According to the dictionary, broken or unbroken, artificial or natural, dense mineral materials of different sizes are called aggregates. Among the aggregate types, sand and gravel are the most commonly used building materials. Pebbles are the most widely used natural aggregate type in construction. However, most of the time, instead of gravel, the crushed stones obtained by shredding natural stone masses by using machines are also used as aggregates. Where natural sand is needed, artificial fine aggregates are obtained by using grinding machines.

The main feature of the aggregate is that they are intact, do not wear easily, do not soften and disperse in contact with water. When using aggregates, they should not form a harmful compound when combined with cement components and should not endanger the wear protection of the place where it is used. In addition, the texture and shape of the aggregate grains are expected to be good and the distribution of the grains in terms of their size is expected to be in accordance with the intended use and standards. And, of course, there should be no other harmful substances in the aggregate.

Factors that determine the physical properties of the aggregate are: unit weight, density, compassion of the aggregate, ie the size of the volume occupied by the grains per unit volume, the resistance of the aggregate to freezing and thawing, and the nature of the gaps between aggregate grains. In addition, the factors determining the mechanical properties of the aggregate are: pressure resistance of the aggregate, abrasion resistance and impact resistance.

The most important building material in concrete construction is aggregate. Aggregate diversity, compressibility and granulometry (ie, to what extent aggregate is used) affect the class of concrete. In simple terms, the aggregate is a mixture of sand, gravel and crushed stone, with diameters up to 4 millimeters of sand and gravel up to 32 millimeters. Aggregate is obtained by blending these materials and is used to form concrete in buildings. In some cases it is also used as a filling material.

Aggregates with these properties are two kinds as natural aggregate and artificial aggregate. Natural aggregates are generally obtained from river beds, sea coasts and sand quarries. It has a wide range of applications from aggregate, road and tunnel constructions to all kinds of constructions.

Aggregate tests are performed in authorized test and inspection laboratories. During these tests, the current regulations and published standards are taken into consideration. The following are a few standards for aggregate testing:

• TS EN 1097-6 Tests for mechanical and physical properties of aggregates - Part 6: Determination of grain density and water absorption rate
• TS EN 1744-7 Tests for chemical properties of aggregates - Part 7: Determination of combustion loss of aggregate (MIBA aggregate) in municipal ash incinerator
• TS EN 933-1 Tests for geometric properties of aggregates - Part 1: Determination of particle size distribution - Screening method
• TS EN 933-7 Tests for geometric properties of aggregates - Part 7: Determination of shell content in coarse aggregates - Percentage of shell
• TS EN 932-5 Tests for general properties of aggregates - Part 5: General instruments and calibration
• TS EN 1355 Aerated concrete or lightweight aggregate porous concrete - Determination of creep under pressure