Proctor-Compaction-Density by Sand Cone Method


The Proctor compaction test is a laboratory geotechnical testing method used to determine the soil compaction properties, specifically, to determine the optimal water content at which soil can reach its maximum dry density. The original test is offren reffered to as Standard Proctor Test, which was later modified and reffered to as Modified Proctor Test. The difference between the two tests lies mainly in the compaction enegry.


The Proctor compaction test consists of compacting soil samples at a given water content in a standard mould with standard compaction energy. The standard Proctor test uses a 4-inch-diameter mould with the compaction of three separate layers of soil using 25 blows by a 5.5 lb hammer falling 12 inches.In the Proctor test, the soil is first air dried and and then separated into 4 to 6 samples. The water content of each sample is adjusted by adding water (3% – 5% increments or more depending on the type of the soil).

The soil is then placed and compacted in the Proctor compaction mould in three different layers where each layer receives 25 blows of the standard hamer. Before placing each new layer, the surface of the previous layers is scratched in order to ensure a uniform distribution of the compaction effects.

At the end of the test, after removing and drying of the sample, the dry density and the water content of the sample is determined for each Proctor compaction test. Based on the whole set of results, a curve is plotted for the dry unit weight (or density) as a function of the water content. From this curve, the optimum water content to reach the maximum dry density can be obtained.


There are many types of Soil compaction tests which are performed on soil. Some of these are :-

1) The Sand Cone Method
One of the most common test to determine the field density of soil is the sand-cone method. But it has a major limitation that this test is not suitable for saturated and soft soils

The formula used are
Volume of soil, ft3 (m3)=[weight of sand filling hole, lb (kg)] /[ Density of sand, lb/ft3 (kg/m3)]

% Moisture = 100(weight of moist soil – weight of dry soil)/weight of dry soil

Field density, lb/ft3 (kg /m3)=weight of soil, lb (kg)/volume of soil, ft3 (m3)

Dry density=field density/(1 + % moisture/100)

% Compaction=100 (dry density)/max dry density

Maximum density is found by plotting a density-moisture curve.