Loose material (sand, gravel): production and sale

Nonmetallic bulk materials are the main components in the construction sector. Sand, crushed stone are used in the production of concrete and reinforced concrete structures, building mixtures. These materials are used for the preparation of grounds, planning, landscape works. In road construction, crushed stone is used as the underlying layer of the roadway. Some types of rubble are used to improve the surrounding areas.

Types of gravel and sand

All bulk building materials are classified according to several basic criteria:

• The origin;
• Physical and mechanical properties (density, strength, frost resistance, moisture absorption);
• Form and size of grains;
• The level of radioactivity, the presence of organic and inorganic impurities.

The origin of crushed stone and sand depends on the source material. Distinguish rubble from rocks, ore crushed stone, which is produced from metallurgical recyclables and secondary, obtained by crushing construction waste (concrete, brick). The physical and mechanical properties of crushed stone directly depend on the material of its origin. The most demanded materials, the basis of which are rocks of high strength - resistant to deformation and destruction under mechanical action. The size of the gravel is divided into several types: screening (up to 5 mm), medium (5-25 mm), large (25-40 mm).

Sand by origin is divided into natural and artificial. Natural bulk material is obtained by the development of sandy or sandy-gravel deposits. Depending on the occurrence, sea, river or mountain sand is distinguished. The first two species are distinguished by more rounded grains and a lower content of impurities, compared to materials produced in quarries. By the size of granules, sand is divided into large, medium and small.

Production of natural sand

The production of natural non-metallic bulk materials includes several stages:

• Production;
• Processing and enrichment (if required);
• storage.

Virtually all types of bulk materials are extracted by open method. Quarry sand is extracted by excavators or bulldozers. In the production of mountain sand, due to the presence of a large number of impurities and different granule sizes, additional processing and enrichment of the raw materials is required. This process involves washing and sorting the material. For the production of the smallest fraction used in the production of cement-based mortars, additional grinding of sand by roll crushers is possible. Natural sand refers to materials prone to caking, so in its production, a silo for bulk materials is often used - an inverted truncated pyramid device for storing and feeding loose material.

River sand is extracted hydromechanically in reservoirs. Barges with hydraulic pumps pump raw materials from the bottom of the river to the hydro-dump on the shore. Water comes back into the river, and the sand remains in the dump. If the bottom is too dense, a bucket elevator is additionally used.

Manufacture of artificial sand

The geographical location of deposits of natural sand is uneven, which may lead to a shortage of this material in some regions. The production of artificial sands can largely solve this problem by providing the necessary needs. Artificial bulk material is obtained by crushing hard rocks and raw materials from other sources. Depending on the material of origin, the following types of artificial sand are distinguished:

• Crushed . Used in acid and decorative compositions. Produced by crushing marble, diabase, basalt or dense metallurgical slag.
• Light sands, organic and inorganic. Bulk material obtained from pumice, volcanic slag, tuff, agricultural and wood waste.
• Sedimentary sands are the result of grinding shell rock.
• Expanded clay sand, obtained by crushing claydite rocks - a heat-insulating material, a filler for lightweight concrete and mortar.
• Porous sands from slag.

Crushed stone production

Raw materials for the production of crushed stone is extracted open-pit in quarries of various rocks. Depending on the characteristics of the deposit and the extracted rock, the method of reservoir development is chosen. Pre-drilling and blasting operations are carried out for especially hard rocks. In the previously drilled wells, a charge is placed. Explosion of the rock breaks into pieces, which come for further processing.

The extracted raw materials are supplied to crushing, which is carried out by crushers of various types (roller, jaw, shock, cone). The choice of technology is made depending on the type of the final product. After crushing, the finished crushed stone comes for sorting. The screening method divides the material into fractions according to the grain size. The installation is a series of large screens with holes of different diameters. The smallest fraction passes through all the levels of the sieves, settling in the pan. In the grading process, the crushed stone can be washed to remove clay impurities.

Main types of rock debris

There is a fairly large group of these materials, but among them the following types are most in demand:

• Granite - the most durable crushed stone of igneous origin. Its basis is made up of quartz, mica and spar. The most common shades are red, pink, gray. In view of their origin, particular attention should be given to certificates of radioactivity when selecting this material. Due to its physical and mechanical properties, the most popular type of crushed stone.
• Gravel . The basis of this material is rock rocks. Produce this kind of rubble in two ways - crushing rocks (crushed gravel) and sifting river or sea soil (rounded gravel). By strength is much inferior to granite, but cheaper with a low radiation background.
• Quartzite . Loose material from rock quartz. On the strength is not inferior to granite, but it has an insignificant radiation background. Thanks to the original structure and attractive colors, it is very popular in decorating.
• Limestone . Produced by crushing sedimentary rocks. On strength is inferior to all other types of rubble. The basis is dolomite and lime. Advantageous difference - low price.

Areas of application of loose materials

The range of application of non-metallic bulk materials is extremely large, it covers almost all stages of construction and is quite in demand in other types of work:

• Preparation of concrete of various grades.
• Manufacture of concrete products.
• Road construction.
• Arrangement of railways, runways.
• Landscape design.
• Livestock raising.
• The device of a protective layer on a road surface at ice.

Transportation of loose materials

Transportation of loose materials is carried out by rail (for long distances), by road and river transport. For rail transport the most suitable are open wagons, open platforms, dumpcars - special open wagons with the possibility of automatic unloading by tipping over. For transportation of sand and rubble by motor transport the most suitable are dump trucks. The delivery of bulk materials by river barges is the cheapest option for transportation, but is only relevant if the waterways are close. When transporting it is not recommended to pour these materials into another transport on the way to the place of delivery in order to avoid losses.

Storage and sale

After mining and, if necessary, enrichment of sand gravel in the form that it sees the consumer is sent to the warehouse. Each type and fractional composition of bulk material is stored separately. Storage areas should be flat, rainwater should not be collected in them. If necessary, additional protection is provided from groundwater. In winter, the materials are cleaned of snow and ice.

Delivery of non-metallic materials from the storage place is most often carried out by road. Exceptions are large enterprises with separate railway branches. For secure and convenient shipment of materials to the end user, the storage area is equipped with convenient access roads. Usually, one-way ring traffic is organized. For convenience of loading and prevention of caking, a silo for bulk materials is used. For work at night, artificial lighting is provided.