Extending the Lifespan of Decorative Concrete

Summer is the time when decorative concrete shines, and concrete contractors are busy laying and stamping elegant patterns on sidewalks, patios, driveways, and pool surrounds. But what happens to the beautiful natural stone, brick, and other decorative concrete patterns imprinted into the surface when, a few years later, rain, snow, and repeated freeze-thaw cycles take their toll, leading to cracks, weathering, and ultimately corrosion of the reinforcement as well as further cracking? Forward-thinking planning and preventive maintenance using migrating corrosion inhibitors and silane impregnations can significantly help increase the longevity of textured concrete without altering its decorative appearance.

Corrosion-Inhibiting Admixtures

Concrete contractors can give their customers a head start by recommending the use of a Cortec MCI admixture in decorative concrete projects that contain reinforcing steel or wire. MCI admixtures are generally more cost-effective than epoxy-coated rebar for corrosion inhibition and can be added to the concrete mix without the setting-accelerating effect of calcium nitrite (CNI) admixtures, according to the supplier. This is particularly important for work crews who need sufficient time to imprint patterns into the concrete surface before it hardens. MCI-2005 NS is a version with normal setting behavior, while MCI-2005 delays setting. Both have demonstrated good workability during mixing.

The routine application of sealants is an essential part of the process to reduce staining, water penetration, and other harmful effects. Corrosion protection for embedded reinforcing steel can be further enhanced by adding a combined penetrating sealer and surface-applied corrosion inhibitor (SACI) such as MCI-2018. This 100% silane-based penetrating sealer is well-suited for surfaces where there is a risk of slipping. MCI-2018 is available in both a standard formulation and a version for vertical surfaces and overhead areas, and can be applied to decorative concrete without altering its appearance, making it equally suitable for the restoration of historic structures as well as for decorative concrete.

Selecting the Right Penetrating Sealer

The molecules of MCI-2018 penetrate the pore structure of the concrete, chemically react with the cementitious substrate to re-
duce the penetration of corrosive agents, and form a protective, corrosion-inhibiting layer on the surface of the reinforcement. If only a penetrating sealer is desired, MCI-2018 X provides the same penetration without the migrating corrosion inhibitors. It is recommended to repeat this application every seven to ten years, or more frequently if necessary. For surfaces that have previously been treated with a penetrating sealer, MCI-2019 (with migrating corrosion inhibitors) and MCI-2019 X (without migrating corrosion inhibitors) are variants with a 40% silane content, which reduce the effort required for surface preparation to remove residues from the previous application of the impregnating agent.

Decorative concrete is an excellent alternative to paving stones for achieving the aesthetic appearance of stone floors and masonry. One trade-off, however, is the importance of maintenance, including special protection against moisture penetration, freeze-thaw cycles, and corrosion, which can lead to further cracking. Incorporating MCI admixtures is an excellent way to give decorative concrete a head start with additional corrosion protection, while routine maintenance can be improved through the use of two-in-one MCI/silane surface treatments.