Galvanic protection against reinforcement corrosion safeguards Baltic centre for contemporary Art
Galvanic protection against reinforcement corrosion safeguards Baltic centre for contemporary Art
Keywords: Galvanising, Corrosion, Concrete
Baltic is the new international centre for contemporary art on the bank of the river Tyne in Gateshead. For structural engineers, Atelier One and main contractor HBG Construction Ltd, the £46 m transformation of the former Baltic Flour Mill into one of the North's premier attractions involved the creation of a new gallery space within the original skin of the 1950s structure.
In order to retain the original exterior, areas of concrete that had deteriorated due to reinforcement corrosion had to be first repaired. Working with Atelier One, Fosroc specified a tailor-made package using electrochemical technology to repair the damaged concrete and protect it against further reinforcement corrosion, safeguarding the building for future decades.
Baltic is located nearer to the north-east coast and, in addition to carbonation, the building has been exposed to chloride contamination, due to its location, resulting in spalling of the concrete ring beams. Chloride analysis revealed that contamination was particularly severe on the more exposed north elevation whilst the other three elevations contained only low to moderate levels of chloride.
Patch repairs to remove spalled concrete were first conducted by specialist contractor Hicote Ltd using Renderoc HB, a concrete reinstatement mortar from Fosroc. The repair was completed with Renderoc FC, a cementitious fairing coat which was used to fill blow holes and imperfections in the concrete prior to coating with Dekguard Elastic, a decorative, elastometric anti-carbonation coating.
On consultation with the project engineers Atelier One, what had originally been purely a repair project was extended to include the installation of galvanic protection using Fosroc's Galvashield anodes.
Patch repairs in chloride contaminated concrete can induce secondary corrosion immediately adjacent to the repair area. Galvashield XP comprises a sacrificial anode unit encased in a specifically formulated mortar which when attached to the reinforcing steel prevents the transfer of corrosion. Galvashield XP anodes were placed in the patch repairs on the three less exposed elevations to stop corrosion spreading to surrounding areas.
On the more exposed elevation, Galvashield CC sacrificial anode units were placed along sections of the ring beams, where testing had indicated a high risk of corrosion. The Galvashield CC system also uses zinc encased within a highly alkaline cementitious mortar and is designed to control the corrosion in, as yet, undamaged concrete. The system is interconnected with wire in a grid pattern and installed into pre-drilled holes over the whole, or part, of a structure. Galvashield CC can provide protection against corrosion of reinforced concrete for up to 20 years.
This package of products from Fosroc, addressing both patch repairs and preventing corrosion in sound concrete, will help to ensure that Baltic is looking at its best for years to come and will help to avoid the need for future costly and disruptive patch repairs.
