An Analysis of Factors Affecting Particle-Size Distribution of Hydraulic Cements.pdf

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S u b h a s G . M a l g h a n ~ a n d L i n S i e n H . L u m ~

An Analys is of Factors Af fect ing Part ic le S ize Dist r ibut ion of

H y d ra u l i c C e m e n t s

REFERENCE: Malghan , S . G . and Lum, L . -S . H . , An A na lys i s o f

Facto rs Affect ing Particle-Size Distr ibu tion of Hyd raulic Cemen ts,

Cement Concrete and Aggregates CC AG DP, V ol . 13 , No . 2 , Win te r

1991, pp. 115-120.

ABSTRACT: Part icle-size distr ibution of hyd raulic cements plays an

indispensa ble role in control l ing the pro duct quali ty and m aintaining

rel iable performance in end applicat ions. Select ion of part icle-size

measurement methods is becoming increasingly complex due to the

ava i lab il i ty o f a va r ie ty o f ins t ruments based o n d i f fe ren t measure -

ment principles. This paper discusses the primary cr i ter ia to be met

by a part icle-size distr ibution analyz er for applicat ions in hydraulic

cement charac te r iza t ion . Amon g the severa l me thods ava i lab le fo r

measuring the part icle-size distr ibution, a l ight diffract ion technique

was ut i l ized to examine the effect of dispersion solvents on the re-

sul t ing size distr ibution . Dist i l led water , d is t i l led wate r containing a

polyac rylate surfactant , isopro pyl alcohol , and a comm ercial ly avail-

able organ ic surfactant were used as dispersion solvents. The result ing

data are analyzed with respect to variat ions due to the dispersion

solvents and factors responsible for the observed variat ions.

KEY WORDS: part icle-size distr ibution , hydraulic cements, d isper-

sion in solvents , m ethods o f s ize analysis , l ight scat ter ing, instrument

se lec t ion , sample p re para t ion

M o r e t h a n o n e p r o p e r t y o f h y d r a u l i c c e m e n t i s r e l e v a n t in

d e f i n i n g i ts c h a r a c t e ri s t i c s . M a n y o f t h e s e p r o p e r t i e s a r e r e l a t e d

t o s o m e o f t h e m o r e f u n d a m e n t a l m e a s u r e m e n t s o f p a r ti c l es su c h

a s m e a n s i z e , s i z e d i s t r i b u t i o n , s h a p e , c o n c e n t r a t i o n a n d f o r m

o f i m p u r i t ie s , a n d s u r fa c e c h e m i c a l c o m p o s i t io n . T h e m e a s u r e -

m e n t o f p a r t i c l e - s i z e d i s t r i b u t i o n c o n s t i t u t e s o n e o f t h e m o s t

i m p o r t a n t a s p e c ts o f h y d r a u l i c c e m e n t c h a r a c t e r iz a t i o n b e c a u s e

p a r t i c l e s iz e a f f e c ts h o m o g e n e i t y , s e t t l in g t i m e , a n d s t r e f i g t h o f

t h e f i n a l p r o d u c t . T h e r e f o r e , s i z e d i s t r i b u t i o n o f t h e c e m e n t p a r -

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

o r f o r o n - l i n e m e a s u r e m e n t i n p r o c e s s c o n t r o l .

I n r e c e n t y e a r s , t h e a v a i l a b i l i t y o f p a r t i c l e - si z e m e a s u r e m e n t

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

p h y s i c a l p r i n c i p l e s . T h e r a n g e o f p a r t ic l e - s i z e m e a s u r e m e n t c o v -

e r e d b y e a c h i n s t r u m e n t h a s al s o b r o a d e n e d . S o m e o f t h e d r iv i n g

f o r c e s f o r t h e a v a i l a b i l i t y o f a l a r g e n u m b e r o f s y s t e m s a r e : i n -

c r e a s e d r e c o g n i t i o n o f a n e e d f o r m e a s u r e m e n t o f p a r t i c le - s i z e

d i s t r i b u t i o n , e m p h a s i s o n q u a l i t y c o n t r o l a n d r e l i a b i l i t y , a n d a

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

I n r e s p o n s e t o t h e s e t e c h n i c a l a n d m a r k e t - d r i v e n f o r c e s , n u -

m e r o u s p a r t ic l e - si z e m e a s u r e m e n t s y s te m s h a v e b e e n d e v e l o p e d .

T h i s p a p e r d i s c u s s e s s t e p s i n v o l v e d i n t h e p a r t i c l e - s i z e m e a s u r e -

m e n t , d e s c r i b e s a c l a s s i fi c a t i o n o f m e a s u r e m e n t m e t h o d s , a n d

~Group leader , Ceramics Division, and chemical engineer , respec-

t ive ly , Na t iona l Ins t i tu te o f S tandards and Techno logy , Ga i the rsburg ,

M D .

© 99 by the Am er ican Soci e ty fo r Test i ng and Mater ia l s

5

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

t i o n , r e s u l t s a r e g i v e n f o r t h e m e a s u r e m e n t o f p a r t i c le - s i z e d i s -

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

a q u e o u s l i q u i d e n v i r o n m e n t . A l i g h t d i f f r a c ti o n t e c h n i q u e w a s

u s e d i n t h e s e s t u d i e s s i n c e i t i s n o t a f f e c t e d b y d e n s i t y d i f f e r e n c e s

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

Steps Inv olve d in Particle Size Analysis

S o m e o f t h e r e q u i r e m e n t s o f t h e s i z e a n al y s i s a r e t o o b t a i n

d a t a i n s i m i l a r c o n d i t i o n s t o t h a t e x i s t i n g in t h e p r o c e s s o r t o

m e e t t e c h n i c a l s p e c i fi c a t i o n s o f t h e c e m e n t . T h i s n e c e s s i t a t e s

o b t a i n i n g a r e p r e s e n t a t i v e s a m p l e f r o m a b u l k l o t. T h e s e c o n d

r e q u i r e m e n t i s t h e d i s p e r s i o n o f p a r t i c le s in a c h o s e n s o l v e n t s o

t h a t t r u e p a r t i c l e s i z e ( a s d e t e r m i n e d b y s c a n n i n g e l e c t r o n o r

o p t i c a l m i c r o s c o p y ) i s d e t e r m i n e d . D r y t e c h n i q u e s d o n o t r e q u i r e

t h e u s e o f s o l v e n t s f o r d i s p e r s io n . H o w e v e r , a s t h e m e a n p a r t i c l e

s i ze o f t h e h y d r a u l i c c e m e n t b e c o m e s s m a l l e r , d i s p e r s i o n - r e l a t e d

e r r o r s i n c r e a s e . F o r c e m e n t s o f p a r t i c l e s si z e s i n t h e 1 t o 1 0 0 -

I xm r a n g e , w e t t e c h n i q u e s a r e g e n e r a l l y p r e f e r r e d . T h e t h i r d

r e q u i r e m e n t i n t h e p a r t i c le - s i ze m e a s u r e m e n t i s t h e a p p r o p r i a t e

u s e o f s t a n d a r d m a t e r i a l s a n d p r o c e d u r e s f o r m a t e r i a l a n d i n -

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

c a l i b ra t i o n e r r o r s u s in g t h e a p p r o p r i a t e s t a n d a r d m a t e r i a ls . T h e

s t e p s i n v o l v e d [ 1] i n t h e p a r t i c l e - s i z e m e a s u r e m e n t a r e s h o w n

s c h e m a t i c a l l y in F i g . 1 . T h e o v e r a l l m e a s u r e m e n t e r r o r i s a f u n c -

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

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

d u e t o s a m p l i n g a r e e x p e c t e d t o d o m i n a t e [ • ] .

Selection Criteria and Typ es of PSD Measurem ent Techniques

S e l e c t i o n o f a p a r t i c u l a r t e c h n i q u e f o r s iz e d i s t r i b u t i o n m e a s -

u r e m e n t i s d e p e n d e n t o n s e v e r a l c r i t e r i a [ • - 4] :

1 . A c c u r a c y o f m e a s u r e m e n t ( s y s t e m a t i c e r r o r ) .

2 . R e p r o d u c i b i l i t y a n d r e p e a t a b i l i ty o f m e a s u r e m e n t ( r a n d o m

e r r o r ) .

3 . C h e m i c a l r e a c t i o n o f p a r t i c l e s w i t h l i q u id .

4 . S i z e r a n g e o f a p p l i c a t i o n .

5 . T i m e r e q u i r e d f or m e a s u r e m e n t .

6 . S k i l l l e v e l o f o p e r a t o r .

7 . C o s t o f i n s t r u m e n t .

A c c u r a t e m e a s u r e m e n t o f p a r t i c le - s iz e d i s tr i b u t io n r e q u i r e s

t h e d e v e l o p m e n t o f i m p r o v e d t e c h n i q u e s o f s a m p l e p r e p a r a t i o n

a n d a s s o c i a t e d m e a s u r e m e n t t e c h n i q u e s . S y s t e m a t i c e r r o r s c a n

b e m i n i m i z e d b y e n h a n c e d p r e c i s i o n ( a g r e e m e n t w i t h i n a s e t o f

o b s e r v a t i o n s o b t a i n e d a s d i r e c t e d i n a m e t h o d ) a n d r e p e a t a b i l i t y

This standard is for EDUCATIONAL USE ONLY.


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116 CEMENT CONCRETE AND AGGREGATES

I H o m o g e n i z a t i o n o f C e m e nt

4

I S a m p ll n g r o m a L a r g e L o t I

P r e p a r a t i o n

nd Dispersion

]

[ a l i b r a t l o n o f n s tr u me n t ]

l

1 . = = I

Interpretation

nd onversion of Data

FIG. 1 S c h e m a t i c o f s t e p s i n v o l v e d m t h e m e a s ur e m en t Q f p a n i c ~

size d ~tribution.

( c o m p a r i s o n o f d a t a o b t a i n e d i n a si n gl e l a b o r a t o r y a n d t e c h -

n i que ) . Howe ve r , r e p r oduc i b i l i t y i s t o t a l l y de pe nde n t on p r e c i -

s i on i n v o l v in g c o m p a r i s o n b e t w e e n l a b o r a t o r ie s a n d / o r b e t w e e n

d i f f e re n t t e c hn i que s . Ac c u r a c y o f t he t e c hn i que i s e nha n c e d wh e n

t h e d e g r e e o f a g r e e m e n t b e t w e e n t h e t r u e a n d a v e r a g e o f m a n y

obs e r ve d va l ue s i nc r e a s e s .

S i nc e hyd r a u l i c c e me n t s r e a c t w i th a que ou s e nv i r onm e n t , o t he r

s o l ve n t s , e s pe c i a l l y o r ga n i c s o l ve n t s , c a n be u s e d . Howe ve r , f o r

e a s e o f ha nd l i ng a nd c o s t e ff e c t i ve ne s s , t he u s e o f wa t e r - ba s e d

dispersants i s des i rable . D ispers ion of cem ent par t ic les in aqueo us

e n v i r o n m e n t c a n b e c a r r ie d o u t i n t h e p r e s e n c e o f l o w - m o l e c u l a r -

we i gh t ( 5000 t o 10 000 ) po l ya c r y l a t e s , wh i c h p r ov i de s t e r i c s t a -

b i l i z a ti on [ 5 ] a t h i gh pH. Exa m pl e s o f o r ga n i c d i s pe r s a n t s a r e

a l c oho l s a nd c omme r c i a l l y a va i l a b l e mi ne r a l o i l - ba s e d s o l ve n t s .

T h e c o s t o f th e i n s t r u m e n t , t h e t i m e r e q u i r e m e n t f o r a n a ly s i s,

a nd t he s k il l l e ve l o f t he ope r a t o r , e t c , a r e s om e o f t he e x t e r na l

f a c t o r s wh i c h i n f l ue nc e t he de c i s i on on t he s e l e c t i on o f i n s tr u -

me n t s . Th e ov e r a l l c o s t o f a na ly s i s s hou l d a l s o inc l ude t hos e due

t o t he i n s t r ume n t s , d i s pe r s i on s o l ve n t s , a nd c e me n t s a mp l e s .

W he n e x t e ns i ve c l e a n i ng be t we e n t he r uns i s ne c e s s a r y , t he ove r -

a ll c o s t i nc r e a s e s . The t i me r e qu i r e m e n t f o r a na ly s i s c a n r a nge

f r om 5 r a i n t o s e ve r a l hou r s de pe nd i ng on t he pa r t i c l e - s i z e d i s -

t r i bu t i on o f a s pe c i fi c ma t e r i a l , i n s t r um e n t p r i nc i p l e , a nd d i s -

pe r s i on p r e pa r a t i on . I n s t r ume n t s ba s e d on l i gh t s c a t t e r i ng o f f e r

h i gh s pe e d o f ope r a t i on . T he s e l e c t i on o f t he s e i n s t r ume n t s i s

de p e nde n t o n t he sk il l le ve l o f the ope r a t o r ( e . g . , p r odu c t i on

e n v i r o n m e n t v e r s u s r e s e a r c h l a b o r a t o r y ) , I n m o s t c a s e s , a r e a -

s ona b l y we l l - t r a i ne d ope r a t o r i s r e qu i r e d .

T h e r e f o r e , t h e q u e s t i o n o f w h i c h t e c h n i q u e / i n s tr u m e n t t o s e -

l e c t f o r a g i ve n a pp l i c a t i on l e a ds t o t he a na l y s i s o f f a c t o r s a f -

f e c t i ng pa r t i c l e -s i z e d i s t r i bu t i on a n d s pe c i f i c r e qu i r e m e n t s o f t he

p r o c e ss . T h e m y r i a d o f a n a ly s i s te c h n i q u e s , m e a s u r e m e n t p a -

r a m e t e r s , a n d t h e n o m i n a l r a n g e o f a p p li c a ti o n o f t h e s e t e c h -

n i q u e s a r e b r o a d l y g r o u p e d i n T a b l e 1 .

W e t V e r s u s D r y M e t h o d s

Th e po t e n t i a l f o r de t e r mi n i ng t he pa r t i c le - s i z e d i s tr i bu t i on a c -

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

c a n be d i s pe r s e d . As t he pa r t i c l e s be c ome s ma l l e r t he i r t e nde nc y

t o a d h e r e t o e a c h o t h e r i n c r e a s e s d u e t o v a n d e r W a a l s a n d

c ou l ombi c a t t r a c t i ve ( be t we e n c he mi c a l l y d i s s i mi l a r pa r t i c l e s )

f o r c e s. H e n c e , i n a d r y m o d e o f p a rt i cl e -s i z e m e a s u r e m e n t , a g -

g l ome r a t i on o r t he t e nde nc y o f f i ne pa r t i c l e s t o s t i c k t o l a r ge

one s c a nno t be e a s i l y c on t r o l l e d . The r e f o r e , a c c u r a t e a nd r e -

p r o d u c i b l e s i ze d i s tr i b u ti o n m e a s u r e m e n t m a y n o t b e o b t a i n e d

b y m e t h o d s b a s e d o n d r y p a r t i c u l at e s . I n a d d i ti o n , a c c u r a c y o f

qua n t i t a t i ve de t e r m i na t i on o f t he f i ne s t s i ze f r a c t ion i s d i mi n i s he d

i n t he c a s e o f d r y powde r s .

T h o u g h w e t t e c h n i q u e s a r e p r e f e r r e d o v e r d r y te c h n i q u e s , t h e y

s u f f e r f r o m i n t e ra c t i o n s b e t w e e n t h e p a r t ic l e s a n d s u r r o u n d i n g

s o l v e n t . W h e n t h e h y d r a u l i c c e m e n t c o m e s i n c o n t a c t w i t h a

s o l ve n t , t he s i l ic a t e s a nd a l umi n a t e s o f l ime a r e e xpe c t e d t o

und e r go s u r f a c e d i s s o l u t ion a nd t he r e by c o n t r i bu t e s i on i c s pe c i e s

t o t he a d j o i n i ng b u l k s o l u t i on . Th e e x t e n t o f s u r f a c e d i s s o l u ti on

d e p e n d s o n a n u m b e r o f c h a r ac t e r is t ic s o f w h i c h t h e c h e m i c a l

c o m p o s i t i o n o f t h e c e m e n t a n d t h a t o f t h e s o lv e n t a r e t h e m o s t

i mpor t a n t , Wa t e r , be i ng a po l a r s o l ve n t , i nduc e s h i ghe r s u r f a c e

d i s s o l u t i on t ha n o r ga n i c s o l ve n t s . The r e s u l t i ng e l e c t r i c a l doub l e

l a ye r p r ope r t i e s o f a g i ve n c e me n t pa r t i c l e a r e e xpe c t e d t o be

d i f f e r e n t i n wa t e r t ha n i n o r ga n i c s o l ve n t s . The e l e c t ri c a l doub l e

l a ye r f o r m a t i on a nd t he r e s u l t i ng d i s pe r s ion p r o pe r t i e s a r e de -

s c r i be d e l s e wh e r e [ 6] .

S i z e D i s t r i b u t i o n M e a s u r e m e n t i n W e t D i s p e r s i o n s

The p r i ma r y goa l o f t he me a s u r e me n t o f pa r t i c l e - s i z e d i s t r i -

bu t i on i s to de t e r m i ne t he a bs o l u t e s i ze d i s t ri bu t i on o f t he pa r -

t i cl e s i n t he c e m e n t s a mp l e . The r e f o r e , t he f o r ma t i on o f a g -

g l o m e r a t e s s h o u l d b e p r e v e n t e d . T h e m a j o r s t e ps i n v o l v e d in t h e

p r e p a r a t i o n o f h i gh l y d e a g g l o m e r a t e d d i s p e r s i o n s in a q u e o u s a n d

nona que ous s o l ve n t s a r e s hown i n F i g . 2 .

I n t h e c a s e o f h y d r a u l i c c e m e n t , o b t a i n i n g a r e p r e s e n t a t iv e

s a mp l e f o r s i z e d i s t r i bu t i on m e a s u r e m e n t i nvo l ve s the u s e o f a

s p i nn i ng r i f f l e r [ 2 ] . S i nc e c e me n t i s a h i gh l y he t e r oge ne ous ma -

TABLE 1--Techniques of particle size analysis an d a typical

mea surem ent para meter 1~ 41

Measurement Nom inal Range,

Techniques Diameter Ixm

Image Image 0 ,5-1000

Optical 0.01 - 10

Electron

Mechanical sieving

Dr y

Wet

Sedimentation

Elutriation

Gravity

Centrifugal

Zone sensing

Optical

Resistivity

Hydrodynamic

chromatography

Brownian motion

Other

Gas adsorption

Gas permeability

Mercury intrusion

Sieve/mechn-

ical

Dynamic/

Stoke s

Geometric

Geometric

Geometric

Equivalent

spherical

> 10

> 2

1- 100

0.1-130

0.05-100

0.01 - 500

0,05-500

0 . 0 t - 1 . 0

0 . 01 - I

0 .05-50

O . 1 4 0

O. 1 200



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M LGH N ND LUM ON HYDR ULIC CEMENTS 7

D r y S a m p l e P r e p a r a t i o n ]

[ W e t t i n g n d M i x i n g l t h a S u r f a e ta n t

r . = . o o I

I M e a s u r e m e n t f S l z e D i st r i b u t l o n 1

I

[ P r e se n t at i o n f D a t a

[

FIG. 2 - - S e q u en ce o f st eps i n vo l ved i n t h e m ea su rem en t o f p a r ti c le -

si ze d is tr ibut ion by wet t ing the cem ent .

s h o u l d b e t h e s a m e a s t h a t u s e d i n t h e p r e p a r a t i o n o f th e p a r e n t

s u s p e n s i o n . C a r e s h o u l d b e e x e r c i s e d t o a v o i d s e t t l in g o f c o a r s e

p a r t ic l e s d u r i n g s a m p l i n g o f t h e p a r e n t s u s p e n s i o n .

P r e s e n t a t i o n o f th e d a t a is d e p e n d e n t o n t h e e q u i p m e n t . M o s t

o f t e n , t h e d a t a a r e p r o v i d e d i n t h e f o r m o f n u m b e r o r w e i g h t /

v o l u m e f r a c t i o n . D i r e c t c o n v e r s i o n o f d a t a f r o m t h e n u m b e r t o

w e i g h t / v o l u m e f r a c t i o n i s n o t p o s s i b l e w i t h o u t t a k i n g i n t o a c -

c o u n t d e n s i t ie s o f d if f e r e n t c h e m i c a l c o m p o n e n t s o f t h e h y d r a u l i c

c e me n t . S i mi l a r l y , t he s i z e d i s t r i bu t i on da t a f r om g r a v i t a t i ona l

a nd c e n t r i f uga l s e d i me n t a t i on de v i c e s is a f f e c t e d by d i f f e r e n t

d e n s i ti e s o f t h e c o n s t i t u ti n g c h e m i c a l c o m p o n e n t s o f t h e c e m e n t .

T h i s i s p r o b a b l y o n e o f t h e m a i n r e a s o n s f o r u s i n g th e l i g h t

d i f f r a c t i o n - b a s e d d e v i c e i n t h i s s t u d y f o r t h e s i z e m e a s u r e m e n t

o f c e m e n t . I r r e s p e c t i v e o f t h e m e t h o d o f s iz e m e a s u r e m e n t , t h e

r e s u l ti n g d a t a c a n b e a n a l y z e d b y u s i n g a n u m b e r o f m a t h e m a t i c a l

m o d e l s . T h e p a r a m e t e r s o f t h e s e m o d e l s c a n s er v e t h e p u r p o s e

o f c o m p a r i n g t h e c h a r a c t e r is t i c s o f v a r i o u s c e m e n t s .

t e ri a l c o n s i s t in g o f c h e m i c a l c o m p o n e n t s o f v a r i o u s s iz e s a n d

de ns i t i e s , s e g r e ga t i on i s a s e r i ous i s s ue . The r e f o r e , c a r e s hou l d

b e e x e r c i s e d i n t h e d i v i s i o n o f a b u lk l o t o f c e m e n t s a m p l e i n t o

s u b s a m p l e s . E a c h t y p e o f in s t r u m e n t r e q u i r e s a d i f fe r e n t w e i g h t

o f th e s a m p l e . E r r o r s i n s a m p l i n g c a n b e m i n i m i z e d b y u s i n g th e

l a r ge s t pos s i b l e s ubs a m pl e f o r a na l y s i s c ons i s t e n t w i t h t he s a m p l e

r e q u i r e m e n t . F o r f i n e - si z e c e m e n t s , w e t s a m p l e s o f h i g h e r t h a n

t h e r e q u i r e d p a r t i c l e c o n c e n t r a t i o n c a n b e p r e p a r e d , a n d t h e f i n a l

s a m p l e f o r s i z e d e t e r m i n a t i o n c a n b e t a k e n f r o m t h i s p a r e n t

s a m p l e . W h e n d i l u ti o n o f th e p a r e n t s a m p l e i s i n v o l v e d , th e

s u r f a c t a n t c o n c e n t r a t i o n i n t h e f i n a l d i s p e r s i o n s h o u l d b e m a i n -

t a i ne d a t t he s a me l e ve l a s i n t he pa r e n t s a mp l e .

W e t t i n g a n d m i x i n g o f t h e p o w d e r r e q u i r e s t h e s e l e c t i o n o f a

p r o p e r c o m b i n a t i o n o f t h e s o l v e n t a n d a s u r f a c t a n t . O r g a n i c o r

i n o r g a n i c s u r f a c t a n ts [ 6 ] c a n b e u s e d ; h o w e v e r , o r g a n i c d i s p e r -

s a n t s p r ov i de h i ghe r f l e x i b i l i t y a nd mor e de f i n i t e d i s pe r s i on i n

c o m p l e x c h e m i c a l s y s te m s . W a t e r i s a p r e f e r r e d s o l v e n t , t h o u g h

i t ha s c e r t a i n d i s a d va n t a g e s , s uc h a s s u r f a c e d i s s o l u t i on , s we l l i ng ,

a nd s e tt i ng . I n d i l u t e s u s pe ns i ons (l e s s t ha n 1 by we i gh t ) , t he

e f f e c ts o f t h e s e i n t e r a c ti o n s a r e c o n s i d e r e d t o b e m i n i m u m .

T h e s e l e c t i o n o f an a p p r o p r i a t e d i s p e r s a n t r e q u i r e s t h e k n o w l -

e dge o f s u r f a c e c ha r ge a nd i s oe l e c t r i c po i n t , pH~ep ( t he p H a t

w h i c h t h e p a r t i c le s c a r r y a n e t z e r o c h a r g e ) o f t h e c e m e n t p a r -

t i c l e s i n a g i ve n s o l ve n t . S i nc e c e me n t ha s a h i gh l y c ompl e x

c h e m i c a l c o m p o s i t i o n , a c c u r a t e d e t e r m i n a t i o n o f p H ie p b y t r a -

d i t i o n a l e l e c t r o k i n e t i c t e c h n i q u e s i s s o m e w h a t t e d i o u s a n d d i f -

f i c u l t. Ho we ve r , ba s e d on r e l a t i ve we i gh t r a t i o s o f s i l ic a t e s , a l-

u m i n a t e s , a n d o t h e r c o m p o n e n t s , t h e p H i ep c a n b e e s t i m a t e d .

A l s o , e x p e r i m e n t a l d e t e r m i n a t i o n o f t h e p H~ ep is p o s s ib l e b y t h e

a p p l i c a ti o n o f a r e l a t iv e l y n e w t e c h n i q u e i n w h i c h e l e c t r o k in e t i c

s o n i c a m p l i t u d e i s m e a s u r e d [ 7] a s a f u n c t i o n o f p H .

U l t r a s o n i c a t i o n o f t h e s l u r ry c o n t a i n i n g t h e c e m e n t p a r t i c le s

i s a n e s s en t i a l s t e p i n t h e p r e p a r a t i o n o f w e l l -d i s p e rs e d s u s p e n -

s i ons . Dur i ng u l t r a s on i c a t i on , t he pa r t i c l e s a r e s ub j e c t e d t o c a v -

i t a t i on wh i c h d i s l odge s l oos e l y he l d pa r t i c l e s [ 8] . Tw o p r i m a r y

d e v i c e s o f u l t r a s o n i c a t io n a r e b a t h s a n d p r o b e s . T h e p r o b e i s a

p r e f e r r e d d e v i c e b e c a u s e i t a l l o w s t h e a p p l i c a t i o n o f a s p e c i f i c

q u a n t i t y o f u lt r a s o n i c p o w e r l o c a l i z e d t o th e s a m p l e . U l t r a s o n -

i c a t i o n b y t h e p r o b e i s c o m p l e t e d i n ju s t a f e w m i n u t e s s i n ce t h e

powe r i n t e ns i t y i s h i gh .

Th e s i z e d i s t r i bu t i on o f a we l l - d i s pe r s e d s l u r r y is de t e r m i ne d

b y f o l l o w i n g t h e r e c o m m e n d e d p r o c e d u r e o f a p a r t i c u l a r e q u i p -

m e n t . I f t h e s u s p e n s i o n h a s t o b e d i l u t e d , t h e s o l v e n t c h e m i s t r y

A p p l i c a t io n o f t h e L i g h t S c a t t e r in g M e t h o d

T h e p a r t i c l e - s i z e d i s t r i b u t i o n o f P o r t l a n d C e m e n t P r o f i c i e n c y

S a m p l e 9 5 [9 ], d i st r i b u te d b y t h e C e m e n t a n d C o n c r e t e R e f e r -

e n c e L a b o r a t o r y ( C C R L ) , w a s d e t e r m i n e d u s i n g a li g h t d i f fr a c -

t i o n - b a s e d p a r t i c l e - s i z e m e a s u r e m e n t s y s t e m ( H o r i b a L A - 5 0 0 )

[10]. C C R L is a r e s ea r c h a s s o c ia t e p r o g r a m a t N I S T s p o n s o r e d

b y A S T M [11]. T h e p r i m a r y f o c u s o f t h is s t u d y w a s t o e x a m i n e

t h e i n f l u e n c e o f s o l v e n t s in w h i c h t h e c e m e n t i s d is p e r s e d . T h e

s o l ve n t s e xa mi ne d we r e d i s t i l l e d wa t e r , d i s t i l l e d wa t e r c on t a i n i ng

5 0 0 p p m p o l y a c r y l a t e ( D a r v a n C - V a n d e r b i l t C h e m i c a l C o m -

pa ny ) a s a d i s pe r s a n t , i s op r opy l a l c oho l , a nd Se d i s pe r s e A- 12 ( a

s u r f a c t a n t m a n u f a c t u r e d b y M i c r o m e r i t i c s C o r p o r a t i o n ) . 2

D i s p e r s i o n s o f t h e c e m e n t w e r e p r e p a r e d b y m i x in g c e m e n t

a nd t he s o l ve n t i n t he we i gh t r a t i o o f 1 t o 20 , f o l l owe d by u l t r a -

s o n i c a t io n ( u l t r a s o n i c p r o b e o f 1 9 m m d i a m e t e r , 3 0 W , t o t a l o f

3 r a i n ) . The d i s pe r s i on wa s u l t r a s on i c a t e d s t e pwi s e by a pp l y i ng

p o w e r f o r 1 m i n f o l lo w e d b y 1 r a in o f c o o l in g . T h i s p r o c e s s w a s

r e pe a t e d t o g i ve a t o t a l u t t r a s on i c a t i on t i me o f 3 ra i n . The d i s -

p e r s e d p o w d e r s w e r e s i z e a n a l y z e d u s in g a p r o c e d u r e d e v e l o p e d

f o r c e r a m i c p o w d e r s . E a c h m e a s u r e m e n t i s a n a v e r a g e o f 2 5

s c a ns , a nd t r i p l i c a t e da t a we r e ob t a i ne d u s i ng t h r e e s e pa r a t e

s u b s a m p l e s f r o m t h e p r i m a r y d i s p e r s io n . T h e d a t a p r e s e n t e d a r e

a n a v e r a g e o f t h e t h r e e m e a s u r e m e n t s .

T h e s i z e d i s t ri b u t io n d a t a o f t h e c e m e n t s a m p l e a r e p r e s e n t e d

i n F i g . 3 . I n ge ne r a l , a l l f ou r d i s pe r s i ons s how a b i moda l s i z e

d i s t ri b u t i o n i n w h i c h t h e r e i s a sm a l l q u a n t i t y o f s u b m i c r o m e t r e

f r a c t io n a n d a l a r g e q u a n t i t y o f f r a c ti o n w h o s e ds i s i n t he r a n ge

o f 10 t o 20 p .m . The d so i s t he s i z e i n mi c r om e t r e s t h r o ugh wh i c h

50 o f t he pa r t i c l e s pa s s . Th e f o l l owi ng ge ne r a l gu i de l i ne wa s

us e d i n t he e v a l ua t i on o f t he e f f e c t i ve ne s s o f s o l ve n t s a nd d i s -

p e r s a n t s : t h e m o s t s u i ta b l e s o l v e n t - d i s p e r sa n t c o m b i n a t i o n i s o n e

t ha t g i ve s t he f i ne s t s i z e d i s t r i bu t i on . Ba s e d on t h i s c r i t e r i on ,

i s o p r o p y l a l co h o l ( I P A ) a p p e a r s t o b e t h e m o s t s u i ta b l e s o l v e n t .

O n t he o t h e r ha nd , S e d i s pe r s e A - 12 is t he l e a s t e f f e c t i ve d i s -

p e r s a n t . B o t h w a t e r a n d w a t e r c o n t a i n i n g 5 0 0 p p m D a r v a n C

g i ve s i mi l a r s iz e d i s t r i bu t i ons i n t he f i ne - s i z e r a nge a nd a s l i gh tl y

2Certain comm ercial equipment, vendors, instruments, o r materials

are identified in this report in ord er to describe adequately experimental

requirements. In no case does such identification imply recomm endation

or endorsement by the National Insti tute of Standards and Technology,

nor does it imply that the vendor, material, or equipment identified is

necessarily the best available for the purpose.



4/6

8 C E M E N T ,CONCR ETE, AND AG GREGATES

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P a r t i c l e D i a m e t e r , m i c r o n s

FI G.

3- -S iz e distribution data of CC RL portland cemen t proficiency sam ple by using Horiba LA-5 00

device. The effect of fou r solvents is show n: 1) water; 2) water plus 500 pp m Darvan C; 3) 1PA; and

4) Sedisperse A-12.

d i f f e r e n t dgo . Th e ov e r a l l d i f f e r e nc e s i n t he e n t i r e s i z e r a nge a r e

p r e s e n t e d i n F ig . 4 . The s e da t a , i n t e r ms o f c umul a t i ve s i z e

f r a c t i on , s ho w t ha t I P A i s by f a r a s upe r i o r s o l ve n t . Th e dg0 , d s 0,

a nd d25 da t a s um ma r i z e d i n Ta b l e 2 s ho w s pe c i f i c d i f f e r e nc e s i n

t he s i z e d i s t r i bu t i ons . The s i z e d i s t r i bu t i on da t a a r e p r e s e n t e d i n

t e r m s o f w e i g h t f r a c ti o n b y a s s u m i n g t h a t d e n s i t y v a r i a ti o n b e -

t we e n t he pa r t i c le s i s ne g l ig i b l e .

A n o t h e r im p o r t a n t f e a tu r e o f t h e s e d a t a is t h a t 9 0 o f t h e

w e i g h t is fi n e r t h a n 1 9 ~ m i n t h e c a se o f I P A . W h e n u s in g o t h e r

s o l ve n t s , a c oa r s e r s i z e d i s t r i bu t i on i s obs e r ve d . I n a dd i t i on , i n

t h e c a s e o f I P A , m o r e f i n e s a r e o b s e r v e d a t t h e f i n e r e n d o f s i ze

d i s t r i bu t i on . A p os s i b l e r e a s on f o r I P A ' s s upe r i o r i t y in t hi s pa r -

t i c u l a r c a s e i s i ts i ne r t ne s s t o s u r f a c e r e a c t i v i t y w i t h c e m e n t pa r -

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FIG.

4- -S iz e distribution data of Fig. 3 presented in the form of cumulative weight fraction to highlight

differences in the entire size distribution,



5/6

T A B L E

2- -E ffe ct o f solvent on the dispersion o f a cement sample

CCRL Portland Cement Proficiency Sample 95) during particle-size

determination by Horiba LA-500.

Size in M icrometres Through

Which the Sp ecific Weight

Percent Passes

d9o dso dz5

IP A 19.0 9.0 3.6

W ater 26.0 12.0 7.5

Water + Darv an C 30.0 13.0 7.5

A-12 30.0 i t . 0 5 .0

B i m o d a l d i s t r ib u t i o n o b t a i n e d f o r t h i s s a m p l e c o u l d b e t h e

r e s u l t o f t h e a p p l i c a t i o n o f b o t h u l t r a s o n i c a t i o n e n e r g y a n d s o l-

v e n t s f o r d is p e r s i o n . F i n e , s u b m i c r o m e t r e p a r t i cl e s l o o s e l y a d -

h e r e d t o c o a r s e p a r t i c l e s t e n d t o d i s l o d g e b y t h e a p p l i c a t i o n o f

a c o m b i n a t i o n o f m e c h a n i c a l u l t r a s o n i c a ti o n p r o m o t i n g c a vi -

t a t i o n ) a n d s u r f a c e c h e m i c a l s t e ri c i n t h e c a s e o f I P A a n d A -

12 ) d i s pe r s i ve f o r c e s . Dur i ng u l t r a s on i c a t i on , t he pa r t i c l e s a r e

s u b j e c t e d t o c a v i t a t io n w h i c h s e p a r a t e s l o o s e l y h e l d p a r t ic l e s.

O n c e t h e p a r t i c l e s a r e s e p a r a t e d , t h e y a r e k e p t d i s p e r s e d b y t h e

s t e r i c f o r c e s i m p a r t e d b y t h e a d s o r b e d h y d r o c a r b o n m o l e c u l e s

o f I P A . I f t h e s i ze d i s t r ib u t i o n i s c a r r i e d o u t b y d r y s i e v i n g , th e

b i m o d a l d i s t r i b u ti o n m a y n o t b e o b s e r v e d i n s u c h d et a il .

Re p e a t a b i l i t y o f t he s i z e d i s t r i bu t i on da t a i s s how n i n F i g s . 5

a n d 6 f o r I P A a n d S e d i s p e r s e A - 1 2 , r e s p e c t i v e l y . T h e s e d a t a

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

e x c e l l e n t i n t h e c a s e o f f i n e- s iz e f r a c t io n < 1 . 0 ~ m ) . H o w e v e r ,

t he r e i s a s l igh t l y l a r ge r va r i a t i on a t t he c oa r s e - s i z e f r a c t i on whe n

u s i n g I P A ; w h e r e a s , f o r S e d i s p e r s e A - 1 2 , t h e v a r i a t i o n i s n e g -

M A L G H A N A N D L U M O N H Y D R A U L I C C E M E N T S 9

l i g ib l e . S i nc e t he f i na l s e l e c t i on o f a s o l ve n t - d i s pe r s a n t s hou l d

i n c l u d e t h e e v a l u a t i o n o f b o t h a c c u r a c y a n d r e p e a t a b i l i ty , a t h o r -

o u g h e v a l u a t i o n o f t h o s e f a c t o r s is r e q u i r e d i n a r o u n d - r o b i n

c h a r a c t e r i z a t i o n p r o g r a m .

Summ ary and onclusions

M a j o r s t e p s in v o l v e d i n t h e m e a s u r e m e n t o f p a r ti c le - s iz e d i s -

t r i b u t io n a r e s a m p l i n g a n d sa m p l e p r e p a r a t i o n i n c l u d in g d is -

p e r s i o n ) . E r r o r s i n t h e s e s t e p s a r e o f t e n r e s p o n s i b l e f o r l a c k o f

r e p e a t a b i l it y a n d r e p r o d u c i b i li t y . A l a r g e n u m b e r o f s y s t e m s a r e

a v a i la b l e t h a t p r o v i d e d a t a o v e r a w i d e r a n g e o f s i ze d i s t ri b u t io n s .

T h e s e l e c t io n o f i n s t r u m e n t s f o r a g i v e n a p p l ic a t i o n d e p e n d s o n

a n u m b e r o f c r it e r ia . I n r e c e n t y e a r s , s y s t e m s b a s e d o n l i g h t-

s c a t t e r i ng p r i nc i p l e s a r e w i de l y u s e d f o r pa r t i c u l a t e s y s t e ms .

D i s p e r s i o n o f h y d r a u l i c c e m e n t p a r t i c l e s i n a s u i ta b l e s o l v e n t

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

d i s t ri b u t i o n . S e l e c t i o n o f a n a p p r o p r i a t e l e v e l a n d t y p e o f u l tr a -

s o n i c a t io n a n d d i s p e r s i o n p a r a m e t e r s i s t h e k e y f a c t o r i n o b t a i n -

i ng ne a r - t r u e s i z e d i s t r i bu t i on d a t a . Th e s e l e c t i on o f s o l ve n t s a nd

d i s p e r s a n ts f o r h y d r a u l i c c e m e n t s c a n b e s y s t e m a t i z e d i f s u r f a c e

c h a r g e a n d p H i ~p d a t a a r e a v a i l a b le . I n t h e a b s e n c e o f s u c h d a t a ,

f o u r s ol v e nt s w e r e e v a l u a te d b y u s in g t h e C C R L p o r t la n d c e m e n t

p r o f i c i e nc y s a mp l e . The s i z e d i s t r i bu t i on da t a f r om a l i gh t - s c a t -

t e r i n g d e v i c e i n d i c a t e d t h a t t h e c e m e n t s a m p l e h a s a b i m o d a l

s i z e d i s t r ib u t i o n i r r e sp e c t i v e o f t h e s o t v e n t - d i s p e r s a n t c o m p o s i -

t i o n . H o w e v e r , t h e d a t a f r o m i s o p r o p y l a l c o h o l s h o w e d t h a t t h e

o v e r a l l s i z e d i s t r i b u t i o n w a s f i n e r . I n d e p e n d e n t v e r i f i c a t i o n o f

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

mi c r os c opy is r e qu i r e d t o t e s t t he i r va l i d i t y . A s l i gh t va r i a t i on

w a s o b s e r v e d a t t h e p e a k o f t h e c o a r s e e n d o f th e P S D i n t h e

r e p l ic a t e t e s t s u s in g I P A . I n t h e c a s e o f S e d i s p e r se A - 1 2 , t h i s

t ype o f va r i a t i on wa s ne g l i g i b l e .

C

cD

¢-

I

c-

l j n

{D

0

>

¢ -

C E M E N T I N I P A

1

S a m p l e

I

S a m p l e 2

8 - - -

S a m p l e

6

5

4

. / / i i ,

0

O . 1 . 0 1 0 . 0 1 0 0 . 0

P a r t i c le D i a m e t e r m i c r o n s

FI G.

5--Rep eatabil i ty of s ize distr ibution data by using Horiba LA-500 fo r cemen t in 1PA.



6/6

12 CEMENT, CONCRETE, AND AGGREGATES

11

C EM E NT IN A - 1 2

c-

b. .

¢-

o ~

,

~

O

>

-{3

c

10

9

8

S a m p l e 1

S a m p l e 2

- - . - S a m p l e

.3

7

f.

6 / Z

5 ~

4 ~

3

2

O.1 1 .0 10.0 10 0.0

P o r t ic l e D i o m e t e r m i c r o n s

F I G .

6--Repe atabil i ty of s ize distr ibution data by using H oriba LA-500 fo r cement in Sedisperse A-12.

eferences

[1 ] Al len , T . and Dav ies , R . , Mo dern Aspec ts o f Pa r t ic le S ize Ana l -

ys is ,

Advances in Ceramics

Vol. 21:

Ceramic Powder Science

G. L . Mess ing e t a t . , Eds . , A me r ican Ceramic Socie ty , pp . 72 1-

746.

[2 ] Al len , T . ,

Particle Size Measurement

3 r d e d . , C h a p m a n a n d H a l l ,

New York , 1981 .

[3]

Modern Methods of Particle Size Analysis

H. G. Bar th , Ed . , Wi ley

In te rsc ience , New Y ork , 1984.

[4] Poh l , M. , Se lec t ing a Par t ic le S ize Ana lyzer : Fac to rs to Cons ide r ,

Powder and Bulk Engineering Vol . 4 , N o . 2 , Feb ruary 1990 , pp .

2 6 - 2 9 .

[5 ] Napper , D. H. ,

Polymeric Stabilization of Colloidal Dispersions

Acad emic P ress , Inc . , Lo ndon , 1983 , pp . 18 -30 .

[6] Parfit t , G. D. ,

Dispersion of Powders in Liquids

Chap te rs 1 and

2, Applied Science Publishers, 198t.

[7] Malghan , S . G. and Lu m, L . -S . , 'Fac tors Affec t ing In te r face P rop-

e r t ie s o f S il icon Ni t r ide Powders in Aq ueous En v i ro nm ent , in

Ceramic Powder Science

G. L . Mess ing , e t a l . , Eds . , Amer ican

Ceramic Soc ie ty , Sep temb er 1990.

[8] Ano nym ous , B ran son Son i fe r , Bu l le t in 200-214-082 , B ranson Ul-

t rason ics Corp . , Danbury , CT , 1989 .

[9 ] Samples ob ta ined f rom P ie le r t , J . H. , Cement and Concre te Ref -

e rence L abora to ry , Bu i ld ing Mate r ia l s Div is ion , NIST , Ju ly 1990 .

[10]

Ano nym ous , Ho r iba LA-500 Lase r Dif f rac tion Par t ic le S ize Ana -

lyze r , Bu l le t in HRE-361 0B, Kyo to , Japan , January 1990 .

[11]

Pie le r t , J . H. , Cons t ru c t ion Mate r ia l s Refe rence Labora to r ies a t

N I S T ,

ASTM Standardization News

December 1989 , pp . 40 -44 .


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