Asphalt pavement compaction is a crucial indicator for evaluating pavement construction quality and performance, directly impacting pavement strength, durability, and resistance to water damage. While traditional core drilling methods are accurate, they are destructive and inefficient. With advancements in testing technology, nuclear-free density gauges (Nuclear-Free Density Gauges) are widely used for rapid on-site testing.

1. Scope of Application

This method is applicable to the rapid density testing of asphalt mixtures in each structural layer of asphalt pavement laid on the same day but not yet open to traffic, using a nucleus-free density meter, and to calculate the compaction degree.

⚠ The test results are primarily used for construction quality control and are not recommended as the sole basis for final acceptance.

2. Technical requirements for instruments and materials

The nucleus-free density meter should contain an electronic module and a rechargeable battery. The probe should be nucleus-free and capacitor-free. The technical requirements for the nucleus-free density meter are as follows:

(1) Maximum detection depth: ≥10cm.

(2) Minimum detection depth: ≤2.5cm.

(3) Single measurement time: not greater than 5s.

(4) Accuracy: 0.003g/cm³.

(5) Equipped with a standard density block for self-calibration of the nucleus-free density meter.

Reference standards:

ASTM D2950 — Asphalt Pavement Density by Non-Nuclear Method

EN 12697-10 / EN 12697-6 — Density and void content of asphalt mixtures

AASHTO T343 — Non-nuclear density gauge method

3. Methods and Procedures

3.1 Preparation

(1) Before first use, the software initialization settings should be completed and the parameters saved to avoid repeated configuration.

(2) Before use, calibration must be performed using a standard density block, and the correlation with the core drilling results must be verified to ensure the reliability of the test.

3.2 Test Procedures

1. Select the test location according to relevant specifications. The distance from the road edge or any structure shall not be less than 30 cm, and the surface shall be kept dry.

2. Place the non-nuclear density gauge steadily on the test point, ensuring no movement or vibration. If the pavement surface is uneven, fine sand may be used to level the test area.

3. Turn on the device and check the battery level, internal temperature, and test parameter settings (time, sample ID, etc.).

4. Set pavement parameters, including layer thickness and maximum nominal aggregate size, and select single-point testing mode.

5. Press the test button. After approximately 3 seconds, read and record the data. If the surface moisture value is greater than 10, the data shall be considered invalid and a new test location shall be selected.

6. Calculate the actual density using the correction value or correlation formula (accuracy: 0.01 g/cm³).

4. Data Processing

Compaction degree is calculated using the following formula: K = ρd / ρ0 × 100

Where:

K — Compaction degree (%)

ρd — Measured density (g/cm³)

ρ0 — Standard density (determined according to JTGF40 or EN 13108)

Relevant Standards:

JTG F40-2004 — Technical Specification for Construction of Asphalt Pavement

EN 13108 — Asphalt mixture specifications

ASTM D2041 — Theoretical maximum specific gravity

5. Core Drilling Correlation Test (Calibration Method)

5.1 Road Section Selection

Test section length ≥ 200 m

Number of measuring points: no less than 10–15 (determined based on structural consistency)

5.2 Test Procedure

Perform multi-point testing using the five-point method (e.g., T0925 method)

Measure density, humidity, and temperature using a coreless density meter

Drill core samples from the same locations and determine the true density using the core method.

Reference Standards:

ASTM D2726 — Bulk Specific Gravity of Compacted Asphalt Mixtures

EN 12697-27 — Sampling of asphalt mixtures

5.3 Data Processing

Calculate the deviation Δρ between the coreless method and the core drilling method.

Derive the correction coefficient or correlation regression formula.

The model can only be used if the correlation coefficient R ≥ 0.90.

6. Report

This method shall include the following technical information in the test report:

1. Test point location (chainage, pavement layer, etc.).

2. Measured density, standard density, and compaction degree.

3. Average value, standard deviation, coefficient of variation, and representative value of the compaction degree for the test section.

4. If correlation testing is conducted, the correction value or correlation equation, as well as the correlation coefficient, shall also be reported.