Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 42
42
Table 19. Success rates for identifying the physical differences of the
HMA mixtures within a project.
NDT Device PSPA PQI GPR FWD
Success Rate, % 93 71 54 56
areas where the hypothesis was incorrectly rejected. Another modulus is used for all HMA layers. None of the NDT devices
difference that was found but not planned (so it was excluded accurately predicted the modulus values that were measured in
from Table 18) was the difference between the initial and the laboratory for the unbound materials and HMA mixtures
supplemental sections of the US-280 project (see Chapter 5 (see Figures 17-1 and 17-2). All of the modulus estimating
of NCHRP Web-Only Document 133). All NDT devices found NDT devices, however, did show a trend of increasing mod-
a significant difference between these two areas--the supple- uli with increasing laboratory measured moduli. The follow-
mental section had the higher dynamic modulus, which was ing subsections describe the use of adjustment factors for
confirmed with laboratory dynamic modulus tests. Both the confirming the assumptions used for structural design.
PSPA and FWD resulted in higher modulus values and the
GPR estimated lower air voids, but the PQI resulted in much 2.2.1 Unbound Layers
lower densities.
The PSPA did identify all but one of the areas with anom- It has been previously reported that layer moduli calculated
alies or differences. The non-nuclear density gauge did a rea- from deflection basins must be adjusted (multiplied) by a
sonable job, while the GPR and FWD only identified slightly factor for pavement structural design procedures that are
more than 50 percent of the areas with differences. The GPR, based on laboratory derived values at the same stress state
however, did measure the HMA lift thickness placed, which (AASHTO 1993; Von Quintus and Killingsworth 1998). In
was confirmed through field cores. Table 19 contains the suc- the 1993 AASHTO Pavement Design Manual, the adjustment
cess rates for identifying the physical differences of the HMA factor is referred to as the "C-factor," and the value recom-
mixtures within a project. mended for use is 0.33. Thus, there are differences between
The PSPA had an excellent success rate, while the PQI had the field and laboratory conditions that can cause significant
an acceptable rate. The GPR and FWD had lower rates that are bias when using NDT modulus values.
considered unacceptable. Some of the important differences Von Quintus and Killingsworth found that this adjustment
observed between the technologies and devices and the reasons factor was structure or layer dependent but not material type
for the lower success rates of the GPR and FWD are listed dependent. Adjustment factors were determined for different
as follows: types of structures. The C-factor found for embankment or
subgrade soils ranged from 0.35 to 0.75 and averaged 0.62 for
· The FWD is believed to have been influenced by the sup-
aggregate base materials. However, none of the deflection
porting layers creating noise and additional variability
basins measured in this study was measured on the surface
making it more difficult to identify the localized areas. In
of the unbound layers themselves. Conversely, all testing
addition, its loading plate probably bridged some of the
under this study was directly on the surface of the layer being
localized anomalies making it difficult to detect differences
evaluated.
near the surface of the layer evaluated (e.g., segregation).
To compensate for differences between the laboratory and
· The dielectric values measured by the GPR are minimally
field conditions, an adjustment procedure was used to estimate
affected by some of the properties that can change within
the laboratory resilient modulus from the different NDT
a project, and its success is heavily dependent on the num-
technologies for making relative comparisons. The adjustment
ber of cores taken for calibration purposes--similar to that
procedure assumes that the NDT response and modulus of
for unbound materials.
laboratory prepared test specimens are directly related and
In summary, the PSPA and non-nuclear density gauges proportional to changes in density and water content of the
(PQI) are considered acceptable in identifying localized dif- material. Figures 18, 19, and 20 compare the seismic (PSPA)
ferences in the physical condition of HMA mixtures. modulus measured on the samples used in preparing an M-D
relationship. The PSPA modulus-water content relationship
follows the M-D relationship. Thus, the assumption is believed
2.2 Estimating Target
to be valid.
Modulus Values
For simplicity, the adjustment factors were derived using
Laboratory measured modulus of a material is an input the same methodology within the FHWA-LTPP study, with
parameter for all layers in the MEPDG. Resilient modulus is the exception that a constant, low stress state was used to
the input for unbound layers and soils, while the dynamic determine the adjustment factor. In other words, the average
OCR for page 43
43
DSPA, Fine-Grained DSPA, Coarse-Grained Line of Equality
Geo., Fine-Grained Geo., Coarse-Grained
200
Elastic Modulus from NDT
150
Devices, ksi
100
50
0
0 10 20 30 40 50 60
Laboratory Resilient Modulus, ksi
(a) DSPA and the GeoGauge.
LWD, Fine-Grained LWD, Coarse-Grained DCP, Fine-Grained
DCP, Coarse-Grained Line of Equality
60
Elastic Modulus from NDT
50
Devices, ksi
40
30
20
10
0
0 10 20 30 40 50 60
Laboratory Resilient Modulus, ksi
(b) Deflection-Based and DCP methods.
Figure 17-1. Comparison of laboratory resilient modulus and
the elastic modulus values estimated with different NDT
technologies and devices.
Line of Equality FWD Modulus Line of Equality FWD Modulus
PSPA Modulus - Part A PSPA Modulus - Part B PSPA Modulus - Part A PSPA Modulus - Part B
NDT Estimated Modulus,
NDT Estimated Modulus,
2000 900
800
1500 700
600
ksi
ksi
1000 500
400
500 300
200
0 100
0 500 1000 1500 2000 100 200 300 400 500 600 700 800 900
Laboratory Measured Dynamic Modulus (In-Place Laboratory Measured Dynamic Modulus (In-Place
Temperature and 5 Hz.), ksi Temperature and 5 Hz.), ksi
(a) Entire data set. (b) Excludes data point for very stiff HMA mixture placed along SH-130.
Figure 17-2. Comparison of laboratory dynamic modulus and the elastic modulus values estimated with differ-
ent NDT technologies and devices.
OCR for page 44
44
Seismic Modulus, ksi Dry Density, pcfi
Poly. (Seismic Modulus, ksi) Poly. (Dry Density, pcfi)
116 90
114 80
Seismic Modulus, ksi
70
Dry Density, pcf
112
60
110
50
108
40
106 30
104 20
102 10
100 0
8.5 10 12 14.5 16 18 20
Moisture Content, I-85 Embankment, percent
Figure 18. Comparison of the PSPA modulus to the M-D relationship
for the I-85 low plasticity soil embankment.
Dry Density Seismic Modulus
Poly. (Seismic Modulus) Poly. (Dry Density)
128 100
90
Seismic Modulus, kis
126
80
Dry Density, pcf
124 70
122 60
50
120 40
118 30
20
116
10
114 0
7.5 8.5 9.6 10.5 12 13 14 15 16
Moisture Content, SH-130 Embankment, percent
Figure 19. Comparison of the PSPA modulus to the M-D relationship
for the SH-130 improved granular embankment.
Dry Density Seismic Modulus
Poly. (Seismic Modulus) Poly. (Dry Density)
131 140
130.5
Seismic Modulus, ksi
120
Dry Density, pcf
130 100
129.5
80
129
60
128.5
128 40
127.5 20
127 0
3.8 4.8 5.8 7 8 9 10
Moisture Content, US-280 Crushed Stone, percent
Figure 20. Comparison of the PSPA modulus to the M-D relationship
for the US-280 crushed stone base.
OCR for page 45
45
Table 20. Adjustment factors or ratios applied to the NDT modulus
values to represent laboratory conditions or values at low stress states;
Part A projects.
Percent of Ratio or Adjustment Factor
Percent
Project Material Optimum
Compaction Geo. DSPA DCP LWD
Moisture
I-85
Low Plasticity Clay 91 165 0.19 0.087 0.53 0.39
Embankment
TH-23 Silt-Sand-Gravel
100 132 0.90 0.41 0.95 3.13
Embankment Mix
SH-21
High Plasticity Clay 99 84 1.16 0.99 2.94 2.78
Subgrade
TH-23 Base Crushed Aggregate 104 55 0.71 0.30 0.68 1.69
SH-130 Improved Granular
105 101 1.39 1.04 1.67 1.43
Embankment Mix
US-280 Base Crushed Stone 101 52 1.01 0.24 0.96 1.04
The adjustment ratio or factor was determined by dividing the average resilient modulus measured in the
laboratory by the average modulus from the NDT device (for a specific stress state, see Table 21).
laboratory measured modulus (triplicate repeated load resilient oratory (see Tables 21 and 22) for the Part A field evaluation
modulus tests were performed) was divided by the average projects.
moduli estimated with each NDT device. The adjustment factors do not appear to be related to the
Table 20 contains the adjustment factors equating the percent compaction, percent of optimum water content, or
NDT moduli to the resilient modulus measured in the lab- material type. The adjustment factors for the deflection-based
Table 21. Average repeated load resilient modulus values measured
in the laboratory at a specific stress state.
Percent Laboratory
Project & Dry Moisture
Area Maximum Resilient
Materials Density, pcf Content, %
Density, % Modulus, ksi
Before IC Section 1,
I-85 Low 103.0 21.6 0.91 2.5
Rolling Lanes B,C,D
Plasticity Clay
After IC Section 1,
Embankment 108.0 16.9 0.96 4.0
Rolling Lanes B,C,D
NCAT; Oklahoma High Plasticity Clay 96.7 21.3 0.97 6.9
NCAT; South Carolina Crushed Granite Base 130.0 4.7 0.94 14.3
TH-23 South
Lanes A,B 121.0 8.2 0.98 16.0
Embankment, Section
Silt-Sand- North
Lane B,C 122.4 9.1 1.00 16.4
Gravel Mix Section
US-2 Embankment; Soil-Aggregate Mix 123.1 12.1 0.96 19.0
NCAT; Missouri Crushed Limestone Base 124.4 9.0 0.96 19.2
SH-21 High Area 1, with
Lanes A,B 107.3 18.4 0.99 26.8
Plasticity Clay IC rolling
TH-23 Crushed Middle Area Lane B 139.4 4.3 1.04 24.0
Aggregate Base South Area All Lanes 141.1 4.2 1.03 24.6
US-53 Crushed Aggregate Base, Type 304 136.0 9.1 1.01 27.5
NCAT; Florida Limerock Base 110.5 13.4 0.95 28.6
US-2 Class 5 Crushed Aggregate Base 134.4 5.9 0.95 32.4
SH-130
Improved Sections 2, 3 Lanes A,B 128.7 9.1 1.05 35.3
Granular
US-280
Areas 1,2,3 150.6 3.2 1.01 48.4
Crushed Stone
NOTES:
Resilient modulus values for the fine-grained soils and embankments are for a low confining pressure
(2 psi) and repeated stress of 4 psi, while a confining pressure of 6 psi and repeated stress of 6 psi was used
for the granular base materials. These low stress conditions are not based on any theoretical analysis. One
stress state for the embankment soils and one for aggregate base layers were selected for consistency in
comparing the field estimated elastic modulus values from each NDT device to values measured in the
laboratory, which were considered the target values.
Percent maximum density is based on the maximum dry unit weight or density from the moisture-density
relationship (the maximum dry densities are included in Table 23 for each material tested).
OCR for page 46
46
Table 22. Elastic modulus values estimated from the NDT technologies and
devices, without adjustments, in comparison to resilient modulus values
measured in the laboratory.
Project Material Area Modulus, ksi
Lab.* GeoGauge DSPA DCP LWD
I-85 Low Section 2, Lane A 2.2 10.6 24.1 5.0 ---
Embankment Plasticity Section 1, All Lanes 2.5 15.4 30.0 5.9 ---
Before IC Clay Section 2, Lanes B,
Rolling 2.5 17.0 36.6 5.2 ---
C, D
I-85 Low Section 1 4.0 16.8 30.4 6.9 9.99
Embankment Plasticity
After IC Clay Section 2 4.5 19.0 40.4 6.2 11.78
Rolling
So. Section, Lane C 15.0 13.2 31.1 11.5 5.6
TH-23 Silt-Sand- So. Sect., Lanes A,B 16.0 18.3 43.6 15.2 5.7
Embankment Gravel Mix No. Sect., Lanes B,C 16.4 17.8 35.7 19.0 4.7
No. Sect., Lane A 17.0 22.0 51.7 18.5 4.7
SH-21 High Plasticity No IC Rolling 22.0 19.6 23.6 11.9 ---
Subgrade Clay After IC Rolling 26.8 22.9 27.1 8.8 9.6
Middle Sect., Lane C 19.5 21.6 28.0 18.6 8.0
Crushed North Section, All
TH-23 Base Aggregate Lanes; Middle 24.6 28.2 79.3 33.1 12.3
Base Section Lanes A, B
South Section, Lanes
26.0 33.0 110.7 46.4 19.4
A, B
SH-130 Section 3 34.5 19.4 33.3 20.7 24.1
Improved Granular
Sections 1, 2 35.3 26.4 34.3 21.3 24.6
Embankment
US-280 Base Crushed Area 4 40.0 35.1 117.4 34.3 18.5
Stone Areas 1, 2, 3 48.4 47.9 198.6 50.3 46.5
NOTES:
* The repeated load resilient modulus values measured in the laboratory, but corrected to the actual dry density
and moisture content measured for the specific section, in accordance with the LTPP procedure and regression
equations.
devices are approximately the inverse of the values reported ues, with the exception of the fine-grained, clay soils. The
from the FHWA-LTPP study. Thus, the adjustment factors GeoGauge deviated significantly from the laboratory values
derived from testing on bound pavement surfaces should for the fine-grained soils. The results also show that both the
not be used when testing directly on the unbound layer being GeoGauge and DCP over- or under-predicted the laboratory
evaluated. measured values for the same material, with a few exceptions.
Another important observation from the Part A projects is These ratios were compared to the percent compaction, per-
that the adjustment factors for all NDT devices for the I-85 low cent of optimum water content, and material type, but no rela-
plasticity clay embankment prior to IC rolling are significantly tionship could be found. The GeoGauge and DSPA adjustment
lower than for any of the other materials. This observation sug- ratios appear to be related to the amount of fines in the mate-
gests that the resilient moduli measured in the laboratory are rial (percent passing number 200 sieve), as shown in Figure 21.
much lower than for any of the other soils and materials. The In summary, the GeoGauge can be used to estimate the
reason for the low values is unknown. This embankment soil resilient modulus measured in the laboratory for aggregate
had the lowest dry density and highest water content relative to base materials and coarse-graded soil-aggregate embankments,
its maximum dry density and optimum water content also see while the DCP provided a closer estimate for the fine-grained
Table 23). However, these data were excluded from developing soils. However, the ratios for both of these devices were
the adjustment factors and selection of an NDT device that can variable--even within the same soil or material group. The
be used to confirm the structural design parameters because DSPA resulted in a positive bias (over-predicted the laboratory
they were consistent across all NDT devices. resilient modulus) with variable ratios. It is suggested that
Table 24 contains the adjustment factors for all projects repeated load resilient modulus tests be performed to deter-
included in the field evaluation (Parts A and B). The LWD is mine the target or design value and that those results be used
not included in Table 24 because it was excluded from the to calibrate the NDT devices for a specific soil or aggregate
Part B projects. On average, the GeoGauge and DCP pro- base, because of the variability of these ratios. The resilient
vided a reasonable estimate to the laboratory measured val- modulus test should be performed on bulk material sampled
OCR for page 47
47
Table 23. Maximum dry density and optimum water content for the unbound
materials and soils, as compared to the average test results from the EDG.
Maximum Optimum Average
Average Dry
Project Material Dry Unit Water Water
Density, pcf
Weight, pcf Content, % Content, %
NCAT,
High Plasticity Clay 99.9 21.8 96.7 21.3
Oklahoma
SH-21,
High Plasticity Clay 108.0 21.9 107.3 18.4
TX
Low Plasticity Soil; Pre-IC 107.98 16.9
I-85, AL 112.7 13.1
Low Plasticity Soil; Post-IC 107.98 16.9
SH-130, Improved Granular
122.0 9 123.3 8.32
TX Embankment
Silt-Sand-Gravel Mix
122.77 8.69
TH-23, South Area
122.6 12
MN Silt-Sand-Gravel Mix
123.80 7.87
North Area
Soil-Aggregate,
US-2, ND 128.0 9.0 123.1 12.1
Embankment
NCAT,
Limerock Base 116.1 12.5 110.5 13.4
FL
CR-103 Caliche Base 127.5 10.0 125.0 9.5
NCAT,
Crushed Limestone 130.0 10.0 124.4 9.0
MO
TH-23,
Crushed Aggregate Base 135.3 7.8 129.82 4.3
MN
US-53,
Crushed Aggregate Base 134.1 8.5 136.0 9.1
OH
NCAT,
Crushed Granite Base 138.1 5.0 130.0 4.7
SC
US-2, ND Crushed Gravel Base 141.1 6.0 134.4 5.9
US-280,
Crushed Stone Base 148.5 6.2 147.58 3.9
AL
NOTE: The maximum dry density and optimum water content for most of the materials and layers were
determined using AASHTO T 180. The exception is the high plasticity clay from the Texas project and the
North Dakota embankment material.
from the stockpiles or the roadway during construction 1,2,3 = Principal stress, psi.
(control strips). k1,2,3 = Regression constants from laboratory resilient mod-
Most state agencies do not have a resilient modulus test- ulus test results.
ing capability, so other procedures will need to be used to
establish the design or target value during construction The k regression constants are material specific. The fol-
(Darter et al. 1997). The resilient modulus was calculated at lowing defines the regression constants for the different
the same stress state shown in Table 21 using the regression materials that were tested within the field evaluation proj-
equations that were developed from an FHWA-LTPP study ects. These relationships for these regression constants were
(Yau and Von Quintus). The following regression equations developed from the FHWA-LTPP study (Von Quintus and
were used: Killingsworth).
k k3
oct
2
Crushed Stone Base Materials
M R = k1 ( pa ) + 1 (1)
pa pa k1 = 0.7632 + 0.008 ( P3 8 ) + 0.0088(LL) - 0.037 ( w s )
Where: - 0.0001( dry ) (4)
= Bulk Stress, psi
= 1 + 2 + 3 (2) k2 = 2.2159 - 0.0016 ( P3 8 ) + 0.0008(LL) - 0.038 ( w s )
= Octahedral shear stress, psi
dry
2
- 0.0006 ( dry ) + 0.00000024 (5)
=
( ( 1 - 2 )2 + ( 2 - 3 )2 + ( 3 - 1 ) ) 2 0.5
(3)
P#40
3
pa = Atmospheric pressure, 14.7 psi k3 = -1.1720 - 0.0082(LL) - 0.0014 ( w s ) + 0.0005 dry (6)
OCR for page 48
48
Table 24. Adjustment factors applied to the NDT modulus values to
represent laboratory conditions or values at low stress states, all projects.
Adjustment Factors Relating
Resilient Modulus, ksi
Laboratory Values to NDT Values
Project Identification Laboratory Predicted
Measured with LTPP Geo Gauge DSPA DCP
Value Equations
Fine-Grained Clay Soils
I-85 Low- Before IC Rolling 2.5 10.5 0.154 .0751 0.446
Plastic Soil After IC Rolling 4.0 13.1 0.223 0.113 0.606
NCAT; OK High Plastic Clay 6.9 19.7 0.266 0.166 0.802
SH-21, TX High Plastic Clay 26.8 19.6 1.170 0.989 3.045
Average Ratios for Fine-Grained Soil 0.454 0.336 1.225
Embankment Materials; Soil-Aggregate Mixture
South Embankment 16.0 15.7 0.696 0.367 1.053
TH-23, MN
North Embankment 16.4 16.3 0.735 0.459 0.863
US-2, ND Embankment 19.0 19.5 1.450 0.574 0.856
SH-130, TX Improved Soil 35.3 21.9 1.337 1.029 1.657
Average Ratios for Soil-Aggregate Mixtures; Embankments 1.055 0.607 1.107
Aggregate Base Materials
Co. 103, TX Caliche Base --- 32.3 1.214 --- 1.436
NCAT, SC Crushed Granite 14.3 36.1 0.947 0.156 ---
NCAT, MO Crushed Limestone 19.2 40.9 0.747 0.198 ---
Crushed Stone, Middle 24.0 29.9 0.851 0.303 0.725
TH-23, MN
Crushed Stone, South 26.0 35.6 0.788 0.235 0.560
US-53, OH Crushed Stone 27.5 38.3 1.170 0.449 0.862
NCAT, FL Limerock 28.6 28.1 0.574 0.324 0.619
US-2, ND Crushed Aggregate 32.4 39.8 1.884 0.623 1.129
US-280, AL Crushed Stone 48.4 49.3 1.010 0.244 0.962
Average Ratios for Aggregate Base Materials 1.021 0.316 0.899
Overall Average Values 0.942 0.422 1.084
NOTES:
1. The adjustment ratio is determined by dividing the resilient modulus measured in the laboratory at a specific
stress state by the NDT estimated modulus.
2. The average ratios listed exclude the data from the I-85 low plasticity clay prior to IC rolling. The resilient
modulus regression equations are provided in Equations 1 through 15.
Embankments, Soil-Aggregate Mixture, Coarse-
-Grained dry
k3 = 0.9303 + 0.0293( P3 8 ) + 0.0036(LL) - 3.8903 (12)
k1 = 0.5856 + 0.0130 ( P3 8 ) - 0.0174 ( P#4 ) + 0.0027 ( P#200 ) Max
+ 0.0149(PI ) + 0.0000016 ( max ) - 0.0426 ( w s ) Fine-Grained Clay Soil
dry w 2Max
k1 = 1.3577 + 0.0106 (Clay ) - 0.0437 ( w s ) (13)
+ 1.6456 + 0.3932 s - 0.00000082 (7)
Max w Max
x P#40 k2 = 0.5193 - 0.0073( P#4 ) + 0.0095 ( P#40 ) - 0.0027 ( P#2
200 )
k2 = 0.7833 - 0.0060 ( P#200 ) - 0.0081(PI ) + 0.0001( Max ) - 0.0030(LL) - 0.0049 ( w s ) (14)
ws dry
2
k3 = 1.4258 - 0.0288 ( P#4 ) + 0.0303( P#40 ) - 0.0521( P#2
200 )
- 0.1483 + 0.00000027 (8)
w opt P#40 + 0.025(Silt ) + 0.0535(LL) - 0.0672 ( w opt )
opt
2
ws
k3 = -0.1906 - 0.0026 ( P#200 ) + 0.00000081 (9) - 0.0026 ( max ) + 0.0025 ( dry ) - 0.6055
P#40 w opt
(15)
Embankments, Soil-Aggregate Mixture,Fine-Gr
rained Figure 22 compares the laboratory measured resilient
k1 = 0.7668 + 0.0051( P#40 ) + 0.0128 ( P#200 ) + 0.0030(LL) modulus values and those calculated from the regression
equations (see Table 24). Use of the regression equations, on
dry average, resulted in a reasonable prediction of the labora-
- 0.051( w opt ) + 1.179 (10)
Max tory measured values. Yau and Von Quintus, however,
reported that the regression equations can result in significant
dry
k2 = 0.4951 - 0.0141( P#4 ) - 0.0061( P#200 ) + 1.3941 (11) error and recommended that repeated load resilient modulus
Max tests be performed.
OCR for page 49
49
Fine-Grained Soil Aggregate-Soil Mixture Crushed Aggregate Base
2
Adjustment Ratio for
1.5
GeoGauge
1
0.5
0
0 20 40 60 80 100
Percent Passing Number 200 Sieve, %
(a) GeoGauge.
Fine-Grained Soil Soil-Aggregate Mixture Crushed Aggregate Base
1.2
Adjustment Ratio for
1
0.8
DSPA
0.6
0.4
0.2
0
0 20 40 60 80 100
Percent Passing Number 200 Sieve, %
(b) DSPA.
Figure 21. Effect of the amount of fines on the adjustment
ratio for the GeoGauge and DSPA devices.
2.2.2 HMA Layers used to estimate the modulus values from the PSPA and FWD
for making relative comparisons. This field adjustment pro-
Table 25 lists the laboratory dynamic moduli measured at cedure is the same as that used for the unbound materials.
a loading frequency of 5.0 Hz for the in-place average mixture The adjustment ratios were determined for the areas without
temperature measured during NDT. As for the unbound any anomalies or physical differences from the target proper-
materials, it is expected that the modulus values determined ties and are given in Table 26.
from the deflection-based methods are affected by the sup- The PSPA adjustment ratios were found to be relatively close
porting materials. To compensate for differences between the to unity, with the exception of the I-35/SH-130 HMA base
laboratory and field conditions, an adjustment procedure was mixture. This HMA base mixture is a very stiff mixture in the
Resilient Modulus Calculated
50
from LTPP Equations, ksi
Line of Equality
40
Fine-Grained Soils
30
20 Embankment Soils;
Coarse-Grained
10 Granular Base
0
0 10 20 30 40 50
Resilient Modulus Measured in
Laboratory, ksi
Figure 22. Comparison of the resilient modulus values measured
in the laboratory to the resilient modulus values predicted with
the LTPP regression equations.
OCR for page 50
50
Table 25. Elastic modulus values estimated from NDT devices, without
any adjustments, in comparison to dynamic modulus values measured
in the laboratory.
Laboratory Values, ksi NDT Values, ksi
Project In Place
Part Layer/Mixture 130 °F & 5
Identification Temp. & 5 PSPA FWD
Hz
Hz
B I-75, Michigan Dense-Graded; Type 3-C 190 400 435.2 ---
B NCAT, Florida Base, Mix; PG67 203 390 447.1 ---
NCAT, S.
B Base Mix; PG67 214 410 495.2 ---
Carolina
Fine-Graded Surface; Type
B I-75, Michigan 255 590 676.3 ---
E10
A I-85, Alabama SMA Mixture 230 250 237 450
45% RAP; Sect. E-5,
B NCAT, Alabama 250 450 510.7 ---
PG67
B US-47, Missouri Fine-Graded Surface 276 530 457.6 ---
TH-23,
A HMA Base Mixture 319 810 480 ---
Minnesota
US-280,
A HMA Base; Initial Area 330 650 462 165
Alabama
B US-47, Missouri Coarse-Graded Base 344 420 605.3 ---
Coarse-Graded Base;
B US-2, N. Dakota 356 510 344.3 ---
PG58-28
B NCAT, Florida Base Mix, SBS, PG76 366 590 475.8 ---
45% RAP, Sect. E-7;
B NCAT, Alabama 421 610 444.3 ---
PG76 (Sasobit)
45% RAP, Sect. E-6;
B NCAT, Alabama 427 640 473.4 ---
PG76 (SBS)
B US-53, Ohio Coarse-graded Binder Mix 479 850 666.7 ---
B I-20, Texas HMA Base, CMHB 520 340 435.5 ---
US-280, HMA Base; Supplemental
A 613 780 558 310
Alabama Area
A SH-130, Texas HMA Base 965 1,750 342 725
Table 26. Dynamic modulus values measured in the laboratory and
adjustment factors for the modulus estimating NDT devices.
Dynamic Ratio or Adjustment Factor
Project/Mixture
Modulus, ksi PSPA FWD
I-85 AL, SMA Overlay 250 1.055 0.556
TH-23 MN, HMA Base 810 1.688 NA
US-280 AL, HMA Base; Initial Area 650 1.407 3.939
US-280 AL, HMA Base; Supplemental Area 780 1.398 2.516
I-35/SH-130 TX, HMA Base 1,750 5.117 3.253
I-75 MI, Dense-Graded Type 3-C 400 0.919 NA
I-75 MI, Dense-Graded Type E-10 590 0.756 NA
US-47 MO, Fine-Graded Surface 530 1.158 NA
US-47 MO, Coarse-Graded Base Mix 420 0.694 NA
I-20 TX, HMA Base, CMHB 340 0.799 NA
US-53 OH, Coarse-Graded Base 850 1.275 NA
US-2 ND, Coarse-Graded Base, PG58-28 510 1.482 NA
NCAT SC, PG67 Base Mix 410 0.828 NA
NCAT FL, PG67 Base Mix 390 0.872 NA
NCAT FL, PG76 Base Mix 590 1.240 NA
NCAT AL, PG76 with RAP and Sasobit 610 1.3760 NA
NCAT AL, PG76 with RAP and SBS 640 1.352 NA
NCAT AL, PG67 with RAP 450 0.881 NA
Overall Average Ratio or Adjustment Factor 1.128 2.566
NOTES:
1. The adjustment factor or ratio was determined by dividing the dynamic modulus measured in the laboratory
for the in-place temperature at a loading frequency of 5 Hz by the modulus estimated with the NDT device.
2. The laboratory dynamic modulus values listed are for a test temperature of a loading frequency of 5 Hz at
the temperature of the mixture when the NDT was performed (see Table 25).
3. The overall average adjustment factor excludes the SH-130 mixture (shaded in the table) because it was
found to be significantly different than any other mixture tested.
