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Social housing scheme specifies Sika concrete repair system

28 Sep 11 Faced with significant structural damage caused by chloride penetration and subsequent corrosion of the steel reinforcement to a concrete beam on Wiltshire House, one of its seafront social housing blocks, Brighton and Hove City Council needed an innovative means of repairing damage and protecting the steel reinforcement.

They elected to use a range of high performance products from Sika, internationally prominent producer of building products, including its Sika Galvashield XP.

Engineering Design Associates, Consulting Engineer, specified the method of repair and the range of products to be used, choosing Sika for its market proven reliability, especially in coastal concrete repairs, and its range of corrosion management technologies. The repairs works to the 60s apartment block was overseen by main contractor Apollo Group.

The immediate threat to the structure was posed by the expansive corrosion of the concrete’s reinforced steel elements due to the chloride attack, causing spalling of the concrete. This led to significant lumps of concrete falling to the ground below, posing both a health and safety risk and a structural hazard.

To ensure that there would be no further corrosion of the steel, Sika Galvashield XP was installed following the removal of the concrete around the reinforcement. The small circular disc shaped Sika Galvashield XP is then connected to the steel reinforcement. Containing a zinc galvanic anode connected to reinforced steel by wire ties, it corrodes sacrificially to the steel, extending its lifespan by delaying the onset of further corrosion.

This simple solution provides cost effective and focused protection to reinforced concrete elements. With no need for maintenance and easily installed as part of a concrete repair strategy, the product is a key weapon in the Engineer’s constant battle to manage corrosion of reinforced concrete structures.

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For this project Sika’s Galvashield technology was within areas where structural damage had already occurred and need to be repaired. Elsewhere, as part of a package of corrosion management measures employed on this project Sika Ferrogard 903 was applied to slow down corrosion and reduce the likelihood of any further structural damage being caused. This spray-applied corrosion inhibitor both slows and delays the start of corrosion, extending the building’s structural concrete lifespan considerably. Easily applied, it impregnates concrete without altering either its external appearance or its vapour diffusion properties.

To repair damage to the substrate, Sika’s Monotop concrete repair system was used. Exceeding the requirements of BS EN1504, the regulations for concrete repair and protection, this comprehensive two component system uses polymer modified mortars containing silica fume applied “wet-on-wet” to ensure no degradation of the concrete or the steel beneath.

With the coastal climate of key concern to the longevity of the concrete beam, a final layer of SikaGard 550W Elastic was applied to the repaired areas A water-based elastomeric protective coating for concrete, its elasticity gives it crack-bridging properties and ensures that the concrete will be protected from freeze-thawing. Also meeting the requirements of BS EN 1504 this highly durable coating provided the final touch of protection for Wiltshire House.

The use of this range of Sika products provided an innovative solution for the repair of the failing concrete beam. In particular, the use of Sika Galvashield XP gave engineers the chance to significantly combat the effects of chloride contamination and ensure the future integrity of the load bearing concrete.

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