Conductive Concrete   

Achievements

Mix Design

1.     Use steel shaving of 20 percent per volume of conductive concrete as an upper bound; poor workability and surface finishability will result if higher volumetric ratios are used.  In addition, using higher ratios of steel shaving requires an increase in w/c ratio to improve workability, which consequently reduces the compressive strength of the mix.

2.     Use steel fibers of 1.5 percent per volume of conductive concrete as an upper bound; higher ratios will make mixing difficult and produce poor surface finish.

Properties Evaluation

The mechanical and physical properties of the conductive concrete mix were evaluated in accordance with the ASTM and AASHTO specifications.  The compressive strength, flexural strength, rapid freeze and thaw resistance, permeability, and shrinkage of the conductive concrete mix after 28 days have met the AASHTO requirements for bridge deck overlay.

Deicing and Anti-icing Experiment

1.   The potential hazards of using higher voltage to heat the overlay, and the voltage and current   going through the slabs, are below the safe threshold (48-volt) for a human being.

2.   Uniform temperature distribution and gradual temperature change were observed during testing.  No sudden temperature increase was observed eliminating the possibility of thermal shock.

3.   Stress due to temperature variation is in the range of 516 kN/m2 (74 psi) which is less than the tensile strength of the concrete (3100 kN/m2  (450 psi)). 

4.   Average power of about 591 W/m2 (55 W/ft2) was generated by the conductive concrete to prevent snow accumulation and ice formation.

5.   Energy cost is in the range of $0.7 to $1.0/m2 (0.065/ft2) per storm.   

6.   The deicing performance and the power consumption results showed that conductive concrete overlay has the potential to become the most cost-effective bridge deck deicing method.