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
- Place 5 cm of aggregate in the container.
- Fill the container with water so the water level is 2 cm above the aggregate.
- Shake vigorously for 1 minute, making the last few shakes in a swirling motion to level off the aggregate.
- It is suggested that this demonstration be done twice, once with sand and once with kitty litter to obtain various results.
- Allow the container to stand for an hour, or until the liquid above the aggregate is clear.
- 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.
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.