Classification of concrete

The most commonly used classification of concrete is according to:

1. The terms of the mixing of concrete
2. Bulk density of the concrete
3. The type of binder
4. The consistency of the fresh concrete
5. Concrete class
6. The purposes of concrete and other.

Classification according to the terms of mixing of concrete

Depending on the conditions under which fresh concrete prepares, there are two different categories of concrete:

• the first category of concrete (B.I), which can be mixed without the previous tests, but amount of cement determined by Article 26 of the Rulebook on technical norms for concrete and reinforced concrete ("Official Gazette SFRY", No. 11/87 ) (download Rulebook) must be used. First category concrete (B.I) includes following concrete classes: MB 10, 15, 20 and 25 and they can be placed only at the construction site where they were mixed and
• the second categories of concrete (B.II) with concrete class MB 30 or more, as well as concretes with special properties and transported concrete of all concrete classes. Concretes over 60 MB are special concretes, which can be used only for specific purposes. Composition of concrete of category B.II is determined on the basis of preliminary tests of fresh and hardened concrete, made of the determined constituents for the intended construction conditions and purpose of structure.

Specification for concretes of first and second category is determined by Articles 26 - 62 of the above mentioned Rulebook.

Classification according to the bulk density of concrete

Concrete can be classified according to the bulk density, as follows:

• Lightweight concretes, whose bulk density does not exceed 1900 kg/m3. This type of concrete prepares with light porous filling, with total or partial use of quartz sand as fine filling, with a hydraulic binder and water and admixtures in the particular circumstances. The increase of bulk density up to 2,100 kg/m3 is acceptable only when it comes to improvement of mechanical characteristics.

Technical norms that must be fulfilled during designing, construction and maintaining of blocks and structures of concrete and reinforced concrete, prepared with light aggregate filling, are determined by the Rulebook on technical norms for concrete and reinforced concrete prepared with natural and artificial lightweight aggregate filler ("Off. Gazette of the SFRY", No. 15/90) (download Rulebook).

• Classic (ordinary) concrete with bulk density from 1900 kg/m3 to 2500 kg/m3 and
• Heavy-weight concrete with bulk density of higher than 2500 kg/m3. High bulk density of concrete is achieved by using heavy-weight aggregates, such as barite, iron ore (magnetite, hematite and limonite), splinters or specially made balls of iron and steel. In order to improve protective characteristics of heavy-weight concrete, compounds of Boron or Lithium are added to concrete. Compressive strengths of heavy-weight concrete are not high and they don't exceed 40 MPa, and the tensile strength ranges from 1 to 3 MPa.

The provisions of the Rulebook on technical norms for concrete and reinforced concrete ("Official Gazette SFRY", No. 11/87 ) also apply to special types of concrete and structures, for hydro-technical structures, for concrete pavement structure, and similar, unless it is  indicated otherwise.

Classification of concrete according to the type of binder

Depending on the type of binder used for preparing concrete there are:

• Cement-concretes,
• Asphalt-concretes and
• Polymer concretes.

Unlike conventional cement - concretes, where different types and classes of Portland cement can be used as binder, in the asphalt - concretes bitumen, which is obtained by processing oil, is used as binder. Instead of aggregate that has rounded edges (gravel), for the production of asphalt it is used aggregate with sharp edges also called gravel (crushed stone). Asphalt - concrete is used for flexible (elastic) structures, mostly for asphalting streets and roads. Their purposes are completely different, although there are areas where they can overlap.

Polymer-concretes are type of concrete for whose preparation instead of cement polymers are used as binder. Concrete in which polymer is used as an admixture - concrete is called Polymer Cement Concrete - PCC or Polymer Modified Concrete - PMC.

Classification according to the consistency of concrete

According to the Rulebook on technical norms for concrete and reinforced concrete ("Official Gazette SFRY", No. 11/87), there are four types of concrete consistency: solid, low-plastic, plastic and liquid.

Consistency of fresh concrete is the set of all fresh concrete properties that affect its workability and processability. Concrete consistency can also be defined as the degree of stiffness or mobility of fresh concrete. Concrete consistency can be also defined as the degree of stiffness, i.e. agility of fresh concrete.

Classification according to concrete class

The concrete class (MB) is the normed compressive strength in MPa, based on the characteristic strength of concrete at the age of 28 days. The characteristic compressive strength is a value below which can be expected at most 10% of all compressive strengths of tested concrete (a 10 % fractile).

For the construction of concrete blocks the following concrete classes (MB) are used:  10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60.

It is not allowed to use concrete class lower than MB 15 for reinforced concrete.

Classification of concrete according to purpose

Depending on the intended use there are:

• Hydro-technical concretes
• Concretes for pavement structure
• Prestressed concretes
• Precast concretes
• Decorative (visible) concretes
• Concretes for radiation protection (heavy-weight concrete)
• The thermal insulating concretes (lightweight concretes)
• The waterproofing concretes
• The soundproofing concretes (lightweight concretes)
• Concretes for fire protection,
• Concrete and mortar for reparation, etc.

Overview of the concrete types classified according to the composition and characteristics can be found here.