EVALUATION OF DOWEL PLACEMENT USING A DOWEL BAR INSERTER

Abstract

This paper presents the results of several field investigations to evaluate the effectiveness of automatic dowel bar inserter equipment to properly place dowel bars in rigid pavements. Results of three studies using the ground penetrating radar technique to measure dowel bar misalignment are summarized. Two investigations were sponsored by the Demonstration Projects Division of the Federal Highway Administration. The third radar survey was sponsored by the Wisconsin Department of Transportation, Madison, Wisconsin. A commercially available radar system capable of locating steel embedded in concrete was used. The system produces a real time graphic recording and that indicates the horizontal position and relative depth of the embedded steel. Cores were obtained to calibrate the graphic recordings and to obtain the actual embedded depth of the steel bars. In two of the three studies dowel bar alignment using the radar technique was measured along a section where a Guntert and Zimmerman dowel bar inserter was used and where dowels were placed in wire basket assemblies. Overall, the dowel bar inserter performed well compared to the basket assembly construction. Dowel depth, misalignment (vertical and horizontal), and longitudinal displacement are generally comparable.