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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


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.


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.


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)


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)


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



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


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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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)



Figure 6.15: Seven-day Concrete Flexural Strength

for Different Micro Fines Content of Virginia Limestone (Fixed Slump)

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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(%)



Figure 6.16: Twenty-eight-day Concrete Drying Shrinkage


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)


Control vs Micro Fines Content of Virginia Limes tone

Figure 6.17: Twenty-eight-day Concrete Chloride Ion Permeability


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


Fe2O3 Pearson Correlation .139


Na2O Pearson Correlation .096


K2O Pearson Correlation .153


MnO Pearson Correlation .343


TiO2 Pearson Correlation .156


SiO2 Pearson Correlation -.198Sig. (2-tailed) .610

Al2O3 Pearson Correlation .183


Ignition Pearson Correlation .060


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


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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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


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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


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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)


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(%)


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


DryingShrin

kage(%)


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)


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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


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(%)



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)


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


3.5

4.0

4.5

5.0

MPa


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


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

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