Sand and gravel aggregate is widely used in building construction, road and bridge projects, hydroelectric facilities and other projects, and is one of the indispensable and important raw materials in infrastructure construction. You in the industry, you must have often heard others mention the terms coarse sand, fine sand, 12 stone, 13 stone, etc. What does this mean?

Stone-coarse aggregate

Aggregate with particle size greater than 4.75 mm belongs to coarse aggregate, also called stone. It is commonly divided into 5-1 stone, 1-2 stone, 1-3 stone, 2-4 stone and 4-6 stone.

5-1 stone

Represents crushed stone with a particle size of 5-10mm, commonly known as guamite.

1-2 stone

Represents gravel with a particle size of 10-20mm, mostly used in surface roads and concrete.

1-3 Stones

Represents gravel with a particle size of 16-31.5mm.

2-4 stones

Represents 2-4, international standard 1/4-1/2 inch gravel with a particle size of 10-15mm.

4-6 stones

represents four or six points, international standard is 1/2-3/4 inch, particle size is 15-20mm.

Four kinds of finished materials are common in sand and gravel aggregate production

1、Sand-Fine Aggregate

Aggregate with particle size less than 4.75 mm, fine aggregate, also known as sand. Common fine aggregate is divided into coarse sand, medium sand, fine sand and extra fine sand. Concrete use coarse sand and medium sand, plastering and jointing use fine sand. For ordinary concrete, medium sand is preferred.

Grain size and modulus of sand:

Coarse sand

The fineness modulus is 3.7-3.1, and the average particle size is 0.5mm or more, also known as large sand, 05 sand.

Medium sand

The fineness modulus is 3.0-2.3, and the average particle size is 0.5-0.35mm.

Fine sand

Fineness modulus is 2.2-1.6, average particle size is 0.35-0.25mm, also called surface sand.

Extra fine sand

The fineness modulus is 1.5-0.7, and the average particle size is 0.25mm or less.

2、Stone dust

Stone dust refers to the particle size less than 0.075mm in the mechanism sand with the same composition as the parent rock being processed. General ordinary concrete requires stone dust content less than 10%, and high strength concrete requires less than 5%;

There are differences in the definition of stone dust content and particle size of mechanism sand in foreign standards.

Stone dust particle size definition: the United States, Japan, Australia and other countries stone dust defined particle size of 0.075 mm, the United Kingdom, France and other countries for 0.063 mm;

Stone powder content: U.S. standards specify the maximum limit of stone powder content of 5-7%; Japan is 7%; Australia is 25%; the United Kingdom is 15%; France is 12-18%.

In China's actual site production, many places also within 10mm of the powder, sand, stone mixture collectively referred to as stone dust, used in the road water stability layer paving.

3、Natural sand and mechanism sand

Natural sand

Naturally formed, artificially mined and sieved rock particles with particle size less than 4.75mm, including river sand, lake sand, mountain sand, desalinated sea sand, but does not include soft, weathered rock particles.

Mechanized sand

Rock, pebbles, mine tailings not treated by chemical methods, made by the process of soil removal, mechanical crushing, shaping, sieving, powder control, etc., the particle size of rock particles less than 4.75mm.

Mixed sand

Sand made by mixing natural sand and mechanism sand in a certain proportion.

MB value of mechanism sand

The ratio of clay in the particle size less than 0.075mm in the mechanism sand to the stone powder of the same chemical composition of the processed parent rock, which is used to determine the amount of mud content. It is generally required that MB value ≤1.4 is qualified.

4, Needle-like particles

The length of the mechanism sand particles is greater than 2.4 times of the average particle size of the particle class is needle-like particles; the thickness is less than 0.4 times of the average particle size is flaky particles.