Large printed water drainage parts would speed repairs and cost less than conventional versions
By Geoff Giordano
Large-scale 3D printing is being evaluated to repair water-diverting highway culverts, according to Sunil Bhandari of the University of Maine, speaking in a virtual ANTEC® presentation on May 10. An experimental culvert diffuser will be installed in Maine in July and tested in October when the autumn rains arrive.
A conventional glass fiber-reinforced culvert diffuser (left) and an experimental 3D-printed version developed at the University of Maine. Courtesy of Sunil Bhandari/University of Maine
Failing highway culverts are costly not only in manufacturing and installation, but traffic interruptions. Diffusers can be used to rehabilitate culverts to maintain water flow.
“Culverts are usually rehabilitated by the slip lining process, which reduces the cross-sectional area and consequently reduces the discharge of the culverts,” Bhandari explains in an interview. “Culvert diffusers are used to increase the discharge via the venturi effect and hence compensate for the reduction in discharge capacity of the culverts due to the rehabilitation process.”
Current culvert diffusers are made with glass fiber-reinforced epoxy, says Bhandari, a PhD candidate in the university’s Civil and Environmental Engineering Department. By 3D printing diffusers, customized devices featuring geometries that conform to unique culvert dimensions and site conditions can be produced at far less expense, without the need for molds.
There are, however, some process-related issues. “Large-scale 3D printing has very high extrusion rates,” but “the feedstocks are usually pellets … which makes retraction operations more difficult and seams at the start and end point of material deposition more prominent.” It also takes longer for a layer to cool down enough to support the layer above.
Using the large-scale printer at the university’s Advanced Structures and Composites Center, Bhandari built an 8.5-foot-long by 2.5-foot-wide diffuser in four segments using a PLA (polylactic acid)/wood composite material. (The printer’s build area is 60 feet long by 22 feet wide by 10 feet high, with four heating zones.) The experimental diffuser features a round end connected to the failing culvert’s outlet and liner, while the opposite end has a flared opening 30 inches wide.
The four segments were printed in 8 hours, 41 minutes, totaled 410 pounds and were joined with Ashland’s Pliogrip 7770 urethane adhesive.
“The plan is to install the culvert diffuser at the Thorndike site in Maine during the dry season in July,” Bhandari says. “The performance of the diffuser will be measured during the wet season in October, when rainwater will increase the flow in the stream.”
Dialing in the optimal parameters for executing the project, Bhandari notes:
Layer times of 2 minutes, 30 seconds were not long enough to cool the material sufficiently to support the layer above, and layers collapsed. Layer times were increased to 4 minutes, 45 seconds.
Extrusion temperature was increased to 207°C from 200°C, resulting in a smoother surface finish.
Ultimately, a successful diffuser was printed for $2,500; a traditional glass fiber-reinforced diffuser costs $5,110. Bhandari asserts that extrusion rates can be tripled with existing equipment.
View on demand: Bhandari’s presentation “Large-Scale Extrusion-Based 3D Printing for Highway Culvert Rehabilitation” will be available on demand to ANTEC® attendees and those who register for access after the conference.
Kim McLoughlin Senior Research Engineer, Global Materials Science Braskem
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Kim drives technology programs at Braskem to develop advanced polyolefins with improved recyclability and sustainability. As Principal Investigator on a REMADE-funded collaboration, Kim leads a diverse industry-academic team that is developing a process to recycle elastomers as secondary feedstock. Kim has a PhD in Chemical Engineering from Cornell. She is an inventor on more than 25 patents and applications for novel polyolefin technologies. Kim is on the Board of Directors of SPE’s Thermoplastic Materials & Foams Division, where she has served as Education Chair and Councilor.
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Gamini has a BS and PhD from Purdue University in Materials Engineering and Sustainability. He joined Penn State as a Post Doctorate Scholar in 2020 prior to his professorship appointment. He works closely with PA plastics manufacturers to implement sustainability programs in their plants.
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Tom Giovannetti holds a Degree in Mechanical Engineering from The University of Tulsa and for the last 26 years has worked for Chevron Phillips Chemical Company. Tom started his plastics career by designing various injection molded products for the chemical industry including explosion proof plugs and receptacles, panel boards and detonation arrestors for 24 inch pipelines. Tom also holds a patent for design of a polyphenylene sulfide sleeve in a nylon coolant cross-over of an air intake manifold and is a Certified Plastic Technologist through the Society of Plastic Engineers. Tom serves on the Oklahoma Section Board as Councilor, is also the past president of the local Oklahoma SPE Section, and as well serves on the SPE Injection Molding Division board.
Joseph Lawrence, Ph.D. Senior Director and Research Professor University of Toledo
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Dr. Joseph Lawrence is a Research Professor and Senior Director of the Polymer Institute and the Center for Materials and Sensor Characterization at the University of Toledo. He is a Chemical Engineer by training and after working in the process industry, he has been engaged in polymers and composites research for 18+ years. In the Polymer Institute he leads research on renewably sourced polymers, plastics recycling, and additive manufacturing. He is also the lead investigator of the Polyesters and Barrier Materials Research Consortium funded by industry. Dr. Lawrence has advised 20 graduate students, mentored 8 staff scientists and several undergraduate students. He is a peer reviewer in several journals, has authored 30+ peer-reviewed publications and serves on the board of the Injection Molding Division of SPE.
Matt Hammernik Northeast Account Manager Hasco America
A Resin Supplier’s Perspective on Partnerships for the Circular Economy
About the Speaker
Matt Hammernik serves as Hasco America’s Northeast Area Account Manager covering the states Michigan, Ohio, Indiana, and Kentucky. He started with Hasco America at the beginning of March 2022. Matt started in the Injection Mold Industry roughly 10 years ago as an estimator quoting injection mold base steel, components and machining. He advanced into outside sales and has been serving molders, mold builders and mold makers for about 7 years.
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A conventional glass fiber-reinforced culvert diffuser (left) and an experimental 3D-printed version developed at the University of Maine. Courtesy of Sunil Bhandari/University of Maine 
