“Old Wooden Bridge” Bridge to No Name Keyfrom Big Pine Key, Florida

Precision Statements for the Surface Resistivity of Water Cured Concrete

Cylinders in the Laboratory

by

Mike Jackson for

Mario Paredes

SponsorsAmerican Association of State Highway and Transportation Officials (AASHTO);

Technology Implementation Group (TIG);

Florida Department of Transportation;

TRB Committee AFN30 – Durability of Concrete.

Participants

California Department of Transportation;

Colorado Department of Transportation;

Federal Highway Administration;

Florida Department of Transportation;

Florida Atlantic University;

Grupo Carmelo, Puerto Rico;

Indiana Department of Transportation;

McGill University;

Participants (Continued)

Nebraska Department of Transportation;

New York Department of Transportation;

Puerto Rico Highways and Transportation Authority;

Purdue University;

Titan America –Tarmac;

The University of North Florida; and

Virginia Department of Transportation.

Round-Robin Testing Program

ASTM Designation C802, “Standard Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials.”

AASHTO Designation: TP95-11, “Standard Method of Test for Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration2.”

Round-Robin Testing Program

Fourteen (14) different laboratories;

Twelve (12) different concrete mixtures;

Wide range of constituent materials; and

Two (2) different commercial SR meters:• CNS Farnell Ltd.• Proceq SA.

Concrete Mix Constituents

# 1 400 200 200 1785 1209 275 800 25.0 25.0 0.34 0.68# 2 480 120 475 1439 1388 242 600 20.0 0.40 0.73# 3 660 200 1323 1220 335 860 23.3 0.39 0.92# 4 470 300 1585 1337 267 770 39.0 0.35 0.84# 5 519 173 1532 1482 277 692 25.0 0.40 0.97# 6 658 1800 1200 245 658 0.37 0.67# 7 500 135 41 897 890 1157 270 676 20.0 6.0 0.40 0.65# 8 423 141 935 2183 220 564 25.0 0.39 0.70# 9 490 110 25 1740 1175 255 625 17.6 4.0 0.41 0.68

# 10 500 258 75 1700 1076 254 833 31.0 9.0 0.30 0.63# 11 725 160 1741 972 265 885 18.1 0.30 0.56# 12 677 75 1701 1052 263 752 10.0 0.35 0.62

MICRON FLY ASH

(%)

META- KAOLIN

(%)

CA-1 (LB/CY)

CA-2 (LB/CY)

MIX NO.

CEMENT (LB/CY)

FLY ASH (LB/CY)

SLAG (LB/CY)

SILICA FUME

(LB/CY)

SILICA FUME

(%)

w/cm RATIO

FA/CA RATIO

MICRON FLY ASH (LB/CY)

FA (LB/CY)

WATER (LB/CY)

TOTAL CEMENTITIOUS

(LB/CY)

FLY ASH (%)

SLAG (%)

META- KAOLIN (LB/CY)

Concrete Mix Constituents

Mix w/cm ratios ranged from 0.30 - 0.41;

Ten of the12 mixes contained fly ash;

One mix contained no granular admixtures;

One mix contained 25% slag;

One mix contained 10% meta-kaolin; and

Two mixes contained 4% - 6% silica fume.

Test Samples

Hardened 4-in. diameter by 8-in. long cylindrical concrete specimens were tested;

Test specimens were fabricated by 12 of the participating labs, and shipped to all participants for SR testing;

SR was measured in accordance with AASHTO Designation: TP95-11 after 28, 56, and 91 days of standard laboratory curing.

Sample Packaging

After 2 weeks of curing in lime saturated water, specimens were wrapped and sealed to avoid loss of moisture during shipping.

Sample Shipping

The specimens were then carefully packaged for 2nd Day shipping to avoid damage and/or drying during shipping.

Surface Resistivity Testing

SR was then measured after 28, 56, and 91 days of standard laboratory curing.

8"

Top Bottom Probe Spacing

a =1.5"

4"

Wenner Array Probe

Resistivity Meter

KOhm - cm

Example SR Test Results

Surface Resistivity (SR) Readings (Kohm-cm)

Sample # 0° 90° 180° 270° 0° 90° 180° 270° Average

CTA-34 15.5 16 14.6 15.4 15.3 15.9 14.7 15.5 15.3625

CTA-36 15.3 16 14.7 15.2 15.3 15.6 14.6 15.1 15.2250

CTA-38 16.9 16.5 14.9 16.4 16.9 16.5 15.3 16.5 16.2375

Set Average 15.6083

Curing Condition Correction (x 1.1 lime tank or 1.0 for moist room) 1.1

Penetrability Based on Test 17.1692

Chloride Ion Penetration Type MODERATE

Air Temperature of testing room (°F) 67

Water Temperature of lime bath (°F) 72

Curing history specific to your lab once you received the specimens

 

Any abnormalities, comments, and/or notes. 

Mean SR at 28 Days

MIX 1 MIX 2 MIX 3 MIX 4 MIX 5 MIX 6 MIX 7 MIX 8 MIX 9 MIX 10 MIX 11 MIX 12# 1 11.254 9.088 8.996 12.925 9.463 9.646 25.246 27.817 17.183 22.392 11.917 31.567# 2 11.250 9.046 8.729 14.142 9.683 9.096 26.613 30.250 16.563 25.479 12.004 34.733# 3 11.238 9.026 8.275 13.954 8.888 9.598 26.658 27.096 15.814 32.013 12.223 33.060# 4 11.858 10.208 10.358 13.542 9.408 11.279 27.763 29.283 18.496 25.825 12.796 35.200# 5 12.367 15.854 10.421 15.371 9.383 10.588 30.288 31.483 17.242 30.938 12.233 0.000# 6 10.509 9.447 9.165 14.239 10.198 9.540 28.858 28.208 18.046 27.671 12.663 34.263# 7 14.792 12.792 12.458 16.917 13.042 13.333 32.833 33.875 19.504 28.154 14.379 37.421# 8 11.500 9.000 9.667 13.917 10.542 9.875 26.667 28.458 15.796 23.004 12.183 31.596# 9 11.188 9.763 9.133 13.917 9.433 9.742 28.363 28.808 16.854 24.092 12.567 30.917# 10 10.800 9.604 9.475 15.075 9.042 9.671 27.192 28.167 16.417 25.163 12.546 36.075# 11 0.000 9.733 11.063 14.721 9.733 10.033 26.900 26.900 15.933 0.000 11.167 28.283# 12 10.683 8.875 9.517 12.883 9.254 9.892 25.875 26.471 15.713 22.125 11.825 23.033# 13 0.000 10.042 10.785 14.166 9.836 11.611 27.629 35.071 18.200 19.104 11.388 33.525# 14 0.000 9.933 9.663 14.738 9.300 10.233 25.767 26.813 17.092 24.517 12.950 36.958

LAB No.Mean of 28-Day Surface Resistivity Readings (kOhm-cm)

Note: Data shaded in yellow determined to be statistical stragglers by Mandel’s k-statistic.

Std. Dev. at 28 Days

MIX 1 MIX 2 MIX 3 MIX 4 MIX 5 MIX 6 MIX 7 MIX 8 MIX 9 MIX 10 MIX 11 MIX 12# 1 0.49 0.39 0.18 0.88 0.17 0.27 1.58 1.99 0.72 0.12 0.23 4.27# 2 0.37 0.24 0.35 0.30 0.32 0.27 0.89 0.79 0.72 1.23 0.35 1.21# 3 0.43 0.31 0.24 0.52 0.23 0.41 1.87 1.48 0.35 1.48 0.46 3.00# 4 0.38 0.20 0.11 0.48 0.23 0.15 1.57 0.40 1.11 0.50 0.26 1.51# 5 0.45 0.72 0.72 0.14 0.40 0.34 1.64 1.63 0.65 0.29 0.07 0.00# 6 0.13 0.58 0.64 0.19 0.25 0.83 0.48 0.62 0.30 0.64 0.14 2.53# 7 0.29 0.36 0.69 0.31 0.56 0.88 1.23 0.76 0.38 0.79 0.43 2.87# 8 0.25 0.66 0.58 0.72 0.64 0.45 2.29 1.49 0.83 0.82 0.80 0.97# 9 0.15 0.14 0.24 0.86 0.50 0.08 1.19 1.09 0.43 1.36 0.21 1.67# 10 0.17 0.54 0.45 0.34 0.11 0.24 0.77 1.17 1.18 0.68 0.91 1.11# 11 0.00 0.38 0.59 1.02 0.38 0.59 1.23 0.74 0.41 0.00 0.22 1.63# 12 0.69 0.12 0.21 0.62 0.49 0.23 2.20 1.76 0.82 0.44 0.70 0.92# 13 0.00 0.22 0.21 0.70 0.16 0.32 1.45 2.12 0.97 0.59 0.48 0.75# 14 0.00 0.23 0.28 0.43 0.63 0.58 0.73 1.81 0.81 0.48 0.83 2.80

LAB No.Standard Deviation of 28-Day Surface Resistivity Readings (kOhm-cm)

Note: Data shaded in yellow determined to be statistical stragglers by Mandel’s k-statistic.

Mandel’s k-statistic at 28 Days

k = 2.044 at 1% significance

k = 1.698 at 5% significance

0.0

0.5

1.0

1.5

2.0

2.5

# 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 # 9 # 10 # 11 # 12 # 13 # 14

Man

del's

k

-Sta

tistic

Laboratory

MIX 1

MIX 2

MIX 3

MIX 4

MIX 5

MIX 6

MIX 7

MIX 8

MIX 9

MIX 10

MIX 11

MIX 12

Outliers

Stragglers

Mandel’s k-statistic at 56 Days

k = 2.044 at 1% significance

k = 1.698 at 5% significance

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

# 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 # 9 # 10 # 11 # 12 # 13 # 14

Man

del's

k

-Sta

tistic

Laboratory

MIX 1

MIX 2

MIX 3

MIX 4

MIX 5

MIX 6

MIX 7

MIX 8

MIX 9

MIX 10

MIX 11

MIX 12

Outliers

Stragglers

Mandel’s k-statistic at 91 Days

k = 2.044 at 1% significance

k = 1.698 at 5% significance

0.0

0.5

1.0

1.5

2.0

2.5

3.0

# 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 # 9 # 10 # 11 # 12 # 13 # 14

Man

del's

k

-Sta

tistic

Laboratory

MIX 1

MIX 2

MIX 3

MIX 4

MIX 5

MIX 6

MIX 7

MIX 8

MIX 9

MIX 10

MIX 11

MIX 12

Outliers

Stragglers

Mandel’s h-statistic at 28 Days

k = 2.298 at 1% significance

k = 1.850 at 5% significance

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

# 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 # 9 # 10 # 11 # 12 # 13 # 14

Man

del's

h

-Sta

tistic

Laboratory

MIX 1

MIX 2

MIX 3

MIX 4

MIX 5

MIX 6

MIX 7

MIX 8

MIX 9

MIX 10

MIX 11

MIX 12

Outliers

Stragglers

Mandel’s h-statistic at 56 Days

k = 2.298 at 1% significance

k = 1.850 at 5% significance

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

# 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 # 9 # 10 # 11 # 12 # 13 # 14

Man

del's

h

-Sta

tistic

Laboratory

MIX 1

MIX 2

MIX 3

MIX 4

MIX 5

MIX 6

MIX 7

MIX 8

MIX 9

MIX 10

MIX 11

MIX 12

Outliers

Stragglers

Mandel’s h-statistic at 91 Days

k = 2.298 at 1% significance

k = 1.850 at 5% significance

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

# 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 # 9 # 10 # 11 # 12 # 13 # 14

Man

del's

h

-Sta

tistic

Laboratory

MIX 1

MIX 2

MIX 3

MIX 4

MIX 5

MIX 6

MIX 7

MIX 8

MIX 9

MIX 10

MIX 11

MIX 12

Outliers

Stragglers

Precision Calculationsat 28 Days

MIX 1 MIX 2 MIX 3 MIX 4 MIX 5 MIX 6 MIX 7 MIX 8 MIX 9 MIX 10 MIX 11 MIX 12P 10 13 13 13 13 13 13 13 13 12 13 12m 11.265 9.971 9.634 14.122 9.551 10.062 27.217 28.833 16.873 25.193 12.189 32.434

s r2 0.151 0.169 0.174 0.375 0.149 0.174 2.187 2.015 0.584 0.686 0.265 4.521 0.61

s L2 0.256 3.265 0.617 0.428 0.155 0.450 1.169 4.876 0.711 13.128 0.193 13.124 2.10

s R2 0.407 3.434 0.790 0.803 0.304 0.624 3.356 6.891 1.295 13.814 0.458 17.646 2.71

s r 0.389 0.411 0.417 0.612 0.386 0.417 1.479 1.419 0.764 0.828 0.515 2.126 0.69

s R 0.638 1.853 0.889 0.896 0.551 0.790 1.832 2.625 1.138 3.717 0.677 4.201 1.36

COV (s r ) 3.45 4.13 4.33 4.33 4.04 4.15 5.43 4.92 4.53 3.29 4.22 6.56 4.28

COV (s R ) 5.66 18.59 9.23 6.35 5.77 7.85 6.73 9.10 6.74 14.75 5.55 12.95 8.52

s R /s r 1.64 4.50 2.13 1.46 1.43 1.89 1.24 1.85 1.49 4.49 1.31 1.98 2.06

r = 2.8s r 1.09 1.15 1.17 1.71 1.08 1.17 4.14 3.97 2.14 2.32 1.44 5.95 1.92

R = 2.8s R 1.79 5.19 2.49 2.51 1.54 2.21 5.13 7.35 3.19 10.41 1.89 11.76 3.81Outliers 1 1 1 1 1 1 1 1 1 1 1 1

Lab # #7 #7 #7 #7 #7 #7 #7 #7 #7 #7 #7 #7Type h h h h h h h h h h h h

Statistic28-Day Surface Resistivity (kOhm-cm)

Lab #7 Data

Removed

Pooled Precision

Values

Note: Lab #7 Data Removed Based on Mandel’s h-statistic.

Precision Estimatesat 28, 56, and 91 Days

Lab Cured Age

(Days)

Variance(Kohm-cm)2

Standard Deviation (Kohm-cm)

Precision (d2s) (Kohm-cm)

Repeatable, (within lab)

sr2

Reproducible(between lab)

sR2

Repeatable(within lab)

sr

Reproducible(between lab)

sR

Repeatable(within lab)

r

Reproducible(between lab)

R

28 0.61 2.71 0.69 1.36 1.92 3.81

56 1.63 12.9 1.09 2.97 3.05 8.33

91 3.64 33.1 1.55 4.24 4.34 11.9

Precision Statements

Lab Cured Concrete

Age

(Days)

COV (1s%) Precision (d2s%)Repeatability(within lab)

COV (sr)

(%)

Reproducibility(between lab)

COV (sR)

(%)

Repeatability(within lab)

r %

Reproducibility(between lab)

R %

28 4.28 8.52 12.1 24.1

56 4.14 11.5 11.7 32.5

91 4.29 11.0 12.1 31.1

Proposed Precision StatementsSingle-Operator Precision – The results of two properly conducted tests by the same operator on concrete samples from the same batch and of the same diameter should not differ by more than 12.1% of their average.

Multilaboratory Precision – The results of two properly conducted tests in different laboratories on the same material should not differ by more than 32.5% of their average.

Bias - This procedure has no measurable bias.

Equipment Equivalence

y = 1.01x - 1.37R² = 0.87

y = 0.99x - 1.83R² = 0.97

y = 1.02x - 4.12R² = 0.97Line of Equality

10

20

30

40

50

60

70

80

10 20 30 40 50 60 70 80

Proc

eq S

R M

eter

(kO

hm-c

m)

CNS SR Meter (kOhm-cm)

28 Days

56 Days

91 Days

Paper Published in the Journal of ASTM International, Paper ID #JAI104268-11, “Precision Statements for the Surface Resistivity of Water Cured Concrete Cylinders in the Laboratory.”