Sustainable Pavements
Webinar Transcript
Wednesday, July 29, 2:00-3:00 P.M. Eastern
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Description
This webinar provided an overview of FHWA’s Sustainable Pavements Program and highlighted recent activities including the newly released Sustainable Pavements Reference Document. The webinar also showcased how FHWA’s Western Federal Lands Highway Division has employed sustainable pavement techniques in recently completed Federal lands roadway projects.
Presenters
The presenters included:
- Mike Culp of the FHWA Office of Natural Environment;
- Alex Oster of the U.S. DOT Volpe Center;
- Gina Ahlstrom of the FHWA Office of Asset Management, Pavement and Construction;
- Brad Neitzke of the FHWA Western Federal Lands Highway Division.
Full Transcript
Mike Culp
Good afternoon. My name is Mike Culp and I'm the Team Leader for the Sustainable Transport and Climate Change team here at Federal Highway in Headquarters. I'm glad you could be with us today. This is the third webinar in a series that we've done on different activities and initiatives here at Federal Highway Administration that address sustainability. A lot of different areas were discussed in a document that we put out last year in June of 2014 that highlighted different activities at Federal Highway, and we're doing this webinar series to highlight a few of those areas. We've already completed webinars on Access and Affordability and also on Linking Planning and Asset Management. And so basically we are going to address a different action area, and it's going to be on Sustainable Pavements. So we're very pleased today to have Gina Ahlstrom, who was recently selected as the new Team Leader for the Pavement, Design and Analysis Team in the Office of Asset Management, Pavement and Construction here at Headquarters. And we're also happy to have, presenting along with Gina, Brad Neitzke, a Senior Materials Engineer at Western Federal Lands Highway Division at Federal Highway, who will be describing how they've incorporated sustainable pavement principles and technologies into some of their projects. And so I want to thank both of them for being with us today. And with that, I'm going to turn it over to Alex Oster, who is a Community Planner at the Volpe Center, who's going to moderate today's webinar.
Alex Oster
Thanks, Mike. Welcome everyone. Before I begin my presentation, I just wanted to cover a few logistical items. First and foremost is a reminder all attendees are on mute, but please do go ahead and utilize the chat pod located at the bottom left of the screen to pose any questions at any time during the webinar. We will have the speakers address questions during the Q&A session, which will be at the end of the webinar. Also the webinar will be recorded and posted to the FHWA Sustainable Highways Initiative website. To download a copy of today's presentation, go to the file pod in the bottom left of your screen. In the pod, we also have included a copy of the FHWA Sustainable Pavements Reference Document, as well as a listing of key terms that will be discussed today. Finally, throughout today's webinar, we will be asking participants to answer poll questions. And we really greatly appreciate any and all responses you provide. I will now open up the first set of poll questions, and allow you a few minutes to respond.
Okay. We are going to close the polls now. Thanks again, for your responses. Now before we have a more detailed presentation on Sustainable Pavements, I wanted to briefly introduce FHWA's Sustainability Report. As Mike mentioned, FHWA released Advancing a Sustainable Highway System, Highlights of FHWA Sustainability activities in June of 2014. The purpose of the report was to showcase some of the ways in which FHWA is incorporating and embedding sustainability into its activities. This report serves as a resource to the public, transportation professionals, and those working within FHWA to help them better understand the various sustainability initiatives moving forward within the agency.
As Mike mentioned, the Sustainability Report features sustainability action areas, which are listed on the slide. The action areas represent significant opportunities for new growth and advancement and sustainability for FHWA. They also have high potential for achieving sustainability goals and benefits in the near term. Although, not identified as sustainable action areas, the report also includes other key programs and initiatives such as climate change mitigation and environmental streamlining. The report also highlights FHWA's Sustainable Highways Initiative, and related efforts, like the Infrastructure Voluntary Evaluation Sustainability Tool, otherwise known as INVEST, and FHWA's Sustainability Working Group. Additionally, each section of the report showcases exemplary State, Regional and Local examples of Sustainable Transportation Practices. Today's webinar will focus on one of the sustainability action areas, Sustainable Pavements. Now before we begin the presentation on Sustainable Pavements, please take a moment to complete the poll questions on your screen pertaining to the FHWA Sustainability Report, and how you're addressing sustainability in your work.
Great, and thank you, everyone. I will now turn the webinar over to Gina Ahlstrom with FHWA's Office of Asset Management, Pavements and Construction.
Gina Ahlstrom
Okay, great. So to start here, sustainability is a term we continue to hear. It's not just a fad. In the transportation sector, agencies are seeking more sustainability solutions, and in particular, Pavement and Materials Engineers need more technical guidance and resources on how sustainability pertains to them.
On the slides is a very common definition of sustainability, one that you have likely heard. When we talk about sustainable pavements, they should achieve the engineering goals for which it was constructed. Preserve, and ideally, restore surrounding ecosystems. Use financial, human and environmental resources economically. And meet basic human needs, such as health, safety, equity, employment, comfort and happiness.
Pavements play a significant role in our highway system. Let's try to put this into context. Over 2.65 million roads are paved, and about 1.4 million roads are unpaved. Over 47,000 miles of interstate highways comprise just over one percent of highway mileage, but carry one-quarter of all highway traffic. Nearly 70 percent of all freight tonnage is carried by trucks.
The pavement life cycle starts with materials production and continues through the end of life. Although we know that realistically, many pavements simply do not die, they are reused or repurposed in various ways. There are opportunities to improve sustainability throughout the entire pavement life cycle. In the materials phase, options are reduce, reuse, and recycle materials. There are examples like using warm mix asphalt (WMA) and recycled asphalt pavements, or recycled asphalt shingles (RAS), the use of two-lift concrete construction, and long-life pavements. In the design phase, you can use robust design procedures and optimized materials. During the construction phase, we should focus on good quality, efficiency, and smoothness. In the use phase, we want to meet the needs of users by considering things such as smoothness, safety, noise, aesthetics, and possibly even pavement albedo. In the maintenance and preservation phase, we should be using effective treatments and maintaining smoothness. And finally, in the end of life, we should reuse and recycle as much of the existing pavement as possible.
In 2010, the Sustainable Pavements Program was formed. The program goals are to support the U.S. Department of Transportation goals for sustainable transportation; increase knowledge about sustainability of asphalt and concrete paving materials; and advance and promote sustainable technologies and practices in all aspects of pavement engineering throughout the pavement life cycle.
There are three major program activities that I will talk about today. I will talk about how we will engage stakeholders. I'll spend a bit of time going over the technical guidance we have published, specifically the material that's outlined in the document Towards Sustainable Pavement Systems, A Reference Document. And finally, I will talk about the technical resources we have.
Program area 1 is to engage stakeholders. It is important that stakeholders are engaged in our discussions on pavement sustainability. We formed a Sustainable Pavements Technical Working Group (SP TWG) that is composed of 20 members who represent Federal Highway Administration, State Departments of Transportation, and other public agencies, academia and industry. We have a wide group of friends of the Sustainable Pavements Program. And I believe that demonstrates the high level of interest in this area. The group has met twice per year since 2011, and we have discussed a wide range of topics. The discussions can get lively, but it's useful to work through complicated issues with input from the wide group of stakeholders that we have.
The second program area I will talk about is technical guidance. The majority of the remainder of my presentation will highlight the content discussed in the document Towards Sustainable Pavements Systems, A Reference Document. This document is the first comprehensive version of its kind that discusses sustainability throughout the pavement life cycle. The document focuses on strategies that can be used today to benchmark and improve pavement sustainability. It is important to note that pavement sustainability is not one-size-fits-all.
These are the chapters in the Reference Document. A wide-range of topics is covered from materials processing to how pavements fit into the larger system.
Chapter 1 discusses what is sustainability and specifically how it pertains to pavements. Next Chapter 2 covers the role of pavements, defines the pavement life cycle, provides an overview of measuring sustainability and a consideration of trade-offs that's needed.
In Chapter 3, we discuss materials considerations. The graphics here show typical asphalt pavements and typical concrete pavement mixtures. And the red piece of the pie shows exactly how much, in general we use of aggregates in our mixes, which is substantial. Some strategies for improving sustainability are reducing the amount of virgin aggregate use, reducing the impact of virgin aggregate acquisition and processing, and reducing the impact of transporting aggregates.
Chapter 3 continues to talk about specifically asphalt materials considerations. We can reduce virgin binder content, and that may be through increasing the use of recycled asphalt pavement (RAP), recycled asphalt shingles (RAS), or ground tire rubber (GTR). We should or could reduce energy consumed in emissions generated during production, look at extending the service life, and use locally available materials.
Specifically for concrete, we can reduce energy consumption and emissions during cement production, , and that may be through the use of blended cements or the use of supplementary cementitious materials (SCMs), increase the use of recycled materials or co-products and waste materials, and improve concrete durability.
Chapter 4 discusses ways to improve sustainability in the pavement design process. Some strategies are looking at robust pavement designs for optimization, for example through use of the Mechanistic Empirical Pavement Design Guide (MEPDG), looking at long-life designs, enhancing pavement smoothness over the life cycle, noise-reducing surfaces, and we can't forget about pervious pavements.
Chapter 5 discusses ways to improve sustainability during the construction phase. For asphalt pavement construction, you could look at effective construction planning and sequencing, achieving target densities, preventing segregation, proper construction of longitudinal joints, and achieving initial smoothness. Some strategies for concrete construction are, again, looking at effective construction planning and sequencing, proper installation of embedded steel, achieving initial smoothness, looking at surface texture to balance friction and noise, good curing practices, and effective jointing practices to prevent uncontrolled cracking. The bottom line is that a well-constructed pavement is not only good engineering practice, but by eliminating the need for increased maintenance and ensuring the design life, you're also increasing sustainability.
Chapter 6 discusses the use phase. Some major issues during the use phase are vehicle pavement interaction, tire pavement noise, storm water management, possible urban heat island issues, and lighting. Some general strategies here are to maintain smoothness, avoid utility cuts particularly in urban areas, effective surface texture for noise control, pervious pavements for stormwater runoff, and surface friction for safety. This chapter provides an up-to-date summary of the research that's been done in the area of the use phase and their impacts. And in many cases, a single answer or solution cannot be identified at this time, but all of the information is there for agencies to go and read and to make informed decisions.
Chapter 7 focuses on maintenance and preservation strategies. Some of the key points are less material-intensive treatments have lower environmental impacts, treatments with lower life cycle costs are often correlated with lower environmental burden, and maintaining pavements in smooth condition reduces environmental impacts for high-volume roadways.
In Chapter 8, we focus on the end of life considerations. In general, we want to work with pavements that are in place when possible. For example, considering in-place recycling for hot mix asphalt (HMA) or on-site recycling for Portland Cement Concrete (PCC). We also want to increase the use of recycled materials, again using RAP, RAS, and recycled concrete aggregate (RCA). And again, reducing the use of virgin materials.
In Chapter 9, we cover pavements and how they fit within a larger system. For our Pavement and Materials Engineers, this is typically a soft-side subject. However, we're seeing much more collaboration between typical, soft and hard-side engineering. Some strategies to consider are adopting a systems approach to sustainability, looking at ways to incorporate pavements into our communities, and sustaining ecosystems. We can also improve worker and community health by reducing odors, particulate matter, or noise.
At the end of the document, Chapter 10, in the last chapter, we discuss measuring pavement sustainability. There are different ways to assess pavement sustainability. The first listed here, and most common, is life cycle cost analysis, and that's the economic analysis over the entire life cycle of a project segment. Life cycle assessment is the quantification of environmental impact and this is an emerging area, and one that we're delving into now under our Sustainable Pavements Program. Finally, we have rating systems, which focus on agency-defined best practices and scoring them by a common metric, which is typically points. You can see here for rating systems, one typical one that you could use is INVEST, and that was mentioned earlier in the program, which was developed by Federal Highway Administration.
So here is the cover of the Reference Document. It was published in February of this year. It's available on our website. Hard copies are also available, so you can download it free of charge or you can obtain a hard copy of the document as well.
Next I'll talk about the third program area, which is deployment. We published two Tech Briefs that are available also online on our pavements website. One is on life cycle assessment, and another one, generally on pavement sustainability. We have three other Tech Briefs that are under development now, one on climate change and pavements, another, more specifically on sustainability in asphalt pavements, and one on sustainability and concrete pavements. We expect those will be published sometime this summer.
We've done a number of different outreach activities. We participated in a workshop at TRB of this year. It was very well-received with over 100 participants on a Sunday, which I think was a pretty good turnout. We have an ongoing series of five webinars. We've held three webinars already. We have two more coming, one on August 20th on preservation and rehabilitation and another one on September 9th on the use phase. All of the webinars have been recorded. Webinar 1 is already posted online. The audio and the PowerPoint slides are there for you, if you were not able to catch it, and if you're interested. And you can also find information on our website about registering for the additional two webinars.
Here is our website (http://www.fhwa.dot.gov/pavement/sustainability/). We have a number of different references documents, and our Tech Briefs are posted. We have technical articles that will be coming, which highlight various chapters and sections of the Sustainable Pavements Reference Document. We have a number of links and resources, so all of the references that you can find in the reference document, you can link to, to get more information on a particular subject. It is a wealth of information. If you haven't been there, please check it out.
So in summary, sustainability is not a destination, it really is a journey. There is not one size that fits all. And there really are various ways that we can look at incorporating sustainability into what we do every day. There are many opportunities, as you can see, through all life cycle phases. And you do want to make sure you consider various trade-offs and contact sensitivity when you're looking at your pavement design. Again, we have a number of different resources where you can get more information. Our Reference Document is very compressive. We have Tech Briefs, Webinars, our webpage and various other outreach activities. Feel free to email me (Gina.Ahlstrom@dot.gov) if you would like to get on our Friend's List, or any other information. And with that, I will turn it back to Alex.
Alex Oster
Excellent, thanks, Gina. You'll now hear from Brad Neitzke, with FHWA's Western Federal Lands Highway Division.
Brad Neitzke
Thanks, Alex. I'd like to give a specific example of a sustainable pavement approach that the Western Federal Lands Division has utilized. It relates to Gina's presentation, the end of life usage of material, and how we've incorporated that as a pavement practice within Western Federal Lands. For a brief history, we've actually, within the Division, utilized different recycling techniques for pavements, in particular, in-place recycling of hot mix asphalt pavements to incorporate them into recycled bases, and this is an example of where an in-place technique was not available due to the design constraints, and so we opted for a central plant, cold recycled asphalt pavement. And this has been done most recently on the Going to the Sun Road Project in Glacier National Park. The project is still under construction; however, the construction of this portion of the work has been completed. And so through the design phase, we were able to review what possible techniques we could utilize in order to reuse the pavement. And in reviewing that, we found that we were capable of milling the pavement and having a location that we could stockpile it and then reuse it as a part of the new structural pavement design. That was available to us through a stockpile site that was close to the project. And so it became a very effective approach as we went through the design phase, and ultimately came to this way of reutilizing the pavement at the end of life.
So the reasons why we were able, as we approached this, in looking at it, the reasons really pertain to the location of Glacier National Park. There are limited material sources that are available around the park, and many of them are long distances away. In addition, because we are within park boundaries, there are no sources that would be available within park boundaries to utilize as part of their stewardship of the national park. And so as we approached the design aspect and going through it, we wanted to look at what sources were available to us, and try and minimize the haul distance. And in addition, we wanted to minimize the footprint of the new roadway as we were reconstructing it. And so in doing so, if we could maximize the strength of various pavement layers, that way we would come up with a thinner pavement section, and then that would have minimal impacts on the associated trees and aspects of the roadway beyond the ditches to help the environment in which the road is constructed in order to minimize the footprint. So that led us to an opportunity to use central plant recycled pavement as a way to mill and stockpile and bring the pavement back. That pavement has a stronger strength in relation to a pavement structural design than virgin aggregate base. And so therefore it helps us to reduce that overall depth, which again, reduces the impacts beyond the existing pavement edge.
So the benefits in regard to the use of this, we were able to reduce the cost by reducing the hauling and the aggregate production, so it became very, very cost effective for us to do that. In addition, we had environmental advantages by not depleting aggregate reserves that are located within about a 50-mile proximity of the project. And so that is certainly a benefit. In addition to that, we were able to minimize the dust. This recycled pavement layer does not require any dust abatement like a virgin aggregate base would, and so that was a benefit to the tourist who use the facility, and the pavement provided a dust-free interim surface in which to traverse, which was, again, a benefit. The thinner pavement structure did reduce the impacts to the vegetation and trees. Again, because the recycled pavement layer was stronger than virgin aggregates, and therefore provided a very effective strength mechanism which we could utilize. And we still met the minimum 20-year design life of what the pavement was designed for. And so, going through the design phase of the project to ultimately constructing it, we could see various benefits, not only in the economics of it, but in the environmental aspect of it, which, again, promotes a very sustainable approach.
So the methodology was simple in that regard. What we did was to remove the existing pavement and stockpile it. That was part of the contract, so the contractor came in with a milling machine and reduced the pavement, and removed it and stockpiled it. We were able then to correct the existing grade and structure and we brought that up to a hub elevation. So it met new line and grade requirements as necessary. And then simply brought the pavement back and recycled it. There's 100 percent recycled asphalt pavement, using an engineered emulsion as a stabilizing agent. That enabled us to increase its strength. And so once that was accomplished and brought back, we had the surface then which received a final overlay to meet the structural requirements for the 20-year design.
So these are just a few construction slides to get you a feel for the process of it, and what it actually ended up looking like in the end. Here you have a picture of the recycled asphalt pavement that's getting loaded into a single cold feed bin that will be taking it up to have it mixed. In the background of the slide, you can see the pile of recycled asphalt pavement that was stock-piled. All of that material was reused and brought back to the project.
In this picture, you'll see the pugmill output, which is actually incorporating the mixture with the emulsified asphalt. We are dumping the pavement onto the ground as a surge pile. You see the frontend loader in the background that then comes and picks up the material and puts it in a hauling vehicle to haul it to the grade.
In this slide the pavement was actually getting placed. It's a conventional pavement construction technique. So we use a paver. The paver's not heated because this is a cold mix, so there's no energy that's utilized in heating the screed material, and again, it's placed as conventional pavement.
In this next slide you see the completed compaction surface.
In this last one you see the completed surface in three different stages. In the top left, you see the completed compacted surface. In the bottom left, you see one that's received a fog seal, and that's how we seal a surface in order to maintain its integrity before we get the overlay on it, and before any traffic has been on it. And on the right side, you see what the pavement looks like after traffic has been placed on it. And so again, as you look to the right side of the slide with that pavement, the recycled asphalt pavement, as it's done in this process, actually looks very much like conventional pavement. And it certainly is much stronger than using virgin aggregates. And then again, as we finish the next construction phase of this, would be to simply put an overlay on, and that would complete the construction process, and complete the project from a pavement structural standpoint as it was designed. So again, this is a technology that we use, or a technique that we use oftentimes in the work within our Western Federal Lands Division. We are in very remote locations, and so we do look at the most opportune times where we can reuse, whether it's pavements or aggregate materials, because our sources are very limited, and most times we have long-haul distances. So again, it does provide us a useful technique that we can analyze on a project-specific level to see if we can incorporate techniques like this on other projects as well. With that, I will turn it back to Alex for questions and answers.
Questions and Answers
Alex Oster
Great, thanks Brad. We will now take any questions that you have regarding the presentation. We've seen a couple come in already, so go ahead and type your questions into the chat pod and we'll answer them in the order that they are received. For the first question, this comes from Jamie Bents, "Are noise reducing pavements being used for noise mitigation anywhere in the U.S.?" So that question is posed to both Gina and Brad.
Gina Ahlstrom
I'll take a crack at it. Yes, we do see frequently that their noise-reducing surfaces are used. For asphalt, commonly open-graded friction courses are used, and that's pretty common. For concrete, there's been a lot of research done. Diamond grinding, or diamond grooving tend to be the quietest, followed by longitudinal tining. But there's also some research and some newer methods, such as something called the "next generation grinding" for concrete surfaces, that's a combination of grinding and grooving. That has also been found to be very effective in noise control. So this is all kind of discussed in various chapters of the Reference Document, so you can learn more information there. But yes, they are commonly used.
Brad Neitzke
Yeah, and I know of some specific examples that Arizona Department of Transportation is using in regard to open-graded friction courses that also contain ground tire rubber, and they are using those as noise mitigation measures in overlays of concrete pavements in the Phoenix area, as a specific example.
Alex Oster
Great! Thank you to both Gina and Brad for those answers. We have another question. IT comes from Jim Olson and he asks, "Is there research on the sustainability impact of the concept of perpetual pavements?" So again, either of you can answer that question.
Gina Ahlstrom
Sure, so you can find some information about perpetual pavements in Chapter 4 of our document. And there are references listed there if you'd like more information. But generally, when you're talking about something like a perpetual pavement, or a long-life pavement, you're increasing the design life and ultimately decreasing the frequency of maintenance and rehabilitation. So in general, it's a very good concept, depending on your specific situation. We talked a little bit about trade-offs just briefly during the presentation. And of course, you always want to look at your trade-offs. And for example, some potential impacts with using polymer modifications. But really, you would have to do that full environmental assessment, typically using a life-cycle assessment to kind of quantify all of those impacts.
Alex Oster
Great, and thanks, Gina. We have a couple more folks typing in, so while everyone is posing their questions in the chat pod, we're going to go ahead and open the final polling questions that we have, so if you wouldn't mind filling those out while you're jotting down your questions for the presenters.
And again, if you have any questions, please go ahead and type them into the chat pod. We'll give folks a few more minutes to type in their questions. Well, it doesn't seem like any other folks have given any additional questions, so we'll go ahead and conclude today's presentation. So we would once again like to thank all of our speakers for their great presentations, and for taking the time to share their experiences on advancing the use of sustainable pavements. We also would like to thank all of you attendees for participating. Please go ahead check out our future webinars in the series. We should have some additional webinars coming in the fall. That concludes the webinar for today.
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