Paving with Recycled Plastic - Hawaii's Pilot Project - Part 2

In part 2 of our series, we talk with Hawaii DOT's Mel Chung and Kristi Grilho, to go deeper into the testing involved in this project.

Related Information

• S4 E1: Paving with Recycled Plastic – Hawaii’s Pilot Project - Part 1
• S3 E40: From the Cutting Room Floor - Questions from a DOT

Have questions, comments, or want to be a guest on an upcoming episode? Email podcast@aashtoresource.org.

Related information on this and other episodes can be found at aashtoresource.org. 

Transcript

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AASHTO re:source Q&A Podcast Transcript

Season 4, Episode 2: Paving with Recycled Plastic – Hawaii’s Pilot Project - Part 2

Recorded: November 21, 2022

Released: June 6, 2023

Hosts: Brian Jonson, AASHTO Accreditation Program Manager; Kim Swanson, Communications Manager, AASHTO re:source 

Guests: Kristi Grilho and Mel Chung from the Materials Testing and Research Branch at Hawaii Department of Transportation 

Transcription is auto-generated. 

[Theme music fades in.] 

00:00:02 ANNOUNCER: Welcome to AASHTO resource Q & A. We're taking time to discuss construction materials, testing, and inspection with people in the know from exploring testing problems and solutions to laboratory best practices and quality management, we're covering topics important to you. Now here's our host, Brian Johnson.

00:00:21 BRIAN: This is Brian Johnson, and I am here to talk to Mel Chung, Branch Manager from the Materials Testing and Research Branch at the Hawaii DOT.

00:00:31 MEL: Hello everyone. Aloha.

00:00:33 BRIAN: And Kristi Grilho also from the Materials Testing and Research branch at the Hawaii DOT.

00:00:39 KRISTI: Thanks for having us.

00:00:41 BRIAN: I have invited you to come and speak with us about a research project or well, I guess more than a research project because it's already being driven on. It's kind of innovative, a project that was set forth by the Hawaii DOT to use recycled plastics in the roadway, Mel, do you want to tell us a little bit about that project?

00:01:07 MEL: Actually, it's come from our administration, our Deputy Director Ed Sniffen. He always has a goal for us. He wants HDOT to be more sustainable, because especially we live on an island. It's really our resources are very finite. We don't have that much. So, we want to make good use of our material to make our infrastructure better. So, we already have a green solution for our concrete which we use cabin cure, but then we don't really have a true solution for. Except we are using rap, so he directed us to look into recycled plastic into our pavement. So that was all beginning. And then he gave us a couple criteria that we have to meet first, because our ultimate goal is really to use our local plastic waste on to our local infrastructure.

00:01:58 MEL: But currently in Hawaii's industry, we don't have that capability to use our local waste yet. So, he told us we have to find a product that is 100% US waste plastic. And then the performance has to be better than our control mix. And then we have to be very environmentally conscious. He wants the product to have no microplastic leaching, so that's what's the three criteria that. We're going for.

00:02:28 BRIAN: Those are really lofty goals set forth by Ed Sniffin and his administration. It's great, and I applaud the effort of trying to make the most of a difficult situation when people on the mainland think of recycled plastic, you know, there's a lot of attention. OK, the bottles, right? Milk jugs and plastic water bottles and things like that. Is it the same situation in Hawaii or what other plastic waste are you concerned with there that we might not be concerned with here?

00:03:01 MEL: Yeah, we do have postconsumer plastic waste, a lot of them. We collected it, but then there's no way to go in the island. So we either ship it to the mainland or ship it to Southeast Asia. We don't know where it goes, or we just burned it. So, it's not a good alternative. Another problem that we have is we have a lot of fishing nets. That are plastic, HDPE that is floating to Hawaii from all over the world, so we are. Our beach right now looks so nice, but in some locations it's really polluted. So, uh, HPU have an effort. You know, they try to collect those waste. We have a lot of fishing nets for the next project. We want to try to use those fishing nets and pave the road that will be future.

00:03:46 BRIAN: OK, so that you've got the plastic fishing net issue that you're dealing with in Hawaii and the post-consumer plastic. And then can we talk about microplastics a little bit?

00:03:56 KRISTI: I think that part that we want to check for is just in case while it's being incorporated in the mix. That we want to make sure that it doesn't leach out of the road and go into the storm water.

00:04:10 BRIAN: I'll tell you my thoughts on microplastic and we'll see if Kim keeps this in one of the apartments that I lived in once was on the other side of a highway and there was one of those sound barriers in between. And one thing that I didn't understand about living that close to a highway is it generates quite a bit of pollution. So, there would be basically what looked like. Little tiny particles of rubber and little, tiny particles of possibly roadway and other debris would get into the air and coat the small patio that was in the back of my apartment. That was the only time that I really thought about what kind of other pollution could be caused by. So, what I was wondering about with microplastics is it is if that was a concern when you're using this plastic in the asphalt, if it would generate little tiny pieces of plastic debris that would then get into, like you said, stormwater or other runoff or even into the air. So I can understand that. Being a concern.

00:05:17 KRISTI: I think yeah, it's mostly we're checking that nothing that we're putting into the road comes out again. And especially since our stormwater goes straight into the ocean, I think that would also be a bigger concern for us also because we know anything that goes in there will come out to. The ocean, so.

00:05:33 BRIAN: Yeah, absolutely. I mean, you're putting all this effort into cleaning up the ocean by getting rid of some of these plastics. You don't want to put it back in. So, let's talk about performance now. One of the challenges, Mel, that you mentioned. And was that this material needed to meet the standards for resilience, right. So, we wanted to have a long lasting product that performs well. So do you think the selection of the product that you're trying right now at the criteria?

00:06:07 MEL: I think we do. Actually we have a team of people working together to set up the best testing protocol to make this, you know, a better choice. So we have industry partners, we have a contractor, we have UH for mechanical testing. We have another university, HPU for microplastic testing. So, we work together. To come up with a protocol, how we going to do that? So for the pre-construction we have our contractors to. Do some lab performance testing before it lay down to the road and Kristi can talk more about that.

00:06:42 BRIAN: You know, one of the things that I talk about on the podcast sometimes is how DOTs are very service oriented. They're trying to solve problems that help people live better lives, and they do make great efforts to engage with other interested parties and partners to. Come up with optimal solutions. So, I think that what Mel was just saying is a great example of that, that I wanted to highlight. Now Christie's time to put you on the hot seat. Let's talk about how the plastic has been incorporated into the asphalt mixture.

00:07:16 KRISTI: So, the product that we're using is made out of pellets. So, when they get shipped in, they I think they got boxes of pellets. And the way that it's getting incorporated into the mix is at the asphalt plant. They are feeding it through the fiber machine. So, the I think the SMA mixes uses the fiber machine so in that machine that's where they are using plastic pellets.

00:07:40 BRIAN: OK, so the plastic pellets are entered into there and then what happens?

00:07:44 KRISTI: The aggregate will have already been added, so I think it gets added in. Hopefully it melts into the binder and comes out with the homogeneous mix.

00:07:53 BRIAN: So, for those of you who are not involved in asphalt mixtures, you've got this big drum mixer and all this material is being shot into it, fed into it, and then it's heated and mixed and then out on the other end, you've got what looks like, you know, the finished product of the asphalt mix. So, this was mixed together. And what kind of test? Did you perform or your department perform on these materials to give you the confidence to say that it's going to meet the criteria for resilience that's been set forward?

00:08:28 KRISTI: In our typical procedure, we are usually only volumetric kind of testing right now, so we use the Marshall design. But in this case, I think we wanted to find a way, like most was saying that to find a way to, to be comfortable, that their performance would be similar and our partner with the industry and the contractor we came up with an idea that we would check out like we'll try to do some of the performance testing. So, we would do performance testing on our control mix. And the mixes with the plastic added and just kind of compare them like as our first foray into performance testing.

00:09:02 BRIAN: OK, so for those who do not know what performance testing is, what tests are those?

00:09:07 KRISTI: The ones that we chose for reading, we decided to use the Hamburg. So, the Hamburg, they take the compacted material and they put it into the machine and they have a wheel that rolls over it like multiple times and it checks like how much it deforms after so many passes. And for cracking, we went with the ideal CT.

00:09:29 BRIAN: So now a lot of people might not be familiar with the ideal CT what is that test? Uh, it's an indirect tensile cracking test. For asphalt, so. So, it's a way to find the cracking potential and at least compare it against the other ones. OK, so we've got running and we've got cracking as performance. So that'd be different than you mentioned volumetrics before, where you're mainly concerned about the density and air voids.

00:09:56 KRISTI: The air voids and we check all of the aggregate properties in there also.

00:10:02 BRIAN: OK, so we've got these performance tests and what was your conclusion after running tests on this material? So again, we were just looking at it kind of like a comparative. So, after looking at it and we met with the other people on our team, so we had. The contractor, the industry partner I'm with. HAPI and with the university. So, I think we all felt comfortable moving forward with the project.

00:10:29 BRIAN: For those of you who don't know, who is HAPI?

00:10:33 KRISTI: HAPI is our Hawaii asphalt paving industry.

00:10:36 BRIAN: OK. So that's the asphalt paving association for Hawaii, right? Yes, that's another one. So, the DOT's typically do partner with the paving associations. A lot of things. There's usually some engagement and cooperation with the paving industry, so that's always good to hear your goal. As what Mel talked about earlier was getting to the point where you can process this material. In Hawaii, were there other materials that you also ran through performance testing with before you ended up with this product?

00:11:11 KRISTI: No, actually we only tested this one first. One of our main goals was also to look for the US. So, the other products that we had found were from out of country. So, we just tested with this one came out good. So, it's good to go.

00:11:25 BRIAN: Yeah, that's good. And then did you also perform volume metrics on these? OK. And was that comparable to what you expect?

00:11:32 KRISTI: Yeah, they all went through our biometric check first before we went to the performance testing.

00:11:38 BRIAN: Did you also perform any testing in the field or is that up to the contractor? As far as like densities are concerned?

00:11:45 KRISTI: We did our normal like quality assurance kind of testing. The contractor did their own QC tests and then our QA test is we're like compaction. So, we took some courses and the rice. But other than that, that part was up to the contractor. We are doing some additional testing for performance with our university. So uh. Is doing the same performance testing with mix that we collect production, so they're using the production mix to make the specimens to do the performance testing.

00:12:15 BRIAN: Now, Mel. I want to go back to you. What's next? Are you looking to expand the use of this material or try other materials?

00:12:23 MEL: Definitely we want to expand it, but first it's going to make sure that the performance test is OK and there's no microplastic leaching, right? So after that we need to move to. The next step is find a way to use local waste. To the local Rd. we are going to work on the next research project and actually get some climate challenge grant money try to establish a research facility to do that. So hopefully in the future it become more and more popular so we can use more waste on our Rd.

00:12:55 BRIAN: Do you know how long you'll be collecting data before you can try the next step?

00:12:59 MEL: OK so. So, I think we'll have the data ready in the next six months. So, for the right now the microplastic leaching we depending on when you age during the performance test, we'll collect the water and give it to HP UHP will filter that. So the water portion will go to our microplastic. Testing and then the solid portion will goes to UM plastic additive testing. Once we make sure everything is OK, then we'll be good. Oh, that's one more. So, after three months after the construction. Where's the road has? Been used fairly used. And then HP is going to do a simulated rainfall and to collect the storm water, right and then to test it also. So, we want to make sure that there's no additional microplastic reached to the role because a lot of microplastic actually come from the tire itself, not the roll, right. So, we want to make sure that they have a fair comparison once we make that clear. We should move forward to the next step, which is going to be very, very challenging but like, but how you deal excited for the next step.

00:14:03 BRIAN: Yeah, that sounds great. Kristi and any last thoughts from you?

00:14:06 KRISTI: No, I agree with that. It's exciting.

00:14:09 MEL: So yeah, hopefully we can use the plastic beyond.

00:14:09 BRIAN: All right. Oh well, sorry. Now I have to ask you that. What else are you? What else are you thinking of?

00:14:17 MEL: So I have heard that the plastic could be incorporated into the concrete so that could be the next one that we're going to think of. But then, first of all, let's get our local pass rate on to our local AC people first and then we try to have more innovative solution for our other material on our infrastructure.

00:14:40 BRIAN: Yeah, that sounds great. I know a lot of people are trying to put waste in the roads. I think that has been easier maybe or an easier thought process for people because you're already putting kind of plastic-based additives into asphalt mixtures. And so, I think that. It seems like there's some easier transition, I guess, like for the industry, the idea of incorporating that plastic in there. But have you heard anything metal, any resistance or any concerns about moving forward in this direction?

00:15:16 MEL: Sure. That's concerned. I mean, it's just the fact that we cannot have 100% people support what you're doing, but we believe this is the right step and we try our best to do testing before the construction during the construction and after the construction. And we want to document it well. So we have a case to back up. What is? And then we also want this piece of document to be useful for maybe our county may want to consider to use it and maybe others are still looking at our study, maybe they will decide to, you know have more confident using this material. So too. So, this is our administration push for us to do a good research in order. You know for. Hawaii is very small. We don't have that much mileage of Rd. But then we want to see, you know, do our part. Maybe we can encourage other states to take, give it a try.

00:16:07 BRIAN: Yeah, that sounds great. I did want to ask you because so why you so small? Hawaii, do you too is responsible for maintaining some roads? Right. And then you've got county and you've got city, but how much does the dot maintain compared to counties and cities in Hawaii?

00:16:27 MEL: Most of the. Roads are owned by the city and county and other counties, so State Road I believe we are managing about. Well, a little over 3000 miles is not a lot, but the county has a bigger portion. So, in order to have a bigger impact, we should vote it.

00:16:44 BRIAN: Yeah, for sure. Well, I would like to thank you for your time today. Again, we had Mel Chung and Kristi Grillo appreciate your time today.

00:16:53 MEL: Thank you for having us. Thank you.

00:16:55 KRISTI: Yeah. Thank you.

[Musical Transition.]

00:16:58 KIM: And this was Part 2 of a four part series on paving with recycled plastic, Hawaii's pilot project. If you missed last week's episode, I recommend you check it out. It'll give you some good context.

00:17:11 BRIAN: That's right. And next week we've got John Young from Hawaii Asphalt Paving Industry are HAPI to give the industry's perspective on this project.

[Theme music fades in.]  

00:17:20 ANNOUNCER: Thanks for listening to AASHTO re: source Q & A. If you'd like to be a guest or just submit a question, send us an email at podcast@aashtoresource.org or call Brian at 240-436-4820. For other news and related content, check out AASHTO re:source's social media accounts or go to aashtoresource.org.