Carbon fiber reinforced mortar as an electrical contact material for cathodic protection

For a joint between old plain mortar and new mortar (which serves as an electrical contact material for cathodic protection of steel-reinforced old mortar), short carbon fiber addition to the new mortar was found to decrease both the contact resistivity and the new mortar's volume resistivity. Whether the new mortar contained fibers or not, the contact resistance was higher than the new mortar's volume resistance perpendicular to the contact and was lower than the new mortar's volume resistance parallel to the contact. In the presence of latex, the volume resistivity was 3.1 × 10⁵, 1.4 × 10³ and 1.2 × 10² Ω.cm and the contact resistivity was 5.9 × 10⁶, 2.7 × 10⁵ and 2.6 × 10⁴ Ω.cm² at fiber contents of 0, 0.53 and 1.1 vol. % respectively. Latex addition alone to the new mortar increased slightly both contact resistivity and new mortar's volume resistivity. All resistivities increased very slightly with curing age.