Screening of granite rubble

The production of crushed stone is based on crushing rocks (gravel, boulders). In the process, "sand" is formed – stones with a fraction less than 5 mm. According to GOST 8267-93, such material is considered waste, but it is allowed to be used in construction. Such screening, according to the privacy policy, is regulated by GOST 31424-2010 and is delivered to the consumer both in bags and in bulk with delivery.

What is the screening of crushed stone and how does it differ from the usual
Visually, it is not always possible to determine the source of stone seeding. In practice, three types of screening are produced – granite (density 1330-1350 kg/cubic meter), gravel (up to 1400 kg / cubic meter) and limestone (1290 kg/cubic meter). Externally, they look like "sand" in color like crushed stone from the same raw materials. For example, granite boulders. They are found in blue, red, green and gray shades.

Features of granite screening:

particle size 0.1-5 mm;
free of organic inclusions (tolerance up to 0.4% by weight);
low bream content (the presence of flat grains).
Screening is always a byproduct in the manufacture of crushed stone. It differs only in particle size and application area. It is partly similar to sand, but the latter differs in parameters such as the lack of evaluation by the granulometric system. Because of this, sand raw materials are very limited in their scope of use. In addition, the cost of obtaining sand screening and extraction varies significantly, which forces enterprises to make a choice in favor of the first material and its convenient delivery.

Unlike gravel, granite screening has sharp edges, which improve adhesion to cement mortar in the manufacture of concrete. In part, it is this property that creates the specifics of the application of crushed stone screening. Limestone raw materials are "too" soft in comparison, although they have a slightly lower weight (due to the initially different density of the stone).

When processing granite raw materials, screening is obtained "automatically". The same thing happens when working with limestone. If crushed gravel is needed, you will have to spend money on additional processing (you need a separate technical base). The conclusion is simple – granite is cheap, it is quite durable, suitable for most construction work. 16-20% of the total mass of crushed stone is eliminated.

Scope of use
The similarity in technical characteristics with sand determines the main purpose of screening – as a component of concrete mixtures. It is used for filling floor screeds, monolithic structures such as foundations, load-bearing walls, and internal partitions. The material is also in demand as a filler in the manufacture of precast concrete products with almost any filler – from crushed stone to polystyrene. This material, even with delivery in Yekaterinburg, is cheaper than other options, which makes it profitable for those who want to buy screening for concrete mixes.

Popular areas of use:

production of paving slabs, water gutters, curbs;
preparation of asphalt and concrete mixtures for the roadway;
mixing of plaster and masonry mortars;
leveling, lifting of sections, roadsides;
organization of drainage and septic tank.
It is also worth adding the possibility of filling trenches, pits after the installation of pipelines, cables, and other underground utilities. Granite screening is sometimes used for landscaping on the shores of artificial ponds, flower beds, and alpine slides. In winter, its abrasive properties become relevant. Artificial sand is sprinkled on sidewalks when periods of ice come. This material, even with delivery, is cheaper than other options.

The main thing is to make sure in advance that granite is really suitable for the chosen task. There is also a dropout from marble and other materials. They stand out for their more decorative appearance, although gray sometimes remains the "only correct" shade for the chosen design. When it comes to mixing concrete, granite chips are the only sure option.

Specifications
In addition to GOST 8267-92, granite screening is subject to technical specifications, which indicate its main characteristics at the "outlet". Thus, the strength grade corresponds to M1200, the size modulus is in the range from 0/5 to 3/7, the passage through the sieve is 0.16% by weight of 13.0. If the material does not meet these basic criteria, it is considered "defective" and requires either additional dusting before use or complete rejection.

The parameters are also taken into account:

grain size – from 0.1 to 5 mm;
radioactivity – up to 158 Bq per 1 kg;
the proportion of impurities in the composition is not more than 0.4%;
particle size – 14-19%;
The frost resistance limit is F300;
The bulk density is 1300 kg per 1 cubic meter
. Natural (true) density is also distinguished. It ranges from 2615 to 2620 kg per 1 cubic meter. The bulk value is noticeably lower due to the air in the voids (up to 50% of the volume). Sometimes there are questions about the proportionality of the price of the dropout batch if the seller sells materials by volume rather than weight. In this case, there is a dependence of the specific gravity on the volume of dropout, its greediness.

The more flat, plate-like particles there are in a cubic meter, the heavier it is. The ideal shape of a stone is cubic, when it is theoretically possible to obtain a monolithic array. With a fraction size from 0.1 to 4.8 mm, 1 cubic meter of screening weighs 1.41 tons, a large one contains more air per unit volume, and this slightly reduces the indicator (up to 1.33 tons). Builders usually set a margin of 10% (the result is multiplied by a factor of 1.1).

Advantages of granite rubble
The choice in favor of granite is explained by the natural origin of this material, its outstanding strength, durability under the influence of atmospheric precipitation, and other natural factors. In its original state, granite stone with a thickness of 1 cm can withstand a load of up to 100 tons. And all this is due to the high density and uniformity of the structure.

Granite Features:

good frost resistance;
immunity to washout;
absolutely harmless to humans;
reliable adhesion to cement mortar.
The relatively high price is offset by a long service life and a modest amount of repair costs for structures made using granite chips. Including with increased mechanical loads on the surface (floor screed, plaster, foundation). This makes granite screening even more advantageous when mixing concrete mortars than sand.

In its pure form, granite is in demand in several different directions. For example, a fine fraction from 5 to 20 mm is used when laying trails. Stones of 20-40 mm are used for construction, 25-60 mm – for railway, tram embankments, parking lots for heavy vehicles, 40-70 mm – for large buildings, in industry. The largest stones measuring 70-300 mm are relevant in landscape design, in the construction of massive structures.

Depending on the specific sphere, the surface of the stones is impregnated with bitumen, painted, and sanded. Before crushing, they must be washed to prevent the ingress of biological particles and excess dust into the mixture. Therefore, the screening contains "pure" granite, without any impurities.

The cost of granite rubble
The price of a batch of crushed stone screening is simultaneously influenced by several factors. The first is the source of the material. "Natural" or primary crushed stone is extracted from rocks. But there is also a secondary one, made from pieces of concrete and bricks, including those with the addition of granite "grits" to one or another volume. The second option is cheaper, but it is no longer a "pure" stone, but a mixture with cement and other additives.

Such a reduction in the cost of building materials is sometimes "handy" (when filling pits, filling areas before laying the road surface. The initial cost of raw materials also depends on the type of crushing chosen. After all, screening is formed during the production of fractions of 70 mm and 10 mm. At the same time, there is always more "waste" in the manufacture of small stones, which means they are cheaper.

The cost also depends on:

the method of packaging and transportation is in bags, in bulk, on cars of various tonnages;
delivery distances – from the quarry or source plant to the construction site;
the volume of the purchased batch – large volumes are more profitable for the seller, therefore, discounts are often provided for bulk orders, and payment for delivery is canceled.

In the case of screening, the fraction does not play a special role in the assessment, as when buying granite rubble. After all, it is waste from the mining industry, so there are no separate costs for the output and there will not be. When estimating the required volume, the optimal mode of transport is selected. After all, if you make the wrong choice, you will have to make more flights and pay for fuel each time. Therefore, the tonnage of the equipment is determined in advance.

By agreement, the price also changes based on the availability of the construction site, the delivery mode (by phone, around the clock, in agreed batches). The higher the load on the seller's vehicles, the more expensive it will be to drop out. But this is probably offset by a discount for wholesale and a convenient schedule for the delivery of building materials.