16.2. Cold Joints

Try these first

1. 1.

   What is a cold joint?

   Hint

   Think about the interaction between freshly poured concrete and already set concrete.

2. 2.

   List two consequences of cold joints.

   Hint

   Consider the integrity of connections between concrete layers.

3. 3.

   What happens when a cold joint occurs?

   • Concrete bonds well
   • Weak interface forms
   • No effect on strength

   Hint

   Consider the consequences of combining set and unset concrete.

4. 4.

   True or False: Retarding admixtures accelerate the setting time of concrete.

   • True
   • False

   Hint

   Think about the role of admixtures in concrete setting.

5. 5.

   A construction team is pouring concrete for a large foundation slab. Due to delays, the initial pour sets before the second pour can be made, resulting in a cold joint. Discuss the structural implications of this circumstance and suggest four preventative measures the team could implement.

   Hint

   Think about both timing and material choices.

6. 6.

   Evaluate the effectiveness of using retarding admixtures under different temperature conditions. How may temperature affect the setting time and the choice of these admixtures?

   Hint

   Consider how temperature influences chemical reactions.