Task Group on Mechanical Behavior of Cement

26th of June, 2013Washington DC

CHARGE

Develop a technical report on the characterization of mechanical behavior of cement and test methods to measure the mechanical parameters of cement in the laboratory.

New Orleans Winter MinutesThe meeting was called to order at 11:15 AM. A presentation highlighting the current status of the Task Group was reviewed. Discussion centered on the following: • There is no need to prescribe number of samples and analysis range for a technical report.• Using different control mechanisms for monotonic and cyclic tests is not required• Units of Measure should follow API guidelines• Dimensions of splitting tensile test specimen The next steps are:• Clean up draft procedures• Email to TG volunteers• Receive feedback by Summer meeting

The meeting was adjourned around 11:45 AM.

Status of Working Document

• Version 6– Formatted like other Technical Reports– All comments incorporated– Changed units to match API guidelines

• Quality control– Acoustic technique

• Other improvements

Next Steps

• Review and comment period– Comments due by Sept 1st.– Discuss around ATCE meeting? Sept 30th – Oct 4th

• Finalize document– Publications Committee

• Other needs?

Thank you

Cooperative Series #1• Plastic Standard– Load Frames: 6– Consistent E

• Avg: 0.565 Mpsi• COV: 4.6%

– Consistent ν• Avg: 0.35• COV: 5.5%• One outlier

– Acoustic: 3• 2 matched• E = 0.68 Mpsi• ν = 0.38

0.00% 0.05% 0.10% 0.15% 0.20% 0.25% 0.30% 0.35% 0.40%0

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400

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Strain

Stre

ss (P

si)

E=0.540 MpsiE=0.554 MpsiE=0.546 Mpsi

E=0.601 MpsiE=0.600 Mpsi

E=0.566 MpsiE=0.545 - 0.584 Mpsi

Cooperative Series #1• Neat H Cement– Load Frames: 4– Consistent E

• Avg: 2.06 Mpsi• COV: 5.3%• One outlier

– Consistent ν• Avg: 0.19• COV: 9.7%• One outlier

– Inconsistent Strength-0.10% 0.10% 0.30% 0.50% 0.70%0

500

1000

1500

2000

2500

3000

3500

4000

Strain

Stre

ss (p

si)

Cooperative Series #1• Neat H Cement– Splitting Tensile Strength: 4

• Avg: 677 psi• COV: 12.5%

– Acoustic• 2 Labs• 0.55 Mpsi and 3.20 Mpsi

Cooperative Series #1• 40 % Slag Blend – 3 Labs

• One outlier– Consistent E– Consistent ν– Inconsistent Strength– No Acoustic Data

CompositeModulus

(psi)Poisson's

RatioUltimate

Strength (psi)Tensile

Strength (psi)2.01E+06 0.19 9265 4652.20E+06 0.17 5410 3421.05E+06 0.14 6367 382

        

1.75E+06 0.17 7014 3966.15E+05 0.03 2007 63

35.1% 15.7% 28.6% 15.9%

Cooperative Series #1• Summary– Load frames are consistent– Need more data for acoustic– Instrumentation differences can influence stress-strain curve– Different loading applied

Cooperative Series #2

Slurry preparation

• Large scale blender– Lab 1, Lab 2, Lab 7

• Regular blender and low-shear mixer– Lab 3, Lab 5

• Regular blender and spatula mixing– Lab 4

• No information– Lab 6

Slurry density measured by Lab 3 using a Helium pycnometer is 13.99 lb/gal.

Specimen density (lb/gal) test results

Test No. Lab 1-I Lab 1-II Lab 4-I Lab 4-II Lab 3 Lab 5 Lab 7**

Mold Size 2’’ by 5’’ 2’’ by 5’’ 3” by 4”* 3” by 4”* 1.625’’ by 10’’ 1.5’’ by 3’’ 1.4’’ by 2.8’’ 2’’ by 2’’

Top 14.27 14.27 14.33 14.66 14.27 13.9 14.3 14.05

Middle14.29 14.28 14.41 14.41

14.28 13.9 14.34 14.0214.34 14.33 14.33 14.58

Bottom 14.53 14.45 14.41 14.41 14.3 14.0 14.32 13.99

Average 14.36 14.33 14.37 14.52 14.28 13.93 14.32 14.02

COV 0.008 0.006 0.003 0.009 0.001 0.004 0.001 0.002

*: Samples prepared by coring from a big specimen**: Sample position is not applicable here since a single mold is used for each sample (samples not cut).

Monotonic compression test(Lab 1-I)

-0.2% -0.1% 0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7%0

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Radial Strain Axial Strain

Stre

ss (p

si)

Stress-strain curves of three different tests indicate excellent repeatability.

Note: Strain is measured by attached extensometers.

0.0001 in./sec displacement control, 2’’ by 4’’ samples

Strain measurement by extensometers vs. by piston displacement (Lab 1-I)

0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% 0.8%0

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Axial Strain

Stre

ss (p

si)

Measured by Extensometers

Measured by piston displacement

Specimen deformation measured by piston displacement in the test frame tends to significantly overestimate the axial strain due to the fact that the test frame and the piston also deform during the test.

Both test methods can be used to check repeatability of test results.

-0.2% -0.1% 0.0% 0.1% 0.2% 0.3% 0.4% 0.5%0

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Radial Strain Axial Strain

Axia

l Str

ess (

psi)

Monotonic compression test(Lab 2)

Outliers ?

Variability in ultimate compressive strength.

Note: strain is measured by attached extensometers.

0.0001 in./sec displacement control, 2’’ by 4’’ samples

Monotonic compression test(Lab 3)

Loading rate seems to have some effect on test results.

Note: Strain is measured by piston displacement.

Displacement control, 1.6’’ by 3.2’’ samples

0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 1.2% 1.4%0

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400

600

800

1000

1200

1400

1600Displacement rate 0.000033 in./sec Displacement rate 0.00016 in./sec

Axial Strain

Axia

l Str

ess (

psi)

Monotonic compression test(Lab 4-I)

0 0.2 0.4 0.6 0.8 1 1.20

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400

600

800

1000

1200

1400

1600

1800Loading rate 35 psi/sec Loading rate 85 psi/sec

Strain, %

Axia

l str

ess (

psi)

Loading rate seems to have some effect on test results.

Note: strain is measured by measuring platen to platen displacement during compression.

Load control, 1’’ by 2’’ samples

Monotonic compression test(Lab 4-II)

0 0.2 0.4 0.6 0.8 1 1.20

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400

600

800

1000

1200

1400

1600

1800

2000Loading rate 35 psi/sec

Strain, %

Axia

l str

ess (

psi)

Loading rate seems to have some effect on test results.

Note: strain is measured by measuring platen to platen displacement during compression.

Load control, 1’’ by 2’’ samples

Gráfico Esfuerzo axial vs. Deformación axial, radial y volumétrica muestra API-1

0200400600800

10001200140016001800

-0.20% 0.00% 0.20% 0.40% 0.60% 0.80%

Deformación

Esfu

erzo

Axi

al,

sa (

psi)

Axial Radial Volumétrica

Monotonic compression test(Lab 6: representative test plot)

Note: Strain is measured by attached extensometers.

Control mode and loading rate not reported, 1.5’’ by 3’’ sample

Cyclic compression test(Lab 1)

• Cyclic– 50% of estimated strength (Avg of 3 monotonic test)– Minimum load during unloading was 100 lbf (32 psi).

• Lab 1-I– Load control during the entire loading process.– Test data are only partially obtained due to

instrumentation errors.• Lab 1-II

– Load control during the first cycle – Displacement control during the second half-cycle to

failure.

Effective loading rate of a typical displacement-controlled test (Lab 1-I)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-5

0

5

10

15

20

25

30

35

40

45

Normalized time to failure

Load

rate

(lb/

sec)

0.0001 in./sec displacement control, 2’’ by 4’’ samples

Effect of control mode on stress-strain curve (linear-elastic portion, Lab 1)

Control mode (and loading rate) seem to have very little effect on the stress-strain curve of the specimen in the linear-elastic range.

-0.03% 0.00% 0.03% 0.06% 0.09% 0.12%0

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Load control, 10 psi/sec Displacement control, 0.0001 in./minLoad control Displacement control

Radial Strain Axial Strain

Axia

l Str

ess (

psi)

Effect of control mode on measured mechanical properties (Lab 1)

Mechanical PropertiesCompressive

Strength(psi)

Young's modulus

(ksi)Poisson's

ratio

Displacement Control

Average 1687 728 0.207

Std. * 25 23 0.011

COV** 0.015 0.036 0.055

LoadControl

Average 1795 727*** 0.210***

Std. * 38 - -

COV** 0.021 - -

% Change in Average +6.4% -0.0% +1.0%

*: Standard Deviation**: Coefficient of Variation***: Only one valid test result was obtained

-0.1% 0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6%0

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Radial Strain Axial Strain

Axia

l Str

ess (

psi)

Cyclic compression test(Lab 1-II: representative test plot)

Note: Strain is measured by attached extensometers.

Loading rate and sample size are shown in the next two slides.

Cyclic compression test(Lab 1-II: first cycle of three samples)

-0.03% 0.00% 0.03% 0.06% 0.09% 0.12% 0.15%0

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400

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Radial Strain Axial Strain

Axia

l Str

ess (

psi)

Repeatability of the stress-strain curve of three different tests are acceptable.

31 lbf/sec (10 psi/sec) load control, 2’’ by 4’’ samples

Cyclic compression test(Lab 1-II: second half-cycle of three samples)

-0.2% -0.1% 0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7%0

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Radial Strain Axial Strain

Axia

l Str

ess (

psi)

Repeatability of the stress-strain curve of three different tests are acceptable.

0.0001 in./sec displacement control, 2’’ by 4’’ samples

Variations of measured elastic properties during cyclic loading (Lab 1)

Test No. Lab 1-II Lab 1-I

Specimen No. 1 2 3 4

Stress range for

calculation

Segment of loading

YM*

(ksi)PR**

YM*

(ksi)PR**

YM*

(ksi)PR**

YM*

(ksi)PR**

10%-50%

Load 703 0.178 664 0.180 665 0.186 709 0.205

Unload 725 0.184 693 0.185 696 0.190 773 0.205

Reload 709 0.179 681 0.176 685 0.180

Coefficient of variation 0.016 0.019 0.021 0.024 0.023 0.027

15%-40%

Load 723 0.179 677 0.180 678 0.185 727 0.210

Unload 716 0.187 679 0.183 683 0.188 771 0.226

Reload 716 0.179 683 0.176 689 0.181

Coefficient of variation 0.005 0.025 0.005 0.019 0.008 0.018*: Young’s Modulus**: Poisson’s Ratio

Cyclic compression test(Lab 4-I: representative test plot of first 3 cycles)

0.00% 0.02% 0.04% 0.06% 0.08% 0.10% 0.12% 0.14% 0.16%-100

0

100

200

300

400

500

600

700

800

Strain

Axia

l str

ess (

psi)

Note: strain is measured by measuring platen to platen displacement.

Young’s modulus and Poisson's ratio were calculated from test data of the 2nd and 3rd cycles.

0.05 mm/min (3.3 x 10-5 in./sec) displacement control, 1’’ by 2’’ samples

Cyclic compression test(Lab 7: representative test plot)

-1000 0 1000 2000 3000 4000 50000

200

400

600

800

1000

1200

1400

Radial Strain Axial Strain (µm/m)

STRE

SS (P

SI)

0.01 mm/min (6.6 x 10-6 in./sec) displacement control, 1.4’’ by 2.8’’ samples

Note: strain is measured by LVDT.

Young’s modulus and Poisson's ratio were calculated from test data of the 2nd half-cycle.

Comparisons of measured mechanical properties (uniaxial compression tests)

Test No.(No. of samples)

Lab 1-I(3)*

Lab 1-II(3)

Lab 2(5)**

Lab 3(2)

Lab 4-I(6)

Lab 4-II(6)

Lab 5(3)

Lab 6(3)

Lab 7(3)

UCS***(psi) 1687 1548 1318 1382 1673 1825 1246 1652 1201

Standard deviation(psi) 25 3 22 25 143 94 31 70 26

Young’s Modulus (ksi) 728 694 629 198 582 514 338 490 605

Standard deviation(ksi) 22 19 46 11 9 10 119 17 58

Poisson’s Ratio 0.208 0.182 0.168 - 0.14 0.13 0.06 0.183 0.155

Standard deviation 0.009 0.004 0.033 - 0.000 0.005 0.017 0.025 0.012

*: Samples tested with load control were not included in calculation.**: Previously identified potential outliers were not included in calculation.***: Uniaxial Compressive Strength, including samples tested cyclically.