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Release time:Apr.04.2024 Views:0

Definition of machine-made sand

According to national standards, all machine-made sand and mixed sand that have been treated with soil removal are collectively called artificial sand. (Stone Crusher)The specific definition of machine-made sand is rock particles produced by mechanical crushing and screening, with a particle size less than 4.75mm, but does not include particles of soft rock and weathered rock.

Specifications of machine-made sand

Artificial sand is currently basically medium-coarse sand, with a fineness modulus between 2.6 and 3.6. The particle gradation is stable and adjustable, and contains a certain amount of stone powder. Except for an increase in the 150m sieve residue, the rest of the sieve residue is mostly Triangular or rectangular body with rough surface and sharp edges and corners. However, due to the different mineral resources for the production of machine-made sand across the country, as well as the different equipment and processes for producing and processing machine-made sand, the grain type and gradation of the machine-made sand produced may be very different. For example, some machine-made sand has more flaky particles, and some The particle gradation of machine-made sand is large at both ends and small in the middle, but as long as it meets all the technical indicators of artificial sand in the national standard, it can be used in concrete and mortar. Artificial sand that does not meet the technical requirements of the national standard cannot be used because the grain shape and gradation of machine-made sand can be adjusted and improved. In this regard, there is an essential difference between artificial sand and natural sand. The mixing ratio of mixed sand into random sand reduces its above characteristics.

The specifications of machine-made sand are divided into four types according to the fineness modulus (Mx): coarse, medium, fine and extra fine:

The fineness modulus of coarse sand is: 3.7-3.1, and the average particle size is above 0.5mm; the fineness modulus of medium sand is: 3.0-2.3, the average particle size is 0.5mm-0.35mm, and the fineness modulus of fine sand is The number is: 2.2-1.6, the average particle size is 0.35mm-0.25mm; the fineness modulus of extra-fine sand is: 1.5-0.7, the average particle size is below 0.25mm; the larger the fineness modulus, the coarser the sand; The smaller the fineness modulus, the finer the sand.

Grades and uses of machine-made sand

(1) Grade: The grade of machine-made sand is divided into three grades according to its skill requirements: I, II and III.

(2) Usage: Type I sand is suitable for concrete with a strength grade greater than C60; Type II sand is suitable for concrete with a strength grade of C30-C60 and frost resistance, impermeability or other requirements; Type III sand is suitable for concrete with a strength grade less than C30 with building mortar;


Requirements for machine-made sand

The particle size of machine-made sand is between 4.75-0.15mm, and there is a certain proportion limit for stone powder smaller than 0.075mm. The particle sizes are divided into: 4.75, 2.36, 1.18, 0.60, 0.30, 0.15. The particle sizes should preferably be continuous, and each particle size should have a certain proportion. The particle shape should preferably be cubic, and there are certain restrictions on the content of needles and flakes.(Stone Crusher)

Particle gradation of machine-made sand

The particle gradation of sand refers to the proportion of sand size particles. If the sand is of the same thickness, the gaps between them will be larger; when sand of two particle sizes is matched, the gaps between them will be reduced; when sand of three particle sizes is matched, the gaps will be smaller. It can be seen that the porosity of sand depends on the matching degree of particle sizes of sand materials at all levels. Well-graded sand not only saves cement, but also improves the compactness and strength of concrete and mortar.

Raw materials for machine-made sand

Sand-making raw materials for machine-made sand usually use granite, basalt, river pebbles, cobbles, andesite, rhyolite, diabase, diorite, sandstone, limestone and other varieties. The machine-made sand made from it is distinguished according to the type of rock, with differences in strength and use.

Grain type requirements for machine-made sand

The mine configuration requires that the particles of the crushed materials be fine. Generally speaking, needle-shaped materials are more likely to be ground when entering the mill. The requirements for construction gravel are exactly the opposite, with strict proportion restrictions on needle and flake shapes. The main reason is that the cubic particles have edges and corners, which can lock the particles together. At the same time, cubic particles have stronger adhesion than needle-shaped particles and round particles, and occupy a larger surface area.

Characteristics of machine-made sand

The characteristics of concrete made with artificial sand are: the slump decreases and the 28d standard strength of concrete increases; if the slump remains unchanged, the water demand increases; but when the water-cement ratio becomes larger without adding cement, generally In this case, the measured strength of concrete does not decrease. The concrete proportion is designed according to the rules of natural sand. Artificial sand requires a large amount of water, has poor workability, and is prone to bleeding, especially in low-strength concrete with a small amount of cement. Characteristics of concrete proportion design, by rationally utilizing the stone powder in artificial sand and adjusting the sand rate of artificial sand, it is possible to prepare concrete with good workability. The proportion design methods of ordinary concrete proportion design regulations are fully applicable to artificial sand. The fineness modulus of artificial sand most suitable for preparing concrete is 2.6-3.0, and the gradation is zone 2.

Inspection standards for machine-made sand

The country has standardized fine aggregate inspection standards. The main inspection items are: apparent relative density, solidity, mud content, sand equivalent, methylene blue value, angularity, etc.