Winter weather and freezing temperatures will soon mean that construction projects are delayed in many parts of the Northern Hemisphere. For concrete PT (post-tensioning) structures such as bridges or parking ramps, this delays the grouting that should be done as quickly as possible after the placement of bonded PT strands. Cortec MCI-309 is an outstanding solution to counteract corrosion during this critical period of grouting delays.
Corrosion and Grouting Delays
Grouting delays may range from a few days to several months depending on site conditions and circumstances, the severity of the temperatures, and weather. During delays, metal tendons that have been placed inside the PT duct but not enveloped in grout are exposed to oxygen, the potential ingress of moisture, and (depending on proximity to the sea) even chlorides. In the US, state and federal requirements typically call for corrosion inhibitor application if the waiting period is seven to 20 days or longer (each DOT has different requirements). While oil-based corrosion inhibitors offer some protection, they can have a negative impact on bond strength once tendons are grouted.
The Migrating Corrosion Inhibitor Advantage
The best option on the market for corrosion protection of PT tendons that have been installed but not grouted is MCI-309. This Migrating Corrosion Inhibitor powder is easily fogged through ducts using a low-pressure air hose and sandblast cup—no special equipment required. MCI-309 releases corrosion inhibiting vapors that diffuse throughout the entire void space. An attraction to metal allows the corrosion inhibitors to adsorb onto tendons, forming a protective molecular layer. When better weather comes, grout can be applied as normal without flushing the corrosion inhibitor out of the duct.
MCI-309 ‘Claims to Fame’
MCI-309 has been used in a wide variety of construction projects, ranging from the Samuel De Champlain Bridge in Quebec to the extradosed St. Croix River Crossing bridge near Cortec World Headquarters in Minnesota. It has been used in Washington, DC, for the Frederick Douglass Memorial Bridge Project and in the Middle East and Hawaii for non-winter-related grouting delays. Due to its migrating ability, MCI-309 can also be and has been used for corrosion protection in other void space applications, such as flex-float structures at the Round Butte Reservoir where painting hard-to-reach internals of the ballast areas was impractical and MCI-309 provided a much better alternative.
Get Ready for Winter Construction Delays
By planning now for possible construction delays this winter, contractors can be prepared with a stock of MCI-309 to protect PT strands that must be placed but cannot be immediately grouted. To learn more about MCI-309 specifics and how they apply to your PT project, contact Cortec today.