<p><p><strong>References:<br></strong><em>Al-Qadi and Appea (2003)<br>Loulizi et al. (1999)</em></p><p><strong>Method Summary </strong></p><p>Ground-Penetrating Radar (GPR) surveys are performed on the test sections to monitor any changes in the pavement systems. An electromagnetic wave is transmitted through the pavement layers using the GPR. The depth of the hidden interface can be calculated by measuring the time of reflection of the wave and known dielectric constant of the medium above the interface. The changes in the amplitude of the reflected signal at the base/subgrade interface can be monitored to determine whether there is contamination or not due to the migration of the fines from the subgrade into the base layer. When the contamination is present, the amplitude of the reflected wave will be low because of the weak contrast between dielectric constant of the base and subgrade material. This indicates the migration of the fines from subgrade soil to base course material.</p><p>GPR passes are periodically taken for the required sections of the pavement. The depth of the hidden interface in the pavement can be obtained measuring the time of reflection of the signal. The changes in amplitude are compared with the initial observed amplitude to determine contamination of the base layer with time.</p><p><strong>Accuracy and Precision</strong></p><p>Pavement thickness data by GPR are accurate as compared with those obtained through conventional core samples within 3-15% error<em>.</em></p><p><strong>Adequacy of Coverage</strong></p><p>The GPR method can evaluate a wide area of a pavement section.</p><p><strong>Implementation Requirements</strong></p><p>The method is quick and cost effective.</p><p><strong>General Comments</strong></p><p>The GPR test is easy to implement, accurate, quick, and cost effective. It is typically used for quality assurance and evaluating completed pavement sections.</p></p>