Rolling Test and Dispersion Test for Differentiating Silt from Clay Soil

In our previous posts we have learnt about shaking test and strength test for differentiating silt from clay. Now we will discuss about rolling test and dispersion test. We have already learnt about methods for differentiating silt from sand. These two tests we will discuss are very simple test and can provide an rough idea about presence of silt and clay, in soil sample.

Rolling Test:

In this test, a thread of about 3 millimeter diameter is tried to make with moist sample.

If soil sample is silt-

Crumbling and disintegration is observed while making thread, in a word, the faulty thread is formed.

If soil sample is clay-

Thread can be made easily without disintegrating and any other fault. A thread of about 300 millimeter in length can be produced.

The most interesting is that the thread can support self weight without disintegration even when make it suspended holding its ends. This test is also known as toughness test.

Dispersion test:

In this test a jar is filled with water and a spoonful sample is poured into water from top.

It this is silt-

The soil particles take about 15 mins to an hour to settle completely.

If this is clay-

A suspension is formed, that will hold its previous position up to hours to even days, but no flocculation is observed.