This instrument complies with the industry standard of the Ministry of Transport "Highway Asphalt and Asphalt Mixture Test Procedure, Asphalt Mixture Theoretical. Large Relative Density Test (Vacuum Method)". The vacuum method is used to determine the theoretical maximum relative density of asphalt mixture at 25°C.

The maximum relative density refers to the ratio of the mass of the test piece per unit volume to the mass of water at the same temperature when the asphalt mixture is compacted to an ideal state without voids. This instrument consists of a frame, vacuum pump, vibrator, regulating valve, vacuum gauge, pressure gauge, and water accumulation device, allowing for parallel tests on two samples simultaneously.