NRRA Newsletter: April 2017
By Glenn Engstrom, Director
It’s time. As we approach the one year anniversary of the National Road Research Alliance, we need to start thinking about strategy. You don’t have to go any farther than our tagline/philosophy—Strategic Implementation Through Cooperative Pavement Research—to understand that strategy is a key part of this equation.
That said, we don’t want to get too tied down in strategy discussions to the exclusion of getting actual work done. Our future strategy conversations need to be focused—very focused—on implementation. We need to bridge the gap between great research and operational practices in the field. Great research is not enough anymore.
Here are some elements that will shape our strategy discussions:
Goals: Our strategy will set goals and hard deadlines on projects. For example, if we want to develop a better specification for hot mix longitudinal compaction, our alliance needs to put a deadline on that spec. Our goals will be informed by our principles, and we all know what our principles are. With that in mind, I plan to have a strategic plan completed by the end of the fiscal year.
Meetings: Sorry, but we are going to need to have a couple of meetings to bang out a strategic plan. We have contracted with consultant, Tom LaForce, to help us get this done. Some of the steps he will initiate are:
- He will plan, facilitate, and document up to five meetings, each lasting no more than three hours. Meetings will be onsite with MnDOT staff and online, involving other members of the NRRA.
- He will offer suggestions and guidance for how to create a strong and productive leadership model for the NRRA.
- His organization will provide phone and email support between meetings as needed.
The NRRA will do the logistics of getting the meetings set up. If our executive committee is in a particularly collaborative mood and we don’t need all five meetings, our consultant's time can used to assist in collecting feedback from partner organizations.
Collaboration: We could, of course, restrict this exercise to a small group of people, such as the executive committee, and get it done quickly. However, one of our principles is summarized in the African proverb: “If you want to go quickly, go alone. If you want to go far, go together.” That’s why we will be aggressively gathering input from all the agency and associate members as we create this document. Collaboration could slow down this process, so we are going to be dogged in our correspondence and will expect members to respond quickly. Thank you for your help in shaping the future of an organization that can truly make a difference in the infrastructure of our nation.
MnROAD Construction Update
Even though MnROAD is one of the biggest and most sophisticated pavement research facilities in North America, our construction program for 2017 is a pretty big deal.
First off, the scope is larger than in previous years. MnROAD does research on three different sections of road: the high-volume original I-94 westbound (built in 1973), the mainline I-94 westbound (originally opened in 1994) and the low-volume road closed track. All three roads will be having test cells installed this year, which speaks to the size of this year’s construction.
This is also the first season that has National Road Research Alliance-sponsored test cells—experiments requested by alliance members and funded through the combined pool of money created by the alliance. In terms of “tangible benefits” for members in the NRRA, this is the big one. MnDOT will be providing the $2.5 million of construction funding from their state road construction funding.
The bid letting date for this year’s construction will be April 28, but the plans were made available for contractors on March 31. We hope this will give the projects more exposure and generate more interest. Construction will begin June 5 and continue until November 2017.
Forensic Analysis of Failed Cells
Before any construction starts this year, each test section that is being reconstructed a will receive a final forensic study. This allows researchers to get a look at each layer to see the distress that has occurred over the years—and make the final analysis of why it failed. There are always a lot of theories on the causes of what actually failed, but until the forensic is performed, you don’t have proof of what happened. These finding will help build longer lasting pavements in the future.
Studies and Test Cells to Watch
HMA Overlay and Rehab of Concrete and Methods of Enhancing Compaction: States are looking for longer lasting HMA overlays of concrete. New mix designs were developed to promote long-term performance--including how reflective cracking effects can be minimized through design or other joint treatment.
Cold Central Plant Recycling: Other states have utilized RAP stockpiles into plant mix base course mixes (layers below the wear surface) to effectively recycle these materials in a controlled mix design. How can these layers best be utilized and what type of surface mix or chip seal can be placed on top?
Fiber Reinforced Concrete Pavements: Nationally, states want to get a better understanding of the beneficial use of fibers in concrete pavement layers. Is it worth the cost? How can it be best utilized in both thin city streets and higher volume roadways? Can it be used in new construction and in concrete overlays? We are going to find out.
Long-term Effects of Diamond Grinding: Each state has aggregates that have been used in concrete pavements that are considered reactive. Questions arise as to whether diamond grinding might accelerate deterioration in these pavements? We will also be investigating what types of topical sealers can be used to treat the surface after the diamond grinding.
Early Opening Strength to Traffic: What effect does heavy traffic loading have on the long-term performance of full-depth concrete pavement, as well as fast-setting repairs? Test sections will be loaded by a pickup truck in one lane, early enough to produce shallow ruts in the surface. In the other lane, a loaded 18-wheeler will travel over the new concrete immediately after it sets--and then sequentially every 6 hours up to 30 hours. The long-term effects of these early loadings will then be evaluated.
Optimizing the Mix Components for Contractors: What effect do low cementitious content mixes have on long-term performance and constructability of concrete pavements? Two low cementitious content mixes will be studied to give agencies a better understanding of cost savings. Can these savings be achieved without significantly affecting long-term performance?
Compacted Concrete Pavement (CCP) for Local Streets: Compacted Concrete Pavement (CCP) is a form of Roller Compacted Concrete (RCC) that has a standard concrete pavement surface texture. The RCC industry has been successful in Michigan and Kansas constructing CCP pavement on local streets. This research will determine if the texture that is accomplished is durable in harsh freeze-thaw climates.
Recycled Aggregates in Aggregate Base and Larger Subbase Materials: States continue to look for effective ways to recycle materials into unbound bases. This research will add to MnROAD’s understanding of recycled bases and what seasonal strength values can be used for advanced mechanistic designs--and how they are affected by size/gradation.
Maintaining Poor Pavements: Road owners continually have less and less funding to maintain their roadway systems. What practices should be used for stabilizing both HMA and PCC roadways when longer-term repairs cannot be done due to funding levels?
Partial Depth Repair of Concrete Pavements: Agencies are continually seeking improved materials and methods for the repair of concrete pavements. In this study, up to 15 innovative concrete pavement repair materials will be evaluated on the concrete panels of the westbound I-94 bypass parallel to the MnROAD mainline.
Thin Overlays: Experimenting with very thin overlays could provide a real benefit for a lot of the roads currently out there. The premise is that with thin overlays, we can smooth out the ride and extend the longevity of older roads. “We don’t often get to reconstruct random roads these days, and when we do we have much better specifications for low temperature cracking. By the same token, we have to maintain all those older roads built before we had performance grade binders,” said Dave Van Deusen, Principal Engineer with the Materials and Road Research Lab in Maplewood, MN. We will be doing this makeover on an original section of MnROAD built back in the 90’s.
In one experiment, we have a head-to-head comparison of thin overlays on two sections of road. One section has a thick base and subbase under the asphalt. The other has a heavy asphalt top with very little base.
Van Deusen says if we can get an extra five years of life out of road using thin overlays, he would be pleased. Often, he admits, he is surprised by how long these “short-term” fixes actually last.
Research Pays Off Upcoming Topics
This ongoing series of webinars happens every third Tuesday of the month at 10 a.m. (CST). If you missed the last one, Determination of Structural Value of Geogrid Reinforcement in Pavement Layers, you can review it on YouTube.
The next presentation will be on April 18 and will address the National Road Research Alliance's Long Range Research Plans
May Pavement Conference--Save the Date
The NRRA Pavement Conference is approaching fast--May 24, 2017 in St. Paul, MN. The Conference will feature:
- Keynotes from Matt Witczak and Julie Vandenbossche
- A State of the NRRA panel discussion about present and future research
- NRRA case studies from around the country
Join us the day before the conference for workshops and a tour/cookout at MnROAD. Please encourage your colleagues to join us in May. If you are an associate member and don't have your table reserved for the expo, please contact us.
Member Hightlight—Ingios: What gets designed, gets measured
By Bob Filipczak
What if our road designers did all of their work in the metric system while all of our contractors and subcontractors worked in inches and ounces. That’s sort of how it is right now, or up until very recently. Road designers using modern design concepts develop their models based on a measure of resilient modulus while contractors measure density indirectly using gamma radiation.
That “until recently” phrase is important because NRRA associate member Ingios has been working on two technologies to measure modulus for pavement bases and subgrades. What and how they measure road construction could significantly change how roads are designed and built.
The first question that comes up when we talk about this disparity is “why haven’t we measured modulus in the past.” We asked David J. White, [President and Chief Engineer] at Ingios, and he confessed that measuring modulus is actually really tough to do in the field. In fact, his company had to invent technologies that would measure the resilient modulus of base materials in a road.
Automated Plate Load Testing (APLT)
The first tool Ingios built is Automated Plate Load Testing. It takes a heavy steel plate and presses it on the pavement grade. It then sends pulses into the layers to simulate vehicle loads—from passenger cars to completely loaded 18-wheelers. Then it measures the modulus. These pulses and measurements can be repeated with the APLT device thousands of times, giving contractors a clear idea of the stiffness of underlying layers before paving begins.
That part is key—being able to measure the modulus before work begins gives the contractor the opportunity to fix things before it’s too late.
This is a clear way, says White, to establish a link from the up-front design to what was actually built during embankment and pavement foundation construction.
Validate Integrated Compaction Monitoring (VICM)
The second tool from Ingios is Validated Integrated Compaction Monitoring. It consists of a sensor package and proprietary software that is installed on the contractor’s compactors. It can also be used with the aforementioned APLT.
This sensor package measures the properties of underlying layers (including modulus and material type) while the compactor is working. Consequently you see results in real time, while the base is actually being compacted. Again by providing instant information to the contractor, mistakes or deficiencies can be corrected prior to construction.
White has received a lot of positive feedback on these technologies from pavement designers. He says that’s because they are finally able to connect their design to the quality control practices in the field. As White puts it, “this is making state of the art part of everyday work.”
He also thinks this will change how designers do their work, possibly saving millions of dollars. White says that by connecting design to outcome using these tools, designers will be less conservative. Put simply, if designers don’t know what they will get when a project is completed, they will err on the side of conservatism—meaning they will increase pavement thicknesses and materials in the grade and subgrade just to be safe. By removing uncertainty (undetected “soft” areas) in the paving results through fast, good measurement, designers can design closer to reality.
Of course, if you can reduce the materials used on a project, the savings add up quite quickly.
White says they have used these base measurement tools in about 50 projects in the U.S., Canada and Latin America. He hopes they will become a standard practice as he and his company get more construction engineers on board.
Member Highlight—University of Texas—Building a Strong Foundation for the Future
By Bob Filipczak
Soheil Nazarian and the researchers at the University of Texas, El Paso’s Center for Transportation Infrastructure Systems are working on developing a comprehensive specification for the proper preparation of the existing subgrade and the engineered bases/subbases to adequately support the HMA or PCC surface. They are one year into a three-year project to provide a unified standard for defining, building and compacting the underlying foundation of our roads. (They are also the newest associate member of NRRA.)
Nazarian has 30 years of transportation research under his belt, and he is convinced that building a strong foundation properly will extend the longevity of our roads. But we need to agree on some standards.
30 Shades of Grades
Trouble is, says Nazarian, there are currently about 30 different specifications on how to build a base. That’s because many, if not most, DOTs have their own specs for grading and subbase and they develop them without collaborating with other agencies or contractors.
The first step, as he sees it, is to establish a national standard for building bases and subbases through AASHTO. With AASHTO’s blessing, the spec would immediately gain widespread buy-in on many levels.
First the states would have a standard that would give them more uniform bases for their roads. Next, contractors would know what the expectations are for each project. Finally, the manufacturers of compacting equipment would have a standard to aim for as they develop new machinery.
The standard Nazarian is hoping for from AASHTO would be, as he put it, more engineering-friendly. That means developing specifications that are more about the mechanical properties of the underlying pavement layers. Those mechanical properties also need to be communicated to manufacturers because, currently, each roller company has different sets of vibration measurements.
That’s just one example of how not having standard specifications interfere with building consistently reliable bases, says Soheil. We need, he says, one uniform definition with mechanical properties.
Getting everyone on board
Because Nazarian has so much experience in the industry, he knows the spec will only happen if they get all the players in the grading industry to participate. That means meeting and interviewing DOTs, contractors and manufacturers. Then his team needs to interview everyone from pavement designers to field inspectors. “You can’t just sit in your office and do research,” he says, “you need to get all the sectors involved.”
Nazarian is very encouraged so far. He has already talked to many state DOTs. In the future he hopes most DOTs will see the value in the base and grading spec from AASHTO and will adopt it. He himself is dedicated to making and keeping the spec as simple as possible with small adjustments made to it over time.
In the end, says Nazarian, everyone will benefit. The nation will have better quality roads, the contractors will provide more uniform product and the specs for manufacturers will give us better equipment.
This is also a priority for the NRRA Geotechnical team (States and Associates). It is currently working to develop a technology transfer “State of Practice” pulling together NRRA members’ specifications and practices related to Subgrade Design for New and Reconstructed. More information on this effort can be found on their Team page
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This newsletter is one way to connect and collaborate with the NRRA, and we are adding more. During TRB in January we launched our Twitter feed. Now we have established a Facebook page. This will give you a more immediate connection to trends in the industry, new research and our work as we build this alliance. Please follow us and encourage your colleagues to follow us. Thanks.