rr-640 - use of fly ash in a highway shoulder base course · in bituminous concrete mixes as...
TRANSCRIPT
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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
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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
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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
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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.
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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
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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