Demonstration 1:

Making a Silt Test

Objective: The purpose of this demonstration is to determine the viability of an aggregate based on a silt test.

Materials and Supplies:

• Sample aggregate (sand and kitty litter work well for comparison)
• Glass container with lid
• Water
• Ruler

Procedure:

1. Place 5 cm of aggregate in the container.
2. Fill the container with water so the water level is 2 cm above the aggregate.
3. Shake vigorously for 1 minute, making the last few shakes in a swirling motion to level off the aggregate.
4. It is suggested that this demonstration be done twice, once with sand and once with kitty litter to obtain various results.
5. Allow the container to stand for an hour, or until the liquid above the aggregate is clear.
6. The layer that appears above the aggregate is referred to as silt. Measure the silt layer. If this layer is more than 3 mm thick, the aggregate is not suitable for concrete work unless excess silt is removed by washing.

Video Clip

C. Expected Results:

The sand leaves a 3mm layer and therefore is a viable aggregate. Kitty litter, which is clay, leaves a thicker layer and is not a suitable aggregate.