Date of this Version
Report SPR-P1 (08) P307 Final Report 26-1118-0085-001
Extracting concrete cores is the most common method for measuring the thickness of concrete pavement for construction quality control. Although this method provides a relatively accurate thickness measurement, it is destructive, labor intensive, and time consuming. Moreover, concrete cores are usually taken approximately every 750 ft, which may be inadequate for estimating the actual thickness profile of a pavement section; however extracting more cores would damage the pavement extensively and increase the labor cost and time excessively. Ground Penetrating Radar (GPR) is a well-established technique for subsurface exploration. Recently, GPR has been used for several transportation applications, such as measuring layer thickness in asphalt pavement, locating reinforcing bars and tendons, and detecting deteriorations and anomalies in concrete structures. The main advantages of GPR are speed, accuracy, and cost-effectiveness when scans are conducted on large areas. The objective of this project is to investigate the accuracy and cost-effectiveness of using GPR for measuring the thickness of concrete pavement for quality assurance purposes. The GPR systems GSSI SIR20 and SIR3000 with a high resolution 1.6 MHz ground coupled antenna were used in measuring the thickness of concrete pavement up to 14 in. thick. Several laboratory and field tests were carried out to determine the accuracy of the GPR measurement at different concrete ages and when various metal artifacts are used underneath the concrete to improve the reflectivity of the bottom surface. Testing results indicated that GPR is cost-effective nondestructive technique for measuring the thickness of concrete pavement, compared to core extraction, and an accuracy of 1/8 in. can be achieved when appropriate reflectors and calibration cores are used.