Concrete defects

Question 1

How is concrete tested?

Answer 1

Cube test
- A sample of concrete is placed in a cube, cured and then compressed in a lab.

Rebound hammer
- A spring releases a plunger to strike the surface of the concrete. The rebound distance is then measured and correlates the concretes strength

pull out test
small metal rod in concrete
pull it out for compressive strength

Question 2

What are some common concrete defects?

Answer 2

Cracking
- can be from curing
- incorrect mixture
- shrinkage
- overloading

Honeycombing
- Structural defect caused by the failure of mortar to effectively fill the spaces between the coarse aggregate particles.

Carbonation
- It is a chemical process between carbon dioxide and calcium hydroxide react.
- Starts on the surface of concrete and makes its way to the inner part of the concrete
- Carbonation lowers the PH of the concrete
- This can cause the protective layer around the steel reinforcement to brake down and begin to corrode.
- as it rusts it creates more volume and concrete can spall off or cause cracking.

Question 3

How can you treat carbonation?

Answer 3

Hammer test to establish loose concrete

Hack of loose concrete

grit blast to remove corrosion and other deposits

Apply a bar primer to the surface face of the reinforcement

Patch repair using a cementitious material, sand and polymer dispersion

or

can use an anode to pass an electrical current to the reinforcement and apply an alkaline electrolyte to the surface of the concrete