Difference between revisions of "106.3.2.41 TM-41, Density Testing of Bituminous Mixtures with Nuclear Gauges"

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m (Per CM, article moved to conform with Sec 106. Old EPG 106.7.41 had no appreciable history and 839 hits)
(updated per RR3840 - rewrite of TM-41)
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<div style="float: right; margin-left: 30px; margin-bottom: 30px;">__TOC__</div>
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[[image:106.7.41.jpg|right|300px]]
 
[[image:106.7.41.jpg|right|300px]]
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This test method establishes the procedures for density testing of bituminous mixtures with nuclear gauges. These procedures apply to the direct transmission nuclear test rode: used for (1) plant mix bituminous base, (2) Type C or D asphaltic concrete mixtures constructed in layers 2 in. thick or thicker and (3) for Type B asphaltic concrete only when used in lieu of plant mix bituminous base in layers 2 in. thick or thicker and to the backscatter nuclear test mode used only for Type C or D asphaltic concrete mixtures constructed in layers less than 2 in. thick.
+
 
 +
This test method establishes the procedures for density testing of bituminous mixtures with nuclear gauges. These procedures apply to the backscatter nuclear test mode and direct transmission mode. Backscatter nuclear test mode should be used for asphaltic concrete mixtures 3-inches or less. Paving lifts greater than 3-inches shall be cored.
  
 
==106.3.2.41.1 Apparatus==
 
==106.3.2.41.1 Apparatus==
  
−
a) Nuclear gauges meeting the apparatus and precision requirements of ASTM D 2950-74.
+
a) Nuclear gauges with supporting equipment meeting the apparatus and precision requirements of AASHTO T 355. Other non-nuclear gauges will be allowed if acceptable correlations are obtained during the test strip.<br>
−
 
+
b) Fine sand to fill all voids if applicable.<br>
−
b) Equipment required to determine specific gravity of compacted bituminous mixtures.
+
c) Equipment required to determine specific gravity of compacted bituminous mixtures.<br>
 +
d) Drilling equipment capable of obtaining 4 in. diameter undisturbed cores from the pavement.<br>
  
−
c) Drilling equipment capable of obtaining 4 in. diameter undisturbed cores from the bituminous mixtures.
+
==106.3.2.41.2 Preliminary Procedures for Standardization==
  
−
==106.3.2.41.2 Procedures==
+
Tests shall be performed in accordance with AASHTO T 355.
  
−
Tests shall be performed in accordance with ASTM D 2950-74 except that Section 3 shall be deleted and a correction factor determined for each mixture.
+
Standardization of the nuclear gauge on a reference standard block is required at the start of each day’s use and when test measurements are suspect. The following steps shall be conducted:
  
−
Direct transmission tests shall be made at a sufficient depth to test the entire lift. Testing depth shall be the next probe increment greater than the lift thickness when the lift thickness and depth increment do not coincide.
+
:1) Warm up the nuclear gauge in accordance with the manufacturer’s recommendations.
 +
:2) Properly seat the nuclear gauge on the standard block and take a four-minute reading on the reference standard. The density shall be within 1% of the density for the previous day’s reading. If not, or on the first day, repeat the four-minute reading. The two numbers shall be within 1% of each other and within 2% of the density of the previous day’s reading. If the readings do not compare, check the machine for malfunction.  
  
 
==106.3.2.41.3 Correction Factor Determination==
 
==106.3.2.41.3 Correction Factor Determination==
  
−
Obtain the required number of tests from within an area of the compacted mixture for the width being laid by at least 400 ft. long for the direct transmission method and at least 650 ft. long for the backscatter method.
+
Correction factors for nuclear gauges shall be determined during the trial section in accordance with Section 405.4.8 (provided below). All nuclear gauges shall collect density readings at the five Evaluation Locations on the test strip along with density cores.
  
−
Note 1 - Material within one foot of an edge or joint shall not be tested.
+
At each Evaluation Location, 5 one-minute readings shall be taken with the nuclear gauge in the backscatter mode position and mark the outline of the gauge in these locations. Record the wet density values, discard the single and highest and lowest values, average the three remaining values, and record the average value.  
  
−
Test sites, one per increment, shall be randomly selected both longitudinally and transversely by use of [[#106.3.2.41.7 Random Numbers|a table of random numbers]]. An increment equals the length of test area divided by the required number of tests. At each nuclear test site obtain a core for specific gravity determination. The core site should be located between the source and detectors of the nuclear gauge so hat the same material is tested.
+
:Note: Material within one foot of an edge or joint shall not be tested. Check tip of source rod to assure it is free of any foreign substances.
  
−
The minimum number of tests required to establish the correction factor are 16 tests for the backscatter mode and 4 tests for the direct transmission mode.
+
Two to three pavement cores shall be cut at each Evaluation Location corresponding to the nuclear gauge location. The Gmb shall be determined for each core in accordance with AASHTO T 166. The average bulk density of the cores shall be calculated by the Gmb x 62.245 lb/ft<sup>3</sup> at each Evaluation Location.
  
−
A new correction factor shall be determined when here is a change in the job mix, a change in the source of materials or in the material from the same source, a change from one gauge to another or when there is any other reason to believe that the correction factor is in error.
+
The correction factor for each gauge shall be determined by the five Evaluation Locations within the test strip. The two data sets shall be evaluated for outliers by the “T” Statistic Test at 95% confidence level. The following provides an example.
  
−
==106.3.2.41.4 Compliance Testing==
+
:N = Number of Evaluation Locations
−
Compliance tests shall be performed in lots. Lots shall be selected 1,000 ft. in length by the normal width being constructed, from each 500 tons of the constructed mixture. (See Note 1, above.)
+
:di = Difference between Core Density and Nuclear Gauge Density
 +
:CF = Correction Factor is the average of the di
 +
:S = Standard Deviation
 +
:“T” Test = Finds Outliers
  
−
Test sites shall be randomly located both longitudinally and transversely by use of a table of random numbers. One random test site shall be selected in each 200-ft. increment of the lot for a total of 5 test sites. A nuclear density test by the appropriate method for the mixture should be performed at each test site while the mixture is amenable to rolling.
+
{|
 +
|
 +
{| class="wikitable" style="text-align:center;"
 +
! colspan="2" | Rejection Quotients
 +
|-
 +
| N || T<sub>0.95</sub>
 +
|-
 +
| 3 || 1.15
 +
|-
 +
| 4 || 1.46
 +
|-
 +
| 5 || 1.67
 +
|-
 +
| 6 || 1.82
 +
|-
 +
| 7 || 1.94
 +
|-
 +
| 8 || 2.03
 +
|-
 +
| 9 || 2.11
 +
|-
 +
| 10 || 2.18
 +
|}
 +
| style = "width: 20px" |
 +
|
 +
{| class="wikitable" style="text-align:center;"
 +
|-
 +
! Evaluation</br>Location !! Avg. Gmb<sub>Cores</sub></br>(AASHTO  T166) !! Bulk Density of</br>Cores (lb/ft3) !! Avg. Nuclear Gauge</br>Reading (%) !! Difference (di) !! (di  – CF) !! (di  – CF)<sup>2</sup>
 +
|-
 +
| 1 || 2.400 || 149.4 || 152.6 || -3.2 || -2.7 || 7.29
 +
|-
 +
|| 2 || 2.432 || 151.4 || 151.2 || 0.2 || 0.6 || 0.36
 +
|-
 +
|| 3 || 2.421 || 150.7 || 150.7 || 1.8 || 2.3 || 5.29
 +
|-
 +
|| 4 || 2.411 || 150.1 || 150.1 || 0.4 || 0.64 || 6.25
 +
|-
 +
|| 5 || 2.388 || 148.6 || 148.6 || -1.5 || -1.0 || 1.00
 +
|-
 +
|| N = 5 || Gmm = 2.555 || || Correction Factor (CF) || -0.5 || ||
 +
|}
 +
|
 +
|}
  
−
==106.3.2.41.5 Sampling==
+
Correction Factor (CF) = Average of Differences = -0.5
  
−
A compacted sample shall be taken every second day except when production exceeds
+
Standard Deviation (S) = <math>\sqrt \frac {\mathit{\Sigma} \ (di - CF) ^2}{ \ n-1 } = 1.9</math>;    Is S < 2.5?
−
3,000 tons per day in which case a sample shall be taken daily. A compacted sample shall consist of four cores for layers 4 in. thick or less and two cores for layers over 4 in. thick. The cores shall be taken directly under the nuclear density testing device between the source and detectors. The compacted sample shall be submitted to the Laboratory for testing.
 
  
−
==106.3.2.41.6 Calculations==
+
Standard Deviation shall be less than 2.5; if not – redo test strip
  
−
'''Correction factor (C.F.)'''
+
'''<u>Calibration of Nuclear Gauge</u>'''
  
−
::C.F. = Nd – Cd
+
Max. Absolute Value of ǀ di – CF ǀ = 2.7
  
−
::Where:
+
“T” Test = Max. Abs. of (ǀ di – CF ǀ) / S = 2.7 / 2.0 = 1.41
  
−
:::Nd = Average nuclear gauge density in pcf
+
Is “T Test” value < T<sub>0.95</sub> @ N = 5
−
:::Cd = Average core density in pcf = specific gravity x 62.4 pcf
 
  
−
:::Note 2: When Nd > Cd, subtract C.F.
+
If “T” Test (1.41) < T<sub>0.95</sub> @ N = 5 (1.67); All results acceptable
−
:::When Nd < Cd, add C.F.
 
  
−
::Determine all values to nearest 0.1 pcf.
+
If “T” Test value greater than 1.67; Discard results at the evaluation location, recalculate with N=4 for the remaining locations and re-test. If these results fail; then nuclear correlation does not pass and more cores shall be taken for correlation or only use cores for density pay factors.  
  
−
'''Percent compaction'''
+
A minimum of four data points must pass the T-test in part 106.3.2.41.3 of this test method. 
  
−
::Percent compaction = (100 x CN) / "d" (62.4 pcf)
+
The standard deviation shall be less than or equal to 2.5. If it is larger than 2.5, then there is too much variation in the densities of the test strip and the test strip would need to be redone.
  
−
::Where:
+
The “T” Test value shall be less than “T<sub>0.95</sub>” at the critical n value for an acceptable calibration of the nuclear gauge device within the test strip.
  
−
:::CN = corrected nuclear density in pcf (Average of 5 Tests)
+
The correction factor (CF) is applied to each nuclear density reading on the project to obtain a corrected nuclear density.
−
:::"d" = specific gravity of a laboratory compacted specimen made in the proportions of the approved mixture
 
  
−
::Determine corrected nuclear density to nearest 0.1 pcf.
+
When calibrating multiple gauges, if it becomes necessary to discard a location because it failed the standard deviation (S) or the “T” test, then the same location must be discarded for all gauges being calibrated using these set of cored locations.
−
::Report percent compaction to the nearest whole percent.
 
  
−
==106.3.2.41.7 Random Numbers==
+
==106.3.2.41.4 QC/QA Sampling==
  
−
The test procedure requires that test sites both for determining the nuclear gauge correction factor and for compliance testing be randomly located by using the table of random numbers.
+
For QC testing random test locations shall be determined by the anticipated amount of paving and the Quality Control plan in accordance with Sec 403.  The nuclear gauge shall be in backscatter mode and properly seated in accordance with AASHTO T355 and record the following information:
 +
:Take 5 one-minute readings with the nuclear density gauge and mark the outline of the gauge at the random location.
 +
:Record the 5 nuclear density values in lb/ft<sup>3</sup>,
 +
:Discard the single highest and lowest values,
 +
:Average the three remaining values.
  
−
===106.3.2.41.7.1 Computation of Test Site Locations===
+
==106.3.2.41.5 Calculations==
−
Both [[#106.3.2.41.3 Correction Factor Determination |EPG 106.3.2.41.3 Correction Factor Determination]] and [[#106.3.2.41.4 Compliance Testing|EPG 106.3.2.41.4 Compliance Testing]] give the dimensions of the test area and lot, respectively. Note 1 excludes material from within one foot of an edge or joint from testing. The length of the area or lot will not be affected by Note 1 provided the first and last foot of the days operation are excluded from consideration; however, the test width will always be two feet narrower than the width being laid because one foot on each side is excluded from testing.
 
  
−
An example of the use of the table of random numbers for compliance testing follows:
+
Correction Factor (CF) – The CF established during the test strip shall be reported.
 +
:Gmm – The Gmm from the most recent sublot shall be reported.
 +
:Density of Water @ 77 F = 62.245 lb/ft<sup>3</sup>
  
−
The first step is to select a lot 1,000 ft-long by the width (assumed to be 12 ft.) being laid. The lot can be selected from anywhere within the area covered by 500 tons of the constructed mixture. The lot is then divided into 5 increments each 200 ft. in length. Note the beginning station number of each increment.
+
The Average Nuclear Density (ND) from the random sampling location shall be reported and the CF from the test strip applied to report the ND (corrected) value.
  
−
The second step is to select the required sets of numbers from Table 106.3.2.41.7 Random Numbers. Start at any point in the table and, proceeding up or down, pick 5 successive sets of numbers. Once a starting point and direction in the table are chosen, successive pairs of numbers are selected. Skipping pairs of numbers or reversing the direction is not permitted. Should a test site be judged unfit for testing, the next pair of numbers in the table is chosen to locate an alternate site within the increment. Also, should all the pairs of numbers be used on a project, continue through the table of random numbers in the same direction without skipping.
+
ND<sub>Corr</sub> = ND + (CF Value from Test Strip); where either a positive or negative CF is added to ND.
  
−
The third step is to compute the location of the test sites.  
+
Calculate Bulk Specific Gravity of Nuclear Density (G<sub>ND</sub>);
 +
:G<sub>ND</sub> = ND<sub>Corr</sub> / 62.245
  
−
===106.3.2.41.7.2 An Example of a Test Site Location Computation===
+
Calculate % of Theoretical Maximum Density (% Density);
−
'''Step 1:'''
+
:% Density = G<sub>ND</sub> / Gmm * 100
−
Test lot begins at Station 200+00 and ends at Station 210+00. Required number of tests is 5.
+
:Report % Density to the nearest 0.1
  
−
Testing increment is 1,000 ft. divided by 5 or 200 ft. Test width is 10 ft (exclude one ft. from each side of the 12 ft. width being laid).
+
==106.3.2.41.6 Results==
  
−
'''Step 2:'''
+
If either QC or QA are questioning the values of nuclear gauge readings on a sublot; coring shall be conducted to determine the pay factors for that sublot.
−
Select 5 successive sets of numbers from the able of random numbers. Start with the 6th number in column 2 and proceed down. (The fact that each block has 5 sets of numbers has no significance.)
 
  
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
+
QA may not have the means of using a nuclear gauge methods; therefore, QA sampling by cores will continue and compared to the QC nuclear gauge readings.
−
|+ '''Numbers Selected'''
+
 
−
! style="background:#BEBEBE"| A !! style="background:#BEBEBE"| B
+
Nuclear density measurements may also be used for random unconfined longitudinal joint testing following the same sampling procedures described above. The source rod of the gauge shall be within 8 to 12 inches of the mid-vertical edge of the mat.
−
|-
 
−
|.554|| .627
 
−
|-
 
−
|.225|| .163
 
−
|-
 
−
|.035|| .039
 
−
|-
 
−
|.334|| .921
 
−
|-
 
−
|.576|| .417
 
−
|}
 
  
−
'''Step 3:'''
 
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
−
|+ '''Computation of Test Station'''
 
−
! style="background:#BEBEBE"| Station of Beginning of Increment !! style="background:#BEBEBE"|Test A x Increment !! style="background:#BEBEBE"| Station
 
−
|-
 
−
|align="center"|200+00 ||align="center"|+ (.554 x 200')||align="center"| = 201+11
 
−
|-
 
−
|align="center"|202+00 ||align="center"|+ (.225 x 200')||align="center"| = 202+45
 
−
|-
 
−
|align="center"|204+00 ||align="center"|+ (.035 x 200')||align="center"| = 204+07
 
−
|-
 
−
|align="center"|206+00 ||align="center"|+ (.334 x 200')|| align="center"|= 206+67
 
−
|-
 
−
|align="center"|208+00 ||align="center"|+ (.576 x 200')||align="center"| = 209+15
 
−
|}
 
  
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
−
|+ '''Computation of Offset'''
 
−
! style="background:#BEBEBE"| B x Test Width!! style="background:#BEBEBE"| Offset<sup>1</sup>
 
−
|-
 
−
|align="center"|.627 x 10' = 6.3'||align="center"| 7.3'
 
−
|-
 
−
|align="center"|.163 x 10' = 1.6'|| align="center"|2.6'
 
−
|-
 
−
|align="center"|.039 x 10' = 0.4'||align="center"| 1.4'
 
−
|-
 
−
|align="center"|.921 x 10' = 9.2'||align="center"| 10.2'
 
−
|-
 
−
|align="center"|.417 x 10' = 4.2' ||align="center"|5.2'
 
−
|-
 
−
|colspan="2" width=450px|<sup>1</sup> Offset includes the one foot exclusion between test site and measurement reference (centerline or edge). Also, the width of a previously laid pass can be included.
 
−
|}
 
  
−
=== Table 106.3.2.41.7 Random Numbers===
 
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
−
|+
 
−
!style="background:#BEBEBE" colspan="2"| 1!! style="background:#BEBEBE" colspan="2"| 2 !!style="background:#BEBEBE" colspan="2"| 3!! style="background:#BEBEBE" colspan="2"| 4!! style="background:#BEBEBE" colspan="2"| 5
 
−
|-
 
−
!style="background:#BEBEBE"|A!! style="background:#BEBEBE"|B!! style="background:#BEBEBE"|A!! style="background:#BEBEBE"|B!! style="background:#BEBEBE"|A!! style="background:#BEBEBE"|B!! style="background:#BEBEBE"|A!! style="background:#BEBEBE"|B!! style="background:#BEBEBE"|A!! style="background:#BEBEBE"|B!!
 
−
|-
 
−
|align="center"| .576 || align="center"| .730|| align="center"|  .430|| align="center"|  .754|| align="center"|  .271|| align="center"|  .870|| align="center"|  .732|| align="center"|  .721|| align="center"|  .998|| align="center"|  .239
 
−
|-
 
−
| align="center"|.892 || align="center"|  .948 || align="center"|  .858|| align="center"|  .025|| align="center"|  .935|| align="center"|  .114|| align="center"|  .153|| align="center"|  .508 || align="center"|  .749|| align="center"|  .291
 
−
|-
 
−
|align="center"|.669 || align="center"|  .726|| align="center"|  .501|| align="center"|  .402|| align="center"|  .231|| align="center"|  .505|| align="center"|  .009|| align="center"|  .420 || align="center"|  .517|| align="center"|  .858
 
−
|-
 
−
|align="center"|.609 || align="center"|  .482 || align="center"|  .809|| align="center"|  .140|| align="center"|  .396|| align="center"|  .025|| align="center"|  .937|| align="center"|  .310 || align="center"|  .253|| align="center"|  .761
 
−
|-
 
−
|align="center"|.971 || align="center"|  .824|| align="center"|  .902|| align="center"|  .470|| align="center"|  .997|| align="center"|  .392|| align="center"|  .892|| align="center"|  .957 || align="center"|  .640|| align="center"|  .463
 
−
|-
 
−
| colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| -
 
−
|-
 
−
|align="center"|.053 || align="center"|  .899|| align="center"|  .554|| align="center"|  .627|| align="center"|  .427|| align="center"|  .760|| align="center"|  .470|| align="center"|  .040 || align="center"|  .904|| align="center"|  .993
 
−
|-
 
−
|align="center"|.810 || align="center"|  .159|| align="center"|  .225|| align="center"|  .163|| align="center"|  .549|| align="center"|  .405|| align="center"|  .285|| align="center"|  .542 || align="center"|  .231|| align="center"|  .919
 
−
|-
 
−
|align="center"|.081 || align="center"|  .277|| align="center"|  .035|| align="center"|  .039|| align="center"|  .860|| align="center"|  .507|| align="center"|  .081|| align="center"|  .538 || align="center"|  .986|| align="center"|  .501
 
−
|-
 
−
|align="center"|.982 || align="center"|  .468|| align="center"|  .334|| align="center"|  .921|| align="center"|  .690|| align="center"|  .806|| align="center"|  .879|| align="center"|  .414 || align="center"|  .106|| align="center"|  .031
 
−
|-
 
−
|align="center"|.095 || align="center"|  .801|| align="center"|  .576|| align="center"|  .417|| align="center"|  .251|| align="center"|  .884|| align="center"|  .522|| align="center"|  .235 || align="center"|  .398|| align="center"|  .222
 
−
|-
 
−
| colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| -
 
−
|-
 
−
|align="center"|.509|| align="center"|  .025|| align="center"|  .794|| align="center"|  .850|| align="center"|  .917|| align="center"|  .887|| align="center"|  .751|| align="center"|  .608 || align="center"|  .698|| align="center"|  .683
 
−
|-
 
−
|align="center"|.371|| align="center"|  .059|| align="center"|  .164|| align="center"|  .838|| align="center"|  .289|| align="center"|  .169|| align="center"|  .569|| align="center"|  .977 || align="center"|  .796|| align="center"|  .996
 
−
|-
 
−
|align="center"|.165 || align="center"|  .996|| align="center"|  .356|| align="center"|  .375|| align="center"|  .654|| align="center"|  .979|| align="center"|  .815|| align="center"|  .592 || align="center"|  .348|| align="center"|  .743
 
−
|-
 
−
|align="center"|.477 || align="center"|  .535 || align="center"|  .137|| align="center"|  .155|| align="center"|  .767|| align="center"|  .187|| align="center"|  .579|| align="center"|  .797 || align="center"|  .358|| align="center"|  .595
 
−
|-
 
−
|align="center"|.788 || align="center"|  .101 || align="center"|  .434|| align="center"|  .638|| align="center"|  .021|| align="center"|  .894|| align="center"|  .324|| align="center"|  .871 || align="center"|  .698|| align="center"|  .539
 
−
|-
 
−
| colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| -
 
−
|-
 
−
|align="center"|.566 || align="center"|  .815|| align="center"|  .655|| align="center"|  .548|| align="center"|  .947|| align="center"|  .169|| align="center"|  .817|| align="center"|  .472 || align="center"|  .864|| align="center"|  .466
 
−
|-
 
−
|align="center"|.901|| align="center"|  .342|| align="center"|  .873|| align="center"|  .964|| align="center"|  .942|| align="center"|  .985|| align="center"|  .123|| align="center"|  .086 || align="center"|  .335|| align="center"|  .212
 
−
|-
 
−
|align="center"|.470 || align="center"|  .682|| align="center"|  .412|| align="center"|  .064|| align="center"|  .150|| align="center"|  .962|| align="center"|  .925|| align="center"|  .355 || align="center"|  .909|| align="center"|  .019
 
−
|-
 
−
|align="center"|.068 || align="center"|  .242|| align="center"|  .667|| align="center"|  .356|| align="center"|  .195|| align="center"|  .313|| align="center"|  .396|| align="center"|  .460 || align="center"|  .740|| align="center"|  .247
 
−
|-
 
−
|align="center"|.874 || align="center"|  .420|| align="center"|  .127|| align="center"|  .284|| align="center"|  .448|| align="center"|  .215|| align="center"|  .833|| align="center"|  .652 || align="center"|  .601|| align="center"|  .326
 
−
|-
 
−
| colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| -
 
−
|-
 
−
|align="center"|.897|| align="center"|  .877|| align="center"|  .209|| align="center"|  .862|| align="center"|  .428|| align="center"|  .117|| align="center"|  .100|| align="center"|  .259 || align="center"|  .425|| align="center"|  .284
 
−
|-
 
−
|align="center"|.875 || align="center"|  .969|| align="center"|  .109|| align="center"|  .843|| align="center"|  .759|| align="center"|  .239|| align="center"|  .890|| align="center"|  .317 || align="center"|  .428|| align="center"|  .802
 
−
|-
 
−
|align="center"|.190 || align="center"|  .696 || align="center"|  .757|| align="center"|  .283|| align="center"|  .666|| align="center"|  .491|| align="center"|  .523|| align="center"|  .665 || align="center"|  .919|| align="center"|  .146
 
−
|-
 
−
|align="center"|.341 || align="center"|  .688|| align="center"|  .587|| align="center"|  .908|| align="center"|  .865|| align="center"|  .333|| align="center"|  .928|| align="center"|  .404 || align="center"|  .892|| align="center"|  .696
 
−
|-
 
−
|align="center"|.846|| align="center"|  .355|| align="center"|  .831|| align="center"|  .218|| align="center"|  .945|| align="center"|  .364|| align="center"|  .673|| align="center"|  .305 || align="center"|  .195|| align="center"|  .887
 
−
|-
 
−
| colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| -
 
−
|-
 
−
|align="center"|.882 || align="center"|  .227|| align="center"|  .552|| align="center"|  .077|| align="center"|  .454|| align="center"|  .731|| align="center"|  .716|| align="center"|  .265 || align="center"|  .058|| align="center"|  .075
 
−
|-
 
−
|align="center"|.464 || align="center"|  .658|| align="center"|  .629|| align="center"|  .269|| align="center"|  .069|| align="center"|  .998|| align="center"|  .917|| align="center"|  .217 || align="center"|  .220|| align="center"|  .659
 
−
|-
 
−
|align="center"|.123 || align="center"|  .791|| align="center"|  .503|| align="center"|  .447|| align="center"|  .659|| align="center"|  .463|| align="center"|  .994|| align="center"|  .307 || align="center"|  .631|| align="center"|  .422
 
−
|-
 
−
|align="center"|.116 || align="center"|  .120|| align="center"|  .721|| align="center"|  .137|| align="center"|  .263|| align="center"|  .176|| align="center"|  .798|| align="center"|  .879 || align="center"|  .432|| align="center"|  .391
 
−
|-
 
−
|align="center"|.836 || align="center"|  .206|| align="center"|  .914|| align="center"|  .574|| align="center"|  .870|| align="center"|  .390|| align="center"|  .104|| align="center"|  .755 || align="center"|  .082|| align="center"|  .939
 
−
|-
 
−
| colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| - ||colspan="2" align="center"| -
 
−
|-
 
−
|align="center"|.636|| align="center"|  .195|| align="center"|  .614|| align="center"|  .486|| align="center"|  .629|| align="center"|  .663|| align="center"|  .619|| align="center"|  .007 || align="center"|  .296|| align="center"|  .456
 
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|-
 
−
|align="center"|.630|| align="center"|  .673|| align="center"|  .665|| align="center"|  .666|| align="center"|  .399|| align="center"|  .592|| align="center"|  .441|| align="center"|  .649 || align="center"|  .270|| align="center"|  .612
 
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|-
 
−
|align="center"|.804 || align="center"|  .112|| align="center"|  .331|| align="center"|  .606|| align="center"|  .551 || align="center"|  .928|| align="center"|  .830 || align="center"|  .841 || align="center"|  .602|| align="center"|  .183
 
−
|-
 
−
|align="center"|.360 || align="center"|  .093|| align="center"|  .181|| align="center"|  .399|| align="center"|  .564|| align="center"|  .772|| align="center"|  .890|| align="center"|  .062 || align="center"|  .919|| align="center"|  .875
 
−
|-
 
−
|align="center"|.183 || align="center"|  .651 || align="center"|  .157|| align="center"|  .150|| align="center"|  .800|| align="center"|  .875|| align="center"|  .205|| align="center"|  .446 || align="center"|  .648|| align="center"|  .685
 
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|}
 
  
  
  
 
[[Category:106.3.2 Material Inspection Test Methods]]
 
[[Category:106.3.2 Material Inspection Test Methods]]

Revision as of 16:13, 21 February 2024

106.7.41.jpg

This test method establishes the procedures for density testing of bituminous mixtures with nuclear gauges. These procedures apply to the backscatter nuclear test mode and direct transmission mode. Backscatter nuclear test mode should be used for asphaltic concrete mixtures 3-inches or less. Paving lifts greater than 3-inches shall be cored.

106.3.2.41.1 Apparatus

a) Nuclear gauges with supporting equipment meeting the apparatus and precision requirements of AASHTO T 355. Other non-nuclear gauges will be allowed if acceptable correlations are obtained during the test strip.
b) Fine sand to fill all voids if applicable.
c) Equipment required to determine specific gravity of compacted bituminous mixtures.
d) Drilling equipment capable of obtaining 4 in. diameter undisturbed cores from the pavement.

106.3.2.41.2 Preliminary Procedures for Standardization

Tests shall be performed in accordance with AASHTO T 355.

Standardization of the nuclear gauge on a reference standard block is required at the start of each day’s use and when test measurements are suspect. The following steps shall be conducted:

1) Warm up the nuclear gauge in accordance with the manufacturer’s recommendations.
2) Properly seat the nuclear gauge on the standard block and take a four-minute reading on the reference standard. The density shall be within 1% of the density for the previous day’s reading. If not, or on the first day, repeat the four-minute reading. The two numbers shall be within 1% of each other and within 2% of the density of the previous day’s reading. If the readings do not compare, check the machine for malfunction.

106.3.2.41.3 Correction Factor Determination

Correction factors for nuclear gauges shall be determined during the trial section in accordance with Section 405.4.8 (provided below). All nuclear gauges shall collect density readings at the five Evaluation Locations on the test strip along with density cores.

At each Evaluation Location, 5 one-minute readings shall be taken with the nuclear gauge in the backscatter mode position and mark the outline of the gauge in these locations. Record the wet density values, discard the single and highest and lowest values, average the three remaining values, and record the average value.

Note: Material within one foot of an edge or joint shall not be tested. Check tip of source rod to assure it is free of any foreign substances.

Two to three pavement cores shall be cut at each Evaluation Location corresponding to the nuclear gauge location. The Gmb shall be determined for each core in accordance with AASHTO T 166. The average bulk density of the cores shall be calculated by the Gmb x 62.245 lb/ft3 at each Evaluation Location.

The correction factor for each gauge shall be determined by the five Evaluation Locations within the test strip. The two data sets shall be evaluated for outliers by the “T” Statistic Test at 95% confidence level. The following provides an example.

N = Number of Evaluation Locations
di = Difference between Core Density and Nuclear Gauge Density
CF = Correction Factor is the average of the di
S = Standard Deviation
“T” Test = Finds Outliers
Rejection Quotients
N T0.95
3 1.15
4 1.46
5 1.67
6 1.82
7 1.94
8 2.03
9 2.11
10 2.18
Evaluation
Location		 Avg. GmbCores
(AASHTO T166)		 Bulk Density of
Cores (lb/ft3)		 Avg. Nuclear Gauge
Reading (%)		 Difference (di) (di – CF) (di – CF)2
1 2.400 149.4 152.6 -3.2 -2.7 7.29
2 2.432 151.4 151.2 0.2 0.6 0.36
3 2.421 150.7 150.7 1.8 2.3 5.29
4 2.411 150.1 150.1 0.4 0.64 6.25
5 2.388 148.6 148.6 -1.5 -1.0 1.00
N = 5 Gmm = 2.555 Correction Factor (CF) -0.5

Correction Factor (CF) = Average of Differences = -0.5

Standard Deviation (S) = ; Is S < 2.5?

Standard Deviation shall be less than 2.5; if not – redo test strip

Calibration of Nuclear Gauge

Max. Absolute Value of ǀ di – CF ǀ = 2.7

“T” Test = Max. Abs. of (ǀ di – CF ǀ) / S = 2.7 / 2.0 = 1.41

Is “T Test” value < T0.95 @ N = 5

If “T” Test (1.41) < T0.95 @ N = 5 (1.67); All results acceptable

If “T” Test value greater than 1.67; Discard results at the evaluation location, recalculate with N=4 for the remaining locations and re-test. If these results fail; then nuclear correlation does not pass and more cores shall be taken for correlation or only use cores for density pay factors.

A minimum of four data points must pass the T-test in part 106.3.2.41.3 of this test method.

The standard deviation shall be less than or equal to 2.5. If it is larger than 2.5, then there is too much variation in the densities of the test strip and the test strip would need to be redone.

The “T” Test value shall be less than “T0.95” at the critical n value for an acceptable calibration of the nuclear gauge device within the test strip.

The correction factor (CF) is applied to each nuclear density reading on the project to obtain a corrected nuclear density.

When calibrating multiple gauges, if it becomes necessary to discard a location because it failed the standard deviation (S) or the “T” test, then the same location must be discarded for all gauges being calibrated using these set of cored locations.

106.3.2.41.4 QC/QA Sampling

For QC testing random test locations shall be determined by the anticipated amount of paving and the Quality Control plan in accordance with Sec 403. The nuclear gauge shall be in backscatter mode and properly seated in accordance with AASHTO T355 and record the following information:

Take 5 one-minute readings with the nuclear density gauge and mark the outline of the gauge at the random location.
Record the 5 nuclear density values in lb/ft3,
Discard the single highest and lowest values,
Average the three remaining values.

106.3.2.41.5 Calculations

Correction Factor (CF) – The CF established during the test strip shall be reported.

Gmm – The Gmm from the most recent sublot shall be reported.
Density of Water @ 77 F = 62.245 lb/ft3

The Average Nuclear Density (ND) from the random sampling location shall be reported and the CF from the test strip applied to report the ND (corrected) value.

NDCorr = ND + (CF Value from Test Strip); where either a positive or negative CF is added to ND.

Calculate Bulk Specific Gravity of Nuclear Density (GND);

GND = NDCorr / 62.245

Calculate % of Theoretical Maximum Density (% Density);

% Density = GND / Gmm * 100
Report % Density to the nearest 0.1

106.3.2.41.6 Results

If either QC or QA are questioning the values of nuclear gauge readings on a sublot; coring shall be conducted to determine the pay factors for that sublot.

QA may not have the means of using a nuclear gauge methods; therefore, QA sampling by cores will continue and compared to the QC nuclear gauge readings.

Nuclear density measurements may also be used for random unconfined longitudinal joint testing following the same sampling procedures described above. The source rod of the gauge shall be within 8 to 12 inches of the mid-vertical edge of the mat.

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