Safety Edge Demonstration Project – Menominee County, Wisconsin
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SUMMARY OF OBSERVATIONS
This section of the field report provides a summary and listing of important observations made during the paving operations, interview with paving personnel and findings from the field measurements taken during paving that are expected to have a significant impact on the performance of the Safety EdgeSM and non-Safety EdgeSM portions of this project.
- The TransTech Shoulder Wedge Maker and two Carlson devices (Prototype #2 and Prototype #3) were demonstrated on this project. The Carlson prototype #1 was not part of this project. Only the TransTech and Carlson prototype #2 devices were observed during paving. The Carlson prototype #3 was implemented on this project after the site visit. All three devices had varying degrees of success. The TransTech device was bolted to the screed while the Carlson devices were part of the end gate. The Carlson devices were mounted to the lower edge of the end gate and utilized the length of the end gate to apply compaction to the slope face of the Safety EdgeSM. This approach provided adequate elevation control of the Safety EdgeSM and had the benefit of sealing the slope face and producing a smooth appearance which may extend the life of the edge by slowing water infiltration at the edge. None of the devices had a negative impact on the paving operations nevertheless, the following bulleted items call attention to remaining issues.
- The average slope of the Safety EdgeSM was 35°, 33°, and 36° for the TransTech, Carlson Prototype #2 and Prototype #3 respectively. The shape of the slopes were relatively consistent in the observed test sections but in all cases the slopes were higher than the targeted 30°.
- The Carlson’s end gate devices proved to be the least intrusive on the paving crew in that the screed operator's typical end adjustments automatically controlled the edge.
- The TransTech device, on the other hand, required periodic vertical adjustment made from the screed operator by hand in addition to the operators typical adjustments.
- The HMA mix density was slightly higher and the air voids slightly lower adjacent to the edge of the mat for the non-Safety EdgeSM section in comparison to the Safety EdgeSM sections. This result is contrary to other projects where the Safety EdgeSM sections had slightly higher in-place density or similar density when compared to the non-Safety EdgeSM section. The reasons for this result are not known as the roller patterns employed on this project were the same on the Safety EdgeSM and non-Safety EdgeSM sections.
- The aggregate shoulder width on this project varied from 1 to 4 ft and plans called for an additional 1.5 inches of new granular material to be placed on the shoulder to level the grade flush with the pavement surface. New granular shoulder material was not placed during the site visit so direct observations could not be made.
- No problems were observed or expected regarding the shoulder and the Safety EdgeSM as the new HMA overlay, including the Safety EdgeSM, was placed over the existing HMA pavement.
- Segregation was not observed on this project, either at the longitudinal joint or at the edge.
- In the areas inspected, the Safety Safety EdgeSM covered the edge of the existing pavement preventing a true measurement of the mat thickness at the Safety Safety EdgeSM.
This project presents the opportunity to evaluate the long term performance in terms of maintenance efforts and life cycle costs of the Safety EdgeSM placed by different types of devices.