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Sampling Asphalt Mixtures and Density Testing References

504.03.11 Mix Sampling & Testing. Mix sampling and testing for Quality Control (QC) is the responsibility of the Producer or Contractor. Identify the QC sampling locations in the Field QC Plan (plant or project site). Perform Quality Assurance (QA) sampling as directed and witnessed by the Administration. Obtain QA samples from behind the paver prior to compaction. The Administration will perform all QA testing.

(a) QC Sampling at the Plant. Refer to MSMT 457. The Engineer will retain all random sampling documentation. The producer shall sample the mix at the plant. The sample shall be obtained or witnessed by the certified technician. QC plant mix sample results shall not be used in the pay factor calculation. Submit the results to the Administration and identify as Plant samples.

(b) QC Sampling at the Project Site. Refer to MSMT 457. QC and QA samples shall not be split samples. The certified technician shall sample the mix at the project site. Sampling will be witnessed by the Administration.

1. A mix lot constitutes all sublots of a mix created during the production of required tonnage for a lot.
2. A mix sublot size should not exceed 1,000 tons.
3. A sublot size up to 200 tons can be combined with the previous 1,000 ton sublot placed on the same day.
4. A new lot number for a mix will be given when there is a change in the approved job mix formula.
5. QC project site mix sample results may be used in the pay factor calculation.

The specifications state that up to 1,200 tons of asphalt mix can be represented by one asphalt mixture box sample.

The April 6, 2018 Construction Directive 07720.500.04 states:

5) Sampling & Testing for Density Determination
a) Asphalt Paving – Mixture Sampling

1. Quantities of 200 tons or less of asphalt production will not require random field mix samples unless otherwise directed by the Engineer.
2. Random field mix samples must be taken from behind the paver and must not be taken from areas of bridge approaches, entrances, gore areas, handwork, Gradall placed material, paver hoppers and ends of paver augers.
3. Daily quantities greater than 200 tons may be considered small tonnage if accumulated through non-continuous paving. For example, bridge approaches, widening areas, turn lanes, entrances, gore areas. This information must be detailed on the OOC-90 QA Project Report – Mixture/Density Samples.

c) Asphalt Patching – Mixture Sampling

1. Quantities of 200 tons or less of asphalt may not require daily field mix samples. However, one random sample per mix will be required for every 1,000 tons of asphalt or one sample per mix for every five days of patching, whichever yields the greater frequency.
2. Patches not placed with a paver or patches less than 1,000 sq. ft. (10′ wide x 100′ long) will not require a mix sample. This information must be detailed on the OOC-90 QA Project Report – Mixture/Density Samples.

504.03.12 Sampling & Testing for Density Determination .

(d) Acceptance. Each asphalt density lot will be evaluated for compliance using the Engineer’s quality assurance test data and the Contractor’s QC data. The QC and QA core specific gravity data will be analyzed in conformance with MSMT 733 (F-test and t-test method).

1. If test results are determined to be from the same population, QC and QA sublot results will be averaged to calculate the density pay factor in accordance with 504.04.02.
2. If results are determined not to be from the same population, the pay factor will be calculated using QA sublot results only. The average QC maximum specific gravity test results and the average project site behind the paver QA maximum specific gravity test results shall be compared.
3. If QC results and QA results compare within 0.026, the average of the combined QC and QA results shall be used to calculate each core density. If they do not compare within 0.026, QA maximum specific gravity results shall be used to determine each core density.
4. Pay reduction or incentive for the pavement compaction lot will be calculated in conformance with 504.04.02. Statistical outliers will be determined according to MSMT 734.
5. An asphalt density lot size shall equal one paving day’s production per mix. A lot shall be divided into a minimum of five equal sublots. A sublot shall not be greater than 500 tons. When a paving day’s production per mix is greater than 2,500 tons, then each sublot size shall be 500 tons or fraction thereof

Acceptance on projects requiring less than 500 tons of asphalt or when asphalt is used in non-traffic areas or on bridge decks will be determined with a thin layer density gauge used according to the manufacturer’s recommendations. This information must be detailed on the OOC-90 QA Project Report – Mixture/Density Samples.

504.03.13 Thin Lifts and Wedge/Level Courses. If an asphalt course is determined to be a thin lift in accordance with the “Thin Lift Mix Design Identification Table” in 904.04.07, construct a 400 ft to 500 ft control strip on the first day of paving to determine optimum pavement density.

1. Use a thin-lift nuclear or non-nuclear asphalt density gauge in accordance with the manufacturer’s recommendations to take readings from the control strip in five random locations to determine roller patterns and the number of passes needed to obtain optimum density. Optimum density is defined as when the average density does not change by more than 1.0 percent between successive roller passes and the percent density is between 90.0 and 97.0.
2. Core the 5 random gauge reading locations to verify the gauge calibration and to determine the percent pavement density. The cores will be tested by the contractor’s QC laboratory and results will be verified by the Office of Materials Technology. The QC/QA cores will be saved by the contractor and made available to the Administration for retesting 10 days past after the paving date or as directed.
3. On the first day of paving, the target optimum density will be determined using the density gauge readings from the control strip; verified by the core results. The lot average density from the five control strip cores will be used as the target optimum density.
4. Take a minimum of 10 QC/QA gauge readings daily from random locations per day’s paving per mix or 2 per 500 tons of paving per mix; whichever yields the higher frequency of locations. A density lot is defined as a day’s paving per mix. A sublot shall not exceed 500 tons. A paving day shall begin with a new lot and sublots.
5. Any lot average 2.0 percent or more below optimum and below 92 percent shall require a new control strip to be constructed, tested and approved before paving continues.
6. Take 2 QA cores daily when production is in excess of 500 tons per location, or when successive days of less than 500 tons production totals 1000 tons or greater. If the average of the 2 density gauge readings and the average of the two respective QA core densities are within 3.0 lb/ft3, the Administration will accept all the daily density gauge readings. If they do not compare within 3.0 lb/ft3, construct a new control strip and recalibrate the density gauge.
7. Wedge/Level courses placed at variable thicknesses and any area greater than 3/4 in. shall be tested and accepted in accordance with this Thin Lift specification. Density incentives are not applicable for Thin Lift or Wedge/Level Courses. Apply mix pay factors as determined by the Engineer and the Contractor at the Pre-pave meeting.

904.04.07 Thin Lifts. As specified in 504.03.13. Lift thicknesses shall be designated as thin lifts when the lift thickness specified does not meet 3-times nominal maximum aggregate size for fine graded mix designs or 4-times nominal maximum aggregate size for coarse graded mix designs. Determine fine and coarse graded thin lift mix designs per M 323 and in accordance with the table below:

Gradation Classification Control Sieve Mix Design Target (%Passing)

The April 6, 2018 Construction Directive 07720.500.04 states:

5) Sampling and Testing of Small Quantities of Asphalt Materials

d) Asphalt Patching – Cores

1. A calibrated density gauge will be used.
2. A minimum of one test per lift of asphalt will be required and the results recorded for the project records.
3. Three cores per 1,000 tons ( or portion thereof) per mix will be used to validate the density gauge for quality control purposes as per 505.03.14.
4. Core sheets must be submitted daily for all production including low tonnage.

Take three cores and corresponding gauge readings on the first day and per mix weekly to verify the gauge readings. If the average of the density gauge readings and the average of the core densities are within 3.0 lb/ft 3 , all the daily density gauge readings will be accepted. If they do not compare, recalibrate the density gauge. Incentives are not applicable for patch density.

Tack Coat Samples

In accordance with AASHTO R66 and the Administration’s Sample Testing and Frequency Guide:

A one-gallon tack sample shall be taken from the distributor and placed in a wide-mouth plastic jug on the first day of surface paving.

• The plastic jug must be labeled on the side of the jug with the contract information, product information and date sampled.
• A material certificate of analysis must be included with the sample and a completed Form 88.

Important Reference Sites :

• Material Quality Assurance Processes, Details and Frequencies
• Material Quality Assurance Process – Asphalt Technology Division

• OMT Form 88 – General materials sample
• OOC 90 – QA Project Report – Mixture / Density Samples