TD711-2 asphalt mixture maximum theoretical density meter is developed and produced by Cangzhou Tading Hengye Test Instrument Co., LTD. It is suitable for vacuum method to measure the theoretical maximum relative density of asphalt mixture, and can be used for asphalt mixture mix design, road condition investigation or pavement construction quality management to calculate the void ratio and compaction degree. The instrument is not suitable for asphalt mixtures with porous aggregates with water absorption greater than 3%. The instrument is composed of a frame, an imported vacuum pump, a vibrator, an air valve, a vacuum meter, a vacuum container and control appliances, etc. It has a reasonable structure, easy to use, and can carry out parallel tests of two samples at the same time.

Ii. Technical parameters of TD711-2 asphalt mixture maximum theoretical density meter:

Power supply voltage 220V±10% Container volume 4300ml×2 PCS

Pump power 160W pressure range 0-100kpa

Vibrator power 30W External dimension 530×500×360

Test method of TD711-2 asphalt mixture maximum theoretical density meter

It shall be carried out according to T0711-1993 in the Test Code of Asphalt and asphalt Mixture for highway engineering (JTJ052-2000).

1. Take (or drill) asphalt mixture samples from asphalt pavement according to T0701 asphalt mixture sampling method of this regulation. The number of samples shall not be less than the following:

Nominal maximum particle size of aggregate in asphalt mixture (mm) Minimum number of samples (g)

37.5 4000

26.5 2500

19.0 2000

13.2, 16.0, 1500

9.5 1000

4.75 500

2, the asphalt mixture is carefully dispersed, the coarse aggregate is not broken, the fine aggregate is dispersed to less than 6.4mm. If the mixture is hard, the oven can be heated properly after dispersing, the general heating temperature does not exceed 60 DEg C, the dispersed sample should be broken apart by hand, and should not be broken with a hammer to prevent aggregate breakage. When the sample is a non-dry mixture taken from the road, the electric fan should be used to dry it to a constant weight before operation.

3. Type of negative pressure vessel

4, negative pressure container calibration method: B, C type negative pressure container filled with 25 ° C ±0.5 ° C water (with glass plate cover to keep completely filled with water), correctly weigh the total mass of negative pressure container and water (m b).

5. When class A containers are used, all containers are immersed in a constant temperature water tank of 25 ° C ±0.5 ° C, and the water mass (m I) of the containers is weighed.

6. Dry the negative pressure container and number it to take its quality.

7. Put the asphalt mixture sample into a dry negative pressure container, say the total mass of the container and the asphalt mixture, and get the net mass of the sample m a. The mass of the sample should not be less than the minimum quantity specified above.

8. Inject water of about 25℃ into the negative pressure container and soak the mixture completely.

9. Connect the vacuum pump and vacuum gauge in the negative pressure container, start the vacuum pump, so that the vacuum degree reaches 97.3kpa (730mmHg) for 15min±2min.

10. Then strongly oscillate the negative pressure vessel so that the water can fully agitate the mixture and remove the remaining air bubbles. Shake several times every 2 minutes until no bubbles appear. To make the bubbles easy to remove, a surfactant concentration of 0.01% can be added to the water (e.g., 0.01g detergent per 100ml of water).

11. When the negative pressure vessel adopts class A vessel, immerse into the constant temperature water tank insulated to 25 ° C ±0.5 ° C, and after about 10min, weigh the water mass (m2) between the negative pressure vessel and the asphalt mixture. When class B and C containers are used as negative pressure containers, immerse the container containing the asphalt mixture sample into a constant temperature water tank insulated to 25℃±0.5℃, take it out after about 10min, add a cover, so that there is no air in the container, wipe the water outside the container, and weigh the total mass (mc) of the asphalt mixture sample of the container and water.

Iv. Usage method of TD711-2 asphalt mixture maximum theoretical density meter

1. The method of using the instrument is to put the number of samples in the negative pressure container according to the test specifications, and then add 25℃ water to soak the mixture completely, but the water should not be too much, so as not to inhale the pump.

2, put the negative pressure vessel in the instrument platform positioning ring, cover on the cover, and pressure on the pressure bar, then close bleed valve, open air switch, make the negative pressure of 97.3 kpa, switch off extraction pressure after 15 minutes, and open vibration switch, there are two kinds of vibration mode optional, is a continuous vibration, a continuous vibration, the vibration 1 minute. Stop the cycle for 2 minutes until there are no bubbles in the water.

V. Calculation of the results of TD711-2 asphalt mixture maximum theoretical density meter

1. When class A containers are used, the theoretical maximum relative density of asphalt mixture is calculated according to Equation (1).

rt = where rt -- theoretical maximum relative density of asphalt mixture:

ma -- air mass of dry asphalt mixture sample, g;

m1 -- mass of water in negative pressure vessel at 25℃, g;

m2 - mass of negative pressure vessel and asphalt mixture in water at 25℃, g;

2. When class B and C containers are used as negative pressure containers, the maximum relative density of asphalt mixture is calculated according to Equation (2).

rt = where: mb -- the total mass of the negative pressure vessel filled with water at 25℃, g;

mc -- Total mass of sample, water and negative pressure vessel at 25℃, g;

3. The theoretical maximum density of asphalt mixture at 25℃ is calculated according to Equation (3).

Rho t = rt * rho w

ρr -- theoretical maximum density of asphalt mixture, g/cm3

ρw -- density of water at 25℃, 0.9971g/cm3

The average value of the same sample tested in parallel at least twice is taken as the test result and calculated to three decimal places.

Vi. Precautions for TD711-2 asphalt mixture Maximum Theoretical density meter:

1, the instrument should be determined before the use of power supply voltage 220V±10%, and have a good grounding device.

2. After the sample is put into the negative pressure container, the highest water level shall be lower than 3cm below the barrel mouth. To waterproof suction pump caused damage.

3. If there is no pressure indication on the pressure gauge after opening the pump, shut down and start the pump after finding out the reason.

4, vacuum pump is a precision part of the instrument, without the manufacturer's permission is prohibited to disassemble, disassembly will lose its shelf life. The warranty period of normal use is one year from the date of purchase and lifelong maintenance