Determination of the Specific Surface Area of Cements and Pozzolans by the Blaine Air-Permeability Method

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Determination of the Specific Surface Area of Cements and Pozzolans by the Blaine Air-Permeability Method

D G T E F M I N A T I C N O F IhT S Y J C I F I C S U E Z A C E AHEA O F

CEMENTS AND POZZOLANS BY THE BLAINE AIR-

P E R P l E A B I L I T Y METHOD

by

E.G,

Swenson and 11-C. Evans

N O T FOR F U B L I C A T I O N

Research. Report, No. 31

of the

D e t e r m i n a t i o n of tihe S p e c i f i c S u r f a c e Area o f Celnents and P o z a o l a n s by t h e B l a i n e A i r -

p e r m e a b i l i t y

-

Method

by E,G. Swenson and H.C. E v s n s

Purpose of T h i s I n v e s t i a a t i o n

-

The o b j e c t of t h i s i n v e s t i g a t i o n was t o s e t up t h e n e c e s s a r y a p p a r a t u s t o d e t e r m i n e t h e s p e c i f i c s u r f a c e a r e a

(S.S.A.) of t h e cements, p o z z o l a n s , and o t h e r m a t e r i a l s b e i n g used i n p r o j e c t s of t h e B u i l d i n g M a t e r i a l s S e c t i o n , 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 .

The knowledge of t h e p r o p e r t i e s of s u c h m a t e r i a l s i s e s s e n t i a l p a r t i c u l a r l y i n t h e c a s e of cements s i n c e Canadian cements a r e c o n s i d e r a b l y c o a r s e r t h a n U,S. cements. F i n e n e s s i n f ' l u e n c e s t h e r a t e of h y d r a t i o n and may a l s o have an i m p o r t a n t b e a r i n g on t h e chemical r e a c t i v i t y o f a cement w i t h c e r t a i n s o - c a l l e d " d e l e t e r i o u s n a g g r e g a t e s . I n a d d i t i o n , D i v i s i o n a l s t u d i e s i n ~ o l v i n g t h e use o f p o z z o l a n i c m a t e r i a l s s u c h a s f l y a s h and n a t u r a l v o l c a n i c a s h e s i n c o n c r e t e r e q u i r e a knowledge of t h e f i n e n e s s of t h e s e m a t e r i a l s , N a t u r a l p o z z o l a n s a r e economical t o use o n l y i f p r o c e s s i n g i s i n e x p e n s i v e . F o r example, i f e x c e s s i v e g r i n d i n g i s r e a u i r e d t o b r i n g o u t t h e n e c e s s a r y p o z z o l a n i c a c t i v i t y , t h e m a t e r i a l i s n o t o f economic v a l u e . S e v e r a l methods a r e a v a i l a b l e f o r d e t e r m i n i n g s p e c i f i c s u r f a c e a r e a s of s u c h m a t e r i a l s . The B l a i n e method was c h o s e n b e c a u s e of i t s s i v p l i c i t y and a l s o b e c a u s e i t i s one of t h e a c c e p t e d methods of t h e A.S.T.M. f o r f i n e n e s s d e t e r m i n a t i o n o f cements.

Methods of D e t e r m i n i n g t h e S p e c i f i c S u r f a c e Area

T h e r e a r e t h r e e methods commonly i n u s e a t t h e p r e s e n t time t o d e t e r m i n e +,he S.S.A. They a r e "The B l a i n e A i r - p e r m e a b i l i t y Method", "The Lea and. Nurse A i r P e r m e a b i l i t y ~ e t h o d " , and "The

Wagner T u r b i d i t y Meter", A b r i e f d e s c r i p t i o n of t h e l a t t e r two w i l l be g i v e n h e r e . The main body of t h e r e p o r t d e a l s w i t h t h e B l a i n e method.

Lea 3nd !\Jurse A i r P 6 r a e a b l l i t y Mothod (1)

--

---. --

The a i r i s p ~ s s e d t h r o u g h t h o compacted bed o f m a - i t e r i n l n t n c o n s t a n t r n t e and t h e p r e s s u r e d r o p a c r o s s i t

i s measured by an o i l - m a n o m e t e r . Tho rcrte of f l o w i s mnsllred u s i n g n flownleter. The s p e c i f i c s u r f a c e is c a l o n l . n t e d from

t h e e q u a t i o n : i -where S _{i s t h e s p e c l . f i c s u r f ~ i c e a r e a i n ~ r n 2 / ~} t h e d e n s i t y tho m a t e r i a l bed i n e i s t h e p o r o s i t y of t h c m q t e r i a l . A i s t h t c r o s s - s e c t l o n a l n r c a o f b e d i n cm2. hl i s t h e p r e s s u r e a c r o s s bed. 112 i s t h o p r s s s u r t ; z c r o s s f l o w m e t e r . C i s a c o n s t a n t f o r tho c a p i l l a r y t u b e of t h e flowmete- L i s t h e l e n g t h of bed of powder (cm.)

A co.np2rison of t h o Lc3 nnd Nurse and t h e B l a i n e a i r p e m e n b i - l i t y methods i s g i v e n i n t h e p a p e r S p e c i f ' i c ~ t i o n T e s t s f o r S p t c i f i c S u r f a c e of Cements ( 2 ) .

Wagnor T u r b i d i t g Meter

-

A l i g h t s o u r c e of c o n s t n n t i n t e n s i t y p r o v i d e s p a r s l l e l r a y s t h r ~ t s h i n e t h r o u g h n s u s p e n s F o n of cement i n kcrosc-ne and

s t r i k e thEi s t n s i t i v e ? l u t e of a p h o t o e l e c t r i c c e l l . The c u r r e n t produced by t h e c e l l i s TG q s u r c d on R micro-anmeter. R e a d i n g s 3 r e t a k e n a t v a r i o u s l b v o l s i n t h e trlnk of k e r o s e n e a t t i m e s i n d i c 2 t i d by t h e f l o w of k e r o s e n e f r o m a s p e c i a l l y c s l i b r a t e d b u r e t t e . The r s q d i n g s n r e r o l ~ . t a d t o t h e amount of m a t e r i ~ l suspended i n t h e k e r o s e n e which i n t u r n i s 9 f u n c t i o n of t h e

f i n e n e s s of t h e cernt:nt. The p r o c e d u r e and c , ? l c u l n t i o n s f o r t h e t e s t w e e x p l a i n e d i n t h e A.S.T.M. S t ~ n d - r d s l c ~ 4 9 . B l a i n e A i r - p e r m e n b i l i t y Plethod _..-- T h i s .n.e t h o d c o n s i s t s of d r a w i n g a g i v e n volumt o f a i r t h r o u g h 3 c o m p ~ c t a d bcd o f powder of known p o r o s i t y i n a d e t e r ~ i n e d p e r i o d of t i m e . The p r e s s u r s r e q u i r e d t o draw t h o -. a i r t h r o u g h t h e bed of powder i s p r o v i d e d b y t h e l i q u i d i n t h e

~ r l n o ~ e t u r . The time f o r t h e l i q u i d l o v e 1 t o f s l l a marked d l . s t m c e i n t h e t u b e i s r e c o r d e d d o n g w i t h t h e t e r p e r a t u r e of t h e a i r .

Theory:. I n t h e t h e o r y on w h i c h t h i s m e t h o d i s b a s e d i t i s c o n s i d e r e d t h a t t h e c o m p a c t e d b e d of powder a p p r o x i m a t e s a l a r g e number o f c a p i l l ~ r y c h a n n e l s t o w h i e h P o i s e u i l l e ' s

Law

may be

a p p l i e d . T h i s L q w i s g i v e n b y t h e e q u ~ t i o n :

I n t h e d e v e l o p m e n t of t h i s t h e o r y t h e m a n h y d r a u l i c r a d i u s i s u s e d t o e x t e n d . t h e t h e o r y of c h a n n e l s of c i r c u l a r c r o s s - s e c t i o n t o t h o s e o f o t h e r s h a p e s . The e q u a t i o n s a r e d e v e l o p t i d i n a p a p e r by L e n and n'ursc ( 1 ) . The e q u a t i o n t h a t t h e y d e v e l o p is: If

A

P lic

L

a r e l x l d c o n s t a n t t h o s q u a t i o n becomes: e

=

p o r o s i t y 1

--

l e n g t h of c h a n n e l ( C m . ) L

-

l e n g t h of b e d of powder (cm. ) n

-

v i s c o s i t y of e 4 r i n p o i s e s P

-

p r e s s u r o d i f f o r e n c ~ i n dynes/cm 2 Q

-

d i s c h a r g e of clicmnel i n c c . R

-

r e d i u s o f c h a n n e l i n cm. S

-

s p e c i f i c s u r f z c e a r e n i n c a s / g T

-

t i a e f o r t h e r e q u i z o d volulne o f a i r t o f l o w t h r o u g h t h e b e d i n s e c . u

-

s p p a r e n t v e l o c i t y o f a i r ( i . e . v e l o c i t y o f a i r o v e r c r o s s - s e c t i o n of c e l l t h a t w i l l g i v e t h e same volume r n t e o f f l o w a s the a c t u a l v e l o c i t y t h r o u g h t h e b e d ) . P

-

t r u e d e n s i t y o f powder i n p e r m e a b i l i t y c e l l ( g / c c . )

A p p a r a t u s

The a p p a r a t u s i s i l l u s t r n t e d m d d e s c r i b e d i n A.S.T.M. S t a n d a r d s 1 9 1 ~ 9 .

P r o c e d u r e

The A.S.T.M. p r o c e d u r e wns f o l l o w o d f o r s t a n d a r d i z i n g t h e n p p a r n t u s and d e t c r ~ i n i n g t h e S p o c i f i c S u r f a c e Araa (S.S.A. )

f o r t h e p o r t l n n d cemt.nt t s s t c d . To f i n d t h e S.S.A. o f m n t c r i ~ l s 0 t h ~ ~ ) t h 8 n p o r t l a n d c e m e n t t h e t r u a d e n s i t y i n g / c c . of t h e powder nnd t h e w e i g h t of powder u s e d ~ ~ 1 s t b e d e t e r m i n e d . The l a t t e r d e t e r v i n a t i o n f o l l o w e d A.S.T.M. : p r o c e d u r e . The s p s c i f i c g r a v i t i e s o f t h e p o z z o l a n s w e r e d e t e r m i n e d u s i n g p y c n o m u t e r b o t t l e s a n d k e r o s e n e ,

The volumes of t h e p y c n o m e t b r s were f o u n d b y w e i g h i n g t h e volume of i3g c o n t a i n e d i n t h e p y c n o m e t e r ~ n d d i v i d i n g t h f s b y thu d e n s i t y o f Hg a t t h o tcmpt;r.citure of t h e m e a s u r e m e n t . The

iir;.ilsity of tht: k o r o s u n e u s e d was o b t a i n e d o v e r ? r a n g e o f t e m p e r a -

t u r e f r o m 1 8 O C . t o

3 5 O C .

The d e t e r a i n r ^ t i o n s wore made u s i n g t h e p y c l l o m e t e r b o t t l e s qnd h y d r o m e t e r s , D a t a fro^ b o t h m e t h o d s wort: p l o t t e d on t h e same g r a p h , n c u r v e drawn f o r e 3 c h method,

a n d a a e P n c u r v e p l o t t e d w h i c h was u s e d t o r e c d o f f t h e v a l u e s o f p (kerosene ) a t v a r i o u s t e m p e r n t u r e s . The c u r v e s a g r e e d w i t h i n

0 , 0 0 1 g / c c .

The p y c n o ~ s t o r b o t t l s w ~ s w e t g h c d , f i l l e d a b o u t one- t e n t h f u l l of' powder and w e i g h e d a g a i n . K e r o s e n e wc?s t h e n mixed w i t h t h e powder u n t i l n o b u b b l e s were s e e n r i s i n g t o t h e s u r f a c e on r e p e a t e d s t i r r i n g . The p y c n o m e t e r f u l l of k e r o s e n e and

powder were s e t I n n k e r o s e n e b . ? t h t o b r i n g then? t o t h e same t e m p e r a t u r e . When t h o t o ~ p e r t . t u r s of t h e k e r o s e n e i n t h e pycrlornetor was w i t h i n 1 / 2 ' ~ . of t h i t i n t h e b a t h t h e t e m p e r a t u r e o f thi: f o r v o r was r o c o r d e d s n d t h e t o p p l z c e d on t h e p y c n o m e t e r . The e x c e s s k e r o s e n e w s s relnoved f r o m t h e o u t s i d e w i t h a c l e a n r e g 7.nd t h e p y c n o m e t c r w z i g h e d . Thi: v o l u n e of k e r o s e n e , d e t e r r n 1 n e d . b ~ d i v i d i n g i t s w e . i g h t b y i t s d e n s i t y , was s u b t r a c t e d f r o m t h e volume of t h e p y c n o n e t e r t o g i v e t h e volurne of t h e powder. The weight of t h e powder wcs d i v i d i d by i t s v o l u m t o g f ve t h e d s n s f t y . I n e a c h c a s e d i f f e r e n t runs a g r e e d t;o w i t h i n 1%.

The b e d of powder w : ~ s p r ~ p a r e d a c c o r d i n g t o

A.S.T.M.

procedure. Two s e t s o f t o s t s wore r u n 011 t h e s a m p l e s ; one on

t h e s a m p l e s a s t h e y wore t a k e n m d t h e s e c o n d on s a m p l e s t h a t hnd b e e n d r i e d f o r a t l e a s t

24

h o u r s a t 1 3 5 ' O C . The d e n s i t y was -. d e t e r m i n e d f o r t h ~ d r i o d and u n d r i e d s a m p l e i n e a c h c a s e . D r i e d s a m p l e s were s t o r e d i n d e s i c c a t o r s u r l t i l u s e d . A l l c a l c u l a t i o n s were c s r r i e d o u t a s e x p l a i n e d i n A . S ,T :PI. p r o c e d u r e .

Fe s u l t s

--..-

TABLE 1 F i n e n u s s De t e r a i n a t i o n o f Cements

--

Cement

--.-

S p e c i f i c S u r f a c e Are a i n cm2/&

%

E r r o r C . C . C . P l a n t

#3

H u l l 2 , 9 1 0 C . C . C . Exshnw A l t z ~ . Bag #1 3 , 0 7 0 C . C . C . E x s h ~ i w A l t a , ( U s e d i r l r n o r t n r b n r s ) 3 , 1 0 0 C . C . C . B e l l e v i l l e , Ont. P l a n t

#5,

Bag

#3

2 , 3 6 0 C . C . C . B e l l e v i l l e , Ont. ( u s e d i n m o r t a r b a r s ) 2 , 7 9 0

C . C . C . Ii'ort Whfto, M211. Bag #2 2 , 9 4 0

C . C , C . P l a n t #8 P o r t C o l b o u r n e Bag #1 2 , 750

C , C , C . P l m t #1 P'iontreal B n g

#3

2 , 5 7 0

ENCI

Normal P o r t l a n d C e ~ e n t #2411.5 2 , 6 6 0 NOTE

-

C . C . C . r e f e r s t o Canadc Cement Company

-

ENCI r e f e r s t o R s p c c i o l c e v e n t r e c e i v e d f r o m H o l l a n d f o r :? c o - o p e r a t i v e t e s t . D i s c u s s i o n of R e s u l t s The r e s u l t s o b t a i n e d u s i n g t h a B l z i n e Air P e r m e a b i l i t y A p p a r ~ t u s s h o u l d n o t be c o n s i d e r e d a c c u r a t e a s a n a b s o l u t e v s a s u r e m e n t of t h e s p e c i f i c s u r f a c e . The ~ e t h o d d o e s p r o v i d e however, n r e a s o n a b l y good qnd r n p i d c o ~ p s r i s o n of t h e f i n e n e s s of d i f f a r o n . 1 ; m a t e r i a l s . The d o u b t of t h e a c c u r a c y o f t h o m t h o d a s rin ~ b s o l u t e ve,zsureve:nt m i s c s f r o m tlla f a c t t h z t t h e r e a r e l a r g e d i s c r e p a n c i e s b e t w e e n S .S

.A.

m e a s u r e m e n t made u s i n g t h e :.~li.r p o r ~ e n b l l i t y method a n d t h o s e u s i n g o t h e r m e t h o d s . The r e s t l l - t s obtn!.nod f o - t h e p o z z n l ~ n s u s i n g t h e s a m p l e s d r i e d a t

13s°C.

are of moro v a l ~ e t h a n t h o s e r u n on t h e r , s w st.,~npl-es. The p r e s e n c e o f ~ o i s t u r t : i n t h o s a m p l e ~ d ' f e c t s t h e d e n s i t y of t h e v n t e r i n l qnd a l s o c n u s e s I . t t o cl.,'!:lg t o g e t h e r w h i c h c o u s e s a s ~ a l l e r s u r f a c e t o b e p r o s e n t c d t o t h e . a i r . The

amount of w n t e r i n t h e p o z z o l ~ n w i l l ~ l l s o very cons.i.derr,bly n c c o r d l n g t o how i t was s t o r e d and h:indled. S n m p l e s t h a t h s v e b e e n d r i a d f o r n t l e a s t 2!4 h o u r s fit

13S0C.

w i l l h a v e l o s t a l l

C,lrt;.fr f r e e . n o i s t u r o .

The d r i a d c o n d i t i o l i c a n e r l s i l y b e r e p r o d u c e d i n sny

s:lrrrple and t h e r e f o r e p r o v i d e s a n Gnsy w9y t o g e t t h e s a m p l c s i n

a c o n d i t i o n s u i t a b l e f o r c o m p ~ . r i s o n of t h e i r f i n e n e s s . Thc p o s s i b l e e r r o r i n t h e d e t e r m i n a t i o n of t h e S.S.A. q u o t e d w i t h t h e r e s u l t s i n d i c ~ t e s on1.y t h e d l f f s r e n c e b e t w e e n t h e s z r e s u l t s a n d t h o s e t h n t m i g h t be o b t n i n e d b y o t h e r l n b o r a t o - r i p ! s u s i n g t h e Dl.qine A i r P e r x e a b i l i t y me tllod. D i s c r e p n n c i e s b e t w s e n d r f f e r e n t v e t h o d s a r e l i k o l g t o b e muci-1 l a r g e r ,

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London, 1011.

( 2 ) X u r s e , H.br. L p e c i f i c a t 5 o n 'i'csts f o r S p e c i f f c S u r f a c e of Cerobnts. Dcpartmont o f S c i e n t i f i c and l r l d u s t r i a l R e s e a r c h , 13uilding H e a e n r c t i S t a t i o n . R s p r i n t e d frorr? Cement and