12 types of concrete and concrete classes: overview

The types of concrete are as versatile as its use as a modern building material. Divided into classes, the right concrete is available for every application. We explain what types and classes there are.

types of concrete

Where concrete in its early days more than two thousand years ago was "only" a homogeneous substitute that was easy to produce on site for stone, today the building material convinces with its enormous specialization in the most varied of uses. Depending on the requirements, the composition and nature can vary greatly.

insulating concrete

Traditionally, concrete generates its enormous resilience through a high density of around 2.0 to 2.5 kg/dm3. This is accompanied by extremely poor insulating properties. In order to make the use of additional insulating materials obsolete, insulating concrete also has acceptable insulating values.

• Task: Production of load-bearing components with an insulating effect
• Special feature: Additives such as natural pumice, expanded clay or foam glass as air-entraining agents
• Examples of use: Components or buildings with a concrete look with requirements for thermal insulation

fiber concrete

As an alternative to the well-known reinforcement steel fiber concrete different fibers are introduced to increase the resilience.

• Task: high load-bearing capacity with small component dimensions
• Special feature: Glass fibres, textile fibers or, rarely, metal fibers as a substitute for reinforcing steel
• Examples of use: slim components, such as facing shells, furniture or garden objects, etc.

Easily workable concrete (LVB)

With regard to the grain size and additives used, LVB is designed to be processed as uniformly as possible and without damage. It meets both technical and optical high requirements with a simple installation

• Task: Simple installation in narrow, complicated formwork with dense reinforcement without defects, gravel nests, etc.
• Special feature: Maximum grain size usually 8 to 16 millimeters, often with the addition of superplasticizers and setting retarders
• Examples of use: Exposed concrete components, slender columns or beams

Translucent concrete

True, there is no real "transparent" concrete. However, it is possible to make it translucent for special effects.

• Task: Transport of light through the concrete component as an effect or for basic brightness
• Special feature: layered glass fiber mats or bundles as light channels
• Examples of use: Art installations, public buildings, museum and sacred buildings

normal concrete

The most commonly used type of concrete is normal concrete. One always speaks of normal concrete when the basic mixture is not affected by aggregates, fixtures, etc. is modified to a special type of concrete.

• Task: Production of normal loadable concrete components without special requirements
• Special feature: Mass i.d. R between 2.0 and 2.5 kg/dm3, compressive strength 5.0 to 55.0 N//mm2, hardening to standard strength according to DIN after 28 days
• Examples of use: Walls, ceilings, foundations etc.

recycled concrete

Recycled concrete picks up on the trend towards more sustainability and, depending on the desired properties, replaces parts of the mineral aggregates with recycled construction waste. Aggregate properties such as grain size, grading curve, load capacity, etc. are retained and taken into account unchanged.

• Task: Reducing the consumption of finite resources
• Special feature: processed building rubble as a substitute for mineral additives (sand, gravel, grit)
• Examples of use: depending on the concrete class as types of concrete without recycled building materials

spun concrete

Spun concrete describes the production of axially symmetrical linear components such as posts, masts, tubes, etc. in rotating molds.

• Task: Highly compacted, thin-walled components with high resilience through the use of centrifugal force
• Special feature: heavily layered structure due to ingredients of different weights in the centrifuge
• Examples of use: Power poles, concrete pipes etc.

Self Compacting Concrete (SCC)

Poor compaction often leads to optical and technical defects in the concrete component due to difficult access to the formwork or extremely dense reinforcement. Self-compacting concrete, on the other hand, does not require mechanical compaction by shaking or tamping.

• Task: Avoidance of defects, gravel nests, etc. in tight formwork
• Special feature: high level of uniformity without mechanical compaction methods thanks to the strong addition of superplasticizers and setting retarders
• Examples of use: Exposed concrete components, filigree components such as columns and beams, bridges, etc.

exposed concrete

For some time now, many designers have deliberately used concrete as a visible surface. A surface without air bubbles or gravel nests is important for a high-quality look.

• Task: high quality optical surface
• Special feature: Heavy use of flow agents, sometimes colored additives to change the look
• Examples of use: Buildings with an exposed concrete look, engineering structures such as bridges, retaining walls, underpasses, etc.

prestressed concrete

The load-bearing capacity of normal reinforced concrete can be further increased if the entire component is tensioned from the start in the opposite direction to the subsequent load. One then speaks of so-called prestressed concrete

• Task: Increase in resilience
• Special feature: Installation of tensioning wires, tensioning cables or tensioning rods, which are technically tensioned after the concrete has hardened (mainly by screwing)
• Examples of use: Industrial buildings, traffic structures (bridges!)

stamped concrete

Without reinforcement and compacted only by mechanical shocks, stamped concrete is the oldest type of concrete. It is often found in existing buildings in particular, for example on foundations or massive bridge piers.

• Task: Absorption of pressure loads, often in foundation components
• Special feature: no reinforcement, layered installation and compaction by tamping
• Examples of use: formerly for all concrete components, today still occasionally in horticulture as foundations and for other subordinate components

concrete classes

In order to find exactly the desired or To obtain the concrete required for a task, there are a number of different classifications today. Each classification considers a different property. As a result, today's technical designations for a specific concrete can include a whole range of different specifications. Typical is the classification according to:

compressive strength class

The decisive factor for the load-bearing capacity of concrete is the pressure it can withstand when it has set. Typical designations are a "C" for "Concrete" and two numbers separated by a slash. The first (smaller) number indicates the load in N/mm2 for a cylindrical specimen, the second number for a cube-shaped specimen. Common compressive strength classes are:

• C8/10 (eg. B. with lean concrete for minor soil improvements, in horticulture, etc.)
• C12/15
• C16/20
• C20/25
• C25/30 (common for many types of normal concrete, e.g. B. in classic house construction)
• C30/37 (from this class usually can only be produced with special technical equipment)
• C35/45
• C40/50
• C50/60
• C55/67
  etc.
• C90/105 (from here on no more general approval available, therefore approval required in each individual case, production technically only possible as spun concrete)
• C100/115

exposure class

Depending on how much a concrete component is exposed to environmental influences, it must be able to offer long-term resistance to these influences. For this purpose, concrete is divided into different exposure classes:

• X0: Unreinforced concrete and foundations without frost, no risk of attack for concrete and / or reinforcement
• XC (1-4): Interior or foundation components with high humidity (swimming pool, stables, laundries, etc.), open structures
• XD (1-4): Components in the spray mist area of ​​traffic areas, roadways, brine baths
• XS (1-3): External components near the coast, as well as port facilities, quay walls, etc.
• XF (1-4): Traffic areas treated with de-icing agents, seawater components, scraper runways
• XA (1-3): Components exposed to chemical attack, such as tanks in sewage treatment plants, liquid manure tanks, silage silos
• XM (1-3): Wear stress, e.g. E.g.: for industrial floors

In addition, four quality classes W0, FW, FA and WS designate the concrete quality for components exposed to moisture.

consistency class

Depending on the application, concrete with certain flow or stability properties may be necessary:

• C0: Very stiff, not DIN EN206
• F1: stiff
• F2: plastic
• F3: soft
• F4: very soft
• F5: flowable
• F6: very flowable
• F6*: SCC (self-compacting)

aggregate

Depending on the requirements, differently sized aggregates can be used for the concrete. A distinction is made between sand concrete, gravel concrete and crushed concrete. The grain size used is specified with the maximum diameter (Dmax).

bulk density

Depending on the density of the concrete, it is divided into three categories.

• lightweight concrete
• normal concrete
• heavy concrete

Each of these categories is further divided into raw density classes by DDIN EN206, from which the raw density results. For lightweight concrete, for example, there are 6 bulk density classes D1.0 to D2.0, with D2.0 meaning a bulk density of between 1,800 and 2,000 kilograms per cubic meter of concrete. The bulk density of a concrete is important for the self-weight of a component, but also, for example, for the definition of a surcharge by a concrete component.

Typical designations

A specific concrete mixture does not always have to be classified in all available classes. Sometimes it is also sufficient to determine, for example, the load and the exposure class, while density and grain size are irrelevant for the intended use. A typical concrete for foundation components, such as foundations, floor slabs, etc. is therefore about:

C25/30 XC1

This is a typical normal concrete with a medium load capacity and a low Resistance to moisture, such as that found in normal components in contact with the ground without oppressive groundwater etc can be used.

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