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Exposure class to BS 8500
The exposure classification in EN 206 is based upon deterioration process. Reinforcement corrosion due to carbonation (XC), Reinforcement corrosion due to chlorides (XD/S), Freeze-thaw action (XF) and Chemical (sulfate) attack (XA). The UK uses complimentary Standard BS 8500 and these classes all apply with the exception of sulfate attack which uses the DC classification originating from BRE Special Digest 1.
Other factors to consider are the intended working life of at least 50 years (Table A.4) or 100 years (Table A.5), cement type, strength class (28-day), cement content, water/cement ratio and cover to reinforcement. The current version of BS 8500:2023 provides the following classifications:
X0 – No risk of corrosion or attack
XC1 to 4 – Corrosion induced by carbonation*
XD1 to 3 – Corrosion induced by chlorides other than from sea water**
XS1 to 3 – Corrosion induced by chlorides from sea water**
XF1 to 4 – Freeze/thaw action
DC-1 to 4 – Sulfate attack
* No limit on w/c ratio.
** No limit on strength class.
