PROBLEM
Xuzhou Railroad Bridge, which is 1080 meters long with 108 arches, was built in the 1980’s. Contamination of the concrete structure occurred over the years due to leaking of corrosive materials from trains. Corrosion of embedded reinforcement had led to deterioration of the structure. Inspections showed that over 50% of the bridge was in an active state of corrosion, leaving the bridge owner with two choices: replace all of the beams and rebuild the bridge, or repair with new technology. After extensive research and evaluation, repairs using MCI® products were accepted. The repair project started in 1999 and continued thru 2002.

APPLICATION
Areas in a state of active corrosion (corrosion potential less than – 350mV) were treated by removing all spalled concrete, cleaning rust from exposed rebar using proper tools and chemical rust removers, and applying MCI®-2020 to the repair sections. MCI®-2000 admixture was added to repair mortars, which were applied to the surface of rebar by brush, and then trowelled into repair patch areas. An application of MCI®-2021 sealer to the entire surface completed this part of the repairs. Areas showing corrosion potentials between –200mV to –350mV (50% probability of active corrosion) were treated by applying MCI®-2020 into cracks, sealing the cracks with a low viscosity epoxy, and finally, applying MCI®-2021 sealer to the entire surface. Areas showing corrosion potentials higher than –200mV (less than 10% probability of corrosion) were treated with an application of MCI®- 2020 followed by MCI®-2021 sealer.

CONCLUSION
Follow-up testing at 180, 270, and 780 days, respectively, after the repair showed that the corrosion potential in active areas was reduced dramatically. The corrosion current density, Icorr , decreased from an Icorr>2.0 mA/cm before treatment to an Icorr = 0.17 – 0.15 mA/cm after treatment, effectively controlling corrosion.

PRODUCT
MCI®-2000
MCI®-2020
MCI®-2021