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X0 - No risk of carbonation

• Concrete inside buildings with very low air humidity

XC1 - Dry or permanently wet

• Concrete inside buildings with low air humidity, concrete permanently submerged in water

XC2 - Wet, rarely dry

• Concrete surfaces subject to long-term water contact. Examples: most of foundations

XC3 - Moderate humidity

• Concrete inside buildings with moderate or high air humidity, external concrete sheltered from rain

XC4 - Cyclic wet and dry

• Concrete surfaces subject to water contact, not within exposure class XC2. Examples: cantilever walls, external structures

X0 - No risk

• No risk of corrosion induced by chlorides

XD1 - Moderate humidity

• Concrete surfaces exposed to airborne chlorides

XD2 - Wet, rarely dry

• Swimming pools, concrete components exposed to industrial waters containing chlorides

XD3 - Cyclic wet and dry

• Parts of bridges exposed to spray containing chlorides, pavements, car park slabs

X0 - No risk

• No risk of corrosion induced by chlorides from sea water

XS1 - Exposed to airborne salt but not in direct contact with sea water

• Structures near to or on the coast

XS2 - Permanently submerged

• Parts of marine structures

XS3 - Tidal, splash and spray zones

• Parts of marine structures

X0 - No risk

• Concrete inside buildings not exposed to rain and freezing

XF1 - Moderate water saturation, without de-icing agent

• Vertical concrete surfaces exposed to rain and freezing

XF2 - Moderate water saturation, with de-icing agent

• Vertical concrete surfaces of road structures exposed to freezing and airborne de-icing agents

XF3 - High water saturation, without de-icing agents

• Horizontal concrete surfaces exposed to rain and freezing

XF4 - High water saturation with de-icing agents or sea water

• Road and bridge decks exposed to de-icing agents, concrete surfaces exposed to direct spraycontaining de-icing agents and freezing, splash zone of marine structures exposed to freezing

X0 - No risk

• Concrete not exposed to aggressive chemical environment

XA1 - Slightly aggressive chemical environment according to EN 206-1, Table 2

• Natural soils and ground water

XA2 - Moderately aggressive chemical environment according to EN 206-1, Table 2

• Natural soils and ground water

XA3 - Highly aggressive chemical environment according to EN 206-1, Table 2

• Natural soils and ground water