LRRB Local Operational Research Assistance Program (OPERA) for Local Transportation Groups Field Report

Transcription

1 LRRB Local Operational Research Assistance Program (OPERA) for Local Transportation Groups Field Report This report must include the underlined subject areas and supporting resources (i.e. photos, graphs, charts, etc.). The OPERA program will use this information in an annual report that will be shared with other local agencies within the state. We request that a short 5-10 minute demo or presentation be shared at the Spring Maintenance Training Expo, MN Fall Maintenance Expo or with a professional organization. Date: September 21, 2015 Project Title: Ultra-thin Bonded Wearing Course (UTBWC) over Micro Milling Test Section Project Number: Agency: McLeod County Highway Department Person Completing Report: John Brunkhorst, McLeod County Engineer Project Leader: Phone Number: John Brunkhorst john.brunkhorst@co.mcleod.mn.us Problem: A portion of McLeod County State Aid Highway 115 (South Grade Road near Hutchinson) exhibited a marginal improvement in ride after it was micro milled in In order to preserve the surface of the road, a surface treatment was needed to be done on it. Solution: McLeod County elected to surface CSAH 115 with a 5/8 thick ultra-thin bonded bituminous wearing course (UTBWC) in lieu of a traditional seal coat because the UTBWC should last longer, improve some surface distresses, and most importantly improve the ride. Background on UTBWC: Ultra-Thin Bonded Wearing Courses consist of a thin ( to 0.75-in. thick) gap-graded, polymer-modified hot mix asphalt (HMA) layer placed on a polymer-modified emulsified asphalt membrane. This material was originally developed in France in 1986 and introduced in the United States in the early 1990s as the proprietary product NovaChip. An ultra-thin bonded wearing course is typically applied as a preventive maintenance or minor rehabilitation treatment for the purpose of sealing the surface, correcting surface distresses (e.g., raveling, block cracking), or restoring key surface characteristics, such as friction,

2 smoothness, and transverse profile. The polymer-modified HMA layer uses crushed aggregate chips sized 0.25 to 0.5-in. with binder contents in the range of 4.5 to 5.5 percent. Similar to HMA, an ultra-thin bonded wearing course is easily produced at a HMA facility. The main difference in placement is the use of a specialized paver, which is capable of applying the asphalt membrane and the polymer-modified HMA surfacing in a single pass. Once placed, the material is lightly rolled to orient and seat the aggregate chips. A UTBWC was performed in Minnesota on US-169 near Princeton in 1999 and The UTBWC was placed over a traditional HMA mat, the mat was crack sealed prior to the UTBWC application. According to a 2007 MnDOT Research Report ( ); the application was showing excellent results after 7 years. To the best of our knowledge, the application of the 5/8 UTBWC on McLeod County State Aid Highway 115 was the first one performed over a micro milled surface on a Minnesota County Highway. Testing Procedure: 1. Take pavement smoothness measurements of CSAH 115 at various stages to determine the International Roughness Index (IRI), which is the current MnDOT standard measurement of pavement smoothness. An Ames high speed inertial profiler will be utilized for the tests. Testing will be taken at the following stages: a. Prior to micro milling b. After micro milling/before UTBWC c. After the UTBWC Project Timeline: September 8, 2014 IRI measurements were taken prior to micro milling September 8, 2014 CSAH 115 was micro milled July 31, 2015 IRI measurements were taken August 28, 2015 UTBWC was placed September 21, 2015 IRI measurements were taken Results: The UTBWC application provided a 57% improvement in ride in the eastbound lane. The UTBWC application provided a 60% improvement in ride in the westbound lane. Overall we believe the UTBWC provided a marked improvement in ride. We noticed that the UTBWC provides a very quiet ride. In a rain event the UTBWC sheds water very well. See next page for IRI data breakdown and graphs.

3 IRI PAVEMENT SMOOTHNESS DATA Eastbound Lane CSAH 115

4 Westbound Lane CSAH 115

5 PHOTOS Micro milling - 9/8/14

6 PHOTOS Ultra Thin Bonded Wearing Course (UTBWC) BEFORE - 8/26/15

7 PHOTOS Ultra Thin Bonded Wearing Course (UTBWC) Placement - 8/28/15

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10 Implementation: The UTBWC cost was $5.20/SY. The cost of a bituminous seal coat utilizing granite and a fog seal is approximately $1.50/SY. The cost of a typical 1.5 hot mix overlay is approximately $7.00/SY. Although the cost of the UTBWC is higher than a sealcoat; we believe that it is a good pavement management tool to consider due to its ability to improve ride, provide a quiet driving surface, and hold down reflective cracking due to the high polymer modified oil content. Acknowledgements: Special thanks to Greg Schneider and staff in the MnDOT Bituminous Office for providing the smoothness testing and results. Status: Complete Total Duration of Project: 1 month Project End Date: September 25, 2015 Approximate Cost of Entire Project: $85,000 Total OPERA Funds used for project: $10,000 Send and a completed report with pictures to: Mindy Carlson, CTS TSB, 511 Washington Ave. SE, Mpls. MN 55455, carlson@umn.edu. For questions about this report please contact Mindy Carlson at