1. Granite aggregates
Granite aggregates are crushed hard rock of granular structure, being the most common on Earth. Granite rock comes from magma that erupted on the ground surface and then hardened. Good properties of granite make it the most popular building material.
In terms of its technical characteristics granite is solid (grades 800-1200) and highly solid (grades 1,400-1,600), frost resistant (grades 300-400), with low flakiness index (5-23%), of the 1st class in terms of radionuclidity (A (eff) <370nBq/kg). The radionuclide content, harmful components and additives indicators are either absent or do not exceed norms, the fact of which is proven by corresponding certificates and conclusions issued after conducted researches.
It is the best aggregate for high-grade concrete. Granite is also used as a decorative stone. It can be grey, red, or pink and has a lot of shades. After polishing it acquires a beautiful smooth surface. Granite is mostly composed of feldspar, quartz and mica crystals, the content of which influences the color and shades of the stone.
Fractions of granite aggregate and their applications
0-2 mm, 0-5mm (granite sand): the smallest granite aggregates fractions are used, besides the road construction, for decoration and paving paths, for covering sports grounds and children's playgrounds. Such aggregates are used for making various reinforced concrete structures. They are used for deicing (decrease the slip coefficient). Granite sand is successfully used in landscape architecture (for gardening).
2-5 mm: aggregates of this fraction are mainly used to produce paving slab and other similar construction products where such fraction is crucial.
3-10 mm: this small fraction, like the popular 5-10 fraction, is used for road construction and production of concrete.
5-10 mm: this is the most popular aggregates fraction. Aggregates of this fraction are used in production of concrete and concrete structures, construction of roads, buildings and bridges as well as for different types of fillings, drainages, etc. However, the main application of aggregates of this fraction is road surfacing. When producing concrete, its main strength factor is the fullness of aggregates. The more aggregates are in the mixture, the stronger the concrete. The quality of round or cubic aggregates creates the highest compaction, while the presence of needle shapes leads to the creation of voids and increases in binding component volumes and thus reduces the concrete strength. For this reason small aggregates fractions, one of which is the 5-10 fraction, are used in production of quality concretes.
5-20 mm: small fraction. Aggregates of this fraction are mainly used in road concrete mixes. This size provides the most adhesion in the mixture, which subsequently makes the most solid type of concrete and also provides surface evenness of concrete blocks. This minimizes the preparation of walls, floors and ceilings of buildings for the final stage of treatment - putting up wallpaper, laying tiles, etc. This given fraction is the most used, percentage wise, in all construction work.
10-20 mm: small fraction. This given aggregates fraction is in the most demand in road construction. Aggregates of this fraction are used for laying both asphalt and concrete roads. It is used as filler for garretting -sub-base preparation for the road surface
20-40 mm: a medium fraction. It is used for road construction as a lower layer beneath the asphalt surface. Currently this fraction is the most commonly used in Ukraine's construction industry. It is used both for small private construction and for construction of large industrial spaces. Aggregates of this fraction are used as sub-bases in construction of highways and railways and in production of concrete and massive structures from reinforced concrete. It is used as filler for parking areas and bases for foundations when building work areas for the operation for heavy construction machinery and as filler for increased strength concretes.
0-20 mm, 0-40 mm: a road subbase that is used for road building and maintenance operations.
5-8 mm, 8-11 mm and 11-16 mm (Euro fractions): used for production of high-quality concrete and conforming to European standards.
5-250 mm: a large fraction of aggregates (processed after primary crushing) that is used as a basis for road surface.
20-70 mm, 40-70 mm: a large fraction that is used in production of concrete and solid concrete structures and in works with large volumes of concrete. It is also used in road construction within residential areas and in building of industrial spaces and premises.
70-120 mm, 120-150 mm, 150-300 mm (quarry stone): rarely used. It is used for decorative purposes, usually reveting of catchment areas, reservoirs, and basins.
2. Gravel aggregates
Gravel aggregates are aggregates acquired as the result of sifting quarried rock and by crushing natural stone rock. In strength, gravel aggregates are inferior to granite aggregates, but they also have their advantages: their radioactive background is usually very low and they are cheaper than granite aggregates.
Gravel aggregates are used for foundations and concretes and in products made of reinforced concrete and in road construction.
There are two types of gravel aggregates:
• Scabbled stone- - regular natural or crushed,
• Gravel - rounded pebbles usually of river or sea origin.
Fractions of gravel aggregates are as follows: 3-10 mm, 5-20 mm, 5-40 mm, 20-40 mm.
3. Limestone aggregates
Limestone aggregates are a product of the crushing of sedimentary rock - limestone, which is composed mainly of calcite (calcium carbonate - СаСО3).
Limestone aggregates (sometimes called lime or dolomite aggregate) is one of the main types of aggregates that besides the gravel and the granite types is used in road construction and in production of reinforced concrete objects.
4. Secondary aggregates
Secondary aggregate comes from crushing construction waste - concrete, bricks, and asphalt. This type of aggregate is made with the same equipment as other types of aggregates.
The main benefit of secondary aggregate is its low cost: on average, it is two times cheaper than the granite type. Power input for its production in comparison to other types of aggregates can be up to 8 times lower. The prime cost of concrete in which secondary aggregate is used as a large filler is a quarter lower.
In terms of strength, frost resistance, and certain other characteristics secondary aggregate is inferior to aggregates made of natural stones; nonetheless it has wide application:
• As a large-scale filler for concretes with strength 5 ... 20 MPa;
• In road construction (filler for roads and ramps, use as a lower layer for roads that do not have state importance);
• In maintenance works (filler under asphalted areas and sidewalks);
• For reinforcing the weak soils (trenches for utility network and bottoms of construction pits).
5. Slag aggregates
Slag aggregates are obtained by crushing of smelter slag or by special treatment of fire-liquid slag melt (molten slag aggregates). Currently there are many types of concretes that are developed and used in construction that include metallurgical slags both as a binding component and as fillers. The cost of products from slag concretes is 20-30% lower than traditional ones.