“Old Wooden Bridge”
Bridge to No Name Key
from Big Pine Key, Florida
Precision Statements for the Surface
Resistivity of Water Cured Concrete
Cylinders in the Laboratory
by
Mike Jackson for
Mario Paredes
Sponsors
American 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
MICRON
SILICA METATOTAL
MICRON
SILICA METAMIX CEMENT FLY ASH
SLAG
CA-1 CA-2
FA WATER
FLY ASH
SLAG
FLY ASH
FUME KAOLIN
CEMENTITIOUS
FLY ASH
FUME KAOLIN
NO. (LB/CY) (LB/CY)
(LB/CY)
(LB/CY) (LB/CY) (LB/CY) (LB/CY)
(%)
(%)
(LB/CY)
(LB/CY) (LB/CY)
(LB/CY)
(%)
(%) (%)
# 1 400
200
200
1785
1209 275
800
25.0
25.0
# 2 480
120
475
1439 1388 242
600
20.0
# 3 660
200
1323
1220 335
860
23.3
# 4 470
300
1585
1337 267
770
39.0
# 5 519
173
1532
1482 277
692
25.0
# 6 658
1800
1200 245
658
# 7 500
135
41
897
890
1157 270
676
20.0
6.0
# 8 423
141
935
2183 220
564
25.0
# 9 490
110
25
1740
1175 255
625
17.6
4.0
# 10 500
258
75
1700
1076 254
833
31.0 9.0
# 11 725
160
1741
972
265
885
18.1
# 12 677
75
1701
1052 263
752
10.0
w/cm FA/CA
RATIO RATIO
0.34
0.40
0.39
0.35
0.40
0.37
0.40
0.39
0.41
0.30
0.30
0.35
0.68
0.73
0.92
0.84
0.97
0.67
0.65
0.70
0.68
0.63
0.56
0.62
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.
Wenner
Array
Probe
Resistivity Meter
KOhm - cm
Bottom
Probe Spacing
a =1.5"
8"
4"
Top
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
LAB No.
#1
#2
#3
#4
#5
#6
#7
#8
#9
# 10
# 11
# 12
# 13
# 14
MIX 1
11.254
11.250
11.238
11.858
12.367
10.509
14.792
11.500
11.188
10.800
0.000
10.683
0.000
0.000
MIX 2
9.088
9.046
9.026
10.208
15.854
9.447
12.792
9.000
9.763
9.604
9.733
8.875
10.042
9.933
MIX 3
8.996
8.729
8.275
10.358
10.421
9.165
12.458
9.667
9.133
9.475
11.063
9.517
10.785
9.663
Mean of 28-Day Surface Resistivity Readings (kOhm-cm)
MIX 4
MIX 5
MIX 6
MIX 7
MIX 8 MIX 9
12.925
9.463
9.646
25.246 27.817 17.183
14.142
9.683
9.096
26.613 30.250 16.563
13.954
8.888
9.598
26.658 27.096 15.814
13.542
9.408
11.279 27.763 29.283 18.496
15.371
9.383
10.588 30.288 31.483 17.242
14.239 10.198
9.540
28.858 28.208 18.046
16.917 13.042 13.333 32.833 33.875 19.504
13.917 10.542
9.875
26.667 28.458 15.796
13.917
9.433
9.742
28.363 28.808 16.854
15.075
9.042
9.671
27.192 28.167 16.417
14.721
9.733
10.033 26.900 26.900 15.933
12.883
9.254
9.892
25.875 26.471 15.713
14.166
9.836
11.611 27.629 35.071 18.200
14.738
9.300
10.233 25.767 26.813 17.092
MIX 10
22.392
25.479
32.013
25.825
30.938
27.671
28.154
23.004
24.092
25.163
0.000
22.125
19.104
24.517
MIX 11
11.917
12.004
12.223
12.796
12.233
12.663
14.379
12.183
12.567
12.546
11.167
11.825
11.388
12.950
MIX 12
31.567
34.733
33.060
35.200
0.000
34.263
37.421
31.596
30.917
36.075
28.283
23.033
33.525
36.958
Note: Data shaded in yellow determined to be statistical stragglers by
Mandel’s k-statistic.
Std. Dev. at 28 Days
LAB No.
#1
#2
#3
#4
#5
#6
#7
#8
#9
# 10
# 11
# 12
# 13
# 14
MIX 1
0.49
0.37
0.43
0.38
0.45
0.13
0.29
0.25
0.15
0.17
0.00
0.69
0.00
0.00
MIX 2
0.39
0.24
0.31
0.20
0.72
0.58
0.36
0.66
0.14
0.54
0.38
0.12
0.22
0.23
Standard Deviation of 28-Day Surface Resistivity Readings (kOhm-cm)
MIX 3
MIX 4
MIX 5
MIX 6
MIX 7
MIX 8 MIX 9 MIX 10
0.18
0.88
0.17
0.27
1.58
1.99
0.72
0.12
0.35
0.30
0.32
0.27
0.89
0.79
0.72
1.23
0.24
0.52
0.23
0.41
1.87
1.48
0.35
1.48
0.11
0.48
0.23
0.15
1.57
0.40
1.11
0.50
0.72
0.14
0.40
0.34
1.64
1.63
0.65
0.29
0.64
0.19
0.25
0.83
0.48
0.62
0.30
0.64
0.69
0.31
0.56
0.88
1.23
0.76
0.38
0.79
0.58
0.72
0.64
0.45
2.29
1.49
0.83
0.82
0.24
0.86
0.50
0.08
1.19
1.09
0.43
1.36
0.45
0.34
0.11
0.24
0.77
1.17
1.18
0.68
0.59
1.02
0.38
0.59
1.23
0.74
0.41
0.00
0.21
0.62
0.49
0.23
2.20
1.76
0.82
0.44
0.21
0.70
0.16
0.32
1.45
2.12
0.97
0.59
0.28
0.43
0.63
0.58
0.73
1.81
0.81
0.48
MIX 11
0.23
0.35
0.46
0.26
0.07
0.14
0.43
0.80
0.21
0.91
0.22
0.70
0.48
0.83
MIX 12
4.27
1.21
3.00
1.51
0.00
2.53
2.87
0.97
1.67
1.11
1.63
0.92
0.75
2.80
Note: Data shaded in yellow determined to be statistical stragglers by
Mandel’s k-statistic.
Mandel’s k-statistic at 28 Days
2.5
k = 2.044 at 1% significance
MIX 1
2.0
MIX 2
k = 1.698 at 5% significance
MIX 3
Mandel's k - Statistic
MIX 4
MIX 5
1.5
MIX 6
MIX 7
MIX 8
1.0
MIX 9
MIX 10
MIX 11
MIX 12
0.5
Outliers
Stragglers
0.0
#1
#2
#3
#4
#5
#6
#7
#8
Laboratory
#9
# 10
# 11
# 12
# 13
# 14
Mandel’s k-statistic at 56 Days
3.5
3.0
MIX 1
MIX 2
Mandel's k - Statistic
2.5
MIX 3
MIX 4
k = 2.044 at 1% significance
MIX 5
2.0
MIX 6
k = 1.698 at 5% significance
MIX 7
1.5
MIX 8
MIX 9
MIX 10
1.0
MIX 11
MIX 12
Outliers
0.5
Stragglers
0.0
#1
#2
#3
#4
#5
#6
#7
#8
Laboratory
#9
# 10
# 11
# 12
# 13
# 14
Mandel’s k-statistic at 91 Days
3.0
2.5
MIX 1
MIX 2
k = 2.044 at 1% significance
MIX 3
Mandel's k - Statistic
2.0
MIX 4
k = 1.698 at 5% significance
MIX 5
MIX 6
1.5
MIX 7
MIX 8
MIX 9
1.0
MIX 10
MIX 11
MIX 12
0.5
Outliers
Stragglers
0.0
#1
#2
#3
#4
#5
#6
#7
#8
Laboratory
#9
# 10
# 11
# 12
# 13
# 14
Mandel’s h-statistic at 28 Days
4.0
3.0
MIX 1
k = 2.298 at 1% significance
MIX 2
2.0
MIX 3
Mandel's h - Statistic
k = 1.850 at 5% significance
MIX 4
MIX 5
1.0
MIX 6
MIX 7
0.0
MIX 8
MIX 9
MIX 10
-1.0
MIX 11
MIX 12
Outliers
-2.0
Stragglers
-3.0
#1
#2
#3
#4
#5
#6
#7
#8
Laboratory
#9
# 10
# 11
# 12
# 13
# 14
Mandel’s h-statistic at 56 Days
4.0
3.0
MIX 1
k = 2.298 at 1% significance
MIX 2
2.0
MIX 3
Mandel's h - Statistic
k = 1.850 at 5% significance
MIX 4
MIX 5
1.0
MIX 6
MIX 7
0.0
MIX 8
MIX 9
MIX 10
-1.0
MIX 11
MIX 12
Outliers
-2.0
Stragglers
-3.0
#1
#2
#3
#4
#5
#6
#7
#8
Laboratory
#9
# 10
# 11
# 12
# 13
# 14
Mandel’s h-statistic at 91 Days
3.0
k = 2.298 at 1% significance
2.0
MIX 1
k = 1.850 at 5% significance
MIX 2
MIX 3
Mandel's h - Statistic
1.0
MIX 4
MIX 5
MIX 6
0.0
MIX 7
MIX 8
MIX 9
-1.0
MIX 10
MIX 11
MIX 12
-2.0
Outliers
Stragglers
-3.0
#1
#2
#3
#4
#5
#6
#7
#8
Laboratory
#9
# 10
# 11
# 12
# 13
# 14
Precision Calculations
at 28 Days
MIX 1
10
11.265
MIX 2
13
9.971
MIX 3
13
9.634
MIX 4
13
14.122
28-Day Surface Resistivity (kOhm-cm)
MIX 5 MIX 6 MIX 7
MIX 8 MIX 9
13
13
13
13
13
9.551 10.062 27.217 28.833 16.873
0.151
0.169
0.174
0.375
0.149
0.174
2.187
2.015
0.256
3.265
0.617
0.428
0.155
0.450
1.169
0.407
3.434
0.790
0.803
0.304
0.624
sr
0.389
0.411
0.417
0.612
0.386
sR
0.638
1.853
0.889
0.896
COV (s r )
3.45
4.13
4.33
COV (s R )
5.66
18.59
s R /s r
1.64
r = 2.8s r
R = 2.8s R
Statistic
P
m
sr
2
sL
2
sR
2
Outliers
Lab #
Type
MIX 10
12
25.193
MIX 11
13
12.189
MIX 12 Pooled
12
Precision
32.434 Values
0.584
0.686
0.265
4.521
0.61
4.876
0.711
13.128
0.193
13.124
2.10
3.356
6.891
1.295
13.814
0.458
17.646
2.71
0.417
1.479
1.419
0.764
0.828
0.515
2.126
0.69
0.551
0.790
1.832
2.625
1.138
3.717
0.677
4.201
1.36
4.33
4.04
4.15
5.43
4.92
4.53
3.29
4.22
6.56
4.28
9.23
6.35
5.77
7.85
6.73
9.10
6.74
14.75
5.55
12.95
8.52
4.50
2.13
1.46
1.43
1.89
1.24
1.85
1.49
4.49
1.31
1.98
2.06
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
1.79
1
#7
h
5.19
1
#7
h
2.49
1
#7
h
2.51
1
#7
h
1.54
1
#7
h
2.21
1
#7
h
5.13
1
#7
h
7.35
1
#7
h
3.19
1
#7
h
10.41
1
#7
h
1.89
1
#7
h
11.76
1
#7
h
3.81
Note: Lab #7 Data Removed Based on Mandel’s h-statistic.
Lab #7
Data
Removed
Precision Estimates
at 28, 56, and 91 Days
Lab Cured
Age
Variance
(Kohm-cm)2
Standard Deviation
(Kohm-cm)
Precision (d2s)
(Kohm-cm)
Repeatable,
(within lab)
Reproducible
(between lab)
Repeatable
(within lab)
Reproducible
(between lab)
Repeatable
(within lab)
Reproducible
(between lab)
sr 2
sR 2
sr
sR
r
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
(Days)
Precision Statements
Lab Cured
Concrete
Age
COV (1s%)
Precision (d2s%)
Repeatability
(within lab)
Reproducibility
(between lab)
Repeatability
(within lab)
Reproducibility
(between lab)
(Days)
COV (sr)
(%)
COV (sR)
(%)
r%
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 Statements
Single-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
Proceq SR Meter (kOhm-cm)
80
70
60
y = 1.02x - 4.12
R² = 0.97
Line of Equality
50
28 Days
40
y = 1.01x - 1.37
R² = 0.87
30
56 Days
y = 0.99x - 1.83
R² = 0.97
91 Days
20
10
10
20
30
40
50
CNS SR Meter (kOhm-cm)
60
70
80
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.”