Resumen
In the making a good quality concrete, curing represents one of the most important factors to be considered. Curing allows the cementitious materials tohydrate and the concrete to reach the specified strength. Moreover, it reduces the variability in the mechanical properties and decreases permeability. Sincethe development of low water-to-cementitious materials ratio (W/CM) concretes, several properties of concrete have been greatly improved. Nevertheless,the need of curing has become even more important. A low W/CM concrete has low water content and relatively high amount of cementitious materialswhich increases de need for curing. However, this kind of concrete has low permeability which makes difficult the ingress of curing water. A new paradigmhas emerged for solving the curing needs of low W/CM concretes. This paradigm is called internal curing, and it consists of storing water within the concretethat is not available during the mixing nor during the first stages of hydration but it is released for curing later on. This paper presents the different typesand methods of internal curing currently available, the working principles and some experimental results that demonstrate its effectiveness.