alkalis in concrete
TRANSCRIPT
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I
Ser
TIS
National Research Conseil national
N2 d \t Council Canada
no 236
de recherches Canada
c.
BLDG
EVALU ATION OF TEST METHODS FOR ALKALI-AGGREGATE
REACTIV ITY
y P.E. Grattan-Bellew
Reprinted from
Danish Concrete Association
6th. International Conference
Alkalis in Concrete: Research and Practice
Technical University of Denmark
Copenhagen, 22-25 June 1 98 3
Proceedings, p. 303
314
N R - I S T I 1
BLDG.
RES.
L I B R A R Y
84
11- O
6
B I B L ~ O T H Z Q U E
Reth.
Bttim
N R I I S T
DBR Paper No. 1236
Division of Building Research
Price $1
OO
OTTAWA NRCC 23749
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L es msthodes d e s s a i d e l a r h c t i o n a l c a l i - g r a n u l a t comprennent
c e l l e s q u i p e rm e t t en t d e d e te rm in er l a r e a ct iv it e p o t e n t i e l l e
d u n g r an u l a r ( l e s s a i chimiqu e e t l a m6t hod e p et r o g r aph iq u e
propos ee pour d e terminer l a n g l e d ex t i nc t i on on du la to i r e du
q u a rt z ) e t c e l l e s q u i v i s e n t m esurer l e x p a n s i m d un
gr an u l a t dans l e b e ton (msthodes du p r i sme de b e ton, du bar re au
d e m o r ti e r e t d e l g p r o u v e t t e c y l in d r iq u e ). P l u s i e u r s
mo di f i ca t i on s on t e t5 apport ees l a m ethode chimique,
ASTM
C289 p ou r p r e nd r e en c o n si d e r a ti m l e s v a r i a t i o n s
r e g i on a le s d e s g r a n u l a t s . l
r i n r i n l A U e u e s
d e
mesu re d e l ex p a n s i f en
oeuvre. Pour t e n t e r Ye
s
d 1 accS l e r a t i o n o n t
s
d a n s d e s s o l u t i o r
1 au toc lavage . re
in terp r e t ees avec ,
_
6lev ees,
l
s e p r ~
n e s e p r o d u i r a n
atmosphgrique
.
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DANISH
CONCRETE ASSOCIATION
DBF
LK LIS
N CQMCRlETlE
Research
and
Practice
Paper reprinted from the
PROCEEDINGS
TECHNICAL UNIVERSITY
of Denmark
COPENHAGEN
22. 25.
J U N E 983
Editors: G M ldorn Steen Rostam
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EVALUATION OF TEST METHODS FOR ALKALI-AGGREGATE REACTIVITY
P.E. Grattan-Bellew
Di vis ion of Bui ldin g Research, Nati ona l Research Council Canada
Ottawa, Canada K1A OR6
ABSTRACT
Tes t methods f o r a l ka li - agg r egat e r e ac t i v i t y can be d i v ided i n t o t hose t ha t
de termine the po te nt i a l r e ac t iv i ty of an aggregate the chemica l t e s t and th e
proposed pe t rogr aphic method f o r de termining th e undula tory ex t in c t io n angle
of qua r tz) and those t ha t purp or t t o measure the expansi9i ty of an aggrega te
i n conc re t e conc r e t e p ri sm ,
mortar bar , and rock cy lin de r methods) .
Severa l
mo di fi ca tio ns have been developed f o r th e chemic al method, ASTM C289, t o tak e
i n t o accoun t r eg i on a l va r i a t i on s i n aggr ega te s . The main d i sadvan tage of t h e
methods measuring expansion
i s
t h a t they t ake a long t i m e
To t r y t o overcome
t h i s problem, va rio us methods of a cc el er at io n have been proposed, vary ing from
immersion of t h e s am ples i n s a l t s o l u t i o n a t a n e le v a t e d te mp er at ur e t o
auto clav ing. Autoclaving methods must be rega rded w it h some ca uti on , however,
because a t e lev ate d temperatures and pressures hydrothermal rea ct i on s occur
t h a t do no t t ake p l ace a t a tmospher ic pr e ssu re .
KEY WORDS:
Evalua t ion , Tes t s , Alka l i , Aggregate .
1.
INTRODUCTION
The i de a l method of de te r mi ni ng t h e po t e n t i a l a l k a l i expans i v i t y of an
aggregate i n concre te should be appl i ca ble t o a l l rock types , should be r ap id ,
t ak ing no more tha n a few days t o complete, and must g ive r e l i a b le r e su l t s .
The quest f o r t h i s t e s t has kept a number of rese arch ers busy fo r many yea rs ,
bu t l i k e t h a t of t h e a l chemi s t s be f o re them i t w i l l not succeed.
M v e r s i t y i n
th e composi tion, g ra in s iz e , and poros i ty, and the presence o r absence of
secondary cementing minerals i n rocks pre di ca te s aga ins t t h e development of a
univer s a l ly app l i cable , r ap id t e s t method. Some t e s t s , f o r example th e
conc re t e p ri sm method, a r e ap p l i cab l e t o a l l r ock t ypes bu t may t a ke s o l ong
t h a t t h e s t r u c t u r e w i l l be b u i l t b e fo r e t h e t e s t i s complete.
Other
t e s t s
l i k e t h e mor ta r ba r and t he chemi ca l methods, a r e s u i t a b l e f o r agg rega t es
e x h i b i t i n g 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 v i t y b u t n ot f o r r e a c t i v e c ar b on a te
aggregates. A s a re s u l t , a number of d i f fe re n t t e s t methods have been, and
continue t o be, developed. This review
w i l l
examine t he e f fe ct iv en es s and
l im i ta t io ns of ex i s t in g and proposed t e s t methods.
2. CHEMICAL TEST
The ch emic al method, ASTM
C 89 111, was developed a s a ra pi d means of
d i f f e re n t i a t in g between pot ent i a l l y r eac t ive and non-react ive s i l i ca-be ar ing
aggr ega t es . The c r i t e r i a f o r eva l ua t ion wer e devel oped from t h e r e su l t s of
p a ra l l e l s e t s of mor tar bar and chemical t e s t s on many aggregates f rom th e
Uni ted St at es 121. The rocks te st ed included some con tain ing opal , ch er t o r
chalcedony a s the re ac ti ve component and othe rs i n which vo lc an ic gla ss was
the reactive component.
As
t h e two main re ac ti ve components, op al and
vo l can i c g l a s s , cons i s t of c r yp t o c r ys t a l l i ne S i 02 and an a l umi nos i l i ca t e
g l a s s , r e spec t i ve l y ,
i t i s
s u r p r i s i n g t h a t one s e t of c r i t e r i a were fo und t o
be appropr ia t e f o r eva lua t ion of both types .
The problem of obta in ing meaningfu l va lues fo r th e d i sso lved s i l i c a Sc) and
t he r educ t ion i n a l ka l i n i t y Rc) a r e compli ca ted i f ca r bona t e s o r su l pha t e s ,
e .g., gypsum 131, a r e prese nt i n th e aggregate because they r ea ct wi th NaOH t o
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reduce
i t s
a l k a l i n i t y .
The values of Sc and Rc ar e a ls o very susc ept i b le t o
operator inf luence.
For example, i f th e sample i s not p roper ly s iz ed and a
significant amount of -150
u
m a te r i a l
i s
i nc lu de d i n t h e
t e s t
the value of
Sc w i l l be markedly increased. Grinding quar tz t o s iz e s
less
than about
100 u g r e a t l y i n c r e a s e s i t s s o lu b i l i t y F ig u re 1 ).
The phenolphthale in ind ic ato r does not g iv e a sharp end poin t and th e value
of Rc determined is thu s, t o some ex te nt , dependent on th e judgement of th e
operator. Soaie of th e problem inh eren t i n th e chemical
tes t
were discussed
by Dent Glasser and Kataoka 141.
Their main conclusion i s th a t the va lue of
Rc, as currently determined,
i s
ra th e r meaning less s inc e
i t
inc ludes
r ed uc ti on s i n bo th OH- and t he c o nc e nt ra t io n of ~ a +n t h e s o lu ti o n .
They
suggested th a t th e method should be a l te re d s o t ha t OH can be determined by a
pH meter and ~ a +y a sp ec tr os co pi c method.
The q u e st i o n a r i s e s a s t o t h e need t o d e t e r d n e t h e r ed uc ed a lk a l i n i t y , Rc;
i s de termina t ion of Sc a lone suf f ic ie n t f o r p red ic t i ng the po ten t ia l
re ac t i v i ty of an aggrega te? To inv es t iga te th i s ,
t e s t
r e s u l t s f o r a s e r i e s of
quar tz sands containing varying amounts of opal 121 were pl ot te d i n Figure 2;
i t i s e v ide n t t h a t e x pa ns io n of m o rt ar b a r s c o r r e l a t e s b e t t e r w i th t h e f a c to r
Rc/Sc than with Sc a lone, ind icat ing th at f or th ese aggregates
i t
i s b e t te r t o
determine both Rc and Sc.
I t
h a s been e s t a b l i s h e d t h a t t h e c r i t e r i a give n i n C289 a r e n o t a d e qu a te f o r
the evaluat ion of Icel and ic sands conta ining volcanic gl as s or of Danish f l i n t
g rave l s , f o r which l o w values of th e amount of d iss olved s i l i c a
are
i n d i c a t i v e
of po ten t ia l r eac t iv i ty . New c r i t e r i a were developed fo r th e i r eva lua t ion a s
fol low s pe rs on al comnunication, Hakon Olaf sson)
Icelandic sands:
non -re act ive Sc <I 00 nsnol/L
po te nt ia ll y re ac ti ve Sc 100 t o 200 mmol/L
r ea c t i v e Sc s200 mmol/L
Danish gravels:
non r e a c t i v e Sc <50 mmol/L
pot en t ia l ly reac t iv e Sc 50 t o 200 mmol /~
r e a c t i v e Sc >200 mmol/L
I n c o n t ra s t ,
i n Br i t a i n t he Thames Valley f l i n t g rav e l s y ie lded va lues of Sc
i n exce ss of 100 mmol/L y e t caused no problems i n con cr et e 131. I t appears
t h a t s e p a ra t e s e t s of
c r i t e r i a need t o be developed on a r eg io nal ba si s, even
f o r evalua tion of what ar e nominally t he same rock types.
I n t he late-ex pansive aggr egat es of th e Malmesbury Formation i n th e
Cape Peninsula of South Africa, i n which s tr ai ne d quartz i s t h e r e a c t i v e
component,
t h e c r i t e r i a s p e c i f i ed i n C289 a r e e f f e c t i v e f o r d i f f e r e n t i a t i n g
rea cti ve and non-reactive aggregates;
but i n th e Tygerberg Formation from th e
same reg ion lower val ues of Sc were obtaine d from re ac ti ve agg regat es.
The
resu l t s o f the chemical te s t on thes e aggregates, reported by Brandt,
Oberhols ter and Westra 151, a r e r ep lo t te d i n Figure 3.
It
i s e v id e nt t h a t t h e
dividing l in e between r eac t ive and non-reactive aggregates must l i e a t a value
of Sc between 35 and 50 nnnol/L.
I n Se r b ia t h e che mica l method, ASTM G289, used by Mitr ov iE and
~ u r i E 6 1 i n d i c a t e d t h a t t h e a g gr eg a te s a r e p o t e n t i a l l y r e a c t i v e a s d id t h e
mortar bar tes t ) , a l though no problems have been observed i n co ncret e.
There
a p p e a r s t o be some doubt concerning th e va li d it y of both methods f o r
eva lua t i ng these pa r t i c u l a r aggregates .
I n A u s t r a l ia , t h e c r i t e r i a s p e c i f i e d i n C289 a r e e v id e n t ly s a t i s f a c t o r y ;
they have been adopted s an Austra l ian s tandard, S 1141 Section 39, 1954.
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2 1 Discussion
T h e c h e d c a l
t e s t i s
the only rapid ,
currently
av ai lab le method, th at has
been thoroughly evaluated. With some m d i f i r a t i o n of th e c r i t e r i a used t o
def ine re ac t i ve aggrega tes , and i n co-n juac tion wi t h a pe t rograph ic
examination,
it
can
e
u se d t o e v a lu a t e t h e p o t e n t i a l r e a c t i v i t y o f a w id e
range of s i l ic eo us aggregates . Improvements might be made i n th e an al yt ic a l
p rocedures so tha t the reduc t ions i n OH- and i n ~ a re determined separate ly .
There
is
some
e v id e nc e t h a t d e te rm ina ti on o f d i s s o lv e d s i l i c a a lo n e i s
sufficient t o d i f fe re n t i a te between re ac t iv e and non-react ive aggregates .
Owing t o t h e w id e d iv e r s i t y i n the conposit lo-n gr a i n s i z e and perm eabi l i ty of
rocks,
it i s
most u n l i k e ly t h a t u n iv e r s a l l y a p p l i c a b l e c r i t e r i a c an be
deve loped t o d i f f e r en t i a t e between rea c t iv e and non- reac tive aggrega tes ;
ins tead , c r i t e r i a app l icab le t o spe c i f i ed rock types should be deve loped.
2.2 Modified ch em ical
test
A
d i f i e d c h e d c a l t e s t was d ev elop ed f o r e v a lu a t i n g t h e p o t e n t i a l
r e a c t i v i t y o f a g g re g a te s i n sh Sch les wig -lb lst ein reg ion of Germany. The
aggregate
i s
d iv id e d i n to two s i z e f r a c t i o n s : 1-2 mm and 2-4 mm These a r e
dige sted f n NaOH s ol ut io n f o r 60 d n a t BO C.
The
samples are
washed, dried,
and weigh t lo s s de te rmined ; t h i s represe n ts t he amount of s i l i c a d i s so lved ou t
by N H and gives,
i n p r i n c i p l e , a measure of t h e p o t e n t i a l r e a c t i v i t y of t h e
aggregate.
The l im i t a t i o n s of t h i s t e s t have been disc uss ed by Jensen,
Chatterji, Christensen, Thaulow and Gudmndsson 171. t would be applicable
o n ly t o a g g r eg a t es c o n t ain ing r e a c t i v e
s i l ica ,
i.e., opal,
cher t or chalcedapy
and possi bly a ls o t o aggregate composed of volc anic g lass .
3. MORTAR B R METHOD
The mo rt ar b a r t e s t , ASTM C227-8
/ 8 /
i s
t h e most widely used method of
eva lua t ing the po t en t ia l a lk a l i - rea c t iv i ty of aggrega tes .
A
number of
v a r i a t i o n s i n t h e m ethod o f e v a l ua t i ng t h e t e s t r e s u l t s a r e i n u s e by
di ff er en t organizat ion s . Despi te the a lmost univ ersa l acceptance of th e
mortar bar method,
i t
has several shortcomings: It u s u al l y t a k e s from s i x
months t o a ye ar t o complete,
except wi th some opal-bearing aggregates th at
can be evaluated i n about th re e months.
Such long lead
times
f requent ly do
not ex i s t be fore cons t ruc t ion
i s
s t a r te d , even i n major s t ru c t u r es fo r which
th e d u r a b i l i t y of t h e c o n c r et e i s of c r i t i c a l importance.
The evaluat ion of th e re ac t i v i ty of concrete aggregate by t h e mortar ba r
method assumes t ha t expansion of concrete i n the f i e l d cor re l a t es wi th
expansion of t e s t mortar bars . Although t h i s holds t r ue fo r some aggregates ,
th ere ar e exceptions. The carbonate aggregate from Kingston, Ontario , f o r
example,
shows much g re at er expansion i n co ncre te prisms than i n mortar bars ,
a s do late-expansive quartz-bearing aggre gates such a s Malmesbury aggregat e
from th e Cape Penin sula i n South Af ri ca and a greywacke from Nova S co ti a,
Canada 191 ( s ee Figu re 4, 73-50).
3.1 In te rp re ta ti on of observed expansion
Recommended c r i t e r i a fo r eva lua t ion of th e re su l t s of th e mor ta r ba r t e s t
a r e g iv en i n ASTM
C33-82,
Appendix XI.1.3 / lo /
I t
must be s t r ess ed t ha t
th es e a r e recommendations, not a mandatory pa r t of t h e stand ard. Although
t he y a r e f r e q ue n t ly i n t e r p r e t e d a s
limits,
t h i s
i s
i n c o r r e c t .
According t o C33, expansions a re t o be considered excess ive i f they exceed
0.05% a t thr ee months o r 0.10% a t s i x months; the three-month da ta should only
be used, however, when a six-month t e s t i s not possib le . The a l k a l i con ten t
of th e cement should be 0.6%, pr pref era bly 0.8%. With t h e hig h a l k a l i
cements now commonly i n use, an a l k a l i l e v e l of 1.0% o r g r e a t e r would be more
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ap pr o pr ia te . The problem wi th t he se recommended maximum pe rm is si b le
expansions i s
th a t they assume a fa s t r a t e of expans ion wi th a sh or t
i n i t i a t i o n p eri od .
slow ly expand ing agg re ga te may show mo rtar ba r
expans ions we l l below t he va lues cons ide red t o be de l e te r io us , accord ing t o
C33, but th e cont inuin g slow expansion
w i l l
e v e n t u a l l y l e a d t o e x c e s si v e
s t r e s s and cracking.
t y p i c a l example of exp ans ion of a morta r b ar made w it h Malmesbury
aggre gate and a cement con tai nin g 0.82 a l k a l i i s shown i n Figure 5 (pers onal
comnunication, R.E. Ob erh ols ter ) . Th is agg reg ate i s known t o ca use
de le t e r i ou s expans ion i n conc re te made wi th a h igh a l k a l i cement.
The problem
of eva l ua t i ng the re su l t s of expansion of morta r ba r s made wi th l a te ex pa ns iv e
agg reg ates h as a l s o been disc uss ed by Kennerly e t a l . 1111 and by Sims 131.
3.2 Corps of En gine ers
The C orps of Eng ine er s c r i t e r i a f o r e va lua t i on of t hz r e s u l t s of t he mor t ar
bar t e s t a re po ssi bly more ap pro pri ate than tho se recommended i n C33.
EM 1110-2-2000 1121 s t a t e s th a t expansion of 0.10 o r more a t any age shou ld
be considered de l e te r io us . An expansion of 0.05 or more a t s i x months may
a l so be cons ide red de le te r io us . When expans ions c los e t o the se
l i m i t s
a r e
recorded, th e tre nd of th e time-expansion curve should be taken in t o account.
T h i s
i s
i n l i n e wi th t h e concept of de te rmining the r a t e of expansion proposed
by Grattan-B ellew 191. Cracking of mortar b ar s i s generally observed when
expansion exceeds about 0.04 ; i f c racki ng i s accepted a s ev idence of
de le t e r i ou s reac t ion , expansions of l e s s than 0.10 must in d i ca t e po te n t ia l
a lka l i -aggrega te re ac t i v i ty . The problem i s t h a t a t p r e s e n t no t e nough
informat ion on the co rr e l a t io n between expansion of mortar bar s and f i e l d
c o n c r e t e e x i s t s
t o s e t r e a l i s t i c s a f e l i m i t s o f ex pa nsio n f o r m or ta r ba rs .
3.3 Canadian Sta nd ard s Ass oci atio n
The Canadia n st an dar d (CAN3.A23.1-M77, Appendix B3.4 113 1) s t a t e s t h a t
expans ions i n excess of 0 .04 a t any age a r e to be cons ide red de le te r io us .
t
a l so note s t ha t t he shape of the expans ion curve i s of ten of importance i n
making a judgement.
The 0.04 l i m i t for expans ion i s i n agreement w ith
f requent o bse rva t ions of c racking when th i s l e v e l of expansion i s exceeded;
the l i m i t may, however, be too re s t r i c t i v e f o r some aggre gates f o r which
expans ion may ju s t exceed t h i s va lue and then le v e l of f .
3.4 Accelera ted Danish mortar bar te s t
Th i s t e s t , de s c r ibe d by J ens en e t a l . 171,
i s
a n a c c e l e r a t e d ve r s ion of t he
mortar bar method C227 and i s use d f o r D an is h f l i n t g r a ve l s.
The mortar bars
a r e made i n th e usu al way and cured i n a fo g room a t 23OC f o r 27 days. They
a r e
then placed i n s a tu ra t ed NaCl s ol ut io n a t 50°C and expansion i s monitored
w i t h time. No
l i m i t s
have been proposed. Th is method
i s
r e po r t e d t o be
s a t i s f a c t o r y f o r t h e a gg r ega te s t e s t e d i n Denmark, bu t t he r e a r e no r e po r t s of
i t s
use elsewhere.
3.5 Chinese autoc laved mortar bar te s t
Th i s
i s
a no the r a c c e l e r a t e d mor ta r ba r t e s t . Mort ar ba r s 1
1
4 cm a r e
prepared and cured f o r one day i n a fog room. Following t h i s , they a r e steam
cured a t 100°C f o r 4 h and t hen immersed i n 10
KOH
s o l u t i o n an d au to c la v ed a t
150°C f o r 6 h. Expansions a r e recorded af t e r each phase of the cu r ing cycle .
l a r ge number o f a l ka l i - s i l i c a r e a c t i ve a gg r e ga t es w ere t e s t e d i n t h i s way by
Ming-shu, Su-fen and Shi-hua 1141, who concluded th a t t h e method i s capab le of
d i f f e r en t i a t in g be tween rea c t i ve and non-reac tive aggregate s .
More tes t ing
s hou ld be c a r r i e d ou t t o e va lua t e
i t s
e f f e c t i ve ne s s f o r a wide r va r i e t y o f
rock types. Hydrothermal t e s t s must, however, be regard ed wi th some ca ut io n
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because of the possibility that the observed expansion might be distorted by
hydrothermally induced reactions that would not
occur in concrete under normal
conditions.
3.6 Discussion
No firm limit of expansion can be specified that is applicable to all rock
types. Cracking of mortar bars is frequently observed when expansion exceeds
about 0.04 , and this value might be considered indicative of potentially
deleterious expansion. In some cases, however, this could result in
classification of some aggregates that perform satisfactorily in concrete as
deleterious. It would be desirable to have a time limit for the mortar bar
test; owing, however, to wide divergences in initiation periods and in rates
of expansion it is not possible to establish a universally applicable time
limit. It is possible that regionally applicable time-expansion limits such
as those proposed in C33 may be established for some suites of aggregates.
Accelerated tests have so far not been evaluated for a wide enough range of
aggregates to permit conclusions to be drawn as to their applicability.
4. CONCRETE PRISM TEST
The concrete prism test (CSA A23.2-14A 1151) was developed in Canada for
evaluating the expansivity of reactive dolomitic limestones that do not cause
significant expansion in mortar bars.
The test has also been used success-
fully for late-expansive siliceous aggregates and limestones containing
reactive silica. Similar tests have been used in New Zealand and
South Africa.
The criteria for evaluation of the test results are spe ified
in CSA A23.1.M77, Appendix B3.5. Linear expansions of more than about 0.03
indicate potentially deleterious expansion. Appendix 3.5 concludes that some
aggregates expand beyond the three-month period and that, where possible, the
test should be continued until expansion has virtually ceased. This is sound
advice, but it may often not be practical since with some late-expansive
aggregates it may take up to two years for expansion to taper off. The use
of the rate method of evaluating expansivity of aggregates 191 may help in
evaluating the expansivity of concrete prisms before expansion tapers off.
It is very desirable to carry out a petrographic examination in conjunction
with the concrete prism test so that the type of reactivity to be expected can
be determined; this helps in the correct evaluation of early test results if
it is not possible to wait until the expansion has tapered off.
The concrete prism method may be the most reliable test for all types of
aggregate. In it, the aggregate is tested in the same size range and with the
same cement:aggregate ratio that is used in field concrete.
For some l a t e
expansive siliceous aggregates and for carbonate reactive aggregates such as
those from Kingston, Ontario, the concrete prism test is the only satisfactory
method since these aggregates do not cause significant expansion in mortar
bars.
Expansion can be significantly accelerated by storage of the prisms at
38°C and 100
R
instead of at 23°C as specified. A few preliminary
experiments to try and accelerate expansion by
immersion of the prisms in NaCl
solution, after the method of the Danish accelerated mortar bar test, were not
very successful, but more research is needed before any firm conclusions can
be drawn.
5.
CONCRETE CUBE TEST
This test was developed in Germany 1161,
and cracking is the criterion used
to determine whether a cement-aggregate combination is reactive. There are
two versions of it. In the first, 30-cm cubes are made and expansion is
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accelera ted by s tor age i n a f og room a t 40 .
Other exposure condi t ions a r e
al s o used, f o r example, s to rag e on th e roof of the resear ch laboratory .
I n the second version of the t e s t
10-cm cubes a r e st or ed a t 65 RH wi th the
bottom 1 cm immersed i n w ater a t 20°C.
I n some samples con taining re ac t iv e
agg rega te marked cra ckin g was observed ju s t above t he wate rl ine .
I n B ri ta i n , a t th e Cement and Concrete Associat ion, a modified ver sio n of
the 10-cm cube t e s t
i s
being inves t iga ted (D.W. Hobbs, per so na l communica-
ti on ). Cubes a r e immersed i n a water bath a t 23'C and crack formation i s
observed.
A
temperature of 23'C i s reported t o be the optimum f o r so lu bi l i ty
o f s i l i c a .
In South Africa ,
30-cm cubes a r e used a t outdoor exposure s i t e s where they
may be s ubmitted t o var ious moisture and weather exposure cond it ions.
Te sts involving the obse rvat ion of cracking have a major advantage over
tests req uirin g ac ccur ate measurement of leng th change i n th a t no ela bo ra te
appara tus i s required.
This means t h a t th e concr ete cube t e s t could rea di ly
be ca rr ied out by pi t , quarry or ready-mix operators .
The disadvantage i s
t h a t un less rap id ly expanding aggrega tes a r e be ing eva lua ted
i t
would take an
unacceptably long time f or vi s i bl e cracks t o develop. From laboratory
observ at ions by t he autho r
it
is known th a t a con si de ra bl e amount of ex pans ion
can frequent ly be observed b efore cracks become v is ib le t o th e unaided eye.
6. ROCK CYLINDER METHOD
The rock c y li nde r method (ASTM C586-69 1171) was desi gne d t o eva lu a te t h e
pot en t i a l re ac t iv i ty of a lk a l i reac t iv e carbona te aggrega tes , bu t it h a s a l s o
been used wi th vary ing degrees of success t o eva lua te th e r ea c t iv i ty of
a lk al i- si l i ca re ac t i ve aggregates /5, 10, 18, 191. Paragraph 9.3 of C586
s t a t e s th at expansive behaviour of aggregate (carbonate) i n concre te
i s
qua l i t a t ive ly pred ic t ed by the res u l t s of the rock cy l inder t es t .
Grattan-Bellew 1191 found moderate co rr e la ti on between expansion of co nc re te
made wit h s i x samples of Kingston aggr eg ate and expansion of mi nia tur e rock
prisms made wit h th e same aggregates. Much poorer co r re la ti o n was observed
f o r expansion of co nc re te prisms and th at of minia ture rock prisms made with
late-expanding s i l ic e ou s aggregates. Kennerley e t a l . 1111 found t h a t some
prism s of New Zealand greywacke expanded ex ce ss iv el y i n
NaOH
but t h a t t he
same rock caused no expansion i n concrete.
I t
i s concluded t ha t t he rock cy l i nde r t e s t ,
o r va r i a t i on s o f i t can only
be
used to eva lua te the re ac t iv i ty of ce r t a i n rock types.
I t s optimum use
would probably be f o r evalua t ing th e pot en t ia l expansivi ty of indi vid ual hori -
zons i n a quarry containing a rock type f o r which co rr el at io n of expansion of
rock c yl ind er s and th a t of con cre te prisms has previou sly been demonstrated.
6.1 Acce lera ted rock prism test
An acce le r a t ed rock pr ism t e s t f o r eva lua t ion of the po te n t i a l re ac t iv i ty o f
carb onate agg reg ate s has been developed by Kazimir 1201 and adopted a s
Czechoslov akian st an da rd CSM 7 1160. Rock pr ism s 1
1 3
cm a r e prepa red
and au tocl av ed i n NaOH so lu ti on a t 215OC and 2.1 MPa f o r 6 h. Th is t e s t i s
reported t o be su cce ssf ul i n di f fe re nt ia t i ng between expansive and non-
expansive carbonate aggregates.
Some re se ar ch was conducted by t h e au thor on
t he app l i c ab i l i t y of t h i s t e s t t o l a te - expanding s i l i c e ou s aggrega te s , bu t i t
was discontinued a f t e r a felds par- l ike phase was found t o have formed i n the
prisms. Expansions occurred, but as re act i ons were taking place ( th es e do not
occur a t one atmosphere)
i t
seemed most unlikely that the observed expansions
would c o r re la te with expansions of the same prisms under atmospheric
condit ions.
More res ea rc h should probably be done a t vari ous temperatures and
p re s su re s t o see whether an acc eler ated t e s t could be developed f o r la te-
expansive s i l iceous aggregates .
3 8
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7. GEL PAT TEST
This test was developed in England as a rapid method of identifying
potentially deleterious minerals such as opal or chert in mortar samples.
It does not give any indication of the expansivity of the aggregate.
As reported by Sims 131, a smoothed, sawn surface of the mortar is prepared
and immersed face down in alkali for three days. Gel forms on the reactive
particles, which can thus be readily identified and counted to yield a measure
of the percentage of reactive component in the aggregate.
A somewhat similar test, CSN 72-1162 1211, is used in Czechoslovakia to
accelerate rim development around prisms of siliceous aggregates embedded in
mortar. It is useful for preliminary screening of potentially alkali-silica
reactive aggregates, but additional tests would be necessary to obtain a
measure of the expansivity of the aggregate in concrete.
8. PETROGRAPHIC EXAMINATION
Petrographic examination, ANSIIASTM C595 1221, has been changed from a
technique for determining the mineralogical composition of a rock to a
semi-quantitative method of determining the potential reactivity of certain
rock types by Dolar-Mantuani s development of a technique for determining the
undulatory extinction angle, UE, and relating it to the expansivity of
aggregate 1231. Following on earlier work 124-261, describing the development
of the technique for measuring strain in the quartz lattice by means of the
undulatory extinction angle, Dolar-Mantuani suggested that aggregates with
undulatory extinction angles of less than 15 deg may be characteristic*
nowreactive aggregates.
Recent unpublished results obtained by the present author show that some
South African aggregates (a quartzite from the Witwatersrand, a greywacke, and
a spotted slate from the Malmesbury Formation in the Cape Peninsula,
all of
which cause excessive expansion in concrete) have UE angles of 36, 36 and
43 deg,
respectively, indicating that there is some correlation between high
UE angle and the reactivity of the aggregates. More research into this method
should be carried out.
It has great potential as a rapid method of evaluating
the potential reactivity of quartz-bearing aggregates, particularly the late-
expansive types common in Precambrian terrains.
It would be useful to conduct
a series of interlaboratory measurements of UE angles on reference samples so
that participants could adjust their measuring techniques to ensure results
consistent with those of other operators. In a limited test carried out in
Ottawa,
a variation of
1
deg was found among measurements made by three
participants on the same quartz grains in a thin section. Such a wide
variation may have resulted because one or more of the participants measured
the extinction range, ER, rather than the undulatory extinction angle, UE, as
defined by DolarMantuani.
8.1
Use of scanning electron microscope
Use of the scanning electron microscope (SEM)
to extend the scope of the
petrographic method by permitting characterization of texture and composition
of fine argillaceous rocks may, in due course, make it possible to distinguish
between expansive and non-expansive horizons in a particular deposit.
Figure 6 shows micrographs of two rocks from the Pittsbury quarry near
Kingston, Ontario. Figure 6a shows the highly expansive dolomitic limestone
characterized by isolated dolomite rhombs in a matrix of calcite; Figure 6b
shows a dolostone, which is non-expansive. This sample is composed almost
entirely of a more coarse grained dolomite. Electron probe analysis showed
that the Ca/Mg count rate ratio was different in the two samples
(6a: Ca/Mg 3.6; 6b: Ca/Mg 3.01 indicating a higher percentage of Ca
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i n t h e r e a c t i v e d ol om it e;
t
i s the ref ore , a meta stable protodolomite 1271.
The SEM has one gr ea t advantage over ot he r techniq ues, e .g., pet rog rap hic
microscopy), that i s th e speed wi t h which obse rvat ion and an al ys is can be
done; i n about half an hour a chi p of rock ca n be coated , examined, and
analys ed by an expqrienced ope rato r .
9. CONCLUSION
There i s a d e f i n i t e t rend towards modif ic a t ion of th e s ta nda rd ASTM t e s t s
f o r u se i n c e r t a i n r e g i o n s and f o r s p e c i f i e d t y p es o f a g g r eg a te .
Th i s has
come abou t a s a r e s u l t of inadequac ies in th e s t andard t e s t me thods, e i t h e r
b ec au se t h ey f a i l t o p r e d i c t c o r r e c t l y t h e r e a c t i v i t y of a n a g gr e ga t e o r
because the t e s t tak es to o long t o complete. The t e s t methods have been
modified i n two ways:
expansion has been accce le r a t e d , a s i n the Ch inese
a ut oc la ve d m or ta r ba r t e s t ; t h e c r i t e r i a f o r t h e c he mic al t e s t , a s
recommended, have been modif ied to pre dic t th e re ac t i v i ty of lo ca l aggrega tes
more accu ra te l y , a s i n I ce land and Denmark where s p ec i f i c l i m i t s on th e
d i sso lved s i l i c a have been p roposed.
M od if ie d c r i t e r i a f o r e x i s t i n g t e s t methods may b e l i m i t e d t o s p e c i f i e d
aggrega tes in ce r t a i n r eg ions . For example , t h e p roposed Dan ish c r i t e r i a fo r
e v a l u a t in g t h e r e s u l t s o f t h e c he mi ca l t e s t of f l i n t ag g re g a te s , t h a t
Sc values between 50 and 200 mmol/L a r e ind ic at iv e of po te nt ia l re ac t i v i ty ,
would be qu i t e unsu i t ed f o r th e eva lua t i on of Thames Va l l ey f l i n t s , which a r e
non-expansive i n conc rete de sp i t e having Sc value s i n excess of
100 mmol/L.
There i s s t i l l a gr ea t need fo r bet t er , more rap id methods of d iagnosing
p o t e n t i a l l y r e a c t i v e a gg r eg a te s . F or r e aso n s a l r e a d y o u t l i n e d t h e new t e s t s
w l l p ro ba bl y b e d ev el op ed f o r t h e e v a l u a t i o n of c e r t a i n a g g r e g a te s i n
sp e c i f i c r e g i o n s .
The most promising f o r f ut ur e development a r e th e chemical
method, i n conjunct ion wi th improvements i n techniques f o r pet rograp hic
evalu at ion , and poss ib ly some type of a utocla ve ac ce le ra t i on f o r mor tar or
concre te expans ion t e s t s .
Acknowledgement
The author i s i ndeb ted t o P.J. Lefebvre f o r h i s en thus iasm fo r th e work and
the p rec i s ion wi th which he ca r r i ed ou t th e experimen t s r epor t ed i n t h i s
paper.
Th i s i s a con t r ibu t i on f rom the Div i s ion of Bu i ld ing Research,
Na tion al Research Co uncil Canada, and i s pub l ished wi th th e approva l of th e
Di rec to r of the Divi s ion.
References
/1/
ASTM C289-81, P o t e n t i a l R ea ct iv it y of Aggre gate s Chemic al Method),
Annual Book of ASTM St an da rd s, P a rt 14, C on cre te and Mi ne ral Ag greg ates .
American Soc ie t y f o r Te st i ng and Ma ter ia l s , 1916 Race St . , Phi lad elphia ,
PA 19103, U.S.A., 198 2, 198-205.
/2/
MIELENZ R.C., GREENE,
K.T
nd BENTON,
E J Chemical Test for
Re ac ti vi ty of Aggregates with Cement Alk ali s; Chemical Proces ses i n
Cement-Aggregate Reaction.
Jour na l o f th e American Concre te In s t i tu t e ,
19 3) , 1947, 193-221.
3
EMS
.
The App l i ca t ion and Re l i ab i l i t y o f S tandard Tes t ing P rocedures
fo r Po ten t i a l A lka l i Reac t iv i ty . P roc . , 5 th In t e rn a t i on a l Confe rence on
Alk ali-A ggre gate Re ac tio n, Cape Town, S252/ 13, 1981, 12 p.
/4/ DENT GLASSER, L.S. and KATAOKA,
N .
Some Obs erva tion s on th e Rapid
Chemical Te st f o r Pot en t i a l ly R eact iv e Aggregate .
Cement and Concrete
Research, 11 1981, 191-196.
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/5/ BRANDT, M.P., OBERHOLSTER, R.E. and WESTRA, W.B., A Contribution to the
Determination of the Potential Alkali Reactivity of Tygerberg Formation
Aggregates.
Proc., 5th International Conference on Alkali-Aggregate
Reaction, Cape Town, S,252/11, 1981, 6 p.
I61
MITROVIC, N. and DUCIC, V., Prilog, Zbornik, 1 MK-a, 10, 1981, 195-204.
/7/
JENSEN, A.D., CHATTERJI, S., CHRISTENSEN, P., THAULOW, N. and
GUDMUNDSSON, H., Studies of Alkali-Silica Reaction
Part 1, A Comparison
of Two Accelerated Methods. Cement and Concrete Research,
12
1982,
641-647.
I81
ASTM C227-81, Potential Alkali Reactivity of Cement-Aggregate
Combinations (Mortar Bar Method).
Annual Book of ASTM Standards,
Part 14.
American Society for Testing and Materials, 1916 Race Street,
Philadelphia, PA 19103, U.S.A., 153-158.
/9/
GRATTAN-BELLEW, P.E., A Review of Test Methods for Alkali Expansivity of
Concrete Aggregates. Proc., 5th International Conference on
Alkali-Aggregate Reaction, Cape Town, S25219, 1981, 12 p.
1101 ASTM C33-82, Appendix XI.
Methods for Evaluating Potential Reactivity of
an Aggregate (Para. 1.2, Method C289). Annual Book of ASTM Standards,
Part 14.
American Society for Testing and Materials, 1916 Race Street,
Philadelphia, PA 19103, U.S.A., 13-22.
1111 KENNERLEY, R.A., ST. JOHN, D.A. and SMITH, L.M., A Review of Thirty Years
of Investigation of the Alkali-Aggregate Reaction in New Zealand.
Proc., 5th International Conference on Alkali-Aggregate Reaction,
Cape Town, S252112, 1981, 9 p.
1121 ENGINEER MANUAL EM 1110-2-2000, Engineering and Design Standard Practice
for Concrete, (Appendix B, 3C).
Department of the Army, Office of the
Chief of Engineers, Washington, D.C. 20314, 1971.
1131 CSA CAN3-A23.1-M77, Appendix B3, Tests for Alkali-Aggregate Reactivity
(3.4, ASTM Standard C227, Potential Alkali Reactivity of Cement-Aggregate
Combinations (mortar bar method). 3.5, CSA Test Method A23.2-14A,
Alkali-Aggregate Reaction, National Standard of Canada)
CAN3 AZ3.2-7 7,
Concrete Materials and Methods of Concrete Construction, Methods of Test
for Concrete.
Canadian Standards Association, Rexdale Boulevard,
Rexdale, Ontario, Canada, 1977, 122-123.
1141 MING-SHU, Tang, SU-FEN, Han, and SHI-HUA, Zhen, A Rapid Method for
Identification of Alkali Reactivity of Aggregate. Cement and Concrete
Research,
2
983, 417-422.
1151 CSA A23.2-14A, Alkali-Aggregate Reaction (Concrete Prism Test).
National
Standards of Canada, CAN3 A23.1-M77, CAN3 A23.2-M77, Concrete Materials
and Methods of Concrete Construction. Methods of Test for Concrete.
Canadian Standards Association, Rexdale Boulevard, Rexdale, Ontario,
Canada, 1977, p. 183-185.
1161 BONZEL, Von J. and DAHMS,
J.
Alkalireaktion im Beton, Herstellung
Verwendung 23, 11, S4951500 und H.12, S5971554, 1973.
1171 ASTM C586-69, Standard Test Method for Potential Alkali Reactivity of
Carbonate Rocks for Concrete Aggregates (Rock Cylinder Method). Annual
Book of ASTM Standards, Part 14, Concrete and Mineral Aggregates.
American Society for Testing and Materials,
1916 Race Street,
Philadelphia, PA 19103, U.S.A., 1982, 357-360.
1181 DUNCAN, M.A.G., SWENSON, E.G., GILLOTT, J.E. and FORAN, M.R., Alkali-
Aggregate Reaction in Nova Scotia, Part I, Summary of a 5-Year Study.
Cement and Concrete Research,
2 1973, 55-70.
I191 GRATTAN-BELLEW, P.E., Evaluation of Miniature Rock Prism Test for
Determining the Potential Alkali-Expansivity of Aggregates. Cement and
Concrete Research,11 981, 699-711.
1201 KAZIMIR,
J.,
MoZnosE Skratenia Sk613ky Rozpinania Dolomitovy ch ~ornl n
Alkaliami, Staveb. Cas. 25, c s. Veda Bratislava, 1977, 413-432.
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1211 CSN 72 1162, Stanovenie Odolnostri Prirodnc ho ~tavebnkho 9me6a Proti
~ilicifikich.
MDT 691.2.620.1 679.682.1, Ceskoslovenskti Stgtna Norma
Schvhle~: 4.10. 1981.
1221 ANSIIASTM 295-79, Standard Reconmended Practice for Petrographic
Examination of Aggregates for Concrete. Annual Book of ASTM Standards,
Part 14, Concrete and Mineral Aggregates. American Society for Testing
and Materials, 1916 Race Street, Philadelphia, PA 19103, U.S.A., 1982
218-229.
1231 DOLAR-MANTUANI, L.M.M., Undulatory Extinction in Quartz Used for
Identifying Potentially Alkali-Reactive Rocks. Proc., 5th International
Conference on Alkali-Aggregate Reaction, Cape Town, S252136, 1981, 6 p.
1241 DEHILLS, N.S. and CORVALAN, J., Undulatory Extinction in Quartz Grains of
Some Chilean Granitic Rocks of Different Ages.
Geological Society of
America, Bulletin 75, 1964, 363-366.
1251 DOLAR-MANTUANI, L.M.M.. Petrographic Aspects on Siliceous Alkali-Reactive
Aggregates. P;OC., ~ ~ ~ ~ o s i u m o n ~ ~ l k a l i ~ ~ ~ ~ r e ~ a t eeaction, Reykjavik,
1975. p 87-100.
1261 M A ~ R ;
.,
Presentation at Symposium on Alkali-Aggregate Reactivity.
Annual Meeting of Transportation Research Board, Washington, D.C., 1976.
/27/ SWENSON, E .G. and GILLOTT, J. E Alkali-Carbonate Rock React ion. Highway
Research Record, No. 45, 1964, 21-40.
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Fi gur e
1
E f f e c t of g r a i n s i z e o f q u a r t z o th a o u a t af d i s s o l v e d s i l i c a
det erm ine d by t h e chem ica l met hod , ASTM C289
1 0 0 0
5 0 0
300
-
aoa
0
4 8 12 16 20
24
O P A L
I N
Q U A R TZ S A N D
l l . l L , l ,
b
1 -
\
\
-
Figure 2
P lo t showing va ri a t i o n i n Sc and Rc/Sc determined by t h e chemical
t e s t ,
STM
C289, and leng th change of mor tar ba rs of qu ar tz sand
con tain ing var io us amounts of op al
6 0
\
-
3 0
1 5 -
-
-
5 0 m " 1 ' t " "0 0 4 0 0 6 0 0 8 0 0 1 0 0 0
MEAN G R l N
S 1 Z E ,LL m
2 5 0 1 1 1 1 1 1 1 1 1
2 0 0
-
1 5 0
-
INNOCUOUS
1 0 0
-
t a
DELETERIOUS
D I S S O L V E D S I L I C A
S c
m m o l l l
Figure
Resul t s of chemica l t e s t , STM C289, f o r s o w re ac t iv e and non-
re ac t i ve South Afr ican aggregates . Non-react ive: No no r i te ) and
WS quar tz sand)
3 3
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T h i s p ap er w h i le b ein g d i s t r i b u t e d i n
re p r i n t fo rm by t h e D i v i s i on of B u i l d i ng
Resea rch remai ns t h e copyr i gh t of t h e
o r i g i n a l p u b l i s h e r . t should no t be
r ep ro du ce d i n whole o r i n p a r t w i th o u t t h e
pe rmi ss ion of t h e pub l i she r .
l i s t of a l l p u b l i c a t i o n s a v a i l a b l e from
t h e D i v i s i on may be ob t a i ned by wr i t i ng t o
t h e P u b l i c a t i o n s S e c t i o n 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 N a t i o n a l R e s e a r c h
C o u n c i l o f C a na d a O t ta w a O n t a r i o
KI 0R6.