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CHAPTER SIX: CONCRETE TESTING PROGRAM
6.1 Introduction
As the last testing program in this study, concrete tests were conducted to
investigate the effect of MFA on the properties of concrete after performing
screening, aggregate characterization tests, and mortar tests. The following
sections outline the materials, the test procedures, and the results and discussion of
concrete tests using the selected sands based on the mortar test results. Using the
concrete test results, a case study using one sample was performed to investigate
the effect of micro fines content on the properties of concrete.
6.2 Materials
6.2.1 Portland Cement
Type I cement was used in the concrete tests. It conformed to ASTM C
150-94, Standard Specification for Portland Cement.
6.2.2 Coarse Aggregate
The same coarse aggregate was used in the overall concrete batches,
namely dolomitic limestone (3/4-inch Gravel ASTM #67, from the Gifford-Hill
Company at Garden Ridge Plant in New Braunfels, Texas). The properties of the
coarse aggregate are given in Tables 6.1.
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Table 6.1: Properties of Coarse Aggregate Used in Concrete Batches
TxDHT
MethodProperties Results
TxDHT Item 302
Specification
TEX-403-A Bulk Specif ic Gravity (OD) 2.57
TEX-403-A Absorption (%) 2.9
TEX-404-A Unit Weight (dry rodded), lbs/CF 95.3
TEX-404-A Unit Weight (dry loose), lbs/CF 86.5
TEX-405-A Void Content, (dry rodded), % 40.6
TEX-410-A L.A. Abrasion, % loss 27.5 35% Max.TEX-411-A
Soundness by Na2SO4,
(5 cycles), % loss3.77 12% Max.
TEX-411-ASoundness by MgSO4,
(5 cycles), % loss3.88 25% Max.
TEX-412-A Light Weight Pieces, % 0.0 0.5% Max.
TEX-413-A Clay Lumps and Friable Particles, % 0.0 5.0% Max.
TEX-612-J Acid Insoluble Residue, % 6.5
The gradation of the coarse aggregate and the gradation of ASTM C 33-97,
Standard Specification for Concrete Aggregate are shown in Table 6.2.
Table 6.2: Gradation of Coarse Aggregate Used in Concrete Batches
Sieve SizePercentage Passing,
By WeightASTM C33-97
1 in. (25.0 mm) 100 100
in. (19.0 mm) 100 95 to 100
in. (12.5 mm) 97
3/8 in. (9.5 mm) 20 20 to 55
No.4 (4.75 mm) 1 0 to 10
No.8 (2.36 mm) 1 0 to 5
No.16 (1.18 mm) 0
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6.2.3 Fine Aggregate
Table 6.3 shows the representative aggregates of each type of rock that was
used for mortar tests. The aggregates were selected based on the mortar test
results and each representative sample was selected on the following basis:
1) At least one sample per aggregate type;
2) The sands of higher 28-day compressive strength;
3) The sands of lower 28-day drying shrinkage; and
4) The sands with higher amounts of micro fines
As a result 11 sands were selected, and a natural sand was used as control.
Since the properties of Virginia limestone have been better when compared to the
other samples, all three samples were selected for the concrete tests.
Table 6.3: Aggregates for Concrete Test
ID No. Location Type Size, mm Speed, m/s Cycle
PA/LS/05-00/65 Pennsylvania Limestone 05-00 65 Product
VA/GT/05-00/68 Virginia Granite 05-00 68 Product
SD/QZ/06-00/65 South Dakota Quartzite 06-00 65 Product
VA/DI/06-00/65 Virginia Diabase 06-00 65 Product
OK/DO/06-00/65 Oklahoma Dolomite 06-00 65 ProductVA/LS/05-00/00 05-00 00 as-received
VA/LS/05-00/65 05-00 65 Product
VA/LS/05-00/36
Virginia Limestone
05-00 36 Product
CT/BA/19-02/68 Connecticut Basalt 19-02 68 Product
PA/SS/09-00/68 Pennsylvania Sandstone 09-00 68 Product
MO/LS/06-00/00 Missouri Limestone 06-00 00 as-received
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6.2.4 Mixing Water
Potable City of Austin water was used throughout the laboratory batching
series and was assumed to have a specific gravity of 37 kg/m3 (62.4 lbs/cy).
6.2.5 Chemical Admixtures
No chemical admixtures were used in this study in order to investigate the
effect of higher micro fines on the properties of concrete without admixtures. For
fixed slump batches, only the water content was changed to get the targeted slump
(thus the water-cement ratio was changed).
6.3 Testing Procedures for Concrete Tests
All laboratory mixing was conducted in a 0.17-m3 (6-ft3) capacity rotary
drum mixer, shown in Figure 6.1. ASTM C 192-94, Standard Practice for
Making and Curing Test Specimens in the Laboratory was followed for batching
and making test specimens in the laboratory. All materials reached room
temperature (equilibrium) at 21.1 to 22.8C (70 to 73F) prior to batching. Mixing
water was adjusted accordingly based on the moisture conditions of the coarse and
fine aggregates approximately one-half hour prior to batching.
Concrete tests included both fresh concrete tests and hardened concrete
tests. The test procedures are discussed in the following section.
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Figure 6.1: Rotary Mixing Unit Used for Concrete Batches
6.3.1 Fresh Concrete Testing
6.3.1.1Slump
The slump test was conducted in accordance with ASTM C 143-97,
Standard Test Method for Slump of Hydraulic-Cement Concrete and ASTM C
172 Practice for Sampling Freshly Mixed Concrete.
6.3.1.2Vebe
The Vebe test was performed in accordance with ASTM C 1170, Standard
Test Methods for Determining Consistency and Density of Roller-Compacted
Concrete Using a Vibrating Table. The Vebe test was performed to evaluate
workability for very low slump concrete. The difference between the slump and
Vebe test is that one is a static test and another is a dynamic test. Since the slump
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test is not adequate to investigate the workability of low slump concrete, the Vebe
test was performed in this study.
After filling and dampening a minimum mass of 22.7 kg (50 lb) of fresh
concrete the vibrator and timer were started. When the mortar ring formed
completely around the surcharge, the vibrator and timer were stopped. The
elapsed time was the Vebe consistency time.
6.3.1.3Temperature
The temperature test was performed in accordance with ASTM C 1064-93,
Standard Test Method for Temperature of Freshly Mixed Portland Cement
Concrete. A digital thermometer (accuracy: 0.1F) was used to determine the
temperature of the fresh concrete. The temperature was measured after a
minimum of two minutes or when the temperature reading stabilized.
6.3.1.4Unit Weight and Air Content
The unit weight and air content tests were conducted in accordance with
ASTM C 138-92, Standard Test Method for Unit Weight, Yield, and Air Content
(Gravimetric) of Concrete. Used 0.01-m3
(0.4-ft3) stainless steel container unit
weight and air content of fresh concrete were calculated simultaneously.
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6.3.2 Preliminary Hardened Concrete Testing
The hardened concrete performance-related tests included compressive
strength, flexural strength, drying shrinkage, rapid chloride permeability, abrasion
resistance, and scaling resistance by deicing chemicals.
6.3.2.1Compressive Strength
The compressive strength tests were performed in accordance with ASTM
C 39-96 Standard Test Method for Compressive Strength of Cylindrical Concrete
Specimens using a 270-kg (600-kip) capacity hydraulically operated compression
test machine as shown in Figure 6.2. Three cylinder specimens (4-inch diameter
and 8-inch height) were prepared for each mixture. The specimens were loaded at
a rate of 0.24 0.10 MPa per second (35 15 psi per second) until complete
failure. Neoprene pads inserted in steel retaining caps were used throughout this
study in the compressive strength tests of cylinders.
6.3.2.2Flexural Strength
The flexural strength test (modulus of rupture) was performed according to
ASTM C 78-94 Standard Test Method for Flexural Strength of Concrete (Using
Simple Beam with Third-Point Loading). Three prisms, 75-mm75-mm275-
mm (3-in.3-in.11-in.), were prepared for each mixture. The specimens were
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loaded at a rate of 1.04 0.07 MPa per minute (150 25 psi per minute) until
rupture occurred.
Figure 6.2: Compressive Strength Forney - Hydraulically Operated600 kip Capacity Multiple Loading Rate Machine
6.3.2.3Drying Shrinkage
The drying shrinkage test was conducted in accordance with ASTM C 157-
93, Standard Test Method for Length Change of Hardened Hydraulic-Cement
Mortar and Concrete. Three prisms, 75-mm
75-mm
275-mm (3-in.
3-in.
11-
in.), were prepared for each mixture. The specimens were made and cured in the
lime-saturated water for 28 days. After removal from the lime-saturated water, the
specimens were stored in the drying room, and comparator readings for each
specimen were taken as required by the standard test procedure.
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6.3.3 Final Hardened Concrete Testing
6.3.3.1Chloride Ion Penetration
The chloride ion penetration test (permeability) was performed in
accordance with ASTM C 1202-97 Standard Test Method for Electrical
Indication of Concretes Ability to Resist Chloride Ion Penetration. Three
cylinder specimens (4-inch diameter and 8-inch height) were prepared for each
mixture. Using 2-inch thickness specimens the amount of chloride ion penetration
was measured as electrical charge (coulombs).
6.3.3.2Abrasion Resistance
The abrasion resistance test was conducted at 28 days on three companion
specimens in accordance with ASTM C 944-99 Standard Test Method for
Abrasion Resistance of Concrete or Mortar Surfaces by the Rotating Cutter
Method. The testing machine, shown in Figure 6.3, consisted of a drill press
rotating at a speed of 200 rpm exerting a force of 98 N (10 kgf) on the surface
being tested. The rotating cutter consisted of 24 grinding dressing wheels. Six-
minute periods of abrasion were performed on every surface tested. The depth of
wear on the surface of the specimen was measured to determine the abrasion
resistance of the concrete. The average of three readings at each measuring time
was used as the depth of wear for each sample.
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Figure 6.3: Rotating Cutting Machine for Abrasion Resistance Test
6.3.3.3Scaling Resistance by Deicing Chemicals
The scaling resistance test was performed in accordance with ASTM C
672-92, Standard Test Method for Scaling Resistance of Concrete Surfaces
Exposed to Deicing Chemicals. Prior to initiating the test a stainless steel dam
was built around the edges of the specimens to hold salt solution in place. The
deicing agent used consisted of a 3 percent solution of calcium chloride. A visual
inspection of the test specimens was made after each cycle. The damage was
assessed according to ASTM C 672-92 on a scale from 0 to 5 with zero indicating
no deterioration and 5 indicating severe damage.
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6.4 Mixture Proportioning
As in the mortar testing program, two control variables were used in the
concrete testing program: fixed water-cement ratio and fixed slump (workability)
of concrete batches. The first variable was selected to investigate the effect of
MFA on the properties of concrete at the same water-cement ratio, and the last one
was chosen to evaluate the effect of the property change according to water
demand without any chemical admixture.
Since the gradation of MFA did not meet the ASTM C33 specification,
normal mixture proportioning did not apply to MFA concrete batches. Hence, the
mixture proportioning of MFA concrete was performed using a volumetric
method.
The cement content used in concrete batches was the minimum 5 sacks per
cubic yard of concrete following the TxDOT specification. All concrete batches
had the same cement content. Since the cement content was fixed, water content
depended on the water-cement ratio. According to a recent concrete project by
Vulcan using Calera aggregate, an optimal value of sand used in concrete was
found to be 42 percent based on the total aggregate volume of concrete. Hence
subtracting the volume of cement, water, and entrapped air from total concrete
volume, 42 percent and 58 percent of the remaining volume was for fine aggregate
and coarse aggregate, respectively. The mixture proportioning of concrete batches
is shown in Tables 6.4 (fixed w/c) and 6.5 (fixed slump).
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Table 6.4: Mixture Proportioning of Concrete Batches (Fixed W/C)
ID No.Cement
(lb)
Water
(lb)
Fine Agg.
(lb)
Coarse Agg
(lb)
Natural Sand-F 41.8 22.1 100.1 122.0
PA/LS/05-00/65-F 41.8 22.1 90.4 129.6
VA/GT/05-00/68-F 41.8 22.1 98.9 128.6
SD/QZ/06-00/65-F 41.8 22.1 95.8 128.8
VA/DI/06-00/65-F 41.8 22.1 101.4 128.6
OK/DO/06-00/65-F 41.8 22.1 98.2 128.6VA/LS/05-00/00-F 41.8 22.1 102.2 128.6
VA/LS/05-00/65-F 41.8 22.1 102.5 128.6
VA/LS/05-00/36-F 41.8 22.1 102.2 128.6
CT/BA/19-02/68-F 41.8 22.1 102.2 128.6
PA/SS/09-00/68-F 41.8 22.1 95.6 128.8
MO/LS/06-00/00-F 41.8 22.1 92.8 128.6
Table 6.5: Mixture Proportioning of Concrete Batches (Fixed Slump)
ID No.Cement
(lb)
Water
(lb)
Fine Agg.
(lb)
Coarse Agg
(lb)
Natural Sand-V 41.8 21.4 108.0 116.4
PA/LS/05-00/65-V 41.8 22.1 90.4 129.6
VA/GT/05-00/68-V 41.8 22.1 98.9 128.6
SD/QZ/06-00/65-V 41.8 23.4 94.4 126.8
VA/DI/06-00/65-V 41.8 25.0 98.0 124.2
OK/DO/06-00/65-V 41.8 23.0 97.2 127.4
VA/LS/05-00/00-V 41.8 23.0 101.2 127.4
VA/LS/05-00/65-V 41.8 22.1 102.5 128.6
VA/LS/05-00/36-V 41.8 22.1 102.2 128.6
CT/BA/19-02/68-V 41.8 23.4 100.6 126.8
PA/SS/09-00/68-V 41.8 23.0 94.4 127.4
MO/LS/06-00/00-V
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6.5 Test Results and Discussion
In accordance with required test methods specimens were prepared and
tested. The following section presents concrete test results and discussion of these
results.
6.5.1 Fresh Concrete Testing
6.5.1.1Slump
The slump test results are shown in Table 6.6. The fixed water-cement
ratio was 0.53, and the fixed slump was 2 to 4 inches. As shown in the table,
control batches using natural sand had high slump (7.5 inches) compared to that of
the MFA batches for fixed water-cement ratio. The reason for lower slump for
MFA batches is that the excess water is not enough to lubricate all aggregates due
to high content of micro fines. For Missouri limestone, due to lack of workability
the batch could not be made. For fixed slump batches, most batches needed more
water to reach the targeted slump (2 ~ 4 inches) except the control batch. A water-
cement ratio of 0.51 was enough to gain the targeted slump for the control batch.
To increase the slump excess water cannot be added in the field since the
extra water affects the quality of the concrete. Hence, it is concluded that
chemical admixtures are needed to increase the slump of high micro fines concrete
without increasing water content.
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6.5.1.2Vebe
The test results for Vebe time are shown in Table 6.6. It should be noted
that low slump batches had low Vebe times for a fixed water-cement ratio. Even if
a concrete batch had low slump it could have been a workable batch due to short
compacting time. Hence, it is concluded that the slump test is not adequate to
evaluate the workability of concrete batches. However the Vebe test also has a
disadvantage in that the variance of the test results can be high depending on the
investigator. For future research other test methods for workability evaluation
should be considered.
6.5.1.3Temperature
Table 6.6 shows the test results for concrete temperature. As shown in the
table there was no significant temperature change for fixed water-cement and fixed
slump concrete batches. The reason is that the same amount of cement was used
regardless of fixed water-cement ratio or fixed slump, and no chemical admixtures
were used to the concrete batches. The concrete temperature was 22.8C ~ 24.1C
(73.1F ~ 75.4F).
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Table 6.6: Test Results of Slump, Vebe, and Temperature of Concrete
ID No. W/CSlump
(ln.)
Vebe Time
(Sec)
Temperature
(F)
Natural Sand-F 0.53 7.50 1.0 73.8
PA/LS/05-00/65-F 0.53 2.75 3.0 73.9
VA/GT/05-00/68-F 0.53 3.25 4.0 74.0
SD/QZ/06-00/65-F 0.53 0.75 6.0 73.5
VA/DI/06-00/65-F 0.53 1.25 7.0 74.3
OK/DO/06-00/65-F 0.53 1.50 5.0 75.0
VA/LS/05-00/00-F 0.53 1.50 15.0 74.6
VA/LS/05-00/65-F 0.53 2.00 4.0 74.8
VA/LS/05-00/36-F 0.53 2.00 8.0 75.4
CT/BA/19-02/68-F 0.53 0.75 12.0 74.9
PA/SS/09-00/68-F 0.53 1.50 7.0 73.1
MO/LS/06-00/00-F 0.53 0.0
Natural Sand-V 0.51 3.75 2.0 74.5
PA/LS/05-00/65-V 0.53 2.75 3.0 73.9
VA/GT/05-00/68-V 0.53 3.25 4.0 74.0
SD/QZ/06-00/65-V 0.56 3.00 2.0 74.4
VA/DI/06-00/65-V 0.60 3.50 6.0 75.0
OK/DO/06-00/65-V 0.55 2.75 5.0 74.5
VA/LS/05-00/00-V 0.55 3.75 4.0 74.3
VA/LS/05-00/65-V 0.53 2.00 4.0 74.8
VA/LS/05-00/36-V 0.53 2.00 8.0 75.4
CT/BA/19-02/68-V 0.56 2.75 4.0 74.6
PA/SS/09-00/68-V 0.55 2.50 6.0 74.5
MO/LS/06-00/00-V
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6.5.1.4Unit Weight and Air Content
The test results for unit weight and air content are shown in Table 6.7. As
shown in the table, for either fixed water-cement ratio or fixed slump, the unit
weight of MFA batches was higher than that of the control batch. Since higher
micro fines filled the voids among aggregate particles. Usually the concrete
batches with higher unit weight had lower air contents since air content is directly
related to air voids among aggregate particles and particle shape. Hence, it is
concluded that the MFA concrete batches usually have higher unit weight and
lower air contents than those of control batches due to higher content of micro
fines. Virginia limestone had the highest unit weight and the lowest air content
which results in dense and less permeable concrete.
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Table 6.7: Test Results of Unit Weight and Air Content of Concrete
ID No. Unit Weight (lb/ft3) Air Content (%)
Natural Sand-F 144.9 2.6
PA/LS/05-00/65-F 147.1 0.8
VA/GT/05-00/68-F 150.1 1.3
SD/QZ/06-00/65-F 148.7 0.9
VA/DI/06-00/65-F 150.7 0.6
OK/DO/06-00/65-F 148.7 0.9
VA/LS/05-00/00-F 151.4 1.2
VA/LS/05-00/65-F 152.7 0.3
VA/LS/05-00/36-F 152.7 0.2
CT/BA/19-02/68-F 152.6 0.6
PA/SS/09-00/68-F 148.7 0.8
MO/LS/06-00/00-F
Natural Sand-V 146.8 1.8PA/LS/05-00/65-V 147.1 0.8
VA/GT/05-00/68-V 150.1 1.3
SD/QZ/06-00/65-V 146.8 1.3
VA/DI/06-00/65-V 148.7 1.1
OK/DO/06-00/65-V 148.7 1.3
VA/LS/05-00/00-V 150.0 1.6
VA/LS/05-00/65-V 152.7 0.3
VA/LS/05-00/36-V 152.7 0.2
CT/BA/19-02/68-V 151.3 0.7
PA/SS/09-00/68-V 147.4 1.0
MO/LS/06-00/00-V
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6.5.2 Preliminary Hardened Concrete Testing
6.5.2.1Compressive Strength
The test results for compressive strength for each type of aggregate are
shown in Table 6.8 and Figures 6.4 and 6.5. For fixed water-cement ratio most
MFA concretes showed higher compressive strength at 7 and 28 days than the
control batch, except for Connecticut basalt. The reason of higher compressive
strength for MFA concrete is that higher micro fines filled the voids among
aggregate particles and the bond between aggregate particles and cement paste was
better due to angular MFA as a result of crushing. The compressive strength of
Virginia limestone was 28 percent higher than the control batch.
On the other hand for fixed slump, the compressive strength of the control
batch was higher than for most MFA concretes. The differences in compressive
strength at 7 and 28 days, however, between control batch and most MFA concrete
batches were at most 10 percent. Hence, if chemical admixtures are used to
increase the workability for MFA concrete, the compressive strength could be
improved compared to that of natural sand concrete.
6.5.2.2Flexural Strength
The Table 6.8 and Figures 6.6 and 6.7 show 7-day flexural strengths for
each type of aggregate. It should be noted that the flexural strengths of most MFA
concretes were higher than for the control batch for either fixed water-cement ratio
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or fixed slump. Even though the relationship between compressive and flexural
strength is usually proportional in a typical concrete batch using natural sand, the
relationship cannot be applied to MFA concrete batches. The reason for a
different relationship between compressive and flexural strength for MFA concrete
is that some characteristics of MFA (such as higher micro fines, particle shape and
texture) improve the flexural capacity of concrete compared to those of natural
sand. Hence, it is concluded that the usual relationship between compressive and
flexural strength does not apply to MFA concrete, since some characteristics of
MFA improves the flexural capacity.
6.5.2.3Drying Shrinkage
The test results for drying shrinkage are shown in Table 6.8 and Figures 6.8
and 6.9. As shown in the figures, the drying shrinkages of most MFA concrete
were higher than that of the control batch. In the table and the figures, it is noted
that even though the water-cement ratio is the same the drying shrinkage of
concrete could be different according to the type of rock. Since the drying
shrinkage is related to a restraining influence of aggregate, the amount of
aggregate in the concrete and the stiffness of aggregate affect the drying shrinkage
of concrete. However, the water demand is the most important factor affecting the
drying shrinkage, hence it is concluded that to reduce drying shrinkage in MFA
concrete, chemical admixtures should be used to reduce the amount of water.
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Table 6.8: Test Results of Compressive Strength, Flexural Strength,
and Drying Shrinkage of Concrete
Compressive
Strength (psi)ID No.
7 days 28 days
Flexural
Strength
at 7 days (psi)
Drying
Shrinkage
at 28 days (%)
Natural Sand-F 3430 4680 580 0.013
PA/LS/05-00/65-F 3840 4850 730 0.021
VA/GT/05-00/68-F 3870 5120 670 0.016
SD/QZ/06-00/65-F 3990 5370 680 0.010
VA/DI/06-00/65-F 4290 5440 690 0.020
OK/DO/06-00/65-F 4150 5290 680 0.017
VA/LS/05-00/00-F 4950 5990 790 0.011
VA/LS/05-00/65-F 3950 4900 730 0.012
VA/LS/05-00/36-F 3920 5200 720 0.007
CT/BA/19-02/68-F 3360 4310 650 0.013
PA/SS/09-00/68-F 4240 5290 710 0.011
Natural Sand-V 3970 5260 660 0.009
PA/LS/05-00/65-V 3840 4850 730 0.021
VA/GT/05-00/68-V 3870 5120 670 0.016
SD/QZ/06-00/65-V 3810 5020 670 0.012
VA/DI/06-00/65-V 3660 4820 620 0.020
OK/DO/06-00/65-V 3990 5070 680 0.017
VA/LS/05-00/00-V 2670 3710 720 0.017
VA/LS/05-00/65-V 3950 4900 730 0.012
VA/LS/05-00/36-V 3920 5200 720 0.007
CT/BA/19-02/68-V 2860 4230 600 0.021
PA/SS/09-00/68-V 3500 4900 680 0.018
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1000
2000
3000
4000
5000
6000
28-dayCompressiveStrength(psi)
Control LS(PA) GT QZ DI DO LS(VA)1 LS(VA)2 LS(VA)3 BA
Type of Aggregate
Figure 6.4: Twenty-eight-day Concrete Compressive Strength for Each Type of Aggrega
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1000
2000
3000
4000
5000
6000
28-dayC
ompressiveStrength(psi)
Control LS(PA) GT QZ DI DO LS(VA)1 LS(VA)2 LS(VA)3 BA
Type of Aggregate
Figure 6.5: Twenty-eight-day Concrete Compressive Strength for Each Type of Aggrega
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100
200
300
400
500
600
700
800
7-day
FlexuralStrength(psi)
Control LS(PA) GT QZ DI DO LS(VA)1 LS(VA)2 LS(VA)3 BA
Type of Aggregate
Figure 6.6: Seven-day Concrete Flexural Strength for Each Type of Aggregate (Fi
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100
200
300
400
500
600
700
800
7-day
FlexuralStrength(psi)
Control LS(PA) GT QZ DI DO LS(VA)1 LS(VA)2 LS(VA)3 BA
Type of Aggregate
Figure 6.7: Seven-day Concrete Flexural Strength for Each Type of Aggregate (Fix
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14 28 42 56 70 84 98 112
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040Control
LS(PA)
GT
QZ
DI
DO
LS(VA)1LS(VA)2
LS(VA)3
BA
SS
DryingShrinkage(%)
Time (days)
Figure 6.8: Drying Shrinkage of Concrete for Each Type of Aggregate
(Fixed W/C)
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14 28 42 56 70 84 98 112
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040Control
LS(PA)
GT
QZ
DI
DO
LS(VA)1LS(VA)2
LS(VA)3
BA
SS
DryingShrinkage(%)
Time (days)
Figure 6.9: Drying Shrinkage of Concrete for Each Type of Aggregate
(Fixed Slump)
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6.5.3 Final Hardened Concrete Testing
Based on the fresh and preliminary hardened concrete test results, three
samples (South Dakota quartzite, Oklahoma dolomite, and Virginia limestone)
were selected for final concrete testing. Those three samples were tested using
fixed slump batches. The following section presents the test results of final
hardened concrete testing using natural sand and selected three samples.
6.5.3.1Chloride Ion Permeability
Table 6.9 shows the chloride ion permeability based on charge passed
(ASTM C1202). As shown in the table, typical concrete, which has moderate
permeability, shows 2,000 to 4,000 coulombs.
The test results of chloride ion permeability using selected samples are
shown in Table 6.10 and Figures 6.10 and 6.11. As shown in the figures for fixed
water-cement ratio, all MFA concretes showed less 28-day adjusted charge passed
than that of the control batch. As mentioned above, the reason for lower
permeability for MFA concretes is that higher micro fines fill the voids among
aggregate particles and it results in making less permeable concrete. The
permeability of most MFA concrete, however, was high (over 4000 coulombs)
regardless of fixed water-cement ratio or fixed slump. It is recommended that
mineral admixtures (such as fly ash, silica fume, etc) be used to make less
permeable MFA concrete.
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Table 6.9: Chloride Ion Permeability Based on Charge Passed (ASTM C1202)
Charge Passed (coulombs) Chloride Ion Permeability
>4,000 High
2,000 ~ 4,000 Moderate
1,000 ~ 2,000 Low
100 ~ 1,000 Very Low
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1000
2000
3000
4000
5000
6000
28-dayAdjuste
dChargePassed(Coulombs)
Control LS(PA) GT QZ DI DO LS(VA)1 LS(VA)2 LS(VA)3
Type of Aggregate
Figure 6.10: Chloride Ion Permeability of Concrete for Each Type of Aggregate (F
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0
1000
2000
3000
4000
5000
6000
28-dayAdjustedChargePassed
(Coulombs)
Control QZ DO LS(VA)3
Type of Aggregate
Figure 6.11: Chloride Ion Permeability of Concrete
for Each Type of Aggregate(Fixed Slump)
6.5.3.2Abrasion Resistance
The test results for abrasion resistance are shown in Table 6.10 and Figures
6.12 and 6.13. Similar to the permeability results, for fixed water-cement ratio, all
MFA concretes showed less 28-day abrasion loss than that of the control batch,
due to higher micro fines and more angular particle shape than natural sand. As
shown in Figure 6.12 for fixed slump, even though the abrasion loss of the control
batch concrete was lower than that of MFA concretes the difference was not
significant. Hence, it is concluded that if chemical admixtures are used to improve
workability, abrasion loss of MFA concrete can be improved compared to natural
sand concrete.
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0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
28-dayA
brasionLossinMass(%)
Control QZ DO LS(VA)3
Type of Aggregate
Figure 6.12 Abrasion Loss of Concrete in Mass
for Each Type of Aggregate (Fixed Slump)
6.5.3.3Scaling Resistance by Deicing Chemicals
Table 6.11 shows the scaling rating according to the surface condition
based on ASTM C672. The rating is determined visually and is subjective. The
specimens were subjected to one cycle per day.
The test results for scaling resistance are shown in Table 6.12. The table
gives the number of cycles required to reach each scaling. As shown in the table
all MFA concretes required more cycles to reach rating 5 (severe scaling) than
those of the control batch. The number of cycles, however, was smaller than the
50 cycles that typical concretes require.
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0
0.05
0.1
0.15
0.2
0.25
28-dayAbrasionLossinMass(%)
Control LS(PA) GT QZ DI DO LS(VA)1 LS(VA)2 LS(VA)3 B
Type of Aggregate
Figure 6.13: Abrasion Loss of Concrete in Mass for Each Type of Aggregate (Fix
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Since the air content of the batches was lower than 2 percent (entrapped
air). Generally speaking, to resist freezing and thawing for a reasonable period of
time, the air content of the concrete should be at least 4 percent. Hence it is
recommended that AEA (air entrainment agent) be used to produce more than 4
percent air content in the MFA concretes.
Table 6.11: Rating of Scaling Based on Condition of Surface (ASTM C 672)
Rating Condition of Surface
0 No scaling
1Very slight scaling
(1/8 in. (3.2 mm) depth, max, no coarse aggregate visible)
2 Slight to moderate scaling
3 Moderate scaling (some coarse aggregate visible)4 Moderate to severe scaling
5 Severe scaling (coarse aggregate visible over entire surface)
Table 6.12: Test Results of Scaling of Concrete by Deicing Chemicals
Needed Cycles to Reach Each Scaling RatingID No.
Rating 1 Rating 2 Rating 3 Rating 4 Rating 5
Natural Sand-V 1 3 5 10 14
SD/QZ/06-00/65-V 6 14 19 24 28
OK/DO/06-00/65-V 1 3 5 14 19
VA/LS/05-00/36-V 3 6 10 14 19
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6.6 Case Study
Based on the concrete test results, one sample (VA/LS/05-00/65) was
selected for a case study. The case study was performed to investigate the effect
of micro fines content on the properties of hardened concrete. A control batch
using natural sand was made to compare the results. The following sections
outline the materials, the test procedures, mixture proportioning, and the results
and discussion of the case study.
6.6.1 Materials
Based on the methylene blue test results and fresh and hardened concrete
test results, it was found that Virginia limestone (VA/LS/05-00/65) was the best
aggregate used. Hence, all micro fines of the sample were sieved and prepared.
The sample contains 13 percent micro fines. Extra micro fines were added to
make 17 percent and 20 percent of micro fines content samples. The same type I
cement used in the concrete tests, was used in the case study. No chemical
admixtures were used in this case study.
6.6.2 Testing Procedures
Since the case study was conducted to investigate the effect of micro fines
content on the properties of hardened concrete, fresh concrete tests except the
slump test were not performed. Compressive strength at 28 days (ASTM C39),
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flexural strength at 7 days (ASTM 78-94), drying shrinkage (ASTM 157-93), and
chloride ion penetration test (ASTM C1202-97) were performed. The test
procedures were discussed in the Section 6.3.2 and 6.3.3.
6.6.3 Mixture Proportioning
The same cement content (5 sacks per cubic yard of concrete) was used in
concrete batches of the case study. In addition the same ratio (0.42) of sand/total
aggregate by volume was used. The only difference in the mixture proportions
was the micro fines content per batch (13%, 17%, and 20%). The different micro
fines contents resulted in different specific gravity and absorptions.
6.6.4 Test Results and Discussion
6.6.4.1Compressive Strength
The test results for compressive strength for different micro fines contents
of Virginia limestone are shown in Table 6.13 and Figure 6.14. As shown in the
figure, with increasing micro fines content the 28-day compressive strength was
slightly decreased. Since the batches used fixed slump, the batch using 20 percent
micro fines obviously needed more water. As a result the compressive strength
was decreased. If chemical admixtures were used to increase the workability,
compressive strength could be improved. Hence, it is concluded that if the MBV
is low (less than 0.5) and chemical admixtures are used to improve workability of
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concrete batch, 20 percent of micro fines content can likely be used to make good
quality concrete.
Table 6.13: Test Results of Compressive Strength and Flexural Strength
of Concrete for Different Micro Fines Content of Virginia Limestone
ID No.
Compressive
Strengthat 28 days (psi)
Flexural
Strengthat 7 days (psi)
Natural Sand-V (3%) 5260 660
VA/LS/05-00/65-V (13%) 4900 730
VA/LS/05-00/65-V (17%) 4850 710
VA/LS/05-00/65-V (20%) 4530 700
0
800
1600
2400
3200
4000
4800
5600
28-d
ayCompressiveStrength(psi)
Natural Sand 13% 17% 20%
Control vs Micro Fines Content of Virginia Limestone
Figure 6.14: Twenty-eight-day Concrete Compressive Strength
for Different Micro Fines Contents of Virginia Limestone (Fixed Slump)
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6.6.4.2Flexural Strength
The test results for flexural strength for different micro fines content of
Virginia limestone are shown in Table 6.13 and Figure 6.15. It should be noted
that all MFA concretes with 13, 17, and 20 percent micro fines contents showed
higher flexural strengths than that of the control batch. As mentioned in section
6.5.2.2, MFA with higher micro fines improves the flexural capacity of concrete
compared to those of natural sand for the same conditions. If chemical admixtures
are used the difference could be larger.
600
620
640
660
680
700
720
740
7-dayFlexuralStrength(psi)
Natural Sand 13% 17% 20%
Control vs Micro Fines Content of Virginia Limestone
Figure 6.15: Seven-day Concrete Flexural Strength
for Different Micro Fines Content of Virginia Limestone (Fixed Slump)
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6.6.4.3Drying Shrinkage
The test results for drying shrinkage for different micro fines contents of
Virginia limestone are shown in Table 6.14 and Figure 6.16. As shown in the
figure, 28-day drying shrinkage was proportionally increased for increasing micro
fines content. As mentioned in Section 6.5.2.3, since drying shrinkage is directly
related to the amount of water used in the concrete batches, higher water demand
with higher micro fines content resulted in higher drying shrinkage. It should be
noted that some characteristics of MFA, that could improve the strengths, could
not improve the drying shrinkage. Hence, it is concluded that to reduce drying
shrinkage in MFA concrete, chemical or mineral admixtures should be used to
reduce the amount of water. An alternate is to use a chemical admixture which can
reduce drying shrinkage.
Table 6.14: Test Results of Drying Shrinkage and Chloride Ion Permeability
of Concrete for Different Micro Fines Content of Virginia Limestone
ID No.
Drying Shrinkage
at 28 days (%)
Chloride Ion Permeability
Adjusted Charge Passed
at 28days (Coulombs)
Natural Sand-V (3%) 0.009 4570
VA/LS/05-00/65-V (13%) 0.012 4100
VA/LS/05-00/65-V (17%) 0.014 4250
VA/LS/05-00/65-V (20%) 0.016 4880
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0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
28-dayDryingShrinkage(%)
Natural Sand 13% 17% 20%
Control vs Micro Fines Content of Virginia Limestone
Figure 6.16: Twenty-eight-day Concrete Drying Shrinkage
for Different Micro Fines Content of Virginia Limestone (Fixed Slump)
6.6.4.4Chloride Ion Permeability
The test results for chloride ion permeability for different micro fines
content of Virginia limestone are shown in Table 6.14 and Figure 6.17. As shown
in the figure, MFA concrete with 13 and 17 percent micro fines content showed
lower permeability than that of the control batch. For MFA concrete with 20
percent micro fines content the permeability was slightly larger than that of the
control batch. Similar to flexural strength, the permeability of MFA concrete with
higher content of micro fines can be improved regardless of fixed water-cement
ratio or fixed slump. As mentioned Section in 6.5.3.1, the penetrability of most
MFA concrete was high (above 4000 coulombs) regardless of the micro fines
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content. Hence, it is recommended that mineral admixtures be used to make less
permeable concrete.
3600
3800
4000
4200
4400
4600
4800
5000
28-dayAdjustedChargePassed
(Coulombs)
Natural Sand 13% 17% 20%
Control vs Micro Fines Content of Virginia Limes tone
Figure 6.17: Twenty-eight-day Concrete Chloride Ion Permeability
for Different Micro Fines Content of Virginia Limestone (Fixed Slump)
6.7 Summary
After performing screening and aggregate characterization tests and mortar
tests, various concrete tests were conducted to investigate the effect of MFA on the
properties of concrete. Fresh and hardened concrete tests as well as a case study to
investigate the effect of micro fines content on the properties of hardened concrete
were performed.
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A control batch using natural sand had high slump (7.5 inches) was
compared to that of the MFA batches for fixed water-cement ratio batches.
Sometimes low slump batches showed low Vebe times for a fixed water-cement
ratio. Even if a concrete batch showed low slump it could be a workable batch due
to short compacting time. It is concluded that the slump test is not adequate to
evaluate the workability of concrete batches. There was no significant temperature
change for fixed water-cement and fixed slump concrete batches. For either fixed
water-cement ratio or fixed slump, the unit weight of MFA batches was higher
than that of the control batch since micro fines filled the voids among aggregate
particles.
For fixed water-cement ratio most MFA concretes showed higher
compressive strengths than the control batch. On the other hand for fixed slump,
the compressive strength of the control batch was higher than for most MFA
concretes. If chemical admixtures are used to increase the workability for MFA
concrete, the compressive strength could be improved compared to that of natural
sand concrete. The flexural strengths of most MFA concretes were higher than for
the control batch for either fixed water-cement ratio or fixed slump. It is
concluded that the usual relationship between compressive and flexural strength
for natural sand concrete cannot be applied to MFA concrete since MFA improves
the flexural capacity regardless of a slump value. The drying shrinkage of most
MFA concretes were higher than that of the control batch for either fixed water-
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cement ratio or fixed slump. It is concluded that to reduce drying shrinkage in
MFA concrete, chemical admixtures should be used to reduce the amount of water.
For fixed water-cement ratio, all MFA concretes showed less 28-day
permeability based on the rapid chloride permeability test than that of the control
batch. The permeability of most MFA concrete, however, was high (over 4000
coulombs) regardless of fixed water-cement ratio or fixed slump. It is
recommended that mineral admixtures (such as fly ash, silica fume, etc) be used to
reduce the chloride ion permeability. For fixed water-cement ratio, all MFA
concretes showed less 28-day abrasion loss than that of the control batch, due to
higher micro fines content and more angular particle shape than natural sand. It is
likely that if chemical admixtures are used to improve workability, abrasion loss of
MFA concrete can be improved compared to natural sand concrete. All MFA
concretes required more cycles to reach rating 5 (severe scaling) than those of the
control batch. The number of cycles, however, was smaller than the 50 cycles that
typical concrete requires. It is recommended that AEA (air entrainment agent) be
used to produce more than 4 percent entrained air content in the MFA concretes
which will provide improved scaling resistance.
For a case study using Virginia limestone, increasing the micro fines
content resulted in a slight decrease in the 28-day compressive strength. If the
MBV is low (less than 0.5) and chemical admixtures are used to improve
workability of concrete batch, it is possible that 20 percent of micro fines content
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can be used to make good quality concrete. All MFA concretes with 13, 17, and
20 percent micro fines contents showed higher flexural strengths than that of the
control batch. Increasing micro fines content resulted in the 28-day drying
shrinkage to be proportionally increased. MFA concrete with 13 and 17 percent
micro fines content showed lower permeability than that of the control batch. For
MFA concrete with 20 percent micro fines content the permeability was slightly
higher than that of the control batch.
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CHAPTER SEVEN: CORRELATIONS OF TEST RESULTS
7.1 Introduction
Using test results (aggregate characterization, mortar, and concrete),
graphical and statistical analyses were performed to establish the relationship
among the test results and to make guidelines for using higher micro fines in
portland cement concrete. The following sections outline correlations of the test
results and correlated equations of test results using regression.
7.2 Correlations of Test Results
The correlations among test results (aggregate characterization, mortar, and
concrete) were analyzed using a SPSS statistical computer program. The
following sections outline the correlations of aggregate properties, the correlations
between aggregate and mortar properties, and the correlations between aggregate
and concrete properties.
7.2.1 Correlations of Aggregate Properties
The graphical and statistical analyses of aggregate properties are presented
in this section. A total of 112 sands for ICAR was used in the analyses. Vulcan
Materials Company and Svedala Barmac performed characterization tests on 204
sands from 29 locations. The analysis of this data can be found in Appendix E.
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7.2.1.1Statistical Analysis of Aggregate Properties
In a statistical analysis software (SPSS), Pearson correlation coefficients,
two-tailed significance level, and bivariate correlation were used.
Pearson correlation coefficients assume the data are normally distributed.
The Pearson correlation coefficient is a measure of linear association between two
variables. The values of the correlation coefficient range from 1 to 1. The sign
of the correlation coefficient indicates the direction of the relationship (positive or
negative). The absolute value of the correlation coefficient indicates the strength.
The values near 0 indicate a very weak linear relationship. The strength of the
relationship increases as the values move away from 0 toward either 1 or 1.
The significance level (or p-value) is the probability of obtaining results as
extreme as the one observed. If the significance level is very small (less than 0.05)
then the correlation is significant to 0.05 significance level and the two variables
are linearly related. On the other hand if the significance level is relatively large
(for instance, 0.50) then the correlation is not significant and the two variables are
not linearly related. However, even if the correlation between two variables is not
significant, the variables may be correlated but the relationship is not linear. Since
the Pearson correlation does not describe nonlinear relationships between
variables, no matter how strong they are.
The aggregate properties used in the analysis for all 112 sands were
crushing speed, bulk specific gravity at oven dry condition, absorption capacity,
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micro fines content, fineness modulus, and methylene blue value (MBV). The
voids content (ASTM C 1252, method A) was analyzed using only 63 of the sands.
The fineness modulus was calculated by a typical method that cumulative percent
retained samples on standard sieves between #100 through 3/8 inch are divided by
100. The correlations of aggregate properties are shown in Table 7.1.
Significant correlations at the 0.01 and 0.05 level are shown in bold with
two asterisks and one asterisk, respectively. As shown in the table, the following
correlations of aggregate properties were found (+ indicates increasing, -
indicates decreasing):
1) Crushing speed (+): absorption capacity (-), fines content (+), fineness
modulus (-), voids content (-)
2) Bulk specific gravity (+): voids content (+), MBV (-),
3) Absorption capacity (+): fines content (+), fineness modulus (+),
MBV(+)
4) Fines content (+): fineness modulus (-), MBV (+)
5) Fineness modulus (+): voids content (+), MBV (+)
and the two variables were linearly related.
It was noted that the Pearson correlation coefficients were relatively low
numbers ranging from 0.2 to 0.6. Since a total of 112 sands (7 different types of
rock) was used in the analyses, the deviation was high. Even if the Pearson
correlation coefficients were relatively low numbers, they were accepted since the
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Table 7.1: Correlations of Aggregate Properties
N = 112, * Correlation is significant at the 0.05 level (2-tailed), ** Correlation is significant at the
CrushingSpeed
BulkSpecificGravity(OD)
AbsorptionCapacity
FinesContent
FineneModulu
Crushing Speed Pearson Correlation 1.000 .052 -.213* ..447722**** --..555533**
Sig. (2-tailed) . .584 .025 .000 .000
Bulk Specific Gravity Pearson Correlation .052 1.000 -.176 .152 -.063
Sig. (2-tailed) .584 . .065 .110 .507
Absorption Capacity Pearson Correlation -.213* -.176 1.000 --..002200 ..443333***
Sig. (2-tailed) .025 .065 . .837 .000
Fines Content Pearson Correlation ..447722**** .152 --..002200 1.000 --..447733**
Sig. (2-tailed) .000 .110 .837 . .000
Fineness Modulus Pearson Correlation --..555533**** -.063 ..443333**** --..447733**** 1.000
Sig. (2-tailed) .000 .507 .000 .000 .
Voids Content Pearson Correlation --..557711**** ..554422**** .012 -.134 ..226622**
Sig. (2-tailed) .000 .000 .926 .295 .038
MBV Pearson Correlation -.091 --..330055**** .469** .212* .234*
Sig. (2-tailed) .341 .001 .000 .025 .013
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objective of the statistical analysis was to investigate the general trend of
correlations of aggregate properties instead of correlations of aggregate properties
for different types of rock.
7.2.1.2Chemical Composition versus Methylene Blue Value
A statistical analysis between chemical composition and methylene blue
value was performed on selected samples to investigate the correlation of the two
variables. As mentioned in Section 4.4.7, there were two series of chemical
analyses in this study. Series 1 used the selected aggregate samples with micro
fines directly delivered from the quarry, and Series 2 used material obtained from
crushing sizes larger than 4.75mm (0.187 in.). In the analysis, the chemical
composition of Series 1 was used since the methylene blue test was performed
using micro fines instead of the material larger than 4.75mm (0.187 in.). The
correlations between chemical composition and methylene blue value are shown in
Table 7.2. As shown in the table, there is no significant correlation observed based
on a 0.05 significance level and, hence, the two variables were not linearly related.
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Table 7.2: Correlations between Chemical Composition of Series 1 and MBV
MBV
CaO Pearson Correlation .317
Sig. (2-tailed) .405
MgO Pearson Correlation -.305
Sig. (2-tailed) .425
Fe2O3 Pearson Correlation .139
Sig. (2-tailed) .721
Na2O Pearson Correlation .096
Sig. (2-tailed) .806
K2O Pearson Correlation .153
Sig. (2-tailed) .694
MnO Pearson Correlation .343
Sig. (2-tailed) .367
TiO2 Pearson Correlation .156
Sig. (2-tailed) .688
SiO2 Pearson Correlation -.198Sig. (2-tailed) .610
Al2O3 Pearson Correlation .183
Sig. (2-tailed) .637
Ignition Pearson Correlation .060
Sig. (2-tailed) .878
7.2.2 Correlations between Aggregate and Mortar Properties
The statistical analyses of correlations between aggregate and mortar
properties are presented in this section. A total of 50 sands (300 batches) was used
in the analyses. The aggregate properties used in the analysis were crushing speed,
bulk specific gravity at oven dry condition, absorption capacity, voids content
(ASTM C 1252, method A), micro fines content, fineness modulus and modified
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methylene blue value (MMBV). The modified methylene blue value represents
the methylene blue value multiplied by micro fines content (%). Since mortar and
concrete specimens were made using whole samples including all micro fines
instead of a part of sample (20g of micro fines) that was used in the methylene
blue test, the methylene blue value should be multiplied by the micro fines content
to compensate the MBV for the extra micro fines. The mortar properties used in
the analysis were flow for fixed water-cement ratio, water-cement ratio for fixed
flow, 28-day compressive strength for fixed water-cement ratio and fixed flow,
and 28-day drying shrinkage for fixed water-cement ratio and fixed flow.
The correlations between aggregate and mortar properties are shown in
Table 7.3. In the table, the average values of the compressive strength and drying
shrinkage of three batches (LF, MF, HF or LV, MV, HV) were used. Crushing
speed and fineness modulus were omitted since there is no significant correlation
between them and the other mortar properties.
As shown in the table, the following correlations between aggregate and
mortar properties were found (+ indicates increasing, - indicates decreasing):
1) Bulk specific gravity (+): 28-day compressive strength for fixed water-
cement ratio (+)
2) Absorption capacity (+): 28-day compressive strength for fixed flow(-),
28-day drying shrinkage (+)
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Table 7.3: Correlations between Aggregate and Mortar Properties
Flow
forFixed
W/C
W/C
forFixed
Flow
28-day
CompressiveStrength for
Fixed W/C
28-day
CompressiveStrength for
Fixed Flow
28
DShrin
Fixe
Bulk Specific Gravity Pearson Correlation -.067 -.039 ..229922** .183 -
Sig. (2-tailed) .643 .788 .040 .203 .
Absorption Capacity Pearson Correlation .083 .046 --..115555 --..331111** ..55
Sig. (2-tailed) .566 .753 .283 .028 .
Fines Content Pearson Correlation --..664400**** --..551144**** -.185 --..338866**** ..
Sig. (2-tailed) .000 .000 .198 .006 .
Voids Content Pearson Correlation --..440022** ..337733** .041 -.357 .
Sig. (2-tailed) .030 .046 .831 .057 .
MMBV Pearson Correlation --..554455**** ..777722**** --..334422** --..772299**** ..88Sig. (2-tailed) .000 .000 .015 .000 .
Flow for Fixed W/C Pearson Correlation 1.000 --..990088**** ..443300**** ..777711**** --..44
Sig. (2-tailed) . .000 .002 .000 .
Water-Cement Ratio Pearson Correlation --..990088**** 1.000 --..445522**** --..885522**** ..66
for Fixed Flow Sig. (2-tailed) .000 . .001 .000 .
28-day Compressive Strength Pearson Correlation ..443300**** --..445522**** 1.000 ..773344**** --
for Fixed W/C Sig. (2-tailed) .002 .001 . .000 .
28-day Compressive Strength Pearson Correlation ..777711**** --..885522**** ..773344**** 1.000 --..66
for Fixed Flow Sig. (2-tailed) .000 .000 .000 . .
28-day Drying Shrinkage Pearson Correlation --..447744**** ..666633**** --..226611 --..664444**** 1
for Fixed W/C Sig. (2-tailed) .001 .000 .067 .000 28-day Drying Shrinkage Pearson Correlation --..557799**** ..777711**** --..332288** --..772266**** ..99
for Fixed Flow Sig. (2-tailed) .000 .000 .001 .000 .
N = 50, * Correlation is significant at the 0.05 level (2-tailed), ** Correlation is significant at th
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3) Fines content (+): Flow for fixed w/c ratio (-), w/c ratio for fixed flow
(-), 28-day compressive strength for fixed flow (-),
28-day drying shrinkage for fixed flow (+)
4) Voids content (+): flow for fixed water-cement ratio (-), water-cement
ratio for fixed flow (+)
5) Modified MBV (+): flow for fixed w/c ratio (-), w/c ratio for fixed flow
(+), 28-day compressive strength (-), 28-day drying
shrinkage (+)
6) Flow for fixed water-cement ratio (+): water-cement ratio for fixed
flow (-), 28-day compressive strength (+), 28-day
drying shrinkage (-)
and the two variables were linearly related.
The fines content and modified methylene blue value (MMBV) had
significant linear correlations with most of mortar properties. The Pearson
correlation coefficients, however, were higher values for the correlation between
the modified methylene blue value and mortar properties than the correlation of
fines content. It indicates that the modified methylene blue value is more accurate
than fines content as the factor relating mortar properties. In other words, the
modified methylene blue value is a better predictor of mortar properties than the
micro fines content.
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7.2.3 Correlations between Aggregate and Concrete Properties
Using the concrete test results for 10 sands (20 batches), statistical analyses
of correlations between aggregate and concrete properties were performed. As for
the correlation between aggregate and mortar properties, the aggregate properties
used in the analysis were bulk specific gravity at oven dry condition, absorption
capacity, voids content (ASTM C 1252, method A), micro fines content, and
modified methylene blue value (MMBV). The concrete properties used in the
analysis were slump for fixed water-cement ratio, water-cement ratio for fixed
slump, Vebe time, unit weight, air content, 28-day compressive strengths, 7-day
flexural strengths, and 28-day drying shrinkages.
The correlations between aggregate and concrete properties for fixed
water-cement ratio are shown in Table 7.4. Crushing speed and fineness modulus
were omitted since there is no correlation between them and the other concrete
properties. As shown in the table, the following correlations between aggregate
and concrete properties for fixed water-cement ratio were found (+ indicates
increasing, - indicates decreasing):
1) Bulk specific gravity (+): unit weight for fixed water-cement ratio (+)
2) Absorption capacity (+): 28-day drying shrinkages for fixed water-
cement ratio (+)
3) Voids content (+): unit weight for fixed water-cement ratio (-)
and the variables were linearly related.
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Table 7.4: Correlations between Aggregate and Concrete Properties (Fixed W
Slump VebeTime UnitWeight AirContent CompressiveStrength
Bulk Specific Gravity Pearson Correlation -.247 .532 ..993377**** -.329 .061
Sig. (2-tailed) .492 .113 .000 .354 .867
Absorption % Pearson Correlation .555 -.365 -.487 .308 -.406
Sig. (2-tailed) .096 .300 .154 .386 .244
Fines Content Pearson Correlation -.038 -.624 -.352 -.058 -.513
Sig. (2-tailed) .916 .054 .318 .873 .129
Voids Content Pearson Correlation -.486 .619 ..664433** .028 .054
Sig. (2-tailed) .154 .056 .045 .938 .883
MMBV Pearson Correlation -.209 -.141 -.177 .005 -.117
Sig. (2-tailed) .562 .698 .624 .990 .748
Slump Pearson Correlation 1.000 -.529 -.184 .213 -.061
Sig. (2-tailed) . .116 .611 .554 .867
Vebe Time Pearson Correlation -.529 1.000 .493 .112 .273
Sig. (2-tailed) .116 . .147 .757 .445
Unit Weight Pearson Correlation -.184 .493 1.000 -.498 -.154
Sig. (2-tailed) .611 .147 . .143 .671
Air Content Pearson Correlation .213 .112 -.498 1.000 .414
Sig. (2-tailed) .554 .757 .143 . .234
Compressive Strength Pearson Correlation -.061 .273 -.154 .414 1.000
Sig. (2-tailed) .867 .445 .671 .234 .
Flexural Strength Pearson Correlation .186 .311 .078 .032 .588
Sig. (2-tailed) .608 .381 .831 .931 .074
Drying Shrinkage Pearson Correlation .318 -.425 -.502 .267 -.155
Sig. (2-tailed) .370 .220 .139 .456 .669
N = 10, * Correlation is significant at the 0.05 level (2-tailed), ** Correlation is significant at the 0.01 le
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Since the samples that had high mortar cube compressive strengths as well
as high micro fines content were selected for concrete tests, the correlations
between compressive strength versus fines content as well as modified methylene
blue value were relatively weak. However, they had significant linear correlations
with flexural strength and drying shrinkage. For slump and Vebe time, there was
no correlation with other concrete properties.
The correlations between aggregate and concrete properties for fixed slump
are shown in Table 7.5. As shown in the table, the following correlations between
aggregate and concrete properties for fixed slump were found (+ indicates
increasing, - indicates decreasing):
1) Bulk specific gravity (+): unit weight for fixed slump (+)
2) Voids content (+): 7-day flexural strength for fixed slump (-)
3) Water-cement ratio (+): 7-day flexural strength for fixed slump (+)
and the variables were linearly related.
Comparing the factors of fines content and modified methylene blue value
(MMBV), there was no correlation between fines content and any concrete
properties for fixed slump. On the other hand the modified methylene blue value
had significant linear correlations with water-cement ratio and 7-day flexural
strength for fixed slump. Hence, the modified methylene blue value has more
influence than fines content on mortar and concrete properties.
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Table 7.5: Correlations between Aggregate and Concrete Properties (Fixed Sl
W/C VebeTime UnitWeight AirContent CompressiveStrength
Bulk Specific Gravity Pearson Correlation .188 .401 ..882277**** -.224 -.334
Sig. (2-tailed) .604 .250 .003 .533 .346
Absorption % Pearson Correlation -.230 -.322 -.280 .087 .066
Sig. (2-tailed) .524 .364 .433 .811 .857
Fines Content Pearson Correlation .300 -.285 -.297 -.007 .456
Sig. (2-tailed) .400 .424 .405 .984 .185
Voids Content Pearson Correlation .553 .247 .401 .185 -.428
Sig. (2-tailed) .097 .491 .250 .610 .217
MMBV Pearson Correlation ..774444** .105 -.273 .216 .097
Sig. (2-tailed) .014 .773 .445 .549 .789
Water-Cement Ratio Pearson Correlation 1.000 .077 -.327 .363 -.221
Sig. (2-tailed) . .832 .356 .303 .539
Vebe Time Pearson Correlation .077 1.000 .406 -.406 .243
Sig. (2-tailed) .832 . .244 .245 .499
Unit Weight Pearson Correlation -.327 .406 1.000 -.610 -.102
Sig. (2-tailed) .356 .244 . .061 .779
Air Content Pearson Correlation .363 -.406 -.610 1.000 -.340
Sig. (2-tailed) .303 .245 .061 . .337
Compressive Strength Pearson Correlation -.221 .243 -.102 -.340 1.000
Sig. (2-tailed) .539 .499 .779 .337 .
Flexural Strength Pearson Correlation --..773300** -.003 .126 -.216 .103
Sig. (2-tailed) .016 .994 .729 .549 .778
Drying Shrinkage Pearson Correlation .417 -.295 -.466 .409 -.425
Sig. (2-tailed) .231 .408 .175 .240 .221
N = 10, * Correlation is significant at the 0.05 level (2-tailed), ** Correlation is significant at t
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7.3 Correlated Equations among Test Results using Regression
While the statistical analysis was performed to investigate the linear
correlation of variables, a least-squares regression analysis was performed to find
nonlinear correlated equations of variables.
Using the regression analysis, correlated equations among test results are
presented in this section. In the least-squares regression analysis, the square of
correlation, R2, is the fraction of the variation in the value of Y that is explained by
the least-squares regression of Y on X.
The correlated equations between aggregate and mortar as well as concrete
properties were investigated. Based on the statistical analysis in previous sections,
the factors that had significant correlations were used in the regression analysis.
7.3.1 Correlated Equations of Aggregate and Mortar Properties
Using the least-squares regression analysis, second order polynomial
equations were found. The aggregate properties used in the regression analysis
were modified methylene blue value (MMBV), micro fines content, and
absorption capacity that turned out to be the factors deciding mortar properties. A
total of 50 sands (16 different sources) was used in the analysis. The trend of the
correlation per each type of rock could be different from the general trend. The
mortar properties used in the analysis were 28-day compressive strengths for fixed
flow and 28-day drying shrinkages for fixed flow.
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7.3.1.1Compressive Strength
Figures 7.1 through 7.3 show the correlations of MMBV, fines content and
absorption capacity with 28-day compressive strength for fixed flow. As shown in
Figure 7.1, the 28-day mortar cube compressive strength decreased as the modified
methylene blue value increased. The equation relating modified methylene blue
value and 28-day mortar cube compressive strength is:
Y = 9505 4182 X + 692 X2 (7.1)
for which X is the modified methylene blue value and the value of R2 is 0.57.
y = 692.42x2
- 4181.8x + 9505.4
R2
= 0.5674
0
2000
4000
6000
8000
10000
12000
0 0.5 1 1.5 2
Modified MBV
CompressiveStrength(psi)
Figure 7.1: Correlation between Modified Methylene Blue Value and
28-day Mortar Cube Compressive Strength (Fixed Flow)
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As shown in Figure 7.2, the 28-day mortar cube compressive strength
slightly decreased as the micro fines content increased. The equation relating
micro fines content and 28-day mortar cube compressive strength is:
Y = 9746 - 109 X + 0.52 X2 (7.2)
for which X is the micro fines content and the value of R2 is 0.15.
y = 0.5197x2
- 108.57x + 9745.5
R2
= 0.1494
0
2000
4000
6000
8000
10000
12000
0 5 10 15 20 25 30
Micro Fines Content (%)
CompressiveStreng
th(psi)
Figure 7.2: Correlation between Micro Fines Content and
28-day Mortar Cube Compressive Strength (Fixed Flow)
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As shown in Figure 7.3, the 28-day mortar cube compressive strength
slightly decreased as absorption capacity increased. The equation relating
absorption capacity and 28-day mortar cube compressive strength is:
Y = 9021 704 X + 94 X2
(7.3)
for which X is the absorption capacity and the value of R2 is 0.10.
y = 93.553x2
- 704.49x + 9020.8
R2
= 0.0973
0
2000
4000
6000
8000
10000
12000
0 0.5 1 1.5 2 2.5 3
Absorption Capacity (%)
CompressiveStrength(
psi)
Figure 7.3: Correlation between Absorption Capacity and
28-day Mortar Cube Compressive Strength (Fixed Flow)
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7.3.1.2Drying Shrinkage
Figures 7.4 through 7.6 show the correlations of MMBV, fines content and
absorption capacity with 28-day mortar drying shrinkage for fixed flow. As shown
in Figure 7.4, the 28-day mortar drying shrinkage increased as the modified
methylene blue value increased. The equation relating modified methylene blue
value and 28-day mortar drying shrinkage is:
Y = 0.0704 + 0.0538 X 0.0017 X2 (7.4)
for which X is the modified methylene blue value and the value of R2 is 0.78.
y = -0.0017x2
+ 0.0538x + 0.0704
R2
= 0.779
0.0000
0.0200
0.0400
0.0600
0.0800
0.1000
0.1200
0.1400
0.1600
0.1800
0 0.5 1 1.5 2
Modified MBV
DryingShrinkage(%)
Figure 7.4: Correlation between Modified Methylene Blue Value and
28-day Mortar Drying Shrinkage (Fixed Flow)
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As shown in Figure 7.5, the 28-day mortar drying shrinkage slightly
increased as micro fines content increased. The equation relating micro fines
content and 28-day mortar drying shrinkage is:
Y = 0.06 + 0.003 X - 0.00008 X2 (7.5)
for which X is the micro fines content and the value of R2 is 0.12.
y = -8E-05x2
+ 0.003x + 0.0608
R2
= 0.1167
0.0000
0.0200
0.0400
0.0600
0.0800
0.1000
0.1200
0.1400
0.1600
0.1800
0 5 10 15 20 25 30
Micro Fines Content (%)
DryingShrin
kage(%)
Figure 7.5: Correlation between Micro Fines Content and
28-day Mortar Drying Shrinkage(Fixed Flow)
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As shown in Figure 7.6, the 28-day mortar drying shrinkage peaks at a
value of approximately 1.75% absorption capacity. The equation relating
absorption capacity and 28-day mortar drying shrinkage is:
Y = 0.066 + 0.036 X 0.0099 X2 (7.6)
for which X is the absorption capacity and the value of R2 is 0.29.
y = -0.0099x2
+ 0.0355x + 0.0659
R2
= 0.2903
0.0000
0.0200
0.0400
0.0600
0.0800
0.1000
0.1200
0.1400
0.1600
0.1800
0 0.5 1 1.5 2 2.5 3
Absorption Capacity (%)
DryingShrinka
ge(%)
Figure 7.6: Correlation between Absorption Capacity and
28-day Mortar Drying Shrinkage (Fixed Flow)
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7.3.2 Correlated Equations of Aggregate and Concrete Properties
The equations relating aggregate and concrete properties were found.
Since the samples that had high mortar cube compressive strengths as well as high
micro fines content were selected for concrete tests, the correlations between
concrete compressive strength and fines content as well as modified methylene
blue value were relatively weak. Hence, the equations relating 28-day concrete
drying shrinkage for fixed water-cement ratio and micro fines content as well as
modified methylene blue value were found. For fixed slump, the equations
relating 7-day concrete flexural strength and the modified methylene blue value
was found.
7.3.2.1Drying Shrinkage for Fixed Water-Cement Ratio
Figures 7.7 and 7.8 show the correlations of MMBV and fines content with
the 28-day concrete drying shrinkage for fixed water-cement ratio. As shown in
Figure 7.7, the 28-day concrete drying shrinkage for fixed w/c increased as the
modified methylene blue value increased. The equations relating modified
methylene blue value and the 28-day concrete drying shrinkage for fixed w/c is:
Y = 0.0093 + 0.03 X 0.03 X2 (7.7)
for which X is the modified methylene blue value and the value of R2 is 0.61.
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0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.006
0.008
0.010
0.012
0.014
0.016
0.018
0.020
0.022
R2= 0.61
Y = 0.0093+ 0.03 X - 0.03 X2
DryingShrinkage(%)
Modified MBV
Figure 7.7: Correlation between Modified Methylene Blue Value and
28-day Concrete Drying Shrinkage (Fixed W/C)
As shown in Figure 7.8, the 28-day concrete drying shrinkage for fixed w/c
increased as micro fines content increased. The equation relating micro fines
content and 28-day concrete drying shrinkage for fixed w/c is:
Y = 0.015 0.0017 X + 0.00012 X2
(7.8)
for which X is the micro fines content and the value of R2
is 0.56.
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0 2 4 6 8 10 12 14 16 18 20
0.006
0.008
0.010
0.012
0.014
0.016
0.018
0.020
0.022
0.024
R2 = 0.56
Y = 0.015 - 0.0017 X+ 0.00012 X2
Drying
Shrinkage(%)
Micro Fines Content (%)
Figure 7.8: Correlation between Micro Fines Content and
28-day Concrete Drying Shrinkage(Fixed W/C)
7.3.2.2Flexural Strength for Fixed Slump
Figure 7.9 shows the correlation of modified methylene blue value and 7-
day concrete flexural strength for fixed slump. As shown in the figure, the 7-day
concrete flexural strength for fixed slump decreased as the modified methylene
blue value increased. The equation relating modified methylene blue value and the
7-day concrete flexural strength for fixed slump is:
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Y = 720 263 X + 178 X2 (7.9)
for which X is the modified methylene blue value and the value of R2 is 0.49.
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
500
550
600
650
700
750
R2= 0.49
Y = 720 - 263 X+ 178 X2
Modified MBV
FlexuralStrength(psi)
3.5
4.0
4.5
5.0
MPa
Figure 7.9: Correlation between Modified Methylene Blue Value and
7-day Concrete Flexural Strength (Fixed Slump)
7.4 Correlations of Other Test Results
The results of a companion study performed by Vulcan Materials Company
were analyzed for correlations and regression. The analysis of this study can be
found in Appendix E.
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7.5 Summary
Using experimental data (aggregate characterization, mortar, and concrete),
graphical and statistical analyses were performed in order to establish the
relationship among the data and in making guidelines for using higher micro fines
in portland cement concrete.
The percentage of micro fines increases with increasing crushing speed.
The following correlations of aggregate properties were found (+ indicates
increasing, - indicates decreasing):
1) Crushing speed (+): absorption capacity (-), fines content (+), fineness
modulus (-), voids content (-)
2) Bulk specific gravity (+): voids content (+), MBV (-),
3) Absorption capacity (+): fines content (+), fineness modulus (+),
MBV(+)
4) Fines content (+): fineness modulus (-), MBV (+)
5) Fineness modulus (+): voids content (+), MBV (+)
There is no significant correlation between chemical composition and
methylene blue value based on a 0.05 significance level and, hence, the two
variables were not linearly related.
The following correlations between aggregate and mortar properties were
found (+ indicates increasing, - indicates decreasing):
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1) Bulk specific gravity (+): 28-day compressive strength for fixed water-
cement ratio (+)
2) Absorption capacity (+): 28-day compressive strength for fixed flow(-),
28-day drying shrinkage (+)
3) Fines content (+): Flow for fixed w/c ratio (-), w/c ratio for fixed flow
(-), 28-day compressive strength for fixed flow (-), 28-day drying
shrinkage for fixed flow (+)
4) Voids content (+): flow for fixed water-cement ratio (-), water-cement
ratio for fixed flow (+)
5) Modified MBV (+): flow for fixed w/c ratio (-), w/c ratio for fixed flow
(+), 28-day compressive strength (-), 28-day drying
shrinkage (+)
6) Flow for fixed water-cement ratio (+): water-cement ratio for fixed
flow (-), 28-day compressive strength (+), 28-day
drying shrinkage (-)
The following correlations between aggregate and concrete properties for
fixed water-cement ratio were found (+ indicates increasing, - indicates
decreasing):
1) Bulk specific gravity (+): unit weight for fixed water-cement ratio (+)
2) Absorption capacity (+): 28-day drying shrinkages for fixed water-
cement ratio (+)
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3) Voids content (+): unit weight for fixed water-cement ratio (-)
The following correlations between aggregate and concrete properties for
fixed slump were found (+ indicates increasing, - indicates decreasing):
1) Bulk specific gravity (+): unit weight for fixed slump (+)
2) Voids content (+): 7-day flexural strength for fixed slump (-)
3) Water-cement ratio (+): 7-day flexural strength for fixed slump (+)
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CHAPTER EIGHT: GUIDELINES FOR USING HIGHER MICRO FINES
IN PORTLAND CEMENT CONCRETE
8.1 IntroductionBased on experimental data and graphical and statistical analyses using the
data, guidelines for using higher micro fines in portland cement concrete are
proposed. The following sections outline guidelines for mixture proportioning for
using higher micro fines in portland cement concrete, the classification of
manufactured fine aggregate based on their suitability for use and cost analysis.
8.2 Guidelines for Using Higher Micro Fines in Portland Cement ConcreteSeveral guidelines for incorporating the use of higher levels of micro fines
in concrete construction are presented.
8.2.1 Guidelines for Mixture Proportioning for Using Higher Micro Fines inPortland Cement Concrete
The test results indicated that good quality concrete could be produced
using many of the fine aggregates in the study at micro fine levels of up to 18
percent. As shown in Section 6.5.2.1, for a fixed water-cement ratio most MFA
concretes showed higher compressive strengths at 7 and 28 days than the control
batch. This indicates that if chemical admixtures are used to increase the
workability of the MFA concretes, up to 18 percent of micro fines can likely be
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used regardless of the modified methylene blue value. However, a maximum
amount of chemical admixtures should be determined by quality control testing to
prevent adverse effects on the properties of concrete. The amount of chemical
admixture will likely depend, in part, on the properties of manufactured fine
aggregate (e.g. grading, particle shape, particle texture, etc). Hence, based on the
properties of manufactured fine aggregate and chemical admixtures, the amount of
micro fines for each type of sand that can be used in portland cement concrete
should be determined.
The concrete specimens were made from fine aggregate, which had
produced high mortar strengths and had high micro fines contents. As a result the
concrete compressive strength had a weak correlation with the micro fines content
and with the modified methylene blue values (MMBV). From the mortar tests, it
is clear that there is a reduction in strength with increasing MMBV. The reason
for the higher levels of MMBV in some aggregates is not yet known. Concrete
specimens exhibited higher shrinkage with increasing MMBV. As a result,
caution is recommended when using fine aggregate with high MMBV to produce
concrete.
For the mixture proportioning of MFA concretes, a volumetric method is
recommended since the gradations of MFA do not meet ASTM C 33. The
sequence of mixture proportioning is the selection of water-cement ratio, the
minimum amount of cement, and determination of the amount of coarse and fine
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aggregates by volume based on voids among the particles. An improved
proportion method based on aggregate shape and texture as well as grading must
be developed in order to properly design concrete using high levels of micro fines.
8.2.2 Classification of Manufactured Fine Aggregate Based on TheirSuitability for Use
Concrete made with micro fines that result in adequate strength and
acceptable shrinkage may not have adequate slump for some applications. Slump
is not an adequate measure of workability for high fines concrete, but many
specifications continue to specify slump limits due to a lack of acceptable
measures of workability (TxDOT Specification, 1996).
Generally speaking, manufactured fine aggregate can be used in concrete
construction requiring low minimum slump. For structural concrete, it includes
slabs, concrete overlays, caps, columns, piers, and wall sections over 230 mm (9.1
inches). In addition the MFA can be used in concrete pavements. On the other
hand, MFA should be carefully used in concrete construction in which high
minimum slump is specified (e.g. drilled shafts and concrete placed underwater).
The suitability for use of MFA in concrete construction requiring high minimum
slump should be investigated in future research.
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8.3 Cost AnalysisThe relative cost of concrete made higher micro fines contents as compared
to concrete using current limits of micro fines will vary depending on many
factors. Total plant, delivery, sales, and general and administrative expenses will
likely be the same for both. For material costs, the concrete with higher micro
fines will require more chemical admixtures and coarse aggregate costs but less
cement and fine aggregate costs [Hudson, personal communication]. Since there
will be a high amount of micro fines in the concrete, more coarse aggregates and
less cement can be used and more chemical admixtures will generally be required
to increase the workability. Hence, total material costs will probably be slightly
decreased compared to the costs of the concrete made with micro fines at current
ASTM C 33 limits.
Other effects on cost include savings in disposal and handling of excess
micro fines and will vary from producers to producers. The improvement in
concrete properties including higher flexural strengths, reduced permeability, and
greater abrasion resistance is not easy to quantify. The cost of concrete with high
micro fines contents is most likely to be very competitive with conventional
concrete.
The National Ready Mixed Concrete Association (NRMCA) estimated that
372 million cubic yards of ready mixed concrete and 4.1 million cubic yards of
precast/prestressed used per year in the U.S. [NRMCA, 1998]. Even for 25
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percent of the annual construction concrete production, if an average of 1,100 lb.
of sand per cubic yard of concrete is used, an increase up to 18 percent from the
current 5 percent limit would result in the use of 4 million more tons of
manufactured fine aggregate each year. At $5.00 per ton this would return $20
million annually to aggregate producers and would eliminate disposing of the
fines.
Table 8.1 shows tonnage and savings of additional manufactured fine
aggregate used in annual concrete production if specifications are changed from
the present high of 5 percent to 10 percent replacement of sand, based on an
average of 1,100 lb. sand per cubic yard of concrete.
Table 8.1: Tonnage and Savings of Higher Amount of MFA Concretes
Ready-Mix Precast/Prestressed TotalsPercent Annual
Concrete
Production
Additional
Tons
Additional
Tons
Additional
Tons
Additional
Dollars
25% 3,973,750 43,606 4,017,356 20,086,781
50% 7,947,500 87,212 8,034,712 40,173,562
If higher amounts of micro fines are used in concrete construction, the
costs of concrete could be decreased as well as the cost savings due to use of
otherwise waste material may result in lots of savings and the improvement of
environmental condition.
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CHAPTER NINE: SUMMARY, CONCLUSIONS AND
RECOMMENDATIONS
9.1 SummaryThe increase in production of crushed aggregates has resulted in an
increase in manufactured fine aggregate (MFA). Standard specifications for fine
aggregate for concrete contained in ASTM C 33 permit a maximum of 7 percent
finer than the No. 200 sieve (75m), if the fines consist of dust-of-fracture
essentially free of clay or shale. Since the production process for MFA normally
generates 10 to 20 percent of micro fines, excess fines must be separated from the
desired sizes by screening or washing operations, or both. Previous studies
indicate an improvement in the properties of both fresh and hardened concrete
when the MFA included a higher percentage of micro fines than the 7 percent
ASTM C 33 limit.
The overall objective of this research study was to determine guidelines for
proportioning concrete with higher levels of crushed fines. Specially, the
objectives were to:
1) Develop a classification of crushed fines based on their suitability for use,2) Develop guidelines for mix proportioning of concrete higher fines contents,3) Determine the effect of higher amounts for several types of crusher fines
on concrete including fresh and hardened properties,
4) Develop modifications to existing construction specifications,
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5) Conduct a cost comparison between concrete containing fines at currentfines limits and concrete incorporating higher fines contents.
This research study consisted of four main stages. The first stage was the
selection of aggregates that were used in this project. Sixteen sources of
aggregates were used. The aggregate property-testing program was the second
stage. The basic aggregate characteristic tests were conducted to select the
aggregates that are proper to be tested for the next stage. Five tests were
performed for 112 sands and seven rock types. The third stage was the mortar
testing program to evaluate the use of MFA in mortar. Two variables (the cement-
sand ratio and the flow rate of mortar) were considered to investigate the
characteristics for each type of aggregate in mortar. The fourth stage was the