Definition and Classification of Construction Sand - FUJIAN NINON TECHNOLOGY CO.,LTD.

Terms and Definitions of Construction Sand

Natural Sand

Rock particles with a particle size less than 4.75 mm, formed by rock crushing, weathering, sorting, transportation and accumulation under natural conditions.

Note: Natural sand includes river sand, lake sand, mountain sand and purified sea sand, excluding soft and weathered particles. It is often used as a supplementary raw material in a sand making plant when the supply of manufactured sand is insufficient.

Manufactured Sand

Particles with a particle size less than 4.75 mm, produced from raw materials such as rock, pebbles, mine waste rock and tailings through a sand making plant—the process covers soil removal, mechanical crushing (mainly by a vsi crusher, a key sand making machine), shaping, screening and powder control—to meet requirements for gradation, particle shape and stone powder content.

Note: Manufactured sand excludes soft and weathered particles. The vsi crusher in the sand making machine ensures the particle shape of manufactured sand is close to cubic, which improves the performance of concrete.

Blended Sand

Sand formed by mixing manufactured sand (produced through a vsi crusher in a sand making plant) and natural sand in a certain proportion. This type of sand combines the stability of manufactured sand and the workability of natural sand.

manufactured sand production line

Mud Content

Content of particles with a particle size less than 75 μm in natural sand. Excessive mud content will reduce the strength of concrete, so natural sand needs to be washed before being used in a sand making plant.

Stone Powder Content

Content of particles with a particle size less than 75 μm in manufactured sand. This index is precisely controlled in the manufactured sand production line; the vsi crusher generates a certain amount of stone powder during crushing, and subsequent powder control equipment adjusts it to the standard range.

Clay Lump Content

Content of particles in sand that originally have a particle size greater than 1.18 mm and become less than 0.60 mm after soaking in water, elutriation and other treatments. In a sand making plant, raw materials are inspected for clay lump content first, and those with excessive content are pre-treated before entering the sand making machine.

Fineness Modulus

An index for measuring the fineness degree of sand. In a manufactured sand production line, the fineness modulus of manufactured sand can be adjusted by changing the screen mesh of the screening equipment in the sand making machine system.

Soundness

The ability of sand to resist fracture under the action of external physical and chemical factors. Manufactured sand produced by a vsi crusher in a sand making plant has good soundness because the vsi crusher crushes raw materials through high-speed impact, reducing internal cracks of particles.

Flaky Particle

In manufactured sand, particles with a particle size greater than 1.18 mm where the minimum one-dimensional dimension is less than 0.45 times the average particle size of the particle's respective size fraction. The special crushing principle of the vsi crusher in the sand making plant can effectively reduce the proportion of flaky particles.

Lightweight Substance

Substances in sand with an apparent density less than 2000 kg/m³. In a sand making plant, lightweight substances are separated by wind selection or water washing after the vsi crusher and sand making machine crushes raw materials.

Alkali-Aggregate Reaction

An expansion reaction that occurs slowly in a humid environment between alkali-reactive minerals in sand and alkalis from concrete components such as cement, mineral admixtures and admixtures, as well as alkalis in the environment, leading to concrete cracking and damage. In a sand making plant, raw materials for the sand making machine are tested for alkali-reactive minerals to avoid this reaction.

Classification and Categories

Classification

Divided into natural sand, manufactured sand (produced through vsi crusher in a sand making plant) and blended sand according to source of production. With the shortage of natural sand, manufactured sand has become the main type of construction sand, relying on the efficient operation of sand making machine such as the vsi crusher.

Classification by Fineness Modulus

Divided into coarse sand, medium sand, fine sand and extra-fine sand based on fineness modulus, with the respective fineness modulus ranges as follows:

Coarse sand: 3.7 ~ 3.1

Medium sand: 3.0 ~ 2.3

Fine sand: 2.2 ~ 1.6

Extra-fine sand: 1.5 ~ 0.7

In a manufactured sand production line, adjusting the rotating speed of the vsi crusher and the screen mesh of the sand making machine can produce sand of different fineness moduli to meet diverse construction needs.

Categories

Construction sand is classified into Category I, Category II and Category III according to technical requirements including particle gradation, mud content (stone powder content), methylene blue (MB) value, clay lump content, harmful substances, soundness, crushing index and flaky particle content.

Category I sand: Suitable for high-strength concrete, requiring strict control of particle gradation and stone powder content. It is usually produced by a high-precision sand making machine in a sand making plant, with the vsi crusher ensuring excellent particle quality.

Category II sand: Used for ordinary concrete and mortar, with moderate technical requirements, producible by a standard manufactured sand production line.

Category III sand: Applied to non-load-bearing concrete and backfill projects, with relatively loose requirements, but the sand making machine still needs to control basic particle size.

Particle Gradation

Except for extra-fine sand:

The cumulative sieve residue of Category I sand shall comply with the requirements of Zone 2 in Table 1, and the individual sieve residue shall comply with Table 2. This requires the screening system of the sand making machine in the manufactured sand production line to have high precision.

The cumulative sieve residue of Category II and Category III sand shall comply with Table 1.

The actual particle gradation of sand may deviate from the specified ranges except for the 4.75 mm and 0.60 mm sieve sizes, but the total sum of deviations of cumulative sieve residue across all sieve sizes shall not exceed 5%. In a sand making plant, operators monitor particle gradation in real time and adjust the manufactured sand production line (such as the feeding amount of the vsi crusher) to control deviations.

sand making machine

sand making plant

manufactured sand production line

sand making machine

sand making plant

manufactured sand production line

sand making machine