What is manufactured sand (M-sand)?
Manufactured sand(M-sand) is also called machine-made sand, which is made by mechanical crushing and screening. Rocks, mine tailings or industrial waste slag particles with a particle size of less than 4.75 mm.
Characteristics of manufactured sand for construction
l. Artificial sand particles have edges and corners and irregular shapes, so they contain needle-like particles.
The manufactured sand particles interlock with each other, and the flow resistance is large, so the workability of the mixed concrete is poor, but the manufactured sand usually contains stone powder to improve the work performance of the concrete. The occlusion between artificial sand particles can improve the flexural strength and tensile strength of concrete, and has a limiting effect on the deformation of concrete.
2. The surface of manufactured sand is rough. The rough surface of artificial sand increases particle flow resistance and adversely affects workability, but it also increases the bonding strength between aggregate and cement slurry. At the same time, the rough surface will increase the water absorption rate, and the larger water absorption rate will affect the frost resistance of medium and low strength concrete. Air-entraining agents can be used to improve the frost resistance.
3. Poor gradation of manufactured sand. There are more coarse particles (above 2.36 mm) and fine particles (below 0.15 mm), but there are fewer intermediate particles (especially between 1.18~0.3 mm), which have an adverse effect on the strength of concrete.
4. Usually in the same construction site, manufactured sand and crushed stone are the same kind of parent rock, with the same thermal properties, which are particularly effective for mass concrete technology.
5. manufactured sand usually contains stone powder. Stone powder can improve the gradation of aggregates, play a role of lubrication and filling, improve the workability of concrete, increase the density of concrete, and improve strength and impermeability. Stone powder also increases the overall specific surface area of the solid particles in the mixture, and increases the cohesion and water retention of the concrete mixture.
At present, there are different definitions for the particle size of stone powder in machine-made sand. Some refer to particles smaller than 0.16 mm in size, and some refer to particles smaller than 0.08 mm or 75μm. In some European countries, “stone powder” means particles smaller than 63μm.
Definition of stone powder content
Usually refers to the content of particles with a particle size of less than 75μm in the artificial sand.
Configuration of manufactured sand concrete
The technical process of preparing high-quality concrete with machine-made sand:
1. Increase the stone gradation and reduce the porosity.
2. Increase the amount of admixtures-fly ash, mineral powder, stone powder, and increase the air content (defoaming agent + air-entraining agent).
3. Reduce cement consumption and water consumption.
What is natural sand?
Natural sand is formed by natural weathering, water flow handling, sorting, and accumulation. The particle size is less than 4.75 mm. According to its source of production, it can be divided into river sand, sea sand, and mountain sand. It is a non-renewable resource .
Manufactured sand vs natural sand
Difference between manufactured sand and natural river sand
1. Natural river sand has few edges and corners and has a smooth surface. Manufactured sand has many corners and rough surface.
2. Natural sand does not contain powder (particles ≤75μm are often called mud). Manufactured sand contains a lot of powder (particles ≤75μm are usually stone powder, and the strength of its water absorption is greatly affected by the type of original rock and its degree of weathering).
Read Also : How to make manufactured aggregate