NEWS ALERT: Comparing Options for Rusted Rebars in Concrete Patch Repairs

VpCI Corrverter on Rebar

Concrete spalling happens when corrosion on embedded rebar expands so much that it causes the concrete cover to break and fall off. The only responsible response is to repair the gap and seek to slow down the corrosion process. But what are the best materials to use on the exposed rusted rebars? Here is a look at two popular options.

  • 3K Bonding Agent

One commonly used product is a 3K material containing epoxy, corrosion inhibitor, and a bonding agent. These components are mixed and applied to clean metal reinforcement before the application of repair mortar. The coating works as a “glue” to bond the rebar or old concrete to the new patch material while also inhibiting corrosion on embedded reinforcement.

  • CorrVerter® MCI®

CorrVerter® MCI® Rust Primer is a single component water-based primer that converts rusted surfaces to a passive layer using a combination of chelating agents and a high solids waterborne latex with extremely low water vapor permeability. It can be applied to rusty rebar and patched with a concrete repair mortar once the primer has dried.

Some of the key differences between the two products are summarized in the following table:

3K Bonding Agent CorrVerter® MCI®
Surface Prep
Clean, rust-free surface is required; this typically means sandblasting

Sandblasting is labor-intensive and cannot clean the back of the rebar

Sandblasting byproducts create an environmental concern and must be disposed of carefully

Application to corroded surface is okay if loose rust has been brushed away

Repair mortar can be applied directly over CorrVerter® MCI®—no bonding agents required

Treatment of the back of the rebar is feasible with brush application

Application and Disposal
Three components must be mixed together and used within 1-2 hours or discarded

Two coats needed, 2-3 hours apart

Workers have 8-16 hours in which they can apply repair mortar for maximum bonding effect

One component; only needs enough mixing to ensure solids are evenly distributed

One or two coats needed; second coat can be applied after 20-30 minutes

Unused material can be covered and used later

Workers should wait 12-24 hours before applying patch material; minimal impact on bond strength thereafter

While both repair methods are valid, CorrVerter® MCI® offers obvious advantages in terms of reducing waste and simplifying labor. Which do you prefer? Contact Cortec® to learn more about the CorrVerter® MCI® advantage for spalling repairs!

Keywords: concrete repair, concrete spalling, concrete repair mortar, concrete bonding agent, rust converter, Cortec, From Grey to Green, MCI, CorrVerter, rebar coating

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