Mechanical Properties of Concrete with Flyash Obtained from Blended Coal Mixtures
Barzin. Mobasher and Sandeep A. Mane Department of Civil and Environmental Engineering
Raphaël Tixier
ACerS, PAC RIM 4, November 7, 2001 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
ASTM Fly ash classification Classification: ASTM
C 618 - 1998.
Class
F flyash: Bituminous coal. Class C flyash: Sub-bituminous coal
[SiO2+Al2O3+ Fe2O3], min, %
Class F 70
• Objectives of the present study: What are the properties of fly ash obtained from the combustion of blended coals (using subbituminous coal), but meeting the properties of class F flyash?
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Class C 50
Origin of coals for blended fuel Reference
Coal # 1
Coal # 2
A
50 % Lee Ranch
50 % PRB Eagle Butte
B
50 % Lee Ranch
50 % PRB North Antelope
C
40 % Lee Ranch
60 % PRB North Antelope
D
50 % Lee Ranch
50 % PRB Spring Creek
E
50 % McKinley
50 % PRB Spring Creek
F
75 % McKinley
25 % PRB Spring Creek
G and G2
Unit 1: 40 % Lee Ranch – 60 % Jacob Lake Unit 2: 30 % Spring Creek -30 % Jacob Lake-40 % Lee Ranch
H
50 % P & M
50 % PRB (Jacob’s Ranch)
I
Unit # 2 North and South Pipe
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Typical chemical composition Reference SiO2 Al2O3 Fe2O3 SiO2+ Al2O3+ Fe2O3 CaO MgO K2O Na2O SO3 LOI A
56
23
5
84
8.7
2.4
1.2
1.3
0.5 0.55
B
55
25
4
85
8.1
1.9
1.1
0.8
0.5 0.63
D
58
23
5
87
5.5
1.7
1.4
2.0
0.8 0.77
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Typical XRD pattern
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Mix Design of Concrete
Characteristic compressive strength ( f’c)= 5000 psi Water/Binder ratio = 0.4 Materials: a. Cement b. Aggregates (Coarse and Fine) c. Water d. Flyash, (meeting F class) Type of mix: a. Control mix b. 15% flyash c. 20% flyash d. 25% flyash e. 30% flyash Activators: NaOH, KOH, Ca(OH)2 Dosage : 1%, 2.5% and 4% of total binder. Chemical Admixture: superplasticizer. Curing: normal and limited number of autoclave curing
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Mix designs developed in ASU laboratory Mix ID #
% FA
Cement content Lbs/cu.yd
High cement Content
Low cement content
Dry weight of materials, kg
W/B Cement
Fly ash
Water
Sand
CA
H_40_LS
0
1129.9
0.4
8.68
-
3.47
7.5
9.86
H20_40_LS
20
941.15
0.4
7.23
1.45
3.47
7.5
9.86
H25_40_LS
25
903.4
0.4
6.94
1.74
3.47
7.5
9.86
H30_40_LS
30
868.25
0.4
6.67
2
3.47
7.5
9.86
L30_42_LS
30
493
0.42
4.83
1.45
2.64
12.47
16.41
L30_42_HS
30
493
0.42
4.83
1.45
2.64
12.47
16.41
L30_45_LS
30
490
0.45
4.8
1.44
2.81
12.29
16.17
L30_45_HS
30
490
0.45
4.8
1.44
2.81
12.29
16.17
L35_42_LS
35
480
0.42
4.5
1.63
2.64
12.47
16.41
Note: HS and LS refers to high and low superplasticizers HS: 400ml/100 kg of cementious materials. LS: 200ml/100 kg of cementious materials
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Types of Test and Specimen
Compression Test
Conventional Flexure Test
4 in. x 4 in. x 14 in. beam
Cyclic or Fracture Test
Concrete: 3 in. diameter, 6 in. cylinder Mortar: 2 in. cubes
3 in. x 1 in. x 13.5 in. Type A beam 4 in. x 4 in. x 14 in. Type B beam
Restrained Shrinkage specimen
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Compression Test
Closed-loop test to get the post peak response.
Control: Load and Circumferential displacement
Measurement: Load, Actuator reading, Circumferential and Axial displacement
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Effect of amount of flyash at 28 daysstress vs. circumferential strain 8000 7000
Stress, psi
6000 5000
y
Control 10% Flyash
x
25% Flyash 30% Flyash Weight of flyash
4000 3000 2000 1000 0 0.000
0.002 0.004 0.006 0.008 0.010 Circumferential strain, in/in
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0.012
Effect of amount of flyash at 28 daysstress vs. axial strain 8000 Control 20% Flyash 25% Flyash
6000 Stress, psi
30% Flyash Weight of flyash
4000
y y
2000
0 0.000
0.001
0.002 0.003 Axial strain, in/in
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0.004
Effect of activators on 30% flyash concrete at 7 days 6000 2.5% NaOH 2.5% KOH
5000
2.5% Lime
Dosage of activators
Stress, psi
4000 3000
y
2000 1000 0 0.000
x
0.004 0.008 0.012 Circumferential strain, in/in
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0.016
Effect of activators on 25% flyash concrete at 28 days 7000 No activators 1% NaOH
6000
2.5% NaOH
5000
2.5% KOH
Stress, psi
Dosage of activators
4000 3000
y
2000
x 1000 0 0.000
0.004 0.008 0.012 Circumferential strain, in/in
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0.016
Effect of Superplasticizers on 30% flyash concrete at 28 Days 5000 Age = 28 Days
Stress, Psi
4000
L30_42_LS L30_42_HS L30_45_LS L30_45_HS L35_42_LS
3000
2000
1000
0
0
0.002 0.004 0.006 0.008 Circumferential Strain, in/in
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0.01
Comparison of compressive test result for different volume of flyash and superplasticizer 20 28 Days 7 Days
18 16
H30_40_LS
Mix ID
14
H30_40_LS
12
TRM_SRP_30FA
10
L35_42_LS
8
L30_45_LS
6
L30_45_HS
4
L30_42_LS
2 0
L30_42_HS
0
1000 2000 3000 4000 5000 6000 7000 8000 Compressive Strength, Psi
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Effect of flyash levels and NaOH, KOH levels at 28 days 8000 No activators 1% NaOH
Compressive strength, psi
7000
2.5% NaOH 2.5% KOH Dosage of activators
6000
5000
4000
3000
0
5
10
15 20 % of flyash
25
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30
Comparison of flyash levels, curing conditions, and NaOH, and KOH levels for mortar cubes 7000 Average compressive strength, psi
6500
Autoclave curing
6000 28 Days
5500 5000 4500
Activators
4000
NaOH
3500
7 Days
3000
KOH NaOH
2500 2000
0
5
10 15 20 25 30 35 40 45 50 Weight of flyash, %
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Flexure Test • Closed-loop test to get the post peak response. • Measurement: Load, Actuator reading, CMOD and Displacement
• Control: Load and CMOD
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Effect of different flyash content on flexural strength 2000 Control 15% Flyash
1600
20% Flyash
Load, lbs.
25% Flyash
1200
30% Flyash
800 P
400
0 0.000 0.005 0.010 0.015 0.020 Crack Mouth Opening Displacement, inches
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Effect of activators on 30% flyash concrete No activators
2000
2.5% NaOH 2.5% KOH
Load, lbs.
1500
2.5% Lime
Dosage of activators
P
1000
500
0 0.000 0.004 0.008 0.012 0.016 Crack Mouth Opening Displacement, inches You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
Effect of Superplasticizers on flexural strength of concrete at 28 days. 1500
Age = 28 Days
Load, Lbs
1200
L30_42_LS L30_42_HS L30_45_LS L30_45_HS L35_42_LS
900
600
300
0
0
0.01
0.02 0.03 0.04 Deflection, in
0.05
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0.06
Effect of age and cement content on flexural strength of concrete 2100 H30_40_LS_28 Days H30_40_LS_7 Days L30_42_LS_28 Days L30_42_LS_7 Days
1800
Load, Lbs
1500 1200 900 600 300 0
0
0.01 0.02 0.03 0.04 0.05 Crack Mouth Openig Displacement,in
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0.06
Comparison with respect to weight of flyash and activator dose 2400 No activators 1% NaOH 2.5% NaOH
Flexural load, lbs.
2000
2.5% KOH
Dosage of activators
1600 P
1200
800
0
10
20 % of flyash
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30
Comparison of flexural strength for different volume of flyash and superplasticizer 20 28 Days 7 Days
18 16
H30_40_LS
14 Mix ID
H25_40_LS
12
TRM_SRP_30FA
10
L35_42_LS
8
L30_45_LS
6
L30_45_HS
4
L30_42_LS
2
L30_42_HS
0
0
500
1000 1500 Flexure Load, Lbs
2000
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Comparison of flexural toughness for different volume of flyash and superplasticizer 20 28 Days 7 Days
18 16
H30_40_LS
14 Mix ID
H25_40_LS
12
TRM_SRP_30FA
10
L35_42_LS
8
L30_45_LS
6
L30_45_HS
4
L30_42_LS
2 0
L30_42_HS
0
5
10 15 Toughness, Lbs.in
20
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25
Fracture toughness using Cyclic loadingunloading Tests 300 20% Flyash 30% Fly ash
LOAD, lbs.
200
100
0 0.000
0.002
0.004 0.006 0.008 Crack Mouth Opening Displacement, in
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0.010
0.012
Average toughness values, Type A specimen 2.50 2.5% Lime 2.5% KOH
2.00 Toughness, lbs/in
2.5% NaOH 1.50
1.00
0.50
0.00 0
5
10
15 20 25 Weight of flyash, %
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30
35
Average toughness values, Type B specimen 16
2.5% KOH 4% NaOH 2.5% NaOH
Toughness, lbs/in
12
2.5% Lime 2.5% KOH 2.5% NaOH
8
Control
4
0 0
5
10 15 20 25 Weight of flyash, %
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30
35
Field trial conducted in collaboration with ADOT to demonstrate performance of newly developed mix design of concrete with higher percentage of flyash by ASU
Test section of pavement along which samples were collected
Concrete pouring in test section of pavement
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Sample collection from pavement sections
-Tucson ready mix concrete with SRP 30% fly ash. (TRM_SRP_30FA) - Tucson ready mix concrete with 30% fly ash. (TRM_30FA) -Tucson Ready mix concrete with 20% fly ash. (TRM_20FA)
collection of test samples from pavement sections
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Effect of age on 30% flyash concrete for samples collected from field trial 4000 TRM_SRP_30FA
3500
7 Days 28 Days
Stress, psi
3000 2500
W/C = 0.4 FA = 30%
2000 1500 1000 500 0
0.002 0.0045 0.007 0.0095 Circumferential Strain, in/in
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0.012
Comparison of flexural strength for different volume of flyash in concrete samples collected from field trial 1200 TRM_20FA TRM_SRP_30FA
1000
Load, Lbs
800 Age = 28 Days W/C = 0.42
600 400 200 0
0
0.01
0.02 0.03 0.04 Deflection, in
0.05
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0.06
Compressive Strength as a function of age for Field Samples 6000 TRM_20FA TRM_SRP_30FA
Compressive Strength, Psi
TRM_30FA
5000
4000
3000
0
10
20
30 40 Age, Days
50
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60
Comparison of experimental and theoretical curve generated using R-curve program for 30% flyash concrete 1200 E = 14000 0.25 a0 = 12.75 mm b = 101.6mm t = 101.6 mm S = 406.4 mm KIC = 48.00 MPa*mm.5 CTODc = .05
Load, Lbs
900
% FA = 30
LSPC30_42_1 LSPC30_42_2 Model Fit
Age = 28 Days W/C = 0.42
600
300
0
0
0.005 0.01 0.015 0.02 0.025 Crack Mouth Opening Displacement,in
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0.03
Comparison of fracture resistance R for different superplasticizer content and w/c ratio generated using R-curve program 0.2 Age = 28 Days
Fracture Resistance, R
0.16 L30_42_LS
0.12
L30_45_LS
L35_42_LS L30_42_HS L30_45_HS TRM_SRP_30FA TRM_20FA
0.08
0.04
0
0
20
40 60 Crack Length, in
80
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100
Comparison of Stress Intensity factor obtained from Theoretical R-curve analysis for different mixes 8 KIC
28 Days
7
Mix ID
( FIELD )
6
TRM_SRP_30FA
5
L35_42_LS
4
L30_45_LS
3
L30_45_HS
2
L30_42_LS
1 0
L30_42_HS
0
10
20 30 40 50 Stress Intensity Factor, K
60
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70
Experimental setup of shrinkage test and recording of strain gage readings Concrete
Steel Tube
Strain gages
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Inspection of cracks using digital camera and microscope
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Comparison of experimental and theoretical curve of shrinkage test 300
Strain gage readings, microstrains
Control 25% Flyash Theoretical
200
Es = 2.9E7 psi C u = 0.235 sh = 540 microstrains
First crack
100
0
-100 0
3
5
8 10 Time, days
13
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15
18
Experimental result obtained from restrained shrinkage test of samples collected from the field 100 TRM_20FA TRM_SRP_30FA TRM_30FA
Micro Strains
80 60 40 20 0 -20
0
10
20 Age, Days
30
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40
Crack formation in shrinkage specimens collected from field during restrained shrinkage test
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Average crack width measured during restrained shrinkage test for samples collected from field 1.4 TRM_20FA TRM_30FA TRM_SRP_30FA
Avg. Crack width, mm
1.2 1 0.8 0.6 0.4 0.2 0
5
10
15
20 25 Age, Days
30
35
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40
Conclusions
Up to 30% of cement in cement based mixtures was replaced by blended coal flyash resulting in high strength and ductility. Even though addition of flyash with various chemical activators results in low early strength, it has higher strength than control concrete after the 28-days period Use of Sodium Hydroxide as an activator plays an important role in the hydration process and improves the compressive strength. Similar results were obtained in Autoclaved specimens. Concrete containing flyash also shows a significant increase in the flexural stiffness and ductility
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Conclusions (contd.)
The flexural properties of the Potassium hydroxide activated concrete are superior to the Sodium and Calcium hydroxide activators. Cyclic load-unload tests can be used to compute fracture properties of cement based materials.
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