Concrete crushed stone: purpose, characteristics,

We all know that in the production of concrete mortar use crushed stone, but not everyone understands its purpose and characteristics, which must be met by this important component of the mixture. We will tell you what kind of crushed stone is needed for concrete, as well as dwell on its varieties, characteristics and show why rubble is in concrete.

Construction gravel

Purpose and properties

Щебенка – это минеральный неорганический продукт дробления горных пород, гравия, валунов, отходов горных предприятий, переработки руд, шлаков металлургических заводов и ТЭЦ, а также вторичной переработки строительного мусора. Камень должен быть сыпучим и иметь фракцию от 3 – 5 мм до 150 мм и выше. Особо крупный отсев называется бут (читайте также статью «Бетонная брусчатка или как недорого обустроить место на участке»).

The average density of gravel is 1.2 - 3 tons per cubic meter.

In addition, there is a set of important properties, which assess the quality and suitability of raw materials for various purposes:

1. Fractional composition - one of the main characteristics of the product. Determined by the largest particle size of the grains, while these grains are not less than 30%. The separation into fractions is carried out in the process of mining and crushing stone in special separators and screenings;
2. Grain Shape - no less important characteristic of gravel, which determines its quality and the possibility of using it in construction and production of reinforced concrete products. Grains should be as close as possible to the cubic form, otherwise they say about the high flakiness of the material, that is, the stones in it have a flat or needle shape when the thickness or width of the grain is more than three times its length;
3. Grain strength - The most important parameter, which depends on the type and origin of the stone. Distinguish high strength - M 1200 - M 1400, durable - M 800 - M 1200, medium - M 600 - M 800, weak - M 300 - M 600 and very weak - M 200. Strength is determined by checking the crushability in the cylinder, the ultimate strength for compression and wear in the shelf drum, imitating stone wear during road works;
4. Frost resistance – важный показатель качества камня, который характеризуют количеством циклов замерзания-оттаивания или циклов насыщения-высушивания в растворе сернокислого натрия. Различают такие марки по морозостойкости: F15, F25, F50, <…>, F300, F В строительстве используют продукт марок F300 и F400;
5. Radioactivity - Mandatory characteristic, which shows the safety and applicability of crushed stone for housing construction. For the construction of houses, high-strength crushed stone of class I of radioactivity is used, that is, the effective activity of radionuclides in the composition of the stone (Aeff) does not exceed 370 Bq / kg. For the construction of roads within cities, raw materials of class II radioactivity are allowed, with Aeff no more than 740 Bq / kg;
6. Breed stone or composition - also an important quality indicator. Granite and gravel rubble is considered to be the most durable and of high quality, limestone material is also quoted, and slag and secondary gravel are sometimes used. Crushed stone secondary concrete is a product of crushing and screening of construction waste.

  Note! Crushed stone for concrete according to GOST 8267-93 should have a fraction of 3–8 or 5–20 for the production of ready-mixed mortar and reinforced concrete products, a fraction of 20–40 is used for laying foundations and pillows, and sizes 25–60 and 40–70 are used in road construction according to GOST R 54748-2011.

Also called construction standard involves the use of other fractions, but this practice is limited and is rare. Extra large fraction can be used in very large volumes of filling in the construction of large objects, such as dams, moorings, bridges, soles of foundations.

They use crushed stone for the production of concrete mortar, including commercial, concrete products, screeds, foundations, floor slabs and columns, bearing elements and in monolithic construction.

Also, this material is used in the production of road works, when crushed stone and mastic asphalt concrete is prepared, pillows and drainage bedding are made under the rails, as well as for other construction activities within the listed areas.

Types and characteristics

Существуют различные по происхождению разновидности щебенки (см.также статью &#171;Саморезы по бетону: параметры выбора&#187;).

In construction and production use such of them:

• Granite. It is mined by the development and crushing of granite rock and frozen magma, obtaining durable and high-strength (M 800 - M 1600) screenings with low flakiness, high frost resistance and class I radioactivity. It is considered the best aggregate for high-grade concrete;
• Gravel. It is obtained by screening quarry rocks and crushing stone rocks, getting screenings of 5 - 40 mm. The strength is inferior to granite, but it has a low radioactive background and is cheaper. Widely used in construction, production of concrete products and road works;
• Limestone. It is obtained by crushing sedimentary rocks consisting of limestone and calcite, obtaining high-quality stone, also used in construction and production along with granite and gravel raw materials, as well as for draining sprinklers;
• Slag. Produce crushing of slag heaps and melts, as well as porous slags with high gas saturation (aerated concrete rubble). Use in construction and production of concrete goods, road works and works on improvement of territories as adding under asphalt and concrete as a cheaper product;
• Secondary. The price of granite and gravel raises the question: “What is the replacement of crushed stone in concrete?”, And the answer was the processing of concrete into crushed stone, as well as the crushing of construction debris - bricks, concrete goods, asphalt, etc. The material allows to reduce the cost of production of the solution by about a quarter.

Note! In private construction, raw materials from granite and gravel are most often used, but sometimes they produce recycled materials with their own hands by crushing sub-standard bricks, sludge and sledgehammers, construction waste and demolishing screeds or walls.

In some cases, the instruction does not involve the use of granite and gravel, since their excessive strength makes it difficult to work out products. This is true for floors, followed by grinding the screed when you need to cut reinforced concrete with diamond circles or diamond drilling holes in concrete. Limestone crushed stone is more suitable for these procedures.

Conclusion

Щебенка – важный и широко используемый строительный материал, незаменимый при производстве бетонного раствора, железобетонных изделий, дорожных работах, сооружении подушек, дренажных подсыпок и благоустройстве территорий (см.также статью &#171;Железобетонные фермы – размеры, расчет и производство&#187;).

The video in this article will help you learn more about this material.