 8 ° C ) .
T h e c o n c r e t e s m a d e with greywacke and a r g i l l i t e c o a r s e a g g r e g a t e show a high d e g r e e of a l k a l i - e x p a n s i v i t y a s a g a i n s t no significant expansion for t h o s e m a d e with t h e h e t e r o g e n e o u s r o c k . The r e s u l t s of t h e s e c o n c r e t e p r i s m t e s t s c o r r e l a t e d well with t h o s e of t h e m o r t a r b a r s e r i e s .
Twenty-four c o n c r e t e m i x e s w e r e m a d e in which 25% by weight of t h e cement w a s r e p l a c e d by fly a s h and by a p r o v e n , a c t i v e pozzolan. A l k a l i - nity w a s i n c r e a s e d by using t h e m e d i u m a l k a l i c e m e n t and adding sodium
hydroxide t o give a t o t a l a l k a l i of 1. OOpercent, calculated a s Na 0. In one s e t 2
of m i x e s only t h e a d m i x t u r e r e p l a c e m e n t w a s m a d e ; i n t h e o t h e r t h e a d m i x t u r e r e p l a c e m e n t was accompanied by an addition of sodium hydroxide t o a value
V o l . 3, No. 1 A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE
0 1 , L G R E Y W A C K E +
$
A R G I L L I T E H E T E R O G E N E O U S X N O N - R E A C T I V E R E F E R E N C E 0 2 0 4 0 6 0 8 0 1 0 0 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 T I M F . W E E K S FIG. 3Linear expansion of 3 by 3 by 11 in. (75 by 75 by 275 m m ) c o n c r e t e p r i s m s made with Nova Scotia r o c k s a s c o a r s e aggregate with low alkali cement (LA, 0. 340/0), medium alkali (MA, 0.7 1%) and high alkali (MA, 0. 719'0 with added NaOH to 1. 0070 total alkali calculated a s Nai;O).
Fog room at 7 3 ° F ( 2 3 ° C ) o r 1 0 0 ° F ( 3 8 ° C ) i n sealed containers.
equivalent t o 1.00 percent by weight of alkali, based on cement plus pozzolan o r fly ash. F i g u r e 4 shows length change r e s u l t s for an alkali-expansive greywacke. The v e r y effective suppression of expansion by the m i n e r a l ad- m i x t u r e s shown h e r e was a l s o demonstrated for a number of other a l k a l i - expansive r o c k types used in t h i s s e r i e s .
3. Rock Cylinder T e s t s
An extensive investigation was m a d e to d e t e r m i n e if the ASTM C586 t e s t , developed f o r alkali-carbonate rock reactions, would be equally useful in a s s e s s i n g the type of alkali-aggregate reaction occurring in Nova Scotia. This was shown t o be the c a s e . About 1200 rock cylinders, cored f r o m Nova Scotia rocks and f r o m r e f e r e n c e rocks, w e r e i m m e r s e d in sodium hydroxide solutions of various concentrations at different t e m p e r a t u r e s and m e a s u r e d periodically for length change.
A s p e c i a l m i c r o m e t e r was developed t o minimize inaccuracies that might develop over the lengthy t e s t p e r i o d s . Wherever possible, r o c k Sam
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p l e s w e r e cored in t h r e e mutually orthogonal directions. Expansion r e s u l t s usually differed because of anisotropy but the a v e r a g e of the expansions inV o l . 3, No.
1
A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE I I I I I I I I I I I I I I I I I I I I I I I - - O,O, 2 5 % R E P L A C E M E N T O F C E M E N T
-
--
. , A , 2 5 % R E P L A C E M E N T A N D W I T H - F U R T H E R A D D E D N a O H T O - - T O T A L A L K A L I I N N O R M A L M I X - - N O R M A L M E T A G R E Y W A C K E C O A R S E A G G R E G A T E I N-
C O N C R E T E P R I S M S . M E D I U M ( 0 . 7 1 % AS N a 2 0 ) A L K A L I C E M E N T P L U S N o O H T O 1 . 0 0 % T O T A L - N a 2 0 ( 1 0 0 % R H , 1 0 0 ° F ( 3 8 ° C ) )-
--
- - - - -- - W I T H F L Y A S H - - --
1 1 1 1 1 l 1 1 1 1 1 1 1 l 1 1 1 l l l l I I I T I M E , W E E K S FIG. 4Effect of l i n e a r expansion of c o n c r e t e p r i s m s m a d e with a m e t a g r e y w a c k e c o a r s e a g g r e g a t e with 25% of c e m e n t r e p l a c e d by a c a l c i n e d volcanic tuff
p o z z o l a n o r a fly a s h .
t h e t h r e e d i r e c t i o n s w a s t a k e n t o b e t h e s i g n i f i c a n t v a l u e . All expansion
d a t a r e p o r t e d h a v e b e e n c o r r e c t e d f o r t h e s m a l l , n o r m a l expansions due t o s o a k i n g i n w a t e r . C o m p a r i s o n of t e s t r e s u l t s with t h o s e f r o m o t h e r length
c h a n g e t e s t s led t o t h e adoption of 0. 056 p e r c e n t v o l u m e t r i c expansion a s
t h e c r i t i c a l v a l u e
F i g u r e 5 shows t y p i c a l volume change r e s u l t s f o r r o c k c y l i n d e r s at two t e m p e r a t u r e s f o r s e v e r a l c o n c e n t r a t i o n s of sodium h y d r o x i d e . T h e g r e y w a c k e h e r e exhibits a h i g h d e g r e e of a l k a l i - e x p a n s i v i t y ; t h e r h y o l i t e d o e s not u n d e r t h e s e conditions of t e s t . T h e extensive d a t a of t h i s type developed i n t h e s e t e s t s showed good c o r r e l a t i o n with t h o s e f r o m m o r t a r b a r s and c o n c r e t e p r i s m s . In e x p e r i m e n t s w h e r e r o c k c y l i n d e r s w e r e i m m e r s e d i n KOH i n s t e a d of NaOH, e x p a n s i o n s w e r e v e r y m u c h l e s s . T h i s w a s c o n t r a r y t o t h e e x - p e r i m e n t s with m o r t a r b a r s a l r e a d y d e s c r i b e d . 4. O t h e r T e s t s F o u r t e e n r o c k s a m p l e s t h a t had b e e n shown by o t h e r t e s t s t o b e
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I I I I I I I I I I I I I I I I I
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- - G R E Y W A C K E - - R O C K C Y L I N D E R S - - I N N a O H A T 7 3 O F ( 2 3 O C ) - - - - I I I I I I I I I 1 G R E Y W A C K E R O C K C Y L I N D E R S I N N a O H A T 1 0 0 ° F ( 3 8 O C )/
T I M E , W E E K S FIG. 5 T y p i c a l e x p a n s i o n s of r o c k c y l i n d e r s i n v a r i o u s c o n c e n t r a t i o n s of NaOH at 7 3 ° F ( 2 3 ° C ) and 100" F ( 3 8 ° C ) a l k a l i - e x p a n s i v e w e r e s u b j e c t e d t o t h e ASTM Quick C h e m i c a l T e s t ,C289-66. On t h e b a s i s of t h i s t e s t , about half would b e c l a s s e d a s a l k a l i - r e a c t i v e , t h e o t h e r half a s innocuous, indicating t h e inapplicability of t h i s t e s t f o r t h e Nova S c o t i a r o c k s . T h e Conrow t e s t , ASTM C342-67, a l s o c a r r i e d out on r e a c t i v e s a m p l e s , did not p r o d u c e r e s p o n s e . R i m f o r m a t i o n w a s r a r e and g e l exudation did not often o c c u r i n l a r g e a m o u n t s i n c a s e s of
e x c e s s i v e expansion of t h e c o n c r e t e o r m o r t a r . T h e s e and o t h e r r e s u l t s t o b e d i s c u s s e d in s u b s e q u e n t p a p e r s s u g g e s t e d s t r o n g l y t h a t t h e Nova S c o t i a r e a c t i o n i s d i f f e r e n t i n s o m e i m p o r t a n t r e s p e c t s f r o m t h e c l a s s i c a l a l k a l i - s i l i c a r e a c t i o n . D i s c u s s i o n T h o r o u g h a n a l y s e s w e r e m a d e of t h e l e n g t h - c h a n g e d a t a f r o m t h e m o r t a r b a r , c o n c r e t e p r i s m , and r o c k c y l i n d e r s t u d i e s t o d e t e r m i n e t h e d e g r e e of c o r r e l a t i o n and t h e r e l i a b i l i t y of t h e v a r i o u s p r o c e d u r e s u s e d . Of p a r t i c u l a r i m p o r t a n c e w e r e t h e f a c t o r s of t e m p e r a t u r e , a l k a l i content, c o n c e n t r a t i o n of r o c k t y p e , and v a r i a b l e c o m p o s i t i o n within e a c h r o c k t y p e . A g r e e m e n t b e t w e e n t h e t h r e e t y p e s of t e s t s in r a t i n g a r o c k a s a l k a l i - e x - p a n s i v e o r not w a s about 80 p e r c e n t ( s e e Appendix A). T h e m o s t c o n s i s t e n t r e s u l t s w e r e obtained f o r g r e y w a c k e s , a r g i l l i t e s and p h y l l i t e s ; a g r e e m e n t
V o l . 3, N o . 1
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w a s not a s good f o r t h e q u a r t z i t e s , m i c a c e o u s s c h i s t s and r h y o l i t e s . H e t e r - o g e n e o u s r o c k s ( t h o s e with no p r e d o m i n a t i n g r o c k t y p e ) b e h a v e d c o n s i s t e n t l y i n r e l a t i o n t o t h e t o t a l of a l k a l i - e x p a n s i v e r o c k t y p e s p r e s e n t . In a s s e s s i n g r e l i a b i l i t y , e x t r a weight w a s given t o r e s u l t s obtained u n d e r only m o d e r a t e l y a c c e l e r a t i n g c o n d i t i o n s . T h e p r o c e d u r e r e c o m m e n d e d f o r e v a l u a t i n g a n a g g r e g a t e s o u r c e i n Nova S c o t i a , b a s e d on t h i s i n v e s t i g a t i o n , c a n be s u m m a r i z e d as follows: ( a ) E x a m i n a t i o n of t h e p e r f o r m a n c e of f i e l d c o n c r e t e i n a r e a i n q u e s t i o n ; s u c h e v a l u a t i o n would i n d i c a t e t o what d e g r e e s p e c i a l t e s t i n g f o r a l k a l i - a g g r e g a t e r e a c t i v i t y need b e c o n s i d e r e d . ( b ) C o n v e n t i o n a l a g g r e g a t e t e s t s t o e n s u r e t h a t n o r m a l s p e c i f i c a t i o n r e q u i r e - m e n t s a r e m e t . ( c ) P e t r o g r a p h i c e x a m i n a t i o n and i n t e r p r e t a t i o n by a p e t r o g r a p h e r with e x p e r i e n c e with a l k a l i - a g g r e g a t e r e a c t i o n s . ( d ) If p e t r o g r a p h i c a n a l y s e s i n d i c a t e a h i g h , p e r c e n t a g e of r o c k t y p e s d e s i g n a t e d in t h i s s t u d y a s p o t e n t i a l l y a l k a l i - e x p a n s i v e , no f u r t h e r t e s t - i n g n e e d b e done, and one o r m o r e of t h e r e c o m m e n d e d p r e v e n t i v e m e a s u r e s should b e t a k e n . ( e ) If p e t r o g r a p h i c a n a l y s e s i n d i c a t e l i t t l e o r no s u c h r e a c t i v e r o c k s p r e s e n t , t h e u s u a l c o n c r e t e p r a c t i c e m a y b e followed. ( f ) If a n a l y s e s l e a v e doubt a s t o a l k a l i - r e a c t i v i t y , l e n g t h c h a n g e t e s t i n g should b e done t o d e t e r m i n e e x t e n t of p r e v e n t i v e a c t i o n t o b e t a k e n . A p r e l i m i n a r y p r o b e t e s t of v a r i o u s s t r a t a i n a q u a r r y t h a t c a n be r e c o m m e n d e d t o give a n a s s e s s m e n t in a m i n i m u m a m o u n t of t i m e i s :
(i) 16-week r o c k c y l i n d e r t e s t a t 1 2 5 ° F ( 5 2 ° C ) i n a 2 . 67M NaOH solution, with a c r i t i c a l m e a n e x p a n s i o n l i m i t of 0 . 056 p e r c e n t , o r ,
(ii) 16-week m o r t a r b a r t e s t a t 150" F (64" C ) with a h i g h a l k a l i c e m e n t containing not l e s s t h a n 0. 90 p e r c e n t t o t a l a l k a l i c a l c u l a t e d a s Na 0
2 ( c r i t i c a l e x p a n s i o n l i m i t of 0. 05 p e r c e n t ) .
F o r g r e a t e r r e l i a b i l i t y but r e q u i r i n g m o r e t i m e , t h e following p r o - c e d u r e i s r e c o m m e n d e d :
A L K A L I AGGREGATE R E A C T I O N , E X P A N S I O N , CONCRETE
V a l . 3 , N o . 1
(iii) 72 -week m o r t a r b a r t e s t a t 100"
F
( 3 8 ° C ) with 1. 00 p e r c e n t t o t a l a l k a l i and a c r i t i c a l length change limit of 0. 05 p e r c e n t , o r ,( i v ) 120-week c o n c r e t e p r i s m t e s t a t 1 0 0 ° F ( 3 8 ° C ) with a high a l k a l i c e m e n t of t o t a l a l k a l i ( a s Na 0) not l e s s than 0. 90 percent ( c r i t i c a l length
2
change l i m i t of 0. 05 p e r c e n t ) . An e s s e n t i a l f a c t o r i n any of t h e s e t e s t s i s t h e u s e of at l e a s t one c a r e f u l l y chosen, non-alkali-expansive c o n t r o l a g g r e g a t e .
P r e v e n t i v e m e a s u r e s t o be u s e d in t h e field, a s shown in t h i s study, a r e t h e s a m e a s for the well-known a l k a l i - s i l i c a r e a c t i o n . T h e s e a r e :
( a ) low a l k a l i c e m e n t of not m o r e than 0. 60 p e r c e n t a l k a l i , calculated
(b) substitution of p a r t of n o r m a l high a l k a l i c e m e n t by a f l y a s h o r a proven pozzolan, o r , ( c ) w h e r e p o s s i b l e , design of s t r u c t u r e t o p e r m i t drying of c o n c r e t e a f t e r c u r i n g . S u m m a r y and Conclusions C e r t a i n r o c k t y p e s i n Nova S c o t i a , o t h e r w i s e acceptable f o r c o n c r e t e a g g r e g a t e , w e r e shown t o be alkali-expansive t o a n e x c e s s i v e d e g r e e when used in conjunction with a high a l k a l i c e m e n t . T h e length-change expansion t e s t s confirmed field o b s e r v a t i o n s and r e s u l t s of examination of field con-
c r e t e s . Culprit r o c k s w e r e greywackes, a r g i l l i t e s , phyllites, and s o m e of the q u a r t z i t e s , s c h i s t s and r h y o l i t e s . A highly m o i s t environment was shown t o be n e c e s s a r y for t h i s r e a c t i o n t o develop t o any s e r i o u s extent.
A c c e l e r a t e d methods of evaluation w e r e developed b e c a u s e of t h e v e r y slow r e a c t i o n . P r e v e n t i v e m e a s u r e s , d e m o n s t r a t e d in t h e l a b o r a t o r y , a r e t h e u s e of a low a l k a l i c e m e n t o r a pozzolan o r fly a s h .
Acknowledgem ent
T h i s investigation was initiated by t h e Nova Scotia P o w e r C o m m i s s i o n
which h a s , with added financial support f r o m o t h e r p r o v i n c i a l a g e n c i e s , been t h e m a i n s p o n s o r . Most of t h e s t u d i e s w e r e c a r r i e d out a t t h e Nova Scotia
T e c h n i c a l College by t h e f i r s t a u t h o r . T h e Division of Building R e s e a r c h of t h e National R e s e a r c h Council of Canada c a r r i e d out t h e detailed p e t r o - g r a p h i c a n a l y s e s and w a s r e s p o n s i b l e for continuing advice and a s s i s t a n c e .
Vol. 3 , No. 1
A L K A L I AGGREGATE REACTION, EXPANSION, CONCRETE
T h e p r o j e c t w a s a d m i n i s t e r e d by, s u c c e s s i v e l y , t h e Nova S c o t i a R e s e a r c h Foundation and t h e Atlantic I n d u s t r i a l R e s e a r c h Institute. T h e r e s e a r c h r e s u l t s a r e being published t h r o u g h c o u r t e s y of 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 .
R e f e r e n c e s
1. M. A. G. Duncan and E. G. Swenson, Investigation of C o n c r e t e Expansion i n Nova Scotia. T h e P r o f . Eng. i n Nova S c o t i a , Vol. 10, NO. 2, M a y
1969, p . 16-19.
2. P. K. Mukherjee, M.A.G. Duncan, M. R. F o r a n and A . S a m a n t a . T h e E x p a n s i v e Behaviour of M o r t a r B a r s P r e p a r e d f r o m Alkali- 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 . Atlantic Ind. R e s . Inst.
,
Halifax, Sept. 1970, p . 1-28.3. M. A. G. Duncan, C o r r e l a t i o n of F i e l d and L a b o r a t o r y Evidence of Alkali-Silica R e a c t i v i t y i n Nova S c o t i a C o n c r e t e . P h . D. T h e s i s , Nova S c o t i a Tech. Coll.
,
1970, p. 1-544.4. S.S. G u r j a r , M. A. G. Duncan, and P. K. M u k h e r j e e . P e r f o r m a n c e of C o n c r e t e P r i s m s m a d e f r o m A l k a l i - E x p a n s i v e Nova S c o t i a A g g r e g a t e s . Atlantic Ind. R e s . Inst.
,
Halifax, Sept. 1970, p. 1-27,ALKALI AGGREGATE REACTION, EXPANSION, CONCRETE
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3,
No.
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A P P E N D I X A A L K A L I - E X P A N S I V I T Y O F N O V A S C O T I A A G G R E G A T E S A S D E T E R M I N E D BY TEST M E T H O D S A N D C O N D I T I O N S S E L E C T E D F O R E V A L U A T I O N P U R P O S E S ( C R I T I C A L T I M E - E X P A N S I O N V A L U E S I N E A C H C A S E G I V E N I N T E X T ) M i x t u r e s o f T e s t S a n d a n d N e u t r a l S a n d g i v i n g M a x i m u m E x p a n s i o n E X P A N S I O N : E = E x c e s s i v e , B = B o r d e r l i n e , N = N o t E x c e s s i v e . C o n t i n u e d A G G R E G A T E W H I T E Q U A R T Z I T E F E L D S P A T H I C Q U A R T Z I T E M E T A - F E L D S P . Q U A R T Z I T E F E L D S P A T H I C Q U A R T Z I T E F E L D S P A T H I C Q U A R T Z I T E E E E E N N - E E E E B E E E N -E E E E - E - E E B N N N E E E E E E E N B E NV o l . 3, N o . 1 A L K A L I AGGREGATE R E A C T I O N , E X P A N S I O N , CONCRETE A P P E N D I X A ( C o n t i n u e d ) F E L D S . Q U A R T Z I T E A N D A R G I L L I T E Q U A R T Z I T E F E L D S P A T H I C Q U A R T Z I T E M I L K Y Q U A R T Z I T E M A S S I V E M I L K Y Q U A R T Z E E A R K O S I C S A N D S T O N E F E L D S P A T H I C S A N D S T O N E B N N A R K O S E P O R P H Y R I T I C B A S A L T E N A M Y G D U L C I D A L B A S A L T E N N N S Y E M I T E X E N O L I T H I N A C I D I N T R U S I V E D O L O M I T I C L I M E S T O N E P Y R I T I F E R O U S S C H I S T O S E E E N - N N N - N -N B A N D E D R H Y O L I T E ( 1 ) P O R P H Y R . R H Y O L I T E ( 2 ) S P H E R O L R H Y O L I T E ( 2 ) M I X O F ( I ) , ( 2 ) A N D ( 3 ) R H Y O L I T E I M P U R E G R A N U L A R Q U A R T Z H E T E R O G E N E O U S
