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Influence of cementing agents on particle dispersion in Leda clay
NATIONAL RESEARCH COUNCIL CANADA
DIVISION O F BUILDING RESEARCH
T H E I N F L U E N C E O F CEMENTING AGENTS ON P A R T I C L E DISPERSION IN LEDA CLAY
b y E . P e n n e r and G. L o c k e r ANALYZED I n t e r n a l R e p o r t No. 250 of t h e Division of Building R e s e a r c h OTTAWA M a r c h 1962
P R E F A C E
It i s one of t h e r e s p o n s i b i l i t i e s of t h e Division to r e - e x a m i n e established l a b o r a t o r y techniques a s well a s to e s t a b l i s h new o n e s f o r u s e in advancing the s c i e n c e of building. T h e study now r e p o r t e d was t h e r e f o r e a p p r o p r i a t e s i n c e i t was concerned with t h e d i f f e r e n c e s t o b e expected in m e c h a n i c a l a n a l y s e s of s o i l s f o r engineering p u r p o s e s f r o m t h e application of p r e t r e a t m e n t p r o c e d u r e s such a s a r e commonly used in s o i l science.
T h e s e n i o r author i s a g r a d u a t e in a g r i c u l t u r e with s p e c i a l t r a i n i n g i n s o i l s c i e n c e and a r e s e a r c h o f f i c e r with the Soil M e c h a n i c s Section. T h e junior author, a g r a d u a t e in Civil Engineering was
employed on t h i s p r o j e c t a s a s u m m e r a s s i s t a n t .
Ottawa M a r c h 1962
N. B. Hutcheon, A s s i s t a n t D i r e c t o r .
Leda clay, the s o i l u s e d in t h i s study, i s of p o s t - g l a c i a l o r i g i n and i s found extensively a s a s u r f i c i a l deposit along the St. L a w r e n c e and Ottawa R i v e r s and t h e i r t r i b u t a r i e s . Mica, the predominant c l a y m i n e r a l , i s a l s o well r e p r e s e n t e d in t h e s i l t and
sand f r a c t i o n s a c c o r d i n g to a r e c e n t study by Brydon ( 2 ) . F e l d s p a r predominated in the c o a r s e r f r a c t i o n s but o c c u r r e d a l s o in s i g n i f i - cant amounts in the c l a y - s i z e r a n g e . In g e n e r a l , q u a r t z , f e l d s p a r and amphiboles w e r e always r e p r e s e n t e d in the c l a y f r a c t i o n , and c h l o r i t e , v e r m i c u l i t e , m o n t m o r i l l o n i t e and mixed l a y e r e d m i n e r a l s w e r e u s u a l l y p r e s e n t .
Leda c l a y i s u s u a l l y c a l c a r e o u s except i n t h e pedological p r o f i l e developed on t h i s p a r e n t m a t e r i a l ( 2 ) . In m a n y i n s t a n c e s f o s s i l s give it a high c a r b o n a t e content. T o t a l i r o n d e t e r m i n a t i o n s have given values a s high a s 8 p e r cent ( 3 ) and t h e o r g a n i c m a t t e r ,
except n e a r the s u r f a c e , i s known t o b e low, p e r h a p s around 0. 5 p e r cent.
EXPERIMENTAL METHODS AND MATERIALS M a t e r i a l s
T h e Leda clay deposit was s a m p l e d in t h r e e l o c a t i o n s , two within the Ottawa city l i m i t s
-
Sample 100 -6 a t 35 ft and Sample103 f r o m 10 t o 15 ft
-
but s e p a r a t e d by a d i s t a n c e of 10 m i l e s . At h i r d Sample, 116, was taken within the pedological "C" h o r i z o n w h e r e Wesley C r e e k e n t e r s the St. L a w r e n c e R i v e r e a s t of Cornwall, Ontario. T h e s o i l s w e r e p u r p o s e l y s e l e c t e d t o contain different c l a y - s i z e p e r -
centages.
T h e s a m p l e s w e r e remoulded a t t h e i r n a t u r a l m o i s t u r e content ( o r slightly h i g h e r ) with a m e c h a n i c a l m i x e r until a c r e a m y t e x t u r e was obtained. They w e r e s t o r e d in s e a l e d p l a s t i c containers at t h i s m o i s t u r e content until r e q u i r e d for a n a l y s i s . It i s to be noted s p e c i f i c a l l y that the s o i l was not allowed to a i r - d r y a s i s common with s o m e p r o c e d u r e s .
Methods
T h e e x p e r i m e n t a l p r o g r a m contained eight t r e a t m e n t s : for t h r e e , t h e m e c h a n i c a l composition was d e t e r m i n e d by the p i p e t t e method and for five, i t was done by t h e h y d r o m e t e r method. Each
t r e a t m e n t was quadruplicated in o r d e r that the r e s u l t s could b e s t a t i s t i - cally analyzed.
1. DBR h y d r o m e t e r p r o c e d u r e ( s i m i l a r t o t e n t a t i v e ASTM method (1) ).
Modifications t o ASTM method
a ) T h e s o i l was used at i t s n a t u r a l m o i s t u r e content and not in the a i r - d r i e d s t a t e .
b) T h e d i s p e r s i n g agent contained 102 gm of sodium metaphosphate p e r l i t r e of which 50 c c w e r e u s e d p e r s a m p l e . No pH a d j u s t m e n t w a s c a r r i e d out. T h e ASTM method c a l l s f o r t h e addition of sodium
c a r b o n a t e which p r e v e n t s r e v e r s i o n to t h e o r t h o - f o r m 2. P i p e t t e method
a ) S a m e s o i l p r e p a r a t i o n and p r o c e d u r e a s in "1" except s a m p l e s w e r e taken at t h e 1 0 - c m depth f o r the 50-, 20-, 5-, 2 - and 1 - m i c r o n f r a c t i o n s a t the a p p r o p r i a t e t i m e s a s calculated f r o m Stokes' Law f o r s p h e r i c a l p a r t i c l e s .
b) E a c h aliquot consisted of 25 c c u s i n g the Lowy pipette Withdrawal t i m e was about 12 s e c using a falling head of w a t e r technique.
3. P i p e t t e method
-
Bourget ( 4 ) modified t h e method of K i l m e r and Alexander ( 5 ) except a s follows:a ) Mechanical d i s p e r s i o n f o r 15 min in m e c h a n i c a l m i x e r instead of end -over -end s h a k e r .
b) Iron oxides w e r e r e m o v e d by t h e Aguileca and J a c k s o n ( 6 ) method, modified by Brydon ( 7 ) .
c) All washings w e r e done by centrifugation and decantation instead of filtration.
S ~ e c i a l n o t e s on method
i) O r g a n i c m a t t e r and c a r b o n a t e s w e r e r e m o v e d by t h e simultaneous t r e a t m e n t of p e r o x i d e and a c e t i c acid. ii) A d i s p e r s i n g agent p r e p a r e d using 30.6 gm of sodium
metaphosphate and 1 . 2 2 gm of sodium c a r b o n a t e p e r l i t r e . Twenty-five c c of t h i s solution w e r e u s e d p e r s a m p l e .
4. P i p e t t e method
-
s a m e a s "3" except a s follows:with hydrochloric acid in s e p a r a t e operations.
b) The chemical dispersing agent consisted of adjusting pH t o 8 with sodium hydroxide, letting sample stand overnight and re-adjusting i t to 8 before mechanical dispersion.
a ) Organic matter was removed with peroxide. b) Same dispersing agent a s in "3".
6.
Hydrometer method-
s a m e a s "5" except a s follows: a ) Carbonates were removed with hydrochloric acid. 7. Hydrometer method-
s a m e a s"6"
except a s follows:a ) Iron oxides were removed by dithionite method. 8. Hydrometer method
-
s a m e a s "7" except a s follows:a ) Same dispersing agent a s in "1".
RESULTS
The r e s u l t s of the hydrometer method were plotted on semi-log paper with the "percentage finer by weight than a given diameter" on the arithmetic scale, and Stokest equivalent p a r t i c l e diameter on the log scale. Values were read from the best fitting curve for the 1
-,
2-, 5-, 20- and 50-micron p a r t i c l e d i a m e t e r s .T h e s e particle diameters corresponded to the s i z e fractions determined by the pipette method. The results for the treatments were grouped for comparison according t o the b a s i c method employed
-
pipette o r hydrometer-
and a r e shown in Table I .Pipette and Hydrometer Method Comparisons
Table I 1 gives the comparison between the hydrometer and pipette methods f o r s i m i l a r treatments. For all three soils the
clay-size fraction i s S i g n i f i c a ~ t l y higher f o r the hydrometer method than for the pipette method. The 2- to 20-micron fractions a r e quite s i m i l a r . The
>
20-micron fraction was obtained f r o m the difference between the two.AS
might be expected, the>
20 -micron fraction r e s u l t s a r e the r e v e r s e of the clay-size fraction.T r e a t m e n t s Analyzed by the P i p e t t e Method
Results of the t r e a t m e n t s using the pipette method a r e given in Table 111. The essential d i f f e r e n c e s between t r e a t m e n t s
I I ~ I I and 1141f a r e the method of carbonate removal and the chemical
dispersion procedure. In "3". organic m a t t e r and carbonates were removed simultaneously with peroxide and acetic acid; in 114" the two w e r e done s e p a r a t e l y and carbonates w e r e removed with hydrochloric acid. Dispersion in "3" was c a r r i e d out with sodium metaphosphate a f t e r all extraneous ions had been removed following sodium chloride washings. In "4", sufficient sodium hydroxide was added to i n c r e a s e the pH t o 8 instead of the sodium metaphosphate t r e a t m e n t . In 11211, t h e r e was no removal of cementing agents and sodium metaphosphate
was used a s in "1".
The clay-size fraction of treatment "4" i s statistically higher than in t1211 and "3" for a l l t h r e e soils. This i s not s o clear cut for the 2- t o 20-micron fraction. In the fraction
>
20 m i c r o n s , t r e a t m e n t11211 i s higher than "3" and "4". One interpretation of t h e s e r e s u l t s i s that by the r e m o v a l of cementing agents, better dispersion was achieved; an alternative i s that the carbonate or i r o n oxides w e r e in the c o a r s e fraction a s d i s c r e t e p a r t i c l e s and by dissolving t h e s e , the t o t a l solids w e r e reduced. The s a m e weight of clay would then be calculated a s a higher percentage of the total.
T h e r e a r e a l s o s m a l l differences between t r e a t m e n t s "3" and "4" that indicate that the l a t t e r m a y be a slightly m o r e effective method. In some c a s e s the differences a r e l a r g e enough t o b e
statistically significant.
T r e a t m e n t s Analyzed by the Hydrometer Method
Table I V gives the r e s u l t s of the p r e t r e a t m e n t comparisons f o r which the hydrometer method was used to determine the mechanical
composition. ,Treatments 11711 and I18I1 differ only by the amount of dispersant used. In 11811, the amount recommended by ASTM, 50 cc of solution containing 102 gm of sodium metaphosphate, was usedr
this works out t o 5. 1 gm p e r sample. In "7"
,
25 cc of solution containing 30.6 gm of the s a m e dispersing agent w e r e used, according t o theBourget modified method. This gives 0. 612 gm per sample. Statisti- cally both t r e a t m e n t s give the s a m e r e s u l t s .
Comparing r l l l l (no cementing agents removed) with "7" and
"8", the clay-size fraction percentage i s significantly higher f o r the l a t t e r two t r e a t m e n t s in s o i l s a m p l e s 100 -6 and 116; this i s the s a m e r e s u l t obtained f o r a l l soils with the pipette method. With the hydrometer
technique, s o i l s a m p l e 103 shows an anomoly and i s not understood. It can b e s a i d t h a t , in general, t h e r e m o v a l of c a r b o n a t e s , o r g a n i c m a t t e r and f r e e i r o n oxides f o r both t h e pipette and h y d r o m e t e r m e t h o d s r e s u l t s i n a higher c l a y - s i z e p e r c e n t a g e . T h i s is l a r g e l y a r e s u l t of the i r o n oxide r e m o v a l t r e a t m e n t which follows f r o m a c o m p a r i s o n of 11511 and It6f' with 117 1 1 and 11811.
Sample 100-6 shows no effect of o r g a n i c m a t t e r r e m o v a l
in "5" and for both organic m a t t e r and c a r b o n a t e r e m o v a l a s in "6".
In
s a m p l e 103, t h e r e a r e s o m e m i s s i n g r e s u l t s and i n s o i l 116 t h e r e a r e s m a l l but s t a t i s t i c a l l y significant differences r e s u l t i n g f r o m o r g a n i c m a t t e r r e m o v a l . T h i s was to b e expected s i n c e t h e o r g a n i c m a t t e r content was considerably higher in t h i s s o i l on t h e b a s i s of v i s u a l inspection.DISCUSSION AND CONCLUSION
F r o m t h e few Leda clay s a m p l e s studied, t h e s e r e s u l t s
a p p e a r t o indicate a consistently higher c l a y - s i z e f r a c t i o n when analyzed by t h e h y d r o m e t e r method a s c o m p a r e d t o the pipette method. T h e r e i s of c o u r s e no definite way of knowing f r o m t h i s study which gives t h e c o r r e c t a n s w e r . In any c a s e , t h e d i f f e r e n c e s ( 3 to 7 p e r cent) a r e p r o b a b l y not of any g r e a t i m p o r t a n c e in c l a s s i f i c a t i o n t e s t s f o r s o i l engineering. F o r c l a y m i n e r a l s t u d i e s , however, t h e conclusion might b e different.
T h e r e a p p e a r t o b e s o m e effects f r o m the r e m o v a l of
o r g a n i c m a t t e r and c a r b o n a t e s in s o i l 116, but m u c h m o r e evident a r e t h e higher c l a y - s i z e p e r c e n t a g e s when f r e e i r o n oxide r e m o v a l i s
c a r r i e d out a s p a r t of t h e p r e t r e a t m e n t p r o c e d u r e . T h e r e s u l t s f r o m both t h e pipette method ( T a b l e 111) and h y d r o m e t e r method ( T a b l e I V )
show i t t o be s t a t i s t i c a l l y significant. T h e d i f f e r e n c e s r a n g e f r o m 4 to 7 p e r cent - not l a r g e enough t o w a r r a n t any significant change in t h e p r e s e n t DBR h y d r o m e t e r method for t h e m e c h a n i c a l a n a l y s e s
p r o c e d u r e f o r Leda clay, provided t h e s o i l i s not e x c e s s i v e l y f o s s i l i f e r o u s and i s taken well below t h e pedological A and B h o r i z o n s .
It should b e noted t h a t s o m e s t a t i s t i c a l l y significant e f f e c t s f r o m t h e r e m o v a l of cementing a g e n t s have been shown, but on t h e b a s i s of t h i s work, t h e i n c r e a s e d c l a y - s i z e p e r c e n t a g e s f r o m t h e s e p r e t r e a t m e n t s cannot b e f i r m l y a s s i g n e d t o t h e r e l e a s e of s e p a r a t e particles f r o m a g g r e g a t e s o r t o a reduced t o t a l s o l i d s by t h e solution
It i s a l s o n e c e s s a r y t o d r a w attention to t h e r e a s o n for doing c l a s s i f i c a t i o n t e s t s in s o i l engineering. T h i s i s mainly t o c h a r a c t e r i z e the behaviour of the soil. If a g g r e g a t e s of p a r t i c l e s existing a s s e p a r a t e entities in n a t u r a l s o i l influence the s o i l
p r o p e r t i e s in much the s a m e way a s do solid p a r t i c l e s of equal s i z e , it i s r e a s o n a b l e that breaking down t h e s e a g g r e g a t e s i s not d e s i r a b l e . T h i s i s p a r t l y achieved by m e c h a n i c a l d i s p e r s i o n which i s always a p a r t of the a n a l y s i s . T h e r e i s a need, t h e r e f o r e , for r'urther
investigations.
REFERENCES
I . A m e r i c a n Society for T e s t i n g and M a t e r i a l s , P r o c e d u r e s f o r T e s t i n g Soils, ASTM designation D-1140-54T. A p r i l 1958. 2 . Brydon, J . E . and L. M. P a t r y . Mineralogy of Champlain Sea
Sediments and a Rideau Clay P r o f i l e . Canadian J o u r n a l of Soil Science, Vol. 41, p. 169-181, J u n e 1961.
3. B u r n , K. N. P r i v a t e communication. 4. Bour get., S. J. P r i v a t e communication.
5. K i l m e r , V. J. and L. T . Alexander. Methods of Making ~ e c h a n i c a l Analyses of Soil Science, Vol. 68, p. 15-24, J u l y 1949.
6. Aguilera, N. H. and M. L. J a c k s o n . Iron Oxide R e m o v a l f r o m Soils and Clays. P r o c e e d i n g s , Soil Science Society of A m e r i c a , Vol. 17, p. 354-360, 1953.
TABLE I
RESUME O F HYDROMETER AND P I P E T T E METHODS
P i p e t t e M
-
2-
3-
4 S a m p l e 100 -6-
<
1 3 5 . 6 * 38. 5 3 6 . 8 < 2 4 2 . 0 4 7 . 1 4 6 . 0 ( 5 53. 1 56. 8 57. 5 ( 2 0 66.2 6 8 . 2 7 0 . 0 ( 5 0 7 6 . 7 7 6 . 2 7 5 . 6 T r e a t m e n t H y d r o m e t e r 5-
-
6-
7-
8-
1 , 3 9 . 1 3 8 . 8 4 7 . 5 4 4 . 8 3 9 . 5 4 7 . 3 4 7 . 0 5 4 . 1 5 2 . 9 4 7 . 0 57. 5 56.9 62. 5 61. 1 5 6 . 6 7 0 . 4 6 9 . 5 73. 5 7 1 . 3 6 9 . 9 7 6 . 4 76. 1 7 9 . 8 7 8 . 6 79. 5 S a m p l e 1 0 3 < 1 5 9 . 9 6 1 . 2 6 4 . 4 t 2 7 1 . 0 7 4 . 4 7 7 . 8 < 5 8 6 . 0 8 6 . 5 9 2 . 0 ( 2 0 93. 5 9 4 . 8 9 8 . 8 ( 5 0 9 6 . 6 9 5 . 8 9 9 . 8 S a m p l e 1 16 ( 1 41. 3 47. 1 5 0 . 2 < 2 5 2 . 6 5 9 . 5 6 1 . 9 ( 5 7 6 . 0 8 0 . 8 8 3 . 6<
20 9 2 . 5 9 6 . 1 9 8 . 8 ( 5 0 9 4 . 6 9 6 . 4 9 9 . 9-
58. 5 6 6 . 1 6 3 . 5 6 2 . 9-
7 1 . 5 7 7 . 8 7 6 . 1 7 5 . 3-
84. 5 9 0 . 9 89. 0 8 9 . 8-
94. 4 9 7 . 6 9 7 . 0 9 8 . 6-
95. 0 9 8 . 9 98. 3 99. 3 46. 8 47. 3 51. 8 55. 3 46. 1 61. 3 60. 8 64. 8 65. 5 5 7 . 6 8 0 . 9 79. 1 81. 6 8 2 . 9 79. 3 96. 1 9 4 . 9 97. 1 97. 5 98. 0 97. 1 96. 2 9 7 . 4 98. 1 99. 3TABLE I 1
COMPARISON BETWEEN P I P E T T E AND HYDROMETER METHODS WITH SIMILAR SOIL PRETREATMENTS
Hydrometer Pipette Hydrometer
Difference Pipette Difference LSD
**
M Treatment 1 Treatment 2 Treatment 7 Treatment 3 (0. 05)
Soil 100 -6
Soil 103
*
Average of four individual determinations in p e r cent of total soil weight.TABLE I 1 1 P I P E T T E METHOD RESULT M
-
2-
3 4 - LSD** (0. 05) Soil 100-6*
4
2 4 2 . 0 4 7 . 1 46. 0 2 . 2 Soil 103 Soil 1 16*
A v e r a g e of four individual d e t e r m i n a t i o n s in p e r cent of t o t a l s o i l weight.T A B L E I V
HYDROMETER METHOD RESULT
M d 1
