Research Projects

Using Recycled Carbon Fibers in Electrically Heated Pavement

Establish if and how recycled (pyrolyzed) carbon fibers can be used in place of virgin carbon fibers for achieving comparable performance at lower material costs.

Background (Describe the current situation or problem in the industry, and how your idea would address it.)

Many US airfields experience snow, ice, or slush in the winter time. Less than perfect conditions of runways or aprons lead to slower, less efficient and less safe operations. Typical removal practices are costly, time consuming and can have environmental and corrosive impacts.
Heated Pavement Systems (HPS) are offering an alternative. Of the different types available, Electrically Conductive Concrete (ECC) has proven to be a viable approach (Sassani et al., 2018). In general, ECC consists of cement, sand, aggregates, water, additives and an electrically conductive component. Among various other possibilities (metallic wires or particles, carbon based powders, carbon nano materials), short carbon fibers (CF) have proven to be the best performing conductive material in terms of effectiveness, non-corrosiveness, installation and operating costs. They also improve other concrete properties such as compressive strength, tensile strength, and fatigue cracking.
Of those, typical PAN-based carbon fibers with diameters of up to 15 μm and lengths of up to 6mm have proven most effective, with aspect ratios of about 430 being sufficient. Typically used in volume dosages below 1%, their cost nevertheless has a big influence on the overall economics of any HPS. The to date most successful, or at least most tested, formulation uses a combination of nominally 70% 6mm and 30% 3mm virgin carbon fibers. In practice, the mixing process is sure to diminish the actual fiber length distribution. The price range for contracted and regularly available volumes of short, standard modulus carbon fibers is around $8 - $12 per lb.

If processed properly, recycled (pyrolyzed) carbon fibers can be produced with minimal reduction of their actual fiber properties, and costs under $3 per lb (per Modern Recovery Systems, Inc.). However, while their average length can be controlled, it is never entirely consistent, and rather a length distribution around a median. But it stands to reason that recycled fibers with the right average length will match the conductive performance of virgin fibers, and at a much lower total cost, even if the actual quantity of fibers should need to be somewhat higher.
In practice, the challenge will be to find the optimum combination of average length and quantity of recycled fibers, since neither amount nor length of fibers in concrete mixtures can be increased indefinitely without affecting its workability.

Objective (What is the desired product or result that will help the airport industry?)

Establish if and how recycled (pyrolyzed) carbon fibers can be used in place of virgin carbon fibers for achieving comparable performance at lower material costs.

Approach (Describe in general terms the steps you think are needed to achieve the objective.)

Review latest carbon fiber & cement application practices and research. Focus on formulations, mixing
technology and mixing sequences

Develop an experimental plan to compare effect of using various recycled (pyrolyzed) carbon fiber samples vs.
virgin carbon fiber (3mm and 6mm)

Conduct experimental work

Develop a use profile of how to substitute recycled for virgin carbon fibers (less than 6mm) in cement applications

Cost Estimate and Backup (Provide a cost estimate and support for how you arrived at the estimate.)

Estimated problem funding: $180,000

Related Research - List related ACRP and other industry research; describe gaps (see link to Research Roadmaps above), and describe how your idea would address these gaps. This is a critical element of a synthesis topic submission.

Electrically conductive pavement as a solution for de-
icing systems is currently being investigated.
Early work was conducted by Tuan, incorporat
ing conductive concrete to develop a deicing concrete pavement for a
bridge deck (Yehia et al., 2000). The system was implemented in Nebraska and tested. At the Iowa State University a
research team led by Halil Ceylan is currently researching electrically
conductive concrete heated pavements with
promising results. (Abdualla et al., 2016). They conclude that short carbon fibers (3mm
-6mm) are superior to all
other alternatives, but that construction costs, especially the costs of the conducting component, a
re critical for
overall feasibility (Sassani et al., 2018).
Carbon fiber composites are being recycled in different ways, however, the only method which is capable of
extracting clean, raw fibers from all types of wastes and polymer matrixes (regardless o
f their curing stage), is
pyrolysis (Oliveux 2015). When processed optimally, the recovered fibers maintain their original fiber properties
(Boulanghien 2013).
Abdualla, H., Ceylan, H., Kim, S., Gopalakrishnan, K., Taylor, P., and Turkan, Y., (2016), "System Requirements
for Electrically Conductive Concrete Heated Pavements", Transportation Research Record: Journal of the
Transportation Research Board, No. 2569, Transportation Research Board, Washington, D.C., 2016, pp. 70–
79. DOI:
Boulanghien, M., Mili, M.R., Bernhart, G., Berthet, F., and Soudais, Y., (2013), "Fibre characterisation of steam
thermal process recycled carbon fibre/epoxy composites", The 19th International Conference On Composite
Materials,. Jan 2013, France.
Derwin, D., Booth, P., Zaleski, P., Marsey, W., and Flood, W. (2003). "Snowfree Heated Pavement System System
to Eliminate Icy Runways," SAE Technical Paper 2003
- 2145
Federal Aviation Administration, (FAA). (2011). "Airside use of heated pavem
ent systems." Advisory Circular
17, Washington, DC.
Oliveux, G., Dandy, L.O. and Leeke, G.A. (2015), "Current status of recycling of fibre reinforced polymers: Review
of technologies, reuse and resulting properties", Progress in Materials Science, vol 72 (2015), pp. 61-
Sassani, A., Ceylan, H., Kim, S., Arabzadeh, A., Taylor, P. C., and Gopalakrishnan, K. (2018). "Development of
Carbon Fiber
-modified Electrically Conductive Concrete for Implementation in Des Moines International Airport".
Case Studies in Construction Materials, 8: 277-
291. DOI: 10.1016/ j.cscm.2018.02.003.
Yehia, S., Tuan, C.Y., (2000), "Thin Conductive Concrete Overlay for Bridge Deck Deicing and Anti
-Icing", Transp.
Res. Rec. J. Transp.
Res. Board. 1698 (2000) 45–53.



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