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CT 375 Backscatter > CT 375 Backscatter > Flashcards

CT 375 Backscatter Flashcards

1
Q

What is the Title of CT 375?

A

Determining the In-place Density and Relative Compaction of Hot Mix Asphalt Pavement using Nuclear Gages

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2
Q

Backscatter can be used on HMA thickness of at least how much?

A

At least 0.10 ft.

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3
Q

What must be done for each nuke gage to correlate to core densities?

A

A conversion factor must be developed for each gage for each project.

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4
Q

What must be done daily with your nuke gage before you can take any readings?

A

Standardize the gage

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5
Q

When must you establish a new conversion factor? 5 criteria.

A

Change in lift thickness of 1/2” or more, underlying material, material source, mix design, or recalibration of the nuclear gage.

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6
Q

A test strip must have the same what criteria in order to be considered?

A

Same HMA binder type, binder content, aggregate source, agg type, and grading.

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7
Q

How thick must the test strip be in order to be considered?

A

Must be within +- 0.03 feet of thickness that will be tested on the job.

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8
Q

In no case will the lift thickness be less than ______ ft.

A

0.10 feet

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9
Q

Each test strip must be at least __________ ft long?

A

At least 600 feet long

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10
Q

How wide must a test strip be?

A

One traffic lane wide

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11
Q

What must be done if a contiguous 600’ can’t be placed?

A

Test strip length may be reduced or combine broken segments to achieve as close to 600 feet as possible.

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12
Q

How many test locations must be used for the test strip?

A

A minimum of 10 test sites.

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13
Q

How are the test locations determined?

A

Test locations are random.

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14
Q

How many cores do you get?

A

A set of two cores.

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15
Q

What size of cores are required?

A

4” to 6” in diameter.

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16
Q

What must be done if any of your cores are damaged during coring?

A

Damaged cores must be discarded and replaced by additional cores from the same site.

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17
Q

What test method is used to determine the core density?

A

CT 308 - Method A

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18
Q

What must the 2 core densities be within in order to be averaged?

A

0.05 g/cc

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19
Q

What must be done with the 2 core densities that are within 0.05 g/cc?

A

Average the 2 densities.

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20
Q

How is the correlation value determined?

A

Subtract the average nuclear density from the average core density for the site.

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21
Q

Test a minimum of 10 sites for each ________ tons of HMA placed.

A

500 tons

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22
Q

For areas containing less than 500 tons, test at the rate of one test site for each _______ tons.

A

50 tons

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23
Q

No test site shall be represented by fewer than _____ test sites.

A

Five test sites

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24
Q

Which table should be used for ten test sites? What table for less than 10 test sites?

A

TABLE 1, TABLE 2

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25
Q

The numbers for transverse location will always be in what order?

A

Random

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26
Q

At what thickness can you use conventional nuke gages?

A

Thickness of 0.20 ft. or more

27
Q

For combinations gages, what mode should be used for thickness of 0.20 ft. or more?

A

Asphalt Mode

28
Q

For lift thickness between 0.10-0.20 ft., what nuke gages should be used?

A

Thin lift gages that don’t use nomographs and combination gages placed in thin lift mode.

29
Q

What sieve size should be used for filling voids?

A

No. 30 sieve

30
Q

Can conventional gages and thin lift gages be used if the combined thickness of a previously tested layer and a newly placed layer is greater than 0.20 ft.?

A

Yes, but layers must be added together

31
Q

Where must the sand come from to be used for filling voids?

A

Sand comes from aggregate mix.

32
Q

If alternate test site must be selected due to surface issues, how do you select the new location?

A

New test site is 10 ft. forward in longitudinal direction, while keeping transverse location.

33
Q

What must be done after sand is No. 30 sieved over test area?

A

Straight edge the surface to smooth out voids and scrape away excess sand.

34
Q

What location must the source rod be placed at on the gage?

A

Place in backscatter mode.

35
Q

What must you do when you have setup your gage before or after your 1 minute count?

A

Mark the base of the nuke gage on the pavement.

36
Q

After your first reading is complete, what is done? And base is marked.

A

Flip gage 180 degrees and place over precise location of initial test.

37
Q

How is the count ratio determined?

A

Dividing nuclear reading by standard count.

38
Q

What decimal must the count ratio be calc’d to?

A

0.001, nearest thousandth

39
Q

How is the density determined?

A

Count ratio-density table is referenced to find density.

40
Q

Density is rounded to what?

A

Nearest 0.01 g/cc

41
Q

What must the 2 density measurements per test site be within what tolerance?

A

Within 0.05 g/cc

42
Q

What must be done if densities are not within 0.05 g/cc?

A

Perform tests until densities are within 0.05 g/cc.

43
Q

What must be done if densities do not come within 0.05 g/cc after 3 retests?

A

Pick different location 10 ft. forward of current test.

44
Q

What is done with the 2 density readings per test site?

A

Average densities and round to nearest 0.01 g/cc

45
Q

What is done with test site readings that have been averaged per site?

A

Average densities and round to nearest 0.01 g/cc

46
Q

How is the corrected in-place density calculated?

A

By adding the conversion factor to the avg in place density.

47
Q

What is TMD?

A

Test Maximum Density

48
Q

What are the two ways to find TMD?

A

LTMD and FTMD

49
Q

What does LTMD stand for?

A

Laboratory Test Max Density

50
Q

What does FTMD?

A

Field Test Max Density

51
Q

When daily production exceeds ______ tons, take additional representative samples from each ______ tons or portion thereof.

A

5,000 tons, 5,000 tons

52
Q

Determine LTMD at least once for the following occurances:

A

Project start-up, Every 5 days or every 25,000 tons placed, whichever first, Change in the HMA or JMF.

53
Q

How often should the LTMD or FTMD be determined?

A

For each daily sample.

54
Q

Testing LTMD or FTMD may be waived for selected daily samples provided all of the following conditions:

A

Five consecutive days of LTMD/FTMD do not differ by more than 1% from their average, at least one LTMD/FTMD is tested every 5 paving days and the results does not differ by more than 1% from the average from the previous 5 days. Untested samples are retained for testing if needed.

55
Q

What Test method is used for getting density of LTMD?

A

CT 308 method A

56
Q

CT 308 Method A rounds to what value for density?

A

Nearest 0.01 g/cc

57
Q

Determine LTMD of the sample by averaging the density values of the ____ individual specimens.

A

5 individual specimens

58
Q

Correlation Factor for FTMD must be determined when?

A

Beginning of a project.

59
Q

What must be done with the sample when determine correlation factor of LTMD and FTMD?

A

Split sample into two representative portions, submit one for LTMD and other for FTMD.

60
Q

How many test specimens of each LTMD and FTMD must be made?

A

5 test specimens of each.

61
Q

How is the Correlation Factor calculated?

A

Divide the average of the LTMD values by the average of the FTMD.

62
Q

How do you calc the relative compaction?

A

RC=(Corrected In-Place Density/TMD) x100

63
Q

Round relative compaction to what?

A

Nearest 0.1%

CT 375 Backscatter (1 decks)

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