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

Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses

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

This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact scholarsmine@mst.edu.

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.