Artificial aggregates are obtained from heat-treated rocks and industrial waste. The use of a specific type of artificial aggregate depends to a large extent on their production in a given region of the country.
Criteria for the division of artificial aggregates:
1. Due to the type of rock material and the method of obtaining it:
• Aggregates from thermally treated mineral raw materials: expanded clay, aluminoporite The most frequently used artificial aggregate is expanded clay aggregate. The basic raw material for its production is clay, which, after the maturation period, is mechanically plasticized and crushed. The granules obtained in this way are fired at a temperature of 1200 ° C. During the firing process, the granules increase in volume several times, creating a lightweight aggregate with spherical grains and porous structure. LECA is segregated into specific fractions (10-20 mm, 4-10 mm, 2-4 mm and 0-2 mm) on mechanical screens. Depending on the faction 1 m3 of expanded clay weighs from 350 do 500 kg.
LECA is most often used as a thermal insulation for ceilings, flat roofs, vaults, foundation and basement walls, floors on the ground, etc.. It is a material suitable for the renovation of ceilings and wooden floors in historic buildings – during the renovation of the ceiling, the existing roof can be replaced (clay mixture, chaff and lime, located in the space between the supporting beams) on a layer of lighter expanded clay.
LECA is also used to make structural elements of lightweight concrete (popularly known as expanded clay aggregate) – blocks for erecting load-bearing and partition walls, ceiling and ventilation blocks, lintels.
• Aggregates from thermally treated industrial waste: Grail, slate engraving, ashpore, metallurgical pumice stone, slag.
• Aggregates from industrial waste not subjected to additional thermal treatment: elporyt, blast furnace slag, other types of metallurgical slag, furnace slag, fly ash.
• Organic aggregates from wood processing waste (scobs, peat, cane, rapeseed straw, chaff).
2. Due to the graining:
• Fine aggregate – with a grain diameter up to 4 mm.
• Coarse aggregate – about the grain size 4-63 mm.
3. Due to the apparent density:
. Ordinary aggregate – about density 1800 – 3000 kg/m3.
• Lightweight aggregate – with a density less than 1800 kg/m3.