The measurement of asphalt concrete compaction density is an essential measure, whether for the quality control of the new pavement or for the evaluation of the existing pavement. If the compaction density is too high or too low, the pavement may fail, resulting in huge maintenance costs.

Compaction density is closely related to void ratio. Void ratio is the volume percentage of void in asphalt concrete. The ratio of the compacted density of the measured sample to the theoretical maximum density (void ratio is zero) is obtained. In order to obtain the best performance of the pavement, the void ratio should be 3% - 8% for the dense pavement. Over compacted pavement with voids less than 3% may cause rutting. However, for the uncompacted pavement, the void ratio is more than 8%, which may cause water and air to enter into the pavement, causing pavement cracks and looseness. Therefore, the field compaction density or voidage measurement is not only a frequent measurement for the quality control of the new pavement, but also for the old pavement to estimate the pavement life.

Generally, there are two methods to measure the road compaction density: 1. Take the core on site, and then measure the compaction density in the laboratory; 2. Measure the compaction density with portable nuclear densitometer. Recently, electromagnetic densitometer has also been introduced as an alternative instrument of nuclear densitometer to measure the field compaction density. Although the nuclear densitometer and electromagnetic densitometer are non-destructive measurements, they need to be calibrated with the compaction density measured in the laboratory after on-site coring.

Compared with the electromagnetic densitometer, the nuclear densitometer uses radioisotopes in two kinds of portable measuring instruments, which is potentially harmful to users. However, the measurement results of electromagnetic densitometer are interfered by many environmental factors (for example, the recently proposed conductive asphalt concrete can heat melted snow without using sand salt, which is conducive to environmental protection. However, due to the interference of the electromagnetic densitometer's compaction density measurement results due to the addition of conductive materials in the asphalt concrete, the frequent use of field core samples for calibration may be an essential means to ensure the measurement results of the electromagnetic densitometer.

After on-site coring, the laboratory measures the compaction density, which requires the core sample of asphalt concrete to be sent to the laboratory for measurement. The measurement data usually takes 24 hours to get. The timeliness of measurement is often a problem. In addition, it is necessary to mark each asphalt core sample and record the coring section, which is cumbersome and error prone.

The portable on-site asphalt concrete compaction density measuring instrument adopts the patented technology to measure the asphalt core samples after on-site coring in real time. The measurement results can not only accurately get the compaction density and porosity of the field pavement, but also realize the frequent calibration of the portable densitometer to ensure its measurement accuracy and accuracy.