the influence of cation exchange and electrolyte
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Scholars' Mine Scholars' Mine
Masters Theses Student Theses and Dissertations
1965
The influence of cation exchange and electrolyte concentrations The influence of cation exchange and electrolyte concentrations
upon the Atterberg limits upon the Atterberg limits
Kent J. Schwieger
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Part of the Civil Engineering Commons
Department: Department:
Recommended Citation Recommended Citation Schwieger, Kent J., "The influence of cation exchange and electrolyte concentrations upon the Atterberg limits" (1965). Masters Theses. 5721. https://scholarsmine.mst.edu/masters_theses/5721
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ii
ABSTRACT
The object of this investigation is to correlate relationships
between cation exchange capacity, clay content, and type and
concentration of the exchangeable cations upon the Atterberg limits of
a soil. Synthetic soils consisting of loessial silt and either an
illitic natural deposit, bentonite, ball clay, or kaolin clay were
used.
As the percent clay fraction was increased the cation exchange
capacity, liquid and plastic limits and plasticity index increased
linearly in the clay range. Results also suggested a linear
relationship between the liquid and plastic limits and the cation
exchange capacity of soils of one hundred percent clay fraction.
ACKNOWLEDGMENT
The author wishes to express his appreciation to Professor
John Be Heagler, J r . for his guidance and counsel during the course
of this study. Thanks are also given to Dr. Thomas Se Fry for his
comments in the preparation of this paper.
iii
iv
TABLE OF CONTENTS
PAGE
ABSTRA.CT •••••• •• • • ••••• • ••••• ••• •• ••••••••••••• • •••• ••••••••• •• •• ii
A CKN <:M'LE l)(;l-1ENT • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • iii
LIST OF ILLUSTRA.TIONS. • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • v
I • INTRODUCTION. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • 1
II • REVIEW OF LITERA.TURE • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • 3
III • PROCEDlJR..E • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 10
IV . DISCUSSION OF RESULTS • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 15
V. CONCLUSIONS AND RECOMMENDATIONS.......... . . ..... .......... 37
BIBLIOORA.PliY... ... ... .. ....... .. . ... .. ........ . .. ......... .. . .... 41
VITA • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 4 3
v
LIST OF ILLUSTRATIONS
FIGURE PAGE
1 CRYSTAL LATTICE OF MONTMORILLONITE... . ...... . ...... .. . ... . 5
2 CRYSTAL LATTICE OF KAOLIN. . • . . . . • . • • • . . . . • . . . . . . . . . . . . . . . . 5
3 DISPERSED sYSTEM. • • . • . . . . . . . . . . . . . . . • . . . . . • . . . . . . . . . . . . . . . 5
4 FLOCCULATED SYSTEM . • • . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . 5
5 TITRATION CURVE FOR DETERMINATION OF HYDROGEN IONS ADSORBED . • • • • • • • • • . • . • • • • • • • • • • . • • • • • . • • • • • • . • • • • . • • • • . • • • 12
6 TITRATION CURVE FOR DETERMINATION OF BASE IONS ADSORBED. . . 12
7 PLASTICITY INDEX AND CATION EXCHANGE CAPACITY OF KAOLIN.. . 18
8 PLASTICITY INDEX AND CATION EXCHANGE CAPACITY OF BALL CLAY 19
9 PLASTICITY INDEX AND CATION EXCHANGE CAPACITY OF ONYX CAVE CLAY......... .... . . .. . .... . . . ..... . ...... . . ... . ........ . .. 20
10 PLASTICITY INDEX AND CATION EXCHANGE CAPACITY OF BENTONITE 21
11 ATTERBERG LIMITS OF KAOLIN FOR VARYING PERCENTAGES OF ADDITIVE . . . . . . . . . . . . . . . . . . • • . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . 2 2
12 ATTERBERG LIMITS OF BALL CLAY FOR VARYING PERCENTAGES OF ADDITIVE . . . . . . . • . . . . . . . . . . . • . . • . . . . . . . . . . . . . . . . . . . • . . . . . • . 2 2
13 ATTERBERG LIMITS OF ONYX CAVE CLAY FOR VARYING PERCENTAGES OF ADDITIVE . . • • . . . • • . . . . . . . . . • . . . . . • . . . . . . . . . . . . • . . . . . . • . . 22
14 ATTERBERG LIMITS OF BENTONITE FOR VARYING PERCENTAGES OF ADDITIVE . . • . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . 2 2
15 LIQUID AND PLASTIC LIMITS OF KAOLIN , 8% ADDITIVE . . •. . ..••. 26
16 LIQUID AND PLASTIC LIMITS OF BALL CLAY, 8% ADDITIVE . •• •... 27
17 LIQUID AND PLASTIC LIMITS OF ONYX CAVE CLAY, 6%-4% ADDITIVE.... .... .... ... . . .. . .. . .. .. .. . ........ ...... 28
18 LIQUID AND PLASTIC LIMITS OF ONYX CAVE CLAY, 2% ADDITIVE.. 29
19 LIQUID AND PLASTIC LIMITS OF BENTONITE , 4% ADDITIVE . .... .. 30
20 PLASTIC LIMIT VERSUS CLAY CONTENT , UNALTERED ..••••.••• . .. . 31
21 LIQUID LIMIT VERSUS CLAY CONTENT , UNALTERED .•. . .. . • . • . • .. • 32
FIGURE
22
23
24
25
PLASTCITY INDEX VERSUS CLAY CONTENT , UNALTERED ... . .•.....
LIQUID AND PLASTI C LIMITS OF BENTONITE, UNALTERED .•.. . . . .
CATION EXCHANGE CAPACITY VERSUS LIQUID AND PLASTIC LIMITS
GRAIN- SI ZE DI STRI BUTION CURVE ...•.•••.••••...•.. .. . . .... .
vi
PAGE
33
35
36
40
I. INTRODUCTION
The physico-chemical properties of soils are of great interest in
attempting to understand soil behavior as related to its engineering
properties. The amount and characteristics of the clay fraction present
in a soil is generally the chief factor influencing the physical be-
havior of a clay soil system. Previous investigations have indicated
general linear relationships between the percent clay fraction and the
Aeterberg limits and cation exchange capacity.(!) The liquid and
plastic limits are determined by the surface charge-density of the clay
mineral, the thickness of the diffuse double layer which decreases with
increasing electrolyte concentration and increasing cation valence, and
the existance of the face-to-edge orientation of clay particles favored
by reduced pH. Similar factors influence the cation exchange capacity,
thus correlation of the Atterberg limits with the cation exchange
capacity of a known percentage clay fraction in a soil system may be
expected.
The liquid and plastic limit test developed by Atterberg are
simple to conduct and have experienced wide acceptance as a means of
indicating engineering properties of plastic soils. They are combined
with grain-size analysis to form various classification systems which
are invaluable as design criteria.
Wide variations in values obtained for the Atterberg limits are
common among even experienced laboratory technicians due to types of
equipment and individual testing techniques. Discrepancies in liquid
limit values arising from test procedures prescribed by ASTM may be due
to equipment such as type of grooving tool, resiliency of the rubber
base of the liquid limit apparatus, the type and size of rubber feet,
the condition of the surface inside the cup, the type of rest or table
and the location of the liquid limit machine on it.(2) However,
deviations may be due to the laboratory technician as effected by the
height of fall, the weight of soil in the cup, curing time, and the
method of proceeding from the wet to the dry soil state.
Repetitive cycles of wetting and drying may cause the values of
the liquid limit to vary as much as thirty percent.()) The plastic
limit is also subject to fluctuations in values obtained due to the
procedures used by the laboratory technician. Individual techniques
vary in the pressure exerted while rolling the sample, judgment of the
one-eighth inch thread diameter, and speed of rolling. Wetting and
drying cycles will affect the plastic limit to a lesser degree than
the liquid limit.
It was reported by Davidson and Sheeler(l) and Havens(4 ) and
2
indicated by this thesis that the liquid and plastic limit values are
a function of the amount of clay fraction, the type of clay minerals
and their related cation exchange capacities, the type and concen
tration of the exchangeable ions, as well as the grain size distribution
and shape of the soil particles.
This thesis is an attempt at correlating the liquid and plastic
limits and resulting plasticity index with the amount and type of clay
fraction present, cation exchange capacity, and the type and
concentration of the exchangeable cations in the soil system.
II. REVIEW OF LITERATURE
It has been found that the engineering properties are affected by
the type and amount of c lay fraction as wel l as the type of adsorbed
cation on the clay surfaces . Davidson and Sheeler(!) observed that
the liquid and plastic limits generally increased linearly with in
creasing clay content. They also reported that the cation exchange
capacity is a similar linear function of the percent clay content .
I nvestigations carried out by Seed(S) with inorganic synthetic soils
indicate linear relationships between the liquid limit and the percent
c lay content exist above ten percent for clays of high activity and
above forty percent for clays of l ow activity. Linearity was also
found to exist between the plastic limits and percent c l ay content in
mixtures with greater than twenty percent clay fraction. A thorough
understanding of the effects of the clay fraction and colloidal sized
particles in a soil system necessitates a review of the present con-
cepts of clay mineralogy.
Montmorillonite, illite, and kaolin were the three types of clay
minerals used in this investigation. The sheetlike crystal s tructure
3
of montmorillonite clay is constructed of three layers. Two tetrahedral
silica layers are stacked with a third octahedral alumina layer between
them. The typical crystal lattice of the montmorillonite family is
shown in Figure 1. Mg++, Fe++, or similar bivalent ions are often
isomorphically substituted for some of the trivalent aluminum ions
in the octahedral layer. Similarly potassium or alumina may be found
in place of silica in the tetrahedral layer. These isomorphic
substitutions within the crystal structure result in a net negative
charge and the resulting deficiency of positive ions i s satisfied by
4
adsorbed cations and associated water molecules (due to the dipolar
nature of the water molecules) on the basal surfaces of the mineral.
Both positive and negative charges occur due to broken bonds along the
edges of the particles. The number of these charges is proportional
to the diameter to thickness ratio of the crystal . In the
montmorillonite crystals these charges will be of less importance
than those due to isomorphic substitutions.
The order of preference of the different cations to be adsorbed on
the basal surface of the clay crystal may generally be predicted from
the Hofmeister series: H+ Al+++ NH + 4
L.+ l. • !t is to be noted with the exception of hydrogen, ions of
higher valence and greater atomic weight are preferred . Hemholtz
proposed the theory that the net negative charge surrounding the
particle was neutralized by a rigid positive layer of cations . The
validity of Hemholtz 1 s rigid double layer theory has been greatly
disputed. Gouy-Freundlich 1 s diffuse double layer theory proposes
that the double layer is not held in rigid contact with the particle
surface but rather extends loosely throughout a liquid media or
"hydrospheretr surrounding the particle (Figure 2). Thus the term clay
"micelle" consists of the clay crystal and its surrounding adsorbed
diffuse layer. !t is believed the attractive forces of the crystal for
the adsorbed cations in the micelle varies exponentially with the
distance from the crystal surface. This decrease in attraction has been
designated as the zeta potential and is expressed by the following
equation:
z == 4 1T Qd Ak
Silica
tetrahedral layer
Alumina
octahedral layer
Silica
tetrahedral layer
5
0 Oxygen
(Q) Silicon
@ Hydroxyl
• Aluminum
FIGURE 1. CRYSTAL LATTICE OF MONTMORILLONITE
FIGURE 2 CRYSTAL LATTICE OF KAOLIN
Alumina
octahedral layer
Silica
tetrahedral layer
FIGURE 3 DISPERSED SYSTEM
FIGURE 4 FLOCCULATED SYSTEM
where
Q/A = the charge density of the surface
d = the thickness of the diffuse double layer
k = the dielectric constant of the media.
6
Both the charge density and dielectric constant are slightly variable
but the thickness of the diffuse double layer is the significant factor
which can be altered to influence the zeta potential. The zeta
potential is an indication of the energy state of the clay micelle.
Most engineering properties can be related to the energy state of the
soil media. As the soil is changed from a high to a low energy state
by exchanging cations in the clay micelle the coefficient of friction,
permeability, and friability increase while the plasticity index,
cohesion, density, shrinkage and swell decrease. As can be noted from
the Hofmeister series, ions of smaller ionic radius and higher valence
are preferred in the diffuse double layer surrounding the clay
crystal(6) and will contribute to a decrease in the zeta potential . If
a low zeta potential is desired to alter the engineering properties of
a soil, an introduction of an excess of the required cation will en-
hance the cation exchange. Cations such as sodium and potassium are
large and monovalent in nature and increase the thickness of the diffuse
double layer of the micelle. This results in a higher zeta potential of
the clay micelle. High repulsive forces result between neighboring
micelles. The micelles tend to orient themselves in a face to face
configuration or dispersed state (Figure 3). As drying of the clay
system begins to force the micelles closer together Van der Waal-London
attractive forces increase until they become the prevailing force
between micelles. This causes the high relative values for dry strength
of a high energy clay in the dispersed state. The parallelism
7
of the micelles suggests their ability to slide over one another and
one would expect a low angle of friction . In contrast a low zeta
potential results in low repulsive forces between the micelles.
Attraction between the positive charges at broken edges and the negative
charges on the crystal surface yield an edge to face cardhouse effect
in random orientation (Figure 4). This flocculated, low energy state
has a high degree of interlock among the micelles and would indicate
that a higher angle of friction should be expected. Van Olphen(]) found
the ratios of diameter to thickness to be as high as 400:1 in mont -
morillonite. Thus the adsorbative potential of exchangeable cations
and additional water molecules (due to the dipolar nature of water)
would be high. The associated water ranging as high as six molecules
thick explains the high degree of swell characterized by this type of
clay.< 3)
The ability of a soil to adsorb or exchange cations in its diffuse
double layer is measured by its cation exchange capacity expressed in
milliequivalents per 100 gm dry soil. A milliequivalent is one
milligram of hydrogen or that portion of an ion that will combine with
or replace one milligram of hydrogen. The cation exchange capacity is
a function of the charge density of the crystal surface as well as the
number of broken bonds at the edges of the crystal lattice. Thus the
ability to alter the zeta potential of a clay is directly related to
its cation exchange capacity . A high cation exchange capacity is found
in montmorillonite due to its particle diameter to thickness ratio
brought about by weak bonding between neighboring silica sheets . (3
)
Illites are of crystal structure similar to that of montmoril l onite
differing chiefly in that neighboring silica layers are bonded more
strongly by potassium ions which reduces cleavage in the lattice
8
structures. Resulting particle diameter to thickness ratios of about
50:1( 7) suggest increased influence of positive charges due to broken
bonds at the edge of the particle. The resulting charges at the
particle edge may be of greater significance than the net charge of the
basal surfaces. This reduction in total net charge is reflected by its
lower cation exchange capacity when compared to that of montmorillonite.
Typical kaolin crystals are composed of one tetrahedral silica
sheet bonded to an octahedral alumina sheet to form an electrically
neutral layer. Kaolin clays are usually found in hexagonal shaped
plates of diameter to thickness ratios of 10:1 to 20:1. Charges along
the edges of the particle may result in an electrically nonneutral
particle but the low overall charge on the particle would suggest low
cation exchange capacity.
Grim(8) suggests the following cation exchange capacities:
kaolin 3-15 m.e./100 gm. soil, illite 10-40 m.e./100 gm. soil, and
montmorillonite 80-150 m.e./100 gm. soil. Grim(6
) reported that
particle size appeared to be much more significant in soils of low
cation exchange capacity than in high cation exchange capacities.
In a soil system at the liquid limit, free water surrounds the
clay micelles and gives only slight deterance to relative motion
between the particles. Thus structure or the micelle orientation has
significant effects on the values obtained for the liquid limit. As
evaporation of the free water continues the micelles are forced close
together. Repulsion forces increase and prevail over the Vander Waal-
London forces of attraction and particle orientation would be ov even
greater influence at the plastic limit. Grim(6
) asserted that bonding
between particles was dependent upon geometric fit, hydration tendencies,
and valency of available exchangeable cations. Baver(9) reported the
physico-chemical behavior of clays to be a function of the surface
"active Ions." Davidson and Sheller(l) observed an apparent linear
9
relationship between the liquid and plastic limits and cation exchange .
Cation exchange capacity consisting of both the exchangeable bases
d h bl h d b d . d b th d (10,11,12) an exc angea e y rogens may e eterm1ne y numerous me o s.
Generally they require leaching a soil sample with 1.0 N ammonium
acetate and after a period of 4 to 24 hours determine the amount of
exchangeable cations by direct nesslerization and use of a centrifuge
and spectrophotometer, potentiometric titration or other analytical
procedures. A simplified method of cation exchange determination
originated by Brown(lZ) utilizes a minimum amount of equipment and
technical laboratory skill. Results which are comparable(l3
) with
other methods are much quicker and simpler to obtain.
10
III. PROCEDURE
The synthetic soils used in t esting were made up of three
commercial clays and the clay fraction removed from a natural soil
deposit. Wyoming Bentonite, a member of the montmorilloni te fami ly,
Georgia Kaolin, and Ball Clay from old mine No. 4 whose chi ef
constituents are of the kaolin group, were obtained from the Ceramics
Department at the University of Missouri at Rolla. The clay frac tion
removed from the natural deposit i s termed Onyx Cave Clay and was
found to contain a 76 percent clay frac tion as determined by hydrometer
analysis( l4
) (Figure 25) and which clay fraction believed to be pre -
dominately i llite as de t ermined from X-ray analysis. The Onyx Cave
clay was air dried , crushed, and sieved through a number 100 s ieve
before used in testing.
The silt used for testing as the non-plastic fines in the
synthetic soils was obtained from a Peorian l oessia l deposit of the
Wisconsin stage along u.s. Highway 54 two miles north of Jefferson
City, Mis souri. The Loess was placed in solution in distilled water, a
dispersent added to promote co lloida l suspension of the clay fract i on
present which was then extr acted observing Stokes law concerning the
differentia l rate of settlement of particles in s uspension as a
function of their size and density . Repeated cycl es were used to
achieve the lowes t clay fraction remaining in the silt as possible.
The silt was then washed repeatedly in distilled wa t er to remove excess
dispersent associated with the si lt particles. The c l ay fraction is
defined as the effective spherical particle diameter finer than .002 mm
according to the textural classification systems of the Massachusetts
Institute of Technology , Atterberg, the U. s. Department of Agriculture
11
and the International Society of Soil Science.(lS , l 6) It can be seen
graphically from Figure 25 the grain size distribution curve determined
. (14) . . by hydrometer analys~s, that the processed s~lt conta~ned less than
a two percent clay fraction.
Determinations of the cation exchange capacity for the various soil
mixtures were made utilizing the method proposed by Brown~ 12 ) Equipment
and material requirements were minimal and included standard normal
acetic acid, neutral normal ammonium acetate , a Beckman Zeromatic pH
meter equipped with glass electrodes capable of detecting differences
of 0.02 pH . As Erlenmeyer flasks with stoppers of relative capacities
of 50 ml were not available ten 400 ml beakers with glass stirring rods
were substituted. Determinations of exchangeable hydrogen according to
Brown can be made by placing 2.5 gms. of soil in a 50 ml Erlenmeyer
flask, adding 25 ml of neutral normal ammonium acetate, stoppering and
shaking . The mixture is allowed to stand for one hour with occasional
shaking, the pH is then determined and the milliequivalents of
exchangeable hydrogen per 100 gms of soil can be found directly from
Figure s.<13) The total exchangeable bases are determined by mixing
2.5 gms of soil and 25 ml of 1.0 normal acetic acid, again allowing to
stand for one hour with occasional agitation. The pH is then deter-
mined and the milliequivalents of exchangeable bases per 100 gms of
soil can be read directly from Figure 6. Figure 5 was obtained by
potentiometric titration of 100 ml of neutral normal ammonium acetate
buffer with 0.2 normal acetic acid. The number of milliequivalentsa of
acetic acid required to lower the pH of the ammonium acetate solution
was then multiplied by 10 to give the quantity required per 1000 ml.
In the use of this curve for the determination of exchangeable hydrogen
it is assumed that the reaction is complete and that an equal amount of
pH
pH
7.0 ~
6.8
6.6
6.2
6.0 0
"" I'-I
" " '~'--.. ..........
.......... .......... r--...
r--1'-.. 1-. r-t-
8 12 16 20 24 28 3 2 36
Milliequivalents of Hydrogen/100 Grams of Soil
HYDROGEN IONS ADSORBED
Figure 5.
3.00 ~~--1-
I.-r-~
L,....--~ 2. 00
v ......
/ v 2.60
,/"' v v v,
2.~ 0 2 6 8 10 12 1~ 16 lB .:20
Milliequivalents of Bases/100 Grams of Soil
BASE IONS ADSO RBED
Figure~
12
hydrogen ions, whether combined with the acetic acid or involved in
ion exchange with the soil, will cause an equal change in the pH of
1000 ml of neutral normal ammonium acetate. The titration curve of
13
Figure 6 indicates the change in pH of 1000 ml of normal acetic acid
for each mil l iequivalent of ammonium hydroxide added, thus the pH of a
mixture of 100 gms of soi l and 1000 ml of normal acetic acid indicates
the milliequivalents of exchangeable bases per 100 gms of soil.
As the curves of both Figure 5 and 6 are based on a 1 to 10
ratio of soil to so lute, larger volumes of 100 ml solute were required
d~e to the replacement of 400 ml beakers for the SO ml Erlenmeyer
flasks . For soils of high cation exchange capacities difficulty arises
in obtaining accurate values at those portions of the curves approaching
a horizontal slope . By using a 1 to 20 ratio of soil to solute and
doubling the values obtained graphically from Figures 5 and 6 high
values of cation exchange capacity can be determined.(l3) Difficulty
~as encountered in obtaining comp lete reaction between bentonite and
acetic acid . Vigorous stirring was used and the so lution allowed to
set 12 hours before determining the pH .
Before and after determinations were made, the pH meter was checked
at the initial pH of the buffer so lution with necessary adjustments
made for temperature corrections . Values obtained by Brown( l2
) and
Davidson(!)) using this method were analogous to determinations made
bY other conventiona l methods.
All values of liquid limits were determined following ASTM Standard
D423- 6l(l]) with the exception of proceeding from the wet to the dry
state and substituting a flat type Casagrande grooving tool for use
~tth all but the kaolin mixtures . Flow curves were plotted on semi -
logarithmic graphs with water contents as ordinates on the arithmetical
14
scale and the number of drops or shocks as the abscissae on the
l ogarithmic scale. Straight lines were then drawn through four points
determined from each sample . P l astic limits of the various soil
mixtures were determined as required by ASTM Standard D424-59.( l B)
Before varying the clay content of the soil samples the effects
of varying the concentration of exchangeable cations on the liquid and
plastic l imit values of the test samples composed of 100% c l ay content
were determined. An analytical grade of calcium hydroxide was used
as the f l occulant and sodium hexametaphosphate was employed as the
dispersing agent. The addition of electrolytes in the kao l in, bentonite,
and bal l clay ~ere made in 2 percent increments up to 8 percent by
weight of clay present . Additives up to 6 percent by weight were
combined with illite . Water was then mixed into the soil samples
until the moisture content was above the l iquid limit . The samples
were covered so as to maint ain this moisture level and were then
a l lowed to cure for 12 t o 16 hours. The liquid and plastic limit
values for the various percentages of additives are plotted as
shown in Figures 11, 12, 13 and 14 . Peak values, within practicability,
of percentages of additives causing significant deviations in the
liquid and plastic limit values from those of the natural state were
determined . Samples were then mixed adding the previously determined
percentages of dispersent and flocculent to varying percentages of clay
content. Silt and clay fraction mixtures without additives were used
as comparative values in investigating the liquid and pl astic limit
va l ues of soil systems in the flocculated and dispersed state . In
all mi xtures the clay content was varied in twenty percent increments .
15
IV. DISCUSSION OF RESULTS
The relationship between the Atterberg limits and varying per-
centages of unaltered clay in clay-silt mixtures is illustrated
graphically in Figures 20, 21, 22, 23. The plastic and liquid limits
appear to be directly proportional to the percent clay content in the
upper clay range. The upper clay range is the range where the colloidal
nature of the clay dominates the characteristics of the clay-silt
mixture. This condition occurs where silt particles in a matrix of clay
colloids are not allowed grain-to-grain contact. When grain-to-grain
contact of the silt particles begins to increase at lower percentages
of clay fraction a transition into the silt range occurs where the
properties of the silt predominate. Casagrande showed that the liquid
limit test is analogous to a shear test on the soil and that the
liquid limit test may roughly be defined as that water content at which
2 (19) the soil has a shear strength of 25 gm/cm . L. E. Norman suggested
lower values of about 20 gm/cm2
.C20) The clay range was found to
extend to a lower value of percent clay content for the liquid limit
than for the plastic limit. The shearing resistance of the soil at the
plastic limit is approximately 10 times that at the liquid limit than for
the plastic limit. The lower clay range of the liquid limit curve as
compared to the plastic limit curve is a function of angularity, grading,
void ratio, and density of the silt and clay particles.C2l) After con-
sidering the effects of negative pore water pressure and internal
2 friction it was found that at the liquid limit the 20 to 25 gm/cm shear
. (22) strength is dependent chiefly on the net forces between clay part1cles.
16
Particles with greater surface area and higher surface activity require
greater spacing between particles to maintain a 20 to 25 gm/cm2 shear
strength and thus have a correspondingly higher liquid limit . The
plate shaped Bentonite particles of a diameter to thickness ratio of
around 400:1 would be expected to have a higher liquid limit than
ill ite with a 50: 1 diameter to the thickness ratio or kaolin with a
ratio of 10;1 to 20:1. The clay fraction will determine the liquid and
plastic limit characteristics of the soil mixture when the clay fraction
present is more than sufficient to fill the voids in the non- clay
fraction . The non- clay fraction possesses a plastic limit which may
have a higher value than points on the lower portion of the clay
range and a smooth transition curve from the clay to the silt range
would be expected. The s l ope of the plasticity index versus clay
content curve represents the activity coefficient K of the c l ay fraction
where the activity coefficient is determined from the equation
K = Plasticity I ndex. Clay content (%)
The activity coefficient is determined by the plastic and liquid limits
and is a function of the surface area and activity of the clay fraction.
Results of cation exchange capacity determinations on soil
mixtures of varying clay content are shown in Figures 7, 8, 9 and 10
where the abcissa is the cation exchange capacity expressed as
mi lliequivalents per 100 grams of soil. The plasticity index is also
shown for dispersed, flocculated and unaltered mixtures. Linear
relationships between the cation exchange capacity and the plasticity
index were no t found to exist although it was generally found that
soils of higher cation exchange capacity resul ted in higher va l ues for
the pl as t icity index which can be understood as both ar e a function of
17
the surface area and activity of the soil particles. Thus the low
particle diameter to thickness ratio of kaolin explains its low values
of cation exchange capacity and plasticity index. Correspondingly the
higher surface area and activity of bentonite explains its high cation
exchange capacity and plasticity index.
The effects of increasing percentages of additives on the liquid
and plastic limits and resulting plasticity index for the clay fraction
are shown in Figures 11, 12, 13 and 14 where the ordinate represents
the percent moisture and the abcissas the percentages of additives.
It can be seen that the higher the cation exchange and plasticity
index of the unaltered soil the greater the effect of cation substitution
upon its physical properties. As the concentration of calcium ions
used as the flocculating agent was increased in the bentonite and
illitic Onyx Cave clay the plastic limit was observed to increase
while the liquid limit decreased . Due to the higher valence and
smaller radii of calcium ions the thickness of the micelle surrounding
the clay particle would be expected to decrease in the flocculated soil.
Thus the use of calcium ions as flocculents is expected to de
crease the value of the liquid limit . ()) This was experienced in clays
of higher cation exchange capacities, as bentonite and illitic Onyx Cave
clay but not so in kaolin and ball clay of low cation exchange capacity.
Upon alteration of the exchangeab le cation the thickness of the outer
diffuse layer of the clay micelle decreases with the addition of calcium
ions and increases with the substitution of sodium ions due to the
larger effective radius and roonovalence of the sodium ion . The thickness
of the double layer varies inversely as the square root of the
concentration of adsorbed ions in the diffuse layer, and inversely as
~ .. t l:zl
~ 0
j 0
100
80
,
•' ,
60 1- ,/'
40
20
' I I I
I I I I
•
6% Dispersent ~ ~
\..
'
Plasticity Index and Cation Exchange Capacity of Ka@lin
Plasticity Index
Cation Exchange Capacity
FIGURE 7 0 __.J
10 20 30 40 50 60
PLAST~CITY INDEX, %AND CEC, rn.G,/100 gms. SOIL
...... 00
10
8
~
" 6 ~ r.x1
~ C,)
g C,) 4
2
lp
10 20
' Flocculent ~
'----- Unaltered ----
8% Dispersent
30
~
/-
40 so PLASTICITY INDEX,% AND CEC, m.e./100 gms. SOIL
Plasticity Index and Cation Exchange Capacity of Ball Clay
Plasticity Index
Cation Exchange Capacity
FIGURE 8
60
-------------------------------------------------------·----------------------~
~ \C)
100
80
~
.. 6 ~ f;J::l
~ u ~
d 4•b
2
or o , 10
Floc culeu t -4-- ·-----------------r
20
I I
I I
IJ ..-\ 4'% '" 0
'
30
2% Flocculent ~~
40 50
PLASTICITY INDEX,% AND CEC, m.e./100 grns. SOIL
Plasticity Index and Cation Exchange Capacity of Onyx Cave Clay
Plastic Limit
Cation Exchange Capacity
FIGURE 9
60 70
N 0
~ .. ~ r..l
~ ~ c.>
100
80
60
40
20
I
0 I I I
0 I
I I
I
e' I
I
I
I I
cq '
'<'--4% Flocculent ---4---, Plasticity Index and Cation Exchange Capacity of Bentonite
Plasticity Index
Cation Exchange Capacity
FIGURE 10
0 ~--~---··.....L...-----·-·-·------L ____ L..,._
----'-------..l-------'--------' 600 100 200 300 400 500
PLASTICITY INDEX,% AND CEC, m.e./100 gms. SOIL N ......
L. I
8
% Water Content
60
20
Liquid Limit
Plastic Limit
Plasticity Index
% Dispersent % Flocculent
FIGURE 11. KAOLIN
8 4 0 4 8
Liquid Limit
Plastic Limit
Plasticity Index
8 4 0
Liquid Limit
22
Plastic! Limit '
Plasticity 20 Index
4 8
% Dispersent % Flocculent
FIGURE 12 • BALL CLAY
400
200 Liquid Limit Plasti
city Inde~ ._.-~~P~l~a-s~t7i.4c Limit l
8 I 4 0 4 8
% Dispersent % Flocculent
FIGURE 13. ONYX CAVE CLAY
% Dispersent % Flocculen,t
FIGURE 14. BENTONITE
23
the valence of the adsorbed ions.< 3) At the liquid limit clay minerals
with large, monovalent adsorbed cations, such as sodium, tend to orient
themselves into parallelism between adjacent particles because of the
mutual repulsive forces between them. This is also suggested in the
laboratory from the smooth, glossy consistency of the dispersed samples
at the liquid limit. The smaller, divalent calcium ions reduce the
effective thickness of the micelle and parallelism of the clay particles
would also be expected. However, owing to differences in particle size,
edge-to- face bonding occurs due to attraction between the positive
charges of broken bonds at the edges and the net negative charge of
the surfaces of the clay particl es.( 3) This bonding results in a
random, cardhouse arrangement of the clay particles with high voids
which contain free water. Since the cation exchange capacity is a
function of the charge deficiency caused by substitution within the
crystal lattice of the clay mineral and the number of broken bonds
around the edge of the clay particles relative values of the liquid
and plastic limits may be predicted from the cation exchange of the
soil if the type and concentration of adsorbed cation is known . In
clays of higher cation exchange capacity, as bentonite and illite,
net charge on the particle surface would be more significant than the
charges at the edges due to broken bonds as these clays have high
particle diameter to thickness ratios. Thus the influence of the
thickness of the diffuse layer will have more significance than the
orientation or structure of the clay micelles for soils of high cation
exchange capacity which will result in higher values for the liquid
limit with monovalent sodium versus divalent calcium as the adsorbed
ion . Other investigators have also found inconsistencies in the
24
relationship between the liquid limit and the nature of the exchange
able cations on the surface of the clay particle. It has been reported
that montmorillonite and to a lesser degree illites have higher liquid
limit values for sodium versus calcium as the exchangeable cation. In
contrast to this, clays of the kaolin family will often have lower
values for the liquid limit with sodium as the adsorbed ion as compared
with values obtained with calcium.<23) More total water is required for
sodium montmorillonite because more water is adsorbed in calcium
montmorillonite. In kaolin only a small fraction of the total water
is adsorbed on the particle surface and the liquid limit appears to be
a function of interparticle attractions. Sodium in comparison with
calcium as the exchangeable cation would be expected to reduce particle
attractions resulting in lower values for the liquid limit.
It has been noted that the tendency towards edge-to-face arrange-
f h 1 1 . h d . H (23 ,24) ment o t e c ay partie es 1ncreases wit ecreas1ng p . The
following pH values were obtained for the clays used in the synthetic
soils in this investigation: bentonite 8.1, Onyx Cave clay 7 .9, ball
clay 4.7, and kaolin 4.4. This suggests increased preference of kaolin
and ball clay towards edge-to-face particle arrangement.
As the plastic limit is approached upon evaporation the oriented,
parallel particles of the dispersed soil can more easily approach each
other, whereas the random, cardhouse structure of the flocculated soil
will still contain a higher degree of voids due to its edge-to-face
arrangement of clay particles. Thus soil structure will be the
predominating factor resulting in higher values of the plastic limit
for the flocculated soil. Increasing amounts of manipulation of the
flocculated soil will initiate breakdown of the structure and
variations of plastic limit values between different laboratory
technicians may be experienced . I n clays of low cation exchange
capacity the influence of positive charges at the particle edges re
sulting from broken bonds may have more significance than the charge
intensity of the surface as the particle diameter to thickness ratio
is lower. If the effects of the charges at the particle edge prevail
over the net surface charge the effects of particle orientation would
25
be of greater importance than the thickness of the micelle as determined
by the adsorbed ion. Thus kaolin and ball clay which possess low
cation exchange capacities may have higher values for the liquid limit
in the flocculated versus the dispersed state due to higher voids and
interlock of the random, cardhouse particle arrangement . The influence
of structure would then also be of importance in determination of the
plasti c limit.
The effects of designated percentages of additives upon the liquid
and plastic limits and plasticity index of soil mixtures of varying
percentages of clay fraction are shown in Figures 15, 16, 17, 18 and
19. It was noted that the dispersed samples had higher dry strength
than the flocculated. The apparent silt range was observed to begin
at lower values of c lay fraction for the dispersed than for the
floccul ated samples which would suggest lower values for the plastic
limits for the dispersed soils . Valid plastic limit determinations
could not be made on samples of one hundred percent silt. The pro
jection of the plasticity index was found to intercept the origin at
zero percent moisture and clay fraction although deviation from
linearity would be expected in the silt range. Comparisons of the
plastic and liquid limits and plasticity index of the different clay
types are shown in Figures 20, 21, and 22 for the clays in the unaltered
10{!
80 J..
~ .. t 60 rz:l
~ c:..>
~ c:..> 40
20 1-
0 ...1--
10
·---·- .. -..-.. ··~-~---· ---~------·- .... ·--------
(i)
' I I I
I I I I
I I I I I
0, • / I
I I I
I I I I I
I I 80 ., I I
I I I I / I I
I I I / (-').0 ' I I
/ < '0 0'1,. •.
' t
20 30 40 50
WATER CONTENT , %
-··--------. ----------
Liquid and Plastic Limits of Kaolin
• Liquid Limit 8% Flocculent
Liquid Limit -e- 8% Dispersent
Plastic Limit --- 8% Flocculent
--0-- Plastic Limit 8% Dispersent
FIGURE 15
60
N (1\
s-2
" E-l z I'Ll
~ c.:>
~ c.:>
lOQ..
8
6
4
I I
..[
2
I 0 I
I I
I 0 I
I I
'0 '
I I
I
I 0 I
I I
0 I
I
'I I
I ·•) .
I I
.j
I I
I
0~·, " ' . ' "-·
'
• \
,-,> '-'-
I I
•l r.
I I
I
I
I I
I I
I I. 0
10 20 ',..;:;>'-J.,.. _____ _.
~ ~----------~--------~30 40
WATER CONTENT,%
I I
G I
•
-(;}--
- -o--
- -o--
$
0 ,'
//
/
Liquid and Plastic Limits of Ball Clay
Liquid Limit 8% Flocculent
Liquid Limit 8% Dispersent
Plastic Limit 8% Flocculent
Plastic Limit 8% Dispersent
FIGURE 16 ~--------------~--------------l 50 60 70
--------------·------· ---~-----·- --- ~-·-··---. -------- N -..J
,.___.,.._ ----· ~--~
s-!! .. t ~
~ C,)
j C,)
100
80
60
40
20
I
t
I I
I I
I
I I
q) I
I I
~ I I
</J I I .•0 -
\ \ 1:' \ I
' I ' I ~ ..
\ \
\
I I
I
I
I I
I
\
0 I I @ I I
20 40 60
.
WATER CONTENT, %
L ------
----~.-~.
---..1
80 100
___ . ......._..._, ... .,..= .. --. ..,..,._.-"-"=....r....._-... ........ ~ .. ' ---~ ............. ,... .... -. -- "-"' -·- '-. .... ._
Liquid and Plastic Limits of Onyx Cave Clay
,..... ""'
-- ... --
Liquid Limit 6'% Flocculent
Liquid Limit 4'% Dispersent
Plastic Limit 6'% Flocculent
Plastic Limit - -& - 4'% Dispersent
FIG'(J"RE 17
N CX>
100
80
s-!! ... t 60 rx:l
~ u
~ u 40
20
I ~
I (
'cv \
I I
I 0
I
I
\
0 ,___ __ _
20
I
0 I
I
I I
i I
I ~
I
I
I
I 1
I
I
I
I
I
'
I
I
I
' I
-·-...-· ... --~ -·~---·... ...·-·-···- -
Liquid and Plastic Limits of Onyx Cave Clay
• I":'\ .....,
--.--
--e-
Liquid Limit 2% Flocculent
Liquid Limit 2% Dispersent
Plastic Limit 2% Flocculent
Plastic Limit 2% Dispersent
FIGURE 18 _.._ ______ _._ _______ ~L-...-------- - _,
40 60 80 100
WATER CONTENT, %
------------------- -----.... -- -·· -· . ~-------------- -··-·- ------·-N \0
100 . <;:T I I ,,
I / Liquid and Plastic I I If Limits of Bentonite
80 1-I I
8• G)
I I I I
I I ~ I I
.. 60 J I
~ 0e ~
I I
~ I I
L / Liquid Limit I I 4% Flocculent
c.> I I
8
~ ,,
j / Liquid Limit I I 0
c.> 40 0f 4% Dispersent ,,
' / ,, ------ Plastic Limit
II 4% Flocculent
" !/ Plastic Limit If --G--20 1- @ 4% Dispersent
FIGURE 19
0 l--@~----L------l..------1------..__ ____ _.... _____ __~... __ . __ ··--· .1
100 200 300 400 500 600
WATER CONTENT , % w 0
-----------·~·-----
100
80
~ .. ~
60 l)t1
§ C)
~ C) 40
2
' I
! ' I I
I ~~ I
'• ;,~ \\ ' \\
I \
~~ 1\
~ ~
\ V..-------~---~-----''---------"--------'L-----·· ----1
20 40 60 80 100
PLASTIC LIMIT, % WATER
Plastic Limit
vs.
Clay Content
Ball Clay
---- Onyx Cave Clay
----- Kaolin
FIGURE 20
w .....
r---------------------------------------------"-------------------------------------------~ 100
80
~ .. ~ 60
~ ~ u
s u
40
20
0 ...__ __
I I
I I ,.
I I
I I
I /e
I I
{
I I
I I
I
\ / . ( \ ' \ I
'\ \\
/ /.
/
• I / "
/ /
/ /
• / ... /
// /
• /
" /
" /. /
20 40 60 80 100
LIQUID LIMIT, %WATER
Liquid Limit
vs.
Clay Content
Ball Clay
Onyx Cave Clay
Kaolin
FIGURE 21
Vol N
100 r • • I Plasticity Index
I I
vs. I I
Clay Content I
I I
I I 80 ~ ~ I
I• I I
I I
I I I ~ I
I' .. 60 T tl I !:z;l I I ~ I I u I .I
Ball Clay g I I u 40 ., I _ _ __ Onyx Cave Clay I I
I .I _____ Kaolin I 7 I I
20 ~0 I
I I I
I I I FIGURE 22
I I
0~ 20 40 60 80 100
PLASTICITY INDEX, % I
I.N I.N
34
state . Bentonite was not shown in the figures as its values were too
great to allow an accurate comparison of the Atterberg limits with the
clays of lower activity coefficients. The liquid and plastic limits
and plasticity index versus varying clay fraction for bentonite in the
unaltered state are shown in Figure 23. Linear relationships between
cation exchange capacity and the liquid and plastic limits would be
expected since all are a function of the surface area and activity.
In Figure 24 the liquid and plastic limits are plotted as abcissa and
the cation exchange capacity as the ordinate for the natural, un
altered clays. A direct proportion between the plastic limits and the
cation exchange capacity is evident. Linear relations between the
liquid limits and the cation exchange capacity are apparent at low
values. The low value of cation exchange capacity determined for
bentonite may be higher for other types of montmorillonites which
would result in linearity throughout the length of the liquid limit
versus cation exchange capacity curve.
---------·--·- --------------- ---- ~ ---····----·-
100
80-
I a-!
I .. ~ 60
, I fZl
~ I u I
~ I u 40
• I \ I I
20 ~ ~ I I ~
' I I I I
f
// ./
Liquid and Plastic Limits of Bentonite
Liquid Limit
Plastic Limit
FIGURE 23
0 L _____ !~O ------L _________ t__ ___ ----- __ - -------- L _ _ __ -. -- .... ----l
200 300 400 500 600
WATER CONTENT, %
--------------w VI
-------- --~-----
100 -
80 • I ___ _______.
,...:! H
I I I
I
I
/ ~-~ Cation Exchange Capacity
0 en . ! 0 0 r-l -. CIJ . Ei .. u ~
60
40
20
I I I I I I I j
• I I l I . _, I.
I
/ I
I
_L __ 0 l ~ I 300
100 200
WATER CONTENT, %
·-----------------------·--------------·
vs.
Liquid and Plastic Limits
Liquid Limit
Plastic Limit
FIGURE 24
400 500 600
I I
. ~-~-41
l
w 0\
37
V. CONCLUSIONS AND RECCI1MENDATIONS
It can be concluded from the results of this investigation that
the liquid and plastic limits, plasticity index, and cation exchange
capacity are linear functions of the percent c l ay fraction present in
non-organic synthetic soils . The Atterberg limits and cation exchange
capacity increase in direct proportion to the percent clay content
contained in the soil .
The values of the plasticity index approach zero as the clay
fraction is reduced to zero indicating zero plasticity for soils
consisting of one hundred percent non-plastic fines. In the silt
range deviation from linearity was found for the liquid and plastic
limit curves and positive values were obtained at zero percent clay
content. The silt characteristics began to predominate at lower values
of clay fraction for soils of higher activity coefficients. This may
be attributed to their swell characteristics and resulting ability to
fill the voids between the silt particles due to the expansion of the
clay particles.
The method proposed by Brown that was employed in the determination
of cation exchange capacity is not as effective as other methods when
testing soils of extremely high activity coefficients which experience
high swell characteristics and low permeability as complete reaction of
the soil with the acetic acid or ammonium acetate cannot be assured.
Although more rigid equipment and laboratory skill is required other
methods of determining cation exchange capacity would yield more
reliable results.
The concentration as well as the type of electrolyte had significant
effects on the liquid and plastic limits . As the percent flocculent was
38
increased in kaolin and ball clay the liquid limit increased until a
plateau was reached indicating the maximum degree of edge-to - face
arrangement of the clay particles had been achieved. The liquid limit
of Onyx Cave clay and bentonite which possess higher values of cation
exchange capacity was observed to decrease as the percent flocculent was
increased due to the reduction of the thickness of the clay micelle
suggesting the minor effects of soil structure. The liquid limit de
creased approaching a minimum value where minimum thickness of the
micelle was attained. The plastic limit increased from the dispersed
to the flocculated state for al l soils infering increased importance
of soil structure at lower water contents as influenced by the
concentration and type of adsorbed cation . The l iquid limit was found
to increase more than the plastic limit for the kaolin and ball clay.
The resulting plasticity index generally increased from the dispersed
to the flocculated state indicating the edge-to- face particle arrange
ment predominated over the thickness of the clay micelle in influencing
the liquid and plastic limits of low cation exchange capacity soils.
The plasticity index of Onyx Cave clay and bentonite decreased as they
were changed from the dispersed to the flocculated state . In soils of
high cation exchange capacity the thickness of the micelle as affected
by the type and concentration of the cation in the diffuse outer layer
contributes greater influence upon the liquid and plasti c limits than
the effect of soil structure.
Apparent linearity was found between the values of plastic and
liquid limits and the cati on exchange capacity for different clays of
low to intermediate activity coefficients. The values for bentonite
deviated from this straight line relationship .
39
The use of synthetic soil eliminates the problem of unknown
organics in the soil and the soil can be designed to meet the require
ments of the investigator . In f uture work in this area more soi ls in
the intermediate range should be investigated. Mixtures of kao lin,
illite, or montmorillonite could be used to obtain desired cation
exchange capacities and activity coefficients . Values for Atterberg
limits and cation exchange capacity for soils of high activity should
be compared with values found for bentonite.
Liquid and plastic limits using different material as non-plastic
fines other than silt resulted in lower values at low clay content
where the characteristics of the silt-sized particles predominate.
The cation exchange capacity and Atterberg limits of the non-plastic
fraction will be influenced by the particle size, shape, and
distribution and the exchangeable cations present on the particle
surfaces .
BIBLIOORAPHY
1. DAVIDSON, D. T., and SHEELER , J. B. (1952) Clay Fraction in Engineering Soils : III Influence of Amount on Properties, Highway Research Board 31, p. 558- 563.
41
2 . DAWSON, R. F. (1959) Investigation of the Liquid Limit Test on Soils, ASTM Special Technical Publication 254, p. 190-195.
3. SCOTT, R. F . (1963) Principles of Soil Mechanics, Addison-Wesley Publishing Co., Reading, Massachusetts, p. 36-52.
4. HAVENS, T. H., YOUNG, J. L. and DRAKE, W. B. {1949) Some Chemical, Physical, and Mineralogical Features of Soil Colloids, Highway Research Board 29, p. 567-577.
5 . SEED , H. B., WOO~ARD , R. J., and LUNDGREN, R. (1964) Fundamental Aspects of the Atterburg Limits, ASCE Proceedings, Vol . 90, No. SM6, pt. 1, p. 75-105.
6. GRIM, R. E. (1952) Ion Exchange in Relation to Some Properties of Soil-Water Systems, ASTM Special Technical Publication 142, p. 3-10.
7. van OLPHEN, H. (1956) Forces Between Suspended Bentonite Particles, Proceedings of the 5th Nat. Conf. on Clays and Clay Minerals, Nat. Academy of Sci.-Nat. Research Council Pub . No. 406, p. 204 .
8. GRIM, R. E. (1953) Clay Mineralogy, McGraw-Hill, New York, p. 129.
9 . BAVER, L. D. (1929) Relation of the Amount and Nature of Exchangeable Cations to the Structure of a Colloidal Clay, Soil Science 29, p.291- 309.
10. SCHOLLENBERGER, c. J. and SIMON, R. H. (1945) Determination of Exchange Capacity and Exchangeable Bases in Soil by Ammonium Acetate Method, Soil Science 59, p. 13-24.
11. SCHOLLENBERGER , C. J. and DREIBELBIS, F. R. (1930) Analytical Methods in Base Exchange Investigations on Soils, Soil Science 30, p. 161-173 .
12. BROWN, I. C. (1943) A Rapid Method of Determining Exchangeable Hydrogen and Total Exchangeable Bases of Soil, Soil Science 56, p. 353-357.
13. DAVIDSON , D. T. and HAUTH, W. R. (1950) Particle Size Distribution and Cation Exchange Capacity, Highway Research Board 30, p. 458-464.
42
14. American Society of Testing Materials, 1958, ASTM Standards, Part 4, Test D422-54T, p. 1119.
15. SPANGLER , M.G. (1960) Soil Engineering, 2nd Edition, International Textbook Company, Scranton, Pennsylvania, p. 42.
16. PECK, R. B. , HANSEN, W. E., and THORNBURN, T. H. (1953) Foundation Engineering, John Wiley & Sons, Inc . , New York, p . 35.
17. American Society of Testing Materials, 1961, ASTM Standards, Part 4, Test D423-61T, p. 1286.
18. American Society of Testing Materials, 1961, ASTM Standards, Part 4, Test D424-59, p. 1291.
19. CASAGRANDE, A., Classification and Identifications of Soils, Transactions ASCE , Vol. 113, 1948, p . 901-991.
20. NORMAN , L. E., A Comparison of Values of Liquid Limits Determined with Bases of Different Hardness, Geotechnique , Inst. of Civil Engrs., Vol. 8, No. 1, London, 1958, p . 79-91.
21. FEDA, J ., Fundamentals Aspects of the Atterburg Limits, Transactions ASCE, Vol. 91, No. SM6, November, 1965, Part 1, p. 111.
22. SEED, B. H., WOODWARD, R. J ., and LUNDGREN , R., Fundamental Aspects of the Atterburg Limits, Transactions ASCE, Vo 1. 90, No. SM6, November, 1964, Part 1, p. 77.
23. MICHAELS , A. s., Physico-Chemical Properties of Soils, Discussion, ASCE Proceedings, April, 1959, Vol. 85, No. SM2, Part 1, p. 91-92.
24 . TAYLOR , A. w., Physico- chemical Properties of Soils: I on Exchange Phenomena, ASCE Proceedings, April, 1959, Vol. 85, No. SM2, Part 1, p. 20-23 .
VITA
Kent James Schwieger was born on June 24 , 1942, in Ft. Dodge,
Iowa, the son of James A. and Olga Fo Schwieger.
He received his elementary and high school education at
Marshfield, Missouri, graduating from Marshfield High School in
May, 1960.
43
He enrolled at the University of Missouri at Rolla in September,
1960, and received a Bachelor of Science in Civil Engineering from
that institution in May, 1964.
He has been enrolled in the Graduate School of the University
of Missouri at Rolla since September, 1964. He accepted a Graduate
Assistantship in January, 1965.
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