High Performance Concrete Pavements
Project Summary

CHAPTER 23. MINNESOTA 3 (Mn/Road, Mainline Road Facility, and US 169, Albertville)

Introduction

This study included two projects: three test sections on US 169 in Elk River and six test sections on I-94, at the Minnesota Road Research (Mn/Road) test facility (see Figure 67).

Figure 67. Location of MN 3 project.

The US 169 site represents a typical application for ultrathin whitetopping. Most of the loads are static and the traffic is constantly starting and stopping. This section of US 169 carries approximately 400,000 ESALS per year. The few cracks that were present in the existing asphalt pavement were in good condition, but the asphalt itself was not, especially along the outer edge. A large amount of rutting (greater than 25 mm [1 in.]) was also present before milling.

The I-94 section was in good condition. Very few cracks were present on the existing asphalt pavement and all were of low severity. The roadway is subjected to heavy traffic loadings (over 1 million ESALs per year). Although this is not a typical application, it provided the opportunity to monitor the performance of the overlay under accelerated loading conditions and to evaluate ultrathin whitetoppings as an overlay alternative for high-volume roads (Vandenbossche and Rettner 1998; Vandenbossche and Rettner 1999).

Study Objectives

The purpose of the test sections was to further evaluate how whitetopping performs in Minnesota and to determine what design features are desirable to optimize the life of the pavement. These heavily instrumented sections allow the static and dynamic response of the pavement under various applied and environmental loading conditions to be measured. In doing this, a better understanding can be obtained on how to more accurately model whitetopping overlays so that a more efficient design method and performance prediction model can be developed.

Project Design and Layout

The first project was located on the outer southbound lane of US 169 in Elk River at the intersections of Jackson, School, and Main streets. The first 240.2 m (788 ft) north of each intersection was overlaid with 76.2 mm (3 in.) of fiber-reinforced concrete and the final 3.66 m (12 ft) was paved 203.2 mm (8 in.) thick. The original asphalt pavement was constructed in 1961 on a sandy subgrade and consisted of a 101.6-mm (4-in.) asphalt surface on 127-mm (5-in.) of a relatively dense-graded aggregate base and 152.4-mm (6-in.) of subbase. In 1991, 50.8 (2 in.) of asphalt was milled and the pavement was overlaid with 38.1 mm (1.5 in.) of asphalt. The average asphalt thickness based on a total of 10 cores was 158.75 (6.25 in.). Temperature and dynamic and static strain sensors were installed at the Jackson Street intersection. A summary of each test section is provided in Table 30.

On the Mn/Road project, a 342.9-mm (13.5-in.) full-depth asphalt pavement was whitetopped with a fiber-reinforced concrete overlay. The original asphalt pavement was constructed in 1993 on a silty-clay subgrade. The existing asphalt pavement was previously a transition zone that separated the 5- and 10-year mainline test cells. The test section was divided up into six separate test cells with various thicknesses and joint patterns. These cells were instrumented with strain, temperature and moisture sensors. A summary of the test cells is provided in Table 31.

The US 169 test sections were paved on September 17, 1997 and the I-94 test sections on October 23, 1997. All concrete was required to have an air content of 6.5 percent ± 1.5 percent and a flexural strength of 2757.9 kPa (400 lbf/in²) at 3 days so that the overlays could be opened to traffic. The flexural and compressive strengths for the concrete on US 169 are provided in Tables 32 and 33, respectively. The flexural strengths for both the polypropylene and polyolefin mixes were similar. The polypropylene concrete had slightly higher compressive strengths even though the w/c ratio for the polyolefin mix was lower. Increasing the fiber content in the polyolefin mix by 8 times that of the polypropylene mix contributed to the lower strength of the polyolefin concrete. Both mixes met the Minnesota Department of Transportation's (Mn/DOT's) flexural and compressive strength requirements.

In addition to the material testing on the US 169 project, extensive material property testing was also performed on the concrete mixture used to construct the I-94 test sections. These material properties are summarized in Tables 34 through 36.

Additional information on the concrete mixture design and the construction of these test sections can be found in the report by Vandenbossche and Rettner (1998).

State Monitoring Activities

Climatic, static strain, and dynamic strain data are collected periodically throughout the year on the US 169 project. On the I-94 project, temperature, moisture, and static strain data were collected every 15 minutes since construction. Dynamic strain data were collected for both static and dynamic truckloads and in conjunction with FWD testing four times per year, once during each season. Distress, ride, and faulting data were also collected four times per year.

Preliminary Results/Findings

Distinct cracking patterns developed within each test section. The UTW test sections with a 1.22-m x 1.22-m (4-ft x 4-ft) joint pattern contained corner breaks and transverse cracks. The corner breaks occurred primarily along the inside longitudinal joint and the lane/shoulder (L/S) longitudinal joint while the transverse cracks developed in the panels adjacent to the shoulder. The transverse cracks typically develop approximately 1/3 of the length of the panel away from the transverse joint. The test section with the 1.83-m x 1.83-m (6-ft x 6-ft) joint pattern performed significantly better because the longitudinal joint does not lie in the inside wheelpath. This significantly reduces the edge and corner stresses. Very tight longitudinal cracks developed on the 152.4-mm (6-in.) overlay with a 1.83-m x 1.83-m (6-ft x 6-ft) joint pattern on I-94. Reflective cracking was not observed in any of the test sections, although reflective cracking has been found to occur in UTW placed on thicker HMA pavements, such as on I-94 (Vandenbossche 2003).

The strains measured on I-94 were consistently lower than those on US 169, even when measurements were made at higher HMA temperatures. The reduction in strain is a result of the increase in thickness and quality of the HMA on I-94 and an increase in the bond strength between the two layers. Increases in the temperature of the HMA also produce much smaller increases in strain on I-94 compared to US 169, except for the strains measured at mid-panel. Strains at mid-panel on the I-94 project approach those measured at mid-panel on the US 169 project. It was found that applying a load when the HMA temperature is high produces similar strains in the UTW regardless of the thickness of the HMA layer when a good bond is obtained (Vandenbossche 2003).

The strain measurements emphasize the importance of the support provided by the HMA layer. A reduction in this support occurs when the temperature of the HMA is increased or when the HMA begins to ravel. The results from the strain measurements and the cores pulled from the test section indicate the HMA ravels at a faster rate along the joints where there is greater access for the water to enter the pavement structure. The lane-shoulder joint is the most difficult to keep sealed and therefore the HMA along this joint was found to be more susceptible to stripping/raveling. Consideration should be given to sealing this joint to limit the water coming into contact with the HMA layer (Vandenbossche 2003).

Repairs were made on three of the six Mn/ROAD test sections on June 20, 2001, after over 4.7 million ESALs. The repairs were made to 13 different areas in the ultrathin whitetopping test sections. In the section with a 3-in overlay and 5-ft by 5-ft joint spacing, four panels were repaired (two locations). Eighteen panels were repaired (six locations) in the section with a 3-in overlay and 4-ft by 4-ft joint spacing. Nineteen panels were repaired (five locations) in the section with a 4-in overlay and 4-ft by 4-ft panels. A detailed description on the repair techniques used was provided by Vandenbossche and Fagerness (2002).

Current Project Status, Results, and Findings

The test sections on US 169 were in service between September 1997 and September 1999. During that period, the sections accumulated approximately 670,000 equivalent single-axle loads (assuming a 152.4-mm (6-in.) portland cement concrete pavement and a terminal serviceability of 2.5). Additional information on the performance of these test sections can be found in the report by Vandenbossche (2002).

Three of the test sections on I-94 will be reconstructed in the summer of 2004. The new test sections will consist of a 127-mm (5-in.) and a 101.6-mm (4-in.) overlay with 1.52-m x 1.83-m (5-ft x 6-ft) panels. Half of each section will have sealed joints and the joints in the other half of each test section will remain unsealed. The monitoring activities will be similar to that for the original whitetopping test sections. The new test sections will be instrumented with temperature, moisture, and static and dynamic strain gauges.

Point of Contact

Thomas Burnham
1400 Gervais Ave.
Maplewood, MN 55109
(651) 779-5606
Tom.Burnham@dot.state.mn.us

References

Vandenbossche, J. M. 2003. "Performance Analysis of Ultra-thin WhitetoppingIntersections on US-169." Transportation Research Record 1823. Transportation Research Board, Washington, DC.

---. 2002. The Construction and Performance of Ultra-thin Whitetopping Intersections on US-169. Final Report. Minnesota Department of Transportation, St. Paul.

Vandenbossche, J. M., and A. J. Fagerness. 2002. "Performance, Analysis and Repair of Ultra-thin and Thin Whitetopping at Mn/ROAD." Transportation Research Record 1809. Transportation Research Board, Washington, DC.

Vandenbossche, J. M., and D. L. Rettner. 1999. "One-Year Performance Summary of Whitetopping Test Sections at the Mn/ROAD Test Facility." Proceedings, International Conference on Accelerated Pavement Testing, Reno, NV.

---. 1998. The Construction of US-169 and I-94 Experimental Whitetopping Test Sections in Minnesota. Minnesota Department of Transportation, St. Paul.

More Information

• High Performance Concrete Pavements: Technical Summary
• Pavement Publications

Contact

Sam Tyson
Office of Asset Management, Pavement, and Construction
202-366-1326
E-mail Sam