Ageing mechanisms in building materials (physical ageing) involve damage mecha­nisms which cause material characteristics to deteriorate, and which can be caused by the exposures below:

— mechanical attacks, such as stresses imposed by temperatures

— physical attacks (frost, temperature changes and humidity)

— chemical attacks (acids, alkalis etc.)

— biological attacks (bacteria and fungi).

These effects set off ageing mechanisms which, for essential building materials, include:

— concrete: cracking, creep and shrinkage, swelling, secondary curing, carbonisation, damage due to chloride or sulphate attack, alkali reaction, solvent attacks, such as by acids and salts, swelling sulphate attacks, growths (e. g. algae), radiation

— reinforcement steel, pre-stressing steel, construction steel: corrosion

— pre-stressed concrete: loss of tension due to creep and shrinkage

— plastics: fatigue

— coatings: bubbling, cracking, chalking.

Ageing mechanisms can also be caused by changes to the subsoil, such as faults in building structures (cracks), operating problems (skewing turbine foundations etc.) due to the subsoil settlement under load, or deformations or changes of form in dykes through soil consolidation, sagging, settlements or external events.