3D localization of the reinforcement in reinforced concrete slab by using GPR
Résumé
GPR is an inspection technique characterized by a high speed of implementation. It is well adapted for the assessment of reinforced concrete structures. One of the main applications is for the 3D localization of reinforcement. Nevertheless for achieving a good accuracy, the localization in depth needs post processing which requires a good level of expertise. The objective of this work is to propose a novel measurement procedure and an adapted post processing for 3D localization of the first layer of steel reinforcement in reinforced concrete and for water content assessment of cover concrete. This methodology can be fully done without any processing expertise. The measurements are done using two GPR antennas with a central frequency of 1.5 GHz, in a bi-static configuration. Both antennas are disposed in a single box equipped with an encoding wheel. The transmitter (T1)-receivers (R1) and (R2) distances are constants, such as (T1)-(R1) is 5.9 cm and (T1)-(R2) is 11.9 cm. We developed an original algorithm to analyse and process recorded radar signals which provides the position in the plane and depth of the first layer of reinforcement in slabs and walls. This algorithm also allows calculating the velocity of electromagnetic waves in concrete that will be used to quantify the water content. This communication aims to present the performance of this algorithm. The results show that it enables the localization of the reinforcement in depth with an error lower than 4%. Measurement processing is very fast and does not require any knowledge neither of the material nor of the geometry.