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1985

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DRDA Project No. 388803

Use of Fly Ash in a Highway Shoulder Base Course

DONALD H. GRAY Professor of Civil Engineering

EGONS TONS

Professor of Civil Engineering

and

MOHAMMAD RAZI Research Assistant

June 1985

Consumers Power Company

Electric Power Research Institute

Michigan Department of Transportation

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THE UNIVERSITY OF MICHIGAN

COLLEGE OF ENGINEERING

DEPARTMENT OF CIVIL ENGINEERING

USE OF FLY ASH IN

HIGHWAY SHOULDER BASE COURSE

Donald H. Gray Professor of Civil Engineering

Egons Tons Professor of Civil Engineering

and

Mohammad Razi Research Assistant

Project Sponsored by:

Consumers Power Company In Cooperation with

Electric Power Research Institute EPRI Project RP 2422~7

Administered through:

DIVISION OF RESEARCH DEVELOPMENT AND ADMINISTRATION

THE UNIVERSITY OF MICHIGAN

June 1985

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ACKNOWLEDGEMENT

This research was sponsored by the Consumers Power Company of

Michigan.

The authors wish to acknowledge the assistance of Mr. William

H. Berry, Jr., Consumers Power Company; Mr. Ulrich w. Stoll,

Stoll, Evans, Woods and Associates; Mr. Michael J. Adams, Michigan

Ash Sales Company and number of individuals from the Dundee Cement

Company.

The participation and interest in the research project on the

part of the following organizations are also acknowledged:

Electric P01~er Research Institute, Michigan Dept. of Natl.

Resources, Michigan Dept. of Transportation, Michigan Energy

Resources Research Assoc., Detroit Edison Company, and GAI

Consultants, Inc.

DISCLAIMER

The opinion, findings, and conclusions expressed in this

publication are those of the authors and not necessarily those of

the sponsoring agencies.

Consumers Po1~er Company does not warrant the accuracy of this

report nor the correctness nor validity of the conclusions. Any

use of this report or reliance thereon shall be solely at the risk

of the user. This disclosure shall be included in any and all

reproductions of the report or portions thereof.

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SUMMARY

The engineering and index properties of cement stabilized fly

ash mixtures were determined experimentally in the laboratory.

The mixtures were evaluated in order to determine their likely

behavior and performance as pavement base courses. A fly ash from

the D.E. Karn power plant in Essexville, Michigan, was selected

for the study. This ash was tested in both a dry (hopper stored)

and wet (ponded) condition. The ponded fly ash was air dried

before testing. Only one cement (Type I) was used in the study.

Engineering properties of interest included gradation,

specific gravity of solids, moisture-density relationships, on ash

and ash-cement mixtures, frost heave, durability, and unconfined

compressive strength. Test results showed that the addition of 12

percent cement (dry weight of solids) to the fly ash followed by

compaction at optimum moisture content to at least 95% relative

compaction based on the Modified method (ASTM Dl557) produced a

satisfactory mixture. The error tolerance or performance loss

sensitivity of this mixture was evaluated by investigating the

influence of changes in molding water content, compactive effort,

and mixing procedure.

Mixing procedure and the resulting degree of mix uniformity

profoundly affected the strength, durability, and other

engineering properties of compacted, cement stabilized fly ash.

This consideration alone will critically affect the successful use

and performance of compacted, cement stabilized fly ash in field

applications.

• Based on this study a specification was written for placement

of a cement stabilized, compacted fly ash base course in the

field.

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INTRODUCTION

Fly ash is a by-product of the combustion of pulverized coal

in electrical power plants. The United States currently produces

over 50 million tons of fly ash per year. In the past few decades

this residual product has become increasingly expensive to dispose

of, in addition to creating environmental problems associated with

its disposal. It is apparent that continued effort is necessary

to develop new applications and expand existing ones in order to

eliminate disposal problem and eventually turn a costly liability

into an income producing asset.

Fly ash has been used in highway construction for a long

time. However, the quantities consumed have lagged far behind it's

potential usage in this area. Fly ash has been used successfully

in bituminous concrete mixes as mineral filler and for base,

sub-base, and surface courses. It has also been used occasionally

in highway embankments and fills.

One area in highway construction where fly ash is potentially

usable in high volume quantities is in pavement base courses.

Mixtures of lime and/or cement plus fly ash have been used in

combination with aggregate in pavement base courses for many

years. In contrast to these mixtures, it is possible to use

compacted cement stabilized fly ash by itself as a pavement base

course. Use of fly ash in this manner is undeveloped in the

United States and is the subject of the research reported herein.

Engineering properties and performance of compacted, cement

stabilized-fly ash mixtures were determined experimentally using a

number of standard laboratory tests such as specific gravity,

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moisture-density relationship, unconfined compressive strength,

durability (vacuum saturation), and frost heave.

The primary objective of this study was to investigate the

feasibility of utilizing cement stabilized fly ash mixtures as a

highway shoulder pavement base course.

PURPOSE OF RESEARCH

The main objectives of this research are as follows:

1. To demonstrate that aggregate-free, cement-stabiljzed,

conditioned, high-carbon fly ash is a structurally

and environmentally acceptable base material for

highway shoulder construction.

2. To determine an optimum amount of cement in a

cement stabilized fly ash mix and mixing/compaction

procedures that would result in satisfactory strength,

durability, and economy when used as a highway

shoulder pavement base course •.

3. To write a specification for field trial

installation of a fly ash-cement base course.

LITERATURE REVIEW

FLY ASH PRODUCTION

Fly ash is a powdery, largely inorganic by-product of the

combustion of pulverized coal in electricity generating power

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plants. It is removed by mechanical collectors or electrostatic

precipitators as a fine particulate residue from the combustion

gases before they are discharged into the atmosphere (1). Fly ash

should not be confused with bottom ash, a granular by-product

which drops to the bottom of the furnace during the burning

process, and comprise up to 30 percent of the total ash produced

(2). Rate of production of fly ash in the United States has

increased from 17 million tons in 1966, the first year that data

was taken, to a current production of over 50 million tons

(2,3,4).

Despite the increased efforts to develop new uses for fly ash

in the past several years, the rate of utilization has not

approached the rate of production yet. Up to date, less than 20

percent of fly ash produced is used in some manner other than

landfilling and dumping. But fly ash disposal creates serious

land use and environmental problems which contribute to escalating

disposal costs. Based on a 1983 study (5) fly ash disposal cost up

to $10 per ton. Therefore, the need to utilize fly ash on a

large-tonnage bases becomes apparent when the volume of fly ash

produced annually is considered.

FLY ASH CHARACTERISTICS

Fly ash consists of very fine particles, the majority of

which are glassy spheres, with the remainder being crystalline

matter and carbon. The chemical and physical characteristics of a

fly ash are a function of several variables such as:

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1. Coal source;

2. Degree of coal pulverization;

3. Method of burning;

4. Method of collection and storage.

Due to these factors fly ash displays a high degree of

variability, not only between power plants but also within a

single power plant. However, more than 80 percent of most fly

ashes consist of chemical compounds and glasses formed from (1,6):

Silica, as Si02

Alumina, as Al 2o3 Iron Oxide, as Fe2o3 Calcium Oxide, as CaO

Magnesium Oxide, as MgO

Plus smaller quantities of various other oxides and alkalies such

as Tio2 , so3, Na2o, and K2o. Unburned carbon, c, is also present

in varying amounts.

The water soluble content of bituminous coal fly ash ranges.

from 1 to 7 percent. Lignite fly ash has slightly higher water

soluble content. The leachate from fly ash is usually alkaline

with PH ranging from 6.2 to 11.5. The leachate contains

principally calcium and sulphate ions, with smaller quantities of

magnesium, sodium, potassium, and silicate ions (6,7,8,9).

It is important to determine the chemical composition and

physical properties of the fly ash being used for the following

reasons (4,6):

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1. A high carbon content will inhibit the hardening

mechanism of the ash, will generally lower the

specific gravity, will make the ash darker in

color, and will raise the optimum moisture content

for compaction.

2. A high calcium oxide (CaO) content will enable the

ash to self-harden when moisture is added.

3. In general, a high calcium oxide content creates an

alkaline leachate while a high iron oxide content

results in an acidic leachate.

Physically, fly ash consists of finely divided,

noncombustible glassy particles which are typically spherical in

shape. A small portion of these particles are thin-walled hollow

spheres (10). The size of particles range from 1 m to 100 min

diameter for the glassy spheres, with an average of 7 m, and from

10 m to 300 m in diameter for the irregularly shaped carbon

particles (11). The specific gravity of fly ash varies from 2.1

to 2.6 with an average of 2.4 for most u.s fly ashes (6, 12).

Fly ash is a relatively uniformly graded material with

predominantly silt-sized particles. Its grain-size distribution

curve falls within the conventional limits for frost susceptible

soils. Another measure used to indicate the fineness of fly ash is

the Blaine fineness. This usually ranges from 1700 cm2/gm in fly

ashes from mechanical collectors to 6400 cm2/gm in fly ashes from

electrostatic precipitators (6).

The maximum dry compacted density of fly ash typically ranges

from 70-105 pcf (4,6). Hopper and silo fly ashes tend to have

sharp, well defined points of maximum dry density and optimum

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moisture content, while ponded ashes tend to have flatter

moisture-density curves.

FLY ASH PROPERTIES AND UTILIZATION

Fly ash is a well known and commonly used pozzolan. Its

pozzolanic nature is a unique property which makes fly ash a

valuable engineering material. The American Society for Testing

and Materials (13) defines pozzolan as "a siliceous or siliceous

and aluminous material which in itself possesses little or no

cementitious value, but will, in finely divided form and in the

presence of moisture, chemically react with calcium hydroxide to

form compounds possessing cementitious properties". Fly ash, an

artificial pozzolan, is very similar to the volcanic ashes

(natural pozzolan) used in the production of the earliest known

hydraulic cements more than 2,000 years ago - near the small

Italian town of Pozzouli, which later gave its name to our modern

day pozzolan's ( 14) • The ancient Roman buildings were built from

pozzolanic materials, and some of the ruins still stand today.

Currently, there is no quick and reliable test for predicting

the degree of pozzolanic activity in a fly ash. The rate and

extent of the reaction is a function of several factors (15,16):

1. Quantity of stabilizer (free lime or cement)1

2. Amount of silica (Si02 ) and alumina (Al 2o3)

in the fly ash1

3. Compacted density1

4. Age (curing period)1

5. Fineness of the fly ash1

6. Curing temperature1

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7. Presence of adequate moisture; and

8. Amount of carbon in the fly ash.

The greater the items 1 through 6, the greater the pozzolanic

reaction as measured by unconfined compressive strength. For item

7, an extreme in either direction has an adverse affect on the

reaction. In item 8, the higher the carbon content, the lower the

reactivity.

Where available fly ash has been used in the manufacture of

cement and concrete because of its pozzolanic properties. So far

this use has constituted the largest market for this material in

the United States. However, ashes with high carbon content are

not suitable for this application.

The pozzolanic properties of fly ash have made it attractive

for soil stabilization and various phases of highway construction.

Fly ash is an excellent material for fills and embankments due to

its pozzolanic properties, availability in developed areas,

relatively low unit weight, and high shear strength, particularly

when placed over weak subgrades where heavier materials could

cause excessive settlement or .failure (4,6). Mixtures of lime and/

or cement plus fly ash in combination with aggregate have also

been used for base and subbase course materials in roadways for

many years (17,18,19,20).

CEMENT STABILIZED FLY ASH BASES

Cement-stabilized aggregate-free, fly ash base courses

represent a unique application of fly ash in that the fly ash

. itself serves both as a pozzolan and an aggregate. The fly ash

and stabilizer function mechanically much the same as a

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fine-grained soil-cement except that the natural pozzolanic

reaction between the fly ash and the cement continues to produce

an increase in strength over a long period of time, thereby

increasing the durability of the base course (6). Although many

Class F (Bituminous) fly ashes posses self-hardening properties,

the strength developed within a reasonable time period is

generally not adequate for pavement application. Also, since most

base courses are constructed within the frost zone in most regions

of the United States, both load-bearing capacity and frost

resistance are required. Hence, this makes the addition of a

stabilizer necessary. Stabilized base courses are normally covered

with a bituminous wearing surface to protect them from water and

abrasion as well.

In cement-stabilized fly ash, the cement hydrates upon

contact with moisture producing its own cementitious compounds as

well as releasing certain amounts of lime which then react with

the fly ash in a pozzolanic manner. In addition, certain chemical

and physical characteristics influence the degree to which a fly

ash can react with a stabilizer. For example, the presence of

silica, alumina, and calcium oxide in large quantities enhances

the reactivity of a fly ash. On the other hand, high carbon

contents are detrimental to the pozzolanic reaction, and require

greater amounts of stabilizer. A 7 to 10 percent carbon content in

a fly ash is often considered an upper limit (21) for acceptable

behavior and performance in a structural fill or base course. On

the other hand, it is precisely these high carbon content ashes

for which it would be desirable to find and promote uses.

Although cement-stabilized fly ash pavements are relatively

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new in the United States, they have been used in Europe for more

than 25 years. Both Great Britain and France have adapted

specifications and established ready-mixed plants for

cement-stabilized fly ash bases (4,19). The European experience

and demonstration projects in the United States have shown that

cement-stabilized fly ash is a viable base course material. It

may be particularly attractive in locations where a source of fly

ash is available and supplies of aggregate are unavailable or

expensive.

A project search conducted in 1984 (4) located 6 pavement

base courses constructed using fly ash, including 3 roads and 3

parking lots. The results of these field trails to date have all

been favorable. One of these projects includes the construction

of an access road and parking lot in Haywood, West Virginia, in

1975. Cores taken in 7, 90, 180, and 360 days yielded unconfined

compressive strengths of 566, 869, 872, and 925 psi respectively •

A visual inspection in May 1984 indicated only one crack running

across the width of the parking lot.

Design Criteria

The thickness design method for cement stabilized fly ash base

courses requires the mix be strong and durable (22). The most

practical method to date for determining durability is residual

strength after vacuum saturation (23). Three mix design criteria have

been adopted for cement-stabilized fly ash mixes:

1. The seven-day unconfined compressive strength of

the mix, when cured under moist conditions and at

70.+ 3°F (21 t 2°C), must be 400-450 psi (2760-

3100 KPa) for cylindrical specimens having a length

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to diameter ratio of 2:1.

2. The unconfined compressive strength of the mix must

increase with time.

3. Unconfined compressive strength after vacuum saturation

must exceed 400 psi.

Durability Eyaluation

Cement-stabilized fly ash pavements which will be subjected

to extreme service conditions should be tested for durability in

some manner. Dempsey and Thompson (24) developed a~tomatic

freeze-thaw testing equipment which accurately simulates field

conditions. Compressive strength after freeze-thaw cycling (5 or

10 cycles) is used to characterize lime and/or cement plus fly ash

plus aggregate mixtures. This method appears to be suitable for

fly ash-cement mixes as well.

The vacuum saturation test procedure proposed by Dempsey and

Thompson (23) is a rapid technique which only requires 1-1/2 hours

to complete compared to 10 days for the older method. Samples are

vacuum saturated and then tested in unconfined compression. The

justification for using the vacuum saturation procedure is the

excellent correlation between the compressive strengths of vacuum

saturation specimens and freeze-thaw specimens. The revision of

ASTM C 593 currently approved includes the use of the vacuum

saturation for durability evaluation purposes. The minimum

allowable compressive strength after vacuum saturation of lime

and/or cement plus fly ash plus aggregate is 400 psi (6).

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Frost Susceptibility

The grain-size distribution of most fly ashes falls within

the limits of frost susceptible soils. However, frost

susceptibility is also influenced by pore size, mineralogical

composition, strength, and permeability (25). Frost

susceptibility criteria have not been developed in the United

States for cement-stabilized fly ash in pavements. A procedure

proposed by the Road Research Laboratory in England (26) is based

on the amount of frost heave developed in a compacted specimen

when subjected to freezing conditions which simulate field

conditions. The criteria was adopted for 6-inch high samples

subjected to 250-hour test as follows:

1. Not frost susceptible if heave < 0.5 inches

2. Marginally frost susceptible if 0.5" < heave < .7"

3. Frost susceptible if heave > 0.7 inches.

The resistance to frost heaving can be improved substantially

through stabilization with cement. The amount of cement required

to prevent or reduce frost heaving to acceptable levels in several

studies, has varied from 5 percent to 15 percent (25,27).

Leachate from Fly Ash

Minimal leachate is generated from using fly ash as a

pavement base course for the following reasons (4):

1. The wearing surface placed above the base course

will be relatively impermeable and limit the amount

of infiltration. In addition, a proper crown on

the surface will assist in diverting thawater off

11

the road and into the adjacent drainage ditches.

2. Typical road design precludes the groundwater table

from coming in contact with the pavement system of

which the base course is a part. Therefore, no

source of water should be in contact with the fly

ash base course from below.

3. Proper drainage ditches will channel the runoff

4.

away and not provide a source for lateral seepage

through the base course.

The permeability of:

fly ash is very low

a compacted, cement stabilized

-6 (on the order of 10 em/sec);

hence, only small leachate quantities can be produced.

SUMMARY OF LITERATURE STUDY

The highway construction industry is potentially the largest

bulk user of fly ash in the United States. The most notable

property which makes fly ash attractive as an engineering

material in various applications of highway construction is its

pozzolanic nature, The most influential chemical constituents of

fly ash from an engineering view point are free lime (CaO) and

carbon (C). Free lime and carbon influence the chemical

reactivity, compaction and strength characteristics. Carbon is

detrimental to the engineering properties and behavior of a fly

ash. High carbon ashes are more difficult to use and require

greater amounts of cement stabilizers. Fly ash with large amounts

of free lime, on the other hand, tends to be very reactive and can

exhibit some degree of self hardening.

Cement-stabilized fly ash base courses are relatively new in

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the United States. However, European experience, and various

demonstration projects in the United States have shown

cement-stabilized fly ash to be a viable base course material.

The design criteria for cement-stabilized fly ash base courses

requires that the mix be durable. Present criteria include the

following:

1 • The seven-day unconfined compressive strength

of the mix, cured under moist conditions and

at 70 + 3°F, must be 400-450 psi.

2. The strength must increase with time.

3. Minimum strength after vacuum saturation must

be 400 psi.

Frost susceptibility criteria have not been developed in the

United States. According to British criteria, a material is

regarded as non-frost susceptible if the heave does not exceed 0.5

inches after 10 days. This criteria is based on simultaneous

exposure of 6-inch high samples to unfrozen water at their base

and freezing temperatures at their tops. Several studies have

shown than 5 percent to 15 percent addition of cement to fly ash

is required to reduce frost heaving to acceptable levels.

LABORATORY TESTING PROGRAM

The purpose of this phase of the work was to determine the

engineering properties and predicted performance of different

compacted cement stabilized fly ash mixtures, and to write a

specification for a field trial installation of a fly ash-cement

base in pavement shoulder construction.

13

WATER CONTENT DEFINITIONS:

Two water contents are encountered in this report, the

molding water content and the actual water content. The molding

water content(% of dry solids or the fly ash plus cement), is the

water content added to the solid material before mixing and

compaction of specimens. The actual water content (% of dry

solids), is the water content of a compacted specimen. As can be

seen from tables 5 and 6, the actual water contents are lower (1

to 3 percent) than the molding water contents. This is mainly due

t<• evaporation and loss of moisture during the mixing and

compaction process.

To develop moisture density curves (Figures 5 and 6), the

actual moisture contents were used to plot the curves. For the

rest of the tests in this report, the water content is the molding

water content.

MATERIALS AND PROCESS VARIABLES USED

The fly ashes used in this study were obtained from a single

power plant, but in two conditions, hopper (dry) and ponded. They

were obtained from D. E. Karn plant, Consumers Power Company,

Essexville, Michigan.

The cement used was Type I, supplied by Dundee Cement

Company, Dundee, Michigan.

In general, the following materials and variables were used

in this investigation:

One hopper fly ash (Karn Plant)

One ponded fly ash (limited testing, Karn Plant)

Three to five mixing water contents

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Four cement contents (6, 9, 12 and 15% dry wt.

of solids basis)

Several mixing procedures

Two compactive efforts (90 and 100% of maximum

dry density based on the Modified Proctor Test)

Four wait times between mixing and compaction

(0,1,2,3 hrs.)

One curing temperature (68F)

One curing moisture condition (100% RH)

Two curing times (7 and 28 days).

ASH TESTING

Index and engineering property tests were conducted on both

hopper (dry) and ponded ash from a single power plant source. The

following tests were conducted on these two types of ash:

1. Specific Gravity •••..••.•...•.•••..... ASTM D854

2. Grain Size Analysis ••••••••••••••••••• ASTM D442

3. Moisture-Density Relationship ••••••••• ASTM Dl557

4. Unconfined compression •••••••••••••••• ASTM D2166

5. Vacuum Saturation (Durability) •••••••• ASTM C593

6. Frost Heave .....•••..••.•••....••••..• BRL LR90

The engineering property tests (3-7) on compacted and/or

cement stabilized fly ash along with the material/process

variables are listed in Table 1.

SPECIMEN PREPARATION

Specimens for strength evaluation were made using a Harvard

3 miniature mold (Figure 1) with a volume of 62.4 em • The height

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of the specimens was 2.84 inches and the diameter 1.30 inches.

For frost-heave specimens the modified Proctor mold (ASTM Dl557)

was used which was 4.6 inches in height and 4.0 inches in

diameter. Before the actual test specimens were made, two

preliminary studies were conducted:

1. Calibration of the maximum dry density of specimens

compacted in the miniature mold with those

compacted in the larger modified Proctor mold. In the

modified Proctor test, specimen are compacted in 5

layers, with ~5 blows of a 10-lb hammer on each

layer. It was found that the miniature specimens

would have the same density as that of modified

Proctor specimens, if they are compacted in 5

layers and 35 blows per layer using a 1.13-lb

tamper.

2. Determination of the best possible and most

practical scheme. for mixing fly ash cement to

insure mixing thoroughness. The mix uniformity is

affected by dry or wet mixing, and mixing time (28).

A Hobart Mixer (Figure 2) was used in this study, and

the mix uniformity was measured and judged by the

unconfined compressive strengths of the specimens

after moisture curing for 7 days. It was found that

when fly ash and cement is mixed dry for 1 minute,

and then 3 minutes after the addition of water, the

mix will give the best results. The total mixing

time for all specimens was 4 minutes. Other mixing

procedures tried were: 2 minute dry mixing followed by

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2 min. of wet mixing, 4 min. of wet mixing, etc.

All specimens were moisture cured for 7 days

before testing in a 100% RH fog room. Some

specimens were cured 28 days to determine the

effect of time on strength development. Difficulty

during compaction was encountered with high moisture

contents. At high moisture contents (more than 1.5-2

percent above opt.), the mix is soft and spongy in the

mold and water seeps out from the base of the mold.

SPECIFIC GRAVITY MEASUREMENT (ASTM 0854)

The specific gravity is defined as the ratio of the dry

weight of a volume of fly ash particles to the weight of the same

volume of water at a given temperature.

About 50 grams of fly ash are placed in a volumetric flask

called a pyncnometer, usually 500 cm3 in volume. The air is

removed from the flask under a vacuum. By knowing the weight of

the solid in suspension, the weight of 500 cm3 of suspension and

the weight of 500 cm3 of distilled water at an equivalent

temperature, the specific gravity can be determined. Specific

gravity results obtained in the manner described are presented in

Table 2.

Occasionally some of the particles may have specific gravity

less than that of water and float. If a significant amount of fly

ash behaves this way, an alternative procedure using kerosene,

ASTM Cl88, can be employed.

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GRAIN SIZE ANALYSIS (ASTM D422)

Grain size analysis was performed to determine the proportion

by weight of the ash in different particle size ranges. For a

fine material such as fly ash a combination of sieve analysis and

hydrometer analysis must be used.

A sieve analysis was performed by passing a dried sample of

fly ash of 100 grams through a set of U.S. standard sieves, nested

in decreasing order of sieve openings and clamped in a mechanical

sieve shaker for a prescribed length of time. The sieves used

were numbers 30, 100, and 200. Since fly asn contains a

significant amount passing no. 200 sieve, the hydrometer analysis

was used in combination with sieve analysis. See Table l for

results of the gradation analysis using these combined testing

procedures.

MOISTURE-DENSITY RELATIONSHIP FOR FLY ASH (ASTM Dl557)

An impact method of compaction was used to determine the

moisture-density relationship of the fly ash. The impact method

uses a rammer of known weight falling freely through a known

distance to impart a compactive energy to the sample. The fly ash

is compacted at a particular moisture content in a mold of known

volume. In the modified Proctor test, the fly ash is placed in 5

layers and each layer compacted with 25 blows of the rammer. The

dry density of the compacted sample is determined from the total

weight, moisture content, and volume of the mold. This process is

repeated at different moisture contents until a moisture-density

relationship curve has been defined.

At high moisture contents, the fly ash became saturated and

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liquid tended to seep or bleed from the mold.

FLY ASH-CEMENT MOISTURE DENSITY (ASTM Dl557)

This test is basically the same as the moisture-density test

discussed previously. In this case, however, cement was added to

the fly ash and dry-mixed for l minute. Then, water was added and

mixing continued for an additional 3 minutes. The rest of the

test procedure is the same as before.

UNCONFINED COMPRESSIVE STRENGTH (ASTM D2166)

In an unconfined compression test, a cylindrical specimen

(2.84" high and 1.3" in diameter) of compacted material is loaded

to failure in simple compression without lateral confinement. The

• test is most suitable for cohesive materials. It is also useful

for evaluating fly ashes subject to pozzolanic hardening.

Specimens were loaded to failure at a rate of deformation of

0.05 inch/min.

VACUUM SATURATION (ASTM C593)

Fly ash-cement mixtures used as base course material may

suffer strength loss following freezing and thawing. This

strength loss is from excess water and deterioration of the

cementitious matrix. Vacuum saturation is a fast method to

determine durability (about 1.5 hrs.) as compared to the old

method of freeze and thaw testing which takes 48 hours per cycle

(5 cycles take 10 days). Studies have shown a good correlation

between strength after vacuum saturation exposure and freeze-thaw

test after 5 and 10 cycles. This test is now accepted by ASTM

(C593) as a durability indicator for fly ash and other pozzolans

19

for use with cement. The procedure is as follows:

Samples are cured for 7 days at 70 + 3°F

Each specimen after curing, is placed in a vacuum

chamber. A vacuum of 24 inches of mercury is

applied for 30 minutes to evacuate air from voids.

After deairing, the sample is flooded with water and

soaked for one hour at atmospheric pressure.

The sample is removed from the chamber, drained of

free water, and immediately tested for unconfined

compressive strength.

The minimum strength after vacuum saturation must

be 400 psi in order to meet durability

requirements.

FROST HEAVE (See Ref. 26)

When water freezes it expands. If unsaturated soil is

quickly frozen, the pore water will expand into the voids and

little or no overall expansion of the soil will occur. In some

soils, water is drawn up continuously through the capillary pores

and ice lenses form. These ice lenses may create a significant

increase in the soil volume, a process referred to as frost heave.

In the spring, the soil thaws from the top down. Because the

underlying soil is frozen, the water can not drain and the

saturated surface soil loses its strength. For significant frost

heave to occur, several conditions must be satisfied (4). First,

there must be a source of water to feed the ice lenses, second,

the soil must contain sufficient fine particles to provide upward

capillary movement of water. Third, the soil must be permeable

20.

enough so that the water can flow upward at a fast enough rate to

nourish the ice lenses. Untreated, fly ash is especially

susceptible to frost heave. Studies have shown that addition of 5

to 15 percent of cement significantly reduces frost heave (26,27).

The frost heave test (26) basically consists of exposing the

top surface of 6 inch high compacted sample to a temperature of

-17°C while the bottom surface rests on a porous ceramic disc in

contact with water at +4°C. The volume expansion or frost heave

is measured under these conditions during a period of 250 hours.

The criteria adapted by the British Road Research Laboratory are

as follows:

1. Heave less than 0.5 inches in 250 hours -

not susceptible.

2. Heave between 0.5 to 0.7 inches-

marginally susceptible.

3. Heave greater than 0.7 inches-

very susceptible.

In this study, specimens were made in a modified Proctor mold with

a height of 4.6 inches as opposed to 6 inch specimens used in the

British test. A test with 4.6-inch high specimens should be more

severe because the freezing front will contact the capillary water

a little sooner and because the capillary water has less distance

to travel. Specimens were moist cured for 7 days and then placed

in a frost cabinet for 10 days. The frost heave test set up is

shown in Figure 3.

21

RESULTS

This section includes the results of index and engineering

property test conducted on both hopper (dry) and ponded (wet) fly

ash from a single power plant source. Only a limited number of

selected tests were performed on ponded ash. All mixes were mixed

for a total of 4 minutes. Cement and fly ash were mixed for 1

minute in dry condition, then water was added and mixing continued

for 3 more minutes.

Specimens were made using a Harvard miniature mold which was

calibrated with the Modified Proctor to achieve the same compacted

densities. Frost heave specimens were made using Modified Proctor

~· equipment. See Figure 1 for Harvard Miniature and Modified

Proctor equipment respectively. Specimens were moist cured for 7

days (some for 28 days) before testing.

CHEMICAL AND INDEX PROPERTIES

The results for chemical analysis, specific gravity, and

grain size distribution of fly ash are presented in Table 2.

Chemical analysis shows a high carbon content o~ 7.3 pe~gent in

the hopper ash, and a low lime content (CaO) of 1.07 percent.

Specific gravity of the hopper ash is low, 2.22. Grain size

analysis shows that ponded ash is coarser (see Figure 4) and has a

higher specific gravity of 2.42.

The chemical analysis and properties of the Type I cement are

given in Table 3. The initial set of cement is found to be at 2

hours and 55 minutes.

22

_,,,

I

:·_·j

:';1

. :j

'

MOISTURE-DENSITY

Results from moisture-density tests show the influence of

compactive effort and influence of the ash source.

Influence of ash source is shown in Figure 5. It indicates

that pond ash has a considerably higher maximum dry density.

Influence of 100 percent and 90 percent compactive efforts

are shown in Figure 6 for mixes with various amounts of cement.

In general, as the cement content increases, the compacted density

increases, and when the optimum moisture content is reached, then

the curves slope down. The compacted densities for 90 percent

compactive efforts are considerably lower than those for 100

percent compactive efforts (data from Tables 4, 5 and 6),

UNCONFINED COMPRESSION

This test determines the influence of following variables on

compressive strength of specimens:

1. Influence of cement content and molding water

content.

2. Influence of molding water content.

3 • Influence of compactive effort.

4. Influence of ash source.

5. Influence of curing time.

6. Influence of wait time before compaction.

7. Influence of vacuum saturation (freeze-thaw simulation).

Influence of cement and molding water contents on 7-day

compressive strengths is shown in Figures 7 and 8 for hopper and

pond ash respectively. As cement content is increased, the

strength is increased, Maximum compressive strengths are obtained

23

... ---· ..•. ·- ......... - .. ~------· . ····-····················-······················-····································

for mixes with optimum moisture contents (data from Tables 7 and

8) •

Influence of compactive effort is presented in Figure 9

(Table 9). This figure shows that 90 percent compactive effort,

will drastically lower the compressive strength. Also, the

moisture content is shifted to right, higher than that for the 100

percent compactive effort.

Influence of ash source is given in Figure 10 (Tables 7 and

8). Ponded ash generally has a higher compressive strength

compared to tht' hopper ash. The difference in strength between

the two ashes increases with increasing cement content.

Influence of curing time on compressive strength is shown in

Figures 11 and 12, for hopper ash with 100 percent and 90 percent

compactive efforts respectively (see Table 10). Strengths

obtained after 28 days of moist curing are higher than those cured

for 7 days.

Influence of wait time between mixing and compaction is

presented in Figure 13 (Table 11). As the wait time increases,

the strength of specimens generally decreases.

Influence of vacuum saturation on compressive strength are

given in Figures 14 and 15 (see Tables 7, 8, 9). Compressive

strengths after saturation are lower. Strengths may reduce as

much as 75 percent of original strength in the "as compacted"

condition.

FROST HEAVE

Results from this test show the influence of cement content,

water content, ash source, and compactive efforts on frost heaving

24

I ,,

I J

of the specimens.

Figure 16 (Table 12) shows the effect of cement content on

frost heave of the specimens made with hopper ash. The frost

heaving decreases as cement content increases. Addition of 10

percent or more of cement limits the frost heave to an acceptable

level provided the sample is compacted at optimum moisture content

100% of Hodified Proctor density.

Figure 17 (Table 12) shows the effect of molding water

content on frost heave of specimens. As the water content

increases, the frost heaving increases.

Figure 18 shows the influence of compactive efforts on the

frost heave of samples. As compactive effort is reduced, the

frost heave of the specimen increases.

Influence of ash source on frost heaving is shown in Figure

19 (Table 12 and 13). As the figure shows, ponded ash is less

susceptible to frost heaving than hopper ash.

DISCUSSION OF RESULTS

It is evident from the results that strength, durability, and

frost resistance of compacted cement-stabilized fly ash mixes

increases as the amount of cement is increased. This is due to

the fact that, more cement produces more cementitious material

upon hydration as well as releasing certain amounts of lime which

then react with the fly ash in a pozzolanic manner. These results

indicate that addition of 12 percent (by solid weight) or more of

cement to fly ash used in this study produces a mix which

satisfies all the design criteria which have been stipulated

25

(4,6,26) for cement-stabilized fly ash base courses.

Due to various factors such as coal type, method of burning,

collection and storage, fly ash displays a high degree of

variability both in chemical and physical properties. These

variations in turn affect the engineering properties and

performance of cement-stabilized fly ash mixtures and the amount

of cement addition required to produce a durable mix. For

instance, free lime and carbon contents affect the chemical

activity, compaction and strength characteristics. While a large

amount of free lime tends to be very reactive and exhibits some

degree of self-hardening, the carbon content inhibits the

pozzolanic reactivity and lowers the strength and compacted

density. The chemical composition presented in Table 2, indicates

a low lime content of 1.07 percent and a moderately high carbon

content of 7.3 percent (typical of bituminous coal fly ashes).

This means that the amount of cement required to stabilize this

fly ash must be relatively high.

Specific gravity influences density and is often used as a

method of comparison between engineering materials. Specific·

gravity of hopper ash as indicated in Table 1, is low (2.22).

This is mostly due to the high carbon content and presence of

hollow particles (cenospheres) in fly ash (specific gravity of

conventional aggregate range from 2.5 to 2.8). Specific gravity

of ponded ash is higher, 2.42. This may be due to the fact that

carbon, cenosphere and lighter particles have been washed away

when the ash is slurried into the holding ponds or lagoon.

Compaction characteristics are usually expressed in terms of

moisture density relationships. The maximum dry density of

26

\ . )

compacted fly ash is low due to the uniform grain-size

distribution of its particles (see Figure 4), low specific

gravity, amount of carbon, and presence of cenosphere particles in

the fly ash. Figure 5 shows the moisture-density curves for

hopper and ponded ash (see Table 4 also). Hopper ash has a maximum

dry density of 77 pcf at an optimum moisture content of 28.5

percent, while ponded ash has a maximum density of 91 pcf at an

optimum moisture content of 20 percent. Again, since ponded ash

is very low in carbon content and is coarser, the maximum density

is higher and occurs at a lower moisture content.

Moisture-density curves for 100 percent and 90 percent

compactive effort of the cement-fly ash (hopper) mixes are

presented in Figure 6 and Tables 5 and 6. As the cement content

is increased, the maximum dry densities are increased. This is

due to the higher specific gravity of cement (3.15 as compared to

2.22 for hopper ash). It may also be due to slight change in

gradation upon addition of cement. Figure 6 also indicates that 90

percent compactive effort lowers compacted densities considerably

and increases the optimum moisture content as compared to 100

percent compactive effort.

It is important to note that the actual moisture contents of

the compacted specimens are about l to 3 percent lower than the

molding water content reported herein (see Tables 5 and 6) due

mainly to evaporation of moisture during mixing and compaction

process. At moisture contents on the wet side of the optimum,

liquid also seeps from the base of the mold during compaction, in

addition to moisture loss by evaporation.

Unconfined compression test was used to determine the

27

compressive strength of cement-stabilized fly ash mixes. Since

strength is a measure of load-bearing capacity under traffic

loads, it is necessary to choose a mix design which satisfies the

strength requirements of 400-450 psi for cement-stabilized fly ash

base courses. Figure 7 (Table 7) shows the effect of cement

content on 7-day compressive strengths of hopper ash mixes. As

cement content increases, so do the compressive strengths, and

compressive strengths are highest for mixes compacted at optimum

moisture content. The lowest compressive strengths are obtained

for mixes compacted at 5 percent on wet side of optimum moisture

content. This is due to decrease in bond strength and friction

between particles. At 12 percent cement or more (% by weight of

solids) and at optimum moisture content or at 5 percent dry of

optimum, all specimens pass the required minimum compressive

strength of 400-450 psi.

Similar results for ponded ash are presented in Figure 8

(Table 8), except that compressive strengths are noticeably higher

than those for hopper ash. The same explanation advanced

previously (on page 26) also holds in this case, namely, when ash

is slurried and discharged into ponds, detrimental, light

particles such as carbon, cenospheres, and some fine materials get

washed away with the current, leaving a coarser and carbon free

materials behind. All pond ash mixes made with 12 percent or more

of cement and optimum moisture content + 5 percent pass the

strength requirement.

The effect of compactive effort on hopper fly ash is shown in

Figure 9 (Table 9). As it can be seen, the compressive strength

is very sensitive to compactive effort, and at 90 percent

28

; :] J

compactive efforts all the specimens (except one) fail to meet the

compressive strength requirement of 400-450 psi.

The influence of ash source on compressive strength is

presented in Figure 10. It indicates that the ponded ash exhibits

higher compressive strengths than hopper ash for the reasons

discussed before.

Strength gain with time is shown in Figures 11 and 12 (Table

10). They show that strength at 28 days are higher than those at 7

days. This gain in strength is due to pozzolanic activity and

additional hydration of cement with time.

Figure 13 (Table 11) shows the effect of wait time between

mix and compaction on compressive strength. As the wait time

increases, the strength decreases. This is influenced by the

setting of cement. For satisfactory results, the wait time should

be limited to 1 hour.

Durability based on residual strength after vacuum saturation

is shown in Figures 14 and 15. Vacuum saturation generally

reduces compressive strength by reducing the effectiveness of the

cementitious matrix and decreasing the bond between particles.

Mixes with 12 percent or more cement, compacted at optimum

moisture content satisfy pass the minimum strength requirement of

400 psi after vacuum saturation,

Figure 16 (Table 12) indicates that as the cement content is

increased, the frost heaving decreases. The frost heave is

reduced to an acceptable limit of 0.50 inches with addition of 12

percent or more of cement, when compacted at optimum moisture

content with 100 percent compactive effort. The addition of

cement not only increases the tensile strength of the fly ash,

29

thereby increasing its ability to resist the heave pressure

produced by the formation of ice lenses, it also reduces the

permeability of the fly ash which restricts the inflow of water

and reduces the quantity of water available for ice lens

formation.

Effects of water content and compactive effort on frost

heaving are presented in Figure 17 and 18 respectively. As

molding water content increases the heave increases because

samples are generally weaker. Mixes compacted at lower compactive

efforts have lower tensile strength and are less dense, therefore

the frost heaving is increased in these mixes as compared to those

with 100 percent compactive effort.

~ Finally, Figure 19 (Tables 12 and 13) show the influence of

ash source on frost heaving. It shows that ponded ash is less

susceptible to frost heaving than hopper ash. The reasons for

better performance of ponded ash are the same as discussed before.

CONCLUSIONS

The following conclusions are based on the work done with a

typical bituminous fly ash produced at Consumers Power Company's,

D. E. Karn plant at Essexville. Both dry hopper fly ash and

ponded fly ash from the Essexville plant were compacted and

stabilized with cement. The engineering properties of these

cement-stabilized fly ash mixtures were determined and evaluated

against criteria established for road base course materials. The

procedures presented in this report are useful for evaluating

other fly ashes. The conclusions listed below pertain to the mix

30

and fly ash used in this study:

1. All mixes with 12 percent (by weight of solids) or

more of cement and compacted at optimum moisture

content to 100% of maximum density by Modified Proctor

pass the strength and durability requirements of

400-450 psi. /

2. The frost heaving is reduced below the acceptable

limit of 0.50 inches when fly ash is mixed with 12

percent or more of cement and compacted at 100 percent

compactive effort.

3. Useful insights and information on the "error

tolerance" or performance loss sensitivity of this

mixture was gained by investigating the influence

of molding water content, compactive effort, wait

time, and mixing procedure on strength, durability,

and frost heave behavior.

4. The ponded ash produces higher compressive strength

before and after vacuum saturation, and heaves less

comparison to hopper ash. However, ponded ash has to

be dried first before mixing and is likely to be

quite variable in its composition and properties

depending on its location in the pond. More work

is needed on this.

5. Strength of specimens increased as the curing

period is increased.

6. Basic data has been acquired for specifying the

hopper fly ash for field installation as a road

pavement base course.

31

RECOMMENDATIONS - FIELD TRIAL

One of the main goals of the laboratory study was to develop

information pertinent to preparation of a specification document

for the construction of a cement-stabilized fly ash base course

for highway shoulder. The University of Michigan research group,

(Gray, Tons, Razi and Mundy) worked together with Stoll, Woods,

and Associates, the Michigan DOT, and Michigan Ash Company in this

effort. As the result of various consultations, it was decided

that a 1/2 mile long test section about 10 inches thick and 8 feet

wide conBtructed from cement-stabilized fly ash will be installed

as a pavement shoulder base course during the 1985-1986

construction. Hopper fly ash from Karn's plan will be used. The

base course will be placed and compacted on a sand subbase. A

topping of about 3 inches of asphalt concrete will be used as a

cover. The draft of the specification is given in the next

section.

32

SPECIFICATION FOR COMPACTED

BASE COURSE

M-54, Grand Blanc, Mich.

Control Section 25074; Job *00337C

FLY ASH - CEHENT MIX PREPARATION

The fly ash - cement mix will be preconditioned, transported,

stockpiled, and mixed with cement on the site by Michigan Ash

Company. The contractor is required to have a front end loader to

load the fly ash in the mixer on the job site.

PRELIMINARY TEST STRIP

A 100-foot long trial section will be constructed in advance

to allow for calibration of mixing and compaction equipment and to

determine the number of compaction lifts.

Cm!PACTION SPECIFICATIONS

The fly ash - cement mix will be picked up by the contractor

from the on-site mixing plant and transported to the shoulder.

Spreading should be done with a shoulder spreader machine in one

pass. No reworking is allowed. The thickness of the layer should

be such that the final compacted thickness is 10 inches ~ 1/2

inch. The initial compaction should be done with a rubber-tired

roller followed by a vibratory roller. The density achieved in

the field should be 98% of the modified Proctor Laboratory

density. Lower densities may be accepted based on compaction

33

results on a trial section and with prior approval of MDOT

officials. The on-site density of the compacted mix will be

checked by a consultant or MDOT using non-destructive nuclear

device and giving instant readings. Acceptance will be based on

these readings. The maximum allowable time between the mixing

time and the final compaction pass is 1 hour.

FINISHING

If necessary, the base course should be fine-graded with a

motor patrol. The surface s~·uld then be sacrified and

proofrolled to insure a finished surface free of ridges, cracks,

ruts, and compaction planes.

JOINTS

Straight transverse and longitudinal joints should be formed

at the end and edges of each day's construction by cutting back

into the completed work to form a true vertical face free of loose

or shattered material. All material resulting from the trimming

operation should be removed from the area to prevent mixing with

fresh base course material. When the bituminous wear surface is

constructed for a roadway, it should be placed so that the wear

surface joints coincide with the base course longitundal joints.

The engineer may consider the sawcutting of roadway pavement

joints at regular intervals to control reflective cracking that

may occur as a result of shrinkage cracks in the base course.

34

SEALING AND CURING

Final compacted layer of cement stabilized fly ash will be

sealed as soon as possible to prevent loss of moisture. A prime

or seal coat consisting of 0.1 to 0.2 gallons per sq. yd of

cut-back liquid or emulsified asphalt will be placed no later than

1 hour after completion of finish operations and after the surface

of the base course has been broomed free of all loose and foreign

material. The bituminous concrete surface will be applied after a

7 day curing period.

QUANTITIES AND DIMENSIONS

The shoulder base course will be 10 inches thick, 8 feet wide

and 3,000 feet long. The fly ash - cement mixture weighs about 80

pounds per cubic foot when compacted to 100% modified Proctor

density at optimum moisture content. Thus the total weight to be

handled is about 800 tons or 740 cubic yards (in place compacted

volume).

INCLEMENT WEATHER

Spreading and compaction of the fly ash - cement mixture in

the field will not be carried out in the following types of

weather:

1. If temperature is less than 32°F the night before

and less than 45° during the time of placing.

2. When it is raining.

3. When wind velocity is more than 15 mph.

35

ENVIRONI1ENTAL TEST INSTALI,ATIONS

Environmental monitoring sampling will be done from existing

drainage facilities. Wells will be dug off the road by ENCOTEC as

needed. The contractor is not involved in the environmental

installations.

36

i !

>'

,-i

1.

2.

REFERENCES

Berry, E.E., and Halhorta, V.M., "Fly Ash for use in Concrete- A Critical Review," Proceedings, ACI Journal, Vol. 77, No. 2, April 1980.

Faber, J.H., "Power Plant Ash Utilization and Energy Conservation Effects," Proceedings, Sixth Mineral Waste Utilization Symposium, u.s. Bureau of Mines and IIT Research Institute, Chicago, IL, May 1978.

3. Material Research Society, "Effects of Fly Ash Incorporation in Cement and Concrete,• Proceedings, Symposium N, Annual Meeting, November 1981.

4.

5.

6 •

7 •

8 .

GAI Consultants, "Dry Ash Utilization Manual," Project 2422-2, Interim Report, Prepared for Electrical Power Research Institute, December 1984.

Consumers Power Company, "Demolition Cost Study for Consumers Power Company Fossil-Fired Electrical Generating Plants," Report of Plant Modification and Misc. Projects Dept. for Facility Planning and Research, June 17, 1983.

Meyers, J.F., Pichunani, R., and Kapples, B.S., "Fly Ash- A Highway Construction Material," u.s. Department of Transportation, FHWA, June 1976.

Barber, E.G., "The Utilization of Pulverized Fuel Ash," Journal of the Institute of Fuels, Vol. 43, No. 348, January 1970.

Gray, D.H., and Lin, Y.K., "Engineering Properties of Compacted Fly Ash," Journal of the Soil Mechanics and Foundation Division, ASCE, Vol. 98, SM4, April 1972.

9. Rohrman, F.A., "Analyzing the Effect of Fly Ash on Water Pollution," Power, August 1971.

10, Weinheimer, C.M., "Evaluating Importance of the Physical and ' Chemical Properties of Fly Ash in Creating Commercial Outlets for

-··J c/ the Material," ASME, Vol. 66, No. 6, 1944.

11. Hecht, N.L., and Duvall, D.S., "Characterization and Utilization of Municipal and Utility Sludges and Ashes: Volume III - Utility Coal Ash," National Environmental Research Center, u.s. Environmental Protection Agency, May 1975.

12. Faber, J.H., and Digioia, Jr., A.M., "Use of Fly Ash in Embankment Construction," Transportation Research Board, No. 593, 1976.

13. American Society for Testing and Materials, "Fly Ash and Raw or Calcinated Natural Pozzolan for Use as Mineral Admixture in Portland Cement Concrete," ASTM C618, Annual Book of ASTM Standards, Vol. 4.02, 1983.

37

I

t:: [:)

I t • I I

f-: !

14. Pozzolanic Technical Bulletins, "Fly Ash- The Modern Pozzolan,• Pozzolanic International, 1983.

15. Thorne, D.J., and Watt, J.D., "Composition and Pozzolanic Properties of Pulverized Fuel Ashes II. Pozzolanic Properties of Fly Ashes as Determined by Crushing Strength Tests on Lime Mortar," Journal, Applied Chemistry, Vol. 15, December 1965.

16, Vincent, R.D., Mateos, M., and Davidson, D.T., "Variation in Pozzolanic Behavior of Fly Ashes," Proceedings, ASTM, Vol. 61, 1961.

17. Minnick, L.J., and Meyers, W.F., "Properties of Lime-Fly Ash­Soil Compositions Employed in Road Construction," Highway Research Board, No. 69, 1953.

18, Barenberg, E.J., "Behavior and Performance of Asphalt Pavements with Lime -Fly Ash- Aggregate Bases," Proceedings, Second International Conference on the Structural Design of Asphalt Pavements, Ann Arbor, Michigan, 1967.

19. Smith, P.H., "Large- Tonnage Uses of PFA in England and Other European Countries," Proceedings, Third International Symposium on Ash Utilization, u.s. Bureau of Mines, IC 8640, 1973.

20. Barenberg, E.J., "Lime- Fly Ash- Aggregate Mixtures in Pavement Construction," Process and Technical Data Publication, National Ash Association, 1974.

21. Davidson, D.T., Sheeler, J.B., and Delbridge, N.G., "Reactivity of Four Types of Fly Ash with Lime," Highway Research Board, No. 193, 1958.

22. GAI Consultants, Inc., "Guide for the Design and Construction of Cement- Stabilized Fly Ash Pavements," Process and Technical Data Publication, National Ash Association, 1976.

23. Dempsey, B.J., and Thompson, M,R., "Interim Report- Durability Testing of Stablized Materials," Civil Engineering Studies, Transportation Engineering Series No. 1, Illinois cooperative Highway Research Program, Series No. 32, University of Illinois at Urbana Champaign, September 1972.

24. Dempsey, B.J., and Thompson, M.R., "A Vacuum Saturation ~1ethod for Predicting the Freeze-Thaw Durability of Stabilized Haterials,• Highway Research Board, No. 442, 1973.

25. Lin, Y.K., •compressibility, Strength, and Frost Susceptibility of Compacted Fly Ash," Ph.D. Thesis, University of Michigan, 1971.

26. Corney, D., and Jacobs, J.C., "The Frost Susceptibility of Soils and,Road Materials,• Laboratory Report LR 90, Road Research Laboratory, Crowthorne, England, 1967.

38

··~ l . I

~~

-'!

! 27. Sutherland, H.B., and Gaskin, P.N., "Factors Affecting the Frost

. \

Susceptibility Characteristics of Pulverized Fuel Ash," Canadian Geotechnical Journal, Vol. 7, No. l, 1970.

28. Stoll, u., "Effect of Laboratory Batching/Mixing Procedures on Uniformity of Cement Dispersal and Compressive Strength of Stabilized Fly Ash," personal communication, 9 Sept. 1985.

39

TABLE 1

Fly Ash Testing Program

Number of Different Values per Variable for each Test* Material and Process MDR SC!ID UC1 UC2 D!V.S.) F.H.

Variables ·Hopper Pond Hopper Hopper Pond Hopper Pond

1. Plant Origin (1) 1 1 1 1 1 1 1 1 1

2. Ash Condition (2) 2 1 1 1 1 1 1 1 1

3. Compaction Effort (2) 1 2 2 1 1 2 1 2** 1

4. Compaction W/C (5) 5 5 3 3 1 3 2 3 3

5. Type Cement (1) 1 1 1 1 1 1 1 1 1

,. 6. Amount Cement 0 (4) 1 4 4 4 4 4 4 5 2

7. Mix Time (1) 1 1 1 1 1 1 1 1 1

8. Wait Time (4) 1 1 1 1 4 1 1 1 1

9. Cure Temperature (1) 1 1 1 1 1 1 1 1 1

10. Cure Length (2) 1 1 2*** 1 1 1 1 1 1

Number of Specimens X 2 20 20 64 24 32 48 16 36 12

*UC1 = Unconfined Compression **90% Compaction Effort for Mixes with UC2 =Unconfined Compression with Wait Time 12% Cement Only MDR = Moisture-Density Relationship SCMD = Soil-Cement Moisture Density ***28- Curing For Mixes with Optimum Moisture D(V.S.) Durability (Vacuum Saturation) Moisture content Only F.H. = Frost Heave

i . !

TABLE 2

Properties of Hopper and Ponded Ash

Chemical Composition (%)

Silica, Si02

Aluminum Oxide, A12o

3

Iron Oxide, Fe2o

3

Calcium Oxide, CaO

Magnesium Oxide, MgO

Lithium Oxide, Li20

Manganese Oxide, Mn02

Phosphorous Pentoxide, P2o

5

Potassium Oxide, K2

0

Sodium Oxide, Na2o

Sulfite, so3

Titanium Oxide, Ti02

Carbon, C (Loss on Ignition)

Moisture Content

Specific Gravity (Water at 68F)

Grain Size Analysis

Sieve Size (%Passing)

Hhdrometer (%Finer)

#30 #100 #200

#325 25 18 13

7 3

(595 um) (149 um) (75 um)

(44 um) Microns Microns Microns Microns Microns

41

Hopper Ash

52.36

28.84

4.91

1.07

0.85

0.04

0.04

0.26

1.59

0.57

0.16

2.04

7.30

0.20

2.22 _/

100 99 96·

88 74 52 37 18 10

Pond Ash

2.42

100 99 92

60 37 26 19 12

5

TABLE 3

Properties of Type 1 Cement

Chemical Composition

Silicon Oxide, Si02

Aluminum Ox~de, A12o3

Iron Oxide, Fe2o3

Calcium Oxide, CaO

Magnesium Oxide, MgO

Sulfur Trioxide, S03

Alkalies as Na2o

Loss on Ignition

Tricalcium Silicate, (3CaO.Si02

)

Dicalcium Silicate, (2CaO.Si02

)

Tricalcium Aluminate, (3CaO.A2o

3)

Tetracalcium Aluminoferrite, (4CaO.A2o

3.Fe

2o

3)

Free Lime, CaO

Insoluable Residue

Physical Tests

Blaine Fineness

Initial Set (Gillmore) Final Set (Gillmore)

Autoclave Expansion

42

Percent

21.12

5.41

2.90

62.62

3.52

2.84

0.74

1.40

45.70

26.1

9.4

8.8

0.20

2 3860 em /gm

2:55 Hours 6:10 Hours

0.10%

TABLE 4

Moisture - Density Data for Hopper and Ponded Ash

llolding Actual Dry I ''·i

Ash Specimen Water Density Wave. I ( y Avg** ·:j Water No. ('lb)* w ('lb) (pcf) ('ib) I d (pcf)

H 1 21 20.35 74.7 20.40 I 74.75 0 2 20.45 74.8 I p 3 24 23.60 74.7 23.63 74.75 p 4 23.66 74.8 E 5 27 26.63 16.6 26.68 76.65 R 6 27.73 76.7

,,.; 7 30 28.48 76.9 28.57 77.0 A 8 28.66 77.1 s 9 33 29.59 75.7 29.77 75.75 H 10 29.95 75.8 p 11 16 14.70 88.7 14.70 88.70

''1 0 12 N 13 18 17.70 89.3 17.0 90.10 D 14 E 15 20 20.0 91.5 20.0 91.50 D 16

.j A 17 22 20.33 91.4 20.33 91.40

A 18

: s 19 24 21.90 90 21.90 90.0

.. 3 H 20

:·l, *Percent of Dry Solid (Dry Solid = Fly Ash + Cement) **(yd)avg = average dry density

43

TABLE 5

Fly Ash - Cement Moisture Density Data (Hopper Ash, 100% Compaction Effort)

I I Molding I Actual Dry I !Specimen I Cement Water I Water Density Wave. I ( 'Y )Avg** ·~

I I (%)* I w (%) !11cfl (%) d No. (%)* I (Jlcfl I 1 I 6 21 I 19.8 76.0 19.70 76.15 I 2 I I 19.6. 76.3 I 3 I 6 24 I 22.7 76.3 22.80 76.25 I 4 I I 22.9 76.2 I 5 I 6 27 I 25.8 76.8 25.70 76.80 I 6 .I I 25.6 76.8 I 7 I 6 30 I 27.9 78.3 27.75 78.35 I 8 I I 27.6 78.4 I 9 I 6 33 I 29.2 76.9 29.30 76.80 I 10 I 29,4 76.7 I 11 9 21 I 19.5 78.5 19.65 78.3 I 12 I 19.8 78.1 I 13 9 24 I 22.8 78.8 22.85 78.80 I 14 I 22.9 78.8 I 15 9 27 I 26.0 79.4 26.00 79.30

16 26.0 79.2 17 9 30 28.2 79.5 28.20 79.45

~·

18 28.2 79.4 19 9 33 29.9 78.2 29.95 78.10 20 30,0 78.0 21 12 21 20.1 77.9 20.15 77.80 22 20.2 77.7 23 12 24 23.1 78.5 22.95 78.55 24 22.8 78.6 25 . 12 27 25.8 80 .o 25.75 79.95 26 25.7 79.9 27 12 30 27.6 79.8 27.70 79.75 28 27.8 79.7 29 12 33 29.8 78.1 29.75 78.20 30 29.7 78.3 31 15 21 20.1 79.2 20.10 79.30 32 20.1 79.4 33 15 24 22.8 80.6 22.85 80.60 34 22.9 80,6 35 15 27 26.0 80.8 26.0 80.95 36 26.0 81.1 37 15 30 27.5 80.6 27.60 80.75 38 27.7 80.9 39 15 33 29.7 78.9 29.75 78.95 40 29.8 79.0

*Percent of Dry Solid (Dry Solid = Fly Ash + Cement) **(yd)Avg = average dry density

44

TABLE 6

Fly Ash - Cement Moisture Density Data (Hopper Ash, 90% Compaction Effort)

I Molding Actual Dry I I Specimen Cement Water Water Density I Wave. ( y )Avg** I (%)* (%)* w !%) !11cf)l (%) d

!11cfl I 1 6 24 23.05 70.4 22.85 70.65 I 2 22.7 10.9 I 3 6 27 25.9 71.4 25.95 71.45 I 4 26,0 71.5 I 5 6 30 28.5 72.1 28.45 72.25

' I 6 28.4 72.4 ··:

I ;. ~: 7 6 33 31.2 73.9 31.35 73.90 I 8 31.5 73.9

9 6 36 33.6 73.0 33.60 73.20 10 33.6 73.4 11 9 24 22.9 72 .o 23.05 71.95 12 23.2 71.8 13 9 27 26.3 72.7 26.10 72.75 14 25.9 72.8 15 9 30 28.8 72.8 28.90 72.85 16 29.0 72.9 17 9 33 31.4 74.7 31.20 74.90

··-"' 18 31.0 75.1 19 9 36 32.5 74.1 32.95 74.1 20 33.4 74.1 21 12 24 23.3 71.4 23.10 71.4 22 22.9 71.4 23 12 27 26.2 72.3 26.20 72.35 24 26.2 72.4 25 12 30 28.8 74.1 28.70 74.35

.":: 26 28.6 74.6 <: 27 12 33 31.5 75.8 31.0 76.20 :l

28 30.5 76.6 29 12 36 32.9 74.0 33.15 74.05 30 33.4 74.1 31 15 24 22.5 72.2 22.80 72.25 32 23.1 72.3 ., 33 15 27 26.4 73.3 26.30 73.40 ·-] 34 26.2 73.5 ~_j 35 15 30 28.9 74.5 29.0 74.45

'.·j 36 29.1 74.4 37 15 33 31.8 75.8 31.35 76.30

.-,' 38 30.9 76.8 39 15 36 33.0 74.7 33.3 74.75 40 33.6 74.8

*Percent of Dry Solid (Dry Solid = Fly Ash + Cement) **(y )Avg

d = average dry density

45

TABLE 7 7-Day Unconfined Compression Data Before and

After Vacuum Saturation (Hopper Ash, 100% Compaction Effort)

Molding uc UC** I (UC ) Specimen Cement Water uc Ave Specimen vs I vs ave

No. !%!* !%!* !Jlsi! !Jlsi! No !Jlsi! I !Jlsi! 1 6 23 289 289 25 274 . I 273 2 289 26 272 I 3 9 23 415 379 27 343 I 343 4 343 28 343 I 5 12 23 532 /' 483 29 328 ,,,/' 375 6 433 30 422 7 15 23 469 514 31 361 424 8 559 32 487 9 6 28 280 298 33 217 217

10 316 34 217 11 9 28 469 451 35 343 359 12 433 36 375 13 12 '28 541 ' / 545 37 397 /' 424 14 548 38 451 15 15 28 731 682 39 502 503

~ 16 632 40 505 17 6 33 208 I 213 41 134 137 18 217 I 42 141 19 9 33 256 I 268 43 177 179 20 280 I 44 180 179 21 12 33 303 /'I 307 45 271 .A 263 22 310 I 46 256 I 23 15 33 343 I 379 47 220 I 233 24 415 I 48 245 I

*Percent of Dry Solid (Dry Solid = Fly Ash + Cement) **UC = Unconfined Compression After Vacuum Saturation

vs

46

TABLE 8 7-Day Unconfined Compression Data Before and

After Vacuum Saturation (Ponded Ash, 100% Compaction Effort)

Molding I uc UC** (UC ) Specimen Cement Water uc I Ave Specimen vs vs ave

No. !%l * !%l* !11sil I !11sil No !11sil !11sil 1 6 15 253 I 247 25 200 206 2 242 I 26 211 3 9 15 420 I 389 27 332 346 4 357 I 28 361 5 12 15 635 /1 607 29 538 545 6 579 I 30 552 7 15 15 749 I 708 31 698 665 8 668 I 32 632 9 6 20 345 I 335 33 271 271 10 325 I 34 271

''"i 11 9 20 568 I 568 35 523 506 i 12 568 I 36 489

13 12 20 715 /I 718 37 740 735 14 722 I 38 731 15 15 20 861 I 883 39 886 879 16 906 l 40 872 17 6 25 141 I 134 -.,, 18 I 126 19 9 25 307 I 298 20 289 I

.•, 21 12 25 451 ,/1/ 450 :; 22 449 I

23 15 25 579 I 577 24 576 I

.-_! .-i ,_·) *Percent of Dry Solid (Dry Solid = Fly Ash + Cement)

**UC = Unconfined Compression After Vacuum Saturation vs .

. __ .j

47

TABLE 9 Before and AFter Vacuum Saturation (Hopper Ash, 90% Compaction Effort)

I Molding uc UC** I (UC ) I Specimen Cement Water uc Ave Specimen vs I vs ave I No. !%!* !%!* !l!si! !l!si! No !I! s i! I !l!si! I 1 6 26 208 201 25 171 I 185 I 2 193 26 198 I I 3 9 26 307 298 27 235 I 236 I 4 289 28 238 I I 5 12 26 343 334 29 289 I 298 I 6 325 30 307 ·I I 7 15 26 334 348 31 383 I 383 I 8 361 32 383 I 9 6 31 226 226 33 202 200 I 10 226 34 198 I 11 9 31 307 319 35 238 245 I 12 330 36 253 I 13 12 31 375 359 37 337 358 I 14 343 38 379 I 15 15 31 514 485 39 433 437 I 16 455 40 440

4 I 17 6 36 144 138 41 121 115 I 18 132 42 108 I 19 9 36 229 226 43 144 140 I 20 222 44 135 I 21 12 36 271 305 45 177 176 I 22 339 46 175 I 23 15 36 370 343 47 220 239 I 24 316 48 258

*Percent of Dry Solid (Dry Solid = Fly Ash + Cement) **Unconfined Compression After Vacuum Saturation

48

TABLE 10 28-Day Unconfined Compression Data

(Hopper Ash)

Molding !Compaction uc Specimen Cement Water I Effort uc ave

No. (%)* (%)* I (%) (psi) (psi) 1 6 28 I 100 478 430 2 I 383 3 9 28 I 100 487 460 4 I 433 5 12 28 I 100 814 696 6 I 577 7 15 28 I 100 803 880 8 I 956 9 6 31 I 90 198 226 10 I 253 11 9 31 I 90 390 384 12 I 379 13 12 31 I 90 541 519 14 I 496 15 15 31 I 90 697 720 16 I 743

~·

*Percent of Dy Solid (Dry Solid = Fly Ash + Cement)

-_{ -i

49

TABLE 11 7-Day Unconfined Compression Data

With Wait Time

I Molding Wait uc Specimen I Cement Water Time uc ave

I (%)* (%)* (Hours) (psi) (psi) 1 I 6 28 1 291 287 2 I 282 3 I 9 28 1 361 345 4 I 328 5 I 12 28 1 489 488 6 I 487 7 I 15 28 1 563 579 8 I 595 9 I 6 28 2 231 224 10 I 217 11 I 9 28 2 289 305 12 I 321 13 I 12 28 2 473 426 14 I 379 15 I 15 28 2 516 538 16 I 559

A~

17 I 6 28 3 253 258 18 I 263 19 I 9 28 3 346 336 20 I 325 21 I 12 28 3 310 363 22 I 415 23 I 15 28 3 502 503 24 I 505

*Percent of Dry Solid (Dry Solid = Fly Ash + Cement)

i,: :-

50

'"~) ,-::

TABLE 12

Frost Heave Data, Hopper Ash

Molding (Compaction( Heave Heave I Heave Heave Ave Specimen Cement Water I Effort (3rd Day 6th Day lOth Day lOth Day

No. (%)* !%)* I !%) I !In) No !In) !In) 1 0 22 I 100 I 1.06 1.47 1.90 1.80 2 I I 1.06 1.25 1,69 3 0 25 I 100 I 1.34 2.09 2.66 2.58 4 I I 1.28 2.09 2,50 5 0 28 I 100 I 1.22 1.94 2.81 2.69 6 I 1.15 1,81 2.56 7 6 22 I 100 0.35 0.79 1.22 1.29 8 I 0.35 0.85 1,35 9 6 25.5 I 100 0.66 0.97 1.29 1.12 10 I 0.32 0.69 0.94 11 6 28.5 100 0.41 0.79 1.10 1.21 12 0.50 0.87 1,31 13 9 22 100 0.16 0.28 0.41 0.54 14 0.25 0,47 0,66 15 9 25 100 0.19 0.35 0.50 0.68 16 0,35 0,57 0.85

~· 17 9 28 100 0.41 0.66 0.91 0.82 18 0.28 0.47 o. 72 19 12 22 100 0.10 0.19 0.35 0.37 20 0.13 0.22 0.38 21 12 24 100 0.07 0.13 0.16 0.37 22 0.06 0.18 0.37 23 12 26 100 0.06 0.12 0.25 0.32 24 0.09 0,22 0.38 25 15 22 100 0.03 0.03 0.04 0.08

:_j 26 0.03 0.06 0.12 27 15 25.5 100 0.03 0.19 0.25 0.19 28 0.03 0.06 0.12 29 15 29 100 0.07 0.19 0.32 0.32 30 0.12 0.25 0,31 31 12 22 90 0.13 0.31 0.84 0.70

< ::j 32 0.16 0.31 0.56

33 12 26 90 0.13 0.31 0.56 0.69 34 0.13 0.38 0.81 35 12 30 90 0.06 0.16 0.28 0.34 36 0.09 0.22 0.41

'-!

*Percent of Dry Solid (Dry Solid ; Fly Ash + Cement)

51

TABLE 13 Frost Heave Data For Ponded Ash

100% Compaction Effort

Molding Heave Heave Heave Heave Ave Specimen Cement Water 3rd Day 6th Day lOth Day lOth Day

No. (%)* (%)* On) (In) <In) On) 1 9 15 o.oo 0.06 0.13 0.31 2 0.03 0.09 0.16 3 9 20 0.06 0.16 0.28 0.27 4 0.06 0.13 0.25 5 9 23 0.09 0.22 0.38 0.40 6 0.09 0.22 0.41 7 12 15 0.00 0.07 0.13 0.12 8 0.03 0.07 0.10 9 12 20 0.04 0.10 0.13 0.13 10 0.04 0.10 0.13 11 12 24 0.03 0.18 0.31 0.31 12 0.03 0.18 0.31

52

Figure 1~ Hatvard Miniature Compaction Equi~~ent

_ ... ~j:~;--

•,:

a) Hobart I'-1ixe.r

b) Vacuum Saturation Apparatus

Figure 2. Hobart Hixer and Vacuum Saturation Apparatu~~

-54-

Figure .3 .. Frost Heave Test Set-Up

·.·:

-55-

... Q) c: :;:: -c: Q) (,) ... Q) Q.

Gravel Sand

Coarse to Fine Silt Clay medium

U.S. standard sieve sizes I I

0 ~ 8 ~ .... ... ~ ... 0 0 0 0 0 0 z z z z z z

I I I I I T ~~r-.

100

80

60

40

20

0

I I I

I I I

I I I I I I I I I I I I I I! I I I I !I I I

I 'l I

I I

I

I I I I

I I I

r

I I

d I I

I I

Ponded

I

I I T

I I ! I I

rr II 'I I

.-g

"' a:l ci

I

I I

I I

I

I I

I I

I

~ I

I '" ~

r I!~ ! I

I '\ Ash I

I ! \. I I I I

l i l I i I I

I I I I I II I li l I

I! I l I

Grain diameter, mm

~

~

' \ \

\

~.

Hopper Ash

\

~

~ Q

Q c::i

1 ....

~ ~'r-.

~ ..... ~

-~

Figure 4. Grain Size Distribution Curves for Hopper and Ponded Ash

56

·'

~ u P<

I

I» '-' ·rl

"' " "' ~ I» ... ~

10~----------------------------------------~

Ponded Ash

80

75 Hopper Ash

704-----~------~----~------~----~----~ 0 5 0 5 0 5

Actual Water Content - W%

Figure 5. Moisture-Density Relationship for Hopper and Ponded Fly Ash

57

4

~.-------------------------------------~ 0 15% Cement

• 12% Cement

0 9% Cement

• 6% Cement

100% Compaction

90% Compaction

4

Actual Water Content - W%

Figure 6. Fly Ash-Cement Moisture Density Relationship, Hopper Ash

58

:---i l 'i

':-'} BOO

.... 700 en

"" -.-l

I

..0: 600 +J

00 0:

" ... +J en 500 " > .... (J)

.-J (J)

" ... ~ 0 u

"" " 0: .... "" 0: 0 C)

0: :::> :>. "' "" I ,_

0

c w = 28% (Optimum Molding Water Content)

• w = 23%

0 w = 33%

0 9 2 5 Cement Content - % Dry Solid

Figure 7. Unconfined Compressive Strength vs. Cement Content, Hopper Ash, 100% Compaction

59

1

Figure 8. Unconfined Compressive Strength vs. Cement Content, Ponded Ash, 100% Compaction

60

-l

i ·-·:

:: j

>!

i "~4-

.<! c-1

.--; '

:J

.<: ;-·: I

:-'

'•')

:)

'

BOO H U)

"" 700 I

.a 4-J bO 600 <=! <!) H 4-J U)

<!) 500 l> ·rl Ul Ul <!) 400 H 0. s 0 u

"" 300 <!)

<=! ·rl 4-<

<=! 200 0 u <=! p

:>, 100 "' <=> I .....

0

• w = 31% (Optimum Molding Water Content)

c w = 26%

0 w 36%

9 2 5 Cement Content - % Dry Solid

Figure 9. Unconfined Compressive .Strength vs. Cement Content, Hopper Ash, 90% Compaction

61

1

100

H Ul I>;

I

..::: '-' bJ) ,;

"' H '-' Ul

~

"' :> ·r< CJl CJl 500 "' H 0. s 0 400 u

'0

"' ,; ·r< 4-1 ,; 0 u ,; p

!»

"' I=> I ,.._

Q

8 Ponded Ash

C Hopper Ash

0 2 5

Cement Content - % Dry Solid

Figure 10. Influence of Ash Source on Unconfined Compressive Strength, 100% Compaction, Optimum Molding Water Content

62

1

i'·

H Ul

"" I ~· .c ...

bD ,:; Q)

H ... Ul

Q)

:> •.-1 (J) (J) Q) H

IF 0 u ., Q) ,:;

•.-1 4-l ,:; 0 <J ,:; ;:o

~ 28-Day Curing

D 7-Day Curing

6 9 12 15

Cement Content - % Dry Solid

Figure 11. Strength Gain with Time, Hopper Ash, 100% Compaction, Optimum Molding Water Content

63

H Cl)

0..

~· ..c: '"' OJ)

" <!)

H

'"' Cl)

<!)

i> .... Ol Ol <!)

H

[j' 0 u

""' <!)

" .... 4-l

" 0 <J

" ~

~ 28-Day Curing

D 7-Day Curing

6 9 12 15

Cement Content - % Dry Solid

Figure 12. Strength Gain with Time, Hopper Ash, 90% Compaction, Optimum Molding Water Content

64

' '

Figure 13. Influence of Wait Time on Unconfined Compressive Strength, Hopper Ash, 100% Compaction, Optimum Molding Water Content

65

80 H Cll

"" .a +J OJ)

" "' H

'"' Cll

"' ~ .... Ul Ul

"' H

~ 0 u

"" "' " .... 4-<

" 0 u

" :::> I»

"' 'T .....

0

•As Compacted, 100%

tJ Vacuum Saturated, 100% Compaction

0 Vacuum Saturated, 90% Compaction

2 5 Cement Content - % Dry Solid

Figure 14. Unconfined Compressive Strength Before and After Vacuum Saturation, Hopper Ash, Optimum Molding Water Content

66

1

··)

Figure 15. Unconfined Compressive Strength Before and After Vacuum Saturation, Ponded Ash, 100% Compaction, Optimum Molding Water Content

67

3

2.

(I) II)

..c: ()

l'l H

(I)

» 1. C1j

~

0 .....

"" II) ....,

""' < II) (b) > C1j II)

::t:

Cement Content - % Dry Solid

Figure 16. Frost Heaving in Compacted Fly Ash. (a) Heave in Compacted Sample with 6% Cement. (b) Frost Heave vs. Cement Content, Hopper Ash, 100%

Compaction, Optimum Molding Water Content.

68

; 'i .•-,

I

1~----------------------------------------.

.8

04---------~--------r---------.-------~ 9 1

Time - Days

Figure 17. Influence of Molding Water Content on Frost Heave, Hopper Ash, 100% Compaction, 9% Cement

69

UJ A <lJ

"' ()

10 H

(!)

:> <1J (!)

::0

1~----------------------------------------.

.8 0 90% Compaction

• 100% Compaction

. 6

.4

.2

04----------r--------~----------~------~ Q

Time - Days

Figure 18, Influence of Compaction Effort on Frost Heave, Hopp.er Ash, Optimum Molding Water Content, 12% Cement

70

1

1

.9

.B

.7

Cll

.6 ())

..c:: (.)

" H .5 ())

~ .4 ())

P:1

.3

.2

.1

0

a Hopper Ash

a Ponded Ash

0 9 1 Time - Days

Figure 19, Influence of Ash Source on Frost Heave, 100% Compaction, Optimum Molding Water Content, 12% Cement

71