Polyurethane-carbon microfiber composite coating for electrical heating of concrete pavement surfaces

Abstract

Electrically-heated pavements have attracted attention as alternatives to the traditional ice/snow removal practices. Electrically conductive polymer-carbon composite coatings provide promising properties for this application. Based on the concept of joule heating, the conductive composite can be utilized as a resistor that generates heat by electric current and increases the surface temperature to melt the ice and snow on the pavement surface. This research investigates the feasibility of applying an electrically conductive composite coating made with a Polyurethane (PU) binder and micrometer-scale carbon fiber (CMF) filler as the electrical heating materials on the surface of Portland cement concrete (PCC) pavements. PU-CMF composite coatings were prepared using different volume fractions of CMF, applied on the PCC surfaces, and evaluated in terms of volume conductivity, resistive heating ability, durability, and surface friction properties at the proof-of-concept level. A conceptual cost analysis was performed to compare this method with other heated pavement systems with respect to economic viability. Percolative behavior of CMF in PU matrix was captured and most desirable CMF dosage rates in terms of each performance parameter were investigated. Two percolation transition zones were identified for CMF in PU matrix at dosage rate ranges of 0.25-1% and 4-10%. The composites exhibited their most desirable performance and properties at CMF dosage rates greater than 10% and smaller than 15%.

Keywords: Carbon fiber; Civil engineering; Composite; Electrically conductive coating; Heated pavement systems; Materials science; Mechanical engineering; Polyurethane; Portland cement concrete.

Fig. 1

Specimens for determination of percolation threshold: (a) coating on wood substrate before application of silver paste; (b) coating on wood substrate with silver paste electrode; (c) coating on concrete substrate before application of silver paste; and (d) coating on concrete substrate with silver paste electrode.

Fig. 2

Concrete specimens coated with PU-CMF composite for resistive heating test.

Fig. 3

Schematic of the coating durability test set-up.

Fig. 4

Concrete specimens coated with PU-CMF composite and the test set-up for evaluating the (a) effect of loading cycle on mass loss, (b) effect of loading cycles-induced current flow path deterioration on electrical conductivity, (c) loading cycles-induced localized damage on electrical conductivity.

Fig. 5

Variation of volume conductivity with CMF dosage rate in the PU-CMF composite coatings.

Fig. 6

Thermographic images of coatings with (a) 0.25–1.5%, (b) 2–7.5%, and (c) 10–20% CMF dosage rates on wood substrate after 1-minute current application.

Fig. 7

Average surface temperature rise of coatings on wood substrate at CMF dosage rates (a) below and (b) above the lower limit of second percolation transition zone after 1 min of current application.

Fig. 8

Average temperature rise on the surfaces of coated concrete specimens at different durations of electric current application.

Fig. 9

Infrared thermal images after 3 min of electric current application for concrete PU-CMF-coated specimens at CMF dosage rates of (a) 3%, (b) 6%, (c) 7.5%, (d) 10%, (e) 12.5%, (f) 15%, and (g) 17.5%.

Fig. 10

Mass loss of coatings with different CMF dosage rates. Coatings showing measurable mass loss at (a) all; (b) greater than 500; and (c) greater than 5,000 loading cycles.

Fig. 11

The changes in electrical resistance of coatings after 10,000 loading cycles for (a) coatings that experienced resistance increase, and (b) coatings that experienced resistance decrease.

Fig. 12

PU-CMF coatings with (a) 10%, and (b) 15% CMF dosage rates after 10,000 loading cycles.

Fig. 13

British pendulum test results for the control and coated concrete specimens.

Fig. 14

WBS of heated pavement system made of conductive coatings vs. WBS of ECON HPS (Created based on the previous study on economic performance of the ECON HPS [103]).

Fig. 15

Construction cost comparison among various heated pavement technologies (created based on the data obtained from literature [102, 103, 104, 127, 128]).