Demonstration 3:

Effect of Aggregate on Workability of Concrete

Objective: The purpose of this demonstration is to determine the effect of different aggregates on the workability of the resulting concrete.

Materials and Supplies:

• cement
• two containers labeled:
  • "limestone chip aggregate"
  • "sand aggregate"
• water
• small limestone chips(pea gravel)
• sand

Procedure:

1. Add 1 part of cement and 1/2 part water to each container. Suggested amounts include 50 grams of concrete and 25 ml of water.
2. Mix to make the cement paste.
3. To the appropriate container, add 3 parts (150g) of limestone chips and mix.
4. To the second container, add 3 parts (150 g) of sand and mix.
5. Using gloved hands, knead the concrete to determine its workability.
6. Which concrete mixture is more workable? Why?

Expected Results:

The sand aggregate is more workable, because the smaller particles facilitate flow. The larger particles of the gravel hinder it.