Ageing refers to:

a) a process where the physical properties, for example the rheology, of wet clay are improved by allowing the clay to sit undisturbed for a period, sometimes for years but more often for days or months, to allow the water to become more homogeneously distributed or to promote the growth of microorganisms. An improvement in plasticity by ageing is important for pressing and drawing of the clay for commercial production of ceramics.
Syn., aging, maturation;

b) in soil mechanics, aging is also referred to the process of secondary consolidation or drained creep.
Cf., drained creep, secondary compression