Methods for Asphalt Road Density Measurement: A Review

Compaction process of the asphalt pavement is to reduce the air voids inside. It is important to monitor the quality of the compaction by density measurement. The thinner the asphalt pavement is, the more challenging the density measurement is. A conventional method for measuring density (i.e., collecting data) is to extract core samples by coring method and then conduct the in-lab tests. This method, so called destructive method, provides the highly accurate density measurements, but need to destroy the compacted pavement. Several Non-destructive (ND) methods for density measurement have also been developed. The term ND method refers to the method measuring density without destroying the pavements. They include nuclear density gauge (NDG), pavement quality indicator (PQI) and ground penetrating radar (GPR) . They are respectively based on the effects of the density on the nuclear (Gamma ray) and electromagnetic signals. A common problem of them is that their measurement results are affected by the factors other than density and they are very hard to be modelled or quantified. This paper is a review of the mentioned methods which are applied in measuring the density of the thin-layer asphalt pavement. Their operational theories, features and accuracies will be discussed respectively.