Aggregate Terms | Gravel Particle Size | Fineness Modulus

Maybe many new friends have doubts about some basic terms of the industry. Let’s introduce some appellations of aggregate industry briefly to help you better understand and communicate.

Material TypeDefinition
Aggregategranular loose material that plays the role of skeleton, filling and volume stabilization in concrete. According to the particle size, it can be divided into coarse aggregate and fine aggregate.
Coarse Aggregaterock particles larger than 4.75mm, including pebbles and crushed stone:
Pebblerock particles > 4.75mm formed by natural weathering, water transportation, sorting and accumulation.
Crushed Stonerock particles > 4.75mm made from rock, pebble and tailings without chemical treatment by desoiling, crushing, shaping, screening, powder control and other processes.
Fine Aggregaterocks and particles with particle size < 4.75mm. Including natural sand and artificial sand.
Natural Sandrock particles < 4.75mm formed naturally, mined and screened manually include river sand, Lake sand, mountain sand and desalinated sea sand
Artificial SandIncluding machine-made sand and mixed sand.
Machine-Made Sandrock particles < 4.75mm made from rock, pebble and tailings without chemical treatment by desoiling, crushing, shaping, screening, powder control and other processes.
Mixed Sandsand formed by mixing natural sand and machine-made sand in proportion

In the mining industry, the particle size of gravel is usually between 5mm-31.5mm, and 1-2 / 1-3 gravels are generally collectively referred to as paving gravels. The specific sizes of gravel are as follows:

Gravel TypeParticle Size
0-5sand with particle size of 0-5mm
5-1gravel with a particle size of 5-10 mm
2-41/4-1/2 inch, 10-15mm gravel
1-2gravel with particle size of 10-20mm
4-61/2-3/4 inch, 15-20mm gravel
1-3gravel with particle size of 16-31.5mm

According to the fineness modulus (MX), the specifications of machine-made sand can be divided into 4 types: coarse, medium, fine and extra fine:

sand fineness modulus

  • 1. Coarse Sand: the fineness modulus is 3.7-3.1, and the content of particles larger than 0.5mm exceeds 50% of the total weight, and the average particle size is 1mm-0.5mm.
  • 2. Medium Sand: sand with fineness modulus of 3.0-2.3, particle size greater than 0.25 mm and average particle size of 0.5-0.25 mm.
  • 3. Fine Sand: the fineness modulus is 2.2-1.6, and the particles with particle size greater than 0.075mm exceed 85% of the total weight, and the average particle size is 0.25mm-0.125mm.
  • 4. Ultra Fine Sand: the fineness modulus is 1.5-0.7, and the average particle size is less than 0.25mm.

In addition, the following terms may also be frequently heard to measure the quality of sand:

Mud Content: the content of natural sand, pebble and gravel with particle size less than 75 μm.
Powder Content: the content of particles with the particle size less than 75 μm in the artificial sand.
Methylene Blue (MB value): an index used to determine the adsorption performance of stone powder.
Needle/Flake Particles: needle particles refer to the length of machine-made sand particles is 2.4 times larger than the average particle size; flake particles refer to the thickness is less than 0.4 times of average particle size.

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