Spalling occurs when the reinforcing steel in concrete corrodes. The corrosion is caused by the ingress of salt and carbon dioxide into the concrete. When steel corrodes, the rust has a larger volume than the original steel and this expansion breaks the surrounding concrete. Concrete where spalling (carbonating) occurs must be chipped away and removed.
The damaged and rusted steel reinforcing needs to be repaired by cleaning away all corrosion down to bright, shiny metal.
Thereafter the steel needs to be painted with a corrosion resistant paint system. Inadequate cleaning, repair and painting, may lead to further contamination of the concrete. All concrete areas with a negative pH, mut be removed and repaired. The rpaired area is to be re-instated with a 5 star cement mixture.
Spalling is mostly evident on high rise buildings due to their higher exposure to the elements. It is most notibale on the Durban coast line as the salty sea air blows on shore and settles on the paint system. Some of the properties along the coast line are not mainted as regularly as they should be and as such the longer the maintenance cycle the higher the incident of spalling.
There are two major issues that spalling causes, the first is the potential risk to the integrity of the structure itself, therefore attending to the painting earlier on will prevent this from taking place. Naturally in the long term it is more cost effective to have a planned maintanance cycle and ensuring their is budgeting in palce for this.
The second issue is the risk associated with the plaster in the affected area working itself loose and falling from height. There has been incindents where chunks of plaster have fallen through neighbouring roofs, luckily without harm or injury to the tenants living there.
Eeastcoat Painting comes across this problem fairly often and are specialists in the repairing of spalling.