A Method for Cavity Scale Estimation Based on Ground-Penetrating Radar (GPR) Explorations: An Experimental Study

Table 2

Dielectric values of the typical pavement soil and layer constituents.

Constituent	Dielectric value
Air	1
Freshwater	8
Ice	4
Bedrock (granite)	5–7
Clay	25–40
Silt	16–30
Silty sand	7–10
Sand subbase	4–6
Gravel base	4–7
Glacial till	8–18
Asphalt concrete	4–8
Slag asphalt concrete	8–15
Portland cement concrete	8–10
Bitumen bound base	6–7
Cement bound base	8–10