What types of sand can sand washing machines/sand washers wash?

Sand is widely used in construction, serving as one of the primary constituents of concrete and mortar, and is a bulk material in civil engineering. Sand is generally categorized into two types: natural sand and artificial sand. Natural sand is formed primarily through the action of natural conditions, such as the weathering of rocks, and consists of rock particles with a size below 5mm. Artificial sand, also known as manufactured sand or washed sand, refers to rock particles less than 4.75mm in size that have been mechanically crushed and sifted after being treated to remove soil. It does not include particles from soft rocks or weathered rocks. The specifications of sand are classified into three grades—coarse, medium, and fine—based on the fineness modulus (an indicator of the fineness and category of natural sand particles).

Coarse Sand: Fineness modulus ranges from 3.7 to 3.1, with an average particle size of over 0.5mm.

Zhong Sha: Fineness modulus ranges from 3.0 to 2.3, with an average particle size of 0.5 to 0.35 mm.

Fine Sand: fineness modulus ranges from 2.2 to 1.6, with an average particle size of 0.35 to 0.25 mm.

Extrafine Sand: Fineness modulus ranges from 1.5 to 0.7, with an average particle size below 0.25mm.

The higher the fineness modulus, the coarser the sand. The fineness modulus range for common concrete sand is 3.7-1.6, with medium sand being preferred. Alternatively, coarse sand can be mixed with a small amount of fine sand in a ratio of 4:1.

The particle gradation of sand refers to the proportion of different-sized sand particles. If the sand particles are of the same fineness, the voids are large. When sand particles of two different sizes are mixed, the voids are reduced. Mixing sand particles of three sizes further decreases the voids. Thus, the void ratio of sand depends on the gradation of different particle sizes. Well-graded sand not only saves cement but also enhances the compactness and strength of concrete and mortar.