8.10 : Curing of Concrete

The hydration of cement takes place within the water-filled capillary pores. However, environmental elements can disrupt this process by evaporating water from the concrete surfaces. Sealed concrete with a water-cement ratio below 0.5 experiences self-desiccation, leading to water loss. The water loss in concrete is mitigated by curing. This technique involves keeping the concrete saturated to maintain the necessary temperature and moisture conditions, to optimally fill the spaces in the cement paste initially occupied by water with hydration products. Curing starts after the cement has attained the final set. Concrete left to dry without curing may shrink and crack and will likely only reach half the strength of concrete that is continuously cured over 28 days. The duration of curing correlates directly with the concrete's final compressive and tensile strength, underlining the importance of this practice not only for strength but also for ensuring other desirable properties like durability, water tightness, resistance to abrasion, and freeze-thaw. This effect is more prominent in thinner structural elements and mixes with a high cement content, whereas lightweight aggregate concrete is less affected. Moreover, air-entrained concrete is less influenced by curing conditions than non-air-entrained concrete.