Reliability and limitations of GPR for identifying objects embedded in concrete – Experience from the lab

This paper presents laboratory application of the Ground Penetrating Radar technique on six concrete specimens, with intentionally embedded objects made of different materials, in an effort to demonstrate the capabilities of the radar technique and to assist practitioners in using this technique in real applications. Conclusions are drawn on the effectiveness in identifying objects including rebars and (dense) mesh, polyethylene, steel and plastic tubes, steel sheets, wood and brick. The impact of data acquisition parameters is discussed and practical guidance is given for high-quality scans and data interpretation. It is concluded that cross-polarized antennas are an efficient way for the detection and identification of different rebar diameters. The signal penetrability is reduced for moist concrete; however, by suitable signal modification, the raw data quality can be considerably enhanced. The use of the technique for the investigation of laboratory concrete specimens with known content allows for the understanding of the limits of the technique.