Sand can be classified into three types based on grain sizes, as coarse, medium and fine.

The determination of these fractions is important since they affect the engineering characteristics and performance of sands as pavement layers in terms of plasticity, strength and bearing capacity.

The shape of sand particles affects its density and stability and overall engineering behaviour. Smooth rounded particles would offer less resistance to rearrangement than angular or elongated particles with rough surfaces

The desert sand is not used for construction works, because it does not satisfy the criteria or specifications required to be used as a construction material.

Let us now go into detail about, why the desert sand is treated as unfit for construction works.

The desert sand or the sea sand has the following 4 properties, that are against the construction norms.

They are,

1. Desert sand is round in shape.

2. They have a smooth surface finish.

3. The particle size of the desert sand is very fine.

4. They are slightly alkaline in nature.

1. Round shape:

The sand used for construction work should be angular in shape to densely pack with each other, leaving no space in between the sand particles. Most parts of the desert sand particles are round in shape, which creates voids in between them, having the weak interlocking capability.

2. Smooth surface finish:

The construction sand should have a rough surface finish to make a good bond strength with cement & coarse aggregates. The smooth surface of the desert sand does not fulfill these criteria, as it creates a weak bond strength in the concrete materials.

As you can observe in the above image. the construction sand particles are angular in shape having a rough surface texture.

3. Fine sand particles:

The particle size of the construction sand should pass the sieve analysis test to attain the required design strength. The fineness of desert sand does not allow it to be used in the construction work, as they fail in the sieve analysis test.

As the sand act as a filler material between the coarse aggregates, their size should be large enough to satisfy this condition.

4. Alkaline in nature:

The concrete becomes weak in its strength when we use the sand having alkaline content in them. When the water evaporates in the desert region, they leave the salt content in the sand.

In the case of river sand, the salt, and other chemical impurities get washed away by the flowing water. The salt content also creates dampness & efflorescence in the building structures.

So, again the desert sand is declared unfit to be used in the construction works due to this reason.

The sea sand has the same characteristics similar to desert sand. The worst thing is, they contain more salt content when compared to the desert sand.