Operation instructions for asphalt penetration tester

Asphalt penetration tester is a specialized instrument for measuring the viscosity of asphalt, suitable for measuring the penetration of road petroleum asphalt, modified asphalt and other materials, in order to determine the softness and cohesiveness of asphalt. The operation must strictly follow the standard specifications (such as the "Test Regulations for Asphalt and Asphalt Mixtures in Highway Engineering", the specific steps are as follows:

1、 Preparation before the experiment

Sample preparation

Heat the asphalt sample to a molten state (heating temperature not exceeding 90 ℃ above the softening point of the sample, and heating time not exceeding 30 minutes), and continuously stir until there are no bubbles or impurities.

Pour the molten asphalt into a clean and dry sample dish:

For samples with a penetration of less than 200, the depth of the sample dish should not be less than 35mm;

For samples with a penetration degree greater than or equal to 200, the depth of the sample dish shall not be less than 50mm.

The height of the poured asphalt should be about 10mm higher than the expected penetration value, and it should be cooled at room temperature for more than 1.5 hours. If the sample belongs to modified asphalt or special asphalt, the cooling time should be appropriately extended.

Place the cooled sample dish in a constant temperature water bath at the specified temperature for insulation: the standard test temperature is 25 ℃, and the insulation time is not less than 1.5 hours; if the test temperature is other temperatures (such as 0 ℃, 5 ℃, 45 ℃), the insulation time needs to be adjusted to more than 2 hours.

Instrument inspection and calibration

Check whether the needle connecting rod of the penetration tester is flexible, without shaking or jamming; Check whether the standard needle is clean, free from bending, and the needle tip is undamaged. If the needle tip is worn, it should be replaced in a timely manner.

Calibrate the displacement measurement system and time control device of the instrument: ensure accurate timing when the time is set to 5s, 15s, and 30s; The displacement reading error shall not exceed 0.1mm.

Adjust the temperature of the constant temperature water bath: stabilize the water temperature at the specified test temperature (deviation not exceeding ± 0.1 ℃), and ensure that the water bath can immerse the sample dish, and the distance between the water surface and the sample surface is not less than 10mm.

Equipment preparation

Prepare standard needles, weights (usually 100g, including the weight of the needle connecting rod, and the total load can be adjusted to 50g or 200g according to the test requirements), sample dishes, constant temperature water baths, thermometers, etc.

2、 Instrument operation steps

Place the sample

Take out the insulated sample dish from the constant temperature water bath and quickly place it on the testing platform of the penetrometer. Adjust the platform position so that the center of the sample dish is aligned directly below the standard needle.

Cover the instrument with a thermal insulation cover to prevent temperature fluctuations in the sample during the testing process.

Adjust the position of the needle

Loosen the fixing screw of the needle connecting rod and slowly lower the needle connecting rod so that the tip of the standard needle just touches the surface of the asphalt sample. Judgment method: It can be observed manually or through the optical projection device of the instrument. When the needle tip comes into contact with the surface of the sample, stop lowering it.

Lock the needle connecting rod and reset the reading of the displacement measuring device to zero.

Set experimental parameters

Set the load and time according to the experimental requirements:

Standard test conditions: load 100g, time 5s;

Other test conditions can be adjusted according to the specifications for load (50g or 200g) and time (15s or 30s).

Confirm that the time controller is in a pending trigger state.

Start the test

Press the "start" button of the instrument, and the fixing device of the needle connecting rod will automatically release. The standard needle will vertically pierce the asphalt sample under the load.

When the set time is reached, the instrument will automatically lock the needle linkage and stop piercing.

Read data

Read the value of the displacement measuring device, which is the penetration value of the asphalt sample (unit: 0.1mm).

The same sample needs to undergo at least 3 parallel tests, and the distance between the needle points for each test should not be less than 10mm, and the distance from the edge of the sample dish should not be less than 10mm to avoid the impact of the previous needle on the subsequent test.

3、 Post experimental processing

Instrument cleaning

After the experiment is completed, remove the needle connecting rod, clean the residual asphalt on the standard needle with organic solvent (such as trichloroethylene), dry it, and store it properly.

Clean the sample dish. If the sample needs to be recycled, it can be heated and melted before collection; If there is no need for recycling, dispose of it according to the laboratory waste disposal regulations.

Data calculation and recording

Calculate the average penetration of 3 parallel experiments, with the result rounded to one decimal place.

When the difference between the maximum and minimum values of the three test results exceeds the allowable deviation, the test needs to be repeated.

Record test conditions: temperature, load, time, sample name and number, etc.

4、 Precautions

The entire experimental process must ensure the stability of the sample temperature, and the time from the sample being taken out of the water bath to the completion of the experiment should not exceed 10 seconds.

Standard needles are precision components that should be avoided from collision and bending during use, and the sharpness of the needle tip should be calibrated regularly.

The water level of the constant temperature water bath should be kept stable to prevent temperature fluctuations in the sample due to low water level.

Gloves should be worn during operation to avoid hand temperature affecting the sample and to prevent burns from high-temperature asphalt.