Some ageing characteristics of lime

This study involves the special case of lime compacts which are considered to serve as models for the system of lime in hydrated Portland cement paste. The ageing of lime was studied by measuring length changes of powdered samples under various steady‐state and alternating conditions of humidity. As an explanation for the unique behaviour of lime compacts, a primary mechanism is proposed based on the theory that recrystallisation occurs at least at areas of particle contact when lime compacts are exposed to humidities above a certain value. Furthermore, this recrystallised product is more accommodating than the parent material, and hence it can be consolidated by forces due to menisci or changes in surface free‐energy. This action is manifested by irreversible shrinkage on storage at intermediate humidities, by drying after storage or by alternating between two levels of humidity.