Concrete Cancer – The Hidden Dangers!

“Spalling Concrete”

In layman’s terms:

Concrete reinforced structures incorporate steel re-bars during construction to strengthen the structure. Spalling is generally referred to when: The steel reinforcing (re-bars) in concrete structures is rusting. As it expands it weakens the structure and causes the concrete and plaster to delaminate.

Visual examples:

In more technical terms:

Corrosion Of Steel Reinforcement:

Corrosion is a change in the surface structure of material caused by external chemical or electrochemical attack.  (Rust)  

In the corrosion of metals two types of reaction are recognised:

  • Anodic processes (characterised by pitting of steel) and
  • Cathodic processes (characterised by rust formation)

Carbonation proceeds from the surface of the concrete inwards* Its rate of advance is determined by a number of factors, including:

  • The relative humidity of the atmosphere
  • The CO2 content of the air
  • The quality of the concrete.

The bottom line:

Once this process has started it will continue to weaken the structure over time. It is important to realise that these failures are aggressive in nature and should not be left to eventually undermine the structural integrity of you building. A specialist should be contracted to remedy these failures, as normal plaster repairs will not suffice. Various recognised Manufacturer’s have specific systems to treat and arrest spalling concrete.

How to go about it:

It is important to consult a specialist to determine the exact cause of spalling on your building and to recommend a suitable reinstatement strategy. Once the cause and specification has been established, competitive quotes can be obtained from specialist contractors to perform the necessary repairs and maintenance.

*Because this process is promoted by external factors the general maintenance and protection of plastered and painted areas (Building envelope) will act as prevention against spalling. This emphasises the role of correct maintenance and waterproofing of external surfaces.

General guidelines for the repair of spalling concrete.

EXPOSURE OF ALL RUSTED REINFORCEMENT BARS

REMOVAL OF RUST

PROTECTING REINFORCEMENT AGAINST RENEWED CORROSION

PATCHING AND RESURFACING

After this process normal preparation and repairs of substrates can continue prior to painting.
Normal plaster repairs will not remedy spalling failures.

Frederik Nel,
Curasure