Methods for rating concrete waterproofers

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Methods for rating concrete waterproofers

NATIONAL RESEARCH C O U N C I L CANADA

D I V I S I O N OF B U I L D I N G RESEARCH

METHODS FOR R A T I N G CONCRETE WATERPROOFERS by

F.

K o c a t e s k i n and E o G o Swenson R e p o r t N o . 112 of the D i v i s i o n o f B u i l d i n g R e s e a r c h O t t a w a January,

1957

PREFACE

The value o f v a r i o u s compounds which have been proposed f o r u s e i n r e n d e r i n g c o n c r e t e w a t e r p r o o f h a s l o n g been d e b a t e d , and adequate methods f o r e v a l u a t i n g water- p r o o f e r s a r e b a d l y needed. Such e v a l u s t i o n i s made

d i f f i c u l t n o t s o much by t h e w a t e r p r o o f e r s t h e m s e l v e s a s by the c o m p l e x i t i e s of t h e movement of w a t e r i n m a t e r i a l s . Any s t u d y of w a t e r p r o o f e r s i s t h e r e f o r e mainly a s t u d y of w a t e r i n m a t e r i a l s and methods of e v a l u a t i o n c a n be

s u c c e s s f u l o n l y t o t h e e x t e n t t h a t t h e y a r e r e a l i s t i c i n r e s p e c t of t h e v a r i o u s c o n d i t i o n s under which w a t e r may be c a u s e d t o move.

The D i v i s i o n h a s been w e l l aware f o r some time o f t h e need f o r f u r t h e r i n f o r m a t i o n on w a t e r p r o o f e r s . Only t h e p r e s s u r e of o t h e r u r g e n t problems h a s p r e v e n t e d t h e development of a s u b s t a n t i a l program of work i n t h i s f i e l d . It was w i t h a g r e a t d e a l o f p l e a s u r e , t h e r e f o r e , t h a t

arrangements were made f o r t h e f i r s t - n a m e d a u t h o r , h o l d e r of an N.R.C. P o s t d o c t o r a t e F e l l o w s h i p , t o work i n t h e B u i l d i n g M a t e r i a l s Laboratory on a s u b j e c t t h a t was of mutual i n t e r e s t . D r . Kocataskin, a C i v i l E n g i n e e r from t h e s t a f f o f the T e c h n i c a l U n i v e r s i t y of I s t a n b u l , was t h e f i r s t p o s t d o c t o r a t e f e l l o w t o come t o t h e D i v i s i o n . The v e n t u r e was a most happy and m u t u a l l y p r o f i t a b l e one a s t h i s r e p o r t w i l l i n d i c a t e .

Ottawa

SUMMARY

-

A combination of s e v e r a l s i m p l e , p r a c t i c a l t e s t s were used a s a p r o c e d u r e f o r e v a l u a t i n g i n t e g r a l and s u r f a c e

w a t e r p r o o f e r s f o r c o n c r e t e , The t e s t s were s e l e c t e d on t h e b a s i s of t h e v a r i o u s p o s s i b l e m o i s t u r e c o n d i t i o n s t h a t might pose problems i n t h e f i e l d . , and. c o n s i s t e d o f : ( a ) t h e d r y - cup t e s t f o r vapour p e r m e a b i l i t y , ( b ) s a t u r a t e d p e r m e a b i l i t y under a s m a l l head, ( c ) c a p i l l a r y a b s o r p t i o n t e s t , ( d ) evapo- r a t i o n t e s t , and ( e ) combined c a p i l l a r y - e v a p o r a t i o n t e s t , The t e s t s were l i m i t e d t o i s o t h e r m a l c o n d i t i o n s , one cement, two mixes, and a l i m i t e d number of w a t e r p r o o f i n g a g e n t s .

The d i f f e r e n c e s i n t h e e f f e c t s o f a w a t e r p r o o f e r u n d e r t h e d i f f e r e n t t e s t c o n d i t i o n s show t h a t a s i n g l e t e s t , s u c h a s t h e s a t u r a t e d p e r m e a b i l i t y t e s t , d o e s n o t p r o v i d e f o r an a d e q u a t e , n o r a f a i r , a p p r a i s a l o f s u c h m a t e r i a l s , The

combined t e s t s i n d i c a t e t h e s p e c i a l m o i s t u r e c o n d i t i o n s u n d e r which a g i v e n a g e n t may be h e l p f u l , u s e l e s s , o r even harmful.

I t must be r e c o g n i z e d , however, t h a t o t h e r p r o p e r t i e s , s u c h as d u r a b i l i t y , r e s i s t a n c e t o c o r r o s i o n , s t r e n g t h , and w o r k a b i l i t y , r e q u i r e s u p p l e m e n t a r y t e s t i n g i n t h e e v a l u a t i o n o f w a t e r p r o o f i n g a g e n t s .

METHODS FOH RATING CONCRETE WATERPROOFERS b y F'. K o c a t a s k i n and E. G. Swenson I. INTRODUCTION 1. G e n e r a l The u s e o f w a t e r p r o o f i n g a d m i x t u r e s i n m o r t a r s a n d c o n c r e t e h a s become v e r y w i d e s p r e a d i n r e c e n t y e a r s . A l t h o u g h t h e b e n e f i t s t o b e d e r i v e d f r o m t h e i r u s e a r e s e r i o u s l y q u e s t i o n e d by many c o n c r e t e e x p e r t s , t h e r e h a v e b e e n r e l a t i v e l y few a t t e m p t s t o d e v e l o p s a t i s f a c t o r y methods of r a t i n g t h e e f f e c t i v e n e s s of t h e s e m a t e r a i a l s . I t i s c l e a r t h . a t w a t e r - p r o o f e r s w i l l c o n t i n u e t o be u s e d i n c o n c r e t e s and m o r t a r s , and i t i s becoming e v i d . e n t t h a t t h e i n c r e a s i n g number a n d v a r i e t y of' s u c h m a t e r i a l s on t h e m a r k e t , and t h e wide c l a i m s b e i n g made f o r them, make i t n e c e s s a r y t o r e - e v a l u a t e t h e methods h i t h e r t o employed a.nd t h e c o n c l u s i o n s drawn f r o m p r e v i o u s i n v e s t i g a t i o n s .

A l t h o u g h good c o n c r e t e i s impermeable t o l i q u i d w a t e r i n a g e n e r a l s e n s e , m o i s t u r e c a n p a s s t h r o u g h it b y b o t h l i q u i d and v a p o u r f l o w o r by a c o m b i n ~ t i o n o f t h e two a s , f o r example, when w a t e r i s drawn i n b y c a p i l l a r i t y a t one s u r f a c e and e v a p o r a t e s a t t h e o t h e r s u r f a c e . A w a t e r p r o o f i n g a g e n t may n o t b e e f t ' e c t i v e i n t h e one c a s e b u t may b e e f f e c t i v e i n t h e o t h e r . T h e r e f o r e , d i s t i n c t i o n must be made between

w a t e r p r o o f ' e r s a n d damp-pr0ofe1.s. The i n f l u e n c e o f such a g e n t s on a b s o r p t i o n of w a t e r may a l s o b e s i g n i f i c a n t i n r e l a t i o n t o d u r a b i l i t y t o f r o s t .

D e s p i t e t h e f a c t t h a t t h e t e c h n i c a l r e q u i r e m e n t s f o r making good impermeable c o n c r e t e a r e w e l l known, i t i s v e r y o f t e n n o t a c h i e v e d i n t h e f i e l d . The v a l u e of w a t e r p r o o f e r s i n s u c h s i t u a t i o n s i s n o t c l e a r l y e s t a b l i s h e d .

The p r e s e n t i n v e s t i g a t i o n was u n 2 e r t a k e n i n a n a t t e m p t t o d e v e l o p t e s t methods f o r

rat in^

t h e e f f e c t i v e n e s s o f

p r o p r i e t a r y w a t e r p r o o f e r s , k e e p i n g i n mind f i e l d r e q u i r e m e n t s and t h e n a t u r e oi' t h e a g e n t s t h e m s e l v e s . The methods u s e d a r e n o t c l a i m e d t o be t h e f i n o 1 s o l u t i o n b u t i t i s hoped t h a t t h e p r e s e n t sturly w i l l s e r v e a s a b a s i s f o r f u r t h e r d e v e l o p - ment i n t h i s f i e l d .

2. The Problems

W a t e r p r o o f i n g a d m i x t u r e s o r s u r f a c e t r e a t m e n t s have b e e n m a i n l y a s s o c i a t e d w i t h p r e v e n t i o n o f l i q u i d f l o w t h r o u g h t h e c o n c r e t e a s a r e s u l t of a h y d r o s t a t i c h e a d . C l a i m s a r e made f o r many p r o p r i e t a r y m a t e r i a l s t h a t t h e y p r e v e n t damp- n e s s i n basement f l o o r s and w a l l s and s t o p r a i n p e n e t r a t i o n .

O f added i n t e r e s t i s t h e p o s s i b l e e f f e c t o f s u c h a g e n t s i n r e d u c i n g e f f l o r e s c e n c e , s t a i n i n g , and f r o s t damage t h r o u g h w a t e r a b s o r p t i o n on e x p o s e d c o n c r e t e , m o r t a r , o r cement-base r e n d e r i n g s . Under most f i e l d c o n d i t i o n s t h e c o n c r e t e i s n o t s u b j e c t e d t o h i g h w a t e r p r e s s u r e s and i s n o t i n a c o m p l e t e l y s a t u r a t e d c o n d i t i o n . I t may be s u b j e c t e d t o a s m a l l w a t e r p r e s s u r e on one s i d e and t o a i r on t h e o t h e r s i d e . A small h y d r o s t a t i c h e a d o f w a t e r w i l l t h e n f o r c e w a t e r i n a s h o r t d i s t a n c e on one s i d e t h r o u p h t h e l a r g e p o r e s . F u r t h e r l i q u i d i'low i n t o t h e m a t e r i a l i s g e n e r a t e d by t h e s u c t i o n p r o p e r t i e s o f t h e m a t e r i a l . T h i s s u c t i o n , o r m o i s t u r e - r e t a i n i n g p r o p e r t y o f a p o r o u s m a t e r i a l , i s t h e r e s u l t of a c o m b i n a t i o n o f f o r c e s s u c h a s s u r f a c e a d s o r p t i o n , c a p i l l a r i t y , and s o l u t i o n . The s u c t i o n o f a c o m p a r a t i v e l y d r y m a t e r i a l c a n b e v e r y h i g h , e q u i v a l e n t i n some c a s e s t o 1 0 , 0 0 0 l b . p e r sq. i n . o f p r e s s u r e o r e q u i v a l e n t t o a h y d r a u l i c h e a d 01' t h o u s a n d s o f f e e t o f w a t e r , I n a c o m p l e t e l y s a t u r a t e d sample t h e s u c t i o n would be z e r o . The s u c t i o n of' a m a t e r i a l may a l s o be con-

s i d e r e d a s a measure of t h e m a g n i t u d e o f p r e s s u r e d i f f e r e n c e between t h e a t m o s p h e r i c p r e s s u r e and t h a t of t h e " h e l d " w a t e r , t h e l a t t e r b e i n g a l w a y s t h e l e s s e r . The e x t e n t a n d r a t e of c a n i l l a r i t y i s d e t e r m i n e d n o t o n l y by t h e s u c t i o n p r o p e r t i e s of t h e m a t e r i a l s b u t a l s o b y t h e r a t e of e v a p o r a t i o n o r v a p o u r f l o w , The p l a n e o f e v a p o r a t i o n i s e s t a b l i s h e d by p o r e s i z e and t h e r e l a t i v e r a t e s i n v o l v e d . The c o n v e n t i o n a l p e r m e a b i l i t y t e s t u s i n g h i g h h y d r o s t a t i c p r e s s u r e s , and c o n d u c t e d u n d e r s a t u r a t e d c o n d i t i o n s , simu- l a t e s , t h e r e f o r e , o n l y one of s e v e r a l p o s s i b l e s i t u a t i o n s , and i s s t r o n g l y s u s p e c t e d o f b e i n g i n a d e q u a t e as a method f o r r a t i n g t h e e f f e c t i v e n e s s o f w a t e r p r o o f i n g and d a m p - p r o o f i n g m a t e r i a l s . The p r o b l e m s i n v o l v e d i n p r o p e r l y e v a l u a t i n g t h e s e m a t e r i a l s must b e c l e a r l y r e c o g n i z e d . R e f e r e n c e h a s a l r e a d y b e e n made t o t h e p o s s i b i l i t y o f v a r i o u s t y p e s o f m o i s t u r e

s i t u a t i o n s e a c h o f which depend on boundary c o n d . i t i o n s . M o i s t u r e may b e t r a n s f e r r e d t h r o u g h c o n c r e t e a s a r e s u l t of v a p o u r f l o w , l i q u i d f l o w , o r a c o m b i n a t i o n of t h e two,

d e p e n d i n g on t h e d e g r e e o f s a t u r a t i o n and, t h e r e f o r e , t h e s u c t i o n p r o p e r t i e s o f t h e m a t e r i a l . Each of' t h e s e mechanisms

s e p a r a t e l y o r t o g e t h e r , c a n g i v e r i s e t o f i e l d s i t u a t i o n s which a r e u n d e s i r a b l e and t h e i n f l u e n c e of w a t e r p r o o f i n g i n

e a c h o f t h e s e ca.ses, w h e t h e r i n t e g r a l o r s u r f a c e t y p e , i s o f i m p o r t a n c e i n view o f t h e v a r i e t y of c l a i m s made f o r s u c h m a t e r i a l s .

A second problem i s c r e a t e d by t h e l a r g e number and v a r i e t y o f w a t e r p r o o f e r s on t h e m a r k e t . Most of t h o s e m a t e r i a l s , f r o m c h e m i c a l a n a l y s e s , a p p e a r t o f a l l i n t o a l i m i t e d number of c l a s s e s , however, which may somewhat

s i m p l i f y t h e development of t e s t methods. Such c l a s s e s a r e : a c c e l e r a t o r s ( c a l c i u m c h l o r i d e t y p e ) , w a t e r r e p e l l e n t s

( s t e a r a t e t y p e ) , b i t u m i n o u s m a t e r i a l s , s i l i c o n e s , and o t h e r l e s s w e l l - d e f i n e d g r o u p s . Some a g e n t s , however, c o n t a i n more t h a n one o f t h e above-mentioned b a s i c i n g r e d i e n t s , and i t i s a l s o q u i t e p o s s i b l e t h a t t h e f o r m u l a f o r a g i v e n p r o p r i e t a r y m a t e r i a l may be changed p e r i o d i c a l l y by t h e m a n u f a c t u r e r . A t h i r d c o m p l i c z t i o n a r i s e s f r o m t h e v a r i a t i o n s i n t h e c o n c r e t e i t s e l f . D i f f e r e n t m i x e s may p r o d u c e d i f f e r e n t p o r e s i z e s and d i s t r i b u t i o n s which i n t u r n r e s u l t i n d i f f e r e n t f l o w c h a r a c t e r i s t i c s . F o u r t h l y , a g i v e n a d m i x t u r e may behave d i f f e r e n t l y w i t h d i f f e r e n t cements. I t i s known, f o r example, t h a t

c a l c i u m c h l o r i d e i s more e f f e c t i v e i n a c c e l e r a t i n g h y d r a t i o n f o r some c e m e n t s t h a n f o r o t h e r s .

I n c o n s i d e r i n g t h e development of e v a l u a t i o n p r o c e d u r e s i t was a c c e p t e d t h a t more t h a n one t y p e of t e s t m i g h t be

r e q u i r e d and t h a t t e s t s m i g h t have t o b e s e l e c t e d t o t a k e a c c o u n t of t h e above-mentioned problems. Q u i t e s e p a r a t e f r o m t h e p r o b l e m o f d e v e l o p i n g s a t i s - f a c t o r y methods of r a t i n g i n t e g r a l w a t e r p r o o f e r s i s t h e m a t t e r of t h e i n f l u e n c e o f t h e s e m a t e r i a l s on t h e d u r a b i l i t y of c o n c r e t e and m o r t a r . The s c o p e of t h e p r e s e n t i n v e s t i g a t i o n d i d n o t p e r m i t a s t u d y of t h i s a s p e c t o f t h e p r o b l e m o r o f t h e d u r a b i l i t y of t h e s u r f a c e w a t e r p r o o f o r s t h e m s e l v e s b u t t h e y a r e r e c o g n i z e d a s b a s i c c o n s f d e r a t i o n s i n t h e o v e r - a l l e v a l u a t i o n o f t h e s e m a t e r i a l s . P r e v i o u s I n v e s t i p a t i o n s

3 -

-

A coniprehensive s t u d y o f t h e more r e c e n t l i t e r a t u r e i n d i c a t e s t h a t l i t t l e p r o g r e s s h a s b e e n made i n d e v e l o p i n g s i m p l e b u t c o m p r e h e n s i v e methods o f t e s t which t a k e i n t o a c c o u n t a l l t h e f a c t o r s d i s c u s s o d above. The method most cormnonly u s e d m e a s u r e s s a t u r a t e d p e r m e a b i l i t y u n d e r hydro- s t a t i c head. C a p i l l a r y a b s o r p t i o n i s measured i n some c a s e s , b u t no s e r i o u s a t t e m p t h a s b e e n made t o c o v e r t h e v a r i o u s m o i s t u r e s i t u a t i o n s , t h e v a r i o u s c l a s s e s of a d m i x t u r e s , and t h e v a r i a t i o n i n p e r f o r m a n c e of a d m i x t u r e s u n d e r d i f f e r e n t mix c o n d i t i o n s .

I n t e g r a l W a t e r p r o o f e r s .

-

The more r e c e n t comprehensive i n v e s t i g a t i o n s i n v o l v e m a i n l y w a t e r p r e s s u r e and a b s o r p t i o n

(1, 2,

3, 4 ) .

They a g r e e g e n e r a l l y t h a t a d m i x t u r e s s u c h a s s o a p s , c e l l u l o s e wax, f a t t y a c i d s , v a s e l i n e , potroleurn

o i l s , b u t y l s t e a r a t e , n a p h t h a l e n e and c o a l t a r do n o t d e c r e a s e h y d r o s t a t i c f l o w and may even i n c r e a s e i t u n d e r h i g h p r e s s u r e s , These m n t e r i ~ l s g e n e r a l l y r e d u c e a b s o r p t i o n b u t a l s o r e d u c e compre s s i v e s t r e n g t h s . h r o r k a b i l i t y i s u s u a l l y improved

( 3 ) ,

Calcium c h l o r i d e d o e s n o t r e d u c e h y d r o s t a t i c f l o w o r a b s o r p - t i o n , b u t f i l l e r s do a p p e a r t o r e d u c e h y d r o s t a t i c f l o w ( I ) , a l t h o u g h t h e y have l i t t l e e f f e c t a s damp-proofers

( 5 ) .

The u s e of v e r y s m a l l amounts of w a t e r - r e p e l l e n t m a t e r i a l s c a n r e d u c e c a p i l l a r y s u c t i o n

( 3 ) .

R a t h e r e x t e n s i v e d i s c u s s i o n s o f t h e m e r i t s of v a r i o u s i n t e g r a l w a t e r p r o o f e r s a r e r e p o r t e d f o r c o n c r e t e

( 5 ) and u n i t masonry

( 6 ) .

The methods u s e d , however, do n o t c l e a r l y d i f f e r e n t i a t e between i n i t i a l e f f e c t s and t h e h p h a v i o u r a f ' t e r cons l d e k a b l e t i m e l a p s e .

S u r f a c e W a t e r p r o o f e r s .

-

T e s t methods f o r r a t i n g s u r f a c e w a t e r p r o o f e r s have been g e n e r a l l y l i m i t e d t o mo asuroments

o f : ( a ) h y d r o s t a t i c p r e s s u r e r a n g i n g from h i g h p r e s s u r e s

( 7 )

t o v e r y low w a t e r h e a d s

( 8 ,

91, and i n c l u d e v a r i a t i o n i n

p r e s s u r e s ( 1 0 ) ; ( b ) a b s o r p t i o n (1,

4,

11); and ( c ) a b s o r p t i o n and evaporation ( 1 2 ,

13,

I&). The i n f l u e n c e o f w a t e r p r o o f e r s on p e r m e a b i l i t y of masonry w a l l s t o w i n d r d r i v e n r a i n h a s been c a r r i e d o u t on w a l l e t t e s

(15).

The m e r i t s o f t h e v a r i o u s t y p e s of' s u r f a c e w a t e r p r o o f e r s , a s r e p o r t e d by t h e s e i n v e s t i - g a t o r s , a r e n o t w e l l - d e f i n e d , u n q u e s t i o n a b l y t h e r e s u l t of v a r i a t i o n s i n methods of a p p l i c a t i o n , d e g r e e s of e x p o s u r e t o which t h e samples were s u b j e c t e d , and o t h e r d i f f e r e n c e s i n t e s t methods. The d u r a b i l i t y o f s u r f a c e c o a t i n g s i s , o f c o u r s e , a v e r y i m p o r t a n t c o n s i d e r a t i o n . O f c o n s i d e r a b l e economic s i g n i f i c a n c e a r e t h e r e s u l t s o f methods t h a t compare t h e e f f i c i e n c y of p r o p r i e t a r y s u r f a c e w a t e r p r o o f e r s w i t h o r d i n a r y cement g r o u t o r n e a t cement p a s t e

( 7 , 8,

91, C o n s i d e r a b l e g e n e r a l i n f o r m a t i o n i s a v a i l a b l e on c o r n p o s i ~ i o n , m a n u f a c t u r e , d u r a b i l i t y and methods of a p p l i c a t i o n of' s u r f a c e w a t e r -

p r o o f e r s ( 1 6 ,

1 7 ,

10, 19, 2 0 ) . The e v a l u a t i o n of a s i m p l e b u t s a t i s f a c t o r y t e s t p r o c e d u r e , on t h e b a s i s o f f i e l d c o n d i t i o n s , and on t h e b a s i s of m a n u f a c t u r e r s t c l a i m s , h a s , however, n o t a p p e a r e d i n p u b l i s h e d r e p o r t s . I1 INITIAL CONSIDERATIONS

-

_-

1. Nature of C o n c r e t e Good mix d e s i g n f o r c o n c r e t e r e q u i r e s t h a t , a f t e r compaction, t h e cement-paste constituent w i l l c o m p l e t e l y c o a t t h e s u r f a c e s of t h e a g g r e g a t e p a r t i c l e s and f i l l t h e v o i d s between them. S i n c e a h i g h cement c o n t e n t i s u s u a l l y u n d e s i r a b l e , a minimum q u a n t i t y i s a c h i e v e d by p r o p e r g r a d i n g

of a g p r e e a t e s . The w e l l - c o m p a c t e d , h a r d e n e d c o n c r e t e i s t h e n a s o l i d containing a n a g v e p a t e p o r e s y s t e m , u s u a l l y v e r y f i n e , w h i c h i s c h a r a c t e r i s t i c o f t h a t a g g r e g a t e , and a cement- p a s t e p o r e s y s t e m t h a t v a r i e s w i t h w a t e r - c e m e n t r a t i o , d e g r e e of c o m p a c t i o n , d e g r e e o t ' h y d r a t i o n , cmd t y p e o f cement ( 2 1 ) . The g e l p o r e s a r e t h e u l t r a - f i n e p o r e s t h a t a r e c h a r a c t e r i s t i c o f t h e cement a n d a r e e s s e n t i a l l y i n d e p e n d e n t of e x t e r n a l t r e a t m e n t . They p l a y o n l y a m i n o r r o l e i n t h e t r a n s ~ o r t of m o i s t u r e t h r o u g h c o n c r e t e

.

The c a p i l l a r y p o r e s a r e s c a t t e r e d p o c k e t s and c l ~ a n n e l s , s o w of which a r e i s o l a t e d and some i n t e r c o n n e c t e d , d e p e n d i n g on t h e i n i t i a l w a t e r - c e m e n t r a t i o , t h e d e g r 2 e of h y d r a t i o n ( a g e ) , and t h e d e g r e e o f com- p a c t i o n . They a r e l s r g e r t h a n t h e ye1 p o r e s , v a r y f r o m v e r y f i n e t o v e r y l a r g e v o i d s , and a r e r e s ~ o n s t b l e f o r t h e d e g r e e of' p e r m e a b i l i t y or' t h e c o n c r e t e ( 2 2 ) . The ? o r e s o f t h e

a g ~ r e g a t e s a r e u s u a l l y s o f i n e t h a t t h e y do n o t a f f e c t t h e o v e r - a l l p e r m e a b i l i t y or' c o n c r e t e

.

Owing t o t h e a f f i n i t y f o r m o i s t u r e o f t h e s u r f a c e s i n t h e c e m e n t - p a s t e v o i d s , t h e y a r e u s u a l l y p a r t l y f i l l e d w i t h w a t e r , t h e e q u i l i b r i u m m o i s t u r e c o n t e n t b e i n e d e n e n d e n t on

t e m p e r a t u r e , h u m i d i t y c o n d i t i o n s , and t h e age and d e g r e e o f h y d r a t i o n o f t h e c o n c r e t e . \!ater may be t r a n s f e r r e d t h r o u g h t h e p o r o u s s y s t e m by v a p o u r f l o w i n d u c e d b y a v a p o u r p r e s s u r e d i f f e r e n t i a l u n d e r c o n d i t i o n s of low m o i s t u r e c o n t e n t , s n d b y l i q u i d f l o w u n d e r s a t u r a t e d c o n d i t i o n s . B o t h mechanisms a r e b e l i e v e d t o o p e r a t e u n d e r p a r t i a l l y s a t u r a t e d c o n d i t i o n s . O t h e r a c c i d e n t a l means f o r w a t e r t r a n s f e r t h r o u z h c o n c r e t e , s u c h a s c r > a c k s , honeycombing, and j o i n t s , a r e c a s e s i n which t h e u s u a l t y p e o f i n t e g r a l w a t e r p r o o f e r c a n n o t be c l a i m e d t o p r o v i d e a remedy. They a r e t h o r e f o r e n o t c o n s i d e r e d i n t h e p r e s e n t s t u d y a l t h o u r h t h e y d o c o n s t i t u t e a n i m p o r t a n t f i e l d problem. 2. D i f f e r e n t C a s e s o f M o i s t u r e Plow and. S e l e c t i o n o f T e s t C o n d i t i o n s The e q u i l i b r i u m m o i s t u r e c o n t e n t of c o n c r e t e i s con- s i d e r a b l y i n f l u e n c e d b y t e m p e r a t u r e . R e c e n t i n v e s t i g a t i o n s have a l s o shown t h a t i n c o n c r e t e , a s i n some o t h e r m a t e r i a l s , m o i s t u r e may move t h r o u g h t h e i n f l u e n c e o f a t e m p e r a t u r e

g r a d i e n t b e t w e e n d i f f e m n t p o i n t s i n the c o n c r e t e ( 2 3 , 2 4 ) . The i n t ' l u e n c e o f chan,ges i n t e m p e r a t u r e conditions on t h e e f f e c t i v e n e s s of waterproofing a g e n t s would c o n s t i t u t e a r a t h e r e x t e n s i v e r e s e a r c h p r o p a m . The p r e s e n t s t u d y was t h e r e f o r e r e s t r i c t e d t o i s o t h e r m a l c o n d i t i o n s . M o i s t u r e f l o w u n d e r i s o t h e r r n a l c o n d i t i o n s may t a k e p l a c e i n s e v e r a l d i f f e r e n t ways d e p e n d i n g on b o u n d a r y c o n d i t i o n s , Vapour p e r m e a b i l i t y r e f e r s t o one e x t r e m e c a s e where m o i s t u r e e n t e r s a m a t e r i a l a s v a p o u r and l e a v e s i t a s v a p o u r ( 2 5 , 2 6 , 27, 2 8 , 29,

30,

7 1 , 32,

33,

34,

35,

3 6 ) .

I t i s a f o r m o f u n s a t u r a t e d p e r m e a b i l i t y . S a t u r a t e d p e r m e a b i l i t y r e f e r s t o t h e o t h e r e x t r e m e s i t u a t i o n where t h e m o i s t u r e e n t e r s a s a l i q u i d and l e a v e s i t a s a l i q u i d , t h e m a t e r i a l b e i n g e s s e n t i a l l y i n a s a t u r a t e d c o n d i t i o n

( 3 7 , 38,

39, 4 0 ,

41,

4.2,

43).

T h i s t y p e o f f l o w mag b e i n d u c e d by a h y d r o s t a t i c head. M o i s t u r e f l o w s i t u a t i o n s , w h i c h may b e c o n s i d e r e d a s i n t e r m e d i a t e c a s e s , i n v o l v e a b s o r p t f o n b y c a p i l l a r i t y

(44,

!45¶

4.6,

l4.7,

4 8 , 4 9 ) , a f o r m o f u n s a t u r a t e d p e r m e a b i l i t y where b o t h v a p o u r f l o w and l i q u i d f l o w o c c u r , a n d d r y i n g b y e v a p o r a t i o n ( 5 0 ,

51,

5 2 ,

53)

i n w h i c h v a p o u r f l o w o c c u r s . C a p i l l a r i t y and e v a p o r a t i o n c a n , o f c o u r s e , o p e r a t e a t t h e same t i m e . If an i n t e e r a l w a t e r p r o o f ' e r o r a s u r f a c e w a t e r ~ r o o f e r i s t o b e e v a l u a t e d on t h e b a s i s o f i t s e f l ' e c t i v e n e s s i n d e c r e a s i n g t h e f l o w o f m o i s t u r e , i t i s n e c e s s a r y t o s t u d y i t s i n f l u e n c e f o r e a c h of t h e s e v e r a l p o s s i b l e c a s e s . The u s u a l h y d r o s t a t i c f l o w t e s t would oDpear t o be i n a d e q u a t e ; t h e same a p p l i e s t o t h e s i m p l e a b s o r p t i o n t e s t . I t i s c l e a r t h a t p r o p e r e v a l u a t i o n c a n be a c h i e v e d o n l y b y a s e r i e s o f t e s t s c o v e r i n g t h e c a s e s m e n t i o n e d above. I n t h e f o l l o w i n g i n v e s t i g a t i o n f i v e s e p a r a t e t e s t s h a v e been s e l e c t e d : 1. v a p o u r p e r m e a b i l i t y ; 2. s a t u r a t e d p e r m e a b i l i t y ;

3.

c a n i l l a r y a b s o r p t i o n ;

4.

d r y i n g b y e v a p o r a t i o n ; and

5.

combined c a p i l l a r i t y and e v a p o r a t i o n . I n i t i a l l y t h i s s e r i e s o f t e s t s was c h o s e n f o r p u r p o s e s o f i n v e s t i g a t i o n a n d i t was r e c o g n i z e d t h a t t h e d a t a o b t a i n e d would v e r y l i k e l y s u g g e s t c e r t a i n m o d i f t c a t i o n s f o r ac t u 8 1 t e s t i n g p u r p o s e s .

3.

S e l e c t i o n o f l i l a t e r p r o o f ' e r s S i n c e t h e p r e s e n t i n v e s t - l g a t i o n was d i r e c t e d t o w a r d t h e d e v e l o p m e n t o f s i m n l e m e t h o d s o f t e s t !,ased on p o s s i b l e f i e l d s i t u a t i o n s o f m o i s t u r e t r a n s f e r , t h e w a t e r p r o o f ' i n z a g e n t s u s e d i n e v a l u a t i n g t h e m e t h o d s were s e l e c t e d f r o m d i f f e r e n t t y p e s a v a i l a b l e on t h e mar!iet. I t was c o n s i d e r e d t h a t t h e o n e s s e l e c t e d would s u f f i c i e n t l y c o v e r t h e f i e l d of w a t e r p r o o f ' e r s t o i n d i c a t e t h e u s e f u l n e s s o f s u c h a s e r i e s o f t e s t s . The f o l l o w i n g were u s e d : In+,o,.rrni ' ? ! ~ t e : ~ r ? r o c f c r s

.

-

A d n i x t u r e 1 i s o f t h e a c c e l e r a t o r

--

---

---..-

-

-

t y p e . I t i s z _{l i g h t g r e y l i q u i d c o n t s i n i n - c a l c i u m c h l o r i d e} i n t h e c o n c e n t r a t i o n o f

345

grams p e r l i t r e a s i n d i c a t e d b y d e n s i t y measurement. T h i s a g e n t would p r e s u m a b l y a c c e l e r a t e t h e h a r d e n i n g o f t h e cement p a s t e , t h e r e b y h a s t e n i n g t h e f i l l i n g o f v o i d s i n t h o p a s t e and. p r o m o t i n g l o w e r p e r m e a b i l i t y a t e a r l y a c e s .

A d m i x t u r e 2 i s n w a t e r - r e p e l l e n t , s t e a r a t e t y p e . I t i s a creamy p a s t e c o n t a i n i n g 24 p o r c e n t amrnoni~un s t e a r a t e b y w e i c h t a c c o r d i n g t o t h e m a n u f ~ . c t u r e r t s d e s c r i p t i o n . P r e -

s u m a b l y t h e f r e e l i m e i n t h o hydrating cement woulcl combine w i t h t h i s a g e n t f o r m l n p I . n s o l u b l e c a l c i u m s t e a r a t e . T h i s c s l c i u m s o a p would r e n d o r t h e n o r e s u r f a c e s o f t h e p a s t e h y d r o p h o b i c and t h e r e b y d e c r e a s e a b s o r p t i o n . Admixture

3

i s a b i t u m i n o u s e r n u l s i o n d e s i g n a t e d as a n i n t e g r a l w a t e r p r o o f e r . T e s t s i n d i c a t e d a w a t e r c o n t e n t of 4 0 p e r c e n t by w e i ~ h t a n d a s o f t e n i r ~ n o i n t or' 0 2 O ~ . ( A . S. T. M. D95-46 and

114-6-46).

T h i s a g e n t would. p r e s u m a b l y c o a t i n t e r n a l s u r f a c e s or' t h e c o n c r e t e , r e n d e l - i n ? i t h y d r o - p h o b i c . Admixture

4

i s a l i f t h t y e l l o w p a s t e o f a s i l i c e o u s a n d o r e a n i c c o m p o s i t i o n , a n d a w a t e r c o n t e n t o r 8b p e r c e n t by w e i g h t . The s i l i c a i s p r o b a b l y i n t h e f o r m o f a g e l and i s p r e s u m a b l y i n t e n d e d t o cornbino wi.th t h e f r e e l i m e l i b c r a t e d t h r o u g h h y d r a t i o n . The r e s u l t i n p i n s o l u b l e s i l i c a t e s a r e p r o b a b l y e x p e c t e d t o pr>oduce a d e n s e , i m p e r m e a b l e p a s t e . The o r g a n i c component o f t h e a d m i x t u r e may b e i n t e n d e d a s a

w a t e r r e p e l l e n t .

S u r f a c e W a t e r p r o o f e r s .

-

No.

1s

i s a n e a t c e m e n t - p a s t e w i t h

a w a t e r - c e m e n t r a t i o o f 0.75. T h i s p r o d u c e d n v e r y f l u i d c o n s i s t e n c y w h i c h would. n o t b e u s e d i n p r a c t i c e . 'Phis w a t e r c o n t e n t was u s e d t o conlpare r e s u l t s w i t h No. 2 S w h i c h r e q u i r e s

a w a t e r - c e m e n t r a t i o of 0 . ' / 5 . One c o a t was a p p l i e d . P r o p e r c o r n ~ a r i s o n o f r a t i n g w i t h n e a t c e m e n t - p e , s t e would r e q u i r e a c r e a m y c o n s i s t e n c y a s recommended i n well-known p u b l i c a t i o n s . Two c o a t s a r e u s u a l l y a p p l i e d i n p r a c t i c e . No. 2S 5 s a p r o p r i e t a r y c e m e n t - b a s e s u r f a c e w a t e r p r o o f e ~ w h i c h i s mixed w i t h w a t e r ( w 2 t ~ r - c e m e n t r a t i o o f 0 . 7 5 ) . One c o a t i s a p p l i e d on a c l e a n and t h o r o u g h l y s a t u r a t e d s u r f a c e . No.

3 s

i s a s i l i c o n e r e s i n . I t i s m a r k e t e d a s a s o l u t i o n o f

5

p e r c e n t s i l i c o n e 2nd 9.5 n e r c e n t s o l v e n t . I t i s a p p l i e d o n a c l e a n d r y s u r f a c w i t h 2 b r u s h . The q u a n t i t y t o be u s e d i s 0 . 1 grorns/cE? o f s u r f a c o .

4..

I r e n a r a t i o n o f T e s t Sanlples _{---.-.-- . -.-} F o r I n t e g r a l S J a t e r g r o o f e ~ ~ s .

-

The a g g r e g a t e u s e d i n t h e s a m p l e s

-

was a n a t u r a l sand o f good s e r v i c e r e c o r d , and u s e d a s a r e f e r - e n c e m a t e r i a l i n t h i s l a b o r z t o r y . I t s s p e c i f i c g r a v i t y i n t h e s a t u r a t e d s u r f a c e d r y c o n d i t i o n was 2.60. I t w a s s e p a r a t e d i n t o s i e v e f r a c t i o n s and rcconlbined t o c o n f o r m t o t h e A.S.T.14. g r a d i n g r e q u i r e m e n t s , a s f o l l o w s :

s i e v e s i z e : p a n 1 0 0 5 0 3 0 1 6

8

4

p e r c e n t p a s s i n g : O

5

15

35

60 80 1 0 0 B e c a u s e of t h e s m a l l s i z e of' t h e t e s t s a m p l e s n o a g g r e g a t e was u s e d a b o v e t h e No. s i e v e s i z e . T h i s s h o u l d i n n o way

a f f e c t t h e method o f r a t i n g t h e a d m i x t u r e s .

Only one t y p i c a l C a n a d i a n cement was u s e d i n t h i s t e s t program. I t s s p e c i f i c g r a v i t y was 3.165 and o f a somewhat g r e a t e r f i n e n e s s t h a n t h a t of most C a n a d i a n p r o d u c t s . From t h e c h e m i c a l a n a l y s i s , t h e c a l c u l a t e d compound c o m p o s i t i o n was f o u n d t o b e : t r i c a l c i u m s i l i c a t e

48

p e r c e n t , d i c a l c i u m s i l i c a t e 2 5 p e r c e n t , and t r i c a l c i w n a l u m i n a t e

13

p e r c e n t , a n o r m a l Type 1 cement. Two m o r t a r c o m p o s i t i o n s w e r e s e l e c t e d : m o r t a r A b e i n g f a i r l y r i c h and w i t h a low w a t e r - c e m e n t r a t i o ; and m o r t a r B

a l e a n mix w i t h a h i g h w a t e r - c e m e n t r a t i o . The a c t u a l mix p r o p o r t i o n s used a r e shown i n T a b l e I.

MORTAR MIXUS FOR TEST SAPIPI,ES

-

M o r t a r A M o r t a r B A g g r e g a t e Cement r a t i o 6.17 ( b y w e i g h t ) 7 - 4 4 ( b y w e i g h t ) Water Cement r a t i o 0.62 ( b y w e i c h t ) 0.78 ( b y w e i g h t ) D e n s i t y o f t h e f r e s h c o n c r e t e 234.0 g r / l i t r e 11 2300 p / l i t r e Cement c o n t e n t 3 0 0

"

250 " 11 Sand c o n t e n t

1855

'I II 185;s

"

II W a t e r c o n t e n t 185;

"

1 I 1 9 5

"

I1 A i r v o i d s 1.6% ( b y volume) 2.2% ( b y volume)

Samples of t h e s e two c o m p o s i t i o n s w e r e made w i t h and w i t h o u t t h e a d m i x t u r e s r e f e r r e d t o p r e v i o u s l y . T h e s e admix- t u r e s w e r e i n c o r p o r a t e d a t t h e t i m e of m i x i n g i n t h e amount and manner s p e c i f i e d by t h e m a n u f a c t u r e r . F o r a d m i x t u r e 1, p a r t of t h e m i x i n g w a t e r w a s r e p l a c e d b y an e q u a l volume of

a d m i x t u r e s o t h a t t h e c a l c i u m c h l o r i d e a c t u a l l y a d d e d w a s

two p e r c e n t of t h e cement c o n t e n t by w e i g h t . Admixture 2 was added t o t h e t o t a l m i x i n g w a t e r i n t h e a ~ o u n t oS 0.7 p e r c e n t by w e i g h t of cament. F o r a d m i x t u r e

3,

p a r t o f t h e w a t e r was r e p l a c e d b y a n e q u a l volume of a d m i x t u r e c o r r e s p o n d i n g t o 1 7 p e r c e n t b y w e i g h t o f c e m e n t , and a d m i x t u r e

4

w a s added t o t h e t o t a l m i x i n g w a t e r i n t h e amount o f 6.8 p e r c e n t by w e i g h t of cement. A l l n r o p r i e t a r y m a t e r i a l s w e r e a d d e d a s s p e c i f i e d by t h e m a n u f a c t u r e r .

The m o r t a r s w e r e m e c h a n i c a l l y mixed and, f o r t h e

p e r m e a b i l i t y t e s t s , s a m p l e s w e r e moulded i n s m a l l c y l i n d r i c a l moulds

4

i n c h e s i n d i a m e t e r and 1 i n c h i n d e p t h . F o r t e n s i l e

and c o m p r e s s i v e s t r e n g t h s , s p e c i m e n s w e r e f a b r i c a t e d i n

c o n v e n t i o n a l moulds. S t a n a a r d b a r moulds were u s e d f'or s a m p l e s t o be s u b j e c t e d t o s h r i n k a g e t e s t i n g .

The samples f o r t h e p e r m e a b i l i t y t e s t s were compacted by v i b r a t i o n u n d e r c o n t r o l l e d c o n d i t i o n s t o o b t a i n uniform d e n s i t y of m a t e r i a l . Iquch p r e l i m i n a r y work was c a r r i e d o u t i n t h i s phase of t h e i n v e s t i g a t i o n t o e n s u r e a high d e g r e e

01' r e p r o d u c i b i l i t y . The samples f o r s u p p l e m e n t a r y t e s t s were p r e p a r e d a c c o r d i n g t o A.S. T.M. s p e c i f i c a t i o n s .

Except f o r t h e s h r i n k a g e samples, t h e specimens were c u r e d 24 h o u r s a t n e a r 100 p e r c e n t R.H., demoulded and

s t o r e d i n w a t e r f o r

6

d a y s 6 t h e n p l a c e d i n a room c o n d i t i o n e d a t

5'0

p e r c e n t R.H. and 2 3 C. f o r 28 days.

The code f o r t h e t e s t samples i s a s f o l l o w s : Code

-

AOX A 1 X A2X A 3 X BOX B I X B2X B3X

The f i r s t l e t t e r of t h e code r e f e r s t o t h e mix A o r B. The middle number r e f e r s t o t h e a d m i x t u r e , i f any. The X r e f e r s t o t h e cement used i n t h i s s t u d y . D u p l i c a t e samples were used from e a c h s e r i e s and f o r e a c h t e s t and t h e i r mean

v a l u e s a r e r e p o r t e d i n t h i s t e x t .

C e r t a i n p r o p e r t i e s of t h e cements and m o r t a r s , o t h e r t h a n p e r m e a b i l i t y , were e x p e c t e d t o be m o d i f i e d by t h e ad- m i x t u r e s . The p r a c t i c a l importance of s u c h e f f e c t s would depend on t h e p a r t i c u l a r f u n c t i o n of t h e c o n c r e t e element i n q u e s t i o n . I n t h i s i n v e s t i g a t i o n i t was n o t p o s s i b l e t o

c a r r y o u t a complete chock on t h e s e v a r i a b l e s , b u t s e v e r a l were done t o show t h e need f o r such t e s t s .

T a b l e I1 g i v e s t h e t i m e of s e t of t h e cement ( V i c a t n e e d l e ) , w i t h no admixture, and w i t h e a c h a d m i x t u r e p r e s e n t

i n t h e same p r o p o r t i o n t o t h e cement a s p r e s c r i b e d f o r t h e m o r t a r s .

The c a l c i u m c h l o r i d e admixture i s shown t o h a s t e n t h e s e t t i n & t i m e v e r y cons i d e r a b l y .

The w o r k a b i l i t y of t h e f r e s h m o r t a r was e s t i m a t e d by o b s e r v a t i o n and t h e t i m e o f v i b r a t i o n n e c e s s a r y f o r complete compaction was noted. The r e s u l t s a r e g i v e n i n T a b l e I11

TABLE I1

-

TIME OF SET OF STANDARD CEMENT PASW WITH AND lJITROUT ADMIXTURES

S e r i e s I n i t i a l S e t F i n a l S e t Mix

-

AOX A 1 X A2X

A3X

A ~ x 2 h r .

55

m i n e

3

h r .

45'

m3-n. 0 h r .

55

mine 1 h r . 1 0 min.

3

h r . 1 0 mine

4

h r . 08 mine

3

h r . 40 mine

4

h r .

45

mine

3

h r . 8 0 min.

3

h r . 50 min. TABLE I11

WORKABILITIES OF MORTAR IQX A

-

W o r k a b i l i t y F a i r F a i r Good Poor F a i r Length o f V i b r a t i o n

-

50

-

60 s e c .

50

-

6 0 s e c . 25

-

40 s e c . 50

-

115

s e c .

50

-

60 S ~ C . M o r t a ~ B gave s i m i l a r r e s u l t s b u t r e q u i r e d s l i g h t l y l o n g e r vibration p e r i o d s f o r complete compaction.

The 28-day c o m p r e s s i v e and t e n s i l e s t r e n g t h s of m o r t a r

A w i t h and w i t h o u t a d m i x t u r e s a r e g i v e n i n T a b l e I V .

TABLE I V

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28-DAY COMPHESSIVE AND TENSILE STRENGTHS

S e r i e s

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AOX A 1 X A2X A3X A 0 Cornpre s s i ve T e n s i l e S t r e n g t h s ( p s i 2 3 1 S i m i l a r t e s t s on m o r t a r B a r e n o t shown s i n c e t h e y showed t h e e x p e c t e d l o w e r s t r e n g t h s and were i n t h e same

o r d e r ss f o r m o r t a r A.

I t was noted t h a t , a l t h o u p h the c a l c i u m c h l o r i d e i n t e g r a l admixture a c c e l e r a t e d t h e s e t t i n g time, i t d i d n o t i n c r e a s e r a t e of h a r d e n i n g a s i n d i c a t e d by t h e s t r e n ~ t h s i n Table I V . The t e s t s were r e p e a t e d w i t h pure c a l c i u m c h l o r i d e , w i t h t h e same r e s u l t s . They l..!ero t h e n r e ~ e a t e d a t h i r d t i m e w i t h t h e sam2les c u r e d a t n e a r 100 p e r c e n t R.B. i n s t e a d of i n w a t e r . Again . t h e r e s u l t s were t h e salne, i n d i c a t i n g t h a t t h i s cement was n o t r e s p o n s i v e t o c a l c i u m chlo!-ide, The s t e a r a t e a d m i x t u r e a p p e a r e d t o have no a d v e r s e i n f l u e n c e on s t r e n g t h s , whereas t h e b i t u m i n o u s m a t e r i a l d i d r e d u c e s t r e n g t h s c o n s i d e r a b l y . The s h r i n k a g e d a t a g i v e n i n Table V i n d i c a t e p o s s i b l e a d v e r s e i n f l u e n c e on t h e p a r t of some i n t e g r a l a d m i x t u r e s on t h e volume change c h a r a c t e r i s t i c s of c o n c r e t e . T h i s i s p a r t i c u l a r l y n o t i c e a b l e i n t h e c a s e of' i n t e p a l adtnlxture No.

4.

F i g u r e 1 shotrs c u t c r o s s - s e c t i o n s t h r o u ~ h samples of' m o r t a r s A and

R.

M o r t a r I3 i s n o t a b l e f o r t h e h i z h p e r c e n t a g e of l a r g e v o i d s . Theso two m o r t a r s were c o n s i d e r e d 2s s u L t - a b l e f o r t e s t i n ? t h e Lnfluence 01' i n t e g r a l w a t e r p r o o f o r v on

p e r m e a b i l i t y . These t e s t s i l l u s t r a t e t h e need f o r c a r e f u l c o n s i d e r a t i o n of p o s s i b l e m o d i f i c a t i o n s i n p r o p e r t i e s t o b e e x p e c t e d from t h e a d d i t i o n o f i n t e , p r a l w a t e r p r o o f e r s . The e f f e c t s of t h e s e a d m i x t u r e s w i l l v a r y w i t h t h e cement and t h i s must be t a k e n i n t o a c c o u n t b e f o r e t e s t i n g . For example, t h e i r i n f l u e n c e on s h r i n k a g e , though s m a l l , may b o an impor- t a n t f a c t o r f o r c e r t a i n t y p e s of s t r u c t u r e s . The number of such check t e s t s may, however, be c o n f l n e d t o t h o s e p r o p e r t i e s t h a t a r e of' c o n c e r n on a g i v e n job. I n p a r t i c u l a r , s u i t h l e d u r a b i l i t y t e s t s must be developed t o p a r a l l e l p e r m e a b i l i t y t e s t s . S i n c e t h e p r e s e n t s t u d y was d i r e c t e d toward t h e development o f methods f o r r a t i n g a d m i x t u r e s on t h e b a s l s of t h e i r i n f l u e n c e on p e r m e a b i l i t y a l o n e , s u c h a d d i t i o n a l v a r i a b l e s r e q u i r e f u r t h e r r e s e a r c h , S u r f a c e Waterproof e r s .

--

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A l l s u r f a c e w a t e r p r o o f ' e r s a r e i n t e n d e d t o be p a i n t e d on s u r f a c e s w i t h smooth t e x t u r e s and w i t h o u t l a r g e p o r e s . I t was c o n s i d e r e d t h a t m o r t a r A f o r i n t e g r a l w a t e r p r o o f e r s would meet t h e s e r e q u i r e m e n t s and t h e r e f o r e i t was used. The s i z e and shape o f s a m p l s s were t h e same a s f o r t h e p e r m e a b i l i t y t e s t s c m p l e s f o r i n t e g r a l w a t e r p r o o f e r s .

P r e p a r a t i o n an2 c u r i n g were a l s o t h e same. The s u r f a c e w a t e r - p r o o f e r s were a p p l l e d when t h e samples were

28

d a y s o l d .

A f t e r a p p l i c a t i o n , t h e samples were c u r ~ d a n a d d i t i o n a l

14

d a y s a t

50

p e r c e n t R.H. b e f o r e t h e t e s t s were s t a r t e d . The f o u r s e r i e s c o n s i s t e d o f : No. OS w i t h no c o a t i n g , No.

1s w i t h

one c o a t o f n e a t cement-paste, No. 2 5 w i t h one c o a t of cement- b a s e w a t e r p r o o f e r , and No.

3s

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

I Oi3O'O-$LO'O ZLG'G-990'0 850'0-050'0 ~f0'0-zCG'O ZTO'G-010'0 80GeO-ZOG'O Xftr

A , I n t e y r a l W a t e r p r o o f e r s

-

1, Vapour P e r m e a b i l i t y T e s t G e n e r a l .

-

A s p e c i a l c a s e o f m o i s t u r e f l o w i s v a p o u r d i f f u s i o n , Here b o t h s u r f a c e s of t h e m a t e r i a l r e m a i n d r y and w a t e r v o p o u r d i f f u s e s t h r o u s h t h e v o i d s o f t h e c o n c r e t e due t o d i f f e r e n c e s i n v a p o u r p r e s s u r e s , A l t h o u g h t h e r e h a s b e e n c o n s i d e r a b l e i n v e s t i s a t i o n i n t h e f i e l d of v a p o u r p e r m e a b i l i t y , t h e r e a r e a s p e c t s w h i c h a r e s t i l l n o t c l e a r l y u n d e r s t o o d , I t i s p r o b a b l e t h a t t h e f l o w t a k e s p l a c e a s v a p o u r d i f f u s i o n t h r o u g h t h e l a r g e r p o r e s and as a s e q u e n c e of c o n d e n s a t i o n , c a p i l l a r y f l o w , and e v a p o r a t i o n t h r o u z h t h e s m a l l e r c a p i l l a r i e s , The most c o m p l e t e t h e o r y on t h i s phenomonon h a s b e e n e s t a b l i s h e d

by 0. Krischer

(54).

With t h i s t h e o r y and by means o f a s e r i e s o f c o m p l i c a t e d e x p e r i m e n t s , K r i s c h e r was a b l e t o d e t - e r m i n e s e p a r a t e l y t h e f a c t o r s f o r t h e two t y p e s of' p a r t i a l f l o w i n a sample o f wood, But due t o e x p e r i m e n t a l d i f f i c u l t y , t h i s method i s n o t a p p l i c a b l e t o o t h e r m a t e r i a l s . A t p r e s e n t t h e g e n e r a l l y a c c e p t e d method, t h e r e f o r e , c o n s i s t s o f u s i n g r e l a t i o n s s i m i l a r t o t h o s e i n h e a t f l o w and o f d e t e r m i n i n g e x p e r i m e n t a l l y a n o v e r - a l l c o e f f i c i e n t of m o i s t u r e t r a n s - m i s s i o n K f r o m e a s i l y a s c e r t a i n a b l e s t e a d y s t a t e c o n d i t i o n s . The law o f m o i s t u r e t r a n s f e r c a n be w r i t t e n a s : q d x = Kdp where q = r a t e o f m o i s t u r e l'low p e r u n i t a r e a , gm/cm2 x s a c . x = d i s t a n c e f r o m s u r f a c e , cm, K = c o e f f i c i e n t of v a p o u r p e r m e a b i l i t y , cm/sec. p = v a p o u r p r e s s u r e a t p o i n t x , gm/cm2 Here d i f f i c u l t y a r i s e s f r o m t h e f a c t t h a t

K

i s n o t a c o n s t a n t a s i n h y d r o s t a t i c f l o w , b u t v a r i e s w i t h t h e v a p o u r p r e s s u r e p f r o m p o i n t t o p o i n t , T h e r e f o r e t h e above e q u a t i o n c a n n o t b e i n t e g r a t e d f u l l y , F o r t h e s t e a d y - s t a t e f l o w where q e q u a l s a c o n s t a n t , we have: To go f u r t h e r i t i s c u s t o m a r y t o work w i t h mean v a l u e s of t h e c o e f f i c i e n t :

Rut t h e mean v a l u e KO i s d e p e n d e n t on t h e i n t e r v a l ( p - p ) . I t s v a l u e may v a r y w i t h t h e p o s i t i o n and s i z e o f t h e i n ? e r v a l . Comparison or' r e s u l t s o f i n d e p e n d e n t e x p e r i m e n t s i s t h e r e f o r e n o t p o s s i b l e . The u s u a l p r o c e d u r e f o r m e a s u r i n g v a p o u r p e r m e a b i l i t y i s t h e d r y - c u p t e s t

( 5 5 ) .

I t wag a d o p t e d w i t h s u l t a b l e m o d i f i c a t i o n s t o accommodate t h e r e l a t i v e l y t h i c k sarnples. The s a m p l e s were mounted on aluminum d i s h e s f i l l e d w i t h a d e s i c c a n t (CaC12) a n d t h e s i d e s s e a l e d w i t h wax (Fig.2). One p a i r of t h e s e s o c a l l e d d r y c u p s was s t o r e d i n chambers w i t h c o n t r o l l e d c o n s t a n t t e m p e r a t u r e and c o n s t a n t h u m i d i t y . Owing t o t h e d i f f e r e n c e o f v a p o u r p r e s s u r e s o u t s i d e t h e c u p ( p ) and i n s i d e t h e c u p ( p o = o ) , v a p o u r d i f f u s e d t h r o u g h t h e p o r e s o f t h e mounted sample and was t a k e n up b y t h e d e s i c c a n t . To d e t e r m i n e t h e m o i s t u r e g a i n o f t h e d e s i c c a n t , w e i s h t s were t a k e n a t i n t e r v a l s and p l o t t e d a ~ a i n s t t i m e . The p l o t showed a l i n e a r g a i n w i t h t i m e ( F i g . 3a). A t t h i s s t e a d y - s t a t e c o n d i t i o n t h e s l o p e of t h e r e s u l t i n g s t r a i g h t l i n e r e p r e s e n t e d t h e r a t e o f v a p o u r f l o w q , f r o m which t h e mean v a l u e KO w a s c a l c u l a t e d : I t may b e n o t e d t h a t b y s t , o r i n g s e v e r a l p a i r s o f d r y c u p s i n d i f f e r e n t h u m i d i t y c o n d i t i o n s , c o r r e s p o n d i n g v a l u e s o f KO c a n b e d e t e r m i n e d . The G r a p h i c a l Method.

-

A s p o i n t e d o u t , KO i s a n a v e r a g e

-

_{c o e f f i c i e n t f o r t h e v a p o u r p r e s s u r e c o n d i t i o n s o f t h e t e s t} t h a t d o e s n o t r e v e a l d i r e c t l y t h e v a r i a t i o n of K w i t h v a p o u r p r e s s u r e ( o r , a t c o n s t a n t t e m p e r a t u r e , w i t h r e l a t i v e h u m i d i t y ) . .4s i t was p o s s i b l e t o o b t a i n v a l u e s o f q f o r g i v e n v a l u e s o f p e x p e r i m e n t a l l y by t h e dl-y-cup t e s t , t h o p r o d u c t s o f q a n d t h e t h i c k n e s s x, w e r e p l o t t e d a g a i n s t p, and c o n n e c t e d b y a smooth c u r v e , t o g i v e t h e

J0Pmp

c u r v e . G r a p h i c a l d i f f e r e n t i a t i o n o f t h i s c u r v e y i e l d e d

K v a l u e s :

F i e u r e 3b shows t h e g r a p h i c a l d i f f e r e n t l a t i o n method a p p l i e d t o t h e r e s u l t s o f dry-cup t e s t s c a r r i e d o u t a t 50 p e r c e n t , 80 p e r c e n t and 1 0 0 p e r c e n t r e l a t i v e humidity o u t s i d e t h e cups ( 5 6 ) . I t c a n be seen t h a t t h e c o e f f i c i e n t o f vapour p e r m e a b i l i t y of a m o r t a r remains f a i r l y c o n s t a n t f o r low h u m i d i t i e s . I n t h i s r e g i o n vapour d i f f u s e s t h r o u g h t h e p o r e s p r o b a b l y w i t h o u t c a p i l l a r y f'low. But once t h e r e l z t i v e

h u m i d i t y e x c e e d s a b o u t 60 t o 7 0 p e r c e n t , c a p i l l a r y movement c a n talce p l a c e , r e s u l t i n g i n marked i n c r e a s e s i n t h e co- e f f i c i e n t K w i t h i n c r e a s i n g r e l a t i v e h u m i d i t y .

I n f l u - e n c e of Admixtures.

--

-

To d e t e r m i n e t h e i n i ' l u e n c e of a d m i x t u r e s on t h e vapour p e r m e a b i l i t y of c o n c r e t e , d u p l i c a t e samples from s e r i e s AOX, A l X , AZX, A3X, A ~ x , and BOX, R l X ,

BZX, B3X, B u were t e s t e d by t b dry-cup t e s t f o r r e l a t i v e h u m i d i t i e s of 50,

80 and

100 p e r c e n t . F i g u r e s

4

and

5

show t h e c o e f f i c i e n t s of vapour p e r m e a b i l i t i e s o b t a i n e d by t h e g r a p h i c a l d i f f e r e n t i a t i o n method from t h e r e s u l t s o f t h e s e t e s t s . A s s e e n from t h e s e f i g u r e s , a d m i x t u r e s 1 and

4

a r e n o t e f f e c t i v e i n r e d u c i n g vapour p e r m o a b i l i t y . Admixture 2 a p p e a r e d t o be e f f e c t i v e o n l y f o r mix

B, and a d m i x t u r e

3

was e f f e c t i v e i n a l l c a s e s .

2. S a t u r a t e d P e r m e a b i l i t y T e s t

A g r e a t nmber of i n v e s t i g a t i o n s have a l r e a d y been done i n t h e f i e l d of c o n c r e t e p e r m e a b i l i t y . T h n i r r e s u l t 8 have y i e l d e d much i n f o r m a t i o n on t h e c h a r a c t e r i s t i c s o f t h i s t y p e of w a t e r flow and on t h e e f f e c t s of d i f f e r e n t f a c t o r s s u c h a s cement q u a l i t y and f i n e n e s s , a g g r e g a t e q u a l i t y and g r a d i n g , mix p r o p o r t i o n s , c o n s i s t e n c y , water-cemont r a t i o , s u r f a c e f i n i s h , and c u r i n g c o n d i t i o n s . A s u m ~ a r y of t h e s e r e s u l t s h a s been r e p o r t e d i n a p r e v i o u s p a p e r

( b O ) .

The d i s c u s s i o n s h e r e w i l l be c o n f i n e d o n l y t o son~e a s p e c t s o f h y d r o s t a t i c p e r m e a b i l i t y : t o t h e s o - c a l l e d "impermeable concretes" which under o r d i n a r y c o n d i t i o n s show no v i s i b l e l i q u i d f l o w , and t o t h e i n f l u e n c e of' w a t e r p r o o f i n g a d m i x t u r e s . P e r m e a b i l i a .

-

P e r m e a b i l i t y i n v e s t i g a t i o n s show t h a t , a f t e r a s u f f i c i e n t d u r a t i o n of t e s t , w a t e r movement t h r o u g h con- c r e t e p o r e s ma.y be e x p r e s s e d by D a r c y l s f o r m u l a : where w i t h q = r a t e o f f l m , p n / s e c . F = a r e a , cn12 p = p r e s s u r e , &m/cm* x = t h i c k n e s s , cm. K = c o e f f i c i e n t of p e r m e a b i l i t y , cm/sec.

D a r c y t s f o r m u l a shows t h a t t h e e f f e c t of c o n c r e t e q u a l i t y - o n p e r m e a b i l i t y i s r e p r e s e n t e d by t h e p e r m e a b i l i t y c o e f f i c i e n t . Thus K i s t h e o n l y p r a c t i c a l mcans of ex- p r e s s i n g t h i s p r o p e r t y o r c o n c r e t e by a numerical v a l u e and o f comparinc d i f f e r e n t c o n c r e t e s . Values o f K have been found t o v a r y from

l o m 6

t o 10-10 cm/sec. f o r c o n c r e t e s of v a r y i n g q u a l i t i e s and v a r y i n g a g e s above t h e age of 7 days.

I n an a t t e m p t a t f u r t h e r e x p l a n a t i o n of t h e p e r m e a b i l i t y c o e f f i c i e n t Powers and Brownyard e s t a b l i s h e d t h e f o l l o w i n g

t h e o r e t i c a l e q u a t i o n f o r p u r e cement p a s t e s ( 3 7 ) : K = 2.26 x 1 0 - l ~

(

' - c v C ) ( ~ - ~ ~ ) cm/sec. w i t h c = cement c o n t o n t , gm/cm3 V, = s p e c i f i c volume of c a ~ u e n t , crn3/g1n. K1= t h i c k n e s s of t h e i n m o b i l e s u r f a c e l a y e r i n t e r m s 01' m o l e c u l a r l a y e r s .

According t o Powers and Brownyard t h e o r e t i c a l I m p e r m e a b i l i t y ( K = 0 ) can be o b t a i n e d i f :

( a ) c * V C = 1. That i s , i f t h e p a s t e i s a v o i d . l e s s mass, which i s i m p o s s i b l e b e c a u s e even f o r t h e d e n s e s t p a s t e s c.V, was found t o be n o t l a r g e r t h a n 0.70.

( b ) K 1 =

4.

The minimum v a l u e f o r K1 i s 1. The maximum v a l u e i s n o t known, b u t l t c a n n o t be a c c e p t e d a s l a r g e a s

4,

which would mean t h a t a l l t h e w a t e r i n t h e p o r e s i s immobile.

Thus K1 i s p r o b a b l y 1 and n o t

4.

A s a r e s u l t of t h e s e c o n s i d e r a t i o n s Powors and Brown- y a r d conclude t h a t cement p a s t e s c a n n e v e r be impermeable.

F u r t h e r p e r m e a b i l i t y e x p e r i m e n t s by Powers, Copeland and Hayes on cement p a s t e s confirmed t h i s c o n c l u s i o n and showed t h a t even t h e d e n s e s t p o s s i b l e cement p a s t e s (w/c = 0.2) gave some s m a l l l e a k a g e

( 3 9 ) .

I t f o l l o w s t h a t m o r t a r s and c o n c r e t e s c a n n o t be impermeable i f t h e cement p a s t e i s permeable. With p r o p e r p r o p o r t i o n i n g t h e i r p e r r n o a b i l i t y may b e v e r y s m a l l b u t some movement w i l l always occur.

E x p e r i m e n t a l r e s u l t s show t h a t i f t h e c o n d i t i o n s

p r o d u c i n g f l o w a r e m a i n t a i n e d o v e r a s u b s t a n t i a l p e r i o d t h e r e I s a s m a l l b u t c o n t i n u o u s d e c r e a s e i n t h e p e r m e a b i l i t y of c o n c r e t e . E x p l a n a t i o n s have been g i v e n t o a c c o u n t f o r t h i s phenomenon a s f o l l o w s :

( a ) Expansion o f cement p a r t i c l e s due t o f u r t h e r h y d r a t i o n ;

( b ) S w e l l i n g of t h e cement and a g g r e g a t e c o l l o i d s due t o w e t t i n s ;

( , c ) C l o g s i n g o f t h e p o r e s b y p r o d u c t s of c h e m i c a l c o m b i n a t i o n o f b i c a r b o n a t e s i n w a t e r w i t h t h e f r e e l i m o of cement;

( d ) R e t a r d a t i o n o f f l o w due t o t h e i n c r ~ a s e i n t h i c k n e s s of t h e irnmobile w a l l l a y e r ;

( e ) R e t a r d a t i o n o f flord due t o t h e establishment o f

a c o i r n t e r a c t i n p e l e c t r i c a l ~ o t e n t i a l .

The t r u e ~ i c t u r e o f t h i s phenomenon i s y o t n o t known.

I t seorns r e a s o n a b l e t h a t s e v e r a l 01' t h e s e f a c t o r s may b o

r e s p o n s i b l e

.

I n t h e p e r m e a b i l i t y e x p e r i m e n t s now t o be r e p o r t e d

one s a m p l e mix BOX, 28 d a y s o l d , was t h e n m a i n t a i n e d u n d e r t e s t f o r 20 d a y s . A s may be s e e n f r o m F i g . h i t s p e r m e a b i l i t y

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

7

d a y s o f t e s t , f o l l o w i n g c u r v e ab. A t t h e end of

7

d a y s i t was n e c e s s a r y t o make some a d j u s t m e n t s i n t h e a p p a r a t u s , s o t h e s a a p l e was t a k e n o u t f o r a few h o u r s and t h e n mounted a g a i n and t h e t e s t c o n t i n u o d . The p e r m e a b i l i t y s t a r t e d w i t h h i ~ h e s v a l u e s a t c , f e l l q u i c k l y t o t h e o l d v a l u e a t d , and c o n t i n u o d t o d e c r e a s e a t a low r a t e u n t i l t h e v a l u e a t e _{was r e a c h e d a t t h e end o r}

28

_{d a y s ,}

The samp19 was t h e n t a k e n o u t o f t h e a p p a r a t u s , d r i e d i n a d e s i c c a t o r f o r one week, mounted a g a i n i n t h e d r y c o n d i t i o n and r e t e s t e d , The now p e r m e a b i l i t y s t a r t o d w i t h a h i , s h e r v a l u e a t f , b u t f o l l o w i n g f g i t f e l l i n a s h o r t t i m e t o a l o w e r v a l u e , and f r o m t h e n on c o n t i n u e d t o d e c r e a s e a l o n g gh a t a s i m i l a r r a t e a s a l o n g de. Tho p a r t s c d and f g of t h e s e c u r v e s i n d i c a t e t h e e x i s t e n c e of a r e v e r s i b l e d e c r s a s e i n p e r m e a b i l i t y and t h e p o s i t i o n o f t h e c c x v e f g h i n r e s p e c t t o abcde i n d i c a t e s t h e e x i s t e n c e of a permanent d o c r o a s o . R e f e r r i n g t o t h e p o s s i b l e e x p l a n a t i o n s l i s t e d a b o c e , t h e pormnnont d e c r e a s e might be e x p l a i n e d b y f a c t o r s 1 a n d

3

and t h e r e v e r s i b l e d e c r s a s e b y

2,

4,

and

5 .

No f u r t h e r investigation was made o f t h i s c h a r a c - t e r i s t i c ,

For p r a c t i c a l Durposes i t seemed l o g i c a l t o a c c e p t

p o i n t b, r e p r e s e n t i n g t h o p e r m e a b i l i t y a t t h e end of

7

da;ys o f t e s t , a s a b a s i s of c o n p a s i s o n , b e c a u s e i t was of t h e same o r d e r as t h e f i n a l v a l u e e o r a s t h e v a l u e h i n t h e s e c o n d t e s t , and i t r e q u i r e d o n l y one week o f t e s t i n g . Impermeable C o n c r e t e s .

-

I n most i n v e s t i g a t i o n s c a r r i e d o u t by

-

o t h e r s p e r m e a b i l i t y t e s t s have been made t o d e t e r m i n e t h e

minimum cement c o n t e n t n e c e s s a r y t o o b t a i n impermeable c o n c r e t e . L i t t l e r e s e a r c h h a s been done on c o n c r e t e o f h i g h o r cement con- t e n t s . O f i n t e r e s t i s t h e r e c e n t p u b l i c a t i o n by pow em,^.

Copeland a n d Rages on t h e p e r ~ n e a b i l l t y of p o r t l a n d cement p a s t e s ( 3 9 ) a l r e a d y r e f e r r e d t o .