Masonry restoration

Corrosion control of beams and steel

Steel beams are found in constructions dating back to the mid-1900s. Iron beams replaced brick arcs over windows and openings, and were covered as before with mortar. The corrosion of this iron is now an important cause of damage on a vast amount of buildings. Both beams and fasteners for decorations are affected.

Rusty parts of the façade

The chemical and physical transition of steel/iron into rust (rusting/corrosion) when water is present increases the volume of the material. The corrosion process is so powerful that it pushes renders and bricks apart. The decaying process influences the mortar, and it might result in a residue that looks like soil. Fresh and/or uncarbonated mortars have a high pH and will inhibit this reaction, but lime mortars with their damp diffusion open properties and when fully carbonated will not provide any protection. Beams can be well preserved in a façade depending on the thickness (and type) of the renders protecting it. Looking at a façade you will often find bulging over windows and openings, indicating attacked and infected steel beams. Today, new beams are protected with a layer which inhibits corrosion. 

Clean, protect or replace the corroded beam.

Damaged wall

Identifying and examining all beams in the façade is important. Fasteners for decorations are also often infected with corrosion and, when first attacked, will cause a relentless, rapid decay of the façade. The beams must be evaluated to determine whether to replace or protect them. The guidelines are universal; not considering the age of the building but following the classifications set in current standards for concrete and steel repairs (EN...). If protection is chosen, cleaning with e.g. sandblasting on all affected sides down to pure, clean steel is necessary.

When the sought purity is obtained, a corrosion control product should be applied immediately to inhibit further corrosion. Follow standards and guidelines closely for such repairs. Depending on the construction, new renders are applied with the same strength and quality as the original. A transition from these pure CO2-inhibiting products to lime-based renders should be done with a reduction of cement content and strength.