Compaction Test

Objective

Understanding the relationship between water content and dry unit weight in different soils is important for engineers.  Plotting a range of water contents and dry unit weights provides the optimum water content and maximum dry unit weight of the soil.

Procedure

For this laboratory compaction test, the standard compaction method was used. The standard compaction test uses a standard proctor device to compact three layers with 25 drops per layer.  The soil is compacted in a mold that consists, of a base plate, main mold, and an extension collar.  All of the parts of the molds should be cleaned before the test ensues.

Once cleaned the base plate and main mold should be weighed. Assemble the mold so that the extension collar is securely fit to the main mold and screwed down to the base plate.  Pour soil into the mold until the mold is two thirds full.  Compact the soil by dropping the weight in the proctor device in a cross-circular pattern. Drop the weight 25 times for this layer.

A second layer and third layer should be compacted until the compacted layers are even with the main mold.  Remove the extension collar from the main mold.  If the soil exceeds the height of the main mold trim the excess soil so that it’s even with the main mold. Weigh the main mold, base plate, and soil.

Weigh and record the mass of three moisture cans. Take three samples of the compaction, one of each layer of soil.  Put a sample in each can and measure the can and soil’s mass.  Put the three samples in the oven and let them dry for approximately 24 hours.  Once dried measure the mass of the moisture can and samples.