FINAL TECHNICAL
REPORT
November
1, 1999, through October 31,
2000
Principal Investigator:
Tarun
R. Naik
Other
Investigator:
Rudolph N. Kraus
Project
Manager:
Dr. Ronald H. Carty, ICCI
ABSTRACT
This
project was proposed to provide a practical solution to disposal problems
for Illinois coal combustion products
(CCPs). The entire project work
was organized in three phases, each phase lasting one
year. Phase I work was directed
toward optimizing mixture proportions for ready-mixed concrete and masonry
products containing Illinois coal ash through lab investigation during the
year 1994-1995. In Phase I,
a number of candidate mixtures for concrete, bricks, blocks, and paving stones
were established based on strength and durability performance
data. In Phase II (1996-1997),
mixtures selected from Phase I were field manufactured and evaluated to establish
optimum concrete mixture proportions containing Class F fly
ash. Phase III, 1999-2000, reported
here, emphasizes the utilization of clean coal ash and blends of clean coal
ash with Class F fly ash from Illinois in production of concrete and
cast-concrete products.
Three non-air entrained,
three non-air entrained (HPC) with a high-range water reducing admixture,
and three air entrained concrete mixtures, were manufactured at the facilities
of the United Ready-Mix, Inc., Peoria,
IL. One mixture of each type
of concrete was a control mixture without fly ash and the remaining mixtures
contained fly ash up to a maximum of 35% of clean coal ash based upon total
cementitious materials and 5% by weight Class F fly ash as a partial replacement
of aggregates. Concrete mixtures were evaluated for strength and durability
related properties. Specimens
were tested for compressive strength, splitting tensile strength, flexural
strength, abrasion, and drying
shrinkage. Fifteen cast-concrete
product mixtures consisting of five 8-in. hollow-core block mixtures, five
2-in. solid paving stone mixtures, and five brick mixtures were manufactured
at the facilities of Crumb-Colton Block Company, Rockford,
IL. These masonry product mixtures
contained up to a maximum of 45% clean coal fly ash based upon total cementitious
materials, and 8% by weight of Class F fly ash as a partial replacement of
aggregates. The block, paving
stone, and brick mixtures were tested and evaluated for compressive strength,
absorption, density, freezing and thawing resistance, and abrasion as required
by the applicable ASTM standards.
Based upon the results of the project, both clean coal ash and Class
F fly ash may be successfully used in applications for both concrete and
cast-concrete products.
EXECUTIVE
SUMMARY
In 1997 approximately
5.5 million tons of coal combustion products were generated from combustion
of Illinois coal. About 3.0
million tons of these are produced in Illinois and the remaining 2.5 million
tons are generated in other states (including Wisconsin) burning Illinois
coal. A majority of these ash
products are landfilled. The
overall utilization rate in the USA for all coal ashes (excluding FGD material)
was approximately 34% in 1997 (i.e., about 27 million
tons). Utilization of clean
coal ash is much lower than Class F fly ash. This is due to the fact that
there is a significant lack of commercial products that utilize clean coal
ash. At its January 1999
international conference, the American Coal Ash Association (ACAA) did not
report on any clean coal ash utilization in concrete or cast-concrete products
(except for one paper presented by the members of the research team for this
project). Additional information
in June 1998 was presented by Naik, et al. at the Sixth CANMET/ACI International
Conference in Bangkok, Thailand, partially based upon ICCI’s project
Phase II, Year 2, activities. With
increasing federal regulations on power plant emissions, finding use for
clean coal ash (vs. Class F fly ash) is becoming a more important issue since
the quantity of clean coal ash will
increase. Finding practical
solutions to this "ash problem" is essential due to shrinking landfill space,
environmental concerns, and increased public awareness.
Phase I of this
project was successfully completed in 1994-1995 (and reported to ICCI and
in industry publications).
Activities for Phase I involved determination of physical, chemical,
mineralogical, and microscopic properties of Illinois coal ash samples obtained
from eight different sources.
Based on the evaluation, two sources of both conventional Class F
fly ash and clean coal ash were selected for further
investigation. Two additional
ash samples were developed by blending these conventional Class F and clean
coal ashes. Thus, a total of six ash samples were used in Phase I for making
cement-based construction materials in the
lab. Activities involved developing
mixture proportions for high-quality structural grade concrete and masonry
products. Phase II (Year 2 -
1996 - 1997) objectives were to develop new manufactured products containing
Illinois Class F fly ash and evaluate these products after pilot-scale
manufacturing. Based upon Phase II results, several mixtures containing high
volumes of Class F fly ash looked very promising for both concrete and
cast-concrete products.
The objectives of
this third year (Phase III) project work (November 1, 1999 to October 30,
2000) were similar to Phase II but expands the development of manufactured
products by using Illinois clean coal ash and blends of Illinois Class F
ash with clean coal ash. These
mixtures were originally proposed for Phase II, but were eliminated later
due to the project funding modification.
Class F fly ash and clean coal ash were obtained from two Illinois
coal-burning plants; Class F fly ash from Williams Energy Services (WES),
Pekin, IL, and clean coal ash from Southern Illinois University (SIU) at
Carbondale, IL. To accomplish the project objectives, concrete and
cast-concrete products were produced under field conditions at manufacturing
facilities in Peoria and Rockford, IL.
The mixture proportions selected for Phase III were based on strength
and durability test results from Phase I and
II.
Work completed for
Phase III included testing of all aggregates and both ashes used in the
manufacturing of concrete mixtures and cast-concrete blocks and paving stones
mixtures. Concrete was produced
at a ready mixed concrete plant (United Ready-Mix in Peoria, IL), and hollow
core blocks, paving stones, and bricks were manufactured at a masonry products
manufacturing plant (Crumb-Colton Block Company, Rockford,
IL).
A total of nine
ready-mixed concrete mixtures, consisting of three non-air entrained, three
non-air entrained (HPC) containing high range water reducing admixture (HRWRA),
and three air entrained, were manufactured in Peoria,
IL. Each mixture was batched and mixed at the ready-mixed
concrete plant of United Ready-Mix, Inc. (URMI), Peoria,
IL. A total of 15 cast-concrete products mixtures were
manufactured at the facilities of the Crumb Colton Block Company, Rockford,
IL. The dry-cast concrete products
mixtures produced consisted of five hollow-core block mixtures, five paving
stone mixtures, and five brick mixtures.
One non-air entrained reference concrete was proportioned without
fly ash to attain the 28day impressive strength of 5,000
psi. Two additional non-air entrained concrete mixtures were
also proportioned with clean coal fly ash at the rate of 22% and 25% by weight
of total cementitious materials.
The third mixture (No. N3) also contained 5% by weight of Class F
fly ash as a replacement by weight of
aggregates. These mixtures had
the slump in the range of 5 ± 1
in.
The non-air entrained HRWRA reference concrete mixture was
proportioned without fly ash to achieve the 28-day compressive strength of
5,000 psi. Additionally, two
non-air entrained HRWRA concrete mixtures were proportioned with clean coal
fly ash at the rate of 35% and 33% by weight of total cementitious
materials. One of these two fly ash mixtures also contained 5% by
weight of Class F fly ash as a replacement of
aggregates. These mixtures had the slump in the range of 4±1½
in. The air entrained control
mixture was proportioned without fly ash to attain the 28-day compressive
strength of 4,000 psi, per IL-DOT needs.
Two additional air entrained mixtures were also proportioned to contain
clean coal fly ash at cement replacements of 17% and 20% by weight of total
cementitious materials. One
of the mixtures also contained 5% of the Class F fly ash as a replacement
by weight of aggregates. These
mixtures had the slump in the range of 3½±½ in.
All ready-mixed
concrete test specimens were evaluated for compressive strength, splitting
tensile strength, and flexural strength, as a function of
age. Additional tests conducted
on the air entrained concrete mixtures included shrinkage, abrasion resistance,
freezing and thawing resistance, salt scaling resistance, and chloride ion
penetration resistance.
Compressive strength,
splitting tensile strength, and flexural strength was measured for all concrete
mixtures. As expected, strength
for all mixtures increased with increasing
age. Compressive strength of
non-air entrained concrete at the 28-day age range from 3,600-5,000 psi,
and increased to 4,700-6,400 psi at the age of 182
days. The compressive strength
decreased with increased fly ash
content. The compressive strength
data for the non-air entrained HRWRA concrete mixtures ranged from 3,500
to 5,300 psi at the age of 28 days to a range of 5,300 to 7,440 psi at the
age of 182 days. The early age
strength up to the age of 7-days was lower for mixtures containing fly ash;
however, between 7 and 28-days, the rate of compressive strength gain for
the fly ash mixtures was significantly higher than the control mixture without
fly ash. Compressive strengths
achieved by the non-air entrained HRWRA ash mixtures between the ages of
28 days and 182 days are suitable for most concrete construction
applications. For air entrained
concrete mixtures, the reference mixture, (No. A1), without ash attained
a compressive strength of 4,535 psi at the 28-day age, and 5,505 psi at the
age of 182 days. At the early
ages up to 7 days, concrete strength was lower for fly ash mixtures compared
to this reference mixture. Mixture
A2, containing 17% clean coal ash exhibited higher compressive strength than
the control (5,540 psi at 28 days and 7,515 psi at 182
days). Mixture A3, containing
20% clean coal ash and 5% Class F ash had compressive strengths that were
lower than Mixture A1, at the age of 182 days, but achieved strength that
were acceptable for many concrete applications, such as driveways, roadways,
and general residential construction.
In general, all
concrete mixtures with clean coal ash and Class F fly ash have an excellent
resistance to abrasion, and in fact out-performed the reference mixtures
without fly ash. Resistance to Chloride ion penetration for all concrete
mixtures increased at later ages.
This indicates that the microstructure of the concrete containing
fly ash was more dense due to the fineness and improved additional hydration
products produced by the ash materials.
For air entrained concrete mixtures, when concrete surfaces were exposed
to a calcium chloride solution, mixtures containing fly ash were less resistant
to scaling than the reference mixture without
ash. Mixture A2 and A3 (17%
clean coal ash, and 20% clean coal ash with 5% Class F ash, respectively)
exhibited moderate to severe scaling.
The relatively poor performance of the mixtures containing ash is
attributed to the low air content of these mixtures compared to the reference
mixture. Freezing and thawing
resistance of the air entrained concrete mixtures were also
evaluated. The reference mixture
without ash had an average relative dynamic modulus value of 34 after 300
freezing and thawing cycles, which would be considered to be
poor. Mixtures containing ash
(Mixtures A2 and A3) broke apart after only 60 cycles of freezing and
thawing. This relatively poor
performance of the mixtures containing ash were attributed to a low amount
of entrained air.
Fifteen dry-cast
concrete mixtures were manufactured for this project at the Crumb-Colton
Block Company at their manufacturing plant in Rockford,
IL. Five mixtures of 8-inch
hollow core concrete block, five mixtures of 2-inch solid paving stones,
and five mixtures of brick mixtures were manufactured as a solid
block. Each type of concrete
consisted of a control mixture (Mixture M1 for blocks, Mixture P1 for paving
stones, and Mixture B1 for bricks) which were proportioned without fly ash
and an additional four concrete mixtures for each type of cast-concrete product
were proportioned with clean coal fly ash used as a partial replacement of
cement. Two of the clean coal
fly ash mixtures also contained Class F fly
ash. The Class F fly ash was
used as a partial replacement of both the fine and coarse aggregate due to
the relative coarseness of the fly ash and additional aggolomorate coarse
fractions of the fly ash. Prior
to the use of this coarse Class F fly ash in the dry-cast concrete products
mixtures, particles larger than 3/8" were removed from the fly ash by
sieving.
Three reference
mixtures, one each for blocks, paving stones, and bricks, were manufactured
without fly ash. Hollow-core
block, paving stone, and brick mixtures contained clean coal fly ash as a
partial replacement of cement (23%-40% by weight of the total cementitious
materials). Two other mixtures
for all these three products also incorporated Class F fly ash as a partial
replacement of fine and coarse aggregate (6 to 8%). The cast-concrete mixtures
for blocks and bricks were evaluated for compressive strength, absorption,
density, and shrinkage as a function of
age. The paving stone mixtures
were tested for compressive strength, absorption, density, and
abrasion. The compressive strength
of hollow-core masonry block mixtures through the age of 91 days met the
ASTM C 90 requirement of 1,900 psi.
The density of block mixtures ranged between 124 and 138
lbs/ft3. The control
mixture without fly ash had the highest density 138 lbs/ft3; while
mixtures containing the Class F fly ash had the lowest density, 128 and 124
lbs/ft3. The absorption
values for blocks were in the range of 5.0 to 7.9
lb/ft3. All block
mixtures met the ASTM requirement for absorption (13 lb/ft3
max.).
The compressive
strengths of all paving stone mixtures with the exception of mixtures containing
Class F ash met the ASTM C 936 compressive strength requirement of 8,000
psi for paving stones Class F ash had lightweight pieces with up to 3/8”
size which were included in the paving stones
mixtures. These lightweight
pieces apparently did not have sufficient strength required for a high strength
application such as paving stones.
All paving stone mixtures met the ASTM C 936 paving stone requirement
for absorption (5% max.). None of the mixtures met the ASTM C 936 requirement for
abrasion, due to the unorthodox manufacturing of these paving
stones. The units were cast
and compacted vertically, rather than flat as they would be placed in
service. This difference in
compaction probably produced a less dense paving stone specimen which affected
their performance. All mixtures
with the exception of Mixtures P4 and P5 met ASTM C 936 requirement for freezing
and thawing resistance. The
two mixtures that did not meet the requirement had Class F
ash (Mixtures P4 and P5) along
with clean coal ash in the mixture.
For dry-cast concrete
bricks, although most mixtures met ASTM C 55 Type N (general use) or Type
S (veneer and face units) requirements at later
ages. It is believed that the strength of the tested bricks
would be significantly higher than that obtained if the compression load
was applied through the axis of the plane of expected loading (i.e., flat)
instead of loaded perpendicular to the plane of loading (tested on
edge). The density of the dry-cast
concrete bricks varied between 130-142 lb/ft3, the minimum being
for the mixture containing Class F fly ash, and the maximum being for the
no-fly ash mixture. The average
absorption values for the bricks ranged from 7.1 to 8.8% (9.9 to 11.5
lb/ft3). Mixture
B1 (without ash), B2 (29% clean coal ash), and B5 met the absorption requirements
for both Type S and Type N, other mixtures met the requirement for Type S
brick.