IntermediateTopic 71 of 112Civil & Structural
Corrosion and durability
Chlorides and carbonation corrode reinforcing steel.
In depth
Chloride ingress and carbonation break down the passive layer on reinforcement, causing rust that expands and cracks cover. Other mechanisms: sulphate attack, ASR, freeze-thaw. Durability measures: low w/c, adequate cover, supplementary cementitious materials, coatings, stainless or epoxy-coated bars, cathodic protection.
Key points
- Exposure classes
- Service life models
- Half-cell potential survey
ExampleMarine structures need 50+ mm cover and dense concrete.
What is Corrosion and durability?
Chlorides and carbonation corrode reinforcing steel.
Why is it important to understand corrosion and durability?
Corrosion of reinforcement reduces the strength and durability of concrete, so durability design is needed for coastal and de-icing exposure.
What causes reinforcement corrosion?
Chlorides or carbonation break down the passive layer around the steel, and corrosion then expands and cracks the surrounding concrete.
What is concrete cover?
The thickness of concrete between the steel and the outer surface, which protects the reinforcement from corrosive agents.
How is Corrosion and durability used in practice?
Typical applications include specifying a cover depth for a bridge deck exposed to de-icing salt, protecting the reinforcement in a car park from chloride ingress and assessing carbonation depth in an old building before repair.
What should I learn before Corrosion and durability?
Study "Structural health monitoring" first (topic 70 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Corrosion and durability?
Exposure classes. Service life models. Half-cell potential survey.
Can you give an example of Corrosion and durability?
Marine structures need 50+ mm cover and dense concrete.
What comes after Corrosion and durability?
The next topic is "Repair and rehabilitation", which builds directly on this one.
How difficult is Corrosion and durability?
It is classed as Intermediate in Civil & Structural (topic 71 of 112). It is an intermediate topic. Work through the beginner topics in Civil & Structural first.