To the wonder and amazement of other people I must be one of the few Building Surveyors that admires and appreciates the styling, design and material choice of the modernist architecture of the 1960s. However as a building surveyor such buildings are also a challenge as there’s usually a wide variety of defects with both building materials and construction technologies. Every so often along comes an absolute shocker.

The building in question was a typical 1960’s concrete shopping centre with the usual flat roofs, raised walkways and underpasses. Over the years it had been changed around so many times it had been left with unusable space and adhoc shaped units. A number of the shops were empty and the whole shopping centre was pretty run down.

A multitude of defects were evident everywhere you looked, with the main concern being spalling concrete and corroded reinforcement with suspicions this was caused by the carbonation of the concrete. Putting aside the immediate Health and Safety issue represented by one particular loose section of concrete which could have quite easily dislodged and fallen onto a passerby causing serious harm if not death resulting in an area being cordoned off, an urgent remediation plan was clearly necessary.

Carbonation occurs when carbon dioxide in the atmosphere reacts and decomposes the hydrated products of the cement in concrete to form various carbonate minerals, the layer of concrete affected being known as the ‘carbonated layer’. If the steel reinforcement is within the carbonated layer the protection offered by the high alkalinity of the concrete is diminished allowing water and oxygen to penetrate the concrete and react with the steel causing it to corrode. As part of the corrosion process the steel expands resulting in the concrete spalling, thereby exposing the steel reinforcement to further deterioration which in time will lead to structural failure.

Immediate repairs to the concrete was clearly essential and this followed the process of identifying all loose areas of concrete, hacking this off to expose the steel reinforcement bars, grit blasting to remove corrosion, applying a proprietary primer to the surface of the reinforcement and finally undertaking concrete patch repairs using a cementitious material and sand, and a polymer dispersion. A long term solution to inhibit further carbonation would be to restrict the entry of carbon dioxide by applying a coating to the concrete which would act as a protective barrier.

Along with this work other defects, including water ingress and damp problems generally, were rectified and the development was given a lick of paint and new shop fronts providing the centre with the opportunity for another lease of life.

Toby Ware Bsc (Hons) MRICS