July Placement for MnROAD
Preservation Test Sections
By Dr. Buzz Powell, P.E.
Planning and procurement are underway for the placement of northern pavement preservation sections in central Minnesota in July 2016.
MnROAD worked with state DOTs with a northern research focus to develop a consensus to utilize 2.1 miles of Mille Lacs County Road 8 as the low-traffic road, and U.S. 169 as the higher-traffic road, near Pease, Minn.
Both sections are located about 45 minutes north of the main MnROAD test site on I-94 near Albertville just north of Minneapolis. Martin Marietta Aggregate’s Waite Park granite will be the aggregate source and Flint Hills Resources will provide the asphalt emulsions.
Age and pretreatment condition of the existing pavement surfaces on County Road 8 and U.S. 169 were the primary factors in the selection process for both locations. The original treatments/combinations from Lee Road 159 will be placed in both locations in order to encompass the effects of thermal cracking and snow plow damage.
The objective to replicate the original southern research on Lee Road 159 in a northern climate was achieved, noting the same types of minor changes made in treatments and combinations prior to placement on U.S. 280 (i.e., refining the number and type of Thinlay sections).
Vance Brothers will be the placement contractor for the northern treatments just like they were for the southern treatments, which will eliminate the otherwise confounding effect of placement quality on performance.
Also, the Fall 2016 sponsor meeting will be held at MnROAD so funding partners can observe post treatment condition of all the low and high volume road treatments/combinations.
Focus on Northern Climate
Full-scale accelerated pavement testing has been conducted at the National Center for Asphalt Technology (NCAT) Pavement Test Track since 2000. The Minnesota DOT’s Road Research Facility (MnROAD) has been conducting research in these same focus areas for northern states since 1994.
Now, the sixth research cycle at the NCAT Pavement Test Track and the third phase of MnROAD research are for the first time engaged in a research partnership that is cooperatively funded by numerous state DOTs from all over the country for the purpose of executing a national long-term pavement preservation benefit experiment. The objective of this preservation group (PG15) experiment, in which FP2 is an equal funding partner, is to quantify the benefits of pavement preservation on both low volume and high volume roadways with results that are implementable in both northern and southern U.S. climates.
Performance of a comprehensive selection of treatments and combinations will for the first time be related to varying levels of pretreatment pavement condition in both hot and cold climates. This will equip agencies from all over the country to select future treatments that will provide the best life cycle investment for each individual roadway.
More information on the partnership and nationwide experiment it supports at http://www.dot.state.mn.us/mnroad/ncatpartnership/index.html
Tests in Southern Climate
The first preservation treatments were placed in select (100-ft., single-lane) sections on the NCAT Pavement Test Track in the spring 2014 after trigger levels of cracking (20 percent of the total lane area) were reached. A limited number of treatments and combinations were carefully selected for accelerated traffic testing on the track in order to ideally complement a larger number of low-traffic treatments and combinations that were placed off the track in summer 2012 on Lee Road 159 (a dead end access road to a quarry and asphalt plant).
Treatments were placed in 100-foot sections in both the inbound (lightly loaded) and outbound (heavily loaded) lanes. FP2’s participation in the design and execution of the 2012 experiment was key to the success of the overall effort.
At deadline in the middle of April 2016, approximately five million equivalent single axle loadings (ESALs) had been applied in an accelerated manner to select preservation treatments placed on the NCAT Pavement Test Track in spring 2014. Well over one-half million ESALs had been applied in the more heavily loaded outbound lane of the comprehensive array of preservation treatments applied on Lee Road 159 in the summer 2012. And over 1.25 million vehicles have driven on the high traffic treatments applied to U.S. 280 in summer 2015, with almost a quarter million trucks).
The performance (quantified with weekly performance measurements for roughness, rutting, macrotexture, and cracking) of all treatments and combinations has generally been very good on all three southern locations (the track, Lee Road 159, and U.S 280). Crack sealing, scrub sealing, micro surface, cape sealing, and thin overlays all have demonstrated short-term life extending and condition improving benefits. Long-term data collection will quantify the full benefit of pavement preservation in a southern climate.
State highway agencies interested in participating in this pavement preservation and recycling research should contact either Ben Worel (Ben.Worel@dot.state.mn.us) at Minnesota DOT, or Buzz Powell (firstname.lastname@example.org) at NCAT for more information.
Powell is assistant director and Test Track manager, National Center for Asphalt Technology, Auburn, Ala.