Exposure class

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The exposure class is a term used in concrete construction .

In order to ensure sufficient durability , concrete components must be sufficiently resistant to chemical and physical influences from their environment and use. The effects from the various environmental conditions are classified in exposure classes that can affect the concrete , reinforcing steel or metallic components and which are not considered as loads in the structural design. This results in the requirements for the composition of the concrete to be used, as well as the concrete cover and the permissible crack width.

Exposure classes according to Eurocode, DIN and ÖNORM

The designations of the individual exposure classes are made up of the letter X (for E x position), the identifier for the type of damaging effect and a number that indicates the intensity of the damaging effects. The following English abbreviations are used for the different types of actions:

  • 0 for zero risk (no risk of attack)
  • C for C arbonation ( carbonation )
  • D for D eicing Salt (changeable chlorides , e.g. from road salt)
  • S for S eawater (sea water)
  • F for F rust (frost and de-icing)
  • A for Chemical A ttack (chemical attack)
  • M for M echanical Abrasion (mechanical attack (abrasion, wear and tear, etc.))

In Germany, the exposure classes are regulated in DIN EN 1992-1-1 (" Eurocode 2") with the national annex DIN EN 1992-1-1 / NA. In addition, DIN EN 206-1 with the amendments A1 and A2 and DIN 1045–2 with the application rules for DIN EN 206-1 must be taken into account.

In the last version of DIN 1045-1 (2008-08), which has since been withdrawn, the exposure classes were expanded to include exposure W "Concrete corrosion due to alkali-silica reaction ". No minimum concrete strength classes are assigned to this exposure. In Austria these exposure classes are named identically, but have different examples in the assignment.

Table of exposure classes (environmental classes)

Exposure classes according to Eurocode 2 (EN 1992)
Exposure class Environmental condition Examples for the assignment (informative) according to the national annex DIN EN 1992–1-1 / NA [2011–01]
No risk of corrosion or attack
X0 No risk of corrosion or attack unreinforced foundations without frost, unreinforced internal components
XC: Reinforcement corrosion caused by carbonation
XC1 Dry or constantly wet Components in interiors with normal humidity (kitchen, bathroom in residential buildings, etc.)
XC2 Wet, rarely dry Parts of water tanks, foundation components
XC3 Moderate humidity Components with frequent or constant contact with the outside air (open halls), interiors with high humidity (commercial kitchens, bathrooms, laundries), in damp rooms in indoor pools and cattle stalls
XC4 Alternating wet and dry External components with direct irrigation, components in water change zones
XD: Reinforcement corrosion caused by chlorides , excluding sea water
XD1 Moderate humidity Components in the spray mist area of ​​traffic areas
XD2 Wet, rarely dry Swimming pools, components that are exposed to industrial wastewater containing chloride
XD3 Alternating wet and dry Parts of bridges, road surfaces, parking decks
XS: Reinforcement corrosion caused by chlorides from seawater
XS1 Salty air, no direct contact with sea water External components near the coast
XS2 Under water Components in docks that are constantly under water
XS3 Tidal areas, splash water and spray areas Quay walls in port facilities
XF: Concrete attack by frost with and without de-icing agent
XF1 Moderate water saturation without de-icing agent Exterior components
XF2 Moderate water saturation with de-icing agent or sea water Concrete components in the spray mist area of ​​traffic areas treated with de-icing agent, concrete components in the spray mist from seawater
XF3 High water saturation without thawing agents open water tanks, components in the water transition zone of fresh water
XF4 High water saturation with de-icing agent or sea water Road surfaces that are treated with de-icing agents, components in the splash water area of ​​traffic areas treated with de-icing agents, scraper tracks in sewage treatment plants, seawater components in the water transition zone
XA: Concrete attack by chemical attack from the environment
XA1 Chemically weakly aggressive environment Wastewater treatment plant tanks, slurry tanks
XA2 Chemically moderately aggressive environment and marine structures Concrete components that come into contact with seawater, components in soils that are strongly attacked by concrete
XA3 Chemically aggressive environment Industrial wastewater systems with chemically very aggressive wastewater
Additional exposure classes according to the German national annex to Eurocode 2 (DIN EN 1992–1-1 / NA: 2011–01)
W: Concrete corrosion due to alkali-silica reaction
WHERE Concrete which, after drying out, remains largely dry during use

(dry)

Interior components of a building construction

Components that affect the outside air but no precipitation, surface water, soil moisture and / or which are not constantly subject to a rel. Humidity> 80%

WF Concrete that is wet frequently or for a long period of time

(wet)

Unprotected external components exposed to precipitation, surface water and soil moisture

Internal components of building construction for damp rooms with a predominantly higher relative humidity than 80%, (e.g. indoor swimming pools, laundries, other commercial damp rooms) Components with frequent drops below the dew point (e.g. chimneys, heat transfer stations, filter chambers and cattle sheds)
Massive components according to DAfStb - Guideline with smallest dimensions> 0.80 m (regardless of the ingress of moisture)

WA Concrete that is frequently or for a longer period of time damp and is also exposed to frequent or long-term external alkali

(moist + external alkali supply)

Components exposed to seawater

Components exposed to de-icing salt without additional high dynamic stress (e.g. splash water areas, driving and parking areas in multi-storey car parks), components of industrial buildings and agricultural structures (e.g. liquid manure tanks) exposed to alkali salt

WS Class WA concrete with additional high dynamic stress

(damp + external alkali supply + strong dynamic stress)

Components exposed to de-icing salt with additional high dynamic stress (e.g. concrete roadways)
Additional exposure classes according to DIN 1045–2: 2008–08
XM: Concrete attack through wear and tear
XM1 Moderate wear and tear Road surfaces in residential areas
XM2 Heavy wear and tear Road surfaces on main roads, traffic areas with heavy forklift traffic
XM3 Extreme wear and tear Coverings of areas that are often driven over by tracked vehicles (barracks courtyard), hydraulic structures in bodies of debris (upper reaches of rivers, stilling basins )


In the DVGW worksheet W 300 published in October 2014, a separate exposure class X TWB is defined for use in drinking water tanks.

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