Using Ground Penetrating Radars to Detect Cold Joints in Reinforced Concrete Structures

Abstract

This research project aims to solve potential problems that may accompany the inspection of a foundation, to increase awareness about ground-penetrating radar surveys and their methods that can help to enhance processes in the inspection process. For the detection of internal defects, a method of ground penetration radar surveying was used, performed using a regular mesh of orthogonal projections over an easily accessible surface area of the slabs and several antennas producing sounding signals with frequencies varying within the range of 1,500 and 2,000 MHz. The results of several field studies were analysed and summarized. Some internal defects have been detected in the structures, including horizontal cold joints, cavity pockets and honeycombs. Their presence was later confirmed by control drilling and core material sampling. The information thus obtained was later generalized and created surface maps of cold joints that depicted both the relief and the layout of detected defects in space. The core analysis has proven that the reflecting boundaries are the same as those of the core material destruction; it has also demonstrated the presence of air bubbles and the proofs of poor-quality concrete mix compaction. As a result of the research, it can be established that the use of GPR allows one to effectively detect the presence of cold joints in concreting caused by significant pauses in concreting structures.