Application of GPR to map concrete to delineate embedded structural elements and defects

Abstract

Concrete inspection is a well-known use of GPR. The advent of modem GPR instruments combined with vastly increasing computing power and rapidly improving software permits more effective use of GPR. The impediment to wider use is now the ease-of-use of GPR technology for the average commercial user. The requirements for concrete inspection are many and varied. The most common is to clear areas prior to cutting and coring for the installation of utilities or renovations. The requirement is a quick means of knowing how to avoid critical elements such as posttension cables or embedded utilities. Structural applications address the integrity of the concrete itself such as the presence of voids/air pockets, chemical alteration, or cracking. Owing to the less well defined and site specific character of such features, GPR applicability is unpredictable and interpretation of results still depends on gaining experience with the specific site conditions. Intrusive investigation must augment GPR findings to draw definitive conclusions. The embedded object class of problems is readily tractable with GPR. In the last year we focused on development of a system which enables non-GPR specialists to image concrete. The system required integration of a GPR sensor with a positioning procedure and on site data processing in a single package. The output is depth slice maps that allow the operator to immediately select cutting and coring locations. Systematic ergonomic procedures to make operation easy for average concrete users represented a major challenge. In this paper we discuss the design considerations and present the final system embodiment. We use a number of data examples from real environments to illustrate the development.