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5 August 2014 Spalling a danger to properties, says expert

Areas with high moisture levels pose a threat to the structural integrity of buildings, especially along the Atlantic seaboard and west coast, with relentless rainfall, sea spray and high winds.

Water ingress can cause more than just leaking and peeling: it can lead to dangers associated with spalling, according to painting, waterproofing and construction company, Indawo.

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“Spalling is especially common in the Western Cape due to the high moisture in the atmosphere during the wet winters. A further leading contributor to spalling is the higher salt content in the atmosphere,” says Indawo managing director, Geoffrey Jäck.

“Cracks in building structures can often also be attributed to corrosion of the internal steel reinforcing bars. Unreinforced concrete’s tensile strength is relatively low compared to its compressed strength, so steel reinforcing is placed for high tensile strength inside concrete columns that are susceptible to high tensile forces, especially high rise buildings. Untreated damage to this steel can lead to the onset of early deterioration of a building’s structure.”

Spalling is a result of water ingress that reaches into the structures of buildings, causing surface peeling or flaking due to moisture in the concrete. This moisture, coupled with a high salt content that introduces chlorides into the concrete, pushes out from inside the structure while attacking the integrity of the steel reinforcing. This causes corrosion that breaks down the protective layer around the steel bars, weakening them, and leading to the destruction of the building’s exterior structure.

“As cracks expose more of the steel reinforcement, corrosion is exacerbated and the steel will deteriorate at an increasingly rapid rate. The more the steel corrodes, the weaker the building’s structure becomes and less reliance can be placed on the strength the steel originally provided. Left untreated, the steel reinforcement will lose its bond with the concrete and the structure may collapse under its own weight,” Jäck says.

“Spalling is a common maintenance problem and is more prevalent in older buildings. Bodies corporate, building owners and property managers need to be aware of the dangers of spalling in the Western Cape’s high rainfall, wind and sea spray regions. If identified and treated, the integrity of the building will remain unaffected.”

To prevent spalling, Indawo recommends appointing professionals to:

Seal cracks and holes as soon as possible to prevent prolonged exposure of any reinforcing steel.

Ensure that exposed steel is assessed for corrosion and treated.

Ensure adequate waterproofing on surfaces exposed to high rainfall, wind or sea spray.

Implement a maintenance programme that includes a painting plan tailored for specific weather conditions.

Ensure adequate sealing of holes when adding substructures such as tanks and satellite dishes to walls or roofs.

“Spalling repair is a time consuming, often difficult task. Identifying the source and extent of the damage requires extensive testing. This involves chipping away the concrete to expose the corroded steel reinforcing to ascertain the depth of the problem. The corroded steel needs to be scraped to remove all rust. Anti rust paint must be applied followed by a bonding agent to ensure proper adhesion to the concrete. Mortar is then re-applied over the steel before painting the surface, says Jäck.

“If ignored, the damage resulting from spalling may lead to larger more costly repairs and even building condemnation. Regular maintenance checks will allow you to identify problem areas early enough to treat the problem and maintain the structural integrity of the building.”

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