EJ'FEOf OF FREEZING AND THAWIIG .. 01 UNOONFIBED OOMPRESSIVE STRENGTH OF OLAY-LIME MIXTURE

WITH AID WITHOUT AIR ENTRAINING AGENT

by

Abdul Ghan1 Shandaala

1'hes1s submitted to the Graduate Faoult;r of the

V1rg1n1a Pol7teohnio Institute

in candidacy for the degree of

MASTER OF SCIENCE

in

01v11 Engineering

September, 1964 Blacksburg, Virginia

2

Dedicated

To 1fff w1.te and two children

/ ';-·

3

TABLE OF CONTENTS

LIST OF FIGURES •

LIS'.r OF TABLES

• • • • • • • • • • • • • • • Page

• " • 5

• • • • • • • • • • • • • • . •· • • .- • 6

AOKJfOWLEDGMENT S • • • • • • • • • • • " . . • • • • •• 1 INTRODUOTIOlf • • • • • • • • • • • • • • • • • • • • 8

REVIEW OF LITERATURE • • • • • • • • • • • • • • • •• 10

What Is Meant by Lime •• • • • • • • • • • . . " .10

What Happens When Lime is Added to the Soil •••• ll

Jreezing Phenomena in Soil • . . " • • • • • • •• 12

freezing and Thawing Effects on Lime stabilized Soil • ••••••••••••••••••• 15

Air .intra1nment. • • • • • • • • • • • • • • • •• 17

PURPOSE .AND SOOPI •• • • • • • • • • • • • • • • • • .19 MATERIALS AND PROOEDURES. • • • • • • • • • • • • • • .20

Soll. • . . . . . . . . . . . . ' . . . . . . • • 20

Lime. • • • • • • • Grain Size Analysis

Atterberg Limits •

• • • • • • •

• • • • • •

• • • • • • •

• • • • • • • • 20

• • • • • • ••• 20

• • • • • • • • .20

Density Tests • • • • • • • • • • • • • • • • .22

Fabrication of Specimens • • • • • • • • • • ••• 22

Air Ent ra1nment • • • • • • • • • • • • • • • • .23 .23 Ouring • • • • • • • • • • • • • • • • • • • • •

Freezing and Thawing • • • • • • • • • • • • • • • 23

Unconfined Compressive Strength Testa. • • • • •• 24

DESIGI OF EXPERIMENT • • • • • • • • • • • • • • • • .25

RESULTS AND DISOUSSION. • • • • • • • • • • • • • •

Atterberg Limits Tests • • • • • • • • • Dry-Density Tests. • • • • • • • •

Unconfined Compressive strength •• • • •

• • •

• • •

• • •

• • • .Air Entrainment . . . . . . . . . . . . . . ~ Five and Ten Cycles of Freezing and Thawing ••

Ten Day-a 1n a Moist Room • • • • • • • • • • •

OONOLUSIONS •••• ••• ••••• • • • •••••• .BIBLIOGRAPHY , • • • • • • • • • • • • • • • • • •

VITA. • • • • • • • • • • • • • • • • • • • • • •

Page

27

27

27 30 45

45

47 49

50

53

5

LIST OF FIGURES

1. Grain Size Distribution Ourves • • • • • • • • •

Page

21

2. Effect of Lime-Soil Mixture on Atterberg L1mite. 28

3. Standard Miniature Oompaotion Ourves ·Olay-Lime· Mixture. • • • • • • . • • • • • • • • • • • . • . • 29

4. Oompaoted strength - Freezing and Thawing Oy'Ql~a Relationship of Olay-Lime Mixture. • • • • • • 34

5. Oompacted strength - Lime Relationship of Olq • 35

6. Oompaoted strength - Lime Relationship of Olq on Ten Days 1n a Moist Rooa • • • • • • • • • 36

7. Effect of Air Entraining .Agent on Oompreseive Strength • • • • • • • • • • • • • • • • • • • 38

8. Ef.feot of Seven Drops of Air Ent raining Agent on Oompreseive Strength. • • • • • • • • • • • 40

6

LIST OF TABLES

l. Experiment A (without air entrainment). • • • • • .Ex:periment B {with air entrainment) • • • • • • • Atterberg Limits • • • • • • • • • • • • • • • •

4. Dr,y Density Tests • • • • • • • • • • • • • • • • 5. Unconfined Oompressiv·e Strength (psi) of Cle;y-

L1me Mixture .After Ouring, :rreez1ng and Thawing

Page

25 26

27 30

and Kept in a Moist Room • • • • • • • • • • • 32

6. Seoant Modulus of 0191'-Lime Mixture After Ouring, Freezing and Thawing and Kept in a Moist Room • 33

1'. Unoonfined Compressive strength (ps~) of Air En-trai-ne4n01Sl'-L1me Mixture· after Curing and Five oyoles of Freezing and Thawing • • • • • • • • 37

8. Unconfined Oompress1ve Strength (ps1) of Olay-L!me Mixture Treated with Seven Drops of Air Entrain-ing Agent per Two Specimen Batoh • • • • • • • 39

9. Secant Modulus of Air Entrained Olay-Lime Mixture After Ouring and Freezing and Thawing • • • • • 41

10. Secant Modulus of Air Entrained Olay-Lime Mixture Treated with Seven Drops per Two Specimen Batch 42

11. Quantity of Air in Specimens Treated with Spea1-f1c Number of Drops of Air Entraining Agent • • 43

12.

13. E:tfeot of Lime on Oompress1ve Strength • • • • • Effect of Freezing and Thawing Oyoles on the

strength of Olay-Lime Mixture • • • • • •

Eff'eot of Moist Room on Compressive Strength of Olay-Lime Mixture • • • • • • • • • • •

• •

• •

46

47

48

7

.AOKNOW LEDGME.Nf S

The author would like to take this opportun1t7 to ex-

Pl'8SS his deep appreciation and indebtedness to his thesis

ad.visor Dr. Riohard D. Walker for his patience, prudent

guidanoe and encouragement throughout this stuc!T. Appreo1-

at1on is also expressed to Dr. H. M. Morris for his friend-

ship and assistance. !he author also wishes to express his appreciation to

all the members of the Oivil Engineering Department tor their

help in his graduate program, and to Professors J. F. Poulton

and F. D. Rollins in the Architecture and Mathematics Depart-

ments.

Kind regards and thanks are extended to Mrs. R. D. Walker

for her typing asaistanoe.

8

INTRODUOTIOB

The rapid increase of air and highway transportation re-

quires a rapid improvement 1n the phy'sioal properties or soil,

espec1all7 soil strength. A large number of processes of soil

stabilization using admixtures are known to exist; most, al-

though 1n common uae, are still undergoing extensive labora-

to17 experimentation. Portland cement, bitumen, calcium

chloride, lime and many others are included among these addi-

tives in aotual field use or still in laborator,y investigation.

Sinoe hydrated lime is the main additive used in highw&T

construction, it has been extensivel7 used in the United states

tor the purpose of improving as well as strengthening the aub-

grade on which the pavement rests• It has been exp_er1mentally

shown that the strength ot the lime-stabilized soil can be

greatly affected b7 freezing and thawing. The main question

.tor which an answer has not 7et been found is, ~How much

strength does the lime-stabilized soil lose when subjected to

cycles o.t freezing and thawing, and wby'?.. An answer to this

question will enable the highway engineer to control the

pavement thickness which in turn results in monetal'7 savings.

Wide research programs have been carried out in the

United States for the purpose of disoovering a wa::r to control

this freezing and thawing problem. · Since the soils in south-

west Vit'g1n1a are mostly plastic olqs and are subject to

9

freezing and thawing, and since limestone (Oa003) from which

hydrated lime is derived is extensively available, considera-

ble research has been done on this subject in Virginia.

Extensive studies of soil stabilization are being oarried

on by the Civil Eng1neerlni ~apartment of Virginia Polyteohnic

Institute, particularly' in the area of stabilizing plastic

clay soil with b7drated lime.

Soil systems ma.v be classified as open systems and

closed qstems, An open system is free to take on or lose

water while a closed system is prevented from gaining or

losing moisture. Since plastic clays are rather impermeable,

it is possible that they behave mostl.7 as a closed system in

the field. Therefore, the closed system was used in this

work, where the specimens were wrapped and sealed in alum1num

foil and cured for two days at 12001 1n the oven. Freezing

and thawing tests were made by placing the sealed specimens

in a zero °F deep freezer for six hours and in a 70°F en-

vironment for 18 hours. Speoimens were tested for unconfined

compressive strength after five and ten cycles, the percentage

of lime used being between zero and 20 percent by dry weight.

Air entrainment was also used in an attempt to improve

the lime-clay mixture resistance against freezing and thaw-

ing.

10

REVIEW OF THE LITERATURE

.!!!'!!!. il Meant !?z. Lime

Lime is calcium oxide (OaO), obtained by crushing· and

heating limestone {Oaoo3) to drive off its carbon dioxide

(002), leaving the calcium oxide or quicklime (3). Also

there is the lime obtained by burning dolomite OaMg{003)2

which is a carbonate rook ~e?!Y similar to limestone. In

this oase the resulting lime is calcium oxide plus magnesium

oxide, and it is called dolomit1o quicklime. There are then

two chemical types o! quicklime, calcitic (OaO), and dolo-

mitio (OaO + MgO).

When water is added to oaloitio quicklime, the chemical

reaction gives calcium h:ydrox1de (Oa(OH)2) plus heat. Calcium

hydroxide is called hydrated lime or oaloitio hydrated lime.

Water added to dolomitic quicklime gives the product

known as dolomitic monohydrated lime (Ca(OH)2 + MgO). Under

steam and pressure the magnesium oxide (MgO) oa.n be converted

and the result is calcium h;ydroxide and magnesium h1'droxide

(Oa(OH)2 + Mg(OH)2) or dihy'drate dolom1t1o lime. The degree to which a lime is oalo1t1o or dolomitic

oan be expressed by the caloium magnesium ratio Oa/Mg. Cal-

c1t1o limes present a verr large Ca/Mg ratio whereas with

dolomitic lime this ratio is small, on the order of less

than 2:1 (18).

11

Moat of the lime used for road stabilization to date has

been bTdrated lime, although quicklime has been used with

suocess, Hydrated 11me has been applied both in powder and

slurry forms. Quicklime has been applied only in the powder

form but has been known to burn workmen who were not :properly

p:Ntected ( 3).

~ Happens When Lime is £dded l2. th!, So\l

This short discussion will cover only a few o.f the many

chemical reactions which take place in so11~11me mixtures.

!2J1 exchange !!!! flocculation. When lime and a moist

cohesive soil are mixed together and allowed to cure in a

loose condition for a period of time, the soil becomes fri-

able and attains a silty-like conu1t1on, and the plasticity

is lowered, This is due to one of two conditions. In one,

the strong calcium cations of lime replace the weaker metal-

lic 1ons 1 such as sodium and hydrogen. .Another process is

the crowding of additional oalo1um cations of the lime onto

the surfaoe of the ola,y. Both processes change the number

of eleotrical charges on the surfa.oe of the clay particles.

Olay particles then become eleotrioally attracted to one

another and they tend to flocculate to one another. (13,15)

Pozzolan1o action. The calcium in the lime reacts with

certain soil minerals to form new compounds. Usually, alum.1-

nous and s111o1ous minerals in the soil react with the lime

to produce a gel of calcium silicates and aluminates that

12

tends to react with lime to produce a cementing compound

known as a :pozzolan, This rea.ot1on, known as 1•pozzolanio

action"; 1s a long term reaction and one that results in

greater strengths, if the lime soil mixtures are cured for

a period of time (13, 14).

Carbonation, The third important reaction 1s carbona-

tion of lime by absorbing carbon dioxide (002) from the air,

The carbon dioxide reacts with oalcium hydroxide forming

calcium carbonate, These carbonates form weak cements whioh

some _-1nvest1gajors believe to be deleterious to overall

strength gains ( 13) ,

Ef'fect 2.! densitz, It is generall.7 recognized that the

optimum unit dry weight of the oompaoted soil is decreased by

the lime admixture, although the soils will show 1norease in

strength~ The optimum moisture content also varies with ad-

dition of lime to the so1ls, in most oases showing small in-

crease or the order of two or three peroent.

Freezing Phenomena !1J. i2!l,

For the purpose of this discussion 1t is neoessar;r to ·

divide the freezing phenomena of soil into two distinctive

parts, One part is where ice segregation takes place in a

frost susoeptlble soil, due to a. water supply being available

and to slowly depressed freezing temperature, which results

in frost heave. Frost susceptible soils fall mostly into

13

the categories of silt and silty olays. A second part is the

etfeot of alternate oyoles of freezing and thawing on a rela-

tively impermeable Olaf soil wh1oh 1a not normally susceptible

to much frost heave.

Frost heave. Silt and silty clay soils. when frozen

under natural conditions, generally behave as an open system

with respeot to water, 1.e., they have a water supply from

the out side. Taber (4) states that excessive heaving in th1s

system 1s always accompanied b7 the segregation of some of

the water .;fo form layers or lenses of more or less pure 1oe.

Taber found that ice segregation does not occur in a closed

soil system. The factors which chiefly affect 1oe segrega-

tion. according to Taber, are texture of soil, composition

of soil, supp]¥ of water, rate of removal of heat and surface

load.

Effeot 2! freezing W. thawing. Since it is thought

that the soils out of doors generally behave as open systems,

most freezing and thawing studies have been made with speci-

mens in contact with water and moisture absorption allowed

(17). However, in many instances, vel"Y' impermeable plastio

ol~s are used which mar operate more as a closed system.

Oonorete also behaves as a closed system, and Powers (6)

has developed a hypothesis describing the action of freezing \

and thawing on such a system. It is thought possible that

such a hfpothes1s might also apply to impermeable soils.

14

Powers' hypothesis rests mainq on the premise that when ice

begins to form in the outside of specimens, the unfrozen

water will be displaced toward the center. If the water were

tree to move without resistance, no bydraulio pressure what-

ever would develop. However, since the water 1s required to

move through a fine-textured porous substance, the force

causing the movement will give rise to a corresponding fric-

tional resistance and gradients of hydraulic :pressure will be

present during the movement of the water according to the

laws of hydraulic flow.

If this reaction against the force displacing the water

inward 1s suff1o1entl.y high, then it oan be regarded as being

capable of damaging the specimen.

Powers also states that resistance to freezing and thaw-

ing is largely affected by degree of saturation and permeab111-

t7 oharaoterlstios.

Walker and Karabulut (20) stated a comparison of some

permeability values of ohert and dolomite aggregates, silt

and clay soils, and oonorete mortar. These values are pre-

sented in the table below.

15

Typical Permeability Values

Oonorete Mortar (12)

Dolomite (12)

Ohert (12)

Olay (11)

Silt (11)

l to 300 x io-10 cm per sec

300 x io-lO om per sec

l x io-10 cm per seo

less than 1000 x io-10 cm per seo

no more then lo,ooo x io-10 om per seo

Freezing IW1 Thawing Effects 2!!. 1:!.m!.-§tabi~1z94 §oil

Work on freezing and thawing effeots has been carried on

by many investigators who have approached the problem in many

different directions.

Hoover, Handy and Davidson (7), experimented with an

open qstem of freezing and thawing on a Texas coastal plain

clay-. They used three oompaotive efforts: l) between standard

and modified Prootor densit7, 2) equivalent to modified Proc-

tor, and 3) above modified Proctor. The criteria used to

evaluate the effeot of increased density on durability of

the specimens a~er various oyolea of freezing and thawing

were unconfined compressive strength, moisture absorption and

average increase in height of the specimens.

The conclusion was that high density does improve dura-

bility of so11-11me-fl7ash mixtures to the extent that after

an initial moist cure, clay soils ga.1ned strength even more

rapidly during freeze-thaw oyoles than they did in continued

16

moist cure condition. The strength of clay specimens during

cycles of freeze-thaw correlated well with moisture absorp-

tion. OlaJ" showed a drastic increase in absorption up to 5

cycles, after which the specimens slowly lost water. !he

strength dropped about 50 percent from the first to the fifth

oyole, after which there was a slow gain.

Oorte (8) in his study showed how a particle-size sort-

ing occurs in saturated granular soils due to freezing and

thawing oyoling. The laboratOX'Y' experiments and t1eld studies

indicated that there was a tendency for a heterogeneous mix-

ture of grains to become vertically sorted under repeated

freeze-thaw action, when adequate moisture was present, there-

by 1noreas1ng the volume ot the mixture. This phenomenon

was observed when the freezing and thawing plane moved from

the top or from the bottom. The faot that the particles

moved upward as a result of freezing and thawing from the

top indicated that vertical sorting must take place in granu-

lar heterogeneous seasonally frozen soil outside the perma-

frost area if adequate moisture is available.

E. A. Whitehurst and E. J. Yoder (10) studied three

soils with addition of o, 2, 5, and 10 percent of lime.

After fabrication, the specimens were permitted to cure 1n a

moist room for various periods of time, one to thirty-six

weeks. At the end of the curing period some of the specimens

were subjected to 12 cycles of freezing and thawing. Their

17

oonolusions were as follows:

1) The texture of the soil has an appreciable

e:t':t'ect upon the resistance of the lime-soil mixture to

freezing and thawing.

2) For a given lime oontent, increased compaot1on-

or greater density, results 1n increased resistance to

freezing and thawing.

3) Lime in quantities of 5 percent or more, by weight

of the soil, greatly increased the durability of the l1me-

so11 mixtures; the greater the lime content the greater the

durability.

4) Two percent lime did not appreciably alter the

durability character1st1os of the soil.

5) In general moist our1ng proved very beneficial to

the 11me-so11 mixtures.

!!.!: Ent r1inment

Air entrainment is the process of installing a quantity

of air through the so11 for the purpose of providing greater

resistance to freezing and thawing. This process has been

studied widely and used by many investigators in the field

ot concrete, but no work has yet been done in the field or

soil mechanics. It has been found experimental]J' that the

ability of oonorete to resist freezing and thawing will be

greatq improved by using five to six percent of entrained

air.

18

!he effect or air entrainment on plastic 0181' soil mixed

with different peroentages of lime and subjected to freezing

and thawing was studied 1n this project, and in general,

proved to be of some benefit.

19

PURPOSE AND SCOPE

The purpose of this studT was to determine the etfeot

of freezing and thawing on the loss in strength of lime-

stab1lized soil, and to investigate the effect of the addi-

tion of an air entraining agent on the freezing and thawing

durability of lime-soil mixturea.

The effect of freezing and thawing on the at rength ot lime-soil mixtures was evaluated by means of unconfined oom-

pre ssive strength tests. Freezing and thawing conditions

were limited to freezing and thawing in air, with the tem-

peratures ot o°F and 70°F being used for freezing and thaw-

ing respectively. Harvard miniature apparatus was used to

determine mo1ature-dens1t7 relationships, using different percentages of lime, with and without air entrainment. Thia

apparatus was also used to fabricate unconfined compressive

strength specimens. .All specimens were oured two dqs at

120°1. Oontrol speo1mena were placed in the 10°1 environ-ment tor ten days while companion specimens underwent freez-ing and thawing.

20

MATERI.ALS .AND PROOEDUUS

Soil -The plastic olay soil used in this project was selected

from the roadside of a out looation near the northwestern

city limits of the town of Blacksburg, Virginia. It was

reddish-brown claJ' soil having a liquid limit (LL) ot 80

percent; a plastic limit {PL) of 48 percent, and a plast1o1t7

index (P.l.) of 32 percent. Olassifioation of the clay soil

a9oording to the AASHO system is A-7-5 with a group index of

20.

Lime -The h3'drated lime (Oa(OH)2) used in this study was manu-

factured at Kimballton, Virginia, b7 the National Gypsum Oom-

Pal11' of Buffalo, New York. The percentage of calcium carbon-

ate (Oa003) was found to be 6.53 percent. This was determined

b7 placing a sample of the lime in an oven at 900°0 for about

three hours in order to drive off all water and carbon dioxide.

Laboratorr Prooedure1

Grain .§!!!. Ana1ys1s. Grain size analysis of the olsy

soil was performed essentially according to ASfM .D422-54T.

1'he results are shown in Figure 1.

Atterberg Limit a. Liquid limit tests on the air dried

sample of natural soil were performed in aooordanoe with

~ bD ..... Cl> ~

I>:. .0 J-4 Q) s::I

oM ft.I

~ Q) 0 J.i Q.)

P-t

ioo __ ~~~,--~~r-~~~~rr---r-r-r--r---r---r~..;.._--r------,

90

80

70 ·-

60 ---o.05 o.o4 0.03

l -• .. _i_ --- +-

- j ------- - ·-----· ------ ·-·--

0.02

i ! i

0.01 Diameter (mm)

. --·-- ----·- ·t----

~----+---. - ----

0.005

'

··-- -----+ I I

--- -- - --- ;.

0.002

Figure 1. Grain S1ze Distribution Curve

I\) ......

22

ASTM D423-54T except fo~ the following modifications: the

soil was molded 1n Harvard miniature apparatus and wrapped

with aluminum foil to preserve the moisture for a period of

48 hours before performing the test. Plastic limit tests on

the air dried sample of natural soil were performed 1n ac-

cordance with ASTM D424-54T with the same mod1f1oat1ons used

in the liquid limit tests.

Densitz Tegtp. Standard density tests were run on the

air dried sample of natural clay soil with the Harvard minia-

ture oompactive apparatus using a 40 pound spring plunger

with 25 blows each on three uniform lSY'ers. Baig and Broberg

(11, 12) found that the dr;y density obtained by this method

was equal to the d:ry density obtained by standard AASHO

method (A.STM 698-58T Method A). When passing the optimum

moisture content, some d1ff1oulty was found 1n compacting

the clay soil uniformly with the spring loaded dev1oe, due to

the sticking of the 0197 soil to the plunger, preventing the

olay from being compacted uniformly. It 1 s recommended that

a drop hammer be used instead of the spring as described by

Anda;r ( 9).

Fabrication 2! Specimens. All specimens were 1. 32 in.

in diameter b7 2,813 in. in height and were compacted b7

Harvard miniature apparatus in three layers. The oompaotive

efforts applied were 25 blows per layer, with the oompaotion

23

dev1oe using a 40 pound spring. The optimum moisture content

for each of the conditions was used tor molding the specimens.

The specimens were wrapped with aluminum foil and immediately

sealed with paraffin in order to preserve the molding moisture

content during curing, freezing and thawing. Representative

samples of the mixtures were taken from the mixing bowl for

moisture content determinations.

!!L Entrainmept. In an attempt to improve the resistance

of lime clay mixtures against freezing and thawing, Darex AEA

manufaotured by the Dewy-Almy Corporation was used as an air

entrainment agent, Specimens containing five percent lime

were treated with 4, 6, 8, 10 and 12 drops of air entrainment

agent for each two specimen batch, while those containing

zero and ten percent were treated with 4• 7, 10, 15 and 20

drops. The Darex was plaoed in the mixing water.

Curing. After the specimens were wrapped in aluminum

foil and sealed with paraffin. they were placed in an oven

at a constant temperature of 120°F for a period of 48 hours,

plus or minus two hours. Experience has 1nd1oated that this

is a realistic procedure and apnrox1mately equal to 45 da,ys

of field curing near Oharlotteeville, Virginia. (9)

Freezing W, Thawing. Freezing and thawing tests were

made b7 freezing the sealed specimens 1n a o°F deep freezer

for six hours, then thawing the specimens in a 10°1 moist

room for 18 hours, After either 5 or 10 cycles of freezing

24

and thawing, the specimens were tested in unconfined com-

pression.

Unconfined Oompress1ye Tests. The unconfined compres-

sive strength at oompaoted and cured specimens was determined

by loading them at a rate of 0.05 inches deformation per

minute. The maximum compressive stress was taken as the

peak load, divided by the corrected cross-sectional area. A secant modulus was also oaloulated by dividing the maximum

stress· by the strain at the point where maximum stress oc-

curred.

25

DESIGN OF EXPERIMENT

The experiments were designed as shown 1n Tables 1 and

2.

Table 1. Experiment A (without air ent ra1nment)

Unconfined dompressive §!irength Test

As No 1 of 1~eoimen1 tert•irt

cured After 5 After o er lo Total

% cycles cycles days in Specimens

1f1me F & T p & 't moist room

0 3 3 3 3 12

5 3 3 3 3 12

10 3 3 3 3 12

15 3 3 3 3 12

20 3 3 3 3 12

L1me %

0

5

10

26

Table 2. Experiment B (with air entrainment)

Unconfined Oomnressive Strength Test No. of drops No. of specimens tested Total per (2) spec- After 5 cycles Specimens imen batch As cured of F & T

4

1

10

15 20

4

6 7 8

10

12

4

1 10

15

20

1

2

1

1

1

1

1

1

l

1

1

l

2

1

l

1

1

2

1

l

1

1

1

l

1

l

l

1

2

1

1

1

12

12

12

Grand total of specimens tested were 96.

27

RESULTS AND DISOUS.SION

RESULTS

Atterberg Limits Tests

Results obtained from these tests are summarized in

Table 3 and represented by the plot of Figure 2. Examina-

tion of Ts.ble 3 and Figure 2 show that the L.L., P.L., and

P.I. of the clay soil were affected by the addition of lime.

Table 3. Atterberg Limits

Lime ~:f % t.L. P.I. 0 so.o 48.o 32.0

5 70.5 51.20 19.30 10 67.4 57.50 9.90 15 10.8 59.7 11.10

20 73.5 62.2 11.3

R1'l. Densitl Teets

fable 4 and Figure 3 represent the results obtained

from the dry density tests. Examination of Table 4 and

Figure 3 show that the difference in the percentage of the

lime added to the olay soil results in the difference 1n

optimum moisture and the difference in the dr,y dens1t7.

-~ -~ Q)

+' s:: 0 0 Q) f..f :::1 ~ or-i 0 ~

9,__~~~~~~--.-~~~~~~~---~~~~~~~~~~~~~~---'\

L.L.= 80 8

70------

P.I. = 32

60

50

P.L. = 48

0

L.L. = 70.5

P.I. = 19.3

= 51.2

5

L.L. =

I

!P.I. = 9.9 I

= 57.5

10

L.L.

P.]. = 11.10 ! '

P.L. = 59.7

Percentage of lime by dry weight of clay

Figure 2. Atterberg Limits of Lime-Soil Mixtures.

P.I.

73. -I -- -----,

= 11.j __ _j

..... = 62.2

20

I\) co

I"'\

~ .......... .0 r-i

~

90

85

.....4 80 >. +> orl en s;::2

~

t- 75 A

70

1r--····-clay + 0% lime I i

/·-clay + 5% lime

r ·--clay + lot lime I I '

I /

;'

.;J-~; •

' 15~ lime r- clay + 't_"t./', ,,,,.. '-" ' -..... "' ----... ....... ~ , 0 II ·•• •• e -

e::./ I ... -··"o·~--:-::-.q .. ~ / .. } ··_,.~ ' ... .. · ' . .. . .' "' .. • 1 ~. ~'u 1 / / . , -.. . . .. .... .. . . ·"" •. '

,; . ' ' ... ~""' ·····-~ ···., • ... ' ' '"' .· '' ,· .. .. '' 7-·--- / .. · d ./ ••• .. .:-.:~, "' . · . ., ,, -. ... .... "-.: .. ,,_, - .· "· .. ' _... .. "; ... , ~ .. · - "· ~

. f\__ clay + 20% lime ··,~~\"',, ·1 ~·

20% 25% 30% 35% 40~ 45% 50~

Moisture Content

Figure 3. Standard Miniature Compaction Curves of Olay-Lime Mixtures.

I\) \0

30

Table 4. Dry Density Tests

Lime % Optimum Olg

bptlmum Densltr Moisture

0 84.6 lb/rt3 33.8 % 5 81.7 It 35.8 It

10 81.0 It 36.5 tt

15 80.1 ti 38.0 II

20 78.5 ti 39. 3 11

Unconfined Oompreasive strength

The results of the unconfined compressive strength tests

of the non-air-entrained soil-lime mixtures are shown in

fables 5 and 6 and Figures 4, 5, and 6.

The results of the unconfined compressive strength tests

on the air-entrained speolmens are summarized in Table 7 and

presented 1n Figure 7.

Specimens treated with o, 5, and 10 percent of lime were

prepared in duplicate and then treated with 7 drops of air

entraining agent. The first of these samples was tested im-

mediately after curing, while the second was tested after

5 cycles of freezing and thawing. The results of these tests

are summarized in Table 8 and presented in Figure 8. The

secant modulus of all the air-entrained specimens was deter-

mined and presented in Tables 9 and lo. The quantity of

31

air present inside each specimen after treating it with

epeo1t1o amounts of air entraining agent was determined

and is shown in Table ll.

32

fable 5. Unconfined Compressive Strength (psi) of Olay-Lime Mixture, After Ouring, Freezing and Thawing, and Kept in a Moist Roo~.

Ozoles of Faezing !nd Th1wing !!f!ZI in I Moi d Room Lime ~

0

5

10

15

20

Q J io 79.2 11.0 10.3 62.a 18.2 10.3 65.8 11.1 10.5 69.3 Avg. 13.4 Avg. 10.4 Avg.

60.5 51.3 42.2 51.4 95.8 loo.o

loo.a 85.3

143.1 109.7. Avg. 66.2 Avg. 67.6 Avg.

166.o 143.o 126.8 169.5 149.0 139~5 203.0 174.8 159.0 179~5 Avg. 155.8 Avg.141.8 Avg.

184.o 173.o 169.o 200.0 180.0 185.5 206.5 195.0 175.5 196.8 Avg. 182.7 Avg.177.3 Avg.

200.0 185.0 188.5 183.5 172.6 169.5 199.0 180.0 175.0 194.2 Avg. 179.2 Avg.177.7 Avg.

10 57.2 47.0 52.2 52.l Avg.

133.0 76.5

112.5 107.'3 Avg.

179.0 175.5 192.5 182.3 Avg.

203.0 213.0 21:5.0 209.7 Avg.

208.5 200.0 198.o 202.2 Avg.

•

33

Table 6. .Secant Modulus of Olay and L1me Mixture, After Curing, Freezing and Thawing, and Kept 1n a Moist Room.

O;toies of freezing =d T~wing Dn.t:a in a Moist Room Lime. ~ 0 s 0 10

854 281 241 925 0 870 338 224 860

755 311 428 976 826 Avg. 310 Avg. 298 .Avg. 920 Avg.

7600 2430 2880 7350 5 5330 1740 1450 5430

8050 4800 4680 5370 6993 Avg. 2990 Avg. 3003 Avg. 6050 Avg.

9330 5030 8075 8389 10 9520 9380 7150 12400

11400 10900 6385 9000 ia·oe~ Avg. 8437 Avg. 7203 Avg. 9927 Avg.

10400 8100 6850 8150 15 6240 4600 10350 9985

7230 5050 7220 7470 7957 Avg. 5917 Avg. 8140 Avg. 8535 Avg.

6980 5120 7400 4190 20 8580 6440 6850 5085

3970 4210 4500 5550 6510 Avg. 5257 Avg. 6250 Avg. 4942 Avg.

34

220 i

o / -- 1~~ lime 200~-- I I

~ t A -- --- -

180K I -------_!· • -------::;- ~ ·--- l rJ! 11

I ., -· . . . . .. .! ···-··· -· .. ·-·· -- -·-i r . . 20~ l~me 0

------~-j

0

m b .___ ; ~· lOtv me : 16l . I ---·-:--:- ./ I___ --~ 11 t0 140X_____ c. ' -~ ~ . A

~ I ~ 120 . 1 m lOOJL.,_

E I ', ~ )t .... ! I-

E! 80 _ '....._ -· l I 0 • ........ I I

0 --- I I -! ---------

---- -~

5~ lime

---40

.- 0%!1ime I I

20

o~~__._ ____ .:_ __ __._ ____ ..__ __ __._ ____ ..._ __ _._ ____________ ~ 0 5 10

Freezing and Thawing Cycles

Figure 4. Compacted strength - Freezing and Thawing Cycles Relationship of Olay-Lime Mixture.

-...-4 m p, -m m CD J-4

tl • ~ • ~

~

.d

.p ~ i::: CD ~

"" Q)

> .,..f Ol I'll Cl> f..i p. a 0

0

'd Q) s:::I .rt ft..i i::: 0 0 s:l

::=>

220

200

180

160

140

120

100

80

60

40

20

I 0

10 Days 1n Moist Room ' \ ....... ------------___ \ '~ ./ After .. / ••••"''" •••••••••• .. - --auring_~ __ , .v·" ......

lo cycles F &T ·-- /r. - --:: -o- - ---•• -~ +' ....... ~-~+ .,,.. ~t»~ ~

5 Cycles F. & T.

+"' .,.,-1 _,++ , .. _"'.,+ ; ;

+"" , '"' , , ;

+ / -... ~ ,, ........ " /

.·+'t' y

l~'.tr~ ,o ~ / .

- - I· ,,._ \ ..... "' / .~~ I

,;.- I i· I

+ .. , I

· ... 7+"'""'" _; /.

5 10 15 20

Lime (percent by dry weight)

Figure 5. Compacted Strength - Lime Relationship of Clay Soil.

l..J,I \J1

36

220 --- ;-- 15% lime

·········· _f_ .;-::.?:0% lim.~ ...... . 200E----==~·~·-~·==-=-=-=-=-::_:_~.:.:.:~===-_l.~~~~-----~-1

-

~ 180~--r--10% lime --- --- --_--.

m p. -.d 160 --

~ Q) 140 ----""' ~ : 120 --- r- 5% lime '" CT.I ID CD ~ p.. e 0 0

'd Q)

R '" ~ i:I 0 0

~

- -- ------ __ t_ __ ---- -- --- ---100 ~---- -

1

80 t____ .r--o % lime 601- - - - - J ---r--- - ----- ----·---i ~~~~-

40 ~--

i 20 ~-­

! !

o~--------------------------------------------As Cured 10 days in moist room

Figure 6. Compacted Strength - Lime Relationship of Clay Soil After Ten Days in a Moist Room.

37

fable 7~ Unoonf1ned Oompressive strength (psi) of .Air-Entrained Olay-Lime Mixture After Curing and Five Cycles of Freezing and Thawing

time No. of 5 Oyoles or Freezing a= Drops ? Dws Ouring and Thawing

4 60.2 22.9 7 74.5 26.5

0 10 56.9 21.0 15 48.2 18.4 20 43.8 17.6

4 105.5 76.8 6 116.o 76.3

5 8 115.0 81.9 10 101.5 75.2 12 103.0 67.4

4 157.5 109.7 7 167.5 112.0

10 10 isa.o 99.5 15 155.5 101.0 20 151.0 100.2

170

160

150

140

-130 .... ID p. - 120

.c.t ~ ~ 110 ,_. Ii;

CD 100 > .... m m 90 Q) ,_. A a 0 80 0

"d Q) s:I 70 .....

\...! ~ 0 () 60 &

50

40

30

20

,; ,; '

,;

i .. o- ... .. '

38

' ' -·---- , j- - ----

,~ ,, ' I

0 ' ....... -- -- -------------\. -- 10%

i lim~ - 2 days curing

. _ ·- 1- :~ 5%1

lime - 2 days curing

, '*Ji':...._ r- -10% lime - 5 cycles F&T /1' ... . !'

.~-- - -o,, ~ ·,~ ,..o . ... "" .

, I ' ' -:*" ... , ·,~ I .. .:_ ...... , I

I o ... - --- - -""::" - _o - - - - - - - - - -

~•-·>~ ·--- -

0 2

Figure 7.

I •

0%

....,... . t

4

i r . - 5% lime - 5 cycles F&:T

.,

lime - - ..J 2 days curing

I I

r- 0% lime I

6 8 10

.""*-.... ., . ...... ........ . -

- 5 cycles F&T !

12 14 16 18 No. of drops added to two specimens

Effect of Air Entraining Agent on Compressive strength.

20

39

Table 8. Unconfined Compressive Strength (:ps1) of Olay-Lime Mixture Treated with Seven Drops of Air-Entraining Agent Per Two Specimens Batch.

Lime No. of 5 aYcles of Free#ing i DJYpS 2 Dqs Ourlng and TJ.ut.wing 0 7 69.3 31.2

5 7 115~0 65.2 lo 7 165.5 131.5

160

140

120

100

80

60

40

20

40

i

i I :

--- --+~-~s~u~led----~--~---·--- /////

I / , I/ i /

I i / ·----+---·-------+---· ------------ --·+----i I~ i

/ /

,,.,.,. ,,.,.,. ,5 Cycles / i of F&T

,,.,.,./ I ----·"-/ -·-··---· ·- +----------

i . - --- --. --r-- -------·----------

' '

OL-~...1-~...i...~.....1..~---1~--:~~..._~...i...~.....i..~--~--:-O 5 10

lime percent by dry weight

Figure 8. Effect of Seven Drops of Air Entraining Agent on Compressive Strength.

41

Table 9. Secant Modulus of Air .Ent rained Olay-Lime Mixture .After Curing end Freezing and Thawing.

time No. of 5 Oy'oles of 7reez1ng 1! Drone 2 D~te Ouring and Thawing

4 818 428 7 822 496

0 10 1300 537.6 15 1125 362 20 1210 440

4 4950 4300 6 4680 3510

5 8 5420 :5840 10 4410 3140 12 4830 3160

4 6275 4400 7 6200 3420

10 10 5800 2000 15 6050 4550 20 8395 3100

42

fable 10. Secant Modulus of Air-Entrained Ola7-L1me Mixture Treated with Seven Drops per Two Specimen Batch.

Iii.me :No. ot 5 Oyoles of Freezing ~ Drous 2 Days Curing and 1'haw1pg

0 7 1645 1075

5 7 6450 1835 10 7 4200 6175

43

Table 11. Quantity ot Air in Specimens Treated with Specific Number of Drops of Air-Entraining Agent.

Lime I lo. or drops Percentage of air

0 2.2 4 2.7 5 3.8 0

10 4.:3 15 4.4 20 5.3

0 3.0 4 3.4

5 6 5.2 8 6.6

10 6.7 12 1.1

0 2.1 4 2.9

10 7 3.1 10 3.6 15 3.8 20 4.5

44

DISCUSSION

Atterberg_ Limitg

Results of the liquid limit experiment at different per-

oentages of lime (Figure 2) indicate that the liquid limit

was inversely related to percentage of lime up to the ten

percent level, which verifies the results of Karabulut (5)

and Kotehne (19). However, when the lime concentration in-

creased beyond ten percent, the liquid limit was found to

increase rather than decrease, a result that has not previous-

ly been verified. On the other hand, the plastic limit was

found to increase with the increase in concentration or lime

within the limits used in this experiment. These results

are 1n complete agreement with those obtained by Yoder (14),

Karabulut (5) and Kotehne (19), As a result of this varia-

tion of the liquid and plastic limit, the plast1o1ty index

was found to decrease between O and 10 percent lime while it

increased above that lime concentration.

Aiz. Density Test

Results of dry" density tests, presented in Figure 3, show that the maximum densities decreased and the optimum

moisture contents increased with the increase in percentage

ot lime added. These results are in complete agreement with

those obtained by Yoder (14) and others.

45

!!.!: Ent ra1nm'ent

The results of the comparison of the unconfined com-

pressive strength of air-entrained clay-lime mixtures atter

curing as wall as after five oyoles of freezing and thawing

show that there was no gain in strength due to the air en-

training agent. Figure 1 shows that the drop in percentage

or strength after five cycles of freezing and thawing was

greater in the specimens with zero percent of lime. J'igure

7 also shows that the maximum strength of the clay-lime mix-

ture was obtained by using seven drops of air-entraining

agent. Figure 8 shows the unconfined compressive strength

ot olay'-11me mixture specimens molded with seven drops of

air-entraining agent. Those specimens which were tested aa

cured were found to be linearly related to the lime concen-

tration.

Five and Ten Oroles £!. Freezing .i!l!!, Th1wing

The comparison of the unconfined compressive strength

of the specimens after five and ten cycles of treez1ng and

thawing among the various combinations of clay-lime mixtures

is shown in Figures 4 and 5. Table 12 shows the percentage

rise in strength of. speoimens subjected to five and ten

cycles of freezing and thawing at different lime concentra-

tion. Examination of Table 12 shows that the percentage

rise 1n the strength increased with the increase in lime

concentration for both t1ve and ten cycles of freezing and

46

Table 12. E.ffeot of Lime on Oompreosive Strength.

% tncrease in St rengSJl ( pe rce:q,t)

L1me 5 CJtoles 10 Qycles

0 0 0

5 393 550

10 1065 1265 15 1260 1600

20 12::50 1610

thawing. However, this percent increase in the strength was

found to be higher for the ten oyoles of freezing and thawing

than that for five cycles. .Also shown is that the maximum

peroent rise in the strength was found to be between five and

ten percent of lime for both five and ten oyolea.

Results presented in Figure 5 show that the 1norease in

the concentration of lime resulted in the increase in strength

of the clq-11me mixture for different methods ot treatment.

This figure also shows that maximum strength was obtained while the specimens were treated for ten days in a moist room.

The greater strength for all different types of treatments was

estimated to be at a lime concentration of about 17 percent.

Table l} summarizes the percent drop in strength af'ter five

and ten oyoles of freezing and thawing for all speoimena

tested. Examination of this table 1nd1oates that the percent

47

fable 13. Effect of Freezing and Thawing Cycles on the Strength of Olay-Lime Mixture.

Lime ~ F!rst DeoI!l\ie in st ren~h i ;eercent l

Five gyo~es Second 5 O;ycles First io O:roles

0 ao.s 4.5 85.0

5 39.7 -1.3 38.4 10 13.2 7.8 21.0

15 1.2 2.7 9.9 20 1.1 o.e 8.5

drop in strength for the first .five cycles of freezing and

thawing was much higher than that for the last f1ve cycles

of freezing and thawing.

I!!'!. !W, 1!1 A Mo! et l2.2JI Results of the unconfined compressive strength for speci-

mens treated ten dqs in a moist room were presented in Figure

6. This figure shows that strength was affected b1 the lime

conoentrat1on. Furthermore, in a moist room speoimens with

a high lime oonoentration were found to gain more strength

than those with a lower lime concentration. These results

are summarized in fable 14. This seems to indicate the

possibility of the moist environment having some effect on

the specimens, despite the faot that they were wrapped and

sealed in aluminum toil.

Table 14.

Lime %

0

5

10

15 20

48

Effect of Moist Room on Compressive strength ot Olay-Lime Mixture.

Ten D~vs in a Decrease fnorease &! Oure4 Mo1 st · Room in ~ in 1

109.7

179.5 196.8 194.2

107.3 182.3

209.7 202.2

2.2

49

OOMOLUSIONS

l. Mo1eture-dens1ty relationship was affected by the lime

admixture. Maximum dry density was found to deoreeee

while the optimum moisture increased.

2. The addition of lime changed the plasticity properties

of the soil as followss

a. Increased the plast1o limit

b. Decreased the liquid limit with the increase of lime up to ten percent, above which it started 1noreasing

o. Decreased the plasticity index.

3. The compressive strength of clay-lime mixture increased

with the increase in lime oonoentrations within the

l1m1t s tested in this study.

4. The maximum percent increase 1n the strength of cla;r-

11ine mixtures was found to occur at about ten percent

lime.

5. About 17 percent lime was estimated to give maximum

strength.

6. The decrease in strength due to freezing and thawing

was greatest during the !1rst five oyoles.

7. Seven drops of air entraining agent gave maximum

strength of the a1r-entra1ne·d speo1mens.

50

BIBLIOGRAPHY

1. Miller, Eugene A,,. and Sowers, George P'., ttThe strength

Oharaoteristios of Soll-Aggregate Mixtures. 11 Highway

Research Board Bulletin 183, PP• 16-32, 1957.

2. Portland Cement Aesoaiation So11 Primer, pp. 35-49,

1956. '.5. McDowell, o., "stabilization of ,Soils with Lime, Lime-

Fl;rash, and Other Lime Reactive Materials.'' R1ghwq

Research Board Bulletin 231, pp. 61-63, 1959.

4. Taber, stephen, ''Freezing and Thawing of Soils as Fa.otora

in the Destruction of Road Pavements.'' Public Roads,

Vol. 11, No. 6, August 1930.

5. Karabulut, o., "Effect of Freezing and Thawing on Un-

confined Oompresslve strength of Lime stabilized Soils.~

Master of Science Thesis, Virginia Polytechnic Institute,

Department of 01v11 Engineering, 1963.

6. Powers, T. o., "A Working Hypothesis f'or P'urther studies

of Frost Resistance o:t Oonorete." Proceedings, American

Oonorete Institute, Vol. 41• pp. 245-272, 1945.

7. Hoover, J. M., Handy. R. L., and Davidson, D. T., HDura-b111ty of So11 ... L1me-Flyash Mixes Oompacted Above standard

Proctor Density. tt Highway Researoh Board Bulletin 193,

pp. 1-ll, 1958.

51

8. Oorte, A. E., ''The Frost Behavior of Soils. I. Verti-

cal Sorting." Highway Research Board Bulletin 317,

pp. 9 - 34, 1961. 9. Anday, M, o., ttAooelerated Our1ng For Lime-Stabilized

Soils.~ H1ghw33' Research Board Bulletin 304, pp. 1-13,

1961.

10. Whitehurst, E. A. and Yoder, E. J., "Durability Tests

on Lime stabilized Soils.'' Highway Research Board Pro-

ceedings, Vol~ 31, pp. 529-540, 1952.

11. Baig, M. N., 0 0.BR and Unconfined Oompressive Strength

Tests on a Lime stabilized Clay Soil." Master of Science

Thesis, Virginia Polytechnic Institute, Department of

Oiv11 Engineering, 1962.

12. Broberg, R. F., 11 L1me 111 Oement a,nd Lime-Cement stabili-

zation of a Olay Soil." Master of Science Thesis, Vir-

ginia Polytechnic Institute, Department of Oiv11 Engi-

neering, 1962.

13. Herrin, M., and Mitchell, H., ~Lime-Soil Mixtures."

Highway Resea.roh Board Bulletin 304, pp. 99-138, 1961.

14. Yoder, E. J., Principles£..!. Pavement Design. Ohapter

10, 11 So11 Stabilization.'' Wiley and Sons, pp. 255-266,

1959. 15. Hilt, G. B., Davidson, D. 1., ~Lime Fixation in 0187

Soils.'' Highway Research Board Bulletin 262, pp. 20-32,

1960.

52

16. Shelburne, T. E., 11 Spr1ng Break-Up studies of Virginia

Pavements~" American Road Builders' Association Bulle-

tin 151, 1948. 17. Johnson, A. w., "Frost Action in Road and Airfields."

A Review of Literature, Highway Research Board Special

Report No. 1, 1952.

18. Lu. L. w., Davidson, D. T., Han<17, R. L., and Laguros,

J. G., "The Oalcium-Ma.gnesium Ratio in Soil Lime stabi-

lization." 11ghwaJ" Research Board Prooeedings, Vol. 36, pp. 794-805, 1957.

19. Kotehne, E., t•oompar1son of Lime and Portland Oement

Stabilization of Silt and Olay Soils. tt Master ot Science

Thesis, Virginia Pol7teohnic Institute, Department of

Civil Engineering, 1963.

20. Walker, R. D., and Karabulut, C., ••Effect of Preezing

and Thawing on Unconfined Oompress1ve .strength ot Lime

stabilized Soils." Presented at Annual Meeting of

Highwa¥ Research Board, Washington, D. o., 1964.

The vita has been removed from the scanned document

ABSTRACT

EFJ'EOT OF FREEZING A.ND THAWING ON UNOON:PINED OOMPRESSIVE STRENG!lH OF OLAY LIME MIXTURE WITH AND WITBOU!

AIR EN'.f R.A.INING A.GENT

The main objective of this stud; was twofold:

1. To determine the effect of freezing and thawing on

the loss in strength of lime-soil mixture.

2. To investigate the effect ot the addition ot an

a1r entraining agent on the freezing and thawing durability

of lime-soil mixtures.

For the first part, twelve specimens were prepared for

each of o, 5, 10, 15 and 20 percent combination of 11me-olq

mixture, giving a total of 60 specimens.

for the second part, twelve specimens were prepared for

eaoh of o, 5 and 10 percent of lime, giving a total of 36

specimens. Those containing five percent were treated with

4, 6, a, 10 and 12 drops of air entraining agent for eaoh

two specimen batch, while those containing O and 10 percent

were treated with 4, 7, 10, 15 and 20 drops. All specimens

were wrapped with aluminum foil and immediately sealed with

paraffin and cured for two dqs at 120°r. Control specimens

were plaoed in the 70°F environment for ten days while com-

panion specimens underwent five and ten oyoles ot freezing

and thawing.

The results of this study 1nd1oated the following r

1. Addition of lime increases the strength of 0197

soil.

2

2. Maximum percent increase 1n durability of ola;r

soil found to ocour with addition of ten pero.ent

lime.

'3. The decrease in strength due to freezing and

thawing mainly occurred during the first five

oyclee. 4. Seven drops of air entraining agent gave maximum

strength of air entrained specimens.