U.S. patent application number 10/623806 was filed with the patent office on 2004-11-25 for cupola slag cement mixture and methods of making and using the same.
Invention is credited to Fallin, James H., Stroup, Randy D., Stroup, Willie W..
Application Number | 20040231569 10/623806 |
Document ID | / |
Family ID | 26879042 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040231569 |
Kind Code |
A1 |
Stroup, Willie W. ; et
al. |
November 25, 2004 |
Cupola slag cement mixture and methods of making and using the
same
Abstract
A slag cement mixture and process of making the same is
disclosed. The slag cement mixture is composed of cupola slag and
portland cement. The cupola slag is optionally ground granulated.
One embodiment of the process includes rapidly quenching the slag
by submersion into water or by spraying water onto it, and grinding
the resulting product to achieve a fineness of at least 6,000
cm.sup.2/g. The process also includes the addition of 35% ground
granulated cupola slag to portland cement to achieve a stronger and
harder cement than portland cement alone.
Inventors: |
Stroup, Willie W.; (Maceo,
KY) ; Stroup, Randy D.; (Lewisport, KY) ;
Fallin, James H.; (Lewisport, KY) |
Correspondence
Address: |
HOWREY SIMON ARNOLD & WHITE LLP
ATTEN: MARGARET P. DROSOS, DIRECTOR OF IP ADMIN
2941 FAIRVIEW PARK DR, BOX 7
FALLS CHURCH
VA
22042
US
|
Family ID: |
26879042 |
Appl. No.: |
10/623806 |
Filed: |
July 22, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10623806 |
Jul 22, 2003 |
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10285682 |
Nov 1, 2002 |
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6627138 |
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10285682 |
Nov 1, 2002 |
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09784344 |
Feb 16, 2001 |
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6521039 |
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60183370 |
Feb 18, 2000 |
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Current U.S.
Class: |
106/714 |
Current CPC
Class: |
C04B 2111/0075 20130101;
C04B 7/19 20130101; C04B 2111/60 20130101; Y02P 40/10 20151101 |
Class at
Publication: |
106/714 |
International
Class: |
C04B 007/14; C04B
007/19; C04B 011/00; C04B 028/14 |
Claims
1. A cement mixture comprising cupola slag blended with a.
conventional cement, wherein the cupola slag is ground to a
fineness greater than 4,000 cm.sup.2/g.
2-28. (Canceled).
Description
RELATION TO PRIOR APPLICATION
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 60/183,370, filed Feb. 18, 2000.
FIELD OF INVENTION
[0002] The present invention relates to cement. More particularly,
the present invention relates to a slag cement mixture and a
process of making the same. While the invention is subject to a
wide range of applications, it is especially suited for use in
structural concrete and concrete construction.
BACKGROUND
[0003] Cement is a widely used building material. A particularly
popular variety of cement is portland cement. Portland cement is
used in many applications such as mortar, concrete, and cement
building materials such as building blocks. Portland cement is
produced by pulverizing clinker to a specific surface area of about
3,000 to 5,000 cm.sup.2/g or finer. Clinker is created in a cement
kiln at elevated temperatures from ingredients such as limestone,
shale, sand, clay, and fly ash. The cement kiln dehydrates and
calcines the raw materials, and produces a clinker composition
comprised of tricalcium silicate (3CaO-SiO.sub.2), dicalcium
silicate (2CaO-SiO.sub.2), tricalcium aluminate
(3CaO-Al.sub.2O.sub.3), and tetracalcium aluminoferrite
(4CaO-Al.sub.2O.sub.3-Fe.sub.2O.sub.3).
[0004] Conventional mortar and concrete compositions contain
cement, aggregates such as gravel and sand, and water to activate
the hydration process. A mortar product is a hardened cement
product obtained by mixing cement, a fine aggregate, and water. A
concrete product is a hardened cement product obtained by mixing
cement, coarse aggregate, water, and often a fine aggregate as
well.
[0005] The strength properties of concrete and mortar products
depend in part on the relative proportions of cement, aggregates,
and water. The American Society for Testing and Materials ("ASTM")
standard test procedures, such as ASTM C192 and C39 describe the
procedures for mixing, casting, curing, and testing portland cement
concrete mixtures with 1, 3, 7, 14, and 28 day standards. Greater
compressive strength is a desirable feature of cement, and a number
of materials have been used to improve the compressive strength of
cements.
[0006] One way of improving the compressive strength of hardened
cement is to blend ground granulated blast furnace slag with cement
to give an improved cement composition. Blast furnace slag is a
by-product of the production of iron in a blast furnace consisting
of silicates and aluminosilicates of calcium. A quick setting
cement can be produced by grinding blast furnace slag with gypsum.
(See, for example, U.S. Pat. Nos. 1,627,237 and 2,947,643). Blast
furnace slag has hydraulic properties very similar to portland
cement, and adding blast furnace slag to cement is routine to
increase the cement's strength. (See ASTM Specification C989).
[0007] Typical North American blast furnace slag composition ranges
are 3240% SiO.sub.2, 7-17% Al.sub.2O.sub.3, 2942% CaO, 8-19% MgO,
0.7-2.2% SO.sub.3, 0.1-1.5% Fe.sub.2O.sub.3, and 0.2-1.0% MnO. (see
The Portland Cement Association Research and Development Bulletin
RD112T). Blast furnaces in the U.S. are operated using a basic
slag, typically defined as the slag ratio: (% CaO+% MgO)/(%
SiO.sub.2+% Al.sub.2O.sub.3), where the slag ratio is maintained in
excess of 1.0 in order to remove sulfur from the iron produced and
to facilitate producing an iron of high carbon content. The
chemical composition of blast furnace slag also varies world wide,
especially in alumina content. Blast furnace slags have long been
recognized as very useful commodities and have been used in a
number of applications. In addition to its use as cement additive,
blast furnace slag has been used in asphalt, sewage trickle-filter
media, roadway fills, and railroad ballast.
[0008] Blast furnace slags can be used to prevent excessive
expansion of concrete mixtures that have a high-alkali content and
aggregates that are alkali-reactive. Use of blast furnace slag as
40% or more of such a cement mixture can prevent excessive
expansion. Blast furnace slag is characterized by its short setting
time, which is the time between the addition of mixing water to a
cementitious mixture and when the mixture reaches a specified
degree of rigidity as measured by a specified procedure.
[0009] Steel slag is also used as a cement additive. Steel slag is
formed in the process of making steel in a blast furnace, and often
has a high concentration of ferrites. Because of its high ferrite
composition, steel slag is generally used as a filler in cement
road building material or as a feedstock raw material in cement
kilns. It is possible to produce a hydraulic cement base from steel
slag by adding further minerals to the slag portion, thereby
reducing the ferrite composition of the slag. This additional step,
while rendering a usable product, is costly and time consuming.
[0010] Mixtures of blast furnace slag and steel slag have resulted
in stronger cement products, but cupola furnace slag, a by-product
of cast iron production, is only rarely used in cement except as a
processing addition. (See ASTM C465 and Cupola Handbook, published
by the American Foundrymen's Society). Blast furnaces and cupola
furnaces are operated differently and are used to make different
iron products, consequently, the slag products of these furnaces
are also different, both in chemical composition and in material
properties. Cupola slag has different hydraulic properties than
blast furnace slag. For example, cupola slag blended cement sets
more slowly and at 7 days lacks the strength of blast furnace slag
blended cements. Also, cupola slag is not a common concrete
additive due to environmental concerns such as the possibility of
rain water leaching out some of its components. Indeed, cupola slag
often presents a disposal problem, which creates an additional
expense, ultimately increasing the cost of the iron produced.
[0011] There is an ever present need in the cement art for harder,
stronger cement products with longer setting times. There is also a
need in the cast-iron production art for a disposal method for
cupola slag that is environmentally safe and economically
practical.
SUMMARY OF THE INVENTION
[0012] Accordingly, the present invention is directed to a cupola
slag blended cement with an increased compressive strength. The
principal advantage of the present invention is a cement mixture
that results in a concrete which is both harder and stronger while
providing a means of recycling cupola slag that is both
environmentally sound and economically practical. The cement
compositions of the present invention have a resistance to
expansion due to sulfate attack and alkali silica reaction, and can
be formulated to have a wide range of curing times.
[0013] To achieve these and other advantages and in accordance with
the purpose of the invention, as embodied and broadly described,
the invention is a hydraulic cement containing cupola slag ground
to a fineness of greater than 4,000 cm.sup.2/g blended with
portland cement. A preferred embodiment of the invention is a
hydraulic cement containing cupola slag ground to a fineness of
greater than 5,000 cm.sup.2/g blended with portland cement. In the
most preferred embodiment, the invention is a hydraulic cement
containing cupola slag ground to a fineness of between 6,000
cm.sup.2/g and 7,000 cm.sup.2/g.
[0014] In one embodiment, the invention is a hydraulic cement
containing from about 20 to 50% of a ground granulated cupola
furnace slag blended with portland cement. In a preferred
embodiment, the invention is a hydraulic cement containing from
about 30% to 40% cupola slag blended with portland cement. In
another preferred embodiment, the invention is a hydraulic cement
containing about 35% cupola slag blended with portland cement.
[0015] The invention includes ground granulated cupola furnace slag
with a fineness of about 5,000 to about 7,000 cm.sup.2/g and
meeting the fineness requirement of the ASTM C989 Grade 100
specification for blast furnace slag.
[0016] The invention includes ground granulated cupola furnace slag
with a fineness of about 6,000 to about 6,750 cm.sup.2/g. The
invention also includes ground granulated cupola furnace slag with
a fineness of about 6,500 cm.sup.2/g.
[0017] In one embodiment of the invention, a blended cement mixture
of about 35% cupola furnace slag displays a 28 day compressive
strength of more than 7,000 psi and a flexural strength of more
than 700 psi.
[0018] In another embodiment of the invention, the total heat of
hydration of the blended cement mixture of about 35% cupola furnace
slag does not exceed 250 J/g when measured for 72 hours, and the
expansion of mortar bars does not exceed 0.20% at when measured at
14 days.
[0019] In one embodiment, the invention includes a process of using
cupola slag as a raw cement kiln feedstock.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0020] FIG. 1 shows the results of conduction calorimetry tests
performed on two neat cement pastes: standard portland cement
(darker line), and a portland cement/cupola slag blend (lighter
line).
[0021] FIG. 2 shows the results of compressive strength tests
performed on concrete objects made with the same aggregates, but
using either standard portland cement (solid line), or a 65/35%
blend of portland cement and cupola slag (dashed line).
[0022] FIG. 3 shows the results of X-ray powder diffraction tests
performed on cupola furnace slag (upper diffractogram) and on blast
furnace slag (lower diffractogram).
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present invention encompasses blends of cupola slag and
cement with an increased hardness and strength than the cement
alone.
[0024] The hydraulic cement compositions of the present invention
provide a solution to the current needs of the art by converting
cupola furnace slag into a useful product. The cement compositions
of the invention can be formulated to have a wide range of
resistance to sulfate attack as well as wide range of curing times
so that they can be used for a variety of purposes such as making
concrete objects. In particular, a hydraulic cement containing 35%
of a ground granulated cupola furnace slag, with a fineness of at
least 6,000 cm.sup.2/g and meeting the fineness requirement of the
ASTM C989 Grade 100 specification for blast furnace slag blended
with portland cement creates a composition whose superior
compressive strength develops slower than the concretes currently
in use thus providing a more durable concrete product.
Additionally, the sulfate attack resistance of the present
invention increases the useful life of any products made from
cupola furnace slag blended cements thereby increasing the length
of time between replacing such products and reducing the overall
cost of any such project.
[0025] The chemical composition of portland cement plays an
important role in the way that slag blended cements cure, age and
resist chemical attack. The processing of portland cement is well
known in the art, as are the various methods to alter the chemical
composition during the manufacturing process. The invention is not,
however, limited to portland cement. It is believed that cupola
slag mixed with other cements will improve the strength of the
cement/cupola slag mixture.
[0026] A cupola furnace is a vertical shaft furnace used to produce
cast iron by high temperature melting of metallic and mineral
charge materials. A cupola furnace contains a continuous melting
shaft which can accept a wide range of raw materials including
oily, wet and contaminated scrap. Compared to batch-type furnaces,
the energy requirements of a cupola furnace are low. Molten iron is
tapped from the bottom of the furnace. Slag is removed in a molten
state via a slag hole. Cupola furnace slag is preferably rapidly
quenched by submersion into water to yield a fine, granulated
product, thus reducing the amount of grinding required to make the
slag useful in cement. Alternatively, water may be sprayed upon the
slag to quench it, or the slag may be allowed to air-cool for a
time, resulting in a coarser, non-granulated product.
[0027] Cupola furnace slag differs from blast furnace slag in
chemical composition; for example, cupola slag has a higher silica
content and a lower calcium oxide content than blast furnace slag.
While blast furnaces operate using a basic slag, cupola furnaces
generally operate using an acid slag for the production of gray
cast iron. (Basic slags are sometimes used in cupola furnaces for
the production of ductile iron because the basic slag removes
sulfur in the cupola during melting). Blast furnace operations
produce about 30 percent slag per ton of molten iron, while cupola
furnace operations produce 5 to 6 percent slag per ton of iron ore
that is melted.
[0028] Cement users are particularly interested in setting and
strength development characteristics. The maximum and minimum
setting times and minimum strengths of reference cement are
specified in the ASTM C150 standard specification for portland
cements. A number of minor components which form in the clinker
from impurities present in the raw materials or fuel can influence
both the clinker formation process and the hydraulic reactivity and
cementitious properties of the resulting cementitious material. In
particular, the level of alkalis, such as K.sub.2O and Na.sub.2O
present in cement, especially portland cement, may be of concern.
For example, if the cementitious materials are combined with
aggregates containing SiO.sub.2, the alkalis present in the
cementitious materials may react with the SiO.sub.2 to form an
expansive alkali silica gel, which can lead to cracking and break
up of the concrete structure. Because the detection of reactive
SiO.sub.2 in aggregates is difficult, cementitious materials with
low alkali content are generally used. Blast furnace slags are
generally very basic in nature. Thus, a maximum equivalent
Na.sub.2O of about 0.6 percent is included as an optional limit in
the ASTM C150 specification.
[0029] It is possible to use cement containing more than 0.60
percent equivalent Na.sub.2O with SiO.sub.2 reactive aggregates
while avoiding excessive expansion and reducing the total energy
used to manufacture the cement. One example is to mix cement,
preferably portland cement, with latently hydraulic materials such
as ground granulated blast furnace slag. However, the latently
hydraulic materials do not react as quickly as portland cement, and
as a result they contribute to the later developed cement strength
rather than the earlier. The decreased early activity results in
lower heats of hydration, which leads to thermal crack formation.
However, the addition of blast furnace slag does not eliminate
thermal crack formation.
[0030] ASTM C125-99a "Standard Terminology Relating to Concrete and
Concrete Aggregates" defines a number of terms that apply to
hydraulic cement. It is well known in the prior art, that the
hydraulic properties of blast furnace slag vary greatly upon the
chemical nature of the blast furnace slag and the way that molten
slag is cooled.
[0031] Blast furnace slag is classified by performance in the blast
furnace slag activity test in three grades, Grade 80, Grade 100,
and Grade 120. ASTM specification C989 outlines the strength
development of portland cement mixed with the three strength grades
of finely ground, granulated blast furnace slag as measured at
seven days and twenty-eight days and expresses this as blast
furnace slag activity index (SAI). When blast furnace slag is used
in concrete with portland cement, the levels and rate of strength
development depend on the properties of the blast furnace slag, the
portland cement, the relative and total amounts of the blast
furnace slag and the cement as well as the cement curing
temperatures. Unless the slag is derived from a blast furnace it
cannot be marketed as blast furnace slag under the ASTM C989
standards.
[0032] ASTM C989 specifies that the reference cement used to test
blast furnace slag activity have a minimum 28-day strength of 35
MPa (5,000 psi) and an alkali content between 0.6 and 0.9%. To
properly classify a blast furnace slag, the reference portland
cement must conform to the limits on strength and alkali content
under ASTM specification C989. Test data indicate that concrete
compressive strengths at 1, 3 and even 7 days tend to be lower
using blast furnace slag cement combinations. Generally a higher
numerical grade of blast furnace slag can be used in larger amounts
and will provide improved early strength performance, but tests
must be made using job materials under job conditions to properly
access the performance of a blast furnace slag cement.
[0033] Blast furnace slag has latent hydraulic properties that
require an activator to realize these hydraulic properties. One way
for slag to acquire hydraulic properties is to rapidly quench the
slag to preserve the molten slag in a vitreous state. Two processes
that are commonly used to activate the slag's hydraulic properties
are granulation and pelletization. In the granulation process, slag
is quenched by the injection of a large quantity of water under
pressure into the slag. If the temperature of the slag is above its
melting point prior to quenching, then quenching produces a wet
sand-like material with a high degree of vitrification. But if the
slag is permitted to cool slowly, it crystallizes and exhibits
reduced hydraulic properties. To achieve the desired fineness, the
granulated slag is dried and ground. Blast furnace slags are
typically ground to a specific surface area of 5,000 to 6,500
cm.sup.2/g. A fineness of greater than 6,500 cm.sup.2/g requires
additional steps and is more difficult to achieve on a large
industrial scale under dry conditions. Another measure of specific
surface area is the Blaine air permeability method. The Blaine
Fineness test is described in ASTM C204 "Standard Test Method of
Hydraulic Cement by Air Permeability Apparatus." There, blast
furnace slags are described as having a specific surface area of
5,000 to 6,500 cm/.sup.2g. The early development of high strength
is a characteristic of cements comprising blast furnace slag ground
to a fineness of 7,500 cm.sup.2/g. As the fineness increases so
does the rate of the hardening reaction. As ground granulated blast
furnace slag typically has a fineness of about 5,000-6,500
cm.sup.2/g, an extra grinding step is required to achieve a
fineness of 7,500 cm.sup.2/g. There is an energy cost for the extra
grinding step, but it substantially improves the mechanical
strength of the resulting cement. Greater specific surface areas
generally result in greater initial strengths.
[0034] Cupola furnace slag can be granulated by the process of slag
quenching. Molten cupola furnace slag is granulated by the
injection into the slag of a large quantity of water under
pressure, producing a wet sand like material with a high degree of
vitrification. The degree of vitrification depends on the slag
temperature prior to injection and the temperature of the water
under pressure. Because cupola slag has a lower sulfate and
magnesium content and a higher silica and iron oxide content there
is a decrease in the heat generated, which is advantageous for
increasing setting time and slowing the initial strength gain of
the concrete. The lower sulfate and magnesia content coupled with a
higher silica and iron oxide content also leads to a reduction in
the expansions due to heat of hydration and alkali silica
reaction.
[0035] For the purpose of illustrating the advantages obtained by
the practice of the present invention, plain concrete mixes were
prepared and compared to similar mixes containing cupola slag. The
following example is illustrative and is not intended to be
limiting. The methods and details were in accordance with current
applicable ASTM standards.
EXAMPLE 1
[0036] Cupola furnace slag useful in cement compositions of the
present invention desirably shows the following components upon
analysis:
1TABLE 1 Composition of Cupola Slag Component Proportion (wt. %)
SiO.sub.2 43.87 Al.sub.2O.sub.3 8.5 Fe.sub.2O.sub.3 1.93 CaO 33.3
MgO 3.38 SO.sub.3 0.30 Na.sub.2O 0.10 K.sub.2O 0.30 TiO.sub.2 0.34
P.sub.2O.sub.5 <0.01 Mn.sub.2O.sub.3 1.18 SrO 0.08 L.O.I.
(950.degree. C.) 4.34 Total 97.84 Alkalies as Na.sub.2O 0.30
[0037] Although only applicable to blast furnace slag, the Slag
Activity Index test as described in ASTM C989 "Standard
Specification for Ground Granulated Blast Furnace Slag for Use in
Concrete" was performed on the cupola furnace slag as well as a
Blaine Fineness test as described in ASTM C204 "Standard Test
Method of Hydraulic Cement by Air Permeability Apparatus." Table 2
shows the results of these two tests for two different cupola slag
samples ground using a 40-lb mill to two different fineness values
similar to those of commercially available blast furnace slags.
2TABLE 2 Fineness and Slag Activity Index data Ground Cupola ASTM
C989 Slag Sample Requirement for: No. 1 No. 2 Grade 80 min Grade
100 min Fineness, cm.sup.2/g 4240 6530 -- -- Slag Activity At 7
days 61 73 -- 70 Index, % of At 28 days 98 124 70 90 control
[0038] As evident from Table 2, both samples exceeded the ASTM C989
SAI requirements for Grade 80 and Grade 100 blast furnace slag at
28 days. Sample 2 met the SAI 7 day requirements for Grade 100 as
well. Based on this test, all additional tests were preformed on
Sample 2
[0039] Conduction calorimetry tests were conducted on neat cement
pastes made with the control cement and with cupola furnace slag
blend by injection-mixing of 2 grams of cement with water inside a
calorimeter cell. The slag used in this test was Sample 2 as it met
the ASTM C989 Blast Furnace Slag Activity Index requirement for
7-day and 28-day of commercially available blast furnace slag Grade
100. The heat of hydration was recorded over a 72 hour period. The
first peak represents the heat reaction as the cement comes into
contact with the mix water. After the initial peak there is a
period of relative inactivity during which the paste remains
plastic. The second peak indicates an accelerated reaction during
which the alite in the cement hydrates rapidly and heat is
generated. The initial setting of the paste occurs soon after the
beginning of the acceleration period and the final setting occurs
towards the end of the acceleration period. A maximum in heat
evolution is reached soon after the final set, after which the heat
evolution declines to a steady state. The heat of hydration is a
function of both the chemical and the physical properties of the
cement. Table 3 shows the results of the calorimetry tests.
3TABLE 3 Heat Generation Data for Portland Cement and Cupola
Furnace Slag Blended Cement Control Cupola Slag Blend Rate of heat
Rate of heat generation Total Heat generation Total Heat
Description Time J/Kg/sec J/g Time J/Kg/sec J/g Initial 2.28 min
48.74 3.35 3.48 23.55 2.51 Hydration Peak Total Heat at: 0.5 hr
15.43 0.5 hr 11.07 Onset of Alite 2.15 hr 0.59 20.15 3.09 hr 0.51
17.26 Hydration Peak of Alite 11.20 hr 2.91 71.17 15.30 hr 2.70
89.28 Hydration Total Heat at: 24 hr 169.61 24 hr 140.91 Total Heat
at: 48 hr 235.70 48 hr 193.40 Total Heat at: 72 hr 264.33 72 hr
223.19
[0040] Table 3 indicates that the initial hydration peak for cupola
slag cement occurs later in time than that of the control cement
and generates heat at a much slower rate and generates a lot less
heat. Total heat one half hour after hydration is considerably
lower for cupola furnace slag as well. Another major difference
between the control cement and the cupola furnace slag cement is
that the onset of alite hydration and the peak of hydration are
both much later in the cupola slag cement than in the control.
Initially the total heat released for alite hydration is lower for
the cupola slag cement but by the time the peak of alite hydration
occurs, the total heat generated is higher for the cupola slag
cement than the control cement. Total heat released overall remains
lower for the cupola slag cement at each of the time periods
measured. It is anticipated that the surprising low-heat properties
of the cupola slag cement will make it particularly useful in
making concrete that is adapted for mass concrete pours such as
raft foundations, bridge decks, piers, and dams.
[0041] Resistance to sulfate attack on Sample 2 was tested in
accordance with ASTM C1012 "Standard Test Method for Length Change
of Hydraulic-Cement Mortars Exposed to a Sulfate Solution". The
expansion of the control and the blended cupola furnace slag cement
at 15 weeks was 0.026 and 0.015% respectively.
[0042] The potential for the cupola slag to modify alkali
reactivity was determined using ASTM C1260 "Standard Test Method
for Potential Alkali Reactivity of Aggregates (Mortar Bar Method)".
The cement used in this test was the cupola furnace slag bend of
sample 2, and the aggregate was a highly reactive graded
Albuquerque sand. Table 4 shows the results.
4TABLE 4 Expansion of Bars Due to Alkali Silica Reaction Expansion,
% Age, Days Control Cupola Slag Blend 0 0.000 0.000 5 0.009 0.013
11 0.349 0.77 14 0.580 0.195
[0043] Table 4 indicates that the potential of cupola slag to
modify alkali reactivity is considerably lower for cupola slag at
days 11 and 14 than the control.
[0044] Compression and flexural strengths of a blended cement
containing 35% cupola furnace slag (Sample 2) was measured at day
3, day 7, day 28, day 56 and day 90 and compared to a control
cement measured with the same age in days. No chemical additives
were added to either mix and the mixes were made with the same
cementitious content as well as the same water to cementitious
ratio. The mix portions of the two cements are shown in Table 5
while the results of the compression and flexural tests are shown
in Table 6.
5TABLE 5 Concrete Mix Proportions Mix Proportions Material Control
Cupola Slag Blend Portland Cement, pcy* 654 426 Slag, pcy 0 229 Eau
Claire sand, pcy 1,342 1,336 Eau Claire 3/4" stone, pcy 1,847 1,849
Water, pcy 266 267 Slump, inches 5 7 (*pounds per cubic yard)
[0045]
6TABLE 6 Compressive and Flexural Strength Results Compressive
Strength Flexural Strength (ASTM C39), psi (ASTM C78), psi Cupola
Slag Cupola Slag Age, Days Control Blend Control Blend 3 4,410
2,570 -- -- 7 5,530 4,320 785 490 28 7,150 7,780 750 755 56 7,530
8,740 770 750 90 7,710 8,630 -- --
[0046] Table 6 demonstrates that the cupola slag blended cement at
days 3 and 7 displays a lower compressive strength when measured
using the ASTM C29 method. By day 28, however, the compressive
strength of the cupola slag has surpassed that of the control
cement, a totally unexpected result. Additionally, the compressive
strength of the cupola slag blended cement unexpectedly continued
to increase until after day 56 where it begins to level off. At day
56 the compressive strength of the cupola slag blended cement is
more that 1,200 psi greater than the control cement. These tests
indicate the surprising result that the cupola slag blended cement
makes superior concrete over that made with conventional cements.
Table 6 demonstrates that the flexural strength of the cupola slag
blended cement as measured by the ASTM C78 method develops at a
slower rate than that of the control but after 28 days is
approximately equal to that of the control cement.
[0047] X-Ray Diffraction Analysis
[0048] X-ray diffraction may be used to identify and quantify
crystalline materials. Crystalline materials consist of ordered
arrangements of atoms in three-dimensional arrays. Such arrays have
characteristic spacings between the layers of closely packed atoms.
The length of the spacings vary by atom size and the three
dimensional arrays.
[0049] When a powdered sample is subjected to a beam of radiation
from an X-ray source a diffraction pattern is created. The X-ray
beam penetrates the powder a short distance and diffracts from the
most densely packed layers of the atoms within the powdered sample.
The X-ray beam is rotated through a series of angles relative to
the surface of the powdered sample. When the signal from the
diffracted beam is particularly strong, the distances between
layers of atoms (the d-spacings) can be calculated as multiples of
the wavelengths of the incident radiation and the incident
angle.
[0050] A crystalline material has a characteristic pattern of
relative peak heights at given angles. Mixtures of crystalline
materials display combinations of these patterns and the relative
peak heights from various materials can be used to quantify the
relative concentration of each crystalline material. X-ray
diffraction may also be used to identify cracks in concrete. The
detection limit for X-ray will depend on the type of material
analyzed and it can be as high as 5 to 10%.
[0051] A ground granulated cupola furnace slag sample was finely
powdered and subjected to XRD analysis on a Philips PW 1720 X-ray
diffractometer (CuK.theta.) equipped with a .theta.-compensating
slit, graphite monochromator, gas proportional counter detector,
pulse height selector and a strip chart recorder. A commercial
granulated blast furnace slag sample was also finely powdered and
analyzed as a control. Each sample was scanned from
65.degree.2.theta. to 6.degree.2.theta. at a rate of
1.degree.2.theta. per minute. Table 7 is a summary of the phases
detected by XRD.
7TABLE 7 X-ray Diffraction Analysis Sample Largest Phase Detected
Crystalline material Cupola Furnace Slag Amorphous material with a
SiO.sub.2 (.alpha.-quartz) peak at 29.8.degree. 2.theta. Blast
Furnace Slag Amorphous material with a CaCO.sub.3 (calcite) peak at
31.degree. 2.theta.
[0052] As can be seen from Table 7, the two slag samples vary in
their crystalline composition as well as their non-crystalline or
glassy composition. The cupola slag sample has an amorphous phase
peak at 29.8.degree.2.theta. (lower angle) indicating a larger
d-spacing than that of the blast furnace slag. The XRD analysis
also shows that crystalline SiO.sub.2 is present in the cupola slag
which suggests a more acidic form of the amorphous phase. The
amorphous phase of the cupola slag probably contains of higher
amounts of not only SiO.sub.2 but also Al.sub.2O.sub.3 and
Fe.sub.3O.sub.3 than the blast furnace slag.
[0053] All references and standards cited herein are incorporated
in their entireties.
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