Corrosion of concrete by bog waters: a literature review

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Corrosion of concrete by bog waters: a literature review MacFarlane, I. C.

N A T I O N A L RESEARCH C O U N C I L O F CANADA D I V I S I O N OF B U I L D I N G RESEARCH

CORROSION O F CONCRETE BY BOG WATERS

-

A L I T E R A T U R E R E V I E W

R e p o r t No.

4 8

of the

Divieion of Building R e s e a r c h

O t t a w a

The work of the D i v i s i o n of B u i l d i n g Research i n n o r t h e r n Canada b r i n g s i t f r e q u e n t l y i n t o touch w i t h t h e many p r o b l e n ~ s c r e a t e d by t h e e x i s t e n c e of muskeg over l a r g e a r e a s of t h e North, M r . MacFarlane, t h e a u t h o r of t h i s r e p o r t , i s a member of t h e S o i l Mechanics S e c t i o n of the D i v i s i o n and i s d e v o t i n g a l l h i s time t o r e s e a r c h s t u d i e s on muskeg, working i n c l o s e a s s o c i a t i o n w i t h D r . N O W , Radforth of McMaster U n i v e r s i t y ,

Although t h e D i v i s i o n a l s t u d i e s of muskeg a r e g e n e r a l l y r e l a t e d t o i t s mechanical, p h y s i c a l , and b o t a n i c a l p r o p e r t i e s ,

some r e c e n t b u i l d i n g a c t i v i t i e s i n t h e North gave r i s e t o q u e s t i o n s r e g a r d i n g t h e e f f e c t of t h e w a t e r always encountered i n muskeg

upon c o n c r e t e w i t h which i t might be i n c o n t a c t ,

Following t h e u s u a l procedure i n r e s e a r c h , a s t u d y was

made of r e l e v a n t l i t e r a t u r e and s i n c e no r e c o r d of a s i m i l a r survey c o u l d be found it was thought a d v i s a b l e t o p u t t h e r e s u l t s of Rir.

MacFarlanefs r e s e a r c h i n t h i s permanent form. I t i s hoped t h a t i t

w i l l be of u s e t o t h o s e who may be concerned with t h e somewhat unusual problem.

The w r i t e r h a s p e r s o n a l i n t e r e s t i n t h i s r e p o r t i n t h a t t h e p a p e r s 1 i . s t e d a s r e f e r e n c e s

6

and

7

were prepared i n t h e

Westminster c o n s u l t i n g o f f i c e i n which t h e w r i t e r gained h i s e a r l y e x p e r i e n c e . He was p r i v i l e g e d t o do some of t h e s t u d i e s which a r e r e p o r t e d i n r e f e r o n c e No,

7.

O t t;awa

November

1958

Robert F. Legget D i r e c t o r

CORROSPON OF CONCREm BY HOG

WATERS

-

A

LITERATURE

REVIEW

I .C l MacFarlane

It h a s l o n g been r e a l i z e d t h a t c o r r o s i o n of c o n c r o t e i s

of c o n s i d e r a b l e economic importance l I n v a r i o u s countries

e x t e n s i v e s t u d i e s of chemical a t t a c k on t h i s m a t e r i a l hnvo hsen

c a r r l o d out. The g r e a t bulk of t h i s r e s e a r c h h a s concerbned

i t s e l f w i t h t h e problem of s u l p h a t e a t t a c k on c o n c r o t e , d o u b t l e s s because i n p r a c t i c e t h e most common cause of chemical ds texbiorat Lon i s by s u l p h a t e a . Very l i t t l e d o t a i l e d i n f o r m a t Ion I s avt3llab3.e

on t h e o o r r o s i o n of p o r t l a n d cement p r o d u o t s by a c i d s

--

and. i n p a r t i c u l a r by a c i d i c bog w a t e r s

--

p o s s l b l y because i t i s

a u t o m a t i c a l l y a ssurned t h a t most a c i d s do a t t a c k por1;land coment l

However it should be borne i n mind t h a t the q u a l i t y of the c o n c r e t e and t h e n a t u r e of i t s i n g r e d i e n t s a f f e c t i t 8 vulnera-

b i l i t y t o ncid c o r r o s i o n . Much of t h e work which has b s o n done I n t h f s f i e l d t o d a t e h a s been concerned w i t h i n v e s t f g a t i n g t h e e f f e c t of t h e a t t a c k of a c i d i c p e a t y w a t e r s on c o n c r e t e dra5n t i l e . These i n v e s t i g a t i o n s have been c a r r i e d o u t c h i e f l y i n t h e United S t a t e s . Other t h a n t h i s , t h e r e a r e a few refor4encos on t h e e f f e c t of such a g g r e s s i v e w a t e r s on l a r g e c o n c r e t e strut t u r e a such a s dams. Some work h a s been done a l s o on c o n c r e t e specimens i n t h e l a b o r a t o r y .

R6sum6 of Published L i t e r a t u r e

One of the e a r l i e s t s t u d i e s of t h e e f f e c t of a c i d i c w a t e r s on c o n c r e t e was t h a t of Dykerhoff

(31,

who d i s c u s s e d t e s t s on

c o n c r e t e m d e w i t h f o u r k f n d s o f sand and which showed t h a t a l l c o n c r e t e i s more o r l o s s a t t a c k e d by marsh water. The g r e a t e r t h e amount of s i l i c a i n t h e cement t h e b e t t e r i t r e s i s t e d , He found t h a t sea sands and marah sends gave the p o o r e a t r e a u l t s . The p e r m e a b i l i t y of t h e m o r t a r s was t e s t e d by i m o r s i o n

i n

5

por c e n t

s u l p h u r i c a o i d , and by t i t r a t i n g t h e e x c e a s a c i d w i t h soda he concluded t h a t o z o c e r i t o and a s p h a l t were t h e b e s t m a t e r i a l s f o r we t e r p r o o f ing.

The paper by Halcrow, Brook and P r e s t o n

( 7 )

and t h e sub- sequent d i s c u s s i o n (12) were concerned w i t h the e f f e c t of p e a t y w a t e r s on a c o n c r e t e dam. A l a t e r paper by Halcrow

( 6 )

was a

swmning up of t h e e x p e r i e n c e gained and gave c e r t a i n d e s i g n c r i t e r i a based on t h i s e x p e r i e n c e . The o b j e o t of t h e o r i g i n a l paper w a s t o d e s c r i b e a p a r t i c u l a r i n s t a n c e of t h e d e t e r i o r a t i o n

of c o n c r e t e s u r f a c e s due t o c o n t a c t w i t h moorland w a t e r s , i t s e f f e c t on t h e d e s i g n and c o n s t r u c t i o n of h y d r o - e l e c t r i c i n s t a l - l a t i o n s and a l a o t o g i v e some p a r t i c u l a r s of a s e r i e s of t e s t s c a r r i e d out t o a s c e r t a i n t h e b e s t m a t e r i a l s f o r r e s i s t i n g s u c h a c t i o n . The r e s e a r c h was done a t t h e Kinlochleven works of t h e B r i t i s h Aluminium Co. Ltd.

I t was found t h a t i n t h e course of time a l l c o n c r e t e s u r f a c e s exposed t o water, whether s t i l l o r running, were

a f f e c t e d . The smooth s u r f a c e of t h e c o n c r e t e became rough. The cement d i s a p p e a r e d from t h e f a c e s of c o n c r e t e a t r u c t u r e a exposed t o a g g r e s s i v e w a t e r , l e a v i n ~ t h e g r a i n s of sand and arnall aggre- g a t e s exposed. The sand g r a i n s c o u l d be removed by rubbing w i t h t h e hand. The d e p t h t o which t h e a c t i o n t o o k p l a c e was s m a l l and probably d i d n o t exceed one-sighth of a n i n c h , t h e r e f o r e t h e

s t a b i l i t y of t h e s t r u c t u r e was n o t a f f e c t e d . I n t h e c a s e of

c o n d u i t s , however, t h e d e t e r i o r a t i o n of t h e s u r f a c e i n c r e a s e d t h e c o e f f i c i e n t of f r i c t i o n and t h e r e b y reduced t h e carrying, c a p a c i t i e s w i t h a consequent d e c r e a s e i n t h e

maximum

p o s s i b l e o u t p u t from t h e power a t a t ion.

Analyses of t h e w a t e r and t e s t s made i n t h e l a b o r a t o r i e a showed t h a t t h e a c i d s i n t h e p e a t y moorland water disso3.ved t h e lime and calcium aluminate i n t h e cement and somewhat r a p i d l y removed the f a c e of t h e c o n c r e t e , t h e a c t i o n beooming much slower a s t h e a r e a of cement exposed was l e s a e n e d by t h e p r e s e n c e o f

sand g r a i n s .

I n

o r d e r t o determine t h e b e s t cement o r o t h e r m a t e r i a l t o be used t o r e s u r f a c e t h e c o n d u i t when t h e n e c e s s i t y

should a r i s e and a l s o w i t h a view t o d e a l i n g w i t h new works a t Lochaber, experiments were commenced i n 1921 on t h e r e s i s t a n c e of v a r i o u s cements and p r o t e c t i v e c o a t i n g s t o t h i s c o r r o s i v e a c t i o n . Some 113 p o s s i b l e m a t e r i a l s were t e s t e d . They c o n s i s t e d of

v a r y i n g m i x t u r e s of p o r t l a n d , s l a g , and aluminous cement c o n c r e t e s , t a r s , bitumens, b r i c k s , r e n d e r i n g s , chemical s u r f a c e t r e a t m e n t , p r o p r i e t a r y and o t h e r s .

A s m a l l c o n d u i t ,

4

f t wide by

4

f t deep, c o n e t r u c t e d f o r c a r r y i n g w a t e r c o l l e o t e d from a s m a l l watershed a d j o i n i n g t h e

main

c o n d u i t t o t h i s c o n d u i t , was a e l e c t e d f o r t h e t e s t s . The f i r s t t e a t s c o n s i s t e d of exposing i n t e r n a l l i n i n g s t o t h e w a t e r and s u b s e q u e n t l y a s t h e number of m a t e r i a l s t o be t e s t e d i n c r e a s e d , l o o s e s l a b s of o o n c r e t e were p r e p a r e d and s e t i n t h e c o n d u i t f o r c o n t a c t w i t h the water. These l i n i n g s and s l a b s were formed of v a r i o u s c o n c r e t e s t o be t e s t e d o r c o n s i s t e d of a s t a n d a r d mixture of 4:2 :1 p o r t l a n d cement o o n c r e t e on which c o a t i n g s were t e s t e d . The i n t e r n a l l i n i n g s were

4

1/2 in. t h i c k , d i v i d e d i n t o bays

6

f t long, e a c h s i d e having a d l f f e r e n t m a t e r i a l . The s l a b s were 2 f t

d e t e r i o r a t i o n a t t h e end of one y e a r and only a few were u n a f f e c t e d a f t e r a p e r i o d of y e a r s ; of t h e s e , aluminous cements wero out-

s t a n d i n g l y good and c e r t a i n p a i n t e d and c h e m i c a l l y t r e a t e d s l a b s were promising.

Viewing t h e t e s t s a s a whole, t h e a u t h o r s s t a t e d t h a t , w i t h few e x c e p t i o n s , a l l t h e m a t e r i a l s t r i e d were a b l e t o with-

s t a n d t h e v i g o r o u s c o n d i t i o n s b e t t e r t h a n p o r t l a n d cement c o n c r e t e . I n t h e s h o r t p e r i o d of 270 days o r d i n a r y c o n c r e t e appeared t o

have reached i t s worst p o s s i b l e s t a t e and a t 1800 days appeared t o be no worse t h a n it was

4

y e a r s b e f o r e . High-grade aluminous cement c o n c r e t e showed no s i g n of d e t e r i o r a t i o n even a f t e r

6

1/2 y e a r s exposure t o t h e a c i d i c moorland water. I t had e v e r y

appearance of permanency, A n e a t r e n d e r i n g of t h i s type of cement i s a l a o v e r y r e s i s t a n t but i s not t o be r e c o m ~ e n d e d on account of the c r a c k s which develop when used n e a t

--

a l t h o u g h t h e y were conceivably due t o i n s u f f i c i e n t c u r i n g , Mortars of sand and aluminouv cement were s i m i l a r l y u n a f f e c t e d by water.

O f t h e c a l c a r e o u s cements, o n l y one k i n d m e r i t e d f a v o u r a b l e mention, namely t h e f inely-ground o r r a p i d - h a r d e n i n g t y p e

.

The one t e s t e d was undoubtedly s u p e r i o r t o common p o r t l a n d cement Used i n t h e form of a m o r t a r , a r e a s o n a b l y d u r a b l e s u r f a c e was obtained. It wa a found g e n e r a l l y t h a t cements s u p p l i e d n e a t u s u a l l y were very d u r a b l e , whether of a c a l c a r e o u s o r aluminous n a t u r e , b u t they a l l s u f f e r e d from a p e c u l i a r s u r f a o e decay i n t h e moorland w a t e r i n which t h e y were t e s t e d . T h i s decay took t h e form of a s o f t e n i n g of t h e s u r f a c e t o a d e p t h of a b o u t 0.02 i n o , t h e t o p l a y e r of d u s t y '?dead1' cement being removable i n p l a c e s by

rubbing

.

Mention w a s made of a s u r f a c e composed of' e q u a l p a r t s of aluminous cement and p o r t l a n d cement, The chemical r e a c t i o n s d u r i n g t h e s e t of t h e s e two cements r e s u l t e d i n t h e p r o d u c t i o n of f r e e alumina and f r e e lime, One t e s t performed was of a s u r f a c e of e q u a l p a r t s of n e a t aluminous cements and p o r t l a n d cements, and a p a r t from a few s u r f a a e c r a c k s i t was s t i l l hard and sound a f t e r n e a r l y

3

y e a r s , A r e d u c t i o n i n t h e p r o p o r t i o n of a l ~ u n i n o u s cement and c a r e i n the c u r i n g was suggested a s a means of e l i m i - n a t i n g t h o s u r f a c e c r a c k s d e f e c t . Of t h e p a i n t and o i l s u r f a c e t r e a t m e n t s t h e r e were s e v e r a l which appeared t o be a b l e t o s t a n d up f o r a l o n g period. Those of bitumen and t a r b a s i s were found

t o be t h e s u p e r i o r of the two c l a s s e s . Next t o t h e bituminous m a t e r i a l s t h e o i l emulsion o f f e r e d a m a t e r i a l of f a i r l y l o n g l i f e and ono which i s a p p l i c a b l e t o wet o r d r y concrete. The o i l used most s u c c e s s f u l l y i n t h e s e emulsions was chinawood o i l .

I n t h e s u b s e q u e n t d i s c u s s i o n t o t h e above p a p e r i , . ~ 2 ) , i t

was s u g g e s t e d t h a t it might be more economical t o t r e a t the w a t e r

wibh s i l i c a t e o f soda o r h y d r a t e o f l i m e , t h e r e b y n e u t r a l i z i n g t h e a c i d i o e f f e c t . However, it was p o i n t e d o u t t h a t i n l a r g e h y d r o - e l e c t r i c schemes which i n v o l v e g r e a t q u a n t i t i e s of w a t s r , s u c h a s o l u t i o n t o the problem i s n o t a l t o g e t h e r f e a s i b l e . The p a p e r by Tremper p r e s e n t s t h e r e s u l t s of a n e x t e n s i v e i n v e s t i g a t i o n i n t o t h e c o r r o s i v e e f f e c t of a c i d w a t e r s on c o n c r e t e , i n t h i s c a s e l a b o r a t o r y specimens

(13)

* I n h i s summary, t h e a u t h o r p o i n t s o u t t h a t t h e i n v e s t i g a t i o n shows t h a t t h e s e t t l n g and h a r d e n i n g of p o r t l a n d cement d o e s n o t r e s u l t i n compounds of lime t h a t a r e a b s o l u t e l y i n s o l u b l e i n w a t e r . The s o l u b i l i t y of lime i n c r e a s e s w i t h t h e a c i d i t y of t h e w a t e r . T h i s f a c t r a i s e d t h e q u e s t i o n a s t o whether c o n c r e t e exposed t o l.vater i s a b l e t o p e r m a n e n t l y r e s i s t t h e l o s s o f lime t h r o u g h l e a c h i n g . T h i s p a p e r d e s c r i b e s t e s t s of i n t a c t c o n c r e t e s p e c i n e n s exposed i n a f l o w o f a r t i f i c i a l l y a c i d i f i e d w a t e r , t h e pH v a l u e of which was comparable t o t h a t of n a t u r a l w a t e r s , A few specimens were exposod i n a

s m a l l c r e e k which was n a t u r a l l y s l i g h t l y a c l d .

The w a t e r was made t o flovi p a s t t h e s u r f a c e of t h e c o n c r e t e b u t was n o t f o r c e d t h r o u g h

it.

The a u t h o r c o n c l u d e d , howovcr,

t h a t t h e r e s u l t s would p r o b a b l y a p p l y i n a g e n e r a l way t o c o n c r e t e t h r o u g h which w a t e r i s p e r c o l a t i n g . He p r e s e n t s t h e r e s u l t s o f t e s t s of a b o u t 3000 specimens. Theso r a n g e d from 1 1/2- by 1 1 / 2 1 by ,$-in. p r i s m s t o

8-

by &in. c y l i n d e r s . Data were o b t a i n e d on

t h e l o s s of lime and t h e r e l a t i v e l o s s i n s t r e n g t h r e s u l t i n g f r o m a o i d exposure.

F a c t o r s which were s t u d i e d i n c l u d e d : (1) v a r i a t i o n s i n s e v e r i t y o f exposure; ( 2 ) v a r i a b l e s a r i s i n g from m a t e r i a l s u s e d a n d c o n d i t i o n s of m a n u f a c t u r e of t h e c o n c r e t e ; and

( 3 )

t h e t h e o r y

of c o r r o s i o n . A n e f f o r t was made t o e v a l u a t e the e f f e c t of a number of s u b d i v i s i o n s of e a c h of t h e above headings. The d a t a

o b t a i n e d were u s e d t o e s t i m a t e t h e p r o b a b l e l i f e of c o n c r e t e s t r u c t u r e s under v a r i o u s c o n d i t i o n s of' a c i d e x p o s u r e

.

The p r i n c i p a l c o n c l u s i o n s of i n t e r e s t a r e l i s t e d below.

( i ) For t h e r a n g e of a c i d i t y e x p r e s s e d by p H v a l u e s between

6.0

and

7.0

t h e d e g r e e of a t t a c k i s i n v e r s e l y p r o p o r - t i o n a l t o t h e pH number; i f t h e pH of the w a t e r i s above 7.0

t h e a t t a c k i n g e n e r a l i s t o o m i l d t o be of a n y p r a c t i c a l consequence.

( i i ) The volume of w a t e r and i t s v e l o c i t y must be very low b e f o r e a d e c r e a s e i n t h e r a t e of a t t a c k i s observed.

( i i i ) Waters of h i g h v e l o c i t y , p a r t i c u l . e r l y i f t h e y c a r r y suspended m a t t e r , may a c c e l e r a t e t h e r a t e of a t t a c k .

( i v ) Exposure t o a n a t u r a l l y a c i d creek gave r o u u l t s comparable t o t h o s e o b t a i n e d w i t h a r t i f i c i a l l y a c i d i f i e d water i n t h e l a b o r a t o r y .

( v ) Of f o u r brands of p m t l e n d cement s t u d i e d , none was d i s t i n c t l y s u p e r i o r i n r e s i s t a n c e ; c o n c r e t e s made of some

s p e c i a l cements were a t t a c k e d t o a l e s s e r degree t h a n t h o s e made of p o r t l a n d cement.

( v i ) The c h a r a c t e r of t h e aggregate probably h a s l i t t l e e f f e c t on r e s i s t a n c e ; i f t h e r e i s a d i f f e r e n c e between a g g r e g a t e s ,

i t cannot be connected w i t h r e s u l t s of u s u a l i n s p e c t i o n o r t e s t s . ( v i i ) Allowing t h e c o n c r e t e t o become d r y b e f o r e exposure, o r c u r i n g f o r

48

hours i n water vapour a t any temperature between

70 and 212OF, have no e f f e c t on r e s i s t a n c e .

( v i i i ) Although admixture a were found t h a t i n c r e a s e d t h e r e s i s t a n c e of c o n c r e t e somewhat, none a f f o r d e d complete p r o t e c t i o n .

( i x ) Surface c o a t i n g s i n g e n e r a l reduced t h e r a t e of a t t a c k f o r two y e a r s ; t h e performance of such p r o t e c t i o n depends upon t h e d u r a b i l i t y of t h e c o a t i n g o r t h e frequency of i t s renewal.

( x ) Concrete of h i g h q u a l i t y i s markedly more r e s i s t a n t t h a n poor c o n c r e t e .

( x i ) The s t r e n g t h of c o n c r e t e a t any s t a g e of a t t a c k i s dependent on t h e r a t i o of t h e mixing w a t e r t o t h e amount of l i m e remaining i n t h e c o n c r e t e ; t h e r e l a t i o n s h i p may be

expressed by a curve s i m i l a r t o t h e water-cement r a t i o curve.

( x i i )

Loss of lime c a u s e s a d e c r e a s e i n s t r e n g t h of c o n c r e t e ; when a b o u t 50 p e r c e n t of t h e o r f g i n a l lime has been removed from average c o n c r e t e , complete l o s s of s t r e n g t h and coherence r e s u l t s .

( x i i i ) The l o g a r i t h m of t h e q u a n t i t y of l i n e removed v a r i e s d i r e c t l y w i t h t h e l o g a r i t h m of t h e p e r i o d of exposure.

( x i v ) Apart from a s e v e r e a t t a c k of about

1/16

in. a t t h e surface, l o s s i n lime w i t h accompanying l o s s i n s t r e n g t h

i s

u n i f o m throughout t h e body of t h e c o n c r e t e f o r a d e p t h of a t l e a a t f i f t e e n i n c h e s from t h e surfaoe.

( x v ) The r a t e of a t t a c k i s g r e a t l y a f f e c t e d by t h e r a t i o between exposed surfaae and t h e volume of' t h e c o n c r e t e .

( x v i ) Due t o a h i g h s u r f a c e - v o l i m e r a t i o , s m a l l members s u c h a s

3-

o r

&-in.

d r a i n t i l e may have a v e r y s h o r t l i f e i n a c i d s o i l s .

( x v i i ) S t a n d a r d c u l v e r t p i p e , 12 i n . o r more i n d i a m e t e r , o r o t h e r s t r u c t u r e s h a v i n g a n e q u a l o r s m a l l e r s u r f a c e - v o l u n e r a t i o , if made of r e a s o n a b l y good c o n c r o t a , may be e x p e c t e d t o have a l i f e r u n n i n g i n t o t h e c e n t u r i e s , under a l l p r o b a b l e c o n d i t i o n s of n a t u r a l a c i d i t y i n w a t e r .

The r e p o r t s by M i l l e r and Manson

( 8 )

( 9 )

a r e b a s e d on e x a m i n a t i o n s and t e s t s of some 1100 commercial and e x p e r i m e n t a l d r a i n t i l e a n d 10,000 2- by 4-in. e x p e r i m e n t a l c y l i n d e r s . I n s t a l - l a t i o n s of e x p e r i m e n t a l specimen8 were made i n t l ~ r e e p e n t s i n Minnesota, t h r e e p e a t s i n Wisconsin and a n a c i d m i n e r a l s o i l i n North C a r o l i n a . F o r p u r p o s e s o f comparison, specimens were a l s o i n s t a l l e d i n one m i n o r a l s o i l i n Minnesota and ono i n Wisconsin. F i e l d and l a b o r a t o r y s t u d i e s e x t e n d e d o v e r a 24-year p e r i o d , from 1923 t o 1947. The s i g n i f i c a n t resu1.t s of t h i s i n v e s t i g a t i o n a r e a 8 f o l l o w s .

( i ) The d e g r e e of a c t i o n on t h e commercial c o n c r e t e t i l e t a k e n from 1 2 Wisconsin d r a i n a g e systems and i n s t a l l e d i n p e a t 20 t o

26

y e a r s g r e a t l y v a r i e d between systems, r a n g i n g a l l

t h e way f r o m n e g l i g i b l e e t c h i n g t o complete d i s i n t e g r a t i o n of t h e t i l e . I t was n o t c l e a r from t h e d a t a j u s t what i n f l u e n c e e i t h e r t i l e q u a l i t y o r s o i l a c i d i t y h a d on d u r a b i l i t y , b u t i n t h e two systems where complete d i s i n t e g r a t i o n had o c c u r r e d t h e t i l e was v e r y low i n q u a l i t y a s determinod by s t r e n g t h and a b s o r p t i o n

t e s t s w h i l e t h e s o i l a c i d i t i e s , a s measured by pH v a l i i e s of

s 0 9

and

6.4,

were h i g h e s t and second h i g h e s t of t h e t w e l v e l o c a t i o n s .

( i i ) Behaviour of the e x p e r i m e n t a l t i l e waE e s s e n t i ~ lly t h e same a s t h a t o f the commercial t i l e i n t h a t t h e s t r e n g t h t r e n d s were downward f o r t h e t i l e i n o t a l l e d i n p e s t w i t h pH v a l u e s o f

5.9

a n d 8.0, For t h e commercial t i l e s from seven systemn i n p e a t s w i t h pH v a l u e s from

5.9

t o 7 0 5 , t h o l o s s i n brealring s t r e n g t h s a v e r a g e d 260 l b d u r i n g t h e

1 7

y e a r s between t e s kc*, w h i l e f o r t h e e i g h t l o t s o f o x p e r f m e n t a l t i l e i n t h e two p e a t s vii1.h p H v a l u e s of

5.9

and

8.0

t h e a v e r a g e l o s s was 550 l b i n 14 y e a r s . Con- sS-dered t o g e t h e r , t h e l o s s i n s u p p o r t i n g s t r e n g t 1 : s of a l l t h e s e t i l e a f t e r a n a v e r a g e p e r i o d o f

15

3./2 y e a r s I n p u a t w a s s l i g h t l y more t h a n 400 l b p e r l i n e a l f o o t . (ii i ) The s t r e n g t h t r s n d s o f t h e e x p e r i m e n t a l c y l . i n d e r s of p l a i n c o n u r e t o and m o r t a r s were a t , r i . k i n

_P

ly s i m i l a r t o t h o s e o f t h e d r a i n t i l e , w i t h t h e r e s u l t t h a t tho 1-1 y e a r s bet,weon e x p o s u r e s

s t r e n g t h s around 5000 p s i l o s t an a v e r a g e of about 1170 p s i I n

t h e p e a t s w i t h pH v a l u e s of 4.1, 5.1 and

5*lL.

l b ~ ~ s t s of t h e low

s t r e n g t h m o r t a r c y l i n d e r s of 1000 p s i exposed i n p e a t a wit;k~

p H v a l u e s of

4-.1

and

5.1

showed a l o s s of 750 p s i f o l l o w i n g

exposures f o r t h e 3.2 y e a r s between

5

and 17 y e a r s , w i t h the

d a t a i n d i c a t i n g a l o s s of

860

p s i had t h e exposures c o ~ l t ~ j n u s d

a n o t h e r two y e a r s , Expressed a s p e r c e n t a g e s , the st~*rtngI;h l o a s of khe c o n c r e t e c y l i n d e r s was

18

p e r c e n t of the s t r s n g t l l a f ;

5

y e a r s , whereas t h e m o r t a r c y l i n d e r s l o s t

45

p e r c e n t of tho

s t r e n g t h a t

5

y e a r s ,

( i v ) Peat a c i d i t y a s measu.red by pH deter'minat :i.on.s I s a f a i r indicator of' the degree of c o r r o s i . v e a c t i o n .to 'bs

expected on c o n c r e t e .

( v )

A c i d i t i e s of the t h r e e m i n e r a l soi1.s a s mes:31rred.

by pH d e t e x a i n e t i o n s d i d n o t f u r n i s h a s r e l i a b l e an irldex o f

c o r r o s i v e a c t i o n on c o n c r e t e s a s f o r t h e p e a t s . JJo e x a c t o x p l a n a t i o n was o f f e ~ e d f o r t h i s a p p a r e n t d i s c r e p s n c y be t;vlieaxl

pE v a l u e s of p e a t s a n d those of m i n e r a l s o i l s .

( v i ) None of t h e

si.x

a d m i x t u r e s of d i f f e r e n t t;ypea

incraeased t h e r e s i s t a n c e of t h e c y l i n d e r s i n which t h e y were used. ( v i i ) V a r i a t i o n s i n t h e c h e m i s t r y of 20 d i f f e r e n t

cements had 1 i t t l . e e f f e c t on r e s i s t a n c e t o t h e _{s o i l a c f d s , w i t h}

t h e e x c e p t i o n of t h e h i g h alumina cements which were somewhat more r e s i s t a n t t h a n were any of t h e p o r t l a n d cements,

( v i i i ) Specimens c u r e d i n steam a t t e m p e r a t u r e s of'

15S0,

212O o r 28s0F d i d n o t r e s i s t p e a t a c t i o n a p r e c i a b l y b e t t e r t h a n d i d water-cured ones, b u t t h o s e cured a t

3

E

S°F h e l d up i n s t r w n g t h throughout t h e 1 7 y e a r s d u r i n g which they wore under o b s e r v a t i o n .

(1x1

The o n l y s u r f a c e t r e a t m e n t s used w e ~ s l i n s e e d o i l and a cut-back bituminous product. Both of t h e s e somewhat in.creased t h e r e s i s t a n c e o f t h e c o n c r e t e c y l i n d e r s t o which a p p l i e d .

( x )

R i c h mixes of h i g h s t r e n g t h and low p e r m e a b i l i t y gave t h e g r e a t e s t r e s i s t a n c e t o t h e a c t i o n of s o i l a c i d s *

The r e p o r t by F r a s e r

( 5 )

d i s c u s s e s a s e a r c h f o r cheaper a l t e r n a t i v e s t o t h e u s u a l p h y a i o a l ( p a i n t i n g of s u r f a c e s e t c . ) and chemical ( u s e of h i g h alumina and waterproof oements! methods of p r o t e c t i n g c o n c r e t e from p e a t y w a t e r s , s i n c e b o t h measures a r e expensive. Simple t e s t s were begun i n

1953

a t t h e North of

S o o t l a n d Hydro-Electric Boardla Gaur P r o j e c t and t h e problem approached from b o t h t h e p h y s i c a l and chemioal s t a n d p o i n t s . A t

t h i s p a r t i c u l a r l o c a t z o n t h e p H of t h e run-off i s sometimes a s low a s

4.0.

Three types of concrete were t e s t e d :

(1) Type N o r d i n a r y portland cement concrete ( 2 ) Type A

-

ordinary portland cement ooncrete

with an agent t o e n t r a i n 3.0 t o

3.5

p e r cent

a i r f o r improved physical r e s i s t a n o e

( 3 )

Type X

-

ordinary portland cement concrete wi6h a minute q u a n t i t y of water s o f t e n e r f o r Improved chemical r e s i stanae.

Additives "At'

and

")C1' were combined with the mixing water.

T h i r t y cubes of

6

in. s i d e s were made of each type, cured i n r a i n w a t e r f o r 28 days and a i r - d r i e d f o r

7

days. F i f t e e n cu.bes of each type were immersed i n r a i n w a t e r ,

15

i n the Gaur f ishpaes.

A t i n t e r v a l 0 of 1,

3,

6,

9,and 1 2 months t h r e e cubes of each type were removed from t h e tank and the f i s h p a s s , d r i e d , weighed and oruehed.

The a u t h o r admits t h a t the s h o r t d u r a t i o n of the t e s t s prevented d e f i n i t e conclusions from being made but t h e r e were strong i n d i c a t i o n s t h a t

:

( a ) Type t t ~ " and type

"Xu

concretes were s u p e r i o r

t o type "N" i n r e s i s t a n c e t o peaty water a t t a c k , ( b ) Type "Att conorete behaved more c o n s i s t e n t l y than

type "X", but

it

may be p o s s i b l e t o improve t h e q u a l i t y of type "XI' beyond t h a t of type "A1', namely

by varying the cement:chemical r a t i o .

The author recommended t h a t a s an immediate p r a c t i c a l measure, a l l concretes exposed t o a c i d water a t t a c k should be of t h e a i r - e n t r a i n e d v a r i e t y , and t h a t a proper i n v e s t i g a t i o n should be made of chemical treatment of ordinary concrete

.

The paper e n t i t l e d "concrete i n Aggressive Waters and S o i l s ; Direotions f o r t h e Execution of Concrete worksn ( 2 ) out- l i n e s d i r e c t i o n s f o r t h e a o n s t r u c t i o n of concrete s t r u c t u r e s i n .

swamp a r e a s and marah waters a s w e l l a s giving advice on the

c o n s t r u c t i o n of such s t r u c t u r e s i n sea water. A l i s t i s included of v a r i o u s aggressive watera and m a t e r i a l s and t h e i r a c t i o n on concrete i s described. A number of general o o n s i d e r a t i o n s of i n t e r e s t t o t h i s r e p o r t a r e noted.

( i ) Running water i s more dangerous t h a n stagnant water because t h e harmful substances a r e c o n s t a n t l y renewed,

( i i ) The a t t a c k a t c o n s t a n t l y changing w a t e r l e v e l i s u s u a l l y s t r o n g e r t h a n t h e a t t a o k on p a r t s of s t r u c t u r e s c o n s t a n t l y under water. ( i i i ) F r e s h c o n c r e t e n o t y e t s d f i c i e n t l y hardened i s more a e n s i t i v e t o a t t a c k t h e n o l d hardened c o n c r e t e , ( i v ) A p r e v i o u s h a r d e n i n g i n a i r u s u a l l y i n c r e a s e 8 t h e r e s i s t a n c e of c o n c r e t e t o a g g r e s s i v e w a t e r s and s o i l s .

( v ) Concrete i s more r e s i s t a n t t h e more compact

it

is. Every enlargement of t h e a t tacked a r e a ( d e f e a t i v e j o i n t i n g , o r a c k a , s h a r p edges, e t c . ) f e o i l i t a t e s t h e a t t a c k .

I n a r e c e n t S o u t h A f r i c a n c o n t r i b u t i o n t o c o n c r e t e c o r r o s i o n s t u d i e s by van Aardt (I&), some l a b o r a t o r y e x p e r i m e n t s aimed a t a s s e s s i n g t h e r e s i s t a n c e of p o r t l a n d cement m o r t a r s t o a g g r e s s i v e a g e n t s a r e d e s c r i b e d and some p o s s i b l e measures f o r r e d u c i n g t h e i r v u l n e r a b i l i t y a r e suggested. I n h i s c o n c l u s i o n s t h e a u t h o r s t a t e s t h a t whenever c o n c r e t e i s t o be s u b j e c t e d t o a n a g g r e s s i v e environ- n e n t a well-designed p l a s t i c mix w i t h a low water:cement r a t i o

should be used and c a r e must be t a k e n

t o

o b t a i n f u l l compaction

i n o r d e r t o e n s u r e low p e r m e a b i l i t y . He p o i n t s o u t t h a t i t h a s been proven t h a t f a i r l y r i c h mixes a r e more r e s i s t a n t t o c o r r o s i o n t h a n l e a n ones, b u t t h e mix should n o t be t o o r i c h because t r o u b l e w i l l

t h e n be e x p e r i e n c e d due t o c r a z i n g and c r a c k i n g which w i l l i n c r e a s e p e r m e a b i l i t y . P e r v i o u s c o n c r e t e w i l l a l l o w c o r r o s i o n of r e i n f o r c i n g

s t e e l t o t a k e p l a c e .

P o r t l a n d cement c o n c r e t e p r o d u c t s a r e v e r y o f t e n inade- q u a t e l y aured and many f a i l u r e s a r e due t o t h i s cause. The

h y d r a u l i c b i n d e r r e q u i r e s m o i s t u r e f o r s t r e n g t h development, and i f d r y i n g out t a k e s plaoe soon a f t e r p l a c i n g , poor q u a l i t y and consequent v u l n e r a b i l i t y t o a g g r e s s i v e a g e n t s w i l l r e s u l t . Henue

i t i s e s s e n t i a l t o m a i n t a i n moist c o n d i t i o n s f o r

a

s u f f i c i e n t l e n g t h of time a f t e r p l a c i n g i f t h e c o n c r e t e i s t o a t t a i n i t s

maximum s t r e n g t h and r e s i s t a n c e t o an a g g r e s s i v e environment I t

should be r e a l i z e d t h a t g r e e n c o n m e t e i s much more v u l n e r a b l e t o a g g r e s s i v e a g e n t s t h a n i s w e l l matured c o n c r e t e . Therofore i n

some i n s t a n c e s

i t

may be n e c e s s a r y t o p r o v i d e s p e c i a l curing*

I n a d d i t i o n t o t h e above c o n s i d e r a t i o n s , t h e a u t h o r

p o i n t e d o u t t h a t it i s n e c e s s a r y a l s o t o choose t h e c o r r e c t t y p e of cement if optimum c o n d i t i o n s a r e t o be achievod f o r maximum r e s i s t a n c e t o c o r r o s i o n by a s p e c i f i c a g g r e s s i v e agent.

The

d u r a b i l i t y of c o n c r e t e i s i n f l u e n c e d a s well. by t h e t y p e and q u a l i t y of t h e a g g r e g a t e , ao t h e s e should be chosen w i t h c a r e .

a c i d a t t a c k i t was advantageous t o use a n a c i d s o l u b l e a g g r e g a t e . Furthermore, i f t h e a g g r e g a t e s show dimensional changes under t h e i n f l u e n c e of changes of m o i s t u r e c o n t e n t , t h e q u a l i t y of t h e c o n c r e t e i s lowered and c o r r o s i o n c a n be i n c r e a s g d .

Sam l i n p and Analysis of Boa Waters by t h e Nat i o n a l Research

&

--

I n t h e c o u r s e of c a r r y i n g o u t muskeg i n v e s t i g a t i o n s i n Northern Canada during t h e summer of

1955,

some e i g h t samples

of w a t e r from v a r i o u s muskeg c l a s s i f i c n t i o n t y p e s were o b t a i n e d by t h e D i v i s i o n of B u i l d i n g Resoarch. These samples were sub-

s e q u e n t l y a n a l y s e d by the D i v i s i o n of Applied Chemistry t o

determine t h o s e p r o p e r t i e s which might have a n a d v e r s e e f f e c t on c o n c r e t e . The a n a l y s e s were c a r r i e d out i n accordance w i t h t h e procedure l a i d down by Rodt

( l o ) *

The r e s u l t s a r e shown i n Table

I. Graphs showing t h e c o r r e l a t i o n be tween t h e p H d e t e r m i n a t i o n and f r e e C02, c o r r o s i v e C02, and c a r b o n a t e C02 k r e shown i n Figs. 1, 2 and

30

C onc l u s iona

I n a l l t h e p a p e r s reviewed t h e r e i s g e n e r a l agreement t h a t p e a t y s o i l s and bog w a t e r s have a c o r r o s i v e e f f e c t on

c o n c r e t e . It h a s been p o i n t e d out t h a t t h e pH d e t e r ~ n i n a t i o n i s a f a i r i n d i c a t o r of t h e degree of c o r r o s i o n . S u g g e s t i o n s f o r combating t h e e f f e c t of t h e s e c o r r o s i v e w a t e r s and s o i l s a r s remarkably s i m i l a r i n t h e v a r i o u s papers. I n s e v e r a l c a s e s c o n c r e t e made w i t h p o r t l a n d cement was found t o have a h i g h e r v u l n e r a b i l i t y t o c o r r o s i v e a c t i o n t h a n t h a t made w i t h c e r t a i n s p e c i a l cements ( s u c h a s h i g h alumina cements) o r w i t h a i r -

e n t r a i n e d c o n c r e t e . If p o r t l a n d cement c o n c r e t e i s t o be exposed t o a g g r e s s i v e a c t i o n , a r i c h mix i s d e s i r a b l e and adequate c u r i n g of t h e c o n c r e t e i s recommended b e f o r e i t i s brought i n t o c o n t a c t w i t h t h e source of c o r r o s i o n . Various s u r f a c e c o a t i n g s were found t o g i v e a c e r t a i n degree of p r o t e c t i o n t o the c o n c r e t e .

One of t h e few p o i n t s of disagreement i s t h e e f f e c t of t h e

a g g r e g a t e s on t h e r e s i s t a n c e of c o n o r e t e t o c o r r o s i o n . Tremper

(13)

doubts t h a t t h e a g g r e g a t e s have any e f f e c t a t a l l , whereas van Aardt

(14)

c o n s i d e r s them t o be q u i t e important. The paper by Dykerhoff

( 3 )

would appear t o confirm van A a r d t t s argumcnt.

To d a t e only a small number of bog w a t e r samples from Canadian muskegs have been o b t a i n e d s o t h a t one cannot draw any h a r d and f a s t c o n c l u s i o n s r e g a r d i n g t h e i r e f f e c t on c o n c r e t e .

There i s l i t t l e r e a s o n t o b e l i e v e t h a t t h e e s s e n t i a l c h a r a c t e r i s t i c s of t h e s e a g g r e s s i v e w a t e r s a r e any d i f f e r e n t from t h o s e of p e a t y

w a t e r s i n o t h e r c o u n t r i e s . Theref o r e , recommendations a s out- l i n e d i n t h e v a r i o u s p a p e r s f o r t h e c o n s t r u c t i o n of c o n c r e t e

s t r u c t u r e s i n a c i d i c w a t e r s and s o i l s should a p p l y e q u a l l y w e l l t o t h e muskeg a r e a s of Canada a s elsewhere.

Nothing h a s been s a i d of t h e use of a c i d i c water f o r t h e mixing of c o n c r e t e , w i t h t h e e x c e p t i o n of r e f e r e n c e ( 2 ) which

s p e c i f i o a l l y a d v i s e s a g a i n s t i t s use. A t a l o c a t i o n where t h e only r e a d i l y a v a i l a b l e supply of water i s t h a t w i t h a c e r t a i n degree of a c i d i t y , i t may, of n e c e s s i t y , have t o be used. I n such a c a s e i t would be a d v i s a b l e t o t r e a t t h e w a t e r t o r e n d e r

it n e u t r a l b e f o r e u s i n g i t t o mix c o n c r e t e . References

Alway, F. J. D i s i n t e g r a t i o n of Cement T i l e i n P e a t . J o u r n a l , American P e a t S o c i e t y ,

15:3

:15-25. 1922.

Concrete i n Aggressive Waters and S o i l s : D i r e c t i o n s f o r t h e Execution of Concrete Work, ( T r a n s l a t e d from t h e German) D.S .I .Re, B u i l d i n g Research S t a t i o n , L i b r a r y Communication

No. 524, January,

1954.

Dykerhoff R e T e s t a of Concrete

i n

Marsh Water. Cement, v,

17,

pp.

b6-7.

1912. Also Chem. A b s t r a c t s , v.

6,

p. 1832. E l l i o t , G.R.B. E f f e c t of Organic Decomposition P r o d u c t s from

High Vegetable Content S o i l s Upon Concrete Drain T i l e . J o u r n a l of Agric

.

Research, 24:6 :471-500

.

1923

m a s e r , DID. The D u r a b i l i t y of Concrete i n P e a t y Water.

C h a r t e r e d C i v i l Engineer, B u l l e t i n of t h e I .C .E., pp.

11-a.

Septe

1955.

Halcrow, W e T o Some Problems of t h e Design of Concrete Dams: D e t e r i o r a t i o n Due t o Moorland Water. Water and Water

Engineering,

36:434:311-318,

345-353.

Midsummer,

1934.

Halcrow, W.T., O.B. Brook and R e Preston. The Corrosive Attack

of Moorland Water on Concre t e e The Engineer,

146

:3805:664-6650 Dec.

14,

1928.

M i l l e r , D.G. and POW. Manson. D w l a b i l i t y of Concretes and Mortars i n Acid S o i l s w i t h P a r t i c u l a r Reference t o Drain T i l e .

Univ, of Minnesota, Agric. Expl t , S t a t i o n , Teoh, B u l l e t i n 180,

9.

M i l l e r , D.G., and P.W. Manson. E s s e n t i a l C h a r a c t e r i s t i c s of Durable Concrete D r a i n T i l e f o r Acid S o i l s . A g r i c u l t u r a l Engineering, ppr

437-!&La

October,

1948,

10. Rodt, V. T r a n s l a t i o n of a n A r t i c l e on A n a l y s i s of Bog Water Corroding Concrete. Bord na Mona Experimental S t a t i o n ,

E . S , T r a n a l a t i o n No.

33,

I r e l a n d ,

1955.

11. S t e w a r t , J.T. D u r a b i l i t y of Concrete T i l e i n Peat. J o u r n a l , American P e a t s o c i e t y , 15:3:26-32, 1922.

12. The Corrosive Attack of Moorland Water on Concrete. The Surveyor,

74:1927

2571-573

s D ~ c 28, 1928.

13.

Tremper, Bailey. The E f f e c t of Acid Waters on Concrete. Arner. Conc. I n a t . Jour., 3:l:l-32, Sept., 1931.

14.

van Aardt, J.H.Po The R e s i s t a n c e of Concrete and Mortar t o Chemical Attack

--

P r o g r e s s Report on Concrete C o r r o s i o n S t u d i e s . South A f r i c a (Council f o r S c i e n t i f i c and

I n d u s t r i a l Research), N a t i o n a l B u i l d i n g Research I n s t i t u t e , B u l l e t i n No.

13,

pp.

44-80,

March,

1955.

Table I

Analysis of Bog Waters

Sample No* M l - l W M 2 - 1 W

M 3 - 1 W

a - 3 ~

~4-&W

N&-SW NlS-I\V .V:j'-l:j~V

1

:

Wan.

Flin

_Lynn

1

_{~ i ~ d , ! B i r d ,}

I

_{J3i1-d~ j Knc)b Kric~b}

1

Loca t l o n Port., Flon, Lake, Man. Man. Idan. L a l r e , L R ~ C C P ~ '

I Man.,

Man.

Man.

P

,

CJ , _P ,h 14, ,,

---...."*-

."--.

-a",.

-7

Muskeg TypeQ I BE1

!

A E I

/

CDI

I

DFB

CI

/

BI-

FEJ

PI-

I

I T - " - - C " . ..--I".- I(

' ~ r e e H2S04

,

---

n i l

---

I

n i l

I

---

1

n i l

i

---

n .il.

i

I

" ~ a d f orth, N O W . A Suggested C l a s s i f i c a t i o n of Muskeg f o r tlm

Engineer. The Engineering J o u r n a l ,

35:

11. Nov. 1952.

i 1 i _i

-

: i

I

--j

- m y I nf 1 n i l

i

---

1

n i l

i

I 1 I ? ; Free Organic i Acfda I

- -

!

n i l

1

---

I

p H DETERMINATION

FIGURE

I

pH DETERMINATION

FIGURE

2

FIGURE 3