What is concrete cancer and what causes it?

When concrete cracks, water penetrates through, causing the steel reinforcement deep inside to rust. 

Rusting steel then sheds its skin forcing the layers of rust to push away the concrete surrounding it.  

This results in large or small pieces of concrete falling away and allowing steel reinforcement to become even more corroded and may cause devastating wear on both the steel and the concrete.

Concrete Cancer (or spalling)  is caused by many factors including:

• Carbonation
• Moisture 
• Efflorescence (the build up of salt in cement)