Road pavement density evaluation—a case study

A comprehensive evaluation of different pavement density measurement methods was performed on a new highway section in southeastern Finland. A conventional Ground Penetrating Radar (GPR) and a new 12–18 GHz microwave radar provided the Nondestructive Testing (NTD) Data. Drill core samples were analyzed in the laboratory with a 7–17 GHz microwave scanner and by standardized physical methods. Pavement layers were measured after each lift of construction with the microwave radar. After the final surface layer was constructed, the pavement was measured with the GPR. Data spread, both within and between methods, does not support the assumption that a sufficiently accurate density and air void content estimations, equivalent to the physical measurements, could be derived simply by correlating average effective permittivities and physical measurements. Based on the ambiguity of the results a new statistically based approach is needed to assess the quality of asphalt pavement layers with radar.