Methods of curing:
A. Water curing
B. Membrane curing
C. Application of heat
D. Miscellaneous methods
1. Water curing: i) This is the best method of curing, because it satisfies all the requirements of curing. ii) The precast concrete items are normally immersed in curing tanks for certain duration. Pavement slab, roof slab etc. are covered under water by making small pond. iii) Water curing can be done in following ways: Immersion, Ponding method, Spraying or fogging, wet covering.
2. Membrane curing: i) Sometimes concrete works are carried out in places where there is acute shortage of water. Therefore lavish application of water for water curing is not possible for the reason of economy. ii) Water from concrete gets evaporated, which is covered with membrane which will effectively seal the concrete. iii) A membrane will prevent the evaporation of water from the concrete. The membrane can be either in solid or liquid form, known as sealing compound. Other membrane curing sealing compounds are: Rubber latex emulsion, emulsion of resins, varnishes etc.
3. Application of heat: i) The development of strength is not only a function of time but also that of temperature. ii) Concrete subjected to higher temperature accelerates the hydration resulting in faster development of strength. Prefabricated members are normally steam cured. iii) In this method the ingredients of concrete heated and the strength is gained at very fast rate. This can be done in following manner: Steam curing, Curing by infra-red radiation, Electrical curing
4. Miscellaneous method: i) Calcium chloride is used either as a surface coating or as an admixture. It has been satisfactorily used as a curing medium. ii) Both of these based on the fact that calcium chloride, being a salt shows affinity for moisture. The salt not only absorbs moisture from atmosphere but also retains it at the surface. iii) The moisture held at the surface prevents the mixed water from evaporation and thereby keeps the concrete wet for a long time.